NuCana (NCNA) 20-F 20 Mar 24 2023 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2023 shares
Document Information [Line Items]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	NCNA
Entity Registrant Name	NUCANA PLC
Entity Central Index Key	0001709626
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding	52,860,335
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	American Depositary Shares, each representing one Ordinary Share, nominal value £0.04 per share
Security Exchange Name	NASDAQ
Entity File Number	001-38215
Entity Incorporation, State or Country Code	X0
Entity Address, Address Line One	NuCana plc
Entity Address, Address Line Two	3 Lochside Way
Entity Address, City or Town	Edinburgh
Entity Address, Country	GB
Document Annual Report	true
Document Transition Report	false
Entity Address, Postal Zip Code	EH12 9DT
Document Accounting Standard	International Financial Reporting Standards
Document Registration Statement	false
Document Shell Company Report	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	false
Auditor Name	Ernst & Young LLP
Auditor Firm ID	1438
Auditor Location	Edinburgh, United Kingdom
Business Contact
Document Information [Line Items]
Contact Personnel Name	Hugh S. Griffith
Entity Address, Address Line One	NuCana plc
Entity Address, Address Line Two	3 Lochside Way
Entity Address, City or Town	Edinburgh
Entity Address, Country	GB
Local Phone Number	357 1111
City Area Code	131
Entity Address, Postal Zip Code	EH12 9DT

Consolidated Statements of Oper

Consolidated Statements of Operations - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Profit or loss [abstract]
Research and development expenses	£ (25,062)	£ (36,426)	£ (36,834)
Administrative expenses	(6,063)	(7,291)	(8,529)
Impairment of intangible assets	(503)	(292)	(2,809)
Net foreign exchange gains (losses)	(1,156)	4,887	267
Operating loss	(32,784)	(39,122)	(47,905)
Finance income	754	669	103
Loss before tax	(32,030)	(38,453)	(47,802)
Income tax credit	4,398	6,432	7,269
Loss for the year attributable to equity holders of the Company	£ (27,632)	£ (32,021)	£ (40,533)
Basic loss per share	£ (0.53)	£ (0.61)	£ (0.78)
Diluted loss per share	£ (0.53)	£ (0.61)	£ (0.78)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of comprehensive income [abstract]
Loss for the year	£ (27,632)	£ (32,021)	£ (40,533)
Items that may be reclassified subsequently to profit or loss:
Exchange differences on translation of foreign operations	(41)	61	5
Other comprehensive (expense) income for the year	(41)	61	5
Total comprehensive loss for the year	(27,673)	(31,960)	(40,528)
Attributable to:
Equity holders of the Company	£ (27,673)	£ (31,960)	£ (40,528)

Consolidated Statements of Fina

Consolidated Statements of Financial Position - GBP (£) £ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Non-current assets
Intangible assets	£ 2,128	£ 2,365
Property, plant and equipment	521	866
Deferred tax asset	143	103
Total non-current assets	2,792	3,334
Current assets
Prepayments, accrued income and other receivables	2,671	3,957
Current income tax receivable	5,123	6,367
Other assets		2,684
Cash and cash equivalents	17,225	41,912
Total current assets	25,019	54,920
Total assets	27,811	58,254
Capital and reserves
Share capital and share premium	143,420	143,203
Other reserves	79,173	75,872
Accumulated deficit	(207,706)	(180,573)
Total equity attributable to equity holders of the Company	14,887	38,502
Non-current liabilities
Provisions	58	46
Lease liabilities	190	396
Total non-current liabilities	248	442
Current liabilities
Trade payables	3,375	4,803
Payroll taxes and social security	155	162
Accrued expenditure	8,940	10,002
Lease liabilities	206	243
Provisions		4,100
Total current liabilities	12,676	19,310
Total liabilities	12,924	19,752
Total equity and liabilities	£ 27,811	£ 58,254

Consolidated Statements Of Chan

Consolidated Statements Of Changes In Equity - GBP (£) £ in Thousands	Total	Share Capital [member]	Share Premium [member]	Own Share Reserve [member]	Share Option Reserve [member]	Foreign Currency Translation Reserve [member]	Capital Reserve [member]	Accumulated Deficit [member]
Beginning balance at Dec. 31, 2020	£ 99,230	£ 2,047	£ 140,890	£ (339)	£ 24,782	£ (22)	£ 42,466	£ (110,594)
Loss for the year	(40,533)							(40,533)
Other comprehensive income (expense) for the year	5					5
Total comprehensive loss for the year	(40,528)					5		(40,533)
Share-based payments	6,664				6,664
Exercise of share options	182	40	160		(1,222)			1,204
Lapse of share options					(197)			197
Ending balance at Dec. 31, 2021	65,548	2,087	141,050	(339)	30,027	(17)	42,466	(149,726)
Loss for the year	(32,021)							(32,021)
Other comprehensive income (expense) for the year	61					61
Total comprehensive loss for the year	(31,960)					61		(32,021)
Share-based payments	4,890				4,890
Exercise of share options	24	8	58		(362)			320
Lapse of share options					(854)			854
Ending balance at Dec. 31, 2022	38,502	2,095	141,108	(339)	33,701	44	42,466	(180,573)
Loss for the year	(27,632)							(27,632)
Other comprehensive income (expense) for the year	(41)					(41)
Total comprehensive loss for the year	(27,673)					(41)		(27,632)
Share-based payments	3,857				3,857
Exercise of share options	(12)	3	1		(277)			261
Lapse of share options					(238)			238
Issue of share capital	249	16	233
Share issue expenses	(36)		(36)
Ending balance at Dec. 31, 2023	£ 14,887	£ 2,114	£ 141,306	£ (339)	£ 37,043	£ 3	£ 42,466	£ (207,706)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Loss for the year	£ (27,632)	£ (32,021)	£ (40,533)
Adjustments for:
Income tax credit	(4,398)	(6,432)	(7,269)
Amortization, depreciation and loss on disposal	575	732	942
Impairment of intangible assets	503	292	2,809
Movement in provisions	(4,109)	4,100
Finance income	(754)	(669)	(103)
Interest expense on lease liabilities	29	21	18
Share-based payments	3,857	4,890	6,664
Net foreign exchange losses (gains)	1,176	(5,014)	(335)
Cash flows from (used in) operations before changes in working capital	(30,753)	(34,101)	(37,807)
Movements in working capital:
Decrease in prepayments, accrued income and other receivables	1,234	307	473
(Decrease) increase in trade payables	(1,428)	2,974	(428)
(Decrease) increase in payroll taxes, social security and accrued expenditure	(1,087)	442	4,050
Movements in working capital	(1,281)	3,723	4,095
Cash used in operations	(32,034)	(30,378)	(33,712)
Net income tax received	5,595	7,220	9,888
Net cash used in operating activities	(26,439)	(23,158)	(23,824)
Cash flows from investing activities
Interest received	770	638	101
Payments for property, plant and equipment	(4)	(12)	(64)
Payments for intangible assets	(474)	(506)	(1,001)
Repayment (payment) of other assets	2,596		(2,597)
Net cash from (used in) investing activities	2,888	120	(3,561)
Cash flows from financing activities
Payments of lease liabilities	(270)	(227)	(296)
Proceeds from issue of share capital - exercise of share options	4	66	198
Proceeds from issue of share capital	249
Share issue expenses	(36)
Net cash used in financing activities	(53)	(161)	(98)
Net decrease in cash and cash equivalents	(23,604)	(23,199)	(27,483)
Cash and cash equivalents at beginning of year	41,912	60,264	87,356
Effect of exchange rate changes on cash and cash equivalents	(1,083)	4,847	391
Cash and cash equivalents at end of year	£ 17,225	£ 41,912	£ 60,264

General Information

General Information	12 Months Ended
	Dec. 31, 2023
Disclosure Of General Information About Financial Statements [Abstract]
General information	1. General i nformation NuCana plc (“NuCana” or the “Company”) is a clinical-stage biopharmaceutical company developing a portfolio of new medicines to treat patients with cancer . NuCana is harnessing the power of phosphoramidate chemistry to generate new medicines called ProTides. These compounds have the potential to improve cancer treatment by enhancing the efficacy and safety of several current standards of care. The Company has had American Depository Shares (“ADSs”) registered with the US Securities and Exchange Commission (“SEC”) and has been listed on Nasdaq since October 2, 2017. From November 9, 2023 the Company transferred its listing to The Nasdaq Capital Market. The Company is incorporated in England and Wales and domiciled in the United Kingdom . The Company’s registered office is located at 77/78 Cannon Street, London EC4N 6AF, United Kingdom and its principal place of business is located at 3 Lochside Way, Edinburgh, EH12 9DT, United Kingdom. The Company has three wholly owned subsidiaries, NuCana Limited, NuCana, Inc. and NuCana BioMed Trustee Company Limited . The financial statements for the Company were authorized for issue by the board of directors on March 20, 2024.

