Mereo BioPharma (MREO) 20-F 28 Mar 23 2022 FY Annual report (foreign) Financial data

Cover Page

Cover Page - shares	12 Months Ended	84 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Document Information [Line Items]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Registrant Name	MEREO BIOPHARMA GROUP PLC
Entity Central Index Key	0001719714
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding	624,928,519
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity File Number	001-38452
Entity Incorporation, State or Country Code	X0
Entity Address, Address Line One	One Cavendish Place
Entity Address, Address Line Two	4th Floor
Entity Address, City or Town	London
Entity Address, Country	GB
Entity Address, Postal Zip Code	W1G 0QF
Document Annual Report	true
Document Transition Report	false
Document Shell Company Report	false
Document Accounting Standard	International Financial Reporting Standards
Document Registration Statement	false
ICFR Auditor Attestation Flag	false
Auditor Name	BDO LLP	Ernst & Young LLP
Auditor Firm ID	1295	1438
Auditor Location	London	London
Business Contact [Member]
Document Information [Line Items]
Contact Personnel Name	Charles Sermon
Contact Personnel Email Address	cs@mereobiopharma.com
Entity Address, Address Line One	1 Cavendish Place
Entity Address, Address Line Two	4th Floor
Entity Address, City or Town	London
Entity Address, Country	GB
Entity Address, Postal Zip Code	W1G 0QF
City Area Code	44
Local Phone Number	333-023-7300
ADR [Member]
Document Information [Line Items]
Trading Symbol	MREO
Title of 12(b) Security	American Depositary Shares, each representingfive ordinary shares, nominal value of £0.003per share
Security Exchange Name	NASDAQ
Ordinary shares [member]
Document Information [Line Items]
No Trading Symbol Flag	true
Title of 12(b) Security	Ordinary Shares, nominal value of £0.003 pershare
Security Exchange Name	NASDAQ

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss)/Income - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of comprehensive income [abstract]
Revenue		£ 36,464
Cost of revenue	£ 936	(17,908)
Research and development expenses	(24,962)	(23,559)	£ (16,347)
Administrative expenses	(19,543)	(15,933)	(21,222)
Operating loss	(43,569)	(20,936)	(37,569)
Finance income	696	1	44
Finance costs	(3,361)	(4,022)	(6,383)
Changes in the fair value of financial instruments	7,805	40,039	(109,849)
Gain/(loss) on disposal of intangible assets		113	(10,872)
Net foreign exchange gain/(loss)	1,525	(954)	(1,821)
Other income and expenses	811
(Loss)/profit before tax	(36,093)	14,241	(166,450)
Taxation	1,897	(1,516)	2,822
(Loss)/profit for the year, attributable to equity holders of the parent	(34,196)	12,725	(163,628)
Currency translation of foreign operations	(1,828)	(191)	349
Total comprehensive (loss)/income for the year, attributable to equity holders of the parent	£ (36,024)	£ 12,534	£ (163,279)
Basic (loss)/profit per share for the year (in £)	£ (0.06)	£ 0.02	£ (0.48)
Diluted loss per share for the year (in £)	£ (0.06)	£ (0.05)	£ (0.48)

Consolidated Balance Sheets

Consolidated Balance Sheets - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Non-current assets
Property, plant and equipment	£ 1,831	£ 2,530
Intangible assets	24,116	24,564
Total non-current assets	25,947	27,094
Current assets
Prepayments	3,125	2,799
R&D tax credits	1,296
Other taxes receivable	614	809
Other receivables	762	1,419
Cash and short-term deposits	56,334	94,296
Total current assets	62,131	99,323
Total assets	88,078	126,417
Non-current liabilities
Provisions		1,320
Convertible loan notes	0	14,384
Warrant liability	129	8,336
Lease liability	1,222	1,754
Other liabilities	182	80
Total non-current liabilities	1,533	25,874
Current liabilities
Trade and other payables	3,078	2,499
Accruals	4,491	3,826
Current tax liabilities		1,522
Provisions	4,822	2,803
Convertible loan notes	11,085	0
Warrant liability	402
Lease liability	466	622
Other liabilities	333	1,269
Total current liabilities	24,677	12,541
Total liabilities	26,210	38,415
Net assets	61,868	88,002
Equity
Issued capital	1,875	1,755
Share premium	254,303	247,460
Other capital reserves	132,680	129,835
Employee Benefit Trust shares	(1,058)	(1,140)
Other reserves	7,401	7,401
Accumulated losses	(331,164)	(296,968)
Translation reserve	(2,169)	(341)
Total equity	£ 61,868	£ 88,002

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities
(Loss)/profit before tax	£ (36,093)	£ 14,241	£ (166,450)
Adjustments to reconcile (loss)/profit before tax to net cash flows:
Depreciation of property, plant and equipment	727	642	1,599
Share-based payments expense	3,862	3,302	1,558
Net foreign exchange (gain)/loss	(2,064)	954	1,821
Increase in provisions and other liabilities	211	1,385	162
Finance income	(696)	(1)	(44)
Finance costs	2,910	3,797	6,226
Other non-cash movements	647	156
Gain on lease modification			(957)
Fair value remeasurement on warrants	(7,805)	(40,039)	109,849
Other income and expenses	(811)
(Gain)/loss on disposal of intangible assets		(113)	10,872
Out-license of intangible asset		9,457
Working capital adjustments
Decrease/(increase) in receivables and prepayments	695	(589)	141
Increase/(decrease) in trade and other payables and accruals	1,126	(1,256)	(3,551)
Taxation	(1,529)	2,825	10,433
Net cash flows used in operating activities	(38,820)	(5,239)	(28,341)
Investing activities
Acquisition of subsidiary			(354)
Purchase of property, plant and equipment	(10)	(535)	(16)
Proceeds from intangible assets (net of transaction costs)	1,484	113	1,821
Interest earned	696	1	44
Payments to CVR holders	(673)
Net cash flows (used in)/from investing activities	1,497	(421)	1,495
Financing activities
Proceeds from issuance of ordinary shares		78,532	20,136
Transaction costs on issuance of shares		(234)	(1,307)
Proceeds from exercise of employee share options		46
Proceeds from issuance of convertible loan notes			44,375
Transaction costs on issuance of convertible loan notes			(3,598)
Repayment of bank loans			(19,802)
Transaction costs relates to loans and borrowings			(81)
Interest paid on bank loan			(2,900)
[Proceeds from TAP agreement]	153
Payment of lease liabilities	(937)	(692)	(2,086)
Net cash flows (used in)/from financing activities	(784)	77,652	34,737
Net (decrease)/increase in cash and cash equivalents	(38,107)	71,992	7,891
Cash and cash equivalents at January 1	94,296	23,469	16,347
Effect of exchange rate changes	145	(1,165)	(769)
Cash and cash equivalents at December 31	£ 56,334	£ 94,296	£ 23,469

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - GBP (£) £ in Thousands	Total	Issued capital [member]	Share premium [member]	Other capital reserves [member]	Employee benefit trust [member]	Other reserves [member]	Accumulated losses [member]	Translated reserve
Beginning balance at Dec. 31, 2019	£ 40,256	£ 294	£ 121,684	£ 59,147	£ (1,305)	£ 7,000	£ (146,065)	£ (499)
Loss for the year	(163,628)						(163,628)
Other comprehensive income	349							349
Total comprehensive (loss)/income for the year, attributable to equity holders of the parent	(163,279)						(163,628)	349
Share-based payments	1,558			1,558
Issuance of share capital, net	16,937	347	18,715			(2,125)
Conversion of loan notes and warrants	55,949	375	21,386	34,188
Reclassification of loan notes embedded derivative	33,481			33,481
Conversion of warrants	127	1				126
Ending balance at Dec. 31, 2020	(14,971)	1,017	161,785	128,374	(1,305)	5,001	(309,693)	(150)
Loss for the year	12,725						12,725
Other comprehensive income	(191)							(191)
Total comprehensive (loss)/income for the year, attributable to equity holders of the parent	12,534						12,725	(191)
Share-based payments	3,302			3,302
Issuance of share capital, net	79,210	601	78,609
Exercise of share options	46			(119)	165
Conversion of loan notes and warrants	7,881	137	7,066	(1,722)		2,400
Ending balance at Dec. 31, 2021	88,002	1,755	247,460	129,835	(1,140)	7,401	(296,968)	(341)
Loss for the year	(34,196)						(34,196)
Other comprehensive income	(1,828)							(1,828)
Total comprehensive (loss)/income for the year, attributable to equity holders of the parent	(36,024)						(34,196)	(1,828)
Share-based payments	3,862			3,862
Exercise of share options				(82)	82
Conversion of loan notes and warrants	5,958	120	6,843	(1,005)
Issuance of warrants	70			70
Ending balance at Dec. 31, 2022	£ 61,868	£ 1,875	£ 254,303	£ 132,680	£ (1,058)	£ 7,401	£ (331,164)	£ (2,169)

Corporate information

Corporate information	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Corporate information	1. Corporate information Mereo BioPharma Group plc (the “Company” or “Mereo”) is a clinical-stage, United Kingdom (“UK”) based biopharmaceutical company focused on rare diseases. The Company is a public limited company incorporated and domiciled in the UK, and registered in England, with shares publicly traded on the Nasdaq Global Market via American Depositary Shares (“ADSs”) under the ticker symbol “MREO”. The Company’s ordinary shares were previously admitted to trading on the AIM market of London Stock Exchange plc with admission cancelled with effect on December 18, 2020. The Company’s registered office is located at Fourth Floor, 1 Cavendish Place, London, W1G 0QF, United Kingdom. The consolidated financial statements of Mereo BioPharma Group plc and its subsidiaries for the year ended December 31, 2022 were authorized for issue in accordance with a resolution of the Directors on March 28

Significant accounting policies

Significant accounting policies	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Significant accounting policies	2. Significant accounting policies Basis of preparation The Company’s consolidated financial statements have been prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board (IASB). The consolidated financial statements are presented in pound sterling (“£”), which is the presentational currency of the Company. The functional currencies of consolidated subsidiaries are pound sterling and US dollars (“$”). All amounts disclosed in the consolidated financial statements and notes have been rounded to the nearest thousand, unless otherwise stated. The financial statements have been prepared on the historical cost basis, except for the revaluation of certain financial instruments that are measured at fair values at the end of each reporting period, as explained in the accounting policies below. Basis of consolidation The consolidated financial information comprises the financial statements of Mereo BioPharma Group plc and its subsidiaries as at December 31, 2022. Subsidiaries are all entities over which the Company has control. The Company controls an entity when the Company is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power over the entity. Subsidiaries are fully consolidated from the date on which control is transferred to the Company. They are deconsolidated from the date that control ceases. Intercompany transactions, balances and unrealized gains on transactions between subsidiaries are eliminated in preparing the consolidated financial statements. Accounting policies of subsidiaries are consistent with the policies adopted by the Company. The Company has an employee share trust to facilitate share transactions pursuant to employee share schemes. Although the trust is a separate legal entity from the Company, it is consolidated into the Company’s results in accordance with the IFRS 10 rules on special purpose vehicles. The Company is deemed to control the trust principally because the trust cannot operate without the funding the Company provides. Segmental information The Company has one operating segment. The Chief Operating Decision Maker (“CODM”) is the Chief Executive Officer. The Company has a single portfolio of product candidates, with only direct research and development expenses monitored at a product candidate level. The CODM makes decisions over resource allocation at an overall portfolio level and the Company’s financing is managed and monitored on a consolidated basis. Non-current assets held by the Company are located in the United Kingdom and United States. As at December 31, 2022, less than Going concern The going concern basis has been applied in these consolidated financial statements as the Company has adequate resources to meet its liabilities as they fall due for the foreseeable future and at least 12 months from the issuance date of these consolidated financial statements. The Company expects to incur significant operating losses for the foreseeable future as it continues its research and development efforts, seeks to obtain regulatory approval of its product candidates and pursues any future product candidates the Company may develop. Until such time as the Company can generate significant revenue from product sales, or other commercial revenues, if ever, or through licensing and/or collaboration agreements for its rare disease or oncology product candidates, the Company will seek to finance its operations through a combination of public or private equity or debt financings or other non-dilutive Summary of significant accounting policies a) Revenue The Company’s ordinary business activities are the development of product candidates to key clinical milestones and either strategically partnering them or further developing such product candidates through regulatory approval and potentially commercialization. The Company may enter into a range of different agreements with third parties, including but not limited to: (i) licensing agreements where the global rights to a product candidate are licensed to a partner; and (ii) collaboration agreements where rights to a product candidate are licensed to a partner but the Company retains certain rights, for example to further develop or commercialize the product candidate in specified geographical territories. Under both licensing and collaboration agreements, rights to product candidates are provided to a partner typically in exchange for consideration in the form of upfront payments and/or development, regulatory, commercial or other similar milestones, and royalties on commercial sales, should regulatory approval be obtained for the product candidates. Where the Company has performed significant development activities for its product candidates, income from agreements with third parties are considered to be proceeds derived from the Company’s ordinary activities and therefore represent revenue within the scope of IFRS 15, Revenue from Contracts with Customers. Revenue includes income from licensing and collaboration agreements. Consideration received up front is recognized at the point in time in which the right to use an intangible asset is transferred and further payments received are recognized upon the achievement of specified development, regulatory, commercial or other similar milestones. For agreements with a right to access an intangible asset, revenue is recognized over time, typically on a straight-line basis over the life of the license or collaboration agreement. When there are other performance obligations in such agreements, the consideration is allocated using the residual approach and recognized when the performance obligations are satisfied. Income from development, regulatory, commercial or similar milestones is recognized when considered highly probable that a significant reversal will not occur. Timing of the recognition of such milestones are considered to be a key judgment, as they are often dependent on third parties. In general, for milestones which are subject to the decisions of third parties (e.g. the acceptance or approval of a filing by a regulatory authority), the Company recognizes milestone income when the decision occurs. The Company does not currently have any approved product candidates. Accordingly, no commercial sales revenue was generated during the year. Intangible assets out-licensed out-licensed. b) Research and development (R&D) expenses Expenditure on product development is capitalized as an intangible asset and amortized over the expected useful economic life of the product candidate concerned. Capitalization commences from the point at which technical feasibility and commercial viability of the product candidate can be demonstrated and the Company is satisfied that it is probable that future economic benefits will result from the product candidate once completed. Capitalization ceases when the product candidate receives regulatory approval for launch. No such costs have been capitalized to date. Expenditure on R&D activities that do not meet the criteria for capitalization, including ongoing costs associated with acquired intellectual property rights and intellectual property rights generated internally by the Company, is recognized in the consolidated statement of comprehensive (loss)/income as incurred. Intellectual property and in-process c) Taxation Tax expense recognized in the consolidated statement of comprehensive (loss)/income comprises the sum of deferred tax and current tax not recognized in other comprehensive income or directly in equity. Current income tax Current income tax assets and liabilities are measured at the amount expected to be recovered from or paid to the taxation authorities that are unpaid at the reporting date. Current tax is payable on taxable profit, which differs from profit or loss in the consolidated financial statements. Calculation of current tax is based on tax rates and tax laws that have been enacted, or substantively enacted, by the end of the reporting period in the jurisdictions in which the Company operates. Amounts receivable in respect of research and development tax credits are recognized in the consolidated financial statements provided there is sufficient evidence that the amounts are recoverable. These credits are recognized within income tax in the consolidated statement of comprehensive (loss)/income. A provision is recognized for matters in which the tax determination is uncertain but it is considered probable that there will be a future outflow of funds to a tax authority. The provisions are measured at the best estimate of the amount expected to become payable. Deferred tax Deferred tax is provided using the liability method on temporary differences between the tax bases of assets and liabilities and their carrying amounts for financial reporting purposes at the reporting date. Deferred income tax assets are recognized for all deductible temporary differences, carry-forward of unused tax credits and unused tax losses, to the extent that it is probable that taxable profit will be available against which the deductible temporary differences and the carry-forward of unused tax credits and unused tax losses can be utilized. The carrying amount of deferred income tax assets is reviewed at the end of each reporting period and reduced to the extent that it is no longer probable that sufficient taxable profit will be available to allow all or part of the deferred income tax asset to be utilized. Unrecognized deferred income tax assets are reassessed at the end of each reporting period and are recognized to the extent that it has become probable that future taxable profit will allow the deferred tax assets to be recovered. Deferred tax assets and liabilities are measured on an undiscounted basis at the tax rates that are expected to apply in the year when the asset or liability is realized, based on tax rates (and tax laws) enacted or substantively enacted at the end of the reporting period. Deferred tax assets and liabilities are offset when there is a legally enforceable right to set off current tax assets against current tax liabilities and when they relate to income taxes levied by the same taxation authority and the Company intends to settle its current tax assets and liabilities on a net basis. d) Foreign currencies Items included in the consolidated financial statements are measured using the currency of the primary economic environment in which the entity operates (“the functional currency”). The consolidated financial statements are presented in pound sterling (“£”), which is the presentational currency of the Company. The functional currencies of consolidated subsidiaries are pound sterling and US dollars (“$”). Transactions in foreign currencies are initially recorded by the Company at the rate prevailing on the date the transaction first qualifies for recognition. Differences arising on settlement or translation of monetary items as well as gains or losses on the re translation of foreign currency balances at the period-end are recognized in the consolidated statement of comprehensive (loss )/income. The results and financial position of subsidiaries that have a functional currency different from the presentational currency of the Company are translated into the presentational currency (pound sterling). The assets and liabilities of such entities are translated into pound sterling at the rate of exchange prevailing at the balance sheet date. Income and expenses are translated at the average rate for the period, which approximates the exchange rates at the dates of the transactions. Fair value adjustments arising on acquisition of such entities are treated as assets and liabilities of the relevant entity and translated into pound sterling at the closing rate. The exchange differences arising on translation for consolidation are recognized in other comprehensive (loss)/income. e) Property, plant and equipment Property, plant and equipment is stated at cost, net of accumulated depreciation and accumulated impairment losses, if any. Such cost includes the cost of replacing part of the plant and equipment if the recognition criteria are met. All other repair and maintenance costs are recognized in profit or loss as incurred. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Useful lives of various property, plant and equipment are as follows: • Leasehold improvements shorter of lease term or ten years • Office equipment five years • IT equipment three years Property, plant and equipment is derecognized upon disposal or when no future economic benefits are expected from its use or disposal. Any gain or loss arising on derecognition of the asset (calculated as the difference between the net disposal proceeds and the carrying amount of the asset) is included in the consolidated statement of comprehensive (loss)/income when the asset is derecognized. The residual values, useful lives and methods of depreciation of property, plant and equipment are reviewed annually and adjusted prospectively, if appropriate. f) Business combinations Business combinations are accounted for using the acquisition method of accounting. At the date of acquisition, the Company initially recognizes the fair value of the identifiable assets acquired, the liabilities assumed and any non-controlling The consideration transferred is measured at fair value at the date of acquisition. The excess of the consideration transferred over the fair value of net identifiable assets of the business acquired is recorded as goodwill, unless the amount of consideration transferred is less than the fair value of net identifiable assets of the business acquired in which case the difference is recognized directly in the consolidated statement of comprehensive (loss)/income as a bargain purchase. A valuation is performed of assets and liabilities assumed on each acquisition accounted for as a business combination based on the best estimate of fair value. Where the settlement of any part of cash consideration is deferred, the amounts payable in the future are discounted to their present value. Contingent consideration is classified either as equity or a financial liability and is recognized at fair value on the acquisition date. Amounts classified as a financial liability are subsequently remeasured to fair value in accordance with IFRS 9 (Financial Instruments), with changes in fair value recognized in the consolidated statement of comprehensive (loss)/income as an administrative expense. Directly attributable acquisition-related costs are expensed as incurred within the consolidated statement of comprehensive (loss)/income. g) Leases Effective January 1, 2019, the Company adopted IFRS 16 (Leases) using the modified retrospective approach. The Company assesses whether a contract is, or contains, a lease at inception of the contract. The Company recognizes a right-of-use The lease liability is initially measured at the present value of the lease payments that are not paid at the commencement date, discounted using the rate implicit in the lease. If this rate cannot be readily determined, the Company uses its incremental borrowing rate. Lease payments included in the measurement of the lease liability comprise of fixed lease payments, less any lease incentives receivable. The lease liability is subsequently measured by increasing the carrying amount to reflect interest on the lease liability (using the effective interest method) and by reducing the carrying amount to reflect the lease payments made. The Company remeasures the lease liability (and makes a corresponding adjustment to the related right-of-use The right-of-use The right-of-use Right-of-use • Right-of-use six • Right-of-use one When the Company is an intermediate lessor, it accounts for the head lease and the sub-lease sub-lease right-of-use h) Intangible assets Intangible assets are initially recorded at cost which has been determined as the fair value of the consideration paid and payable. Assets that have been acquired through a business combination are initially recorded at fair value. The fair value of consideration is regularly reviewed based on the probability of achieving contractual milestones. Refer to policy on provision for deferred cash consideration below. Where the consideration paid or payable is in shares, the cost is measured in accordance with IFRS 2 (Share Based Payments). Intangible assets that are not yet available for use are reviewed for impairment at each reporting date by allocating the assets to the cash-generating units to which they relate. The estimated useful life is the lower of the legal duration and economic useful life. The estimated useful lives of intangible assets are reviewed at least annually. Intangible assets are amortized from the date they are available for commercial use. No amortization has been recognized to date. An intangible asset is derecognized on disposal, or when no future economic benefits are expected from use or disposal. Gains or losses arising from derecognition of an intangible asset, measured as the difference between the net disposal proceeds and the carrying amount of the asset, are recognized in profit or loss when the asset is derecognized. i) Financial instruments Financial assets and liabilities are recognized in the consolidated balance sheet only when the Company becomes party to the contractual provisions of the instrument. Financial assets On initial recognition, a financial asset is classified into one of three primary measurement categories: • Amortized cost; • Fair value through other comprehensive income (“FVOCI”); or • Fair value through profit or loss (“FVTPL”). The initial classification into a primary measurement category depends on the nature and purpose of the financial asset. For short-term investments, interest income and impairment gains or losses are recognized directly in the consolidated statement of comprehensive income. The difference between cumulative fair value gains or losses and the cumulative amounts recognized in the consolidated statement of comprehensive (loss)/income is recognized in other comprehensive income until derecognition, when the amounts in other comprehensive income are reclassified to the consolidated statement of comprehensive (loss)/income. Classification as debt or equity Debt and equity instruments are classified as either financial liabilities or as equity in accordance with the substance of the contractual arrangements and the definitions of a financial liability and an equity instrument. Embedded derivatives An embedded derivative is a component of a hybrid contract that also includes a non-derivative Convertible loan notes Convertible loan notes are regarded as compound instruments consisting of a liability component and an equity component. At the date of issue, the fair value of the liability component is estimated using a discount rate for an equivalent liability without the conversion feature. This amount is recorded as a liability on an amortized cost basis using the effective interest method until extinguished upon conversion or at the instrument’s maturity date. The difference between the proceeds from the issue of the convertible loan note and the fair value assigned to the liability component is included in equity and not subsequently remeasured. Upon conversion, the amount initially recognized in “Other capital reserves” will be transferred to “Share premium.” Financial liabilities All financial liabilities are measured subsequently at amortized cost using the effective interest method or at FVTPL. Borrowings (including interest-bearing loans) are initially recognized at fair value, net of transaction costs incurred. Borrowings are subsequently measured at amortized cost. Any difference between the proceeds (net of transaction costs) and the redemption amount is recognized in profit or loss over the period of the borrowings using the effective interest method. Under the effective interest method, amortization is included as a finance cost in the consolidated statement of comprehensive (loss)/income. Non-substantial Borrowings are derecognized from the balance sheet when the obligation specified in the contract is discharged, cancelled or expired. The warrant instruments are recorded at fair value, with changes in the fair value recognized in the consolidated statement of comprehensive (loss)/income, where the terms of the warrant instruments allow for cashless exercise. j) Fair value measurement Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value measurement is based on the presumption that the transaction to sell the asset or transfer the liability takes place either: • In the principal market for the asset or liability; or • In the absence of a principal market, in the most advantageous market for the asset or liability. The principal or the most advantageous market must be accessible by the Company. The fair value of an asset or a liability is measured using the assumptions that market participants would use when pricing the asset or liability, assuming that market participants act in their economic best interest. The Company uses valuation techniques that are appropriate in the circumstances and for which sufficient data are available to measure fair value, maximizing the use of relevant observable inputs and minimizing the use of unobservable inputs. All assets and liabilities for which fair value is measured or disclosed in the consolidated financial statements are categorized within the fair value hierarchy, described as follows, based on the lowest level input that is significant to the fair value measurement as a whole: • Level 1 — quoted (unadjusted) market prices in active markets for identical assets or liabilities. • Level 2 — valuation techniques for which the lowest level input that is significant to the fair value measurement is directly or indirectly observable. • Level 3 — valuation techniques for which the lowest level input that is significant to the fair value measurement is unobservable. For assets and liabilities that are recognized in the consolidated financial statements on a recurring basis, the Company determines whether transfers have occurred between levels in the hierarchy by reassessing categorization (based on the lowest level input that is significant to the fair value measurement as a whole) at the end of each reporting period. k) Impairment of non-financial Further disclosures relating to impairment of non-financial • Disclosures for significant assumptions Note 3 • Property, plant and equipment Note 12 • Intangible assets not yet available for use Notes 13 and 14 At each reporting date, the Company assesses whether there is any indication that an asset may be impaired. If any such indication exists, or when annual impairment testing for an asset is required, the Company estimates the asset’s recoverable amount. An asset’s recoverable amount is the higher of an asset’s or cash-generating unit’s fair value less costs of disposal and its value in use. The recoverable amount is determined for an individual asset, unless the asset does not generate cash inflows that are largely independent of those from other assets or groups of assets. When the carrying amount of an asset or cash-generating unit exceeds its recoverable amount, the asset is considered impaired and is written down to its recoverable amount. In assessing value in use, the estimated future cash flows are discounted to their present value using a pre-tax Impairment losses are recognized in the consolidated statement of comprehensive (loss)/income in expense categories consistent with the function of the impaired asset. An assessment is made at each reporting date to determine whether there is an indication that previously recognized impairment losses no longer exist or have decreased. If such indication exists, the Company estimates the asset’s or cash-generating unit’s recoverable amount. A previously recognized impairment loss is reversed only if there has been a change in the assumptions used to determine the asset’s recoverable amount since the last impairment loss was recognized. The reversal is limited so that the carrying amount of the asset does not exceed its recoverable amount, nor exceed the carrying amount that would have been determined, net of depreciation, had no impairment loss been recognized for the asset in prior years. Such reversal is recognized in the consolidated statement of comprehensive (loss)/income unless the asset is carried at a revalued amount, in which case the reversal is treated as a revaluation increase. l) Cash and short-term deposits Cash and short-term deposits in the balance sheet comprise cash at banks and on hand along with short-term deposits with a maturity of three months or less, which are subject to an insignificant risk of changes in value. m) Provisions Provisions are recognized when the Company has a present obligation (legal or constructive) as a result of a past event, it is probable that an outflow of resources embodying economic benefits will be required to settle the obligation and a reliable estimate can be made of the amount of the obligation. When the Company expects some or all of a provision to be reimbursed, for example, under an insurance contract, the reimbursement is recognized as a separate asset, but only when the reimbursement is virtually certain. The expense relating to a provision is presented in the consolidated statement of comprehensive (loss)/income net of any reimbursement. If the effect of the time value of money is material, provisions are discounted using a current pre-tax Where contingent payments relate to future use of the in-licensed n) Provision for deferred cash consideration Provision for deferred cash consideration consists of future payments which are contractually committed but not yet certain. In respect of products which are not yet approved, such deferred cash consideration excludes potential milestones, royalties or other payments that are deemed to be so uncertain as to be unquantifiable. Deferred cash consideration is recognized as a liability with the amounts calculated as the risk adjusted net present value of anticipated deferred payments. The provision is reviewed at each balance sheet date and adjusted based on the likelihood of contractual milestones being achieved and therefore the deferred payment being settled. Increases in the provision relating to changes in the probability are recognized as an intangible asset. Increases in the provision relating to the unwinding of the time value of money are recognized as a finance expense. o) Share-based payments Employees (including executives) and non-executive non-executive Incentives in the form of shares are provided to employees and non-executive see In accordance with IFRS 2 Share-based Payments (“IFRS 2”), charges for these incentives are expensed through the consolidated statement of comprehensive (loss)/income on a straight-line basis over their vesting period, based on the Company’s estimate of shares that will eventually vest. The total amount to be expensed is determined by reference to the fair value of the options or awards at the date they were granted. For LTIP shares, the fair value on grant date excludes the impact of any non-market Equity-settled share-based payment transactions with parties other than employees are measured at the fair value of the goods or services received, except where that fair value cannot be estimated reliably, in which case they are measured at the fair value of the equity instruments granted, measured at the date the entity obtains the goods or the counterparty renders the service. In accordance with IFRS 2, the cancellation of share options is accounted for as an acceleration of the vesting period and therefore any amount unrecognized that would otherwise have been charged in future accounting periods is recognized immediately. When options are forfeited, the accounting expense for any unvested awards is reversed. p) Costs of issuing capital Incremental costs incurred and directly attributable to the offering of equity securities are deducted from the related proceeds of the offering. The net amount is recorded as share premium in the period when such shares are issued. Where such expenses are incurred prior to the offering they are recorded in prepayments until the offering completes. Other costs incurred in such offerings are expensed as incurred and included in general and administrative expenses. q) Employee Benefit Trust The Company operates an Employee Benefit Trust (“EBT”), the Mereo BioPharma Group plc Employee Benefit Trust. The EBT holds ADS’s to satisfy the exercise of options under the Company’s share-based incentive schemes ( see Shares held by the EBT are included in the consolidated balance sheet as a reduction in equity. r) Pension contribution costs Payments to defined contribution retirement benefit plans are recognized as an expense when employees have rendered service entitling them to the contributions.