Material Accounting Policies

Material Accounting Policies	12 Months Ended
	Dec. 31, 2023
Disclosure Of Summary Of Material Accounting Policies [Abstract]
Material accounting policies	2. Material accounting policies Basis of preparation The financial statements have been prepared in conformity with International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standards Board (“IASB”) and in conformity with U.K. adopted international accounting standards. The Company’s financial statements comprise the financial statements of the Company and its subsidiaries at December 31, 2023. The financial statements are presented in pounds sterling, which is also the Company’s functional currency. All values are rounded to the nearest thousand, except where otherwise indicated. Going concern The Company’s consolidated financial statements have been presented on the basis that it is a going concern. The Company has not generated any revenues from operations to date and does not expect to in the foreseeable future. As such, the Company has incurred recurring net losses, has an accumulated deficit totaling £ 207.7 million and cash flows used in operating activities of £ 26.4 million for the year ended December 31, 2023. The Company had £ 17.2 million of cash and cash equivalents at December 31, 2023. In reviewing the going concern assessment the Company’s board of directors have considered a going concern period of 12-months from the issuance of these financial statements. Based on our current operating plan, our cash and cash equivalents on hand will not be sufficient to fund our anticipated operations for the entirety of the going concern assessment period. As the Company intends to continue to progress its research and development activities, there will be a requirement to seek additional capital within the going concern period to fund operations, which the Company may obtain from additional equity financings, debt financings or other sources. If the Company is unable to obtain additional capital, the Company will be required to delay or reduce its research and development programs which could negatively impact its ability to generate future sustainable operating revenues and profits. As a result of these matters, there is uncertainty related to the ability of the Company to raise sufficient additional capital within the going concern period, prior to its cash balances being exhausted. These events or conditions raise substantial doubt about the Company’s ability to continue as a going concern and, therefore, that the Company may be unable to realize its assets and discharge its liabilities in the normal course of business. The consolidated financial statements do not include any adjustments that might result from the outcome of this uncertainty. 2. Material accounting policies (continued) Judgements and estimates The preparation of the financial statements requires management to make judgements, estimates and assumptions that affect the amounts reported for assets and liabilities at the balance sheet dates and the amounts reported for revenue and expenses during the year. The nature of estimations means that actual outcomes could differ from those estimates. The following judgements have had the most material effect on the amounts recognized in the financial statements: Research and development expenses The Company recognizes research and development expenses in the statement of operations in the period in which they are incurred. When development activities reach the advanced stage, as set out in the specific criteria of International Accounting Standard (“IAS”) 38, Intangible Assets , there will be a requirement to capitalize such costs as intangible assets. Management will continue to exercise judgement in the appropriate treatment of research and development costs. Taxation Management judgement is required to determine the amount of deferred tax assets that should be recognized, based upon the likely timing and level of future taxable profits. Further details are contained in Note 7. The following estimates have had the most material effect on the amounts recognized in the financial statements: Recognition of clinical trial expenses As part of the process of preparing our consolidated financial statements, we may be required to estimate accrued or prepaid expenses related to our clinical trials. In order to obtain reasonable estimates, we review open contracts and master service agreements. In addition, we communicate with applicable personnel in order to identify services that have been performed, but for which we have not yet been invoiced, and services not yet performed for which we have been invoiced in advance. In most cases, our vendors provide us with monthly invoices in arrears for services performed. The following are examples of our accrued expenses: • fees paid to CROs for services performed on clinical trials; and • pass-through costs for activities at clinical trial investigator sites. Accruals for clinical trial expenses, including estimated amounts recognized consistent with the above policy, were £ 6.2 million at December 31, 2023 as compared to £ 6.6 million at December 31, 2022. This includes accruals for investigator fees of £ 4.8 million at December 31, 2023 as compared to £ 4.2 million at December 31, 2022. Prepayments for clinical trial expenses, including estimated amounts recognized consistent with the above policy, were £ 1.0 million at December 31, 2023 as compared to £ 1.8 million at December 31, 2022. These amounts include sums that are expected to be utilized over the period of the associated trials, which in some cases could be greater than one year. Recognition of contracted manufacturing expenses As part of the process of preparing our consolidated financial statements, we may be required to estimate accrued or prepaid expenses related to our contracted manufacturing expenses. In order to obtain reasonable estimates, we review open contracts and master service agreements. In addition, we consult with applicable personnel in order to identify services that have been performed and which have not yet been invoiced, and services not yet performed for which we have been invoiced in advance. Accruals for contracted manufacturing expenses, including estimated amounts recognized consistent with the above policy, were £ 0.4 million at December 31, 2023 as compared to £ 0.4 million at December 31, 2022. Prepayments for contracted manufacturing expenses, including estimated amounts recognized consistent with the above policy, were £ 41,000 at December 31, 2023 as compared to £ 0.1 million at December 31, 2022. 2. Material accounting policies (continued) Share-based payments Estimating fair value for share-based payment transactions requires determination of the most appropriate valuation model, which depends on the terms and conditions of the grant. This estimate also requires determination of the most appropriate inputs to the valuation model, including the expected life of the share option, historical volatility of the share price, dividend yield and assumptions about them, and the actual market value of an ordinary share in the Company at the date of grant. For the measurement of the fair value of equity-settled transactions at the grant date, the Company uses the Black-Scholes model. The assumptions used for estimating fair value for share-based payment transactions are detailed in Note 14. Legal proceedings The Company may be party to a number of litigation and other legal proceedings. The Company recognizes a provision for any cost reimbursement due to other parties involved in the legal proceedings if a legal or constructive obligation as a result of a past event exists at the balance sheet date, it is probable that an outflow of economic resources will be required to settle the obligation, and a reasonable estimate can be made of the amount of the obligation, even although the timing or amount of the liability is uncertain. The final amount of any cost reimbursement may be materially different to management’s estimate. Similarly, the Company recognizes an asset for any settlement or cost reimbursement in relation to the legal proceedings due to the Company if it is virtually certain that the income will be received. Where an outflow of economic resources is not probable or an inflow of economic resources is not virtually certain, the Company will disclose a contingent liability or contingent asset, respectively. As of December 31, 2023, the Company had a provision of £ nil (2022: £ 4.1 million) with respect to legal proceedings. Basis of consolidation The consolidated financial statements comprise the financial statements of the Company and its subsidiaries. Subsidiaries are consolidated from the date on which the Company obtains control, and continue to be consolidated until the date when such control ceases. The financial statements of the subsidiaries are prepared for the same reporting period as the parent company, using consistent accounting policies. All intra-group balances, transactions, unrealized gains and losses resulting from intra-group transactions and dividends are eliminated in full. Assets, liabilities, income and expenses of a subsidiary acquired or disposed of during the year are included in the consolidated financial statements from the date the Company gains control until the date the Company ceases to control the subsidiary. Foreign currencies The Company’s consolidated financial statements are presented in pounds sterling, which is also the parent company’s functional currency. For each group entity, the Company determines the functional currency and items included in the financial statements of each entity are measured using that functional currency. Transactions and balances Transactions in foreign currencies are initially recorded by the Company’s entities at their respective functional currency spot rates of exchange at the date the transaction first qualifies for recognition. Monetary assets and liabilities denominated in foreign currencies are translated at the functional currency spot rates of exchange at the reporting date. Differences arising on settlement or translation of monetary items are recognized in the consolidated statements of operations. 2. Material accounting policies (continued) Non-monetary items that are measured in terms of historical cost in a foreign currency are translated using the exchange rates at the dates of the initial transactions. Group companies On consolidation, the assets and liabilities of foreign operations are translated into pounds sterling at the rate of exchange prevailing at the reporting date and their statements of operations are translated at the average exchange rate for the financial period in which those transactions occur. The exchange differences arising on translation for consolidation are recognized in the consolidated statements of comprehensive income or loss. Segment reporting The Company operates in one operating segment. Operating segments are reported in a manner consistent with the internal reporting provided to the Company’s chief operating decision maker (“the CODM”). The Company’s CODM, its Chief Executive Officer, views the Company’s operations and manages its business as a single operating segment, which is the business of developing and commercializing ProTides for use in Oncology. The Company’s principal operations and decision-making functions are located in the United Kingdom from where global decisions are made. Share issue expenses Incremental costs incurred and directly attributable to the issuance of shares are deducted from the related proceeds of the issuance. The net amount is recorded as contributed shareholders’ equity in the period when such shares are issued. Costs that are not incremental and directly attributable to issuing new shares, are recorded as an expense in the consolidated statements of operations. Property, plant and equipment Property, plant and equipment is stated at cost, net of accumulated depreciation and accumulated impairment losses, if any. There are no restrictions on title to assets nor equipment pledged as security for liabilities. Depreciation is provided on property, plant and equipment over their expected useful economic life as follows: Asset class Depreciation method and period Office and computer equipment Straight-line over 3 years Fixtures and fittings Straight-line over 5 years , or, for non-removable items, the remaining term of an associated lease, whichever is shorter Right of use assets Straight-line over the lease terms, which are between two and five years , or the estimated useful lives of the assets, whichever is shorter Intangible assets Intangible assets are stated at cost, net of accumulated amortization and accumulated impairment losses, if any. Cost in relation to patents includes registration, documentation and other legal fees associated with obtaining the patent. Computer software cost represents the initial purchase price of the asset. The amortization method and amortization period for the principal categories of intangible assets are follows: Asset class Amortization method and period Patents Straight-line over 20 years Computer software Straight-line between 3 and 5 years 2. Material accounting policies (continued) The Company’s primary patents each have a life of 20 years. Further patents are granted in various jurisdictions to extend the territorial coverage of the primary patent. These patents are granted up to the period of the related primary patent. Costs are amortized over the remaining life of the relevant primary patent. The amortization expense on intangible assets with finite lives is recognized in the statements of operations as an administrative expense. The amortization method and the amortization period for an intangible asset with a finite useful life are reviewed at least at each financial year end. Changes in the expected useful economic life or the expected pattern of consumption of future economic benefits embodied in the asset are accounted for by changing the amortization period or method, as appropriate. Intangible assets are tested for impairment when there is an indicator of impairment. Cash and cash equivalents Cash and cash equivalents in the statement of financial position include cash at banks with deposit maturity terms of three months or less . Research and development Research and development expenses are recognized in the statement of operations in the year in which they are incurred. Development expenditures on an individual project will be recognized as an intangible asset when the Company can demonstrate: • the technical feasibility of completing the intangible asset so that the asset will be available for use or sale; • its intention to complete and its ability and intention to use or sell the asset; • how the asset will generate future economic benefits; • the availability of resources to complete the asset; and • the ability to measure reliably the expenditure during development. Income Taxes 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. The tax rates and tax laws used to compute the amounts are those that are enacted or substantively enacted at the reporting date in the countries where the Company operates within the tax regime. 2. Material accounting policies (continued) Income tax credit The Company benefits from the U.K. and U.S. research and development tax credit regimes. In the United Kingdom, a portion of the Company’s losses can be surrendered for a cash rebate of up to 26.97 % of eligible expenditures incurred on or after April 1, 2023 ( 33.35 % prior to April 1, 2023). In the U.S. the Company is able to offset the research and development credits against corporation tax payable. Such credits are accounted for within the tax provision in the year in which the expenditures are incurred. Leases The Company assesses, at contract inception, whether a contract is, or contains, a lease. That is, if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company applies a single recognition and measurement approach for all leases, except for short-term leases and leases of low-value assets. The Company recognizes lease liabilities to make lease payments and right of use assets representing the right to use the underlying assets. Right of use assets The Company recognizes right of use assets at the commencement date of the lease (i.e. the date the underlying asset is available for use). Right of use assets are measured at cost, less any accumulated depreciation and impairment losses, and adjusted for any remeasurement of lease liabilities. The cost of right of use assets includes the amount of lease liabilities recognized, initial direct costs incurred, and lease payments made at or before the commencement date less any lease incentives received. Right of use assets, which relate solely to office space, are depreciated on a straight-line basis over the shorter of the lease terms, which are between two and five years , or the estimated useful lives of the assets. Lease liability At the commencement date of the lease, the Company recognizes a lease liability measured at the present value of lease payments to be made over the lease term. The lease payments include fixed payments less any lease incentives receivable, and any variable lease payments that depend on an index. In calculating the present value of lease payments, the Company uses its incremental borrowing rate at the lease commencement date because the interest rate implicit in the lease is not readily determinable. After the commencement date, the amount of the lease liability is increased to reflect the accretion of interest and reduced for the lease payments made. In addition, the carrying amount of the lease liability is remeasured if there is a modification, a change in the lease term or a change in the lease payments. The Company determines the lease term as the non-cancellable term of the lease, together with any periods covered by an option to extend the lease if it is reasonably certain to be exercised, or any periods covered by an option to terminate the lease, if it is reasonably certain not to be exercised. The Company has a number of lease contracts that include extension and termination options. The Company applies judgement in evaluating whether it is reasonably certain whether or not to exercise the option to renew or terminate the lease. That is, it considers all relevant factors that create an economic incentive for it to exercise either the renewal or termination. After the commencement date, the Company reassesses the lease term if there is a significant event or change in circumstances that is within its control and affects its ability to exercise or not to exercise the option to renew or to terminate, such as the construction of significant leasehold improvements. Refer to Note 15 for information on potential future rental payments relating to periods following the exercise date of extension options that are not included in the lease liability. Provisions Provisions are recognized when either a legal or constructive obligation as a result of a past event exists at the balance sheet date, it is probable that an outflow of economic resources will be required to settle the obligation and a reasonable estimate can be made of the amount of the obligation, even although the timing or amount of the liability is uncertain. 2. Material accounting policies (continued) Impairment of non-financial assets The Company assesses, at each reporting date, whether there is an indication that an asset may be impaired. If any indication exists, the Company estimates the recoverable amount of the asset. An impairment loss is recognized whenever the carrying amount of an asset or its cash-generating unit exceeds its recoverable amount. Impairment losses are recognized in the consolidated statements of operations. A cash-generating unit is the smallest identifiable group of assets that generates cash inflows that are largely independent of the cash inflows from other assets or groups of assets. Calculation of recoverable amount The recoverable amount of assets and cash-generating units is the higher of their fair value less costs to sell and value in use. In assessing value in use, the estimated future cash flows are discounted to their present value using a pre-tax discount rate that reflects current market assessments of the time value of money and the risks specific to the asset. For an asset that does not generate largely independent cash inflows, the recoverable amount is determined for the cash-generating unit to which the asset belongs. Reversal of impairment An assessment is made at each reporting date as to whether there is an indication that a previously recognized impairment loss may no longer exist or may have decreased. If such an indication exists, the recoverable amount is estimated. A previously recognized impairment loss is reversed only if there has been a change in the estimates used to determine the recoverable amount since the last impairment loss was recognized. If that is the case, the carrying value is increased to its recoverable amount. An impairment loss is reversed only to the extent that the asset’s carrying amount does not exceed the carrying amount that would have been determined, net of depreciation or amortization, if no impairment loss had been recognized. Share-based payments Employees, directors and consultants of the Company receive remuneration in the form of share options, whereby individuals render services as consideration for equity instruments and the cost is recognized as share-based payments under IFRS 2. Under IFRS 2 Share-based Payment , equity share-based payments are measured at the fair value of the equity instruments at the grant date. Details regarding the determination of fair value of equity settled share-based transactions are set out in Note 14. The fair value determined at the grant date of equity settled share-based payments, after adjusting for an assumed forfeiture rate, is expensed on a straight-line basis over the vesting period, with a corresponding increase in equity to the share option reserve. 2. Material accounting policies (continued) Fair value measurement The fair value of the financial assets and liabilities is included at the amount at which an instrument could be exchanged in a current transaction between willing parties, other than in a forced liquidation or sale. Fair value is based on the price that would be received from the sale of an asset or that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. In order to increase consistency and comparability in fair value measurements, IFRS 13 establishes a fair value hierarchy that prioritizes observable and unobservable inputs used to measure fair value into three broad levels, which are described as follows: Level 1: Quoted (unadjusted) prices in active markets for identical assets or liabilities. Level 2: Other techniques for which all inputs that have a significant effect on the recorded fair value are observable, either directly or indirectly. Level 3: Techniques that use inputs that have a significant effect on the recorded fair value that are not based on observable market data. The fair values of cash and cash equivalents, other receivables, and trade payables approximate their carrying amounts largely due to the short-term maturities of these instruments. Accounting Standards In preparing these financial statements, the Company has applied all relevant IAS, IFRS and International Financial Reporting Interpretations Committee (“IFRIC”) Interpretations as of the date of approval of these financial statements and which are mandatory for the financial year ended December 31, 2023. The following amendments have been adopted as of January 1, 2023 in these financial statements: • IFRS 17 Insurance Contracts (effective from January 1, 2023) • Amendments to IAS 1 Presentation of Financial Statements and IFRS Practice Statement 2 – Disclosure of Accounting Policies (effective from January 1, 2023) • Amendments to IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors – Definition of Accounting Estimates (effective from January 1, 2023) • Amendments to IAS 12 Deferred Tax related to Assets and Liabilities arising from a Single Transaction (effective from January 1, 2023) • Amendments to IAS 12 International Tax Reform - Pillar Two Model Rules (effective from January 1, 2023) 2. Material accounting policies (continued) The Company concluded that these have not had a material impact on the Company’s accounts in the period of initial application, but may impact the accounting for future transactions. The IASB and IFRIC have issued the following standards and amendments with an effective date after the date of these financial statements: • Amendments to IAS 1 Presentation of Financial Statements – Classification of Liabilities as Current or Non-Current (effective from January 1, 2024) • Amendments to IAS 1 Presentation of Financial Statements – Non-Current Liabilities with Covenants (effective from January 1, 2024) • Amendments to IFRS 16 Lease Liability in a Sale and Leaseback (effective from January 1, 2024) • Amendments to IAS 7 and IFRS 7 Supplier Finance Arrangements (effective from January 1, 2024) • Amendments to IAS 21 Lack of Exchangeability (effective from January 1, 2025) The Company will adopt the above standards and amendments on their effective date, although the Company has reviewed the above standards and amendments and considers that they either do not apply to the Company or will not have a material impact in future periods.

Staff Costs

Staff Costs	12 Months Ended
	Dec. 31, 2023
Classes of employee benefits expense [abstract]
Staff costs	3. Staff costs Included in research and development expenses: 2023 2022 2021 (in thousands) £ £ £ Wages and salaries 4,530 4,893 3,931 Social security costs 516 569 465 Pension costs 210 213 189 Share-based payments 2,551 3,125 3,833 7,807 8,800 8,418 Included in administrative expenses: 2023 2022 2021 (in thousands) £ £ £ Wages and salaries 1,500 1,587 1,407 Social security costs 160 155 136 Pension costs 46 46 40 Share-based payments 1,306 1,765 2,831 3,012 3,553 4,414 Total employee benefit expense 10,819 12,353 12,832 The average number of staff employed under contracts of service were: 2023 2022 2021 (number) Research and development activities 23 26 25 Administrative activities 6 7 5 29 33 30 Directors’ remuneration & other benefits 2023 2022 2021 (in thousands) £ £ £ Directors’ remuneration 1,216 1,290 1,149 Pension and other benefits 61 57 57 1,277 1,347 1,206 The number of directors who exercised share options in 2023 was 2 (2022: 3 ; 2021: 3 ). The gain on exercise of these options was £ 8,000 (2022: £ 48,000 ; 2021: £ 0.7 million). 3. Staff costs (continued) The above amounts for remuneration include the following in respect of the highest paid director: 2023 2022 2021 (in thousands) £ £ £ Directors’ remuneration 913 966 850 Pension and other benefits 61 57 57 974 1,023 907

Basic and Diluted Loss Per Shar

Basic and Diluted Loss Per Share	12 Months Ended
	Dec. 31, 2023
Earnings per share [abstract]
Basic and diluted loss per share	4. Basic and diluted loss per share 2023 2022 2021 (in thousands, except per share data) £ £ £ Loss for the year ( 27,632 ) ( 32,021 ) ( 40,533 ) Basic and diluted weighted average number of shares 52,573 52,235 52,041 £ £ £ Basic and diluted loss per share ( 0.53 ) ( 0.61 ) ( 0.78 ) Basic loss per share is calculated by dividing the loss for the year attributable to the equity holders of the Company by the weighted average number of shares outstanding during the year. The equity-settled transactions were considered to be anti-dilutive as they would have decreased the loss per share and were therefore excluded from the calculation of diluted loss per share.

Loss Before Tax

Loss Before Tax	12 Months Ended
	Dec. 31, 2023
Material income and expense [abstract]
Loss Before Tax	5. Loss before tax Loss before tax is stated after charging: 2023 2022 2021 (in thousands) £ £ £ Administrative expenses: Amortization 208 239 535 Depreciation 367 473 407

Capital Commitments and Conting

Capital Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Disclosure Of Capital Commitments And Contingencies [Abstract]
Capital commitments and contingencies	6. Capital commitments and contingencies Other commitments Collaboration and License Agreements Cardiff University License In August 2009, we entered into a research, collaboration and license agreement with Cardiff University and University College Cardiff Consultants Ltd., or Cardiff Consultants, which we refer to as the Cardiff Agreement. The Cardiff Agreement was subsequently renewed and expired at the end of March 31, 2022. Prior to the expiration of the Cardiff Agreement, we notified Cardiff University and Cardiff Consultants regarding our selected ProTides for potential development of commercial products. Pursuant to the terms set out in the Cardiff Agreement, Cardiff University and Cardiff Consultants have granted us an exclusive worldwide license to use for all purposes the Cardiff intellectual property in respect of the nucleoside family of our selected ProTides. This license survives expiration of the Cardiff Agreement. During the license period Cardiff University and Cardiff Consultants may not undertake any research for any competing third party on nucleoside families of interest to us where such research would make use of the Cardiff intellectual property, or to grant rights in the Cardiff intellectual property to any third party for use in connection with nucleosides of interest to us. On our filing, or that of a sublicensee, of patent applications resulting from research under the Cardiff Agreement, we will owe Cardiff Consultants certain immaterial payments. If we or our sublicensees develop and commercialize a product resulting from such research, we will owe Cardiff Consultants clinical development milestone payments of up to £ 1,875,000 , provided that such milestone payments are due only with respect to the first product within each nucleoside family to achieve the milestone. We will also owe Cardiff Consultants royalties equal to a low-single digit percentage on our sales of a product resulting from such research. Should we sublicense our right to commercialize a product resulting from the research, we will owe Cardiff Consultants a high-single digit percentage of payments received in consideration of the sublicense. Cardiff ProTides Agreement In October 2009, we entered into a license and collaboration agreement with Cardiff ProTides Ltd., or Cardiff ProTides, which agreement was subsequently amended and restated as an assignment, license and collaboration agreement in March 2012 and was further amended in May 2012, which we refer to as the ProTides Agreement. Under the ProTides Agreement, we collaborated with Cardiff ProTides in the discovery, drug design and in vitro screening of purine and pyrimidine-based nucleosides as potential drug candidates. We funded certain work at Cardiff ProTides, and Cardiff ProTides has assigned to us all rights in the results of its research under the ProTides Agreement. Cardiff ProTides also assigned to us patents related to certain compounds of interest, including with respect to Acelarin, and granted us an exclusive, worldwide license, including the right to grant sublicenses, to rights in and technical information related to certain unpatented compounds for all therapeutic, diagnostic, prognostic and prophylactic applications. 6. Capital commitments and contingencies (continued) If we or a sublicensee develop one or more products covered by a valid claim of an assigned patent or patent resulting from Cardiff ProTides’ research, such as Acelarin, we will owe Cardiff ProTides up to approximately $ 4.5 million in development and approval milestone payments in the aggregate for the first such product. Additional development and approval milestones would be payable for the first additional product in a new nucleoside series covered by a valid claim of an assigned patent or a patent resulting from Cardiff ProTides’ research, although the maximum potential value of such milestone payments is approximately half the value of the milestone payments associated with the first product. We will also owe Cardiff ProTides royalties equal to a percentage in mid- to high-single digits on sales of such products, subject to reduction under certain circumstances. Royalties on sales by sublicensees are set by formula, which formula would be likely to result in a royalty in the mid-single digits. The ProTides Agreement expires, on a country-by-country basis, on the later of the expiration, invalidity, abandonment, lapsing or rejection of the last valid claim of an assigned patent or patent resulting from Cardiff ProTides’ research, or, if certain technical information licensed from Cardiff ProTides remains confidential or the product is covered by a period of data exclusivity, ten years from the date of first commercial sale of a product in such country. The ProTides Agreement may be sooner terminated on an uncured material breach, bankruptcy of a party or, by Cardiff ProTides, if we challenge, or assist in a challenge, of the validity or ownership of an assigned patent or patent resulting from Cardiff ProTides’ research, or fail to pay amounts payable under the ProTides Agreement. It may also be sooner terminated where sums payable by us remain unpaid for 45 days after we receive a notice from Cardiff ProTides that the relevant sums are overdue. Upon a termination of the ProTides Agreement, our license rights will terminate except where the breach results from certain breaches by Cardiff ProTides, in which case our license rights continue on a non-exclusive basis, subject to reduced payment obligations. Upon termination of the ProTides Agreement, including as a result of our breach, we will be under an obligation to assign back to Cardiff ProTides the patents which Cardiff ProTides originally assigned to us. CROs and manufacturing commitments We have agreed to make payments to CROs and manufacturers under various CRO and manufacturing agreements. We have not included further details on such contingent payment obligations as the amount, timing and likelihood of such payments are not fixed or determinable. Other contingent liabilities Under the U.K. share-based payment plan, the Company granted unapproved share options that have fully vested. If and when these share options are exercised, the Company will be liable for the Employer Class 1 National Insurance payable to HMRC in the U.K. This contingent liability will be determined based on the market value of the shares on exercise less the exercise price paid by the option holders, at the prevailing rate of Employer National Insurance (currently 13.8 %). Based on the closing share price of ADSs on the Nasdaq Capital Market on December 29, 2023, the last trading day of the period to which these financial statements relate, and assuming full exercise of all outstanding and vested unapproved share options on that date, the Employer National Insurance contingent liability would have been £ 0.1 million (December 31, 2022: £ 0.1 million).

Income Tax Credit

Income Tax Credit	12 Months Ended
	Dec. 31, 2023
Major components of tax expense (income) [abstract]
Income tax credit	7. Income tax credit The major components of income tax for the years ended December 31, 2023, 2022 and 2021 are as follows: 2023 2022 2021 (in thousands) £ £ £ Current tax: In respect of current year U.K. 4,558 6,366 7,185 In respect of current year U.S. ( 1 ) ( 3 ) — In respect of prior years U.K. ( 206 ) 35 69 Total current tax 4,351 6,398 7,254 Deferred tax: In respect of current year U.S. 48 34 15 In respect of prior years U.S. ( 1 ) — — Total deferred tax 47 34 15 Income tax credit 4,398 6,432 7,269 Current income tax receivable: U.K. tax 5,121 6,366 7,185 U.S. tax 2 1 3 Current income tax receivable 5,123 6,367 7,188 Deferred tax: U.S. tax 143 103 60 7. Income tax credit (continued) The credit for the year can be reconciled to the loss per the statement of operations as follows: 2023 2022 2021 (in thousands) £ £ £ Loss before tax ( 32,030 ) ( 38,453 ) ( 47,802 ) Tax on loss at standard U.K. tax rate of 23.52 % (2022: 19 %; 2021: 19 %) ( 7,533 ) ( 7,306 ) ( 9,082 ) Effects of: Expenses not deductible 4,818 4,595 4,757 Deduction for R&D ( 7,394 ) ( 8,342 ) ( 9,415 ) Losses surrendered for R&D tax credit 7,394 8,342 9,415 Deferred tax - prior year adjustment 1 — — Overseas tax payable - current year 1 3 — R&D tax credit - U.S. ( 48 ) ( 34 ) ( 15 ) R&D tax credit - current year ( 4,558 ) ( 6,366 ) ( 7,185 ) R&D tax credit - prior years 206 ( 35 ) ( 69 ) Deferred tax asset not recognized 2,715 2,711 4,325 Income tax credit ( 4,398 ) ( 6,432 ) ( 7,269 ) In the United Kingdom, the Company has not recognized a deferred tax asset in respect of tax losses carried forward or temporary differences on share-based compensation arrangements as at December 31, 2023 on the basis that the timing during which tax losses or temporary differences could be regarded as recoverable against future taxable profits cannot be determined with reasonable certainty. In the United States, a deferred tax asset, which relates to research and development tax credits, has been recognized to the extent that management consider that adequate future taxable profits will be available to realize the deferred tax asset. Temporary differences and cumulative carry forward tax losses for which deferred tax has not been recognized amount to £ 99.1 million (2022: £ 85.9 million; 2021: £ 74.4 million), comprising temporary differences on share-based compensation arrangements of £ 0.6 million (2022: £ 1.3 million; 2021: £ 4.1 million) and cumulative carry forward tax losses of £ 98.5 million (2022: £ 84.6 million; 2021: £ 70.3 million). From April 1, 2023 the U.K. corporation tax rate increased from 19 % to 25 % for U.K. companies with annual profits of £ 250,000 or higher, which was substantively enacted on May 24, 2021 and meant the standard U.K. tax rate was 23.52 % for the year ended December 31, 2023.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about intangible assets [abstract]
Intangible Assets	8. Intangible assets Patents Computer Total (in thousands) £ £ £ Cost: At December 31, 2021 6,784 385 7,169 Additions 506 — 506 Disposals — ( 234 ) ( 234 ) At December 31, 2022 7,290 151 7,441 Accumulated amortization: At December 31, 2021 4,439 320 4,759 Charge for the year 195 44 239 Disposals — ( 214 ) ( 214 ) Impairment 292 — 292 At December 31, 2022 4,926 150 5,076 Cost: At December 31, 2022 7,290 151 7,441 Additions 474 — 474 At December 31, 2023 7,764 151 7,915 Accumulated amortization: At December 31, 2022 4,926 150 5,076 Charge for the year 208 — 208 Impairment 503 — 503 At December 31, 2023 5,637 150 5,787 Net book value: At December 31, 2023 2,127 1 2,128 At December 31, 2022 2,364 1 2,365 The Company regularly reviews its patent portfolio and during 2023 further development associated with a limited number of patents, relating mainly to preclinical drug candidates, was discontinued. Management concluded that this was an indication of impairment and an impairment charge of £ 0.5 million has been recognized, representing the aggregate carrying value of those patents as at December 31, 2023. This compared to an impairment charge of £ 0.3 million recognized as of December 31, 2022 .

Property Plant and Equipment

Property Plant and Equipment	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about property, plant and equipment [abstract]
Property, plant and equipment	9. Property, plant and equipment Right of Office and Fixtures Total (in thousands) £ £ £ £ Cost: At December 31, 2021 1,093 379 715 2,187 Additions — 10 — 10 Re-measurement 483 — — 483 Disposals ( 237 ) ( 34 ) ( 130 ) ( 401 ) Effect of foreign currency exchange differences 17 1 — 18 At December 31, 2022 1,356 356 585 2,297 Depreciation: At December 31, 2021 721 249 366 1,336 Charge for the year 251 56 166 473 Disposals ( 237 ) ( 34 ) ( 130 ) ( 401 ) Effect of foreign currency exchange differences 22 1 — 23 At December 31, 2022 757 272 402 1,431 Cost: At December 31, 2022 1,356 356 585 2,297 Additions — 4 21 25 Re-measurement 4 — — 4 Disposals — ( 10 ) — ( 10 ) Effect of foreign currency exchange differences ( 22 ) ( 1 ) — ( 23 ) At December 31, 2023 1,338 349 606 2,293 Depreciation: At December 31, 2022 757 272 402 1,431 Charge for the year 212 52 103 367 Disposals — ( 10 ) — ( 10 ) Effect of foreign currency exchange differences ( 16 ) — — ( 16 ) At December 31, 2023 953 314 505 1,772 Net book value: At December 31, 2023 385 35 101 521 At December 31, 2022 599 84 183 866

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2022
Disclosure Of Other Assets [Abstract]
Other assets	10. Other assets 2023 2022 (in thousands) £ £ Other assets — 2,684 In April 2021, the Company initiated legal proceedings against Gilead Sciences Ireland UC and Gilead Sciences GmbH in the German Regional Court of Dusseldorf (“RC Dusseldorf”) for patent infringement for the sale of Sovaldi as well as its combination products Harvoni, Vosevi and Epclusa in Germany. Later in 2021, the Company provided a security of € 3.0 million by depositing funds with RC Dusseldorf to cover the legal costs of Gilead Sciences Ireland UC and Gilead Sciences GmbH in the event that the Company was unsuccessful in the final outcome of the patent infringement litigation in Germany. The other assets at December 31, 2022 of £ 2.7 million solely related to the security deposit provided. In May 2023, the Company abandoned all proceedings in Germany and reached a settlement agreement with Gilead Sciences Ireland UC and Gilead Sciences GmbH, as disclosed in Note 19, and as a result, the security deposit was repaid in full in July 2023.

Prepayments, Accrued Income and

Prepayments, Accrued Income and Other Receivables	12 Months Ended
	Dec. 31, 2023
Prepayments Accrued Income And Other Receivables [Abstract]
Prepayments, accrued income and other receivables	11. Prepayments, accrued income and other receivables 2023 2022 (in thousands) £ £ Prepayments - manufacturing and clinical 1,081 1,890 Prepayments - other 888 1,416 Accrued income 21 36 VAT 663 601 Other receivables 18 14 2,671 3,957

Share Capital and Share Premium

Share Capital and Share Premium	12 Months Ended
	Dec. 31, 2023
Disclosure of classes of share capital [abstract]
Share capital and share Premium	12. Share capital and share premium 2023 2022 2021 (in thousands) £ £ £ Share capital 2,114 2,095 2,087 Share premium 141,306 141,108 141,050 143,420 143,203 143,137 Number Number Number (in thousands) Issued share capital comprises: Ordinary shares of £ 0.04 each 52,860 52,373 52,180 52,860 52,373 52,180 Number Share Share (in thousands) £ £ Fully paid shares: Balance at December 31, 2021 52,180 2,087 141,050 Exercise of share options 193 8 58 Balance at December 31, 2022 52,373 2,095 141,108 Exercise of share options 79 3 1 Issue of share capital 408 16 197 Balance at December 31, 2023 52,860 2,114 141,306 Ordinary shares Holders of ordinary shares are entitled to one vote for each share held of record on all matters submitted to a vote of shareholders and do not have cumulative voting rights. Capital management For the purpose of the Company’s capital management, capital includes issued capital, share premium and all other equity reserves attributable to the equity holders of the Company. The purpose of the Company’s capital management is to maximize shareholder value and ensure adequate capital is available to meet the medium-term operating plan. Review of operations and commitments is key to identifying future capital management and a full review is undertaken on a quarterly basis. No changes were made in the objectives, policies or processes for managing capital during the years ended December 31, 2023, 2022 or 2021.

Other Reserves

Other Reserves	12 Months Ended
	Dec. 31, 2023
Disclosure Of Other Reserves [Abstract]
Other reserves	13. Other reserves 2023 2022 2021 (in thousands) £ £ £ Own share reserve ( 339 ) ( 339 ) ( 339 ) Foreign currency translation reserve 3 44 ( 17 ) Capital reserve 42,466 42,466 42,466 Share option reserve Balance at beginning of year 33,701 30,027 24,782 Share-based payments 3,907 5,133 6,974 Exercise of share options ( 277 ) ( 362 ) ( 1,222 ) Forfeiture of share options ( 50 ) ( 243 ) ( 310 ) Lapse of share options ( 238 ) ( 854 ) ( 197 ) Balance at end of year 37,043 33,701 30,027 Total other reserves 79,173 75,872 72,137 Foreign currency translation reserve The foreign currency translation reserve is used to record exchange differences arising from the translation of the financial statements of foreign operations. Own share reserve The own share reserve represents the cost of 500,000 shares of NuCana plc purchased by NuCana Employee Benefit Trust and that may, at the discretion of the trustee, be used to satisfy future exercise of options under the Company’s share options plan. Capital reserve The capital reserve balance arose from the reduction of the share premium account and corresponding increase to the capital reserve account reflected as of June 30, 2017 in connection with the Company’s re-registration as a public limited company. Share option reserve The share option reserve is used to recognize the value of equity-settled share-based payments provided to employees, directors and consultants as part of their remuneration. Refer to Note 14 for further details.

Share-based Payments

Share-based Payments	12 Months Ended
	Dec. 31, 2023
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Share-based payments	14. Share-based payments The Company has six share-based payment plans for employees, directors and consultants. The share options granted under these plans will be settled in equity. Options granted under each of the six plans have a maximum life of 10 years. 2021, 2022 and 2023 options In 2021, 2022 and 2023, share options were granted under the following share-based payment plan: 2020 Long-Term Incentive Plan Options granted under this plan will vest if the option holder remains under their respective contract of employment or contract of service for the agreed vesting period. The share options granted under this plan will vest over a period of up to four years . Upon vesting, each option allows the holder to purchase one ordinary share at a specified option price determined at grant date. Options granted as RSU-style options are automatically exercised on vesting. If the Company determines, and at its discretion, an arrangement may be made under the 2020 Long-Term Incentive Plan to substitute the right to acquire shares with a cash alternative of equivalent value. Share options and weighted average exercise prices are as follows for the reporting periods presented: Number of Weighted £ Outstanding at January 1, 2021 7,724,791 3.78 Granted 4,329,913 1.91 Forfeited ( 193,949 ) 5.26 Lapsed ( 42,750 ) 11.21 Exercised 1 ( 1,014,939 ) 0.20 Outstanding at December 31, 2021 10,803,066 3.32 Granted 1,497,013 0.39 Forfeited ( 207,833 ) 2.83 Lapsed ( 151,350 ) 8.40 Exercised 2 ( 219,220 ) 0.30 Outstanding at December 31, 2022 11,721,676 2.94 Granted 2,733,139 0.82 Forfeited ( 97,180 ) 1.37 Lapsed ( 253,454 ) 1.42 Exercised 3 ( 102,957 ) 0.04 Outstanding at December 31, 2023 4 14,001,224 2.59 Vested and exercisable at December 31, 2023 7,564,156 3.61 Vested and exercisable at December 31, 2022 5,686,556 3.63 Vested and exercisable at December 31, 2021 4,138,803 3.51 1. The weighted average share price at the date of exercise of these options was £ 3.77 2. The weighted average share price at the date of exercise of these options was £ 0.85 3. The weighted average share price at the date of exercise of these options was £ 0.68 4. The exercise price of outstanding share options ranges from £ 0.04 to £ 18.05 The weighted average remaining contractual life of the share options outstanding as at December 31, 2023 is 6.66 years (2022: 6.99 years; 2021: 7.59 years). 14. Share-based payments (continued) The following principal assumptions were used in the valuation for 2021 share options: Options granted on Jan 13, 2021 Feb 10, 2021 Feb 10, 2021 Vesting dates Jan 13, 2022 Feb 10, 2022 Feb 10, 2022 Jan 13, 2023 Feb 10, 2023 Feb 10, 2023 Jan 13, 2024 Feb 10, 2024 Feb 10, 2024 Jan 13, 2025 Feb 10, 2025 Feb 10, 2025 Volatility 1 81.42 % 87.66 % 81.45 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 0.01 % 0.01 % 0.11 % Fair value of option at grant date 1 £ 2.37 £ 4.49 £ 2.74 Fair value of share at grant date £ 3.92 £ 4.53 £ 4.53 Exercise price at date of grant £ 3.92 £ 0.04 £ 4.53 Lapse date Jan 13, 2031 — Feb 10, 2031 Expected option life (years) 1 4.50 2.50 4.50 Number of options granted 200,000 91,888 872,775 Feb 10, 2021 Aug 11, 2021 Sept 15, 2021 Vesting dates Feb 10, 2022 Aug 11, 2022 Sept 15, 2022 Feb 10, 2023 Aug 11, 2023 Sept 15, 2023 Feb 10, 2024 Aug 11, 2024 Sept 15, 2024 Feb 10, 2025 Aug 11, 2025 Sept 15, 2025 Volatility 1 83.86 % 81.07 % 79.60 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 0.05 % 0.28 % 0.21 % Fair value of option at grant date 1 £ 4.49 £ 0.95 £ 1.67 Fair value of share at grant date £ 4.53 £ 1.57 £ 1.71 Exercise price at date of grant £ 0.04 £ 1.57 £ 0.04 Lapse date Feb 10, 2031 Aug 11, 2031 — Expected option life (years) 1 3.50 4.50 2.50 Number of options granted 337,000 430,000 140,650 Sept 15, 2021 Sept 15, 2021 Dec 15, 2021 Vesting dates Sept 15, 2022 Sept 15, 2022 Dec 15, 2022 Sept 15, 2023 Sept 15, 2023 Dec 15, 2023 Sept 15, 2024 Sept 15, 2024 Dec 15, 2024 Sept 15, 2025 Sept 15, 2025 Dec 15, 2025 Volatility 1 82.06 % 80.90 % 81.80 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 0.29 % 0.36 % 0.48 % Fair value of option at grant date 1 £ 1.67 £ 1.04 £ 1.05 Fair value of share at grant date £ 1.71 £ 1.71 £ 1.72 Exercise price at date of grant £ 0.04 £ 1.71 £ 1.72 Lapse date Sept 15, 2031 Sept 15, 2031 Dec 15, 2031 Expected option life (years) 1 3.50 4.50 4.50 Number of options granted 603,900 1,488,700 165,000 1. Represents the average for the options granted 14. Share-based payments (continued) The fair values of options granted were determined using the Black-Scholes model that takes into account factors specific to the share incentive plan such as the assumption that the options are exercised at a point in time of up to 2 years after vesting. This has been incorporated into the measurement by means of actuarial modelling. As NuCana plc was unlisted until October 2, 2017, it is not possible to derive historical volatility from the Company’s ADSs prior to October 2017. For options with an estimated life of greater than four years, the underlying expected volatility was determined by using the historical volatility of similar listed entities as a proxy. The volatility percentage applied to each tranche is the average of the historical volatility of comparable companies to the Company. Options granted with an estimated life of four years or less, have been valued using the Company’s own historical volatility rates. In the year ended December 31, 2021, an employee remuneration expense, all of which related to equity-settled share-based payments, of £ 6.7 million has been included in the statement of operations and credited to equity. The following principal assumptions were used in the valuation for 2022 share options: Options granted on Mar 9, 2022 Mar 9, 2022 Vesting dates Mar 9, 2023 Mar 9, 2023 Mar 9, 2024 Mar 9, 2024 Mar 9, 2025 Mar 9, 2025 Mar 9, 2026 Mar 9, 2026 Volatility 1 89.32 % 95.70 % Dividend yield 0 % 0 % Risk-free investment rate 1 1.36 % 1.37 % Fair value of option at grant date 1 £ 0.37 £ 0.53 Fair value of share at grant date £ 0.56 £ 0.56 Exercise price at date of grant £ 0.56 £ 0.04 Lapse date Mar 9, 2032 Mar 9, 2032 Expected option life (years) 1 4.50 3.50 Number of options granted 1,020,925 95,000 Jul 12, 2022 Jul 12, 2022 Vesting dates Jul 12, 2023 Jul 12, 2023 Jul 12, 2024 Jul 12, 2024 Jul 12, 2025 Jul 12, 2025 Jul 12, 2026 Jul 12, 2026 Volatility 1 94.05 % 103.18 % Dividend yield 0 % 0 % Risk-free investment rate 1 1.76 % 1.79 % Fair value of option at grant date 1 £ 0.64 £ 0.64 Fair value of share at grant date £ 0.67 £ 0.67 Exercise price at date of grant £ 0.04 £ 0.04 Lapse date Jul 12, 2032 — Expected option life (years) 1 3.50 2.50 Number of options granted 275,725 105,363 1. Represents the average for the options granted 14. Share-based payments (continued) The fair values of options granted were determined using the Black-Scholes model that takes into account factors specific to the share incentive plan such as the assumption that the options are exercised at a point in time of up to 2 years after vesting. This has been incorporated into the measurement by means of actuarial modelling. As NuCana plc was unlisted until October 2, 2017, it is not possible to derive historical volatility from the Company’s ADSs prior to October 2017. For options with an estimated life of greater than four years, the underlying expected volatility was determined by using the historical volatility of similar listed entities as a proxy. The volatility percentage applied to each tranche is the average of the historical volatility of comparable companies to the Company. Options granted with an estimated life of four years or less, have been valued using the Company’s own historical volatility rates. In the year ended December 31, 2022, an employee remuneration expense, all of which related to equity-settled share-based payments, of £ 4.9 million (2021: £ 6.7 million) has been included in the statement of operations and credited to equity. The following principal assumptions were used in the valuation for 2023 share options: Options granted on Jan 11, 2023 Jan 11, 2023 Jan 11, 2023 Vesting dates Jan 11, 2024 Jan 11, 2024 Jan 11, 2024 Jan 11, 2025 Jan 11, 2025 Jan 11, 2025 Jan 11, 2026 Jan 11, 2026 Jan 11, 2026 Jan 11, 2027 Jan 11, 2027 Jan 11, 2027 Volatility 1 97.11 % 105.11 % 116.33 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 3.31 % 3.34 % 3.38 % Fair value of option at grant date 1 £ 0.87 £ 1.19 £ 1.19 Fair value of share at grant date £ 1.23 £ 1.23 £ 1.23 Exercise price at date of grant £ 1.23 £ 0.04 £ 0.04 Lapse date Jan 11, 2033 Jan 11, 2033 — Expected option life (years) 1 4.50 3.50 2.50 Number of options granted 1,774,176 655,425 219,163 Jun 16, 2023 Jun 16, 2023 Jul 12, 2023 Vesting dates Jun 16, 2024 Jun 16, 2024 Jul 12, 2024 Volatility 1 121.58 % 124.98 % 106.61 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 4.98 % 4.99 % 5.21 % Fair value of option at grant date 1 £ 0.56 £ 0.55 £ 0.42 Fair value of share at grant date £ 0.59 £ 0.59 £ 0.62 Exercise price at date of grant £ 0.04 £ 0.04 £ 0.62 Lapse date Jun 16, 2033 — Jul 12, 2033 Expected option life (years) 1 2.00 1.00 3.00 Number of options granted 37,500 9,375 37,500 1. Represents the average for the options granted 14. Share-based payments (continued) The fair values of options granted were determined using the Black-Scholes model that takes into account factors specific to the share incentive plan such as the assumption that the options are exercised at a point in time of up to 2 years after vesting. This has been incorporated into the measurement by means of actuarial modelling. As NuCana plc was unlisted until October 2, 2017, it is not possible to derive historical volatility from the Company’s ADSs prior to October 2017. For options with an estimated life of greater than five years, the underlying expected volatility was determined by using the historical volatility of similar listed entities as a proxy. The volatility percentage applied to each tranche is the average of the historical volatility of comparable companies to the Company. Options granted with an estimated life of five years or less, have been valued using the Company’s own historical volatility rates. In the year ended December 31, 2023, an employee remuneration expense, all of which related to equity-settled share-based payments, of £ 3.9 million (2022: £ 4.9 million) has been included in the statement of operations and credited to equity.