Significant judgments, estimate

Significant judgments, estimates and assumptions	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Significant judgments, estimates and assumptions	3. Significant judgments, estimates and assumptions The preparation of these consolidated financial statements requires the management of the Company to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses. The Company bases its estimates and judgments on historical experience and on various other assumptions that it considers to be reasonable. Actual results may differ from these estimates under different assumptions or conditions. Judgments a) Revenue Judgment is required to determine the appropriate accounting for the license and collaboration agreement with Ultragenyx Pharmaceutical, Inc. (“Ultragenyx”). Management has determined that the upfront proceeds from the license and collaboration agreement represent proceeds from the Company’s ordinary business activities and, therefore, represent revenue within the scope of IFRS 15, Revenue from Contracts with Customers. Judgment is also required to determine the portion of the carrying amount of the intangible asset to derecognize, relative to the value retained, as a result of the license and collaboration agreement with Ultragenyx. b) Impairment of intangible assets and property, plant and equipment An assessment was made in respect of indicators of impairment in the carrying value of the Company’s intangible assets (see Note 14), right-of-use If such an indication exists, the recoverable amount of the asset, being the higher of the asset’s fair value less costs to sell and value in use, is compared to the asset’s carrying value. Any excess of the asset’s carrying value over its recoverable amount is recognized as an impairment in the consolidated statement of comprehensive (loss)/income. The assessment of intangible assets involves a number of significant judgments regarding the likelihood of successful product approval, the costs of attaining approval, the estimated useful life of intangible assets following commercialization and the subsequent commercial profitability of the product once approved. c) Incremental borrowing rate and lease modification Future lease payments are discounted using the interest rate implicit in the lease, or, if that rate cannot be readily determined, the incremental borrowing rate. IFRS 16 (Leases) defines the incremental borrowing rate as the rate of interest a lessee would have to pay to borrow over a similar term, and with a similar security, the funds necessary to obtain an asset of similar value to the right-of-use environment. The incremental borrowing rate for the current lease portfolio was determined based on relevant and available information as the interest rate implicit in the lease arrangements cannot be readily determined. In addition to the determination of an appropriate discount rate, the Company was also required to assess the lease term for qualifying leases. The determination of the lease term is judgmental as for certain qualifying leases held by the Company, the contract includes an extension option beyond the non-cancellable In August 2020, a lease for office space was modified to reduce the size of the office space leased. At the time of this lease modification, judgment was applied in determining the new lease term and remeasuring the lease liability by discounting the revised lease payments using a revised incremental borrowing rate. The lease expired in August 2022. d) Identification and classification of financial instruments On June 3, 2020, the Company completed a private placement transaction (Note 19) which comprised the issue of ordinary shares, Loan Notes and Warrants. Judgment is applied under IAS 32 (Financial instruments: Presentation) in determining the features of the identified financial instruments on both the transaction date and the date of the general meeting at which Resolutions relating to the private placement were voted on by the Shareholders, to determine the appropriate recognition in accordance with IAS 32. In applying this judgment, management considered the probability of passing the Resolutions at the general meeting and the likelihood of a change of control prior to the passing of the Resolutions, which impact the settlement terms of the financial instruments, and the classification of the financial instruments as liabilities or equity. Management concluded that a change of control event was uncertain and outside of the Company’s control, and therefore the conversion feature on the Loan Notes at the transaction date represented a financial liability with an embedded derivative for the conversion option. On the passing of the Resolutions, judgment was applied to determine that the effective terms of the Loans Notes changed and the embedded derivative financial liability representing the conversion option was reclassified to equity at its fair value, with no associated gain or loss recognized in profit or loss. Estimates and assumptions a) Deferred consideration Deferred consideration represents contingent cash consideration and is recognized as a provision at each balance sheet date, to the extent its amount is quantifiable at the inception of the arrangement (see Note 18). The amount provided is based on estimates regarding the timing and progress of the related research and development activities (see Note 24). Deferred consideration in the form of shares is recognized as a share-based payment when it is probable that shares will be transferred. b) Fair value of financial instruments As part of the private placement transaction ( see c) Contingent consideration The Company makes a provision for the estimated fair value of amounts payable to the former shareholders of Mereo BioPharma 5, Inc. under the Contingent Value Rights Agreement (“CVR”), which is accounted for as a contingent consideration liability. At December 31, 2022, the Company estimates the fair value of the contingent consideration liability to be £nil (2021: nil). Total potential payments under the CVR on a gross, undiscounted basis, are approximately £58.6 million ($80.0 million). The estimated contingent consideration payable is based on a risk-adjusted, probability-based scenario. Under this approach the likelihood of future payments being made to the former shareholders of Mereo BioPharma 5, Inc. under the CVR is considered. The estimate could materially change over time in line with the development plan and potential subsequent commercialization of the product.

Changes in accounting policies

Changes in accounting policies	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Changes in accounting policies	4. Changes in accounting policies a) New standards, interpretations and amendments adopted from January 1, 2022 In the current year, the Company has applied the below amendments to IFRS issued by the IASB that are effective for an annual period that begins on or after January 1, 2022. Their adoption has not had any material impact on the disclosures or on the amounts reported in these consolidated financial statements: • Annual Improvements to IFRS Standards 2018-2020 (Amendments to IFRS 1, IFRS 9, IFRS 16 and IAS 41) • Amendments to IAS 16 – Proceeds before Intended Use • Amendments to IAS 37 – Onerous Contracts – Cost of Fulfilling a Contract • Amendments to IFRS 3 b) New standards, interpretations and amendments not yet effective At the date of authorization of these consolidated financial statements, the Company has not applied the following new and revised IFRS that have been issued but are not yet effective: Effective January 1, 2023 • Amendments to IFRS 17 – Insurance Contracts • Amendments to IAS 12 – Deferred tax related to assets and liabilities arising from a single transaction • Amendments to IAS 8 – Definition of accounting estimates • Amendments to IAS 1 and IFRS Practice Statement 2 – Disclosure of accounting policies Effective January 1, 2024 • Amendments to IAS 1 – Classification of liabilities as current or non-current • Amendments to IAS 1 – Non-current liabilities with covenants • Amendments to IFRS 16 – Lease liability in a sale and leaseback The Company does not expect the adoption of these IFRS amendments will have a material impact on the Company in the current or future reporting periods and on foreseeable future transactions.

Group information

Group information	12 Months Ended
	Dec. 31, 2022
Investments accounted for using equity method [abstract]
Group information	5. Group information Information about subsidiaries The consolidated financial statements of the Company include: Name Principal activities Country of % Equity % Equity Mereo BioPharma 1 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma 2 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma 3 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma 4 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma Ireland Limited Pharmaceutical R&D Ireland 100 100 Mereo BioPharma 5, Inc. Pharmaceutical R&D US 100 100 Navi Subsidiary, Inc. Pharmaceutical R&D US 100 100 Mereo US Holdings, Inc. Holding Company US 100 100 Mereo BioPharma Group plc Employee Benefit Trust Employee share scheme Jersey — — The registered office of Mereo BioPharma 1 Limited, Mereo BioPharma 2 Limited, Mereo BioPharma 3 Limited and Mereo BioPharma 4 Limited is located at Fourth Floor, 1 Cavendish Place, London W1G 0QF. The registered office of Mereo BioPharma Ireland Limited is Rocktwist House, Block 1, Western Business Park, Shannon, County Clare, V14 FW97, Republic of Ireland. Mereo US Holdings Inc. was incorporated on December 3, 2018 for the sole purpose of effecting the business combination with Mereo BioPharma 5, Inc. (formerly OncoMed Pharmaceuticals, Inc.) on April 23, 2019. The registered office of Mereo US Holdings Inc., Mereo BioPharma 5, Inc. and its wholly owned subsidiary, Navi Subsidiary, Inc., is 251 Little Falls Drive, City of Wilmington, County of New Castle, Delaware 19808, US.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2022
Disclosure Of Revenue From Contracts With Customers [Abstract]
Revenue	6. Revenue The Company recognized upfront proceeds of £36.5 million ($50.0 million) from the license and collaboration agreement with Ultragenyx for setrusumab as revenue in the year ended December 31, 2021. The variable consideration relating to future milestones and sales royalties will be recognized in the consolidated statement of comprehensive (loss)/income when the milestones are achieved or the underlying commercial sales are made, in the event regulatory approval is achieved. As a consequence of the license and collaboration agreement with Ultragenyx and in accordance with terms of the 2015 asset purchase with Novartis, the Company made a payment to Novartis of £7.2 million ($10.0 million). The payment included a deduction for costs of £2.4 million which was deferred and will be recognized in the consolidated statement of comprehensive (loss)/income when the associated costs are incurred. In the year ended December 31, 2022, £0.9 million (2021: £1.1 million) of these deductions were recognized within “Cost of revenue” in the consolidated statement of comprehensive (loss)/income. As of December 31, 2022 ,

(Loss)_profit before tax

(Loss)/profit before tax	12 Months Ended
	Dec. 31, 2022
Schedule Of Detailed Information About Profit Before Tax [Abstract]
(Loss)/profit before tax	7. (Loss)/profit before tax (Loss)/Profit before tax is stated after charging: Year ended December 31, 2022 2021 2020 Fees payable to the Company’s Auditor for the audit of the 371 358 449 Fees payable to the Company’s Auditor for other services: Audit of subsidiary accounts 49 46 49 Audit related assurance services 59 57 318 Gain on modification of lease – – (957 ) Income from sub-lease – – (646 ) Depreciation of right-of-use 583 570 1,531 Depreciation (excluding right-of-use 144 72 68 Gain on modification of lease, sub-lease

Employees

Employees	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Employees	8. Employees Total compensation costs for persons employed by the Company (including Directors) during the year was: Year ended December 31, 2022 2021 2020 Included in research and development expenses: Salaries 4,590 4,126 3,046 Social security costs 456 402 397 Pension contributions 78 73 66 Share-based payment expenses 1,083 1,210 446 Included in administrative expenses: Salaries 4,478 3,763 4,832 Social security costs 606 418 681 Pension contributions 124 99 89 Share-based payment expenses 2,779 2,092 1,112 Total 14,194 12,183 10,669 Total compensation costs for Directors during the year was: Year ended December 31, 2022 2021 2020 Salaries and fees 534 810 1,114 Benefits in kind 9 9 14 Pension contributions 42 58 61 Bonus 226 239 538 Total 811 1,116 1,727 During 2022, one Director was a member of a defined contribution pension scheme (2021: one ;

Other income_expenses and adjus

Other income/expenses and adjustments	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Other income/expenses and adjustments	9. Other income/expenses and adjustments Finance income Year ended December 31, 2022 2021 2020 Bank interest earned 696 1 5 Gain on short-term investments — — 39 Total 696 1 44 Finance costs Year ended December 31, 2022 2021 2020 Interest on convertible loan notes (2,660 ) (3,549 ) (2,241 ) Interest on bank loan — — (2,900 ) Interest on lease liabilities (209 ) (227 ) (1,085 ) Discounting of provision on deferred cash consideration (451 ) (225 ) (157 ) Other (41 ) (21 ) — Total (3,361 (4,022 ) (6,383 ) Changes in the fair value of financial instruments Year ended December 31, 2022 2021 2020 Changes in the fair value of warrants – private placement 7,593 39,535 (45,977 ) Changes in the fair value of warrants – bank loan 212 504 (714 ) Changes in the fair value of embedde d — — (63,158 ) Total 7,805 40,039 (109,849 ) Other income and expenses In February 2022, the Company received a milestone payment of $2.0 million (£1.5 million) under the Navi License Agreement with OncXerna. An associated payment was made to the former shareholders of Mereo BioPharma 5, Inc. under the Contingent Value Rights Agreement (“CVR”) of a total of $0.9 million (£0.7 million), after deductions of costs, charges and expenditures, which resulted in other income, net of £0.8 million.

Taxation

Taxation	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Taxation	10. Taxation Year ended December 31, 2022 2021 2020 UK corporation tax R&D credit 1,296 — 2,822 Tax credit/(charge) 601 (1,516 ) — Total 1,897 (1,516 ) 2,822 U.K. income tax The Company is entitled to claim tax credits in the United Kingdom under the U.K. R&D small or medium-sized U.S. income tax During the year-ended December 31, 2022, the Company received £0.8 million related to Alternative Minimum Tax (“AMT”) credits, previously recognized as other taxes recoverable within the consolidated balance sheet. The Company generates R&D tax credits for U.S. federal and state purposes. In respect of these R&D tax credits, no deferred tax assets have been recognized in any periods presented. As of December 31, 2022, the Company had an uncertain tax position of £3.1 million, representing approximately 20% of these historic R&D tax losses claimed. Reconciliation of effective tax rate Year ended December 31, 2022 2021 2020 (Loss)/profit on ordinary activities before income tax (36,093 ) 14,241 (166,450 ) Tax on profit at standard U.K rate of 19% 6,857 (2,706 ) 31,626 Expenses not deductible for income tax purposes (permanent differences) (965 ) (708 ) (13,270 ) Income not taxable 12 78 4 Temporary timing differences — (65 ) — R&D relief uplift 558 1,435 1,214 Losses (unrecognized) (4,810 ) (345 ) (14,479 ) Foreign tax 422 505 184 Differences in overseas tax rates 323 286 261 Derecognition of deferred tax — — (2,686 ) Effects of carryback loss relief (649 ) — — Adjustments in respect of prior years 612 — — Other (463 ) 4 (32 ) Tax credit/(charge) for the year 1,897 (1,516 ) 2,822 Deferred tax The analysis of unrecognized deferred tax is set out below: Year ended December 31, 2022 2021 2020 Losses 47,209 44,683 37,021 Loan relationships 443 73 421 U.S tax credits 12,206 10,557 9,880 R&D capitalization 3,001 — — Fixed assets — — 414 Share options 434 151 55 Other U.S deferred tax — 31 86 Other — — 137 Temporary differences 51 56 18 Net deferred tax asset (unrecognized) 63,344 55,551 48,032 The analysis of recognized deferred tax At January 1, Recognized At December 31, Deferred tax liabilities Intangible asset and right-of-use (20 ) (156 ) (176 ) Deferred tax asset Net operating losses and lease liability 20 156 176 Net deferred tax asset/(liability) — — — A deferred tax asset on losses has been recognized up to the level of the deferred tax liability, resulting in a net deferred tax liability of £nil. The remaining deferred tax assets, as set out in the table above, have not been recognized as there is uncertainty regarding when suitable future profits against which to offset the accumulated tax losses will arise. U.K. deferred tax The deferred tax assets have not been recognized as there is uncertainty regarding when suitable future profits against which to offset the accumulated tax losses will arise. There is no expiration date for the accumulated tax losses. The standard rate of corporation tax applied to the reported profit/(loss) before tax is 19% (2021: 19%). The Finance Act 2021, which was substantively enacted on May 24, 2021, included provisions to increase the standard rate of U.K. corporation tax from % to %, effective from April 1, 2023. As a result, U.K. deferred tax assets and liabilities have been measured at a rate of %. At December 31, 2022, the Company had U.K. tax losses to be carried forward of approximately £125.8 million. U.S. deferred tax U.S. deferred tax assets and liabilities are calculated at a blended rate of approximately 21%. For Mereo BioPharma 5, Inc, with respect to accumulated tax losses carried forward prior to its acquisition by the Company, there is a change of control restriction which will limit the amount available in any one year. At December 31, 2022, the Company had U.S. federal tax losses to be carried forward of approximately £74.6 million, of which £67.7 million can be carried forward indefinitely and £6.9 million which will begin to expire in 2023. At December 31, 2022, the Company had U.S. state tax losses to be carried forward of approximately £4.0 million which begin to expire in 2027 .

Earnings per share

Earnings per share	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Earnings per share	11. Earnings per share Basic profit/(loss) per share is calculated by dividing the profit/(loss) attributable for the year to ordinary equity holders of the parent by the weighted average number of ordinary shares outstanding during the year. Diluted loss per share is based on dividing the loss Year ended December 31, 2022 2021 2020 Numerator – Basic earnings per share (£’000s): (Loss)/profit (34,196 ) 12,725 (163,628 ) Denominator – Basic earnings per share: Weighted average number of ordinary shares 603,196,403 527,818,648 338,953,141 (Loss)/profit per share – basic (£) (0.06 ) 0.02 (0.48 ) Numerator – Diluted earnings per share (£’000s): (Loss)/profit (34,196 ) 12,725 (163,628 ) Effect of dilutive ordinary shares — (38,523 ) — Numerator – Diluted earnings per share (34,196 ) (25,798 ) (163,628 ) Denominator – Diluted earnings per share: Number of ordinary shares used for basic earnings per share 603,196,403 527,818,648 338,953,141 Weighted average effect of dilutive ordinary shares — 27,457,163 — Weighted average number of diluted ordinary shares outstanding 603,196,403 555,275,811 338,953,141 Loss per share – diluted (£) (0.06 ) (0.05 ) (0.48 ) For the years ended December 31, 2022 and 2020, share options, convertible loan notes and warrants were anti-dilutive as they would have decreased the loss per share and were excluded from the calculation of diluted loss per share. Therefore, the weighted average shares outstanding used to calculate both the basic and diluted loss Share options and convertible loan notes were anti-dilutive for the same year.

Property, plant and equipment

Property, plant and equipment	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Property, plant and equipment	12. Property, plant and equipment Right-of-use Right-of-use Leasehold Office IT Total Cost of valuation At January 1, 2022 2,903 295 557 173 180 4,108 Additions — — — 7 3 10 Disposals (451 ) (300 ) — (16 ) (10 ) (777 ) Currency translation effects 13 5 — — — 18 At December 31, 2022 2,465 — 557 164 173 3,359 Depreciation At January 1, 2022 (1,025 ) (231 ) (124 ) (69 ) (129 ) (1,578 ) Disposals 451 300 — 16 10 777 Depreciation for the year (514 ) (69 ) (95 ) (23 ) (26 ) (727 ) At December 31, 2022 (1,088 ) — (219 ) (76 ) (145 ) (1,528 ) Net book value At January 1, 2022 1,878 64 433 104 51 2,530 At December 31, 2022 1,377 — 338 88 28 1,831 Right-of-use Right-of-use Leasehold Office IT Total Cost of valuation At January 1, 2021 1,848 1,169 164 71 132 3,384 Additions 923 — 393 109 48 1,473 Lease modification 133 30 — — — 163 Disposals — (868 ) — (7 ) — (875 ) Currency translation effects (1 ) (36 ) — — — (37 ) At December 31, 2021 2,903 295 557 173 180 4,108 Depreciation At January 1, 2021 (531 ) (1,023 ) (85 ) (65 ) (107 ) (1,811 ) Disposals — 868 — 7 — 874 Depreciation for the year (494 ) (76 ) (39 ) (11 ) (22 ) (642 ) At December 31, 2021 (1,025 ) (231 ) (124 ) (69 ) (129 ) (1,578 ) Net book value At January 1, 2021 1,318 146 79 6 25 1,573 At December 31, 2021 1,878 64 433 104 51 2,530 In August 2022, the Company’s lease for office space in Redwood City, California expired, and certain equipment was . The Company leases office space and equipment for use in administrative and Within 1 year Between 1 and 3 years Between Over 5 Total £’000s £’000s £’000s £’000s £’000s Maturity of lease liabilities 466 1,072 150 — 1,688 Further details on the movements within lease liability are included in Note 23 .

Intangible assets

Intangible assets	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Intangible assets	13. Intangible assets Acquired £’000s Cost At January 1, 2021 33,005 At December 31, 2021 33,005 At December 31, 2022 33,005 Revisions to estimated value At January 1, 2021 (1,357 ) Revision to estimated value 2,373 Out-license (9,457 ) At December 31, 2021 (8,441 ) Revision to estimated value (448 ) At December 31, 2022 (8,889 ) Net book value At December 31, 2021 24,564 At December 31, 2022 24,116 The Company’s strategy is to acquire and develop clinical-stage development programs for the treatment of rare diseases. On January 25, 2021, the Company’s license and collaboration agreement with Ultragenyx for the development and commercialization of setrusumab for OI became effective. Under the terms of the agreement, the Company received an upfront payment of £36.5 million ($50 million). Additionally, the Company will be eligible to receive up to $254 million in future milestones and royalties. The license and collaboration agreement grants Ultragenyx an exclusive license to develop and commercialize setrusumab in the US and rest of the world, excluding Europe where the Company retains commercial rights. As a result, intangible assets with a carrying value of £9.5 million were derecognized and recorded within “Cost of revenue” in the Company’s consolidated statement of comprehensive income/(loss). Refer to Note 3 for additional information. In October 2017, the Company acquired the exclusive license for alvelestat and included the option to acquire certain assets from AstraZeneca AB (“AstraZeneca”). On that date the fair value of alvelestat was measured at £7.2 million, which consisted of upfront cash and equity payments as well as deferred cash and equity consideration. The provision for deferred cash consideration is re-measured million) due to changes in estimated timelines and the probability of contractual milestones being achieved. Refer to Note 18 and Note 24 for additional information. During the year the Company did not revise the value of any other intangible assets. As the intangible assets remain under development, no amortization charge has been recognized (2021: £nil).

Impairment testing of acquired

Impairment testing of acquired development programs not yet available for use	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Impairment testing of acquired development programs not yet available for use	14. Impairment testing of acquired development programs not yet available for use Acquired development programs not yet available for use are assessed annually for impairment. The carrying amount of acquired development programs is as follows: December 31, 2022 2021 £’000s £’000s BPS-804 /UX143 2,159 2,159 MPH-966 7,760 8,208 BGS-649 9,886 9,886 BCT-197 4,311 4,311 Total 24,116 24,564 The Company considers the future development costs, the probability of successfully progressing each program to product approval and the likely commercial returns after product approval, among other factors, when reviewing for indicators of impairment. The results of this testing did not indicate any impairment of the acquired products’ rights for the year ended December 31, 202 2 The acquired development programs are assets which are not used in commercialized products. These assets have not yet begun to be amortized but have been tested for impairment by assessing their value in use. Value in use calculations for each program are utilized to calculate the recoverable amount. The calculations use pre-tax out-licensed out-licensing Key assumptions for the value in use calculations are described as follows: • Development costs to obtain regulatory approval – costs are estimated net of any contributions expected from collaborative arrangements with future partners. Management have developed cost estimates based on their previous experience and in conjunction with the expertise of their clinical development partners; • Launch dates of products – these reflect management’s expected date of launch for products based on the timeline of development programs required to obtain regulatory approval. The assumptions are based on management’s and clinical development partners’ prior experience; • Probability of successful development – management estimates probabilities of success for each phase of development based on industry averages and knowledge of specific programs; • Out-licensing • Sales projections – these are based on management’s internal projections using external market data and market research commissioned by the Company; • Profit margins and other operational expenses – these are based on the Company’s internal projections of current product manufacturing costings, with input from manufacturing partners where applicable, and estimates of operating costs based on management’s prior industry experience; • Cash flow projections – for all assets, cash flows are assessed over an industry-standard asset life of 20 years; and • Discount rates – the discount rate is estimated on a pre-tax basis reflecting the estimated cost of capital of the Company and is applied consistently across each of the acquired development programs. The cost of capital was determined to be Where an out-licensing At this stage of product development, the key sensitivity for all development programs is the probability of successful completion of clinical trials in order to obtain regulatory approval necessary for commercial sales. Therefore, full impairment of a development program is expected should such clinical trials be unsuccessful.

Other receivables

Other receivables	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Other receivables	15. Other receivables December 31, 2022 2021 £’000s £’000s Lease deposits 293 408 VAT recoverable 362 387 Other 107 624 Total 762 1,419

Cash and short-term deposits

Cash and short-term deposits	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Cash and short-term deposits	16. Cash and short-term deposits December 31, 2022 2021 £’000s £’000s Cash 5,230 93,727 Short-term deposits 51,104 569 Total 56,334 94,296 Short-term deposits are available immediately or within 90 days and earn interest at the respective short-term deposit rates.

Trade and other payables

Trade and other payables	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Trade and other payables	17. Trade and other payables December 31, 2022 2021 £’000s £’000s Trade payables 2,886 2,285 Social security and other taxes 167 190 Other payables 25 24 Total 3,078 2,499 Trade and other payables are non-interest

Provisions

Provisions	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Provisions	18. Provisions December 31, 2022 2021 £’000s £’000s Social security contribution on vested share options 9 — Provision for deferred cash consideration 4,634 4,123 Restructuring 179 — Total 4,822 4,123 Current 4,822 2,803 Non-current — 1,320 Social security Deferred cash Restructuring At January 1, 2021 109 1,525 — Arising/(released) during (109 ) — — Increase in provision due — 225 — Increase in provision due — 2,373 — At December 31, 2021 — 4,123 — Arising/(released) during 9 — 179 Increase in provision due — 451 — Increase in provision due — 508 — Decrease — (448 ) — At December 31, 2022 9 4,634 179 The provision for social security contributions on share options is calculated based on the number of vested options outstanding at the reporting date that are expected to be exercised. The provision is based on the estimated taxable gain arising on exercise of the share options, using the best estimate of the market price at the balance sheet date . The deferred cash consideration is the estimate of the quantifiable but not certain future cash payment obligations due to AstraZeneca for the acquisition of certain assets (see provision is calculated as the risk-adjusted net present value of future cash payments to be made by the Company. The payments are dependent on reaching certain milestones based on the commencement and outcome of clinical trials. The likelihood of achieving such milestones is reviewed at the balance sheet date and increased or decreased as appropriate. In October 2022, the Company announced an updated operating plan, including a targeted reduction in the employee base of up to 40 % and a significant reduction in other costs. In connection with the implementation of the operating plan, restructuring costs primarily relating to employee severance and other termination benefits of £0.2 million were paid during the year and as of December 31, 2022, the remaining provision is £0.2 million.

Private Placement

Private Placement	12 Months Ended
	Dec. 31, 2022
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Private Placement	19. Private placement On June 3, 2020, the Company completed a £56 million private placement transaction which comprised of the issuance of 89,144,630 ordinary shares of £0.003 each at a price of £0.174 per share for total proceeds of £15.5 million, and the issue of Tranche 1 convertible loan notes (the “Loan Notes”) for total proceeds of £40.5 million. The investors also received conditional warrants to subscribe for an additional 161,048,366 ordinary shares (the “Warrants”). The terms of the Loan Notes and Warrants, and, in particular, their ability to be converted into ordinary shares was conditional on the passing of certain resolutions (the “Resolutions”) at a subsequent general meeting of shareholders held on June 30, 2020. At that date, the Resolutions were passed, and the Loan Notes became convertible into ordinary shares. Loan Notes The Loan Notes bear interest at a rate of 6% per annum and have an initial maturity date of June 30, Loan Notes in an aggregate principal amount of £40.5 million were issued on June 3, 2020 and became convertible upon the passing of the Resolutions. As a result, on June 30, 2020, Loan Notes in an aggregate principal amount of £21.8 million, together with accrued interest, were automatically converted into 125,061,475 ordinary shares, and Loan Notes in an aggregate principal amount of £18.9 million remained outstanding as of December 31, 2020. See Note 21. During the year ended December 31, 2022, the Company issued and allotted 40,020,280 ordinary shares (2021: 40,397,976 ordinary shares) at a price of £0.174 per share on conversion of Loan Notes. As of December 31, 2022, Loan Notes in an aggregate principal amount of £6.2 million (2021: million) remain outstanding. Warrants Participants in the private placement transaction received conditional warrants to subscribe for further ordinary shares in an aggregate number equal to 50 percent of both the ordinary shares purchased and the ordinary shares issuable upon conversion of the Loan Notes. A total of 161,048,366 Warrants were issued. The fair value of the warrants at inception was £4.1 million. The Warrants have an exercise price of £0.348 per share and are exercisable at any time until their expiry o The Loan Notes and the Warrants were recognized as separate financial instruments. Transaction costs directly attributable to the private placement transaction were apportioned across the ordinary shares, Loan Notes and Warrants.

Warrant liability

Warrant liability	12 Months Ended
	Dec. 31, 2022
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Warrant liability	20. Warrant liability December 31, 2022 2021 £’000s £’000s At January 1 8,336 50,775 Issued during the year — — Settled during the year — (2,400 ) Fair value changes during the year (7,805 ) (40,039 ) At December 31 531 8,336 The change in fair value of the warrant liability represents an unrealized gain in the years ended December 31, 2022 and 2021. Warrants – private placement As a part of the private placement transaction on June 3, 2020, the participating investors received conditional warrants entitling them to subscribe for an aggregate of 161,048,366 ordinary shares in the Company. The warrants were conditional on certain Resolutions being passed at the Company’s general meeting on June 30, 2020. On the passing of the Resolutions, the warrants entitled the investors to subscribe for ordinary shares at an exercise price of £0.348 per warrant and are exercisable until June 30, million was recognized as a gain in the consolidated statement of comprehensive (loss)/income. During the year-ended December 31, 2022, Warrants – bank loan As of December 31, 2022 and 2021, the former lenders of the Company have warrants outstanding to purchase a total of 1,243,908 ordinary shares at an exercise price of £2.95 per share exercisable until August 2027 and a total of ordinary shares at an exercise price of per share exercisable until October 2028. At December 31, 2022, the fair value of these warrants were £0.1 million (2021: £0.3 million). There were no warrants exercised during the year ended December 31, 2022 (2021: nil). Total outstanding warrants At December 31, 2022, a total of 147,431,351 warrants are outstanding (2021: 147,431,351). The warrants outstanding are equivalent to 24% of the issued ordinary share capital of the Company (2021: 25%). The following table lists the weighted average inputs to the models used for the fair value of warrants: December 31, 2022 2021 Expected volatility (%) 95 75 Risk-free interest rate (%) 3.99 0.9 Expected life of warrants (years) 0.5 1.5 Market price of ADS ($) 0.75 1.60 Model used Black-Scholes Black-Scholes

Convertible loan notes

Convertible loan notes	12 Months Ended
	Dec. 31, 2022
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Convertible loan notes	21. Convertible loan notes December 31, 2022 2021 £’000s £’000s Novartis Loan Note 4,449 3,771 Loan Notes – private placement 6,636 10,613 Total 11,085 14,384 Current 11,085 — Non-current — 14,384 Novartis Loan Note On February 10, 2020, the Company entered into a convertible equity financing with Novartis Pharma (AG) (“Novartis”) under which Novartis purchased a £3.8 million convertible loan note (the “Novartis Loan Note”). The Novartis Loan Note is convertible at the discretion of the holder, at a fixed price of £0.265 per ordinary share and bears an interest rate of 6% per annum with a maturity date of February 10, February 2025 Refer to Note 28 for additional information. Loan Notes – private placement The initial issuance of Loan Notes in an aggregate principal amount of £40.5 million were issued on June 3, 2020 and formed part of the private placement transaction ( see Non-closely The fair value of the embedded derivative liability was £11.9 million on initial recognition and the fair value of the liability component was £24.4 million (net of transaction costs). In 2020, between initial recognition and the passing of the Resolutions ( see (loss)/i n The Loan Notes were not convertible until certain Resolutions were passed at the Company’s general meeting on June 30, 2020, following which Loan Notes in an aggregate principal amount of £21.7 million (together with accrued interest) were automatically converted into 125,061,475 ordinary shares. Accordingly, a reduction in interest bearing loans of £13.3 million together with the derecognition of the embedded derivative relating to the conversion feature of £41.6 million was recognized; no gain or loss was recognized on conversion. The remaining portion of the embedded derivative relating to the conversion feature attributable to the Loan Notes outstanding of £33.5 million was reclassified to equity to reflect the effective change in the terms of the feature following the passing of the Resolutions. The movements in the carrying value of the liability component of the Loan Notes is included in the table below. Refer to Note 22 for details of Loan Notes converted to equity. December 31, 2022 2021 £’000s £’000s January 1 10,613 12,946 Issued — — Interest charge 1,981 2,974 Converted to equity (5,958 ) (5,307 ) December 31 6,636 10,613

Issued capital and reserves

Issued capital and reserves	12 Months Ended
	Dec. 31, 2022
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Issued capital and reserves	22. Issued capital and reserves Ordinary Ordinary Share Number £’000s £’000s As at January 1, 2020 97,959,622 294 121,684 Issued on February 11, 2020 14,295,520 43 2,511 Issued on February 20, 2020 12,252,715 37 2,267 Issued on June 4, 2020 89,144,630 267 15,244 Issued on June 30, 2020 125,061,475 375 21,386 Issued on December 23, 2020 239,179 1 — Transaction costs for issued share capital — — (1,307 ) As at December 31, 2020 338,953,141 1,017 161,785 Issued during the year 245,955,098 738 85,909 Transaction costs for issued share capital — — (234 ) As at December 31, 2021 584,908,239 1,755 247,460 Issued during the year 40,020,280 120 6,843 As at December 31, 2022 624,928,519 1,875 254,303 Since January 1, 2020, the following alterations to the Company’s share capital have been made. For each share issuance, ordinary shares of £0.003 in nominal value in the capital of the Company were issued. • On February 11, 2020, the Company issued and allotted 11,432,925 ordinary shares at a price of £0.20 per share to Aspire Capital Fund, LLC (“Aspire Capital”). Gross cash received was £2.3 million. Aspire Capital has also committed to subscribe for up to an additional $25 million of ordinary shares exchangeable for ADSs from time to time during a 30-month non-cash • On February 20, 2020, the Company issued and allotted 12,252,715 0.19 2.3 • On June 4, 2020, the Company issued and allotted 89,144,630 0.174 15.5 13.4 2.1 • On June 30, 2020, the Company issued and allotted 125,061,475 0.174 21.8 • On December 23, 2020, 690,205 138,041 47,835 0.348 • On February 12, 2021, the Company issued and allotted 198,375,000 0.003 0.395 39,675,000 2.726 78.4 0.2 • During the year ended December 31, 2021, 14,954,491 2,990,898 4,621,147 924,229 0.348 460,135 92,027 0.348 0.2 • On May 4, 2021, the Company issued and allotted 2,100,840 0.003 0.517 non-cash, 1.5 1.09 1.09 0.2 • During the year ended December 31, 2021, the Company issued and allotted 40,397,976 0.003 0.174 non-cash • During the year ended December 31, 2022, the Company issued and allotted 40,020,280 0.003 0.174 non-cash Other capital reserves Share- Equity Other Merger Other Total At January 1, 2020 18,285 — 44 40,818 — 59,147 Share-based payments expense during the year 1,558 — — — — 1,558 Novartis convertible loan note instrument and warrants — 1,084 — — — 1,084 Conversion of Loan Notes — — — — 33,104 33,104 Reclassification of the embedded derivative — 33,481 — — — 33,481 At December 31, 2020 19,843 34,565 44 40,818 33,104 128,374 Share-based payments expense during the year 3,302 — — — — 3,302 Share options exercised (119 ) — — — — (119 ) Conversion of Loan Notes — (1,722 ) — — — (1,722 ) At December 31, 2021 23,026 32,843 44 40,818 33,104 129,835 Share-based payments expense during the year 3,862 — — — — 3,862 Share options exercised (82 ) — — — — (82 ) Issuance of warrants — — 70 — — 70 Conversion of Loan Notes — (1,005 ) — — — (1,005 ) At December 31, 2022 26,806 31,838 114 40,818 33,104 132,680 Share-based payments The Company has various share option schemes under which options to subscribe for the Company’s shares have been granted to certain executives, non-executive The share-based payment reserve is used to recognize (i) the value of equity settled share-based payments provided to employees, including key management personnel, as part of their remuneration and (ii) deferred equity consideration. Refer to Note 26 for further details. Equity component of convertible loan instrument The convertible loan notes issued to Novartis are a compound instrument consisting of a liability and an equity component. The value of the equity component (cost of the conversion option) as at December 31, 2022 is £1.08 million (December 31, 2021: £1.08 million). On June 30, 2020, the Loan Notes in an aggregate principal amount of £21.8 million (together with accrued interest) were automatically converted into 125,061,475 ordinary shares. This resulted in £33.5 million recognized in other reserves in equity as a difference between the share capital and share premium recognized on conversion and the carrying value of the embedded derivative financial liability extinguished (see ). Other warrants issued The funding arrangements with The Alpha-1 m Merger reserve The consideration paid to acquire Mereo BioPharma 5, Inc. was 24,783,320 ordinary shares with an acquisition date fair value of £40.9 million, based on the Company’s quoted share price. The nominal value of the issued capital was £0.1 million with the excess, £40.8 million, classified within other capital reserves as a ‘Merger reserve’. Other reserves On June 30, 2020, the Company issued and allotted 125,061,475 ordinary shares of £0.003 in nominal value in the capital of the Company at a price of £0.174 per share to investors following the partial conversion of the Loan Notes. The legal proceeds were £21.8 million. This resulted in £33.1 million recognized in other reserves as a difference between the carrying value of the financial liability extinguished and the legal proceeds. Accumulated loss Year ended December 31, 2022 2021 2020 Other reserves 7,401 7,401 5,001 Accumulated losses (331,164 ) (296,968 ) (309,693 ) Other reserves represent a capital reduction undertaken in 2016 which created a reserve of £7.0 million. On June 3, 2020, the Company issued and allotted 89,144,630 ordinary shares to investors. The difference between the gross proceeds, £15.5 million, and the fair value of the consideration of the ordinary shares, £13.4 million, of £2.1 million, was recognized as a reduction to other reserves. During the year ended December 31, 2021, 15,414,626 private placement warrants were exercised, resulting in a £2.4 million reduction in the warrant liability which was recognized as an addition to “Other reserves.”

Changes in liabilities arising

Changes in liabilities arising from financing activities	12 Months Ended
	Dec. 31, 2022
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Changes in liabilities arising from financing activities	23. Changes in liabilities arising from financing activities Lease Novartis Warrant Deferred Loan Other Total Carrying value at January 1, 2021 1,794 3,196 50,775 1,525 12,946 62 70,298 Financing cash flows (692 ) — — — — — (692 ) Non-cash Settled during the year — — (2,400 ) — (5,307 ) — (7,707 ) Interest expense 230 575 — 206 2,974 18 4,003 Lease addition 910 — — — — — 910 Lease modification 163 — — — — — 163 Changes in fair value — — (40,039 ) 2,373 — — (37,666 ) Changes in foreign exchange (29 ) — — 19 — — (10 ) Carrying value at December 31, 2021 2,376 3,771 8,336 4,123 10,613 80 29,299 Financing cash flows (937 ) — — — — 153 (784 ) Non-cash Settled during the year — — — — (5,958 ) — (5,958 ) Interest expense 209 678 — 451 1,981 19 3,338 Issuance of warrants — — — — — (70 ) (70 ) Changes in fair value — — (7,805 ) (448 ) — — (8,253 ) Changes in foreign exchange 40 — — 508 — — 548 Carrying value at December 31, 2022 1,688 4,449 531 4,634 6,636 182 18,120

Financial and capital risk mana

Financial and capital risk management and fair value measurement	12 Months Ended
	Dec. 31, 2022
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Financial and capital risk management and fair value measurement	24. Financial and capital risk management and fair value measurement Capital risk management The Company’s objectives when managing capital are to safeguard the ability to continue as a going concern and ensure that sufficient capital is in place to fund the Company’s R&D activities and operations. The Company’s principal methods of adjusting the capital available are through issuing new shares, licensing and/or collaboration agreements or arranging suitable debt financing. The Company’s share capital and share premium are disclosed in Note 22 . . The Company has an Employee Benefit Trust which holds ADSs to satisfy exercises of options under the Company’s share option schemes (see Note 26). Financial risk management objectives and policies The Company seeks to maintain a balance between equity capital and convertible debt to provide sufficient cash resources to execute the business plan. In addition, the Company maintains a balance between cash held on deposit and short- term investments in pound sterling and other currencies to reduce its exposure to foreign exchange fluctuations in respect of its planned expenditure. Company’s principal financial instruments comprise warrants, convertible loan notes and trade payables which arise directly from its operations. The Company has various financial assets, including receivables and cash and short-term deposits. Interest rate risk The Company’s policy in relation to interest rate risk is to monitor short and medium-term interest rates and to place cash on deposit for periods that optimize the amount of interest earned while maintaining access to sufficient funds to meet the cost of is operating activities and future research and development activities. The Company’s interest payable on convertible loan notes is fixed. Consequently, there is no material exposure to interest rate risk in respect of interest payable. Credit risk The Company is dependent on a number of third parties for the delivery of its programs and, where required, pays upfront deposits and fees in advance of the delivery of services. The Company considers all of its material counterparties to be creditworthy and the credit risk for each of its major counterparties to be low, but continues to assess credit risk as part of its management of these third-party relationships. The Company’s maximum exposure to credit risk for the components of the balance sheet at December 31, 2022 are the carrying amounts. Liquidity risk The Company’s policy is to maintain adequate cash reserves at highly rated banks and financial institutions and also seeks to invest in short-term deposits to achieve a competitive rate of return. The Company’s liquid resources are invested with regard to the timing of payments to be made in the ordinary course of business, while monitoring its funding requirements through preparation of short-term, mid-term The table below summarizes the maturity profile of the Company’s financial liabilities based on contractual undiscounted payments at December 31, 2022: Within Between Between Over 5 years Total £’000s £’000s £’000s £’000s £’000s Leases 611 1,222 152 — 1,985 Trade and other payables 3,078 — — — 3,078 Accruals 4,491 — — — 4,491 The Company does not face a significant liquidity risk with regards to its lease liabilities. The Company may incur potential payments upon achievement of clinical, regulatory and commercial milestones, as applicable, or royalty payments that may be required to be made under license agreements the Company entered into with various entities pursuant to which the Company has in-licensed Foreign currency and market risk Foreign currency risk arises from R&D activities, commercial transactions and recognized assets and liabilities in foreign currencies, with the principal currency exposure being fluctuations in pound sterling, U.S. dollars and Euros. The functional currency of the Company and all subsidiaries is pound sterling, except for Mereo BioPharma 5, Inc. whose functional currency is U.S. dollars. The Company incurs expenditures in foreign currencies and is exposed to the risks of foreign exchange rate movements, with the impact recognized in the consolidated statement of comprehensive income/(loss). Funding secured in 2021 and 2020 was principally in U.S dollars and, although the Company currently has no revenue from product sales, proceeds received from upfront milestones under its licensing and collaboration agreements are denominated in U.S. dollars, while the majority of operating costs are denominated in pound sterling, U.S. dollars and Euros. The Company seeks to minimize this exposure by passively maintaining foreign currency cash balances at levels appropriate to meet foreseeable foreign currency expenditures. The Company does not hedge potential future cash flows or income. The table below shows analysis of the pound sterling equivalent of period-end December 31, 2022 2021 £’000s £’000s Pound sterling 52,812 92,104 U.S. dollars 2,484 2,018 Euro 1,029 165 Swiss francs 9 9 Total 56,334 94,296 The table below shows those transactional exposures that give rise to net currency gains and losses recognized in the consolidated statement of comprehensive income/(loss). Such exposures comprise the net monetary assets and monetary liabilities of the Company that are not denominated in the functional currency of the relevant subsidiary. As at December 31, these exposures were as follows: December 31, 2022 2021 Net foreign currency assets/(liabilities) £ ’000s £ ’000s U.S. dollars 872 920 Euro 768 (142 ) Swiss francs (179 ) 9 Total 1,461 787 The most significant currencies in which the Company transacts, other than pound sterling, are the U.S. dollar and the Euro. The Company also transacts in other currencies as necessary. The following table illustrates the sensitivity to a 10% weakening or strengthening in the period-end dollar and the Euro against pound sterling: December 31, 2022 U.S. dollar Euro £’000s £’000s Loss before tax (79 ) (70 ) Equity (79 ) (70 ) December 31, 2021 U.S. dollar Euro £’000s £’000s Profit before tax (84 ) 13 Equity (84 ) 13 Financial instruments by category Fair value December 31, Amortized cost December 31, 2022 2021 2022 2021 Financial assets £ ’000s £ ’000s £ ’000s £ ’000s Cash and short-term deposits — — 56,334 94,296 Other receivables — — 400 1,032 Total financial assets — — 56,734 95,328 Financial liabilities Provisions 4,634 4,123 187 — Convertible loan notes — — 11,086 14,384 Warrant liability 531 8,336 — — Trade and other payables — — 2,911 2,309 Accruals — — 4,491 3,826 Lease liability — — 1,688 2,376 Total financial liabilities 5,165 12,459 20,363 22,895 The carrying values of financial assets and financial liabilities recorded at amortized cost in the consolidated financial statements are approximately equal to their fair values. Fair value hierarchy Liabilities measured at fair Date of valuation Total Quoted prices Significant Significant £’000s £’000s £’000s £’000s Provision for deferred consideration (Note 18) December 31, 2022 4,634 — — 4,634 Warrant liability (Note 20) December 31, 2022 531 — 129 402 Liabilities measured at fair Date of valuation Total Quoted prices Significant Significant £’000s £’000s £’000s £’000s Provision for deferred consideration (Note 18) December 31, 2021 4,123 — — 4,123 Warrant liability (Note 20) December 31, 2021 8,336 — 341 7,995 There were no transfers between Level 1 and Level 2 during the years ended December 31, 2022 and 2021. The following table presents the changes in Level 3 items for the years Provision for Warrant £’000s £’000s January 1, 2021 1,525 49,930 Settled during the year — (2,400 ) Unwinding of the time value of money (recognized as a finance cost) 225 — Change in estimate relating to probabilities (revision to intangible asset, 2,373 — Change in fair value — (39,535 ) December 31, 2021 4,123 7,995 Unwinding of the time value of money (recognized as a finance cost) 451 — Change in foreign exchange rates 508 — Change in estimate relating to probabilities (revision to intangible asset, (448 ) — Change in fair value — (7,593 ) December 31, 2022 4,634 402 The following methods and assumptions were used to estimate the fair values: • The fair value of the provision for deferred cash consideration is estimated by discounting future cash flows using rates currently available for debt on similar terms and credit risk. In addition to being sensitive to a reasonably possible change in the forecast cash flows or the discount rate, the fair value of the deferred cash consideration is also sensitive to a reasonably possible change in the probability of reaching certain milestones. The valuation requires management to use unobservable inputs in the model, of which the significant unobservable inputs are disclosed in the tables below. The Company regularly assesses a range of reasonably possible alternatives for those significant unobservable inputs and determines their impact on the total fair value. • At December 31, 2022, the Company estimates the fair value of the contingent consideration liability to be £nil. CVR payments of £0.7 million in 2022 and £0.4 million in 2020 were made relating to the Navi milestones received from OncXerna. The estimated contingent consideration payable is based on a risk adjusted, probability-based scenario. Under this approach the likelihood of future payments being made to the former shareholders of Mereo BioPharma 5, Inc. under the CVR arrangement is considered. The estimate could materially change over time as the development plan and subsequent commercialization of the Navi product progresses. • The warrant liability is estimated using a Black-Scholes model, taking into account appropriate amendments to inputs in respect of volatility, remaining expected life of the warrants and rates of interest at each reporting date. The significant unobservable inputs used in the fair value measurements categorized within Level 3 of the fair value hierarchy, together with a quantitative sensitivity analysis as at December 31, 2022 and 2021 are as follows: Valuation Significant unobservable inputs Input range Sensitivity of the input to fair value Provision for deferred cash consideration Discounted cash flow WACC 2022: 15% 1% increase/decrease would result in a decrease/increase in fair value by £25,000 WACC 2021: 12% 1% increase/decrease would result in a decrease/increase in fair value by £31,000 Probability of success 2022: 40.6 %- 81.2% 10% increase/decrease would result in an increase/decrease in fair value by £0.6 million Probability of success 2021: 40.6% - 81.2% 10% increase/decrease would result in an increase/decrease in fair value by £0.5 million Contingent consideration liability Discounted cash flow Ongoing uncertainty in the clinical development of the Navi product Total potential payments future payments relating to the contingent consideration liability on a gross, undiscounted basis are approximately $80 million. Regulatory approval and commercialization risks Sensitivity of the input to fair value is primarily driven by uncertainty in the clinical development of the Navi product. Future potential payments under the CVR arrangement are contingent on i) future development milestones and ii) future sales of the Navi product, following regulatory approval and commercialization. In January 2020, the Company entered into the license agreement as detailed in Note 13. Although pursuant to the license agreement the Company is entitled to additional payments of up to $302 million, there continues to be significant uncertainty in respect of any milestone and royalty payments under the license agreement. Warrant liability related to the private placement Black-Scholes model Expected volatility 2022: 95.5% Volatility was estimated by reference to the 0.4 year historical volatility of the historical share price of the Company, matching the maturity of the instrument. If the volatility is decreased to 91.8% based on 3-month historical volatility, the carrying value of the warrants as of December 31, 202 2 Expected volatility 2021: 75.1% Volatility was estimated by reference to the 1.4 years historical volatility of the historical share price of the Company, matching the maturity of the instrument. If the volatility is decreased to 67.4% based on 1-year historical volatility, the carrying value of the warrants as of December 31, 2021 would decrease to £6.7 million.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2022
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Commitments and contingencies	25. Commitments and contingencies Each of Mereo BioPharma 1 Limited, Mereo BioPharma 2 Limited and Mereo BioPharma 3 Limited (together, the “Subsidiaries”) issued to Novartis loan notes (which were assigned by Novartis to the Company in exchange for ordinary shares pursuant to the Subscription Agreement) and each of the Subsidiaries agreed to make future payments to Novartis comprising amounts equal to ascending specified percentages of tiered annual worldwide net sales (beginning at high single digits and reaching into double digits at higher sales) by such Subsidiary of products that include the assets acquired. The levels of ascending percentages of tiered annual worldwide net sales are the same for each Subsidiary under the respective Purchase Agreements. Each Subsidiary further agreed that in the event it transfers, licenses, assigns or leases all or substantially all of its assets, it will pay Novartis a percentage of the proceeds of such transaction. The Company will retain the majority of the proceeds from such a transaction. Such percentage is the same for each Subsidiary under the respective Purchase Agreements. The payment of a percentage of proceeds is not payable with respect to any transaction involving equity interests of Mereo BioPharma Group plc, a merger or consolidation of Mereo BioPharma Group plc, or a sale of any assets of Mereo BioPharma Group plc. In October 2017, the Company’s wholly owned subsidiary Mereo BioPharma 4 Limited entered into an exclusive license and option agreement (“the License Agreement”), to obtain from AstraZeneca an exclusive worldwide, sub-licensable sub-licensing licensed-product-by-licensed-product country-by-country The License Agreement will expire on the expiry of the last-to-expire The Company enters into contracts in the normal course of business with contract research organizations (“CROs”), contract manufacturing organizations (“CMOs”) and other third parties to assist in the performance of research and development activities and other services and products for operating purposes. The contracts with CROs generally provide for termination on notice, and therefore, are cancellable contracts and not included herein. The of 2022.