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Presentation of leases for lessee [abstract]
Leases	15. Leases The Company has lease contracts solely for office space with lease terms of between two and five years . Generally, the Company is restricted from assigning and subleasing the leased assets. There are a number of lease contracts that include extension and termination options and variable lease payments, which are discussed further below. Refer to Note 9 for the carrying amounts of right of use assets recognized and the movements during the year. The carrying amounts of lease liabilities and the movements during the year are as follows: 2023 2022 (in thousands) £ £ At January 1 639 371 Re-measurement of liability 4 480 Accretion of interest 29 21 Payments ( 270 ) ( 227 ) Effect of foreign currency exchange differences ( 6 ) ( 6 ) At December 31 396 639 Classified as: Current 206 243 Non-current 190 396 396 639 The maturity analysis of lease liabilities is as follows: 2023 2022 (in thousands) £ £ Contractual undiscounted payments Not later than 1 year 224 272 Later than 1 year and not later than 3 years 164 306 Later than 3 years and not later than 5 years 41 123 Total contractual undiscounted payments 429 701 Less: effect of discounting ( 33 ) ( 62 ) Discounted lease liabilities 396 639 15. Leases (continued) The following amounts are recognized in the statements of operations with respect to lease contracts: 2023 2022 2021 (in thousands) £ £ £ Depreciation expense of right of use assets 212 251 266 Interest expense on lease liabilities (included in administrative expenses) 29 21 18 Total amount recognized in statements of operations 241 272 284 The Company had total net cash outflows for leases of £ 0.3 million in 2023 (2022: £ 0.2 million). The Company has one lease contract with variable payments where the lease costs after the first year of the lease are increased based upon a consumer price index and, therefore, the lease liability for this lease was re-measured at December 31, 2023. All other lease contracts have fixed payments. The Company has a number of lease contracts that include extension and termination options. These options are negotiated by management to provide flexibility in managing the leased asset portfolio and align it with the Company’s business needs. None of the termination options have been exercised or are expected to be exercised, however, two leases terminated on expiry in 2022. All of the extension options require a market rental review and the lease cost for the extension period will t ypically be set at the higher of either the current lease cost or the open market lease cost. The Company renewed or extended two lease contracts in 2022, which resulted in a re-measurement of the right of use asset and lease liability of £ 0.5 million. Based upon the current lease cost, the undiscounted future rental payments of potential extension options that are not included in the lease liability are as follows: 2023 2022 (in thousands) £ £ Extension options not expected to be exercised Not later than 5 years 256 256 Total 256 256

Related Party Disclosures

Related Party Disclosures	12 Months Ended
	Dec. 31, 2023
Related party transactions [abstract]
Related party disclosures	16. Related party disclosures Compensation of key management personnel of the Company 2023 2022 2021 (in thousands) £ £ £ Short-term employee benefits 2,684 2,770 2,165 Pension and other benefits 145 135 104 Share-based payments 3,154 4,255 5,637 5,983 7,160 7,906 The amounts disclosed in the table above are the amounts recognized as an expense during the reporting year.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2023
Cash and cash equivalents [abstract]
Cash and cash equivalents	17. Cash and cash equivalents 2023 2022 (in thousands) £ £ Cash and cash equivalents 17,225 41,912 Cash and cash equivalents comprise cash at banks with deposit maturity terms of three months or less. Cash at banks earns interest at fixed or variable rates based on the terms agreed for each account. Liquidity risk is minimal and is managed using deposits with immediate and varied fixed term dates.

Financial Instruments Risk Mana

Financial Instruments Risk Management	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about financial instruments [abstract]
Financial instruments risk management	18. Financial instruments risk management The Company is exposed to market risk arising from exposure to fluctuation in interest rates and currency exchange rates. These risks are managed by maintaining an appropriate mix of cash deposits in the two main currencies the Company operates in, placed with a variety of financial institutions for varying periods according to expected liquidity requirements. Interest Rate Risk As of December 31, 2023, the Company had cash and cash equivalents of £ 17.2 million (2022: £ 41.9 million). Exposure to interest rate sensitivity is impacted primarily by changes in the underlying bank interest rates. The Company’s surplus cash and cash equivalents are invested in interest bearing accounts and certificates of deposit from time to time which earn interest at fixed or variable rates based on the terms agreed for each account. The Company has not entered into investments for trading or speculative purposes. Financial assets subject to fixed or variable interest rates are as follows: 2023 2022 (in thousands) Carrying Carrying £ £ Financial assets at short-term fixed rates Cash and cash equivalents 1,961 9,360 Financial assets at variable rates Cash and cash equivalents 6,960 24,348 Non-interest bearing cash balances Cash and cash equivalents 8,304 8,204 An increase in the bank interest rates by 0.5 percentage points would increase the net annual interest income applicable to the cash and cash equivalents held on variable and short-term fixed rate deposits by £ 45,000 (2022: £ 169,000 ). 18. Financial instruments risk management (continued) Currency Risk The Company’s functional currency is U.K. pounds sterling, and our transactions are commonly denominated in that currency. However, a portion of expenses are incurred in other currencies, primarily U.S. dollars, and are exposed to the effects of this exchange rate. Although the Company is based in the United Kingdom, it sources active pharmaceutical ingredient, raw materials, research and development, manufacturing, consulting and other services worldwide, including from the United States, the European Union and India. Any weakening of the pound sterling against the currencies of such other jurisdictions makes the purchase of such goods and services more expensive for the Company. The Company seeks to minimize this exposure by maintaining currency cash balances at levels appropriate to meet foreseeable short to mid-term expenses in these other currencies. The Company thus holds a significant portion of cash and cash equivalents in U.S. dollars and will therefore report the impact of exchange rates movements on these balances. The Company does not use derivative instruments to manage exchange rate exposure. Financial assets and liabilities in foreign currencies, primarily held in U.S. dollars, are as follows: 2023 2022 (in thousands) Carrying Carrying £ £ Financial assets Prepayments, accrued income and other receivables 2,027 2,891 Current income tax receivable 2 1 Cash and cash equivalents 10,949 27,924 Financial liabilities Trade payables 596 727 Lease liabilities 66 132 Accrued expenditure 4,930 1,694 A 1 % increase in the value of the U.K. pound sterling relative to the U.S. dollar would reduce the carrying value of net financial assets and liabilities in foreign currencies by £ 74,000 (2022: £ 283,000 ). Credit risk The Company actively manages cash and cash equivalents across a number of banks and has deposits with different maturity dates. The Company monitors the credit rating of those banks. The majority of the Company's cash and cash equivalents at December 31, 2023 are above the £ 85,000 per depositor per bank protected by the U.K. Financial Services Compensation Scheme. However, over 99 percent of the Company’s cash and cash equivalents at December 31, 2023 were held at U.K. and U.S. financial institutions with short-term A-rated credit ratings, as assessed by recognized international credit rating agencies. As a result, no provision for expected credit losses has been recognized.

Provisions

Provisions	12 Months Ended
	Dec. 31, 2022
Provisions [abstract]
Provisions	19. Provisions Legal proceedings Dilapidations Total (in thousands) £ £ £ At January 1, 2023 4,100 46 4,146 Additions — 21 21 Reverse unused ( 46 ) — ( 46 ) Utilized ( 3,801 ) ( 9 ) ( 3,810 ) Transfer from prepayments, accrued income and other receivables ( 247 ) — ( 247 ) Effect of foreign currency exchange differences ( 6 ) — ( 6 ) At December 31, 2023 — 58 58 Classified as: Non-current — 58 58 — 58 58 Legal proceedings In February 2021, Gilead Sciences, Inc. and Gilead Sciences Limited filed a lawsuit against the Company in the Patents Court of the High Court of Justice of England and Wales requesting revocation of the U.K. part of EP 2955190, or EP 190. Subsequently, in March 2021, we filed a counterclaim against the two Gilead entities alleging infringement of our patent resulting from acts including the sale of Sovaldi, as well as its combination products Harvoni, Vosevi and Epclusa, in the U.K. In September 2022, we were granted a further European patent from the EPO, EP 3904365, or EP 365, that covers the composition of matter of a smaller genus of phosphoramidate nucleotide compounds that includes sofosbuvir. Gilead Sciences, Inc. and Gilead Sciences Limited subsequently amended their claim to request revocation of the U.K. part of EP 365 and we counterclaimed for infringement. The Patents Court of the High Court of Justice of England and Wales heard this case between January 20, 2023 and February 3, 2023 and a judgment was handed down on March 21, 2023. In its judgment, the High Court deemed that EP 190 and EP 365 were invalid in the U.K. Following the judgment, the two Gilead entities were entitled to recover a portion of their legal costs from the Company. The judgment was a post balance sheet adjusting event, so a provision of £ 3.0 million was recognized as at December 31, 2022 with respect to an estimate of the cost reimbursement due to Gilead. In addition, following the decision of the EPO Technical Board of Appeal on March 24, 2023 revoking EP 190, the Company reassessed its estimate of the outcome and financial effect of the patent infringement proceedings in Germany, disclosed in Note 10, and a provision of £ 1.1 million was recognized as at December 31, 2022 with respect to an estimate of the cost reimbursement due to Gilead. All obligations arising from the patent infringement litigation in the U.K. and Germany have been settled as at December 31, 2023. Dilapidations The Company has lease contracts for office space that have a requirement to remove all fixtures and fittings on termination of the lease. As of December 31, 2023, the Company had a provision of £ 58,000 (2022: £ 46,000 ) to cover the costs of complying with these requirements.

Events After the Reporting Peri

Events After the Reporting Period	12 Months Ended
	Dec. 31, 2023
Events After Reporting Period [Abstract]
Events After the Reporting Period	20. Events after the reporting period There have been no significant changes to the Company’s circumstances since the year end.