Share-based payments

Share-based payments	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Share-based payments	26. Share-based payments The charge for share-based payments arises across the following schemes: Year ended 2022 2021 2020 £’000s £’000s £’000s 2019 Equity Incentive Plan 3,149 2,860 922 2019 NED Equity Incentive Plan 713 499 167 2015 Plan — — 3 Mereo BioPharma Group plc Share Option Plan — 68 376 Long Term Incentive Plan — (125 ) 90 Total 3,862 3,302 1,558 2019 Equity Incentive Plan (“EIP”) and 2019 Non-Executive The 2019 EIP and 2019 NED EIP were adopted on April 4, 2019, and subsequently amended on February 3, 2020 and January 15, 2021. The 2019 EIP provides for the grant of market value options over ADSs (each ADS is represented by 5 ordinary shares) to executive directors and employees. The 2019 NED EIP provides for the grant of market value options over ADSs to non-executive During the years ended December 31, 2022, 2021 and 2020, market value options were granted to executive directors and employees under the 2019 EIP. Subject to the executive director or employees continued employment, one-fourth During the years ended December 31, 2022, 2021 and 2020, market value options were granted to non-executive one-year The fair value of share options granted were estimated at the date of grant using a Black-Scholes pricing model, taking into account the terms and conditions upon which the share options were granted. The fair value calculation does not include any allowance for dividends as the Company has no available profits for distribution. The exercise price of the share options will be equal to the market price of the underlying shares on the date of grant. The contractual term of the share options is 10 years. During the year ended December 31, 2022, deferred restricted stock units (“Deferred RSUs”) under the 2019 NED EIP were granted to NEDs who elected to receive Deferred RSUs over ADSs in lieu of annual cash compensation for the period . year 180 The number of Deferred RSUs to be granted were determined by dividing the estimated amount of the annual cash compensation by the average closing trading price of the Company’s ADSs over the most recent 30 The following table illustrates the number and weighted average exercise prices (WAEP) of, and movements in, options for the 2019 EIP and 2019 NED EIP and the number of Deferred RSUs for the 2019 NED EIP during the year-ended December 31, 2022: 2019 EIP 2019 NED EIP Options ADS Number WAEP $ Deferred Number Options ADS Number WAEP $ Outstanding at January 1, 2022 3,943,702 2.88 — 421,791 2.90 Granted during the year 4,126,400 1.38 386,144 535,488 1.22 Cancelled during the year (1,164,197 ) 1.83 (42,104 ) (42,192 ) 1.01 Forfeited during the year (48,044 ) 3.97 — — Exercised during the year — — — — Outstanding at December 31, 6,857,861 2.15 344,040 915,087 2.00 Exercisable at December 31, 2022 2,082,027 2.95 — 832,584 2.09 The following table illustrates the number and weighted average exercise prices (WAEP) of, and movements in, options for the 2019 EIP and 2019 NED EIP during the year-ended December 31, 2021: 2019 EIP 2019 NED EIP Options Number WAEP $ Options Number WAEP $ Outstanding at January 1, 2021 1,567,873 2.94 149,416 3.06 Granted during the year 2,696,960 2.83 296,000 2.81 Cancelled during the year (253,277 ) 2.66 (23,625 ) 2.72 Forfeited during the year (28,521 ) 5.37 — — Exercised during the year (39,333 ) 2.11 — — Outstanding at December 31, 2021 3,943,702 2.88 421,791 2.90 Exercisable at December 31, 2021 727,698 3.16 386,623 2.91 The weighted average remaining contractual life for the share options outstanding as at December 31, 2022 for the 2019 EIP was 8.4 years (2021: 8.7 years) and for the 2019 NED EIP was 8.5 years (2021: 8.6 years). The weighted average fair value of options granted during the year was $ per ADS (2021: $ per ADS). Options outstanding at the end of the year had an exercise price of between $ and $ per ADS . The weighted average fair value of Deferred RSUs over ADSs granted during the year was $0.99 per ADS . The 2015 Plan Under the Mereo BioPharma Group Limited Share Option Plan (the “2015 Plan”), the Company, at its discretion, granted share options to acquire ordinary shares to 2022 2021 Options Number WAEP £ Options Number WAEP £ Outstanding at January 1 8,297,694 1.31 8,923,600 1.32 Forfeited during the year (423,164 ) 1.55 (625,906 ) 1.29 Outstanding at December 31 7,874,530 1.46 8,297,694 1.31 Exercisable at December 31 7,874,530 1.46 8,297,694 1.31 The weighted average remaining contractual life for the share options outstanding as at December 31, 2022 was 2.6 years (2021: 3.6 years). Options outstanding at the end of the year had an exercise price of between £1.43 and £2.44 per ordinary share The Mereo Share Option Plan The Mereo Share Option Plan (“Share Option Plan”) provides for the grant of options to acquire ordinary shares to employees, executive directors and executive officers. Options may be granted to all eligible employees on commencement of employment and may be granted on a periodic basis after that. Under the Share Option Plan, the Board of Directors may determine if the vesting of an option will be subject to the satisfaction of a performance condition. Following the introduction of the EIP and NED EIP, no further share option grants under the Share Option Plan are envisaged. The following table illustrates the number and weighted average exercise prices (WAEP) of, and movements in, options for the Option Plan during the year: 2022 2021 Options Number WAEP £ Options Number WAEP £ Outstanding at January 1 1,323,965 3.04 1,411,395 3.14 Forfeited during the year (770,805 ) 3.32 (87,430 ) 3.11 Outstanding at December 31 553,160 3.49 1,323,965 3.04 Exercisable at December 31 553,160 3.49 1,323,965 3.04 The weighted average remaining contractual life for the share options outstanding as at December 31, 2022 was 4.8 years (2021: 5.6 years). Options outstanding at the end of the year had an exercise price of between £3.05 and £3.59 per ordinary share. Long Term Incentive Plan Under the Company’s Long Term Incentive Plan (LTIP), initiated in 2016, the Company, at its discretion, may grant nil-cost The fair value of the LTIP Share Price Element is estimated at the date of grant using a Monte Carlo pricing model, taking into account the terms and conditions upon which the share options were granted. The fair value of the LTIP Strategic Element is estimated at the date of grant using a Black- Scholes pricing model, taking into account the terms and conditions upon which the share options were granted, and the expense recorded is based upon the expected level of achievement of non-market The fair value calculations do not include any allowance for dividends as the Company has no available profits for distribution. The contractual term of the LTIP options is five years. 2022 Number 2021 Number Outstanding at January 1 — 482,748 Lapsed during the yea r — (482,748 ) Outstanding at December 31 — — Exercisable at December 31 — — All LTIP options lapsed during the year ended December 31, 2021. No LTIP options were granted during the years ended December 31, 2021 and 2022 and no further grants are envisaged. Deferred Bonus Share Plan Under the previous terms of the Company’s Deferred Bonus Share Plan (DBSP), 30% of the annual bonus for 2017 for the senior management team was payable in deferred shares, which are governed by the DBSP plan rules. At the date of grant of the awards, the monetary bonus amount was divided by the closing share price to give the number of shares issued to the employee under the DBSP. The number of shares is fixed and not subject to adjustment between the issue date and vesting date. Under the DBSP, awards vest after three years from the date of the award. There are no further performance conditions attached to the award, nor any service conditions (including no requirement for continued employment once the awards have been made). Since the awards are issued at nil cost, they will be satisfied by the issue of ADSs from the Employee Benefit Trust. The outstanding number of options as at December 31, 2021 was all of which were exercisable and had a weighted average life of . During the year ended December 31, 2022, options lapsed (2021: 62,183) and options were exercised (2021: nil). There are no options outstanding as at December 31, 2022. For the 2018 and 2019 financial years, under the Deferred Bonus Plan (“2019 DBP”), 100% of the annual bonus was paid in cash, of which 30% of amounts granted to the senior management team (after deduction of income tax and the relevant employee’s national insurance contributions) was required to be utilized to acquire shares in the Company in the open market within 12 months of the grant of the award. No further grants under the DBSP are envisaged. Deferred equity consideration In October 2017, the Company’s wholly owned subsidiary Mereo BioPharma 4 Limited entered into an exclusive license and option agreement (the “License Agreement”) to obtain from AstraZeneca an exclusive worldwide, sub-licensable MPH-966, Under the agreement with AstraZeneca, the Company may issue up to 1,349,693 ordinary shares which are dependent on achieving certain milestones. Weighted average inputs The following table includes the weighted average inputs to the models used for the fair value of share options granted during the year ended December 31, 2022: 2019 EIP 2019 NED EIP Expected volatility (%) 96 96 Risk-free interest rate (%) 1.83 1.96 Expected life of share options (years) 10 10 Market price of ADSs ($) 1.38 1.22 Model used Black-scholes Black-scholes During the year ended December 31, 2022, no grants of share options were issued under any other scheme. The following table includes the weighted average inputs to the models used for the fair value of share options granted during the year ended December 31, 2021: 2019 EIP 2019 NED EIP Expected volatility (%) 97 98 Risk-free interest rate (%) 1.15 1.09 Expected life of share options (years) 10 10 Market price of ADSs ($) 2.83 2.81 Model used Black-scholes Black-scholes During the year ended December 31, 2021, no grants were issued under any other scheme. The expected volatility inputs for the years ended December 31, 2022 and 2021 reflect the assumption that the historical volatility over a period similar to the life of the options is indicative of future trends.

Related party disclosures

Related party disclosures	12 Months Ended
	Dec. 31, 2022
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Related party disclosures	27. Related party disclosures Compensation of key management personnel of the Company The remuneration of key management personnel of the Company is set out below in aggregate: Year ended December 31, 2022 2021 2020 £’000s £’000s £’000s Short-term benefits 3,699 4,018 4,479 Post-employment benefits 158 173 144 Share-based payment charge 3,043 2,559 875 Total 6,900 6,750 5,498 The amounts disclosed in the table above are the amounts recognized as an expense during the reporting period related to key management personnel. In 2022, key management personnel of the Company consisted of the executive director (the Chief Executive Officer), non-executive Employee Benefit Trust In 2016 the Company set up an Employee Benefit Trust (“EBT”). The EBT holds ADS’s to satisfy the exercise of options under the Company’s share-based incentive schemes (see ). No funding was loaned to the EBT by the Company during the year ended December 31, 2022 or 2021. During the years ended December share-based schemes (2021: 31,205).

Events after the reporting peri

Events after the reporting period	12 Months Ended
	Dec. 31, 2022
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Events after the reporting period	28. Events after the reporting period On February 10, 2023, the Company amended the Novartis Loan Note, extending the maturity date to February 10, 2025. Pursuant to the amendment and a new warrant instrument, interest accrued to the amendment date was paid in cash and warrants to purchase 2,000,000 ordinary shares at an exercise price of £0.150 per ordinary share were issued and are exercisable until February 10, 2028.

Significant accounting polici_2

Significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2022
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Basis of preparation	Basis of preparation The Company’s consolidated financial statements have been prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board (IASB). The consolidated financial statements are presented in pound sterling (“£”), which is the presentational currency of the Company. The functional currencies of consolidated subsidiaries are pound sterling and US dollars (“$”). All amounts disclosed in the consolidated financial statements and notes have been rounded to the nearest thousand, unless otherwise stated. The financial statements have been prepared on the historical cost basis, except for the revaluation of certain financial instruments that are measured at fair values at the end of each reporting period, as explained in the accounting policies below.
Basis of consolidation	Basis of consolidation The consolidated financial information comprises the financial statements of Mereo BioPharma Group plc and its subsidiaries as at December 31, 2022. Subsidiaries are all entities over which the Company has control. The Company controls an entity when the Company is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power over the entity. Subsidiaries are fully consolidated from the date on which control is transferred to the Company. They are deconsolidated from the date that control ceases. Intercompany transactions, balances and unrealized gains on transactions between subsidiaries are eliminated in preparing the consolidated financial statements. Accounting policies of subsidiaries are consistent with the policies adopted by the Company. The Company has an employee share trust to facilitate share transactions pursuant to employee share schemes. Although the trust is a separate legal entity from the Company, it is consolidated into the Company’s results in accordance with the IFRS 10 rules on special purpose vehicles. The Company is deemed to control the trust principally because the trust cannot operate without the funding the Company provides.
Segmental information	Segmental information The Company has one operating segment. The Chief Operating Decision Maker (“CODM”) is the Chief Executive Officer. The Company has a single portfolio of product candidates, with only direct research and development expenses monitored at a product candidate level. The CODM makes decisions over resource allocation at an overall portfolio level and the Company’s financing is managed and monitored on a consolidated basis. Non-current assets held by the Company are located in the United Kingdom and United States. As at December 31, 2022, less than
Going concern	Going concern The going concern basis has been applied in these consolidated financial statements as the Company has adequate resources to meet its liabilities as they fall due for the foreseeable future and at least 12 months from the issuance date of these consolidated financial statements. The Company expects to incur significant operating losses for the foreseeable future as it continues its research and development efforts, seeks to obtain regulatory approval of its product candidates and pursues any future product candidates the Company may develop. Until such time as the Company can generate significant revenue from product sales, or other commercial revenues, if ever, or through licensing and/or collaboration agreements for its rare disease or oncology product candidates, the Company will seek to finance its operations through a combination of public or private equity or debt financings or other non-dilutive
Revenue	a) Revenue The Company’s ordinary business activities are the development of product candidates to key clinical milestones and either strategically partnering them or further developing such product candidates through regulatory approval and potentially commercialization. The Company may enter into a range of different agreements with third parties, including but not limited to: (i) licensing agreements where the global rights to a product candidate are licensed to a partner; and (ii) collaboration agreements where rights to a product candidate are licensed to a partner but the Company retains certain rights, for example to further develop or commercialize the product candidate in specified geographical territories. Under both licensing and collaboration agreements, rights to product candidates are provided to a partner typically in exchange for consideration in the form of upfront payments and/or development, regulatory, commercial or other similar milestones, and royalties on commercial sales, should regulatory approval be obtained for the product candidates. Where the Company has performed significant development activities for its product candidates, income from agreements with third parties are considered to be proceeds derived from the Company’s ordinary activities and therefore represent revenue within the scope of IFRS 15, Revenue from Contracts with Customers. Revenue includes income from licensing and collaboration agreements. Consideration received up front is recognized at the point in time in which the right to use an intangible asset is transferred and further payments received are recognized upon the achievement of specified development, regulatory, commercial or other similar milestones. For agreements with a right to access an intangible asset, revenue is recognized over time, typically on a straight-line basis over the life of the license or collaboration agreement. When there are other performance obligations in such agreements, the consideration is allocated using the residual approach and recognized when the performance obligations are satisfied. Income from development, regulatory, commercial or similar milestones is recognized when considered highly probable that a significant reversal will not occur. Timing of the recognition of such milestones are considered to be a key judgment, as they are often dependent on third parties. In general, for milestones which are subject to the decisions of third parties (e.g. the acceptance or approval of a filing by a regulatory authority), the Company recognizes milestone income when the decision occurs. The Company does not currently have any approved product candidates. Accordingly, no commercial sales revenue was generated during the year. Intangible assets out-licensed out-licensed.
Research and development (R&D) expenses	b) Research and development (R&D) expenses Expenditure on product development is capitalized as an intangible asset and amortized over the expected useful economic life of the product candidate concerned. Capitalization commences from the point at which technical feasibility and commercial viability of the product candidate can be demonstrated and the Company is satisfied that it is probable that future economic benefits will result from the product candidate once completed. Capitalization ceases when the product candidate receives regulatory approval for launch. No such costs have been capitalized to date. Expenditure on R&D activities that do not meet the criteria for capitalization, including ongoing costs associated with acquired intellectual property rights and intellectual property rights generated internally by the Company, is recognized in the consolidated statement of comprehensive (loss)/income as incurred. Intellectual property and in-process
Taxation	c) Taxation Tax expense recognized in the consolidated statement of comprehensive (loss)/income comprises the sum of deferred tax and current tax not recognized in other comprehensive income or directly in equity. Current income tax Current income tax assets and liabilities are measured at the amount expected to be recovered from or paid to the taxation authorities that are unpaid at the reporting date. Current tax is payable on taxable profit, which differs from profit or loss in the consolidated financial statements. Calculation of current tax is based on tax rates and tax laws that have been enacted, or substantively enacted, by the end of the reporting period in the jurisdictions in which the Company operates. Amounts receivable in respect of research and development tax credits are recognized in the consolidated financial statements provided there is sufficient evidence that the amounts are recoverable. These credits are recognized within income tax in the consolidated statement of comprehensive (loss)/income. A provision is recognized for matters in which the tax determination is uncertain but it is considered probable that there will be a future outflow of funds to a tax authority. The provisions are measured at the best estimate of the amount expected to become payable. Deferred tax Deferred tax is provided using the liability method on temporary differences between the tax bases of assets and liabilities and their carrying amounts for financial reporting purposes at the reporting date. Deferred income tax assets are recognized for all deductible temporary differences, carry-forward of unused tax credits and unused tax losses, to the extent that it is probable that taxable profit will be available against which the deductible temporary differences and the carry-forward of unused tax credits and unused tax losses can be utilized. The carrying amount of deferred income tax assets is reviewed at the end of each reporting period and reduced to the extent that it is no longer probable that sufficient taxable profit will be available to allow all or part of the deferred income tax asset to be utilized. Unrecognized deferred income tax assets are reassessed at the end of each reporting period and are recognized to the extent that it has become probable that future taxable profit will allow the deferred tax assets to be recovered. Deferred tax assets and liabilities are measured on an undiscounted basis at the tax rates that are expected to apply in the year when the asset or liability is realized, based on tax rates (and tax laws) enacted or substantively enacted at the end of the reporting period. Deferred tax assets and liabilities are offset when there is a legally enforceable right to set off current tax assets against current tax liabilities and when they relate to income taxes levied by the same taxation authority and the Company intends to settle its current tax assets and liabilities on a net basis.
Foreign currencies	d) Foreign currencies Items included in the consolidated financial statements are measured using the currency of the primary economic environment in which the entity operates (“the functional currency”). The consolidated financial statements are presented in pound sterling (“£”), which is the presentational currency of the Company. The functional currencies of consolidated subsidiaries are pound sterling and US dollars (“$”). Transactions in foreign currencies are initially recorded by the Company at the rate prevailing on the date the transaction first qualifies for recognition. Differences arising on settlement or translation of monetary items as well as gains or losses on the re translation of foreign currency balances at the period-end are recognized in the consolidated statement of comprehensive (loss )/income. The results and financial position of subsidiaries that have a functional currency different from the presentational currency of the Company are translated into the presentational currency (pound sterling). The assets and liabilities of such entities are translated into pound sterling at the rate of exchange prevailing at the balance sheet date. Income and expenses are translated at the average rate for the period, which approximates the exchange rates at the dates of the transactions. Fair value adjustments arising on acquisition of such entities are treated as assets and liabilities of the relevant entity and translated into pound sterling at the closing rate. The exchange differences arising on translation for consolidation are recognized in other comprehensive (loss)/income.
Property, plant and equipment	e) Property, plant and equipment Property, plant and equipment is stated at cost, net of accumulated depreciation and accumulated impairment losses, if any. Such cost includes the cost of replacing part of the plant and equipment if the recognition criteria are met. All other repair and maintenance costs are recognized in profit or loss as incurred. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Useful lives of various property, plant and equipment are as follows: • Leasehold improvements shorter of lease term or ten years • Office equipment five years • IT equipment three years Property, plant and equipment is derecognized upon disposal or when no future economic benefits are expected from its use or disposal. Any gain or loss arising on derecognition of the asset (calculated as the difference between the net disposal proceeds and the carrying amount of the asset) is included in the consolidated statement of comprehensive (loss)/income when the asset is derecognized. The residual values, useful lives and methods of depreciation of property, plant and equipment are reviewed annually and adjusted prospectively, if appropriate.
Business combinations	f) Business combinations Business combinations are accounted for using the acquisition method of accounting. At the date of acquisition, the Company initially recognizes the fair value of the identifiable assets acquired, the liabilities assumed and any non-controlling The consideration transferred is measured at fair value at the date of acquisition. The excess of the consideration transferred over the fair value of net identifiable assets of the business acquired is recorded as goodwill, unless the amount of consideration transferred is less than the fair value of net identifiable assets of the business acquired in which case the difference is recognized directly in the consolidated statement of comprehensive (loss)/income as a bargain purchase. A valuation is performed of assets and liabilities assumed on each acquisition accounted for as a business combination based on the best estimate of fair value. Where the settlement of any part of cash consideration is deferred, the amounts payable in the future are discounted to their present value. Contingent consideration is classified either as equity or a financial liability and is recognized at fair value on the acquisition date. Amounts classified as a financial liability are subsequently remeasured to fair value in accordance with IFRS 9 (Financial Instruments), with changes in fair value recognized in the consolidated statement of comprehensive (loss)/income as an administrative expense. Directly attributable acquisition-related costs are expensed as incurred within the consolidated statement of comprehensive (loss)/income.
Leases	g) Leases Effective January 1, 2019, the Company adopted IFRS 16 (Leases) using the modified retrospective approach. The Company assesses whether a contract is, or contains, a lease at inception of the contract. The Company recognizes a right-of-use The lease liability is initially measured at the present value of the lease payments that are not paid at the commencement date, discounted using the rate implicit in the lease. If this rate cannot be readily determined, the Company uses its incremental borrowing rate. Lease payments included in the measurement of the lease liability comprise of fixed lease payments, less any lease incentives receivable. The lease liability is subsequently measured by increasing the carrying amount to reflect interest on the lease liability (using the effective interest method) and by reducing the carrying amount to reflect the lease payments made. The Company remeasures the lease liability (and makes a corresponding adjustment to the related right-of-use The right-of-use The right-of-use Right-of-use • Right-of-use six • Right-of-use one When the Company is an intermediate lessor, it accounts for the head lease and the sub-lease sub-lease right-of-use
Intangible assets	h) Intangible assets Intangible assets are initially recorded at cost which has been determined as the fair value of the consideration paid and payable. Assets that have been acquired through a business combination are initially recorded at fair value. The fair value of consideration is regularly reviewed based on the probability of achieving contractual milestones. Refer to policy on provision for deferred cash consideration below. Where the consideration paid or payable is in shares, the cost is measured in accordance with IFRS 2 (Share Based Payments). Intangible assets that are not yet available for use are reviewed for impairment at each reporting date by allocating the assets to the cash-generating units to which they relate. The estimated useful life is the lower of the legal duration and economic useful life. The estimated useful lives of intangible assets are reviewed at least annually. Intangible assets are amortized from the date they are available for commercial use. No amortization has been recognized to date. An intangible asset is derecognized on disposal, or when no future economic benefits are expected from use or disposal. Gains or losses arising from derecognition of an intangible asset, measured as the difference between the net disposal proceeds and the carrying amount of the asset, are recognized in profit or loss when the asset is derecognized.
Financial instruments	i) Financial instruments Financial assets and liabilities are recognized in the consolidated balance sheet only when the Company becomes party to the contractual provisions of the instrument. Financial assets On initial recognition, a financial asset is classified into one of three primary measurement categories: • Amortized cost; • Fair value through other comprehensive income (“FVOCI”); or • Fair value through profit or loss (“FVTPL”). The initial classification into a primary measurement category depends on the nature and purpose of the financial asset. For short-term investments, interest income and impairment gains or losses are recognized directly in the consolidated statement of comprehensive income. The difference between cumulative fair value gains or losses and the cumulative amounts recognized in the consolidated statement of comprehensive (loss)/income is recognized in other comprehensive income until derecognition, when the amounts in other comprehensive income are reclassified to the consolidated statement of comprehensive (loss)/income. Classification as debt or equity Debt and equity instruments are classified as either financial liabilities or as equity in accordance with the substance of the contractual arrangements and the definitions of a financial liability and an equity instrument. Embedded derivatives An embedded derivative is a component of a hybrid contract that also includes a non-derivative Convertible loan notes Convertible loan notes are regarded as compound instruments consisting of a liability component and an equity component. At the date of issue, the fair value of the liability component is estimated using a discount rate for an equivalent liability without the conversion feature. This amount is recorded as a liability on an amortized cost basis using the effective interest method until extinguished upon conversion or at the instrument’s maturity date. The difference between the proceeds from the issue of the convertible loan note and the fair value assigned to the liability component is included in equity and not subsequently remeasured. Upon conversion, the amount initially recognized in “Other capital reserves” will be transferred to “Share premium.” Financial liabilities All financial liabilities are measured subsequently at amortized cost using the effective interest method or at FVTPL. Borrowings (including interest-bearing loans) are initially recognized at fair value, net of transaction costs incurred. Borrowings are subsequently measured at amortized cost. Any difference between the proceeds (net of transaction costs) and the redemption amount is recognized in profit or loss over the period of the borrowings using the effective interest method. Under the effective interest method, amortization is included as a finance cost in the consolidated statement of comprehensive (loss)/income. Non-substantial Borrowings are derecognized from the balance sheet when the obligation specified in the contract is discharged, cancelled or expired. The warrant instruments are recorded at fair value, with changes in the fair value recognized in the consolidated statement of comprehensive (loss)/income, where the terms of the warrant instruments allow for cashless exercise.
Fair value measurement	j) Fair value measurement Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value measurement is based on the presumption that the transaction to sell the asset or transfer the liability takes place either: • In the principal market for the asset or liability; or • In the absence of a principal market, in the most advantageous market for the asset or liability. The principal or the most advantageous market must be accessible by the Company. The fair value of an asset or a liability is measured using the assumptions that market participants would use when pricing the asset or liability, assuming that market participants act in their economic best interest. The Company uses valuation techniques that are appropriate in the circumstances and for which sufficient data are available to measure fair value, maximizing the use of relevant observable inputs and minimizing the use of unobservable inputs. All assets and liabilities for which fair value is measured or disclosed in the consolidated financial statements are categorized within the fair value hierarchy, described as follows, based on the lowest level input that is significant to the fair value measurement as a whole: • Level 1 — quoted (unadjusted) market prices in active markets for identical assets or liabilities. • Level 2 — valuation techniques for which the lowest level input that is significant to the fair value measurement is directly or indirectly observable. • Level 3 — valuation techniques for which the lowest level input that is significant to the fair value measurement is unobservable. For assets and liabilities that are recognized in the consolidated financial statements on a recurring basis, the Company determines whether transfers have occurred between levels in the hierarchy by reassessing categorization (based on the lowest level input that is significant to the fair value measurement as a whole) at the end of each reporting period.
Impairment of non-financial assets	k) Impairment of non-financial Further disclosures relating to impairment of non-financial • Disclosures for significant assumptions Note 3 • Property, plant and equipment Note 12 • Intangible assets not yet available for use Notes 13 and 14 At each reporting date, the Company assesses whether there is any indication that an asset may be impaired. If any such indication exists, or when annual impairment testing for an asset is required, the Company estimates the asset’s recoverable amount. An asset’s recoverable amount is the higher of an asset’s or cash-generating unit’s fair value less costs of disposal and its value in use. The recoverable amount is determined for an individual asset, unless the asset does not generate cash inflows that are largely independent of those from other assets or groups of assets. When the carrying amount of an asset or cash-generating unit exceeds its recoverable amount, the asset is considered impaired and is written down to its recoverable amount. In assessing value in use, the estimated future cash flows are discounted to their present value using a pre-tax Impairment losses are recognized in the consolidated statement of comprehensive (loss)/income in expense categories consistent with the function of the impaired asset. An assessment is made at each reporting date to determine whether there is an indication that previously recognized impairment losses no longer exist or have decreased. If such indication exists, the Company estimates the asset’s or cash-generating unit’s recoverable amount. A previously recognized impairment loss is reversed only if there has been a change in the assumptions used to determine the asset’s recoverable amount since the last impairment loss was recognized. The reversal is limited so that the carrying amount of the asset does not exceed its recoverable amount, nor exceed the carrying amount that would have been determined, net of depreciation, had no impairment loss been recognized for the asset in prior years. Such reversal is recognized in the consolidated statement of comprehensive (loss)/income unless the asset is carried at a revalued amount, in which case the reversal is treated as a revaluation increase.
Cash and short-term deposits	l) Cash and short-term deposits Cash and short-term deposits in the balance sheet comprise cash at banks and on hand along with short-term deposits with a maturity of three months or less, which are subject to an insignificant risk of changes in value.
Provisions	m) Provisions Provisions are recognized when the Company has a present obligation (legal or constructive) as a result of a past event, it is probable that an outflow of resources embodying economic benefits will be required to settle the obligation and a reliable estimate can be made of the amount of the obligation. When the Company expects some or all of a provision to be reimbursed, for example, under an insurance contract, the reimbursement is recognized as a separate asset, but only when the reimbursement is virtually certain. The expense relating to a provision is presented in the consolidated statement of comprehensive (loss)/income net of any reimbursement. If the effect of the time value of money is material, provisions are discounted using a current pre-tax Where contingent payments relate to future use of the in-licensed
Provision for deferred cash consideration	n) Provision for deferred cash consideration Provision for deferred cash consideration consists of future payments which are contractually committed but not yet certain. In respect of products which are not yet approved, such deferred cash consideration excludes potential milestones, royalties or other payments that are deemed to be so uncertain as to be unquantifiable. Deferred cash consideration is recognized as a liability with the amounts calculated as the risk adjusted net present value of anticipated deferred payments. The provision is reviewed at each balance sheet date and adjusted based on the likelihood of contractual milestones being achieved and therefore the deferred payment being settled. Increases in the provision relating to changes in the probability are recognized as an intangible asset. Increases in the provision relating to the unwinding of the time value of money are recognized as a finance expense.
Share-based payments	o) Share-based payments Employees (including executives) and non-executive non-executive Incentives in the form of shares are provided to employees and non-executive see In accordance with IFRS 2 Share-based Payments (“IFRS 2”), charges for these incentives are expensed through the consolidated statement of comprehensive (loss)/income on a straight-line basis over their vesting period, based on the Company’s estimate of shares that will eventually vest. The total amount to be expensed is determined by reference to the fair value of the options or awards at the date they were granted. For LTIP shares, the fair value on grant date excludes the impact of any non-market Equity-settled share-based payment transactions with parties other than employees are measured at the fair value of the goods or services received, except where that fair value cannot be estimated reliably, in which case they are measured at the fair value of the equity instruments granted, measured at the date the entity obtains the goods or the counterparty renders the service. In accordance with IFRS 2, the cancellation of share options is accounted for as an acceleration of the vesting period and therefore any amount unrecognized that would otherwise have been charged in future accounting periods is recognized immediately. When options are forfeited, the accounting expense for any unvested awards is reversed.
Costs of issuing capital	p) Costs of issuing capital Incremental costs incurred and directly attributable to the offering of equity securities are deducted from the related proceeds of the offering. The net amount is recorded as share premium in the period when such shares are issued. Where such expenses are incurred prior to the offering they are recorded in prepayments until the offering completes. Other costs incurred in such offerings are expensed as incurred and included in general and administrative expenses.
Employee Benefit Trust	q) Employee Benefit Trust The Company operates an Employee Benefit Trust (“EBT”), the Mereo BioPharma Group plc Employee Benefit Trust. The EBT holds ADS’s to satisfy the exercise of options under the Company’s share-based incentive schemes ( see Shares held by the EBT are included in the consolidated balance sheet as a reduction in equity.
Pension contribution costs	r) Pension contribution costs Payments to defined contribution retirement benefit plans are recognized as an expense when employees have rendered service entitling them to the contributions.

Significant accounting polici_3

Significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Depreciation Calculated on Straight-Line Basis Over Estimated Useful Lives of Assets	Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Useful lives of various property, plant and equipment are as follows: • Leasehold improvements shorter of lease term or ten years • Office equipment five years • IT equipment three years
Summary of Estimated Useful lives of Right of Use Assets	The right-of-use Right-of-use • Right-of-use six • Right-of-use one

Group information (Tables)

Group information (Tables)	12 Months Ended
	Dec. 31, 2022
Investments accounted for using equity method [abstract]
Summary of Information About Subsidiaries of the Group	The consolidated financial statements of the Company include: Name Principal activities Country of % Equity % Equity Mereo BioPharma 1 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma 2 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma 3 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma 4 Limited Pharmaceutical R&D UK 100 100 Mereo BioPharma Ireland Limited Pharmaceutical R&D Ireland 100 100 Mereo BioPharma 5, Inc. Pharmaceutical R&D US 100 100 Navi Subsidiary, Inc. Pharmaceutical R&D US 100 100 Mereo US Holdings, Inc. Holding Company US 100 100 Mereo BioPharma Group plc Employee Benefit Trust Employee share scheme Jersey — —

(Loss)_profit before tax (Table

(Loss)/profit before tax (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule Of Detailed Information About Profit Before Tax [Abstract]
Summary of Profit before tax is stated after charging	(Loss)/Profit before tax is stated after charging: Year ended December 31, 2022 2021 2020 Fees payable to the Company’s Auditor for the audit of the 371 358 449 Fees payable to the Company’s Auditor for other services: Audit of subsidiary accounts 49 46 49 Audit related assurance services 59 57 318 Gain on modification of lease – – (957 ) Income from sub-lease – – (646 ) Depreciation of right-of-use 583 570 1,531 Depreciation (excluding right-of-use 144 72 68

Employees (Tables)

Employees (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Employee	Total compensation costs for persons employed by the Company (including Directors) during the year was: Year ended December 31, 2022 2021 2020 Included in research and development expenses: Salaries 4,590 4,126 3,046 Social security costs 456 402 397 Pension contributions 78 73 66 Share-based payment expenses 1,083 1,210 446 Included in administrative expenses: Salaries 4,478 3,763 4,832 Social security costs 606 418 681 Pension contributions 124 99 89 Share-based payment expenses 2,779 2,092 1,112 Total 14,194 12,183 10,669
Summary of Compensation Cost For Directors	Total compensation costs for Directors during the year was: Year ended December 31, 2022 2021 2020 Salaries and fees 534 810 1,114 Benefits in kind 9 9 14 Pension contributions 42 58 61 Bonus 226 239 538 Total 811 1,116 1,727

Other income_expenses and adj_2

Other income/expenses and adjustments (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Finance Income	Finance income Year ended December 31, 2022 2021 2020 Bank interest earned 696 1 5 Gain on short-term investments — — 39 Total 696 1 44
Summary of Finance Costs	Finance costs Year ended December 31, 2022 2021 2020 Interest on convertible loan notes (2,660 ) (3,549 ) (2,241 ) Interest on bank loan — — (2,900 ) Interest on lease liabilities (209 ) (227 ) (1,085 ) Discounting of provision on deferred cash consideration (451 ) (225 ) (157 ) Other (41 ) (21 ) — Total (3,361 (4,022 ) (6,383 )
Summary of Changes In The Fair Value Of Financial Instruments	Changes in the fair value of financial instruments Year ended December 31, 2022 2021 2020 Changes in the fair value of warrants – private placement 7,593 39,535 (45,977 ) Changes in the fair value of warrants – bank loan 212 504 (714 ) Changes in the fair value of embedde d — — (63,158 ) Total 7,805 40,039 (109,849 )

Taxation (Tables)

Taxation (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Income Tax Credit	Year ended December 31, 2022 2021 2020 UK corporation tax R&D credit 1,296 — 2,822 Tax credit/(charge) 601 (1,516 ) — Total 1,897 (1,516 ) 2,822
Summary of Reconciliation to the Earnings Loss Per Income Statement	Reconciliation of effective tax rate Year ended December 31, 2022 2021 2020 (Loss)/profit on ordinary activities before income tax (36,093 ) 14,241 (166,450 ) Tax on profit at standard U.K rate of 19% 6,857 (2,706 ) 31,626 Expenses not deductible for income tax purposes (permanent differences) (965 ) (708 ) (13,270 ) Income not taxable 12 78 4 Temporary timing differences — (65 ) — R&D relief uplift 558 1,435 1,214 Losses (unrecognized) (4,810 ) (345 ) (14,479 ) Foreign tax 422 505 184 Differences in overseas tax rates 323 286 261 Derecognition of deferred tax — — (2,686 ) Effects of carryback loss relief (649 ) — — Adjustments in respect of prior years 612 — — Other (463 ) 4 (32 ) Tax credit/(charge) for the year 1,897 (1,516 ) 2,822
Summary of Deferred Tax	The analysis of unrecognized deferred tax is set out below: Year ended December 31, 2022 2021 2020 Losses 47,209 44,683 37,021 Loan relationships 443 73 421 U.S tax credits 12,206 10,557 9,880 R&D capitalization 3,001 — — Fixed assets — — 414 Share options 434 151 55 Other U.S deferred tax — 31 86 Other — — 137 Temporary differences 51 56 18 Net deferred tax asset (unrecognized) 63,344 55,551 48,032
Summary of analysis of recognized deferred tax	The analysis of recognized deferred tax At January 1, Recognized At December 31, Deferred tax liabilities Intangible asset and right-of-use (20 ) (156 ) (176 ) Deferred tax asset Net operating losses and lease liability 20 156 176 Net deferred tax asset/(liability) — — —

Earnings per share (Tables)

Earnings per share (Tables)	12 Months Ended
	Dec. 31, 2022
Earnings per share [abstract]
Summary Of Earnings Per Share	Year ended December 31, 2022 2021 2020 Numerator – Basic earnings per share (£’000s): (Loss)/profit (34,196 ) 12,725 (163,628 ) Denominator – Basic earnings per share: Weighted average number of ordinary shares 603,196,403 527,818,648 338,953,141 (Loss)/profit per share – basic (£) (0.06 ) 0.02 (0.48 ) Numerator – Diluted earnings per share (£’000s): (Loss)/profit (34,196 ) 12,725 (163,628 ) Effect of dilutive ordinary shares — (38,523 ) — Numerator – Diluted earnings per share (34,196 ) (25,798 ) (163,628 ) Denominator – Diluted earnings per share: Number of ordinary shares used for basic earnings per share 603,196,403 527,818,648 338,953,141 Weighted average effect of dilutive ordinary shares — 27,457,163 — Weighted average number of diluted ordinary shares outstanding 603,196,403 555,275,811 338,953,141 Loss per share – diluted (£) (0.06 ) (0.05 ) (0.48 )

Property, plant and equipment (

Property, plant and equipment (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Property, Plant and Equipment	Right-of-use Right-of-use Leasehold Office IT Total Cost of valuation At January 1, 2022 2,903 295 557 173 180 4,108 Additions — — — 7 3 10 Disposals (451 ) (300 ) — (16 ) (10 ) (777 ) Currency translation effects 13 5 — — — 18 At December 31, 2022 2,465 — 557 164 173 3,359 Depreciation At January 1, 2022 (1,025 ) (231 ) (124 ) (69 ) (129 ) (1,578 ) Disposals 451 300 — 16 10 777 Depreciation for the year (514 ) (69 ) (95 ) (23 ) (26 ) (727 ) At December 31, 2022 (1,088 ) — (219 ) (76 ) (145 ) (1,528 ) Net book value At January 1, 2022 1,878 64 433 104 51 2,530 At December 31, 2022 1,377 — 338 88 28 1,831 Right-of-use Right-of-use Leasehold Office IT Total Cost of valuation At January 1, 2021 1,848 1,169 164 71 132 3,384 Additions 923 — 393 109 48 1,473 Lease modification 133 30 — — — 163 Disposals — (868 ) — (7 ) — (875 ) Currency translation effects (1 ) (36 ) — — — (37 ) At December 31, 2021 2,903 295 557 173 180 4,108 Depreciation At January 1, 2021 (531 ) (1,023 ) (85 ) (65 ) (107 ) (1,811 ) Disposals — 868 — 7 — 874 Depreciation for the year (494 ) (76 ) (39 ) (11 ) (22 ) (642 ) At December 31, 2021 (1,025 ) (231 ) (124 ) (69 ) (129 ) (1,578 ) Net book value At January 1, 2021 1,318 146 79 6 25 1,573 At December 31, 2021 1,878 64 433 104 51 2,530
Summary of the maturity of lease liabilities	The maturity of lease liabilities as of December 31, 2022 are as follows: Within 1 year Between 1 and 3 years Between Over 5 Total £’000s £’000s £’000s £’000s £’000s Maturity of lease liabilities 466 1,072 150 — 1,688

Intangible assets (Tables)

Intangible assets (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Detailed Information about Intangible Assets	Acquired £’000s Cost At January 1, 2021 33,005 At December 31, 2021 33,005 At December 31, 2022 33,005 Revisions to estimated value At January 1, 2021 (1,357 ) Revision to estimated value 2,373 Out-license (9,457 ) At December 31, 2021 (8,441 ) Revision to estimated value (448 ) At December 31, 2022 (8,889 ) Net book value At December 31, 2021 24,564 At December 31, 2022 24,116

Impairment testing of acquire_2

Impairment testing of acquired development programs not yet available for use (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Carrying Amount of Acquired Development Programs	Acquired development programs not yet available for use are assessed annually for impairment. The carrying amount of acquired development programs is as follows: December 31, 2022 2021 £’000s £’000s BPS-804 /UX143 2,159 2,159 MPH-966 7,760 8,208 BGS-649 9,886 9,886 BCT-197 4,311 4,311 Total 24,116 24,564

Other receivables (Tables)

Other receivables (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Other Receivables	December 31, 2022 2021 £’000s £’000s Lease deposits 293 408 VAT recoverable 362 387 Other 107 624 Total 762 1,419

Cash and short-term deposits (T

Cash and short-term deposits (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Cash and Short-term Deposits	December 31, 2022 2021 £’000s £’000s Cash 5,230 93,727 Short-term deposits 51,104 569 Total 56,334 94,296

Trade and other payables (Table

Trade and other payables (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Trade and Other Payables	December 31, 2022 2021 £’000s £’000s Trade payables 2,886 2,285 Social security and other taxes 167 190 Other payables 25 24 Total 3,078 2,499

Provisions (Tables)

Provisions (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Provisions	December 31, 2022 2021 £’000s £’000s Social security contribution on vested share options 9 — Provision for deferred cash consideration 4,634 4,123 Restructuring 179 — Total 4,822 4,123 Current 4,822 2,803 Non-current — 1,320
Summary of Social Security Contributions on Share Options	Social security Deferred cash Restructuring At January 1, 2021 109 1,525 — Arising/(released) during (109 ) — — Increase in provision due — 225 — Increase in provision due — 2,373 — At December 31, 2021 — 4,123 — Arising/(released) during 9 — 179 Increase in provision due — 451 — Increase in provision due — 508 — Decrease — (448 ) — At December 31, 2022 9 4,634 179

Warrant liability (Tables)

Warrant liability (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Warrant Liability	December 31, 2022 2021 £’000s £’000s At January 1 8,336 50,775 Issued during the year — — Settled during the year — (2,400 ) Fair value changes during the year (7,805 ) (40,039 ) At December 31 531 8,336
Summary of Weighted Average Inputs to the Models Used for the Fair Value of Warrants Granted	The following table lists the weighted average inputs to the models used for the fair value of warrants: December 31, 2022 2021 Expected volatility (%) 95 75 Risk-free interest rate (%) 3.99 0.9 Expected life of warrants (years) 0.5 1.5 Market price of ADS ($) 0.75 1.60 Model used Black-Scholes Black-Scholes

Convertible loan notes (Tables)

Convertible loan notes (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Interest-bearing Loans and Borrowings	December 31, 2022 2021 £’000s £’000s Novartis Loan Note 4,449 3,771 Loan Notes – private placement 6,636 10,613 Total 11,085 14,384 Current 11,085 — Non-current — 14,384
Disclosure of movements in the carrying value of the liability component of the loan notes	The movements in the carrying value of the liability component of the Loan Notes is included in the table below. Refer to Note 22 for details of Loan Notes converted to equity. December 31, 2022 2021 £’000s £’000s January 1 10,613 12,946 Issued — — Interest charge 1,981 2,974 Converted to equity (5,958 ) (5,307 ) December 31 6,636 10,613

Issued capital and reserves (Ta

Issued capital and reserves (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Detailed Information of Ordinary Share Capital	Ordinary Ordinary Share Number £’000s £’000s As at January 1, 2020 97,959,622 294 121,684 Issued on February 11, 2020 14,295,520 43 2,511 Issued on February 20, 2020 12,252,715 37 2,267 Issued on June 4, 2020 89,144,630 267 15,244 Issued on June 30, 2020 125,061,475 375 21,386 Issued on December 23, 2020 239,179 1 — Transaction costs for issued share capital — — (1,307 ) As at December 31, 2020 338,953,141 1,017 161,785 Issued during the year 245,955,098 738 85,909 Transaction costs for issued share capital — — (234 ) As at December 31, 2021 584,908,239 1,755 247,460 Issued during the year 40,020,280 120 6,843 As at December 31, 2022 624,928,519 1,875 254,303
Summary of Other Capital Reserves	Other capital reserves Share- Equity Other Merger Other Total At January 1, 2020 18,285 — 44 40,818 — 59,147 Share-based payments expense during the year 1,558 — — — — 1,558 Novartis convertible loan note instrument and warrants — 1,084 — — — 1,084 Conversion of Loan Notes — — — — 33,104 33,104 Reclassification of the embedded derivative — 33,481 — — — 33,481 At December 31, 2020 19,843 34,565 44 40,818 33,104 128,374 Share-based payments expense during the year 3,302 — — — — 3,302 Share options exercised (119 ) — — — — (119 ) Conversion of Loan Notes — (1,722 ) — — — (1,722 ) At December 31, 2021 23,026 32,843 44 40,818 33,104 129,835 Share-based payments expense during the year 3,862 — — — — 3,862 Share options exercised (82 ) — — — — (82 ) Issuance of warrants — — 70 — — 70 Conversion of Loan Notes — (1,005 ) — — — (1,005 ) At December 31, 2022 26,806 31,838 114 40,818 33,104 132,680
Summary of Accumulated Loss	Year ended December 31, 2022 2021 2020 Other reserves 7,401 7,401 5,001 Accumulated losses (331,164 ) (296,968 ) (309,693 )

Changes in liabilities arisin_2

Changes in liabilities arising from financing activities (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Changes in Liabilities Arising from Financing Activities	Lease Novartis Warrant Deferred Loan Other Total Carrying value at January 1, 2021 1,794 3,196 50,775 1,525 12,946 62 70,298 Financing cash flows (692 ) — — — — — (692 ) Non-cash Settled during the year — — (2,400 ) — (5,307 ) — (7,707 ) Interest expense 230 575 — 206 2,974 18 4,003 Lease addition 910 — — — — — 910 Lease modification 163 — — — — — 163 Changes in fair value — — (40,039 ) 2,373 — — (37,666 ) Changes in foreign exchange (29 ) — — 19 — — (10 ) Carrying value at December 31, 2021 2,376 3,771 8,336 4,123 10,613 80 29,299 Financing cash flows (937 ) — — — — 153 (784 ) Non-cash Settled during the year — — — — (5,958 ) — (5,958 ) Interest expense 209 678 — 451 1,981 19 3,338 Issuance of warrants — — — — — (70 ) (70 ) Changes in fair value — — (7,805 ) (448 ) — — (8,253 ) Changes in foreign exchange 40 — — 508 — — 548 Carrying value at December 31, 2022 1,688 4,449 531 4,634 6,636 182 18,120