Material Accounting Policies (P

Material Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Summary Of Material Accounting Policies [Abstract]
Basis of preparation	Basis of preparation The financial statements have been prepared in conformity with International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standards Board (“IASB”) and in conformity with U.K. adopted international accounting standards. The Company’s financial statements comprise the financial statements of the Company and its subsidiaries at December 31, 2023. The financial statements are presented in pounds sterling, which is also the Company’s functional currency. All values are rounded to the nearest thousand, except where otherwise indicated.
Going concern	Going concern The Company’s consolidated financial statements have been presented on the basis that it is a going concern. The Company has not generated any revenues from operations to date and does not expect to in the foreseeable future. As such, the Company has incurred recurring net losses, has an accumulated deficit totaling £ 207.7 million and cash flows used in operating activities of £ 26.4 million for the year ended December 31, 2023. The Company had £ 17.2 million of cash and cash equivalents at December 31, 2023. In reviewing the going concern assessment the Company’s board of directors have considered a going concern period of 12-months from the issuance of these financial statements. Based on our current operating plan, our cash and cash equivalents on hand will not be sufficient to fund our anticipated operations for the entirety of the going concern assessment period. As the Company intends to continue to progress its research and development activities, there will be a requirement to seek additional capital within the going concern period to fund operations, which the Company may obtain from additional equity financings, debt financings or other sources. If the Company is unable to obtain additional capital, the Company will be required to delay or reduce its research and development programs which could negatively impact its ability to generate future sustainable operating revenues and profits. As a result of these matters, there is uncertainty related to the ability of the Company to raise sufficient additional capital within the going concern period, prior to its cash balances being exhausted. These events or conditions raise substantial doubt about the Company’s ability to continue as a going concern and, therefore, that the Company may be unable to realize its assets and discharge its liabilities in the normal course of business. The consolidated financial statements do not include any adjustments that might result from the outcome of this uncertainty.
Judgements and estimates	Judgements and estimates The preparation of the financial statements requires management to make judgements, estimates and assumptions that affect the amounts reported for assets and liabilities at the balance sheet dates and the amounts reported for revenue and expenses during the year. The nature of estimations means that actual outcomes could differ from those estimates. The following judgements have had the most material effect on the amounts recognized in the financial statements:
Research and development expenses	Research and development expenses The Company recognizes research and development expenses in the statement of operations in the period in which they are incurred. When development activities reach the advanced stage, as set out in the specific criteria of International Accounting Standard (“IAS”) 38, Intangible Assets , there will be a requirement to capitalize such costs as intangible assets. Management will continue to exercise judgement in the appropriate treatment of research and development costs.
Taxation	Taxation Management judgement is required to determine the amount of deferred tax assets that should be recognized, based upon the likely timing and level of future taxable profits. Further details are contained in Note 7. The following estimates have had the most material effect on the amounts recognized in the financial statements:
Recognition of clinical trial expenses	Recognition of clinical trial expenses As part of the process of preparing our consolidated financial statements, we may be required to estimate accrued or prepaid expenses related to our clinical trials. In order to obtain reasonable estimates, we review open contracts and master service agreements. In addition, we communicate with applicable personnel in order to identify services that have been performed, but for which we have not yet been invoiced, and services not yet performed for which we have been invoiced in advance. In most cases, our vendors provide us with monthly invoices in arrears for services performed. The following are examples of our accrued expenses: • fees paid to CROs for services performed on clinical trials; and • pass-through costs for activities at clinical trial investigator sites. Accruals for clinical trial expenses, including estimated amounts recognized consistent with the above policy, were £ 6.2 million at December 31, 2023 as compared to £ 6.6 million at December 31, 2022. This includes accruals for investigator fees of £ 4.8 million at December 31, 2023 as compared to £ 4.2 million at December 31, 2022. Prepayments for clinical trial expenses, including estimated amounts recognized consistent with the above policy, were £ 1.0 million at December 31, 2023 as compared to £ 1.8 million at December 31, 2022. These amounts include sums that are expected to be utilized over the period of the associated trials, which in some cases could be greater than one year.
Recognition of contracted manufacturing expenses	Recognition of contracted manufacturing expenses As part of the process of preparing our consolidated financial statements, we may be required to estimate accrued or prepaid expenses related to our contracted manufacturing expenses. In order to obtain reasonable estimates, we review open contracts and master service agreements. In addition, we consult with applicable personnel in order to identify services that have been performed and which have not yet been invoiced, and services not yet performed for which we have been invoiced in advance. Accruals for contracted manufacturing expenses, including estimated amounts recognized consistent with the above policy, were £ 0.4 million at December 31, 2023 as compared to £ 0.4 million at December 31, 2022. Prepayments for contracted manufacturing expenses, including estimated amounts recognized consistent with the above policy, were £ 41,000 at December 31, 2023 as compared to £ 0.1 million at December 31, 2022.
Share-based payments	Share-based payments Estimating fair value for share-based payment transactions requires determination of the most appropriate valuation model, which depends on the terms and conditions of the grant. This estimate also requires determination of the most appropriate inputs to the valuation model, including the expected life of the share option, historical volatility of the share price, dividend yield and assumptions about them, and the actual market value of an ordinary share in the Company at the date of grant. For the measurement of the fair value of equity-settled transactions at the grant date, the Company uses the Black-Scholes model. The assumptions used for estimating fair value for share-based payment transactions are detailed in Note 14.
Legal proceedings	Legal proceedings The Company may be party to a number of litigation and other legal proceedings. The Company recognizes a provision for any cost reimbursement due to other parties involved in the legal proceedings if a legal or constructive obligation as a result of a past event exists at the balance sheet date, it is probable that an outflow of economic resources will be required to settle the obligation, and a reasonable estimate can be made of the amount of the obligation, even although the timing or amount of the liability is uncertain. The final amount of any cost reimbursement may be materially different to management’s estimate. Similarly, the Company recognizes an asset for any settlement or cost reimbursement in relation to the legal proceedings due to the Company if it is virtually certain that the income will be received. Where an outflow of economic resources is not probable or an inflow of economic resources is not virtually certain, the Company will disclose a contingent liability or contingent asset, respectively. As of December 31, 2023, the Company had a provision of £ nil (2022: £ 4.1 million) with respect to legal proceedings.
Basis of consolidation	Basis of consolidation The consolidated financial statements comprise the financial statements of the Company and its subsidiaries. Subsidiaries are consolidated from the date on which the Company obtains control, and continue to be consolidated until the date when such control ceases. The financial statements of the subsidiaries are prepared for the same reporting period as the parent company, using consistent accounting policies. All intra-group balances, transactions, unrealized gains and losses resulting from intra-group transactions and dividends are eliminated in full. Assets, liabilities, income and expenses of a subsidiary acquired or disposed of during the year are included in the consolidated financial statements from the date the Company gains control until the date the Company ceases to control the subsidiary.
Foreign currencies	Foreign currencies The Company’s consolidated financial statements are presented in pounds sterling, which is also the parent company’s functional currency. For each group entity, the Company determines the functional currency and items included in the financial statements of each entity are measured using that functional currency. Transactions and balances Transactions in foreign currencies are initially recorded by the Company’s entities at their respective functional currency spot rates of exchange at the date the transaction first qualifies for recognition. Monetary assets and liabilities denominated in foreign currencies are translated at the functional currency spot rates of exchange at the reporting date. Differences arising on settlement or translation of monetary items are recognized in the consolidated statements of operations. 2. Material accounting policies (continued) Non-monetary items that are measured in terms of historical cost in a foreign currency are translated using the exchange rates at the dates of the initial transactions. Group companies On consolidation, the assets and liabilities of foreign operations are translated into pounds sterling at the rate of exchange prevailing at the reporting date and their statements of operations are translated at the average exchange rate for the financial period in which those transactions occur. The exchange differences arising on translation for consolidation are recognized in the consolidated statements of comprehensive income or loss.
Segment reporting	Segment reporting The Company operates in one operating segment. Operating segments are reported in a manner consistent with the internal reporting provided to the Company’s chief operating decision maker (“the CODM”). The Company’s CODM, its Chief Executive Officer, views the Company’s operations and manages its business as a single operating segment, which is the business of developing and commercializing ProTides for use in Oncology. The Company’s principal operations and decision-making functions are located in the United Kingdom from where global decisions are made.
Initial public offering (IPO) related expenses	Share issue expenses Incremental costs incurred and directly attributable to the issuance of shares are deducted from the related proceeds of the issuance. The net amount is recorded as contributed shareholders’ equity in the period when such shares are issued. Costs that are not incremental and directly attributable to issuing new shares, are recorded as an expense in the consolidated statements of operations.
Property, plant and equipment	Property, plant and equipment Property, plant and equipment is stated at cost, net of accumulated depreciation and accumulated impairment losses, if any. There are no restrictions on title to assets nor equipment pledged as security for liabilities. Depreciation is provided on property, plant and equipment over their expected useful economic life as follows: Asset class Depreciation method and period Office and computer equipment Straight-line over 3 years Fixtures and fittings Straight-line over 5 years , or, for non-removable items, the remaining term of an associated lease, whichever is shorter Right of use assets Straight-line over the lease terms, which are between two and five years , or the estimated useful lives of the assets, whichever is shorter
Intangible assets	Intangible assets Intangible assets are stated at cost, net of accumulated amortization and accumulated impairment losses, if any. Cost in relation to patents includes registration, documentation and other legal fees associated with obtaining the patent. Computer software cost represents the initial purchase price of the asset. The amortization method and amortization period for the principal categories of intangible assets are follows: Asset class Amortization method and period Patents Straight-line over 20 years Computer software Straight-line between 3 and 5 years The Company’s primary patents each have a life of 20 years. Further patents are granted in various jurisdictions to extend the territorial coverage of the primary patent. These patents are granted up to the period of the related primary patent. Costs are amortized over the remaining life of the relevant primary patent. The amortization expense on intangible assets with finite lives is recognized in the statements of operations as an administrative expense. The amortization method and the amortization period for an intangible asset with a finite useful life are reviewed at least at each financial year end. Changes in the expected useful economic life or the expected pattern of consumption of future economic benefits embodied in the asset are accounted for by changing the amortization period or method, as appropriate. Intangible assets are tested for impairment when there is an indicator of impairment.
Cash, cash equivalents and short-term deposits	Cash and cash equivalents Cash and cash equivalents in the statement of financial position include cash at banks with deposit maturity terms of three months or less .
Research and development	Research and development Research and development expenses are recognized in the statement of operations in the year in which they are incurred. Development expenditures on an individual project will be recognized as an intangible asset when the Company can demonstrate: • the technical feasibility of completing the intangible asset so that the asset will be available for use or sale; • its intention to complete and its ability and intention to use or sell the asset; • how the asset will generate future economic benefits; • the availability of resources to complete the asset; and • the ability to measure reliably the expenditure during development.
Income Taxes	Income Taxes 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. The tax rates and tax laws used to compute the amounts are those that are enacted or substantively enacted at the reporting date in the countries where the Company operates within the tax regime. 2. Material accounting policies (continued) Income tax credit The Company benefits from the U.K. and U.S. research and development tax credit regimes. In the United Kingdom, a portion of the Company’s losses can be surrendered for a cash rebate of up to 26.97 % of eligible expenditures incurred on or after April 1, 2023 ( 33.35 % prior to April 1, 2023). In the U.S. the Company is able to offset the research and development credits against corporation tax payable. Such credits are accounted for within the tax provision in the year in which the expenditures are incurred.
Leases	Leases The Company assesses, at contract inception, whether a contract is, or contains, a lease. That is, if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company applies a single recognition and measurement approach for all leases, except for short-term leases and leases of low-value assets. The Company recognizes lease liabilities to make lease payments and right of use assets representing the right to use the underlying assets. Right of use assets The Company recognizes right of use assets at the commencement date of the lease (i.e. the date the underlying asset is available for use). Right of use assets are measured at cost, less any accumulated depreciation and impairment losses, and adjusted for any remeasurement of lease liabilities. The cost of right of use assets includes the amount of lease liabilities recognized, initial direct costs incurred, and lease payments made at or before the commencement date less any lease incentives received. Right of use assets, which relate solely to office space, are depreciated on a straight-line basis over the shorter of the lease terms, which are between two and five years , or the estimated useful lives of the assets. Lease liability At the commencement date of the lease, the Company recognizes a lease liability measured at the present value of lease payments to be made over the lease term. The lease payments include fixed payments less any lease incentives receivable, and any variable lease payments that depend on an index. In calculating the present value of lease payments, the Company uses its incremental borrowing rate at the lease commencement date because the interest rate implicit in the lease is not readily determinable. After the commencement date, the amount of the lease liability is increased to reflect the accretion of interest and reduced for the lease payments made. In addition, the carrying amount of the lease liability is remeasured if there is a modification, a change in the lease term or a change in the lease payments. The Company determines the lease term as the non-cancellable term of the lease, together with any periods covered by an option to extend the lease if it is reasonably certain to be exercised, or any periods covered by an option to terminate the lease, if it is reasonably certain not to be exercised. The Company has a number of lease contracts that include extension and termination options. The Company applies judgement in evaluating whether it is reasonably certain whether or not to exercise the option to renew or terminate the lease. That is, it considers all relevant factors that create an economic incentive for it to exercise either the renewal or termination. After the commencement date, the Company reassesses the lease term if there is a significant event or change in circumstances that is within its control and affects its ability to exercise or not to exercise the option to renew or to terminate, such as the construction of significant leasehold improvements. Refer to Note 15 for information on potential future rental payments relating to periods following the exercise date of extension options that are not included in the lease liability.
Provisions	Provisions Provisions are recognized when either a legal or constructive obligation as a result of a past event exists at the balance sheet date, it is probable that an outflow of economic resources will be required to settle the obligation and a reasonable estimate can be made of the amount of the obligation, even although the timing or amount of the liability is uncertain.
Impairment of non-financial assets	Impairment of non-financial assets The Company assesses, at each reporting date, whether there is an indication that an asset may be impaired. If any indication exists, the Company estimates the recoverable amount of the asset. An impairment loss is recognized whenever the carrying amount of an asset or its cash-generating unit exceeds its recoverable amount. Impairment losses are recognized in the consolidated statements of operations. A cash-generating unit is the smallest identifiable group of assets that generates cash inflows that are largely independent of the cash inflows from other assets or groups of assets.
Calculation of recoverable amount	Calculation of recoverable amount The recoverable amount of assets and cash-generating units is the higher of their fair value less costs to sell and value in use. In assessing value in use, the estimated future cash flows are discounted to their present value using a pre-tax discount rate that reflects current market assessments of the time value of money and the risks specific to the asset. For an asset that does not generate largely independent cash inflows, the recoverable amount is determined for the cash-generating unit to which the asset belongs.
Reversal of impairment	Reversal of impairment An assessment is made at each reporting date as to whether there is an indication that a previously recognized impairment loss may no longer exist or may have decreased. If such an indication exists, the recoverable amount is estimated. A previously recognized impairment loss is reversed only if there has been a change in the estimates used to determine the recoverable amount since the last impairment loss was recognized. If that is the case, the carrying value is increased to its recoverable amount. An impairment loss is reversed only to the extent that the asset’s carrying amount does not exceed the carrying amount that would have been determined, net of depreciation or amortization, if no impairment loss had been recognized.
Share-based payments	Share-based payments Employees, directors and consultants of the Company receive remuneration in the form of share options, whereby individuals render services as consideration for equity instruments and the cost is recognized as share-based payments under IFRS 2. Under IFRS 2 Share-based Payment , equity share-based payments are measured at the fair value of the equity instruments at the grant date. Details regarding the determination of fair value of equity settled share-based transactions are set out in Note 14. The fair value determined at the grant date of equity settled share-based payments, after adjusting for an assumed forfeiture rate, is expensed on a straight-line basis over the vesting period, with a corresponding increase in equity to the share option reserve. 2. Material accounting policies (continued)
Fair value measurement	Fair value measurement The fair value of the financial assets and liabilities is included at the amount at which an instrument could be exchanged in a current transaction between willing parties, other than in a forced liquidation or sale. Fair value is based on the price that would be received from the sale of an asset or that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. In order to increase consistency and comparability in fair value measurements, IFRS 13 establishes a fair value hierarchy that prioritizes observable and unobservable inputs used to measure fair value into three broad levels, which are described as follows: Level 1: Quoted (unadjusted) prices in active markets for identical assets or liabilities. Level 2: Other techniques for which all inputs that have a significant effect on the recorded fair value are observable, either directly or indirectly. Level 3: Techniques that use inputs that have a significant effect on the recorded fair value that are not based on observable market data. The fair values of cash and cash equivalents, other receivables, and trade payables approximate their carrying amounts largely due to the short-term maturities of these instruments.
Accounting Standards	Accounting Standards In preparing these financial statements, the Company has applied all relevant IAS, IFRS and International Financial Reporting Interpretations Committee (“IFRIC”) Interpretations as of the date of approval of these financial statements and which are mandatory for the financial year ended December 31, 2023. The following amendments have been adopted as of January 1, 2023 in these financial statements: • IFRS 17 Insurance Contracts (effective from January 1, 2023) • Amendments to IAS 1 Presentation of Financial Statements and IFRS Practice Statement 2 – Disclosure of Accounting Policies (effective from January 1, 2023) • Amendments to IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors – Definition of Accounting Estimates (effective from January 1, 2023) • Amendments to IAS 12 Deferred Tax related to Assets and Liabilities arising from a Single Transaction (effective from January 1, 2023) • Amendments to IAS 12 International Tax Reform - Pillar Two Model Rules (effective from January 1, 2023) 2. Material accounting policies (continued) The Company concluded that these have not had a material impact on the Company’s accounts in the period of initial application, but may impact the accounting for future transactions. The IASB and IFRIC have issued the following standards and amendments with an effective date after the date of these financial statements: • Amendments to IAS 1 Presentation of Financial Statements – Classification of Liabilities as Current or Non-Current (effective from January 1, 2024) • Amendments to IAS 1 Presentation of Financial Statements – Non-Current Liabilities with Covenants (effective from January 1, 2024) • Amendments to IFRS 16 Lease Liability in a Sale and Leaseback (effective from January 1, 2024) • Amendments to IAS 7 and IFRS 7 Supplier Finance Arrangements (effective from January 1, 2024) • Amendments to IAS 21 Lack of Exchangeability (effective from January 1, 2025) The Company will adopt the above standards and amendments on their effective date, although the Company has reviewed the above standards and amendments and considers that they either do not apply to the Company or will not have a material impact in future periods.

Material Accounting Policies (T

Material Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Summary Of Material Accounting Policies [Abstract]
Summary of Depreciation on Property, Plant and Equipment Over Their Expected Useful Economic Life	Depreciation is provided on property, plant and equipment over their expected useful economic life as follows: Asset class Depreciation method and period Office and computer equipment Straight-line over 3 years Fixtures and fittings Straight-line over 5 years , or, for non-removable items, the remaining term of an associated lease, whichever is shorter Right of use assets Straight-line over the lease terms, which are between two and five years , or the estimated useful lives of the assets, whichever is shorter
Summary of Amortization Method and Amortization Period for the Principal Categories of Intangible Assets	The amortization method and amortization period for the principal categories of intangible assets are follows: Asset class Amortization method and period Patents Straight-line over 20 years Computer software Straight-line between 3 and 5 years

Staff Costs (Tables)

Staff Costs (Tables)	12 Months Ended
	Dec. 31, 2023
Staff Costs [Line Items]
Schedule of Average Number of Staff Employed Under Contracts of Service Explanatory	The average number of staff employed under contracts of service were: 2023 2022 2021 (number) Research and development activities 23 26 25 Administrative activities 6 7 5 29 33 30
Summary of Directors’ Remuneration and Other Benefits	Directors’ remuneration & other benefits 2023 2022 2021 (in thousands) £ £ £ Directors’ remuneration 1,216 1,290 1,149 Pension and other benefits 61 57 57 1,277 1,347 1,206
Highest Paid Director [member]
Staff Costs [Line Items]
Summary of Directors’ Remuneration and Other Benefits	The above amounts for remuneration include the following in respect of the highest paid director: 2023 2022 2021 (in thousands) £ £ £ Directors’ remuneration 913 966 850 Pension and other benefits 61 57 57 974 1,023 907
Research and Development Expenses
Staff Costs [Line Items]
Disclosure of Employee Benefit Expense	Included in research and development expenses: 2023 2022 2021 (in thousands) £ £ £ Wages and salaries 4,530 4,893 3,931 Social security costs 516 569 465 Pension costs 210 213 189 Share-based payments 2,551 3,125 3,833 7,807 8,800 8,418
Administrative Expenses
Staff Costs [Line Items]
Disclosure of Employee Benefit Expense	Included in administrative expenses: 2023 2022 2021 (in thousands) £ £ £ Wages and salaries 1,500 1,587 1,407 Social security costs 160 155 136 Pension costs 46 46 40 Share-based payments 1,306 1,765 2,831 3,012 3,553 4,414 Total employee benefit expense 10,819 12,353 12,832

Basic and Diluted Loss Per Sh_2

Basic and Diluted Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings per share [abstract]
Schedule of Basic and Diluted Loss Per Share	2023 2022 2021 (in thousands, except per share data) £ £ £ Loss for the year ( 27,632 ) ( 32,021 ) ( 40,533 ) Basic and diluted weighted average number of shares 52,573 52,235 52,041 £ £ £ Basic and diluted loss per share ( 0.53 ) ( 0.61 ) ( 0.78 )

Loss Before Tax (Tables)

Loss Before Tax (Tables)	12 Months Ended
	Dec. 31, 2023
Material income and expense [abstract]
Summary of Loss Before Tax Stated After Charging	Loss before tax is stated after charging: 2023 2022 2021 (in thousands) £ £ £ Administrative expenses: Amortization 208 239 535 Depreciation 367 473 407

Income Tax Credit (Tables)