Financial and capital risk ma_2

Financial and capital risk management and fair value measurement (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary of Fair Value Hierarchy	Liabilities measured at fair Date of valuation Total Quoted prices Significant Significant £’000s £’000s £’000s £’000s Provision for deferred consideration (Note 18) December 31, 2022 4,634 — — 4,634 Warrant liability (Note 20) December 31, 2022 531 — 129 402 Liabilities measured at fair Date of valuation Total Quoted prices Significant Significant £’000s £’000s £’000s £’000s Provision for deferred consideration (Note 18) December 31, 2021 4,123 — — 4,123 Warrant liability (Note 20) December 31, 2021 8,336 — 341 7,995
Summary of the Changes in Level 3	The following table presents the changes in Level 3 items for the years Provision for Warrant £’000s £’000s January 1, 2021 1,525 49,930 Settled during the year — (2,400 ) Unwinding of the time value of money (recognized as a finance cost) 225 — Change in estimate relating to probabilities (revision to intangible asset, 2,373 — Change in fair value — (39,535 ) December 31, 2021 4,123 7,995 Unwinding of the time value of money (recognized as a finance cost) 451 — Change in foreign exchange rates 508 — Change in estimate relating to probabilities (revision to intangible asset, (448 ) — Change in fair value — (7,593 ) December 31, 2022 4,634 402
Summary of Changes In Significant Unobservable Inputs Under Valuation Model Used In Level Fair Value Measurement	The significant unobservable inputs used in the fair value measurements categorized within Level 3 of the fair value hierarchy, together with a quantitative sensitivity analysis as at December 31, 2022 and 2021 are as follows: Valuation Significant unobservable inputs Input range Sensitivity of the input to fair value Provision for deferred cash consideration Discounted cash flow WACC 2022: 15% 1% increase/decrease would result in a decrease/increase in fair value by £25,000 WACC 2021: 12% 1% increase/decrease would result in a decrease/increase in fair value by £31,000 Probability of success 2022: 40.6 %- 81.2% 10% increase/decrease would result in an increase/decrease in fair value by £0.6 million Probability of success 2021: 40.6% - 81.2% 10% increase/decrease would result in an increase/decrease in fair value by £0.5 million Contingent consideration liability Discounted cash flow Ongoing uncertainty in the clinical development of the Navi product Total potential payments future payments relating to the contingent consideration liability on a gross, undiscounted basis are approximately $80 million. Regulatory approval and commercialization risks Sensitivity of the input to fair value is primarily driven by uncertainty in the clinical development of the Navi product. Future potential payments under the CVR arrangement are contingent on i) future development milestones and ii) future sales of the Navi product, following regulatory approval and commercialization. In January 2020, the Company entered into the license agreement as detailed in Note 13. Although pursuant to the license agreement the Company is entitled to additional payments of up to $302 million, there continues to be significant uncertainty in respect of any milestone and royalty payments under the license agreement. Warrant liability related to the private placement Black-Scholes model Expected volatility 2022: 95.5% Volatility was estimated by reference to the 0.4 year historical volatility of the historical share price of the Company, matching the maturity of the instrument. If the volatility is decreased to 91.8% based on 3-month historical volatility, the carrying value of the warrants as of December 31, 202 2 Expected volatility 2021: 75.1% Volatility was estimated by reference to the 1.4 years historical volatility of the historical share price of the Company, matching the maturity of the instrument. If the volatility is decreased to 67.4% based on 1-year historical volatility, the carrying value of the warrants as of December 31, 2021 would decrease to £6.7 million.
Summary of Maturity Profile of Financial Liabilities Based on Contractual Undiscounted Payments	The table below summarizes the maturity profile of the Company’s financial liabilities based on contractual undiscounted payments at December 31, 2022: Within Between Between Over 5 years Total £’000s £’000s £’000s £’000s £’000s Leases 611 1,222 152 — 1,985 Trade and other payables 3,078 — — — 3,078 Accruals 4,491 — — — 4,491
Detailed Information About Cash And Cash Equivalents By Currency Type	The table below shows analysis of the pound sterling equivalent of period-end December 31, 2022 2021 £’000s £’000s Pound sterling 52,812 92,104 U.S. dollars 2,484 2,018 Euro 1,029 165 Swiss francs 9 9 Total 56,334 94,296
Detailed on Information About Gain Loss On Foreign Currency Translaction Recognized In Income Statement	The table below shows those transactional exposures that give rise to net currency gains and losses recognized in the consolidated statement of comprehensive income/(loss). Such exposures comprise the net monetary assets and monetary liabilities of the Company that are not denominated in the functional currency of the relevant subsidiary. As at December 31, these exposures were as follows: December 31, 2022 2021 Net foreign currency assets/(liabilities) £ ’000s £ ’000s U.S. dollars 872 920 Euro 768 (142 ) Swiss francs (179 ) 9 Total 1,461 787
Summary of sensitivity analyis of currency movement	The following table illustrates the sensitivity to a 10% weakening or strengthening in the period-end dollar and the Euro against pound sterling: December 31, 2022 U.S. dollar Euro £’000s £’000s Loss before tax (79 ) (70 ) Equity (79 ) (70 ) December 31, 2021 U.S. dollar Euro £’000s £’000s Profit before tax (84 ) 13 Equity (84 ) 13
Summary of Financial instruments by category	Fair value December 31, Amortized cost December 31, 2022 2021 2022 2021 Financial assets £ ’000s £ ’000s £ ’000s £ ’000s Cash and short-term deposits — — 56,334 94,296 Other receivables — — 400 1,032 Total financial assets — — 56,734 95,328 Financial liabilities Provisions 4,634 4,123 187 — Convertible loan notes — — 11,086 14,384 Warrant liability 531 8,336 — — Trade and other payables — — 2,911 2,309 Accruals — — 4,491 3,826 Lease liability — — 1,688 2,376 Total financial liabilities 5,165 12,459 20,363 22,895

Share-based payments (Tables)

Share-based payments (Tables)	12 Months Ended
	Dec. 31, 2022
Statement [LineItems]
Summary of Share-based Payments	The charge for share-based payments arises across the following schemes: Year ended 2022 2021 2020 £’000s £’000s £’000s 2019 Equity Incentive Plan 3,149 2,860 922 2019 NED Equity Incentive Plan 713 499 167 2015 Plan — — 3 Mereo BioPharma Group plc Share Option Plan — 68 376 Long Term Incentive Plan — (125 ) 90 Total 3,862 3,302 1,558
Summary of Number and Weighted Average Exercise Prices (WAEP) of, and Movements in, Options	The following table illustrates the number and weighted average exercise prices (WAEP) of, and movements in, options for the 2019 EIP and 2019 NED EIP and the number of Deferred RSUs for the 2019 NED EIP during the year-ended December 31, 2022: 2019 EIP 2019 NED EIP Options ADS Number WAEP $ Deferred Number Options ADS Number WAEP $ Outstanding at January 1, 2022 3,943,702 2.88 — 421,791 2.90 Granted during the year 4,126,400 1.38 386,144 535,488 1.22 Cancelled during the year (1,164,197 ) 1.83 (42,104 ) (42,192 ) 1.01 Forfeited during the year (48,044 ) 3.97 — — Exercised during the year — — — — Outstanding at December 31, 6,857,861 2.15 344,040 915,087 2.00 Exercisable at December 31, 2022 2,082,027 2.95 — 832,584 2.09 The following table illustrates the number and weighted average exercise prices (WAEP) of, and movements in, options for the 2019 EIP and 2019 NED EIP during the year-ended December 31, 2021: 2019 EIP 2019 NED EIP Options Number WAEP $ Options Number WAEP $ Outstanding at January 1, 2021 1,567,873 2.94 149,416 3.06 Granted during the year 2,696,960 2.83 296,000 2.81 Cancelled during the year (253,277 ) 2.66 (23,625 ) 2.72 Forfeited during the year (28,521 ) 5.37 — — Exercised during the year (39,333 ) 2.11 — — Outstanding at December 31, 2021 3,943,702 2.88 421,791 2.90 Exercisable at December 31, 2021 727,698 3.16 386,623 2.91
Summary of Weighted Average Inputs to the Models Used for the Fair Value of Share Options Granted	The following table includes the weighted average inputs to the models used for the fair value of share options granted during the year ended December 31, 2022: 2019 EIP 2019 NED EIP Expected volatility (%) 96 96 Risk-free interest rate (%) 1.83 1.96 Expected life of share options (years) 10 10 Market price of ADSs ($) 1.38 1.22 Model used Black-scholes Black-scholes During the year ended December 31, 2022, no grants of share options were issued under any other scheme. The following table includes the weighted average inputs to the models used for the fair value of share options granted during the year ended December 31, 2021: 2019 EIP 2019 NED EIP Expected volatility (%) 97 98 Risk-free interest rate (%) 1.15 1.09 Expected life of share options (years) 10 10 Market price of ADSs ($) 2.83 2.81 Model used Black-scholes Black-scholes During the year ended December 31, 2021, no grants were issued under any other scheme. The expected volatility inputs for the years ended December 31, 2022 and 2021 reflect the assumption that the historical volatility over a period similar to the life of the options is indicative of future trends.
2015 Plan [member]
Statement [LineItems]
Summary of Number and Weighted Average Exercise Prices (WAEP) of, and Movements in, Options	2022 2021 Options Number WAEP £ Options Number WAEP £ Outstanding at January 1 8,297,694 1.31 8,923,600 1.32 Forfeited during the year (423,164 ) 1.55 (625,906 ) 1.29 Outstanding at December 31 7,874,530 1.46 8,297,694 1.31 Exercisable at December 31 7,874,530 1.46 8,297,694 1.31
Mereo BioPharma Group plc Share Option Plan [member]
Statement [LineItems]
Summary of Number and Weighted Average Exercise Prices (WAEP) of, and Movements in, Options	The following table illustrates the number and weighted average exercise prices (WAEP) of, and movements in, options for the Option Plan during the year: 2022 2021 Options Number WAEP £ Options Number WAEP £ Outstanding at January 1 1,323,965 3.04 1,411,395 3.14 Forfeited during the year (770,805 ) 3.32 (87,430 ) 3.11 Outstanding at December 31 553,160 3.49 1,323,965 3.04 Exercisable at December 31 553,160 3.49 1,323,965 3.04
Long-term incentive plan [member]
Statement [LineItems]
Summary of Number and Movements in Long Term Incentive Plan Options	The fair value calculations do not include any allowance for dividends as the Company has no available profits for distribution. The contractual term of the LTIP options is five years. 2022 Number 2021 Number Outstanding at January 1 — 482,748 Lapsed during the yea r — (482,748 ) Outstanding at December 31 — — Exercisable at December 31 — —

Related party disclosures (Tabl

Related party disclosures (Tables)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Summary Of Compensation of key management personnel of the Group	The remuneration of key management personnel of the Company is set out below in aggregate: Year ended December 31, 2022 2021 2020 £’000s £’000s £’000s Short-term benefits 3,699 4,018 4,479 Post-employment benefits 158 173 144 Share-based payment charge 3,043 2,559 875 Total 6,900 6,750 5,498

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail) - GBP (£) £ in Millions	Dec. 31, 2022	Dec. 31, 2021
OncoMed [Member]
Disclosure of related to geographical location of assets [Line Items]
Acquisition of non-current assets	£ 0.1	£ 0.1

Significant Accounting Polici_5

Significant Accounting Policies - Summary of Depreciation Calculated on Straight-Line Basis Over Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2022
Leasehold improvements [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated useful lives	shorter of lease term or ten years
Office equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated useful lives	5 years
IT equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated useful lives	3 years

Significant Accounting Polici_6

Significant Accounting Policies - Summary of Depreciation Method For Right of Use Assets And Useful Life (Detail)	12 Months Ended
	Dec. 31, 2022
Building [member] | Bottom of range [member]
Statement [line items]
Useful life of right-of-use asset	6 years
Building [member] | Top of range [member]
Statement [line items]
Useful life of right-of-use asset	9 years
Equipment | Bottom of range [member]
Statement [line items]
Useful life of right-of-use asset	1 year
Equipment | Top of range [member]
Statement [line items]
Useful life of right-of-use asset	2 years

Significant judgments, estima_2

Significant judgments, estimates and assumptions - Additional Information (Detail) £ in Millions, $ in Millions	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 GBP (£)
Significant Accounting Judgments Estimates And Assumption [Line Items]
Fair value of the contingent consideration liability	£ 0		£ 0
Potential payments under the CVR arrangement	£ 58.6	$ 80

Group Information - Summary of

Group Information - Summary of Information About Subsidiaries of the Group (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Mereo BioPharma 1 Limited [member]
Disclosure of subsidiaries [line items]
Name	Mereo BioPharma 1 Limited
Principal activities	Pharmaceutical R&D
Country of incorporation	UK
% equity interest	100%	100%
Mereo BioPharma 2 Limited [member]
Disclosure of subsidiaries [line items]
Name	Mereo BioPharma 2 Limited
Principal activities	Pharmaceutical R&D
Country of incorporation	UK
% equity interest	100%	100%
Mereo BioPharma 3 Limited [member]
Disclosure of subsidiaries [line items]
Name	Mereo BioPharma 3 Limited
Principal activities	Pharmaceutical R&D
Country of incorporation	UK
% equity interest	100%	100%
Mereo BioPharma 4 Limited [member]
Disclosure of subsidiaries [line items]
Name	Mereo BioPharma 4 Limited
Principal activities	Pharmaceutical R&D
Country of incorporation	UK
% equity interest	100%	100%
Mereo BioPharma Ireland Limited [member]
Disclosure of subsidiaries [line items]
Name	Mereo BioPharma Ireland Limited
Principal activities	Pharmaceutical R&D
Country of incorporation	Ireland
% equity interest	100%	100%
Mereo BioPharma 5 Inc [Member]
Disclosure of subsidiaries [line items]
Name	Mereo BioPharma 5, Inc.
Principal activities	Pharmaceutical R&D
Country of incorporation	US
% equity interest	100%	100%
Navi Subsidiary Inc [Member]
Disclosure of subsidiaries [line items]
Name	Navi Subsidiary, Inc.
Principal activities	Pharmaceutical R&D
Country of incorporation	US
% equity interest	100%	100%
Mereo US Holdings Inc [member]
Disclosure of subsidiaries [line items]
Name	Mereo US Holdings, Inc.
Principal activities	Holding Company
Country of incorporation	US
% equity interest	100%	100%
Mereo BioPharma Group plc Employee Benefit Trust [member]
Disclosure of subsidiaries [line items]
Name	Mereo BioPharma Group plc Employee Benefit Trust
Principal activities	Employee share scheme
Country of incorporation	Jersey

Revenue - Additional Informatio

Revenue - Additional Information (Detail) £ in Millions, $ in Millions		12 Months Ended
	Jan. 25, 2021 GBP (£)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 USD ($)
Disclosure Of Revenue From Contracts With Customers [Line Items]
Upfront Payment Received	£ 36.5				$ 50
Milestone payment for regulatory and commercial achievements | $			$ 302
Ultragenyx collaboration agreement [Member]
Disclosure Of Revenue From Contracts With Customers [Line Items]
Upfront Payment Received				£ 36.5	50
Milestone payment to ultragenyx collaboration agreement deductions costs				2.4
Milestone payment to ultragenyx collaboraation agreement deductions costs recognised		£ 0.9		1.1
Milestone payment to ultragenyx collaboration agreement deductions costs yet to be recogised		£ 0.3		1.3
Ultragenyx collaboration agreement [Member] | Novartis [member]
Disclosure Of Revenue From Contracts With Customers [Line Items]
Milestone payment for regulatory and commercial achievements				£ 7.2	$ 10

(Loss)_profit before tax - Summ

(Loss)/profit before tax - Summary of information about Profit Before Tax (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Detailed Information About Profit Before Tax [Abstract]
Fees payable to the Company's Auditor for the audit of the consolidated accounts	£ 371	£ 358	£ 449
Fees payable to the Company's Auditor for other services:
Audit of subsidiary accounts	49	46	49
Audit related assurance services	59	57	318
Gain on modification of lease	0	0	(957)
Income from sub-lease	0	0	(646)
Depreciation of right-of-use assets	583	570	1,531
Depreciation (excluding right-of-use assets)	£ 144	£ 72	£ 68

Employees - Summary of Total co

Employees - Summary of Total compensation cost for persons Employed by the Group (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of employee [line items]
Share-based payment expenses	£ 3,862	£ 3,302	£ 1,558
Total	14,194	12,183	10,669
Research and development expenses [member]
Disclosure of employee [line items]
Salaries	4,590	4,126	3,046
Social security costs	456	402	397
Pension contributions	78	73	66
Share-based payment expenses	1,083	1,210	446
Administrative expenses [member]
Disclosure of employee [line items]
Salaries	4,478	3,763	4,832
Social security costs	606	418	681
Pension contributions	124	99	89
Share-based payment expenses	£ 2,779	£ 2,092	£ 1,112

Employees - Summary of Compensa

Employees - Summary of Compensation Cost For Directors (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of employee [line items]
Pension contributions	£ 158	£ 173	£ 144
Total	6,900	6,750	5,498
Directors [member]
Disclosure of employee [line items]
Salaries and fees	534	810	1,114
Benefits in kind	9	9	14
Pension contributions	42	58	61
Bonus	226	239	538
Total	£ 811	£ 1,116	£ 1,727

Other income_expenses and adj_3

Other income/expenses and adjustments - Additional Information (Detail) £ in Thousands, $ in Millions				12 Months Ended
	Feb. 28, 2022 GBP (£)	Feb. 28, 2022 USD ($)	Jan. 25, 2021 GBP (£)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 GBP (£)
Statement [line items]
Upfront Payment Received			£ 36,500				$ 50
Milestone payment for regulatory and commercial achievements | $					$ 302
Finance income				£ 696		£ 1		£ 44
Navi License Agreement [Member] | Mile Stone Achievement [Member]
Statement [line items]
Upfront Payment Received	£ 1,500	$ 2
Milestone payment for regulatory and commercial achievements	700	$ 0.9
Finance income	£ 800

Other income_expenses and adj_4

Other income/expenses and adjustments - Summary of Finance Income (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of Other Income Expenses And Adjustment [Line Items]
Bank interest earned	£ 696	£ 1	£ 5
Gain on short-term investments			39
Total	£ 696	£ 1	£ 44

Other income_expenses and adj_5

Other income/expenses and adjustments - Summary of Finance Charge (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of Other Income Expenses And Adjustment [Line Items]
Interest on convertible loan notes	£ (2,660)	£ (3,549)	£ (2,241)
Interest on bank loan			(2,900)
Interest on lease liabilities	(209)	(227)	(1,085)
Discounting of provision on deferred cash consideration	(451)	(225)	(157)
Other	(41)	(21)
Total	£ (3,361)	£ (4,022)	£ (6,383)

Other income_expenses and adj_6

Other income/expenses and adjustments - Summary of Changes In The Fair Value Of Financial Instruments (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of Changes in the fair value of financial instruments [Line Items]
Gain (Loss) on change in fair value of warrants	£ 7,805	£ 40,039	£ (109,849)
Private placement [Member]
Disclosure of Changes in the fair value of financial instruments [Line Items]
Gain (Loss) on change in fair value of warrants	7,593	39,535	(45,977)
Bank Loan [member]
Disclosure of Changes in the fair value of financial instruments [Line Items]
Gain (Loss) on change in fair value of warrants	£ 212	£ 504	(714)
Embedded Derivative [Member]
Disclosure of Changes in the fair value of financial instruments [Line Items]
Gain (Loss) on change in fair value of warrants			£ (63,158)

Taxation - Summary of Income Ta

Taxation - Summary of Income Tax Credit (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Major components of tax expense (income) [abstract]
UK corporation tax R&D credit	£ 1,296		£ 2,822
Tax credit/(charge)	601	£ (1,516)
Tax credit for the year	£ 1,897	£ (1,516)	£ 2,822

Taxation - Additional Informati

Taxation - Additional Information (Detail) - GBP (£) £ in Thousands		12 Months Ended
	May 24, 2021	Dec. 31, 2022	Dec. 31, 2021
Disclosure of income tax credit [line items]
Description of accumulated tax losses		A deferred tax asset on losses has been recognized up to the level of the deferred tax liability, resulting in a net deferred tax liability of £nil.
Deferred tax liability		£ 0
Other taxes recoverable		614	£ 809
Uncertain tax position off balance sheet		£ 3,100
Uncertain tax position off balance sheet | %		20%
Indefinitely Expired [Member]
Disclosure of income tax credit [line items]
Tax Losses carry forward		£ 67,700
U.K. Tax Authority [Member]
Disclosure of income tax credit [line items]
Standard rate of corporation tax applied to reported loss		19%	19%
Rate at which deferred tax assets and liabilities would be recognized		25%
Tax Losses carry forward		£ 125,800
U.K. Tax Authority [Member] | Top of range [member]
Disclosure of income tax credit [line items]
Description of corporate tax reduction	25
U.K. Tax Authority [Member] | Bottom of range [member]
Disclosure of income tax credit [line items]
Description of corporate tax reduction	19
U.S. Tax Authority [Member]
Disclosure of income tax credit [line items]
Rate at which deferred tax assets and liabilities would be recognized		21%
Tax Losses carry forward		£ 74,600
U.S. Tax Authority [Member] | Expire In 2023 [Member]
Disclosure of income tax credit [line items]
Tax Losses carry forward		£ 6,900
Expiration date		2023
U.S. Tax Authority [Member] | Expire In 2028 [Member]
Disclosure of income tax credit [line items]
Tax Losses carry forward		£ 4,000
Expiration date		2027

Taxation - Summary of Reconcili

Taxation - Summary of Reconciliation to the Earnings Loss Per Income Statement (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Major components of tax expense (income) [abstract]
(Loss)/profit on ordinary activities before income tax	£ (36,093)	£ 14,241	£ (166,450)
Tax on profit at standard U.K. rate of 19%	6,857	(2,706)	31,626
Expenses not deductible for income tax purposes (permanent differences)	(965)	(708)	(13,270)
Income not taxable	12	78	4
Temporary timing differences		(65)
R&D relief uplift	558	1,435	1,214
Losses (unrecognized)	(4,810)	(345)	(14,479)
Foreign tax	422	505	184
Differences in overseas tax rates	323		261
Derecognition of deferred tax		286	(2,686)
Effects of carryback loss relief	(649)
Adjustments in respect of prior years	612
Other	(463)	4	(32)
Tax credit for the year	£ 1,897	£ (1,516)	£ 2,822

Taxation - Summary of Reconci_2

Taxation - Summary of Reconciliation to the Earnings Loss Per Income Statement (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
U.K. Tax Authority [Member]
Disclosure Of Income Tax Credit [line items]
Statutory income tax rate	19%	19%	19%

Taxation - Summary of Deferred

Taxation - Summary of Deferred Tax (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	£ 63,344	£ 55,551	£ 48,032
Losses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	47,209	44,683	37,021
Loan relationships [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	443	73	421
U.S. tax credits [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	12,206	10,557	9,880
R&D capitalization [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	3,001
Fixed assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	0		414
Share options [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	434	151	55
Other U.S. deferred tax [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	0	31	86
Other [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	0		137
Temporary differences [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred tax asset (unrecognised)	£ 51	£ 56	£ 18

Taxation - Summary of analysis

Taxation - Summary of analysis of recognized deferred tax (Detail) £ in Thousands	12 Months Ended
	Dec. 31, 2022 GBP (£)
Disclosure Of Analysis Of Recognized Deferred Tax [Line Items]
Deferred tax asset/(liabilities)	£ (55,551)
Deferred tax asset/(liabilities)	(63,344)
Intangible Asset and Right of Use Asset [member]
Disclosure Of Analysis Of Recognized Deferred Tax [Line Items]
Deferred tax asset/(liabilities)	(20)
Recognized in income	(156)
Deferred tax asset/(liabilities)	(176)
Net operating losses and lease liability [member]
Disclosure Of Analysis Of Recognized Deferred Tax [Line Items]
Deferred tax asset/(liabilities)	20
Recognized in income	156
Deferred tax asset/(liabilities)	£ 176

Earnings per share-Summary of e

Earnings per share-Summary of earning per share (Details) - GBP (£) £ / shares in Units, £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings per share [line items]
(Loss)/profit attributable to equity holders of the parent	£ (34,196)	£ 12,725	£ (163,628)
Weighted average number of ordinary shares	603,196,403	527,818,648	338,953,141
(Loss)/profit per share – basic (£)	£ (0.06)	£ 0.02	£ (0.48)
Effect of dilutive ordinary shares		£ (38,523)
Numerator – Diluted earnings per share	£ (34,196)	£ (25,798)	£ (163,628)
Number of ordinary shares used for basic earnings per share	603,196,403	527,818,648	338,953,141
Weighted average effect of dilutive ordinary shares		27,457,163
Weighted average number of diluted ordinary shares outstanding	603,196,403	555,275,811	338,953,141
Loss per share – diluted (£)	£ (0.06)	£ (0.05)	£ (0.48)

Property, plant and equipment -

Property, plant and equipment - Additional information (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of detailed information about property, plant and equipment [line items]
Lease payments	£ 937	£ 692	£ 2,086