Income Tax Credit (Tables)	12 Months Ended
	Dec. 31, 2023
Major components of tax expense (income) [abstract]
Schedule of Major Components of Income Tax	The major components of income tax for the years ended December 31, 2023, 2022 and 2021 are as follows: 2023 2022 2021 (in thousands) £ £ £ Current tax: In respect of current year U.K. 4,558 6,366 7,185 In respect of current year U.S. ( 1 ) ( 3 ) — In respect of prior years U.K. ( 206 ) 35 69 Total current tax 4,351 6,398 7,254 Deferred tax: In respect of current year U.S. 48 34 15 In respect of prior years U.S. ( 1 ) — — Total deferred tax 47 34 15 Income tax credit 4,398 6,432 7,269 Current income tax receivable: U.K. tax 5,121 6,366 7,185 U.S. tax 2 1 3 Current income tax receivable 5,123 6,367 7,188 Deferred tax: U.S. tax 143 103 60
Schedule of Reconciliation of Accounting Loss per Statement of Operations	The credit for the year can be reconciled to the loss per the statement of operations as follows: 2023 2022 2021 (in thousands) £ £ £ Loss before tax ( 32,030 ) ( 38,453 ) ( 47,802 ) Tax on loss at standard U.K. tax rate of 23.52 % (2022: 19 %; 2021: 19 %) ( 7,533 ) ( 7,306 ) ( 9,082 ) Effects of: Expenses not deductible 4,818 4,595 4,757 Deduction for R&D ( 7,394 ) ( 8,342 ) ( 9,415 ) Losses surrendered for R&D tax credit 7,394 8,342 9,415 Deferred tax - prior year adjustment 1 — — Overseas tax payable - current year 1 3 — R&D tax credit - U.S. ( 48 ) ( 34 ) ( 15 ) R&D tax credit - current year ( 4,558 ) ( 6,366 ) ( 7,185 ) R&D tax credit - prior years 206 ( 35 ) ( 69 ) Deferred tax asset not recognized 2,715 2,711 4,325 Income tax credit ( 4,398 ) ( 6,432 ) ( 7,269 )

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about intangible assets [abstract]
Summary of Intangible Assets	Patents Computer Total (in thousands) £ £ £ Cost: At December 31, 2021 6,784 385 7,169 Additions 506 — 506 Disposals — ( 234 ) ( 234 ) At December 31, 2022 7,290 151 7,441 Accumulated amortization: At December 31, 2021 4,439 320 4,759 Charge for the year 195 44 239 Disposals — ( 214 ) ( 214 ) Impairment 292 — 292 At December 31, 2022 4,926 150 5,076 Cost: At December 31, 2022 7,290 151 7,441 Additions 474 — 474 At December 31, 2023 7,764 151 7,915 Accumulated amortization: At December 31, 2022 4,926 150 5,076 Charge for the year 208 — 208 Impairment 503 — 503 At December 31, 2023 5,637 150 5,787 Net book value: At December 31, 2023 2,127 1 2,128 At December 31, 2022 2,364 1 2,365 The Company regularly reviews its patent portfolio and during 2023 further development associated with a limited number of patents, relating mainly to preclinical drug candidates, was discontinued. Management concluded that this was an indication of impairment and an impairment charge of £ 0.5 million has been recognized, representing the aggregate carrying value of those patents as at December 31, 2023. This compared to an impairment charge of £ 0.3 million recognized as of December 31, 2022 .

Property Plant and Equipment (T

Property Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about property, plant and equipment [abstract]
Summary of Property, Plant and Equipment	Right of Office and Fixtures Total (in thousands) £ £ £ £ Cost: At December 31, 2021 1,093 379 715 2,187 Additions — 10 — 10 Re-measurement 483 — — 483 Disposals ( 237 ) ( 34 ) ( 130 ) ( 401 ) Effect of foreign currency exchange differences 17 1 — 18 At December 31, 2022 1,356 356 585 2,297 Depreciation: At December 31, 2021 721 249 366 1,336 Charge for the year 251 56 166 473 Disposals ( 237 ) ( 34 ) ( 130 ) ( 401 ) Effect of foreign currency exchange differences 22 1 — 23 At December 31, 2022 757 272 402 1,431 Cost: At December 31, 2022 1,356 356 585 2,297 Additions — 4 21 25 Re-measurement 4 — — 4 Disposals — ( 10 ) — ( 10 ) Effect of foreign currency exchange differences ( 22 ) ( 1 ) — ( 23 ) At December 31, 2023 1,338 349 606 2,293 Depreciation: At December 31, 2022 757 272 402 1,431 Charge for the year 212 52 103 367 Disposals — ( 10 ) — ( 10 ) Effect of foreign currency exchange differences ( 16 ) — — ( 16 ) At December 31, 2023 953 314 505 1,772 Net book value: At December 31, 2023 385 35 101 521 At December 31, 2022 599 84 183 866

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure Of Other Assets [Abstract]
Disclosure of Other Assets	2023 2022 (in thousands) £ £ Other assets — 2,684

Prepayments, Accrued Income a_2

Prepayments, Accrued Income and Other Receivables (Tables)	12 Months Ended
	Dec. 31, 2023
Prepayments Accrued Income And Other Receivables [Abstract]
Summary of Prepayments, Accrued Income and Other Receivables	2023 2022 (in thousands) £ £ Prepayments - manufacturing and clinical 1,081 1,890 Prepayments - other 888 1,416 Accrued income 21 36 VAT 663 601 Other receivables 18 14 2,671 3,957

Share Capital and Share Premi_2

Share Capital and Share Premium (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of classes of share capital [abstract]
Summary of Share Capital and Share Premium	2023 2022 2021 (in thousands) £ £ £ Share capital 2,114 2,095 2,087 Share premium 141,306 141,108 141,050 143,420 143,203 143,137 Number Number Number (in thousands) Issued share capital comprises: Ordinary shares of £ 0.04 each 52,860 52,373 52,180 52,860 52,373 52,180
Summary of Movement in the Share Capital	Number Share Share (in thousands) £ £ Fully paid shares: Balance at December 31, 2021 52,180 2,087 141,050 Exercise of share options 193 8 58 Balance at December 31, 2022 52,373 2,095 141,108 Exercise of share options 79 3 1 Issue of share capital 408 16 197 Balance at December 31, 2023 52,860 2,114 141,306

Other Reserves (Tables)

Other Reserves (Tables)	12 Months Ended
	Dec. 31, 2023
Other Reserves
Disclosure Of Other Reserves [Line Items]
Schedule of Other Reserves	2023 2022 2021 (in thousands) £ £ £ Own share reserve ( 339 ) ( 339 ) ( 339 ) Foreign currency translation reserve 3 44 ( 17 ) Capital reserve 42,466 42,466 42,466 Share option reserve Balance at beginning of year 33,701 30,027 24,782 Share-based payments 3,907 5,133 6,974 Exercise of share options ( 277 ) ( 362 ) ( 1,222 ) Forfeiture of share options ( 50 ) ( 243 ) ( 310 ) Lapse of share options ( 238 ) ( 854 ) ( 197 ) Balance at end of year 37,043 33,701 30,027 Total other reserves 79,173 75,872 72,137

Share-based Payments (Tables)

Share-based Payments (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Summary of Share Options and Weighted Average Exercise Prices	Share options and weighted average exercise prices are as follows for the reporting periods presented: Number of Weighted £ Outstanding at January 1, 2021 7,724,791 3.78 Granted 4,329,913 1.91 Forfeited ( 193,949 ) 5.26 Lapsed ( 42,750 ) 11.21 Exercised 1 ( 1,014,939 ) 0.20 Outstanding at December 31, 2021 10,803,066 3.32 Granted 1,497,013 0.39 Forfeited ( 207,833 ) 2.83 Lapsed ( 151,350 ) 8.40 Exercised 2 ( 219,220 ) 0.30 Outstanding at December 31, 2022 11,721,676 2.94 Granted 2,733,139 0.82 Forfeited ( 97,180 ) 1.37 Lapsed ( 253,454 ) 1.42 Exercised 3 ( 102,957 ) 0.04 Outstanding at December 31, 2023 4 14,001,224 2.59 Vested and exercisable at December 31, 2023 7,564,156 3.61 Vested and exercisable at December 31, 2022 5,686,556 3.63 Vested and exercisable at December 31, 2021 4,138,803 3.51 1. The weighted average share price at the date of exercise of these options was £ 3.77 2. The weighted average share price at the date of exercise of these options was £ 0.85 3. The weighted average share price at the date of exercise of these options was £ 0.68 4. The exercise price of outstanding share options ranges from £ 0.04 to £ 18.05
Summary of Principal Assumptions Used for Valuation of Share Options	The following principal assumptions were used in the valuation for 2021 share options: Options granted on Jan 13, 2021 Feb 10, 2021 Feb 10, 2021 Vesting dates Jan 13, 2022 Feb 10, 2022 Feb 10, 2022 Jan 13, 2023 Feb 10, 2023 Feb 10, 2023 Jan 13, 2024 Feb 10, 2024 Feb 10, 2024 Jan 13, 2025 Feb 10, 2025 Feb 10, 2025 Volatility 1 81.42 % 87.66 % 81.45 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 0.01 % 0.01 % 0.11 % Fair value of option at grant date 1 £ 2.37 £ 4.49 £ 2.74 Fair value of share at grant date £ 3.92 £ 4.53 £ 4.53 Exercise price at date of grant £ 3.92 £ 0.04 £ 4.53 Lapse date Jan 13, 2031 — Feb 10, 2031 Expected option life (years) 1 4.50 2.50 4.50 Number of options granted 200,000 91,888 872,775 Feb 10, 2021 Aug 11, 2021 Sept 15, 2021 Vesting dates Feb 10, 2022 Aug 11, 2022 Sept 15, 2022 Feb 10, 2023 Aug 11, 2023 Sept 15, 2023 Feb 10, 2024 Aug 11, 2024 Sept 15, 2024 Feb 10, 2025 Aug 11, 2025 Sept 15, 2025 Volatility 1 83.86 % 81.07 % 79.60 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 0.05 % 0.28 % 0.21 % Fair value of option at grant date 1 £ 4.49 £ 0.95 £ 1.67 Fair value of share at grant date £ 4.53 £ 1.57 £ 1.71 Exercise price at date of grant £ 0.04 £ 1.57 £ 0.04 Lapse date Feb 10, 2031 Aug 11, 2031 — Expected option life (years) 1 3.50 4.50 2.50 Number of options granted 337,000 430,000 140,650 Sept 15, 2021 Sept 15, 2021 Dec 15, 2021 Vesting dates Sept 15, 2022 Sept 15, 2022 Dec 15, 2022 Sept 15, 2023 Sept 15, 2023 Dec 15, 2023 Sept 15, 2024 Sept 15, 2024 Dec 15, 2024 Sept 15, 2025 Sept 15, 2025 Dec 15, 2025 Volatility 1 82.06 % 80.90 % 81.80 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 0.29 % 0.36 % 0.48 % Fair value of option at grant date 1 £ 1.67 £ 1.04 £ 1.05 Fair value of share at grant date £ 1.71 £ 1.71 £ 1.72 Exercise price at date of grant £ 0.04 £ 1.71 £ 1.72 Lapse date Sept 15, 2031 Sept 15, 2031 Dec 15, 2031 Expected option life (years) 1 3.50 4.50 4.50 Number of options granted 603,900 1,488,700 165,000 1. Represents the average for the options granted The following principal assumptions were used in the valuation for 2022 share options: Options granted on Mar 9, 2022 Mar 9, 2022 Vesting dates Mar 9, 2023 Mar 9, 2023 Mar 9, 2024 Mar 9, 2024 Mar 9, 2025 Mar 9, 2025 Mar 9, 2026 Mar 9, 2026 Volatility 1 89.32 % 95.70 % Dividend yield 0 % 0 % Risk-free investment rate 1 1.36 % 1.37 % Fair value of option at grant date 1 £ 0.37 £ 0.53 Fair value of share at grant date £ 0.56 £ 0.56 Exercise price at date of grant £ 0.56 £ 0.04 Lapse date Mar 9, 2032 Mar 9, 2032 Expected option life (years) 1 4.50 3.50 Number of options granted 1,020,925 95,000 Jul 12, 2022 Jul 12, 2022 Vesting dates Jul 12, 2023 Jul 12, 2023 Jul 12, 2024 Jul 12, 2024 Jul 12, 2025 Jul 12, 2025 Jul 12, 2026 Jul 12, 2026 Volatility 1 94.05 % 103.18 % Dividend yield 0 % 0 % Risk-free investment rate 1 1.76 % 1.79 % Fair value of option at grant date 1 £ 0.64 £ 0.64 Fair value of share at grant date £ 0.67 £ 0.67 Exercise price at date of grant £ 0.04 £ 0.04 Lapse date Jul 12, 2032 — Expected option life (years) 1 3.50 2.50 Number of options granted 275,725 105,363 1. Represents the average for the options granted The following principal assumptions were used in the valuation for 2023 share options: Options granted on Jan 11, 2023 Jan 11, 2023 Jan 11, 2023 Vesting dates Jan 11, 2024 Jan 11, 2024 Jan 11, 2024 Jan 11, 2025 Jan 11, 2025 Jan 11, 2025 Jan 11, 2026 Jan 11, 2026 Jan 11, 2026 Jan 11, 2027 Jan 11, 2027 Jan 11, 2027 Volatility 1 97.11 % 105.11 % 116.33 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 3.31 % 3.34 % 3.38 % Fair value of option at grant date 1 £ 0.87 £ 1.19 £ 1.19 Fair value of share at grant date £ 1.23 £ 1.23 £ 1.23 Exercise price at date of grant £ 1.23 £ 0.04 £ 0.04 Lapse date Jan 11, 2033 Jan 11, 2033 — Expected option life (years) 1 4.50 3.50 2.50 Number of options granted 1,774,176 655,425 219,163 Jun 16, 2023 Jun 16, 2023 Jul 12, 2023 Vesting dates Jun 16, 2024 Jun 16, 2024 Jul 12, 2024 Volatility 1 121.58 % 124.98 % 106.61 % Dividend yield 0 % 0 % 0 % Risk-free investment rate 1 4.98 % 4.99 % 5.21 % Fair value of option at grant date 1 £ 0.56 £ 0.55 £ 0.42 Fair value of share at grant date £ 0.59 £ 0.59 £ 0.62 Exercise price at date of grant £ 0.04 £ 0.04 £ 0.62 Lapse date Jun 16, 2033 — Jul 12, 2033 Expected option life (years) 1 2.00 1.00 3.00 Number of options granted 37,500 9,375 37,500 1. Represents the average for the options granted

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Presentation of leases for lessee [abstract]
Summary of Carrying Amounts of Lease Liabilities	The carrying amounts of lease liabilities and the movements during the year are as follows: 2023 2022 (in thousands) £ £ At January 1 639 371 Re-measurement of liability 4 480 Accretion of interest 29 21 Payments ( 270 ) ( 227 ) Effect of foreign currency exchange differences ( 6 ) ( 6 ) At December 31 396 639 Classified as: Current 206 243 Non-current 190 396 396 639
Summary of Maturity Analysis of Lease Liabilities	The maturity analysis of lease liabilities is as follows: 2023 2022 (in thousands) £ £ Contractual undiscounted payments Not later than 1 year 224 272 Later than 1 year and not later than 3 years 164 306 Later than 3 years and not later than 5 years 41 123 Total contractual undiscounted payments 429 701 Less: effect of discounting ( 33 ) ( 62 ) Discounted lease liabilities 396 639
Summary of Amounts Recognized in Statements of Operations With Respect to Lease Contracts	The following amounts are recognized in the statements of operations with respect to lease contracts: 2023 2022 2021 (in thousands) £ £ £ Depreciation expense of right of use assets 212 251 266 Interest expense on lease liabilities (included in administrative expenses) 29 21 18 Total amount recognized in statements of operations 241 272 284
Summary of Maturity Analysis of Lease Liabilities Extension Options Not Expected to be Exercised	Based upon the current lease cost, the undiscounted future rental payments of potential extension options that are not included in the lease liability are as follows: 2023 2022 (in thousands) £ £ Extension options not expected to be exercised Not later than 5 years 256 256 Total 256 256

Related Party Disclosures (Tabl

Related Party Disclosures (Tables)	12 Months Ended
	Dec. 31, 2023
Related party transactions [abstract]
Summary of Compensation of Key Management Personnel	Compensation of key management personnel of the Company 2023 2022 2021 (in thousands) £ £ £ Short-term employee benefits 2,684 2,770 2,165 Pension and other benefits 145 135 104 Share-based payments 3,154 4,255 5,637 5,983 7,160 7,906

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2023
Cash and cash equivalents [abstract]
Schedule of Detailed Information About Cash and Cash Equivalents	2023 2022 (in thousands) £ £ Cash and cash equivalents 17,225 41,912

Financial Instruments Risk Ma_2

Financial Instruments Risk Management (Tables)	12 Months Ended
	Dec. 31, 2023
Disclosure of detailed information about financial instruments [abstract]
Schedule of Financial Assets Subject to Fixed or Variable Interest Rates	Financial assets subject to fixed or variable interest rates are as follows: 2023 2022 (in thousands) Carrying Carrying £ £ Financial assets at short-term fixed rates Cash and cash equivalents 1,961 9,360 Financial assets at variable rates Cash and cash equivalents 6,960 24,348 Non-interest bearing cash balances Cash and cash equivalents 8,304 8,204
Summary of Financial Assets and Liabilities in Foreign Currencies, Primarily Held in U.S Dollars	Financial assets and liabilities in foreign currencies, primarily held in U.S. dollars, are as follows: 2023 2022 (in thousands) Carrying Carrying £ £ Financial assets Prepayments, accrued income and other receivables 2,027 2,891 Current income tax receivable 2 1 Cash and cash equivalents 10,949 27,924 Financial liabilities Trade payables 596 727 Lease liabilities 66 132 Accrued expenditure 4,930 1,694

Provisions (Tables)

Provisions (Tables)	12 Months Ended
	Dec. 31, 2022
Provisions [abstract]
Summary of Provisions	Legal proceedings Dilapidations Total (in thousands) £ £ £ At January 1, 2023 4,100 46 4,146 Additions — 21 21 Reverse unused ( 46 ) — ( 46 ) Utilized ( 3,801 ) ( 9 ) ( 3,810 ) Transfer from prepayments, accrued income and other receivables ( 247 ) — ( 247 ) Effect of foreign currency exchange differences ( 6 ) — ( 6 ) At December 31, 2023 — 58 58 Classified as: Non-current — 58 58 — 58 58