Property, Plant and Equipment_2

Property, Plant and Equipment - Summary of IFRS 16 Lease Explanatory (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	£ 2,530	£ 1,573
Ending balance	1,831	2,530
Cost or valuation [Member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	4,108	3,384
Additions	10	1,473
Lease modification		163
Disposals	(777)	(875)
Currency translation effects	18	(37)
Ending balance	3,359	4,108
Depreciation/Amortization and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	(1,578)	(1,811)
Disposals	777	874
Depreciation for the year	(727)	(642)
Ending balance	(1,528)	(1,578)
Leasehold improvements [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	433	79
Ending balance	338	433
Leasehold improvements [member] | Cost or valuation [Member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	557	164
Additions	0	393
Disposals	0
Currency translation effects	0
Ending balance	557	557
Leasehold improvements [member] | Depreciation/Amortization and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	(124)	(85)
Disposals	0
Depreciation for the year	(95)	(39)
Ending balance	(219)	(124)
Office equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	104	6
Ending balance	88	104
Office equipment [member] | Cost or valuation [Member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	173	71
Additions	7	109
Disposals	(16)	(7)
Currency translation effects	0
Ending balance	164	173
Office equipment [member] | Depreciation/Amortization and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	(69)	(65)
Disposals	16	7
Depreciation for the year	(23)	(11)
Ending balance	(76)	(69)
IT equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	51	25
Ending balance	28	51
IT equipment [member] | Cost or valuation [Member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	180	132
Additions	3	48
Disposals	(10)
Currency translation effects	0
Ending balance	173	180
IT equipment [member] | Depreciation/Amortization and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	(129)	(107)
Disposals	10
Depreciation for the year	(26)	(22)
Ending balance	(145)	(129)
Right-of-use asset (building) [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	1,878	1,318
Ending balance	1,377	1,878
Right-of-use asset (building) [member] | Cost or valuation [Member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	2,903	1,848
Additions	0	923
Lease modification		133
Disposals	(451)
Currency translation effects	13	(1)
Ending balance	2,465	2,903
Right-of-use asset (building) [member] | Depreciation/Amortization and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	(1,025)	(531)
Disposals	451	0
Depreciation for the year	(514)	(494)
Ending balance	(1,088)	(1,025)
Right-of-use asset (equipment) [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	64	146
Ending balance	0	64
Right-of-use asset (equipment) [member] | Cost or valuation [Member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	295	1,169
Additions	0
Lease modification		30
Disposals	(300)	(868)
Currency translation effects	5	(36)
Ending balance	0	295
Right-of-use asset (equipment) [member] | Depreciation/Amortization and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning balance	(231)	(1,023)
Disposals	300	868
Depreciation for the year	(69)	(76)
Ending balance	£ 0	£ (231)

Property, plant and equipment_3

Property, plant and equipment - Summary of Maturity of Lease Liabilities (Detail) £ in Thousands	Dec. 31, 2022 GBP (£)
Disclosure of maturity analysis of operating lease payments [line items]
Maturity of Lease liabilities	£ 1,688
Within 1 year [member]
Disclosure of maturity analysis of operating lease payments [line items]
Maturity of Lease liabilities	466
Between 1 and 3 years [member]
Disclosure of maturity analysis of operating lease payments [line items]
Maturity of Lease liabilities	1,072
Between 3 and 5 years [member]
Disclosure of maturity analysis of operating lease payments [line items]
Maturity of Lease liabilities	£ 150

Intangible Assets - Summary of

Intangible Assets - Summary of Detailed Information about Intangible Assets (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disclosure of detailed information about intangible assets [line items]
Beginning balance	£ 24,564
Ending balance	24,116	£ 24,564
Cost or valuation [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	33,005	33,005
Ending balance	33,005	33,005
Depreciation/Amortization and impairment [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	(8,441)	(1,357)
Revision to estimated value	(448)	2,373
Out-license of intangible asset		(9,457)
Ending balance	£ (8,889)	£ (8,441)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) £ in Thousands, $ in Millions			12 Months Ended
	Jan. 25, 2021 GBP (£)	Oct. 28, 2017 GBP (£)	Dec. 31, 2022 GBP (£)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 GBP (£)
Disclosure of detailed information about intangible assets [line items]
Amortisation charge recognised on intangible assets			£ 0	£ 0
Deferred equity consideration			3,862	3,302		£ 1,558
Upfront Payment Received	£ 36,500				$ 50
Receipt of future milestones and royalties	254,000
Intangible assets other than goodwill	£ 9,500		24,116	24,564
MPH-966 [member]
Disclosure of detailed information about intangible assets [line items]
Deferred equity consideration		£ 7,200
Present value of provision for deferred cash consideration			400	£ 2,400
Other intangible assets [member]
Disclosure of detailed information about intangible assets [line items]
Revision in the value of any other intangible assets			£ 0

Impairment Testing of Acquire_3

Impairment Testing of Acquired Development Programs Not Yet Available for Use - Summary of Carrying Amount of Acquired Development Programs (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Disclosure of detailed information about intangible assets [line items]
Acquired development programs	£ 24,116	£ 24,564
BPS-804/UX143 [member]
Disclosure of detailed information about intangible assets [line items]
Acquired development programs	2,159	2,159
MPH-966 [member]
Disclosure of detailed information about intangible assets [line items]
Acquired development programs	7,760	8,208
BGS-649 [member]
Disclosure of detailed information about intangible assets [line items]
Acquired development programs	9,886	9,886
BCT-197 [member]
Disclosure of detailed information about intangible assets [line items]
Acquired development programs	£ 4,311	£ 4,311

Impairment Testing of Acquire_4

Impairment Testing of Acquired Development Programs Not Yet Available for Use - Additional Information (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disclosure of quantitative information about right-of-use assets [abstract]
Impairment of the acquired products' rights	£ 0
Cash flow projections - Industry-standard asset life	20 years
Discount rates	15%	12%

Other Receivables - Summary of

Other Receivables - Summary of Other Receivables (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Disclosure of other receivables [abstract]
Lease deposits	£ 293	£ 408
VAT recoverable	362	387
Other	107	624
Total	£ 762	£ 1,419

Cash and Short-term Deposits -

Cash and Short-term Deposits - Summary of Cash and Short-term Deposits (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash and cash equivalents [abstract]
Cash	£ 5,230	£ 93,727
Short-term deposits	51,104	569
Total	£ 56,334	£ 94,296	£ 23,469	£ 16,347

Cash and short-term deposits _2

Cash and short-term deposits - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022
Text block [abstract]
Number of days threshold limit of Short term deposits	90 days

Trade and Other Payables - Summ

Trade and Other Payables - Summary of Trade and Other Payables (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Trade and other payables [abstract]
Trade payables	£ 2,886	£ 2,285
Social security and other taxes	167	190
Other payables	25	24
Trade and other current payables	£ 3,078	£ 2,499

Provisions - Summary of Provisi

Provisions - Summary of Provisions (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure provisions [line items]
Provisions	£ 4,822	£ 4,123
Current	4,822	2,803
Non-current		1,320
Social security contributions on share options [member]
Disclosure provisions [line items]
Provisions	9		£ 109
Provision for deferred cash consideration [member]
Disclosure provisions [line items]
Provisions	4,634	£ 4,123
Restructuring [member]
Disclosure provisions [line items]
Provisions	£ 179

Provisions - Summary of Social

Provisions - Summary of Social Security Contributions on Share Options (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disclosure of other provisions [line items]
Beginning balance	£ 4,123
Increase in provision due to changes in foreign exchange rates	548	£ (10)
Ending balance	4,822	4,123
Social security contributions on share options [member]
Disclosure of other provisions [line items]
Beginning balance		109
Arising/(released) during the year, net	9	(109)
Ending balance	9
Deferred cash consideration [member]
Disclosure of other provisions [line items]
Beginning balance	4,123	1,525
Increase in provision due to the unwinding of the time value of money	451	225
Increase in provision due to changes in foreign exchange rates	508
Decrease in provision due to a change in estimates relating to timeline and probabilities of contractual milestones being achieved	(448)	2,373
Ending balance	4,634	£ 4,123
Restructuring [member]
Disclosure of other provisions [line items]
Arising/(released) during the year, net	179
Ending balance	£ 179

Provisions - Additional Informa

Provisions - Additional Information (Detail) - GBP (£) £ in Thousands	1 Months Ended	12 Months Ended
	Oct. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Disclosure of other provisions [line items]
Termination benefit expense		£ 200
Provisions		4,822	£ 4,123
Top of range [member]
Disclosure of other provisions [line items]
Employee base reduction percentage	40%
Restructuring [member]
Disclosure of other provisions [line items]
Provisions		£ 179

Private Placement - Additional

Private Placement - Additional Information (Detail) - GBP (£) £ / shares in Units, £ in Millions		12 Months Ended
	Jun. 03, 2020	Dec. 31, 2022	Dec. 31, 2021	Feb. 10, 2020
Statement [line items]
Private Placement Offerings	£ 56
Common stock shares issued	89,144,630
Par value per share	£ 0.003
Shares issued price per share	£ 0.174
Proceeds from Issuance of Convertible Notes	£ 40.5
Borrowing interest rate		6%
Conversion of loan notes into ordinary shares amount		£ 40.5
Convertible loan amount		£ 18.9
Percentage Number Of Shares Issuable		50%
Exercise price per warrants		£ 0.348
Debt maturity		June 30, 2023
Loan Notes [Member]
Statement [line items]
Common stock shares issued		40,020,280	40,397,976
Par value per share		£ 0.174
Notional amount		£ 6.2	£ 12.4
Novartis [member]
Statement [line items]
Borrowing interest rate				6%
Conversion of loan notes into ordinary shares amount		£ 21.8
Number of converted loans converted to ordinary shares		125,061,475
Notional amount				£ 3.8
Warrants [Member]
Statement [line items]
Common stock shares issued	161,048,366
Warrants issued		161,048,366
Fair value of the warrants		£ 4.1
Loans And Notes
Statement [line items]
Notional amount		38.6
Debt Host Instrument
Statement [line items]
Notional amount		26.7
Embedded Derivative
Statement [line items]
Notional amount		£ 11.9
Tranche 1 Notes [Member]
Statement [line items]
Proceeds from Issuance of Convertible Notes	£ 15.5

Warrant Liability - Summary of

Warrant Liability - Summary of Warrant Liability (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Warrant Liability [Abstract]
Beginning balance	£ 8,336	£ 50,775
Issued during the year	0
Settled during the year		(2,400)
Fair value changes during the year	(7,805)	(40,039)
Ending balance	£ 531	£ 8,336

Warrant Liability - Additional

Warrant Liability - Additional Information (Detail) £ / shares in Units, £ in Thousands	12 Months Ended
	Dec. 31, 2022 GBP (£) £ / Warrant £ / shares shares	Dec. 31, 2021 GBP (£) £ / Warrant £ / shares shares	Dec. 31, 2022 $ / shares	Dec. 31, 2021 $ / shares	Dec. 31, 2020 GBP (£)	Jun. 30, 2020 £ / shares shares
Disclosure of classes of share capital [line items]
Percentage of ordinary share capital	24%	25%
Warrant liability | £	£ 531	£ 8,336			£ 50,775
Exercise price per warrants | £ / shares	£ 0.348
fair value of the warrant liability | £	£ 400	£ 8,000
Number of warrants exercised during period		14,954,491
Private placement [Member]
Disclosure of classes of share capital [line items]
Warrants issued						161,048,366
Fair Value Adjustments Of Warrants | £	£ 7,600
Exercise price per warrants | £ / shares						£ 0.348
Number of warrants exercised during period	0	15,414,626
Bank loan [member]
Disclosure of classes of share capital [line items]
Warrant liability | £	£ 100	£ 300
Bank loan [member] | Ordinary shares [member] | Warrants Subscribed [Member]
Disclosure of classes of share capital [line items]
Exercise price per warrants | £ / shares	£ 2.95	£ 2.95
Class of warrant number of securities called by warrants	1,243,908	1,243,908
Bank loan [member] | Ordinary shares [member] | Two Thousand And Twenty Warrants [Member]
Disclosure of classes of share capital [line items]
Exercise price per warrants | $ / shares			$ 0.4144	$ 0.4144
Class of warrant number of securities called by warrants	1,243,908	1,243,908
Warrant [Member]
Disclosure of classes of share capital [line items]
Number of warrants outstanding	147,431,351	147,431,351
Number of warrants exercised | £ / Warrant	0	0

Warrant Liability - Summary o_2

Warrant Liability - Summary of Weighted Average Inputs to the Models Used for the Fair Value of Warrants Granted (Detail) - Warrant liability [member]	12 Months Ended
	Dec. 31, 2022 £ / shares	Dec. 31, 2021 $ / shares
Disclosure of classes of share capital [line items]
Expected volatility	95%	75%
Risk-free interest rate	3.99%	0.90%
Expected life of warrants (years)	6 months	1 year 6 months
Market price of ADS | (per share)	£ 0.75	$ 1.6
Model used	Black-Scholes	Black-Scholes

Convertible loan notes - Summar

Convertible loan notes - Summary of Interest-bearing Loans and Borrowings (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Disclosure of detailed information about borrowings [abstract]
Novartis Loan Note	£ 4,449	£ 3,771
Loan Notes – private placement	6,636	10,613
Total	11,085	14,384
Current	11,085	0
Non-current	£ 0	£ 14,384

Convertible loan notes - Additi

Convertible loan notes - Additional Information (Detail) - GBP (£) £ / shares in Units, £ in Millions			12 Months Ended
	Jun. 03, 2020	Feb. 10, 2020	Dec. 31, 2022
Disclosure of detailed information about borrowings [line items]
Borrowing interest rate			6%
Derecogniton of the embedded derivative			£ 41.6
Proceeds from Issuance of Convertible Notes	£ 40.5
Fair value of the liability component net of transaction costs	£ 24.4
Embedded derivative loan notes outstanding			33.5
Embedded derivative
Disclosure of detailed information about borrowings [line items]
Notes issued value			11.9
Derivative financial liabilities			63.2
Notional amount			£ 11.9
Novartis [member]
Disclosure of detailed information about borrowings [line items]
Issuance of unsecured convertible loan notes			21,700,000
Borrowing interest rate		6%
Number of converted loans converted to ordinary shares			125,061,475
Conversion price per share		£ 0.265
Notes issued value		£ 3.8
Accreted interest on bank loan			£ 13.3
Exercise price of warrants		£ 0.265
Number of securities called by warrants or rights		1,449,614
Expiry date of warrants		Feb. 10, 2025
Notional amount		£ 3.8

Convertible loan notes - Summ_2

Convertible loan notes - Summary Of Movements In The Carrying Value Of The Liability Component Of The Loan Notes (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
DisclosureOfMovementsInTheCarryingValueOfTheLiabilityComponentOfTheLoanNotes [Abstract]
January 1	£ 10,613	£ 12,946
Issued	0	0
Interest charged	1,981	2,974
Converted to equity	(5,958)	(5,307)
December 31	£ 6,636	£ 10,613

Issued Capital and Reserves - S

Issued Capital and Reserves - Summary of Detailed Information of Ordinary Share Capital (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of classes of share capital [line items]
Beginning balance	£ 88,002	£ (14,971)	£ 40,256
Issued during the year		79,210	16,937
Ending balance	61,868	88,002	(14,971)
Beginning balance	247,460
Ending balance	254,303	247,460
Share premium [member]
Disclosure of classes of share capital [line items]
Beginning balance	247,460	161,785	121,684
Issued during the year		78,609	18,715
Ending balance	254,303	247,460	161,785
Beginning balance	247,460	161,785	121,684
Issued for public offering	6,843	85,909
Ending balance	£ 254,303	247,460	161,785
Transaction Costs [Member] | Share premium [member]
Disclosure of classes of share capital [line items]
Transaction costs for issued share capital		£ (234)	(1,307)
Private Placement [member] | Share premium [member]
Disclosure of classes of share capital [line items]
Issued for public offering			15,244
Conversion of Loan Note [member] | Share premium [member]
Disclosure of classes of share capital [line items]
Issued for public offering			21,386
Securities Purchase Agreement [Member] | Aspire Capital One [member] | Share premium [member]
Disclosure of classes of share capital [line items]
Issued for public offering			2,511
Securities Purchase Agreement [Member] | Aspire Capital Two [member] | Share premium [member]
Disclosure of classes of share capital [line items]
Issued for public offering			£ 2,267
Ordinary shares [member]
Disclosure of classes of share capital [line items]
Ordinary shares issued and fully paid, Beginning balance	584,908,239	338,953,141	97,959,622
Issued	40,020,280	245,955,098
Ordinary shares issued and fully paid, Ending balance	624,928,519	584,908,239	338,953,141
Ordinary shares [member] | Private Placement [member]
Disclosure of classes of share capital [line items]
Issued			89,144,630
Ordinary shares [member] | Conversion of Loan Note [member]
Disclosure of classes of share capital [line items]
Issued			125,061,475
Ordinary shares [member] | Conversion of Warrants [member]
Disclosure of classes of share capital [line items]
Issued			239,179
Ordinary shares [member] | Securities Purchase Agreement [Member] | Aspire Capital One [member]
Disclosure of classes of share capital [line items]
Issued			14,295,520
Ordinary shares [member] | Securities Purchase Agreement [Member] | Aspire Capital Two [member]
Disclosure of classes of share capital [line items]
Issued			12,252,715
Ordinary share capital [member]
Disclosure of classes of share capital [line items]
Beginning balance	£ 1,755	£ 1,017	£ 294
Issued during the year	120	738
Ending balance	£ 1,875	£ 1,755	1,017
Ordinary share capital [member] | Private Placement [member]
Disclosure of classes of share capital [line items]
Issued during the year			267
Ordinary share capital [member] | Conversion of Loan Note [member]
Disclosure of classes of share capital [line items]
Issued during the year			375
Ordinary share capital [member] | Conversion of Warrants [member]
Disclosure of classes of share capital [line items]
Issued during the year			1
Ordinary share capital [member] | Securities Purchase Agreement [Member] | Aspire Capital One [member]
Disclosure of classes of share capital [line items]
Issued during the year			43
Ordinary share capital [member] | Securities Purchase Agreement [Member] | Aspire Capital Two [member]
Disclosure of classes of share capital [line items]
Issued during the year			£ 37

Issued Capital and Reserves - A

Issued Capital and Reserves - Additional Information (Detail) - GBP (£) £ / shares in Units, £ in Thousands										12 Months Ended
	May 04, 2021	Feb. 12, 2021	Dec. 23, 2020	Jun. 30, 2020	Jun. 04, 2020	Jun. 03, 2020	Feb. 20, 2020	Feb. 11, 2020	Mar. 21, 2016	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure of classes of share capital [line items]
Ordinary shares issued and allotted						89,144,630
Nominal value						£ 0.003
Ordinary shares price per share				£ 0.174			£ 0.19	£ 0.08
Cash consideration	£ 1,500											£ 1,090
Conversion of loan notes into ordinary shares amount										£ 40,500
Equity component (consideration received for the warrants)										100	£ 100
Fair value of Acquisition for Ordinary shares	1,090
Nominal value of issued capital										£ 1,875	1,755
Gain loss on extnguishment of financial liability											£ 200
Number of warrants exercised during period											14,954,491
Number of ADS equivalents to warrants issued during period											2,990,898
Exercise price per warrants										£ 0.348
Upfront Consideration	£ 1,500											1,090
Number of warrants issued in exchange for funds										1,101,683
Proceeds from exercise Of warrants										£ 200
Equity										61,868	£ 88,002	(14,971)	£ 40,256
Noncash Warrant Exercises [Member]
Disclosure of classes of share capital [line items]
Number of warrants exercised during period											460,135
Exercise price per warrants											£ 0.348
Issued capital [member]
Disclosure of classes of share capital [line items]
Equity										1,875	£ 1,755	£ 1,017	£ 294
Other Reserve [Member]
Disclosure of classes of share capital [line items]
Issued						89,144,630
Warrants [Member]
Disclosure of classes of share capital [line items]
Equity										£ 100
Conversion Of Warrants [Member]
Disclosure of classes of share capital [line items]
Exercise price per warrants											£ 0.348
Directors [member]
Disclosure of classes of share capital [line items]
Reduction in share premium									£ 7,000
Novartis [member]
Disclosure of classes of share capital [line items]
Conversion of loan notes into ordinary shares amount				£ 21,800
Number of converted loans converted to ordinary shares				125,061,475
Amount recognised on conversion and carrying value of the financial liability extinguished				£ 33,500
Aspire Capital Fund LLC [Member]
Disclosure of classes of share capital [line items]
Ordinary shares price per share								£ 0.2
Cash consideration								£ 2,300
Number of converted loans converted to ordinary shares								2,862,595
Issued								572,519
Upfront Consideration								£ 2,300
Ordinary shares [member]
Disclosure of classes of share capital [line items]
Ordinary shares issued and allotted	2,100,840	198,375,000		125,061,475	89,144,630		12,252,715	11,432,925		40,020,280	40,397,976
Nominal value	£ 0.003	£ 0.003		£ 0.003						£ 0.003	£ 0.003
Ordinary shares price per share	£ 0.517	£ 0.395		£ 0.174	£ 0.174					£ 0.174	£ 0.174
Cash consideration				£ 21,800	£ 15,500		£ 2,300
Reduction in share premium						£ 2,100
Shares issued as fully paid up										624,928,519	584,908,239	338,953,141	97,959,622
Fair value of Acquisition for Ordinary shares						13,400
Proceeds from issue of ordinary shares		£ 78,400			13,400	£ 15,500
Discount On Issue Of Shares					2,100
Issued										40,020,280	245,955,098
Transaction costs associated with issue of share capital		£ 200									£ 200
Upfront Consideration				£ 21,800	£ 15,500		£ 2,300
Ordinary shares [member] | OncoMed [Member]
Disclosure of classes of share capital [line items]
Fair value of Acquisition for Ordinary shares										£ 40,900
Ordinary shares [member] | OncoMed [Member] | Issued capital [member]
Disclosure of classes of share capital [line items]
Excess Amount Within Other Capital Reserves										40,800
Ordinary shares [member] | Private placement [Member]
Disclosure of classes of share capital [line items]
Issued												89,144,630
Ordinary shares [member] | Conversion Of Warrants [Member]
Disclosure of classes of share capital [line items]
Share conversion price per share			£ 0.348
Number Of Warrants converted			690,205								4,621,147
Issued												239,179
Ordinary shares [member] | Aspire Capital Fund LLC [Member]
Disclosure of classes of share capital [line items]
Commitement to issue capital								£ 25,000
Novartis bonus shares [member]
Disclosure of classes of share capital [line items]
Conversion of loan notes into ordinary shares amount										£ 1,080	£ 1,080
Merger reserve [member] | OncoMed [Member]
Disclosure of classes of share capital [line items]
Shares issued as fully paid up										24,783,320
Merger reserve [member] | OncoMed [Member] | Issued capital [member]
Disclosure of classes of share capital [line items]
Nominal value of issued capital										£ 100
Capital reserve [member] | Equity component of convertible loan [member]
Disclosure of classes of share capital [line items]
Gain loss on extnguishment of financial liability										£ 33,100
ADS [Member]
Disclosure of classes of share capital [line items]
Ordinary shares issued and allotted		39,675,000
Ordinary shares price per share		£ 2.726
Number of new stock issued			47,835
ADS [Member] | Noncash Warrant Exercises [Member]
Disclosure of classes of share capital [line items]
Number of warrants exercised during period											92,027
ADS [Member] | Other Reserve [Member]
Disclosure of classes of share capital [line items]
Reduction In Warrant Liability											£ 2,400
ADS [Member] | Private placement [Member]
Disclosure of classes of share capital [line items]
Number Of Warrants converted											15,414,626
ADS [Member] | Conversion Of Warrants [Member]
Disclosure of classes of share capital [line items]
Number Of Warrants converted			138,041								924,229

Issued Capital and Reserves -_2

Issued Capital and Reserves - Summary of Other Capital Reserves (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of classes of share capital [line items]
Beginning balance	£ 7,401	£ 5,001
Share-based payments expense during the year	3,862	3,302	£ 1,558
Issuance of warrants	70
Ending balance	7,401	7,401	5,001
Capital reserve [member]
Disclosure of classes of share capital [line items]
Beginning balance	129,835	128,374	59,147
Share-based payments expense during the year	3,862	3,302	1,558
Share options exercised	(82)	(119)
Novartis convertible loan note instrument and warrants			1,084
Conversion of Loan Notes	(1,005)	(1,722)	33,104
Reclassification of the embedded derivative			33,481
Issuance of warrants	70
Ending balance	132,680	129,835	128,374
Share-based payments [member] | Capital reserve [member]
Disclosure of classes of share capital [line items]
Beginning balance	23,026	19,843	18,285
Share-based payments expense during the year	3,862	3,302	1,558
Share options exercised	(82)	(119)
Conversion of Loan Notes	0
Ending balance	26,806	23,026	19,843
Equity component of convertible loan [member] | Capital reserve [member]
Disclosure of classes of share capital [line items]
Beginning balance	32,843	34,565
Share-based payments expense during the year	0
Share options exercised	0
Novartis convertible loan note instrument and warrants			1,084
Conversion of Loan Notes	(1,005)	(1,722)
Reclassification of the embedded derivative			33,481
Ending balance	31,838	32,843	34,565
Other Warrents Issued [Member] | Capital reserve [member]
Disclosure of classes of share capital [line items]
Beginning balance	44	44	44
Share-based payments expense during the year	0
Share options exercised	0
Conversion of Loan Notes	0
Issuance of warrants	70
Ending balance	114	44	44
Merger reserve [member] | Capital reserve [member]
Disclosure of classes of share capital [line items]
Beginning balance	40,818	40,818	40,818
Share-based payments expense during the year	0
Share options exercised	0
Conversion of Loan Notes	0
Ending balance	40,818	40,818	40,818
Other Reserve [Member] | Capital reserve [member]
Disclosure of classes of share capital [line items]
Beginning balance	33,104	33,104
Share-based payments expense during the year	0
Share options exercised	0
Conversion of Loan Notes	0		33,104
Ending balance	£ 33,104	£ 33,104	£ 33,104