General Information- Additional

General Information- Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 Subsidiary
Disclosure Of General Information About Financial Statements [Abstract]
Name of reporting entity	NuCana plc
Description of nature of entity's operations	clinical-stage biopharmaceutical company developing a portfolio of new medicines to treat patients with cancer
Domicile of entity	United Kingdom
Country of incorporation	England and Wales
Name of subsidiary	NuCana Limited, NuCana, Inc. and NuCana BioMed Trustee Company Limited
Number of subsidiaries	3

Material Accounting Policies -

Material Accounting Policies - Additional Information (Detail)	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 GBP (£) Segment	Dec. 31, 2022 GBP (£)	Dec. 31, 2021 GBP (£)	Dec. 31, 2020 GBP (£)
Disclosure Of Summary Of Material Accounting Policies [Line Items]
Accumulated deficit		£ (207,706,000)	£ (207,706,000)	£ (180,573,000)
Cash flows used in operating activities			(26,439,000)	(23,158,000)	£ (23,824,000)
Cash and cash equivalents		17,225,000	17,225,000	41,912,000	£ 60,264,000	£ 87,356,000
Accrued clinical trial expenses		6,200,000	6,200,000	6,600,000
Accrued investigator fees		4,800,000	4,800,000	4,200,000
Prepayments for clinical trial expenses		1,000,000	1,000,000	1,800,000
Accrued contracted manufacturing expense		400,000	400,000	400,000
Prepayments for contracted manufacturing expenses		41,000	£ 41,000	100,000
Number of operating segment | Segment			1
Cash at banks maturity period			three months or less
Legal proceedings provision		£ 0	£ 0	£ 4,100,000
Right of Use Assets [member]
Disclosure Of Summary Of Material Accounting Policies [Line Items]
Depreciation method			Straight-line
Maximum [member]
Disclosure Of Summary Of Material Accounting Policies [Line Items]
Income tax credit, cash rebate percentage	33.35%	26.97%
Maximum [member] | Right of Use Assets [member]
Disclosure Of Summary Of Material Accounting Policies [Line Items]
Depreciation rate			5 years
Bottom Of Range [Member] | Right of Use Assets [member]
Disclosure Of Summary Of Material Accounting Policies [Line Items]
Depreciation rate			2 years
Patents [member]
Disclosure Of Summary Of Material Accounting Policies [Line Items]
Amortization rate			20 years

Material Accounting Policies _2

Material Accounting Policies - Summary of Depreciation on Property, Plant and Equipment Over Their Expected Useful Economic Life (Detail)	12 Months Ended
	Dec. 31, 2023
Office and Computer Equipment [member]
Disclosure Of Property Plant And Equipment [Line Items]
Depreciation method	Straight-line
Depreciation rate	3 years
Right of Use Assets [member]
Disclosure Of Property Plant And Equipment [Line Items]
Depreciation method	Straight-line
Right of Use Assets [member] | Minimum [member]
Disclosure Of Property Plant And Equipment [Line Items]
Depreciation rate	2 years
Right of Use Assets [member] | Maximum [member]
Disclosure Of Property Plant And Equipment [Line Items]
Depreciation rate	5 years
Fixtures and Fittings [member]
Disclosure Of Property Plant And Equipment [Line Items]
Depreciation method	Straight-line
Depreciation rate	5 years

Material Accounting Policies _3

Material Accounting Policies - Summery of Amortization Method and Amortization Period for the Principal Categories of Intangible Assets (Detail)	12 Months Ended
	Dec. 31, 2023
Patents [member]
Disclosure Of Intangible Assets [Line Items]
Amortization method	Straight-line
Amortization rate	20 years
Computer Software [member]
Disclosure Of Intangible Assets [Line Items]
Amortization method	Straight-line
Computer Software [member] | Bottom Of Range [Member]
Disclosure Of Intangible Assets [Line Items]
Amortization rate	3 years
Computer Software [member] | Maximum [member]
Disclosure Of Intangible Assets [Line Items]
Amortization rate	5 years

Staff Costs - Disclosure of Emp

Staff Costs - Disclosure of Employee Benefit Expense (Details) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Staff Costs [Line Items]
Share-based payments	£ 3,900	£ 4,900	£ 6,700
Total employee benefit expense	10,819	12,353	12,832
Research and Development Expenses
Staff Costs [Line Items]
Wages and salaries	4,530	4,893	3,931
Social security costs	516	569	465
Pension costs	210	213	189
Share-based payments	2,551	3,125	3,833
Total employee benefit expense	7,807	8,800	8,418
Administrative Expenses
Staff Costs [Line Items]
Wages and salaries	1,500	1,587	1,407
Social security costs	160	155	136
Pension costs	46	46	40
Share-based payments	1,306	1,765	2,831
Total employee benefit expense	£ 3,012	£ 3,553	£ 4,414

Staff Costs - Schedule of Avera

Staff Costs - Schedule of Average Number of Staff Employed Under Contracts of Service Explanatory (Details) - Employee	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Staff Costs [Line Items]
Average number of staff employed under contracts of service	29	33	30
Research and Development Expenses
Staff Costs [Line Items]
Average number of staff employed under contracts of service	23	26	25
Administrative Expenses
Staff Costs [Line Items]
Average number of staff employed under contracts of service	6	7	5

Staff Costs - Summary of Direct

Staff Costs - Summary of Directors' Remuneration and Other Benefits (Details) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Staff Costs [Line Items]
Directors’ remuneration	£ 1,216	£ 1,290	£ 1,149
Pension and other benefits	61	57	57
Directors’ remuneration & other benefits	1,277	1,347	1,206
Highest Paid Director [member]
Staff Costs [Line Items]
Directors’ remuneration	913	966	850
Pension and other benefits	61	57	57
Directors’ remuneration & other benefits	£ 974	£ 1,023	£ 907

Staff Costs - Additional Inform

Staff Costs - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£) Director	Dec. 31, 2022 GBP (£) Director	Dec. 31, 2021 GBP (£) Director
Classes of employee benefits expense [abstract]
Number of directors, exercised share options | Director	2	3	3
Gain on exercise of option | £	£ 8,000	£ 48,000	£ 700,000

Basic and Diluted Loss Per Sh_3

Basic and Diluted Loss Per Share - Schedule of Basic and Diluted Loss Per Share (Detail) - GBP (£) £ / shares in Units, £ in Thousands, shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings per share [abstract]
Loss for the year	£ (27,632)	£ (32,021)	£ (40,533)
Basic and diluted weighted average number of shares	52,573	52,235	52,041
Basic loss per share	£ (0.53)	£ (0.61)	£ (0.78)
Diluted loss per share	£ (0.53)	£ (0.61)	£ (0.78)

Loss Before Tax - Summary of Lo

Loss Before Tax - Summary of Loss Before Tax Stated After Charging (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Material income and expense [abstract]
Amortization	£ 208	£ 239	£ 535
Depreciation	£ 367	£ 473	£ 407

Capital Commitments and Conti_2

Capital Commitments and Contingencies - Additional Information (Details) - GBP (£)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Capital Commitments [Line Items]
Employer national insurance contingent liability	£ 100,000	£ 100,000
Prevailing rate of employer national insurance	13.80%
Cardiff Consultants [member]
Capital Commitments [Line Items]
Milestone payments for sub-licensee	£ 1,875,000
Cardiff ProTides [member]
Capital Commitments [Line Items]
Milestone payments for sub-licensee	£ 4,500,000

Income Tax Credit - Schedule of

Income Tax Credit - Schedule of Major Components of Income Tax (Details) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current tax:
Total current tax	£ 4,351	£ 6,398	£ 7,254
Deferred tax:
In respect of prior years, deferred tax	(2,715)	(2,711)	(4,325)
Total deferred tax	47	34	15
Income tax credit	4,398	6,432	7,269
Current income tax receivable	5,123	6,367	7,188
Deferred tax	143	103
U.K. [member]
Current tax:
In respect of current year	4,558	6,366	7,185
In respect of prior years	(206)	35	69
Deferred tax:
Current income tax receivable	5,121	6,366	7,185
U.S. [member]
Current tax:
In respect of current year	(1)	(3)
Deferred tax:
In respect of current year, deferred tax	48	34	15
In respect of prior years, deferred tax	(1)
Current income tax receivable	2	1	3
Deferred tax	£ 143	£ 103	£ 60

Income Tax Credit - Schedule _2

Income Tax Credit - Schedule of Reconciliation of Accounting Loss per Statement of Operations (Details) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of accounting profit multiplied by applicable tax rates [abstract]
Loss before tax	£ (32,030)	£ (38,453)	£ (47,802)
Tax on loss at standard U.K. tax rate	(7,533)	(7,306)	(9,082)
Expenses not deductible	4,818	4,595	4,757
Deduction for R&D	(7,394)	(8,342)	(9,415)
Losses surrendered for R&D tax credit	7,394	8,342	9,415
Deferred tax - prior year adjustment	1
Overseas tax payable - current year	1	3
R&D tax credit - U.S.	(48)	(34)	(15)
R&D tax credit - current year	(4,558)	(6,366)	(7,185)
R&D tax credit - prior years	206	(35)	(69)
Deferred tax asset not recognized	2,715	2,711	4,325
Income tax credit	£ (4,398)	£ (6,432)	£ (7,269)

Income Tax Credit - Schedule _3

Income Tax Credit - Schedule of Reconciliation of Accounting Loss per Statement of Operations (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
U.K. [member]
Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates [Line Items]
Applicable tax rate	23.52%	19%	19%

Income Tax Credit - Additional

Income Tax Credit - Additional Information (Details) - GBP (£)		12 Months Ended
	Apr. 01, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Line Items]
Temporary differences and cumulative carry forward tax losses for which deferred tax has not been recognized		£ 99,100,000	£ 85,900,000	£ 74,400,000
Temporary differences on share based compensation arrangements		600,000	1,300,000	4,100,000
Cumulative carry forward tax losses		98,500,000	84,600,000	70,300,000
Applicable tax rate, Profit		£ (32,030,000)	£ (38,453,000)	£ (47,802,000)
U.K. [member]
Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Line Items]
Applicable tax rate		23.52%	19%	19%
Applicable tax rate, Profit	£ 250,000
U.K. [member] | Minimum [member]
Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Line Items]
Applicable tax rate	19%
U.K. [member] | Maximum [member]
Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Line Items]
Applicable tax rate	25%

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	£ 2,365
Ending Balance	2,128	£ 2,365
Cost [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	7,441	7,169
Additions	474	506
Disposals		234
Ending Balance	7,915	7,441
Accumulated Amortization [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	(5,076)	(4,759)
Charge for the year	208	239
Disposals		(214)
Impairment	503	292
Ending Balance	(5,787)	(5,076)
Patents [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	2,364
Impairment	500	300
Ending Balance	2,127	2,364
Patents [member] | Cost [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	7,290	6,784
Additions	474	506
Ending Balance	7,764	7,290
Patents [member] | Accumulated Amortization [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	(4,926)	(4,439)
Charge for the year	208	195
Impairment	503	292
Ending Balance	(5,637)	(4,926)
Computer software [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	1
Ending Balance	1	1
Computer software [member] | Cost [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	151	385
Disposals		234
Ending Balance	151	151
Computer software [member] | Accumulated Amortization [member]
Disclosure Of Intangible Assets [Line Items]
Beginning Balance	(150)	(320)
Charge for the year		44
Disposals		(214)
Ending Balance	£ (150)	£ (150)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - GBP (£) £ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Patents [member]
Disclosure Of Intangible Assets [Line Items]
Impairment charge	£ 0.5	£ 0.3

Property Plant and Equipment -

Property Plant and Equipment - Summary of Property, Plant and Equipment (Details) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	£ 866
Ending Balance	521	£ 866
Cost [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	2,297	2,187
Additions	25	10
Re-measurement	4	483
Disposals	(10)	(401)
Effect of foreign currency exchange differences	(23)	18
Ending Balance	2,293	2,297
Depreciation [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	(1,431)	(1,336)
Charge for the year	367	473
Disposals	10	401
Effect of foreign currency exchange differences	(16)	23
Ending Balance	(1,772)	(1,431)
Right of Use Assets [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	599
Ending Balance	385	599
Right of Use Assets [member] | Cost [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	1,356	1,093
Re-measurement	4	483
Disposals		(237)
Effect of foreign currency exchange differences	(22)	17
Ending Balance	1,338	1,356
Right of Use Assets [member] | Depreciation [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	(757)	(721)
Charge for the year	212	251
Disposals		237
Effect of foreign currency exchange differences	(16)	22
Ending Balance	(953)	(757)
Office and Computer Equipment [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	84
Ending Balance	35	84
Office and Computer Equipment [member] | Cost [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	356	379
Additions	4	10
Disposals	(10)	(34)
Effect of foreign currency exchange differences	(1)	1
Ending Balance	349	356
Office and Computer Equipment [member] | Depreciation [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	(272)	(249)
Charge for the year	52	56
Disposals	10	34
Effect of foreign currency exchange differences		1
Ending Balance	(314)	(272)
Fixtures and Fittings [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	183
Ending Balance	101	183
Fixtures and Fittings [member] | Cost [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	585	715
Additions	21
Disposals		(130)
Ending Balance	606	585
Fixtures and Fittings [member] | Depreciation [member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	(402)	(366)
Charge for the year	103	166
Disposals		130
Ending Balance	£ (505)	£ (402)

Other Assets - Disclosure of Ot

Other Assets - Disclosure of Other Assets (Details) £ in Thousands	Dec. 31, 2022 GBP (£)
Disclosure Of Other Assets [Abstract]
Other assets	£ 2,684
Current	£ 2,684

Other Assets - Additional Infor

Other Assets - Additional Information (Detail) € in Millions, £ in Millions	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 GBP (£)
Disclosure Of Other Assets [Line Items]
Security deposit to cover legal costs | €	€ 3
Other assets | £		£ 2.7

Prepayments, Accrued Income a_3

Prepayments, Accrued Income and Other Receivables - Summary of Prepayments, Accrued Income and Other Receivables Explanatory (Detail) - GBP (£) £ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Prepayments Accrued Income And Other Receivables [Abstract]
Prepayments - manufacturing and clinical	£ 1,081	£ 1,890
Prepayments - other	888	1,416
Accrued income	21	36
VAT	663	601
Other receivables	18	14
Prepayments, accrued income and other receivables	£ 2,671	£ 3,957

Share Capital and Share Premi_3

Share Capital and Share Premium - Summary of Share Capital and Share Premium (Detail) - GBP (£) £ in Thousands, shares in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Classes Of Share Capital [Line Items]
Share capital	£ 2,114	£ 2,095	£ 2,087
Share premium	141,306	141,108	141,050
Share capital and share premium	£ 143,420	£ 143,203	£ 143,137
Ordinary shares of £0.04 each	52,860	52,373	52,180
Ordinary shares [member]
Disclosure Of Classes Of Share Capital [Line Items]
Ordinary shares of £0.04 each	52,860	52,373	52,180

Share Capital and Share Premi_4

Share Capital and Share Premium - Summary of Share Capital and Share Premium (Parenthetical) (Detail) - £ / shares	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Ordinary shares [member]
Disclosure Of Classes Of Share Capital [Line Items]
Par value per share	£ 0.04	£ 0.04	£ 0.04

Share Capital and Share Premi_5

Share Capital and Share Premium - Summary of Movement in the Share Capital (Detail) £ in Thousands, shares in Thousands	12 Months Ended
	Dec. 31, 2023 GBP (£) shares	Dec. 31, 2022 GBP (£) shares	Dec. 31, 2021 GBP (£) shares
Disclosure Of Classes Of Share Capital [Line Items]
Beginning balance	£ 38,502	£ 65,548	£ 99,230
Beginning balance, Shares | shares	52,373	52,180
Exercise of share options	£ (12)	£ 24	182
Exercise of share options | shares	79	193
Issue of share capital, Shares | shares	408
Ending balance	£ 14,887	£ 38,502	£ 65,548
Ending balance, Shares | shares	52,860	52,373	52,180
Share Capital [member]
Disclosure Of Classes Of Share Capital [Line Items]
Beginning balance	£ 2,095	£ 2,087	£ 2,047
Exercise of share options	3	8	40
Issue of share capital	16
Ending balance	2,114	2,095	2,087
Share Premium [member]
Disclosure Of Classes Of Share Capital [Line Items]
Beginning balance	141,108	141,050	140,890
Exercise of share options	1	58	160
Issue of share capital	197
Ending balance	£ 141,306	£ 141,108	£ 141,050

Other Reserves - Schedule of Ot

Other Reserves - Schedule of Other Reserves (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share option reserve
Total other reserves	£ 79,173	£ 75,872
Other Reserves
Disclosure Of Other Reserves [Line Items]
Own share reserve	(339)	(339)	£ (339)
Foreign currency translation reserve	3	44	(17)
Capital reserve	42,466	42,466	42,466
Share option reserve
Balance at beginning of year	33,701	30,027	24,782
Share-based payments	3,907	5,133	6,974
Exercise of share options	(277)	(362)	(1,222)
Forfeiture of share options	(50)	(243)	(310)
Lapse of share options	(238)	(854)	(197)
Balance at end of year	37,043	33,701	30,027
Total other reserves	£ 79,173	£ 75,872	£ 72,137

Other Reserves - Additional Inf

Other Reserves - Additional Information (Detail)	Dec. 31, 2023 shares
Disclosure Of Other Reserves [Abstract]
Number of shares purchased by employee benefit trust under share options plan	500,000

Share-based Payments - Addition

Share-based Payments - Additional Information (Details) £ in Millions	12 Months Ended
	Dec. 31, 2023 GBP (£) yr Plan	Dec. 31, 2022 GBP (£)	Dec. 31, 2021 GBP (£)	Dec. 31, 2020
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of equity settled share-based payment plans | Plan	6
Weighted average remaining contractual life of outstanding share options	6 years 7 months 28 days	6 years 11 months 26 days	7 years 7 months 2 days
Employee remuneration expense, related to equity-settled share-based payments | £	£ 3.9	£ 4.9	£ 6.7
2021 Share Options [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Term of share options exercised			2 years
2022 Share Options [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Term of share options exercised		2 years
2023 Share Options [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Term of share options exercised	2 years
Maximum [member] | Long-Term Incentive Plan [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Share options granted, vesting period				4 years
Maximum [member] | Employees [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Expected option life (years)	10
Maximum [member] | Directors [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Expected option life (years)	10
Maximum [member] | Consultants [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Expected option life (years)	10

Share-based Payments - Summary

Share-based Payments - Summary of Share Options and Weighted Average Exercise Prices (Details)	12 Months Ended
	Dec. 31, 2023 shares £ / shares	Dec. 31, 2022 shares £ / shares	Dec. 31, 2021 shares £ / shares
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Number of shares, Outstanding, Beginning balance | shares	11,721,676	10,803,066	7,724,791
Number of shares, Granted | shares	2,733,139	1,497,013	4,329,913
Number of shares, Forfeited | shares	(97,180)	(207,833)	(193,949)
Number of shares, Lapsed | shares	(253,454)	(151,350)	(42,750)
Number of shares, Exercised | shares	(102,957)	(219,220)	(1,014,939)
Number of shares, Outstanding, Ending balance | shares	14,001,224	11,721,676	10,803,066
Number of shares, Vested and exercisable, Ending balance | shares	7,564,156	5,686,556	4,138,803
Weighted average exercise price per share, Outstanding, Beginning balance | £ / shares	£ 2.94	£ 3.32	£ 3.78
Weighted average exercise price per share, Granted | £ / shares	0.82	0.39	1.91
Weighted average exercise price per share, Forfeited | £ / shares	1.37	2.83	5.26
Weighted average exercise price per share, Lapsed | £ / shares	1.42	8.4	11.21
Weighted average exercise price per share, Exercised | £ / shares	0.04	0.3	0.2
Weighted average exercise price per share, Outstanding, Ending balance | £ / shares	2.59	2.94	3.32
Weighted average exercise price per share, Vested and exercisable, Ending balance | £ / shares	£ 3.61	£ 3.63	£ 3.51

Share-based Payments - Summar_2

Share-based Payments - Summary of Share Options and Weighted Average Exercise Prices (Parenthetical) (Details) - £ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Weighted average share price for share options at date of exercise	£ 0.68	£ 0.85	£ 3.77
Bottom Of Range [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Exercise price of outstanding share options	0.04
Maximum [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Exercise price of outstanding share options	£ 18.05

Share-based Payments - Summar_3

Share-based Payments - Summary of Principal Assumptions used for Valuation of Share Options (Details)	12 Months Ended
	Dec. 31, 2023 GBP (£) shares yr £ / shares	Dec. 31, 2022 GBP (£) yr shares £ / shares	Dec. 31, 2021 GBP (£) shares yr £ / shares
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of options granted | shares	2,733,139	1,497,013	4,329,913
2021 Share Options [Member] | Grant Date Jan 13, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			81.42%
Dividend yield			0%
Risk-free investment rate			0.01%
Fair value of option at grant date | £			£ 2,370
Fair value of share at grant date			£ 3.92
Exercise price at date of grant			£ 3.92
Lapse date			Jan. 13, 2031
Expected option life (years) | yr			4.5
Number of options granted | shares			200,000
2021 Share Options [Member] | Grant Date Feb 10, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			87.66%
Dividend yield			0%
Risk-free investment rate			0.01%
Fair value of option at grant date | £			£ 4,490
Fair value of share at grant date			£ 4.53
Exercise price at date of grant			£ 0.04
Expected option life (years) | yr			2.5
Number of options granted | shares			91,888
2021 Share Options [Member] | Grant Date Feb 10, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			81.45%
Dividend yield			0%
Risk-free investment rate			0.11%
Fair value of option at grant date | £			£ 2,740
Fair value of share at grant date			£ 4.53
Exercise price at date of grant			£ 4.53
Lapse date			Feb. 10, 2031
Expected option life (years) | yr			4.5
Number of options granted | shares			872,775
2021 Share Options [Member] | Grant Date Feb 10, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			83.86%
Dividend yield			0%
Risk-free investment rate			0.05%
Fair value of option at grant date | £			£ 4,490
Fair value of share at grant date			£ 4.53
Exercise price at date of grant			£ 0.04
Lapse date			Feb. 10, 2031
Expected option life (years) | yr			3.5
Number of options granted | shares			337,000
2021 Share Options [Member] | Grant Date Aug 11, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			81.07%
Dividend yield			0%
Risk-free investment rate			0.28%
Fair value of option at grant date | £			£ 950
Fair value of share at grant date			£ 1.57
Exercise price at date of grant			£ 1.57
Lapse date			Aug. 11, 2031
Expected option life (years) | yr			4.5
Number of options granted | shares			430,000
2021 Share Options [Member] | Grant Date September 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			79.60%
Dividend yield			0%
Risk-free investment rate			0.21%
Fair value of option at grant date | £			£ 1,670
Fair value of share at grant date			£ 1.71
Exercise price at date of grant			£ 0.04
Expected option life (years) | yr			2.5
Number of options granted | shares			140,650
2021 Share Options [Member] | Grant Date Sep 15, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			82.06%
Dividend yield			0%
Risk-free investment rate			0.29%
Fair value of option at grant date | £			£ 1,670
Fair value of share at grant date			£ 1.71
Exercise price at date of grant			£ 0.04
Lapse date			Sep. 15, 2031
Expected option life (years) | yr			3.5
Number of options granted | shares			603,900
2021 Share Options [Member] | Grant Date Sep 15, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			80.90%
Dividend yield			0%
Risk-free investment rate			0.36%
Fair value of option at grant date | £			£ 1,040
Fair value of share at grant date			£ 1.71
Exercise price at date of grant			£ 1.71
Lapse date			Sep. 15, 2031
Expected option life (years) | yr			4.5
Number of options granted | shares			1,488,700
2021 Share Options [Member] | Grant Date Dec 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility			81.80%
Dividend yield			0%
Risk-free investment rate			0.48%
Fair value of option at grant date | £			£ 1,050
Fair value of share at grant date			£ 1.72
Exercise price at date of grant			£ 1.72
Lapse date			Dec. 15, 2031
Expected option life (years) | yr			4.5
Number of options granted | shares			165,000
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Jan 13, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Jan. 13, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Feb 10, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Feb 10, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Feb 10, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Aug 11, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Aug. 11, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date September 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Sep 15, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Sep 15, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2022
2021 Share Options [Member] | Vesting Dates One [Member] | Grant Date Dec 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Dec. 15, 2022
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Jan 13, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Jan. 13, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Feb 10, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Feb 10, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Feb 10, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Aug 11, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Aug. 11, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date September 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Sep 15, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Sep 15, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2023
2021 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Dec 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Dec. 15, 2023
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Jan 13, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Jan. 13, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Feb 10, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Feb 10, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Feb 10, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Aug 11, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Aug. 11, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date September 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Sep 15, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Sep 15, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2024
2021 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Dec 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Dec. 15, 2024
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Jan 13, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Jan. 13, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Feb 10, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Feb 10, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Feb 10, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Feb. 10, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Aug 11, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Aug. 11, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date September 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Sep 15, 2021 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Sep 15, 2021 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Sep. 15, 2025
2021 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Dec 15, 2021 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates			Dec. 15, 2025
2022 Share Options [Member] | Grant Date Mar 9, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility		89.32%
Dividend yield		0%
Risk-free investment rate		1.36%
Fair value of option at grant date | £		£ 370
Fair value of share at grant date		£ 0.56
Exercise price at date of grant		£ 0.56
Lapse date		Mar. 09, 2032
Expected option life (years) | yr		4.5
Number of options granted | shares		1,020,925
2022 Share Options [Member] | Grant Date Mar 9, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility		95.70%
Dividend yield		0%
Risk-free investment rate		1.37%
Fair value of option at grant date | £		£ 530
Fair value of share at grant date		£ 0.56
Exercise price at date of grant		£ 0.04
Lapse date		Mar. 09, 2032
Expected option life (years) | yr		3.5
Number of options granted | shares		95,000
2022 Share Options [Member] | Grant Date Jul 12, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility		94.05%
Dividend yield		0%
Risk-free investment rate		1.76%
Fair value of option at grant date | £		£ 640
Fair value of share at grant date		£ 0.67
Exercise price at date of grant		£ 0.04
Lapse date		Jul. 12, 2032
Expected option life (years) | yr		3.5
Number of options granted | shares		275,725
2022 Share Options [Member] | Grant Date Jul 12, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility		103.18%
Dividend yield		0%
Risk-free investment rate		1.79%
Fair value of option at grant date | £		£ 640
Fair value of share at grant date		£ 0.67
Exercise price at date of grant		£ 0.04
Expected option life (years) | yr		2.5
Number of options granted | shares		105,363
2022 Share Options [Member] | Vesting Dates One [Member] | Grant Date Mar 9, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2023
2022 Share Options [Member] | Vesting Dates One [Member] | Grant Date Mar 9, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2023
2022 Share Options [Member] | Vesting Dates One [Member] | Grant Date Jul 12, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2023
2022 Share Options [Member] | Vesting Dates One [Member] | Grant Date Jul 12, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2023
2022 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Mar 9, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2024
2022 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Mar 9, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2024
2022 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Jul 12, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2024
2022 Share Options [Member] | Vesting Dates Two [Member] | Grant Date Jul 12, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2024
2022 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Mar 9, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2025
2022 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Mar 9, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2025
2022 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Jul 12, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2025
2022 Share Options [Member] | Vesting Dates Three [Member] | Grant Date Jul 12, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2025
2022 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Mar 9, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2026
2022 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Mar 9, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Mar. 09, 2026
2022 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Jul 12, 2022 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2026
2022 Share Options [Member] | Vesting Dates Four [Member] | Grant Date Jul 12, 2022 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates		Jul. 12, 2026
2023 Share Options [Member] | Grant Date January 11, 2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility	97.11%
Dividend yield	0%
Risk-free investment rate	3.31%
Fair value of option at grant date | £	£ 870
Fair value of share at grant date	£ 1.23
Exercise price at date of grant	£ 1.23
Lapse date	Jan. 11, 2033
Expected option life (years) | yr	4.5
Number of options granted | shares	1,774,176
2023 Share Options [Member] | Grant Date January 11, 2023 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility	105.11%
Dividend yield	0%
Risk-free investment rate	3.34%
Fair value of option at grant date | £	£ 1,190
Fair value of share at grant date	£ 1.23
Exercise price at date of grant	£ 0.04
Lapse date	Jan. 11, 2033
Expected option life (years) | yr	3.5
Number of options granted | shares	655,425
2023 Share Options [Member] | Grant Date January 11, 2023 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility	116.33%
Dividend yield	0%
Risk-free investment rate	3.38%
Fair value of option at grant date | £	£ 1,190
Fair value of share at grant date	£ 1.23
Exercise price at date of grant	£ 0.04
Expected option life (years) | yr	2.5
Number of options granted | shares	219,163
2023 Share Options [Member] | Grant Date June 16,2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility	121.58%
Dividend yield	0%
Risk-free investment rate	4.98%
Fair value of option at grant date | £	£ 560
Fair value of share at grant date	£ 0.59
Exercise price at date of grant	£ 0.04
Lapse date	Jun. 16, 2033
Expected option life (years) | yr	2
Number of options granted | shares	37,500
2023 Share Options [Member] | Grant Date June 16,2023 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility	124.98%
Dividend yield	0%
Risk-free investment rate	4.99%
Fair value of option at grant date | £	£ 550
Fair value of share at grant date	£ 0.59
Exercise price at date of grant	£ 0.04
Expected option life (years) | yr	1
Number of options granted | shares	9,375
2023 Share Options [Member] | Grant Date July 12,2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Volatility	106.61%
Dividend yield	0%
Risk-free investment rate	5.21%
Fair value of option at grant date | £	£ 420
Fair value of share at grant date	£ 0.62
Exercise price at date of grant	£ 0.62
Lapse date	Jul. 12, 2033
Expected option life (years) | yr	3
Number of options granted | shares	37,500
2023 Share Options [Member] | Vesting Dates One [Member] | Grant Date January 11, 2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2024
2023 Share Options [Member] | Vesting Dates One [Member] | Grant Date January 11, 2023 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2024
2023 Share Options [Member] | Vesting Dates One [Member] | Grant Date January 11, 2023 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2024
2023 Share Options [Member] | Vesting Dates One [Member] | Grant Date June 16,2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jun. 16, 2024
2023 Share Options [Member] | Vesting Dates One [Member] | Grant Date June 16,2023 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jun. 16, 2024
2023 Share Options [Member] | Vesting Dates One [Member] | Grant Date July 12,2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jul. 12, 2024
2023 Share Options [Member] | Vesting Dates Two [Member] | Grant Date January 11, 2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2025
2023 Share Options [Member] | Vesting Dates Two [Member] | Grant Date January 11, 2023 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2025
2023 Share Options [Member] | Vesting Dates Two [Member] | Grant Date January 11, 2023 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2025
2023 Share Options [Member] | Vesting Dates Three [Member] | Grant Date January 11, 2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2026
2023 Share Options [Member] | Vesting Dates Three [Member] | Grant Date January 11, 2023 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2026
2023 Share Options [Member] | Vesting Dates Three [Member] | Grant Date January 11, 2023 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2026
2023 Share Options [Member] | Vesting Dates Four [Member] | Grant Date January 11, 2023 [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2027
2023 Share Options [Member] | Vesting Dates Four [Member] | Grant Date January 11, 2023 One [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2027
2023 Share Options [Member] | Vesting Dates Four [Member] | Grant Date January 11, 2023 Two [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting dates	Jan. 11, 2027

Leases - Additional information

Leases - Additional information (Detail) £ in Thousands	12 Months Ended
	Dec. 31, 2023 GBP (£) LeaseContract	Dec. 31, 2022 GBP (£) Lease	Dec. 31, 2021 GBP (£)
Presentation of leases for lessee [abstract]
Information about nature of lessee's leasing activities	lease terms of between two and five years
Total net cash outflows for leases	£ 300	£ 200
Information about lessee's exposure arising from variable lease payments	The Company has one lease contract with variable payments where the lease costs after the first year of the lease are increased based upon a consumer price index and, therefore, the lease liability for this lease was re-measured at December 31, 2023.
Number of lease contracts with variable lease payments | LeaseContract	1
Information about lessee's exposure arising from extension options and termination options	The Company has a number of lease contracts that include extension and termination options. These options are negotiated by management to provide flexibility in managing the leased asset portfolio and align it with the Company’s business needs. None of the termination options have been exercised or are expected to be exercised, however, two leases terminated on expiry in 2022.
Number of leases terminated | Lease		2
Number of leases renewed or extended | Lease		2
Right of use asset		£ 500
Lease liabilities	£ 396	639	£ 371
Re-measurement of liability	£ 4	£ 480

Leases - Summary of Carrying Am

Leases - Summary of Carrying Amounts of Lease Liabilities (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease liabilities [abstract]
At January 1	£ 639	£ 371
Re-measurement of liability	4	480
Accretion of interest	29	21	£ 18
Payments	(270)	(227)
Effect of foreign currency exchange differences	(6)	(6)
At December 31	396	639	£ 371
Current	206	243
Non-current	£ 190	£ 396

Leases - Summary of Maturity An

Leases - Summary of Maturity Analysis of Lease Liabilities (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Total contractual undiscounted payments	£ 429	£ 701
Less: effect of discounting	(33)	(62)
Discounted lease liabilities	396	639	£ 371
Not later than 1 year [member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Total contractual undiscounted payments	224	272
Later than 1 year and not later than 3 years [member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Total contractual undiscounted payments	164	306
Later than 3 years and not later than 5 years [member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Total contractual undiscounted payments	£ 41	£ 123

Leases - Summary of Amounts Rec

Leases - Summary of Amounts Recognized in Statements of Operations With Respect to Lease Contracts (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Presentation of leases for lessee [abstract]
Depreciation expense of right of use assets	£ 212	£ 251	£ 266
Interest expense on lease liabilities	29	21	18
Total amount recognized in statements of operations	£ 241	£ 272	£ 284

Leases - Summary of Maturity _2

Leases - Summary of Maturity Analysis of Lease Liabilities Extension Options Not Expected to be Exercised (Detail) - GBP (£) £ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Extension options not expected to be exercised	£ 256	£ 256
Not later than 5 years [member]
Disclosure Of Maturity Analysis Of Operating Lease Payments [Line Items]
Extension options not expected to be exercised	£ 256	£ 256

Related Party Disclosures - Sum

Related Party Disclosures - Summary of Compensation of Key Management Personnel (Detail) - GBP (£) £ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Key Management Personnel Compensation [Abstract]
Short-term employee benefits	£ 2,684	£ 2,770	£ 2,165
Pension and other benefits	145	135	104
Share-based payments	3,154	4,255	5,637
Key management personnel compensation	£ 5,983	£ 7,160	£ 7,906

Cash and Cash Equivalents - Sch

Cash and Cash Equivalents - Schedule of Detailed Information About Cash and Cash Equivalents