Issued Capital and Reserves -_3

Issued Capital and Reserves - Summary of Accumulated Loss (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of classes of share capital [abstract]
Other reserves	£ 7,401	£ 7,401	£ 5,001
Accumulated losses	£ (331,164)	£ (296,968)	£ (309,693)

Changes in Liabilities Arisin_3

Changes in Liabilities Arising from Financing Activities - Summary of Changes in Liabilities Arising from Financing Activities (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	£ 29,299	£ 70,298
Financing cash flows	(784)	(692)
Settled during the year	(5,958)	(7,707)
Interest expense	3,338	4,003
Issuance of warrants	(70)
Lease addition		910
Lease modifications		163
Changes in fair values	(8,253)	(37,666)
Changes in foreign exchange	548	(10)
Ending balance	18,120	29,299
Lease liability [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	2,376	1,794
Financing cash flows	(937)	(692)
Interest expense	209	230
Lease addition		910
Lease modifications		163
Changes in foreign exchange	40	(29)
Ending balance	1,688	2,376
Novartis Loan notes [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	3,771	3,196
Interest expense	678	575
Ending balance	4,449	3,771
Warrant liability [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	8,336	50,775
Settled during the year		(2,400)
Changes in fair values	(7,805)	(40,039)
Ending balance	531	8,336
Deferred cash consideration [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	4,123	1,525
Interest expense	451	206
Changes in fair values	(448)	2,373
Changes in foreign exchange	508	19
Ending balance	4,634	4,123
Loan Notes – private placement [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	10,613	12,946
Settled during the year	(5,958)	(5,307)
Interest expense	1,981	2,974
Ending balance	6,636	10,613
Other [Member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	80	62
Financing cash flows	153
Interest expense	19	18
Issuance of warrants	(70)
Ending balance	£ 182	£ 80

Financial and Capital Risk Ma_3

Financial and Capital Risk Management and Fair Value Measurement - Additional Information (Detail) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2020 GBP (£)	Dec. 31, 2021 GBP (£)
Disclosure of detailed information about financial instruments [line items]
Fair value of the contingent consideration liability	£ 0			£ 0
Percentage of increase decrease in sensitivity analysis affecting input to fair value	10%	10%
Milestone payment for regulatory and commercial achievements | $		$ 302
Global Licensing Agreement [member]
Disclosure of detailed information about financial instruments [line items]
Milestone payment for regulatory and commercial achievements	£ 0.7		£ 0.4

Financial and Capital Risk Ma_4

Financial and Capital Risk Management and Fair Value Measurement - Summary of Changes In Significant Unobservable Inputs Under Valuation Model Used In Level Fair Value Measurement (Detail) £ in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2022 USD ($)
Disclosure of significant unobservable inputs used in fair value measurement [line items]
Percentage of increase decrease in sensitivity analysis affecting input to fair value	10%	10%
Undiscounted contingent liability for future payments | $				$ 80
Milestone payment for regulatory and commercial achievements | $		$ 302
Weighted average cost of capital [member] | Provision for deferred cash consideration [member] | Discounted cash flow model [member]
Disclosure of significant unobservable inputs used in fair value measurement [line items]
Weighted average cost of capital	15%		12%	15%
Percentage of increase decrease in sensitivity analysis affecting input to fair value	1%	1%	1%
Increase decrease in sensitivity analysis affecting input to fair value	£ 25,000		£ 31,000
Probability of success [member] | Provision for deferred cash consideration [member] | Discounted cash flow model [member]
Disclosure of significant unobservable inputs used in fair value measurement [line items]
Percentage of increase decrease in sensitivity analysis affecting input to fair value	10%	10%	10%
Increase decrease in sensitivity analysis affecting input to fair value	£ 600		£ 500
Bottom of range [member] | Probability of success [member] | Provision for deferred cash consideration [member] | Discounted cash flow model [member]
Disclosure of significant unobservable inputs used in fair value measurement [line items]
Probability of success	40.60%	40.60%	40.60%
Top of range [member] | Probability of success [member] | Provision for deferred cash consideration [member] | Discounted cash flow model [member]
Disclosure of significant unobservable inputs used in fair value measurement [line items]
Probability of success	81.20%	81.20%	81.20%
Weighted average [member] | Expected Volatility Member [Member] | Warrants Related To Private Placement [Member] | Black And Scholes Method [member]
Disclosure of significant unobservable inputs used in fair value measurement [line items]
Expected Volatility Percentage	95.50%	95.50%	75.10%
Weighted average [member] | Expected Volatility One [Member] | Warrants Related To Private Placement [Member] | Black And Scholes Method [member]
Disclosure of significant unobservable inputs used in fair value measurement [line items]
Expected Volatility Percentage	91.80%	91.80%	67.40%
Financial liabilities, at fair value	£ 300		£ 6,700

Financial and Capital Risk Ma_5

Financial and Capital Risk Management and Fair Value Measurement - Summary of Maturity Profile of Financial Liabilities Based on Contractual Undiscounted Payments (Detail) £ in Thousands	Dec. 31, 2022 GBP (£)
lease [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	£ 1,985
Trade And Other Payables [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	3,078
Accruals [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	4,491
Within 1 year [member] | lease [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	611
Within 1 year [member] | Trade And Other Payables [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	3,078
Within 1 year [member] | Accruals [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	4,491
Between 1 and 3 years [member] | lease [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	1,222
Between 1 and 3 years [member] | Trade And Other Payables [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	0
Between 1 and 3 years [member] | Accruals [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	0
Between 3 and 5 years [member] | lease [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	152
Between 3 and 5 years [member] | Trade And Other Payables [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	0
Between 3 and 5 years [member] | Accruals [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	0
Over 5 years [member] | Trade And Other Payables [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	0
Over 5 years [member] | Accruals [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Financial liabilities on contractual undiscounted payments	£ 0

Financial and Capital Risk Ma_6

Financial and Capital Risk Management and Fair Value Measurement - Detailed Information About Cash And Cash Equivalents By Currency Type (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Detailed Information about Cash and Cash Equivalents by Currency Type [Line Items]
Cash and cash equivalents	£ 56,334	£ 94,296	£ 23,469	£ 16,347
Pound Sterling [Member]
Detailed Information about Cash and Cash Equivalents by Currency Type [Line Items]
Cash and cash equivalents	52,812	92,104
U.S. dollars [Member]
Detailed Information about Cash and Cash Equivalents by Currency Type [Line Items]
Cash and cash equivalents	2,484	2,018
Euro [Member]
Detailed Information about Cash and Cash Equivalents by Currency Type [Line Items]
Cash and cash equivalents	1,029	165
Swiss Francs [Member]
Detailed Information about Cash and Cash Equivalents by Currency Type [Line Items]
Cash and cash equivalents	£ 9	£ 9

Financial and Capital Risk Ma_7

Financial and Capital Risk Management and Fair Value Measurement - Detailed Information About Gain Loss On Foreign Currency Translaction Recognized In Income Statement (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of detailed information about financial instruments [line items]
Net foreign exchange gain/(loss)	£ 1,525	£ (954)	£ (1,821)
Market Uncertainty [member]
Disclosure of detailed information about financial instruments [line items]
Net foreign exchange gain/(loss)	1,461	787
U.S. dollars [Member] | Market Uncertainty [member]
Disclosure of detailed information about financial instruments [line items]
Net foreign exchange gain/(loss)	872	920
Euro [Member] | Market Uncertainty [member]
Disclosure of detailed information about financial instruments [line items]
Net foreign exchange gain/(loss)	768	(142)
Swiss Francs [Member] | Market Uncertainty [member]
Disclosure of detailed information about financial instruments [line items]
Net foreign exchange gain/(loss)	£ (179)	£ 9

Financial and Capital Risk Ma_8

Financial and Capital Risk Management and Fair Value Measurement - Details the Group's Sensitivity to a 10% Change in the Period-End Rate (Detail) £ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Statement [line items]
Profit (loss) before tax	£ (36,093)		£ 14,241		£ (166,450)
Currency risk [member]
Statement [line items]
Profit (loss) before tax	(70)	$ (79)	13	$ (84)
Equity	£ (70)		£ 13			$ (79)	$ (84)

Financial and Capital Risk Ma_9

Financial and Capital Risk Management and Fair Value Measurement - Summary of Fair Value Hierarchy (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Provision for deferred cash consideration [member]
Disclosure of fair value measurement of liabilities [line items]
Date of valuation	Dec. 31, 2022	Dec. 31, 2021
Financial liabilities at fair value	£ 4,634	£ 4,123
Warrant liability [member] | Not measured at fair value in statement of financial position but for which fair value is disclosed [member]
Disclosure of fair value measurement of liabilities [line items]
Date of valuation	Dec. 31, 2022	Dec. 31, 2021
Financial liabilities at fair value	£ 531	£ 8,336
Quoted prices in active markets (Level 1) | Provision for deferred cash consideration [member]
Disclosure of fair value measurement of liabilities [line items]
Financial liabilities at fair value	0	0
Quoted prices in active markets (Level 1) | Warrant liability [member] | Not measured at fair value in statement of financial position but for which fair value is disclosed [member]
Disclosure of fair value measurement of liabilities [line items]
Financial liabilities at fair value	0	0
Significant observable inputs (Level 2) | Provision for deferred cash consideration [member]
Disclosure of fair value measurement of liabilities [line items]
Financial liabilities at fair value	0	0
Significant observable inputs (Level 2) | Warrant liability [member] | Not measured at fair value in statement of financial position but for which fair value is disclosed [member]
Disclosure of fair value measurement of liabilities [line items]
Financial liabilities at fair value	129	341
Significant unobservable inputs (Level 3) | Provision for deferred cash consideration [member]
Disclosure of fair value measurement of liabilities [line items]
Financial liabilities at fair value	4,634	4,123
Significant unobservable inputs (Level 3) | Warrant liability [member] | Not measured at fair value in statement of financial position but for which fair value is disclosed [member]
Disclosure of fair value measurement of liabilities [line items]
Financial liabilities at fair value	£ 402	£ 7,995

Financial and Capital Risk M_10

Financial and Capital Risk Management and Fair Value Measurement - Summary of changes in level 3 of fair value of hierarchy (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Summary of changes in level 3 of fair value of hierarchy [Line Items]
Beginning balance	£ 4,123
Ending balance	4,822	£ 4,123
Provision for deferred cash consideration [member]
Summary of changes in level 3 of fair value of hierarchy [Line Items]
Beginning balance	4,123
Ending balance	4,634	4,123
Provision for deferred cash consideration [member] | Level 3 of fair value hierarchy [member]
Summary of changes in level 3 of fair value of hierarchy [Line Items]
Beginning balance	4,123	1,525
Settled during the year		0
Unwinding of the time value of money recognised as a finance charge	451	225
Change in foreign exchange rates	508
Change in estimate relating to probabilities (revision to intangible asset, see Note 13)	(448)	2,373
Change in fair value	0	0
Ending balance	4,634	4,123
Warrant liability [member] | Level 3 of fair value hierarchy [member]
Summary of changes in level 3 of fair value of hierarchy [Line Items]
Beginning balance	7,995	49,930
Settled during the year		(2,400)
Unwinding of the time value of money recognised as a finance charge	0	0
Change in foreign exchange rates	0
Change in estimate relating to probabilities (revision to intangible asset, see Note 13)	0	0
Change in fair value	(7,593)	(39,535)
Ending balance	£ 402	£ 7,995

Financial And Capital Risk M_11

Financial And Capital Risk Management And Fair Value Measurement - Summary of Financial instruments by category (Detail) - GBP (£) £ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financial liabilities
Provisions	£ 4,822	£ 4,123
Warrant liability	531	8,336	£ 50,775
Accruals	4,491	3,826
Lease liability	1,688
Fair value through profit or loss [member]
Financial assets
Cash and short-term deposits	0	0
Other receivables	0	0
Total financial assets	0	0
Financial liabilities
Provisions	4,634	4,123
Convertible loan notes	0	0
Warrant liability	531	8,336
Trade and other payables	0	0
Accruals	0	0
Lease liability	0	0
Total financial liabilities	5,165	12,459
Amortized cost [member]
Financial assets
Cash and short-term deposits	56,334	94,296
Other receivables	400	1,032
Total financial assets	56,734	95,328
Financial liabilities
Provisions	187	0
Convertible loan notes	11,086	14,384
Warrant liability	0	0
Trade and other payables	2,911	2,309
Accruals	4,491	3,826
Lease liability	1,688	2,376
Total financial liabilities	£ 20,363	£ 22,895

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) £ in Millions, $ in Millions	1 Months Ended
	Oct. 31, 2017 USD ($) shares	Dec. 31, 2022 GBP (£)
Contract Manufacturing Organizations [Member]
Disclosure of commitments and contingencies [line items]
Contractual capital commitments | £		£ 0.9
Mereo BioPharma 4 Limited [member]
Disclosure of commitments and contingencies [line items]
Payment of ordinary shares	$ 3
Issuance of aggregate ordinary shares | shares	490,798
Aggregate upfront payment amount	$ 5
Payments of aggregate and issue additional ordinary shares	$ 115.5

Share-based Payments - Charge f

Share-based Payments - Charge for Share-based Payments (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share-based payments	£ 3,862	£ 3,302	£ 1,558
2019 Equity Incentive Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share-based payments	3,149	2,860	922
2019 Non-Executive Director Equity Incentive Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share-based payments	713	499	167
2015 Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share-based payments	0	0	3
Mereo BioPharma Group plc Share Option Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share-based payments	0	68	376
Long-term incentive plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share-based payments	£ 0	£ (125)	£ 90

Share-based Payments - Addition

Share-based Payments - Additional Information (Detail) £ / shares in Units, £ in Thousands	12 Months Ended
	Dec. 31, 2022 $ / shares shares	Dec. 31, 2022 shares $ / shares	Dec. 31, 2022 $ / shares shares	Dec. 31, 2022 $ / shares shares	Dec. 31, 2021 shares $ / shares	Dec. 31, 2018 GBP (£)	Dec. 31, 2022 £ / shares shares	Dec. 31, 2020	Dec. 31, 2019 GBP (£)
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of shares each ADR represent		5
Number of options granted		0
Number Of Outstanding Share Options			423,164		625,906
Number of share options outstanding in share-based payment arrangement	7,874,530	7,874,530	7,874,530	7,874,530	8,297,694		7,874,530	8,923,600
ADS [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Weighted average exercise price of share options granted  | $ / shares				$ 1.2	$ 2.5
ADS [Member] | Deferred RSUs [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share based payment arrangement, Award payment term	180 days
Number of trading days	30 days
Weighted average exercise price of other equity instruments granted in share-based payment arrangement | $ / shares				$ 0.99
2015 Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Weighted average remaining contractual life for the share options outstanding period	2 years 7 months 6 days				3 years 7 months 6 days
2015 Plan [member] | Existing Non-Executive Directors [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	4 years
2015 Plan [member] | Newly Non-Executive Directors [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	3 years
2015 Plan [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options outstanding exercise price | £ / shares							£ 1.43
2015 Plan [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options outstanding exercise price | £ / shares							£ 2.44
Mereo BioPharma Group plc Share Option Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Weighted average remaining contractual life for the share options outstanding period	4 years 9 months 18 days				5 years 7 months 6 days
Number Of Outstanding Share Options			770,805		87,430
Number of share options outstanding in share-based payment arrangement	553,160	553,160	553,160	553,160	1,323,965		553,160	1,411,395
Mereo BioPharma Group plc Share Option Plan [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options outstanding exercise price | £ / shares							£ 3.05
Mereo BioPharma Group plc Share Option Plan [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options outstanding exercise price | £ / shares							£ 3.59
Long-term incentive plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted					0
Percentage of options issued to employees	75%	75%	75%	75%			75%
Percentage of options vested to employees	25%	25%	25%	25%			25%
Number of share options expired in share-based payment arrangement			0		482,748
Number Of Outstanding Share Options		0
Number of share options outstanding in share-based payment arrangement	0	0	0	0	0		0	482,748
Deferred bonus share plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Annual bonus payable in deferred shares			30%
2019 Equity Incentive Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Contractual term share options	10 years
Number of options granted			4,126,400		2,696,960
Weighted average remaining contractual life for the share options outstanding period	8 years 4 months 24 days				8 years 8 months 12 days
Vesting period	3 years
Number of share options expired in share-based payment arrangement			1,164,197		253,277
Number Of Outstanding Share Options			48,044		28,521
Number of share options outstanding in share-based payment arrangement	6,857,861	6,857,861	6,857,861	6,857,861	3,943,702		6,857,861	1,567,873
Weighted average exercise price of share options granted  | $ / shares				$ 1.38	$ 2.83
Number of share options exercised in share-based payment arrangement			0		39,333
2019 Equity Incentive Plan [member] | Newly Non-Executive Directors [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	1 year
2019 Equity Incentive Plan [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options outstanding exercise price | $ / shares	$ 0.51	$ 0.51	$ 0.51	0.51
2019 Equity Incentive Plan [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options outstanding exercise price | $ / shares	$ 5.4	$ 5.4	$ 5.4	$ 5.4
2019 Non-Executive Director Equity Incentive Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted			535,488		296,000
Weighted average remaining contractual life for the share options outstanding period	8 years 6 months				8 years 7 months 6 days
Number of share options expired in share-based payment arrangement			42,192		23,625
Number Of Outstanding Share Options			0
Number of share options outstanding in share-based payment arrangement	915,087	915,087	915,087	915,087	421,791		915,087	149,416
Weighted average exercise price of share options granted  | $ / shares				$ 1.22	$ 2.81
Number of share options exercised in share-based payment arrangement			0
2019 Non-Executive Director Equity Incentive Plan [member] | Deferred RSUs [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted			386,144
Number of share options expired in share-based payment arrangement			42,104
Number Of Outstanding Share Options			0
Number of share options outstanding in share-based payment arrangement	344,040	344,040	344,040	344,040			344,040
Number of share options exercised in share-based payment arrangement			0
AstraZeneca [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share issued upon consideration	1,349,693	1,349,693	1,349,693	1,349,693			1,349,693
Deferred Bonus Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options granted		0
Weighted average fair value of options granted | £						£ 0			£ 0
Annual bonus payable in deferred shares						100%
Number of share options expired in share-based payment arrangement			22,592		62,183
Percentage of annual bonus granted to directors						30%
Number of share options outstanding in share-based payment arrangement	100,817	100,817	100,817	100,817			100,817
Weighted average remaining contractual life of outstanding share options	1 month 6 days
Number of share options exercised in share-based payment arrangement		0	78,225		0
Other scheme [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options exercised in share-based payment arrangement		0

Share-based Payments - Summary

Share-based Payments - Summary of Number and Weighted Average Exercise Prices (WAEP) of, and Movements in, Options (Detail)	12 Months Ended
	Dec. 31, 2022 shares $ / shares	Dec. 31, 2022 shares £ / shares $ / shares	Dec. 31, 2021 $ / shares	Dec. 31, 2021 $ / shares £ / shares	Dec. 31, 2022 £ / shares	Dec. 31, 2021 £ / shares
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding at January 1	8,297,694	8,297,694	8,923,600	8,923,600
Options over ADR Number granted during the year | shares	0	0
Options over ADR Number forfeited during the year	(423,164)	(423,164)	(625,906)	(625,906)
Outstanding at December 31	7,874,530	7,874,530	8,297,694	8,297,694
Options over ADR Number exercisable at December 31	7,874,530	7,874,530	8,297,694	8,297,694	7,874,530	8,297,694
WAEP options outstanding at beginning of the year | £ / shares		£ 1.31		£ 1.32
WAEP options forfeited during the year | £ / shares		1.55		1.29
WAEP options outstanding at December 31 | £ / shares		£ 1.46		£ 1.31
WAEP options exercisable at December 31 | £ / shares					£ 1.46	£ 1.31
2019 Equity Incentive Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding at January 1	3,943,702	3,943,702	1,567,873	1,567,873
Options over ADR Number granted during the year	4,126,400	4,126,400	2,696,960	2,696,960
Options over ADR Number cancelled during the year	(1,164,197)	(1,164,197)	(253,277)	(253,277)
Options over ADR Number forfeited during the year	(48,044)	(48,044)	(28,521)	(28,521)
Options over ADR Number exercised during the year	0	0	(39,333)	(39,333)
Outstanding at December 31	6,857,861	6,857,861	3,943,702	3,943,702
Options over ADR Number exercisable at December 31	2,082,027	2,082,027	727,698	727,698	2,082,027	727,698
WAEP options outstanding at beginning of the year	$ 2.88		$ 2.94
WAEP options granted during the year	1.38		2.83
WAEP options cancelled during the year	1.83		2.66
WAEP options forfeited during the year	3.97		5.37
WAEP options exercised during the year	0		2.11
WAEP options outstanding at December 31	2.15		2.88
WAEP options exercisable at December 31	$ 2.95	£ 2.95	$ 3.16	£ 3.16
2019 Non-Executive Director Equity Incentive Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding at January 1	421,791	421,791	149,416	149,416
Options over ADR Number granted during the year	535,488	535,488	296,000	296,000
Options over ADR Number cancelled during the year	(42,192)	(42,192)	(23,625)	(23,625)
Options over ADR Number forfeited during the year	0	0
Options over ADR Number exercised during the year	0	0
Outstanding at December 31	915,087	915,087	421,791	421,791
Options over ADR Number exercisable at December 31	832,584	832,584	386,623	386,623	832,584	386,623
WAEP options outstanding at beginning of the year	$ 2.9		$ 3.06
WAEP options granted during the year	1.22		2.81
WAEP options cancelled during the year	1.01		2.72
WAEP options outstanding at December 31	2		2.9
WAEP options exercisable at December 31	$ 2.09	£ 2.09	$ 2.91	£ 2.91
2019 Non-Executive Director Equity Incentive Plan [member] | Deferred RSUs [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options over ADR Number granted during the year	386,144	386,144
Options over ADR Number cancelled during the year	(42,104)	(42,104)
Options over ADR Number forfeited during the year	0	0
Options over ADR Number exercised during the year	0	0
Outstanding at December 31	344,040	344,040
Mereo BioPharma Group plc Share Option Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding at January 1	1,323,965	1,323,965	1,411,395	1,411,395
Options over ADR Number forfeited during the year	(770,805)	(770,805)	(87,430)	(87,430)
Outstanding at December 31	553,160	553,160	1,323,965	1,323,965
Options over ADR Number exercisable at December 31	553,160	553,160	1,323,965	1,323,965	553,160	1,323,965
WAEP options outstanding at beginning of the year | £ / shares		£ 3.04		£ 3.14
WAEP options forfeited during the year | £ / shares		3.32		3.11
WAEP options outstanding at December 31 | £ / shares		£ 3.49		£ 3.04
WAEP options exercisable at December 31 | £ / shares					£ 3.49	£ 3.04

Share-based Payments - Summar_2

Share-based Payments - Summary of Weighted Average Inputs to the Models Used for the Fair Value of Share Options Granted (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
2019 Equity Incentive Plan [member]
Disclosure of classes of share capital [line items]
Expected volatility (%)	96%	97%
Risk-free interest rate (%)	1.83%	1.15%
Expected life of share options (years)	10 years	10 years
Market price of ADS's ($)	$ 1.38	$ 2.83
Model used	Black-scholes	Black-scholes
2019 Non-Executive Director Equity Incentive Plan [member]
Disclosure of classes of share capital [line items]
Expected volatility (%)	96%	98%
Risk-free interest rate (%)	1.96%	1.09%
Expected life of share options (years)	10 years	10 years
Market price of ADS's ($)	$ 1.22	$ 2.81
Model used	Black-scholes	Black-scholes

Share-based Payments - Summar_3

Share-based Payments - Summary of Number and Movements in Long Term Incentive Plan Options (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding at January 1	8,297,694	8,923,600
Outstanding at December 31	7,874,530	8,297,694
Exercisable at December 31	7,874,530	8,297,694
Long-term incentive plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Outstanding at January 1	0	482,748
Lapsed during the year	0	(482,748)
Outstanding at December 31	0	0
Exercisable at December 31	0	0

Related Party Disclosures - Add

Related Party Disclosures - Additional Information (Detail) - GBP (£)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disclosure of transactions between related parties [line items]
Amount paid to trust by the company	£ 0	£ 0
Shares purchased by the EBT	0	0
ADS [Member]
Disclosure of transactions between related parties [line items]
Cash held by employee benefit trust	£ 17,741	£ 17,866
Total number of American Depository Shares used to exercise options by EBT	200,606	216,251
ADS [Member] | Share Based Incentive Scheme [Member]
Disclosure of transactions between related parties [line items]
Total number of American Depository Shares used to exercise options by EBT	15,645	31,205

Related Party Disclosures - Sum

Related Party Disclosures - Summary Of Compensation of key management personnel of the Group (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure of transactions between related parties [abstract]
Short-term benefits	£ 3,699	£ 4,018	£ 4,479
Post-employment benefits	158	173	144
Share-based payment charge	3,043	2,559	875
Total	£ 6,900	£ 6,750	£ 5,498

Events after the reporting pe_2

Events after the reporting period - Additional Information (Detail) - $ / shares		12 Months Ended
	Feb. 10, 2023	Dec. 31, 2022
Statement [line items]
Borrowings maturity		June 30, 2023
Number of warrants issued		1,101,683
Novartis [member] | Major ordinary share transactions [member]
Statement [line items]
Borrowings maturity	February 10, 2025
Number of warrants issued	2,000,000
Number of warrants issued per share	$ 0.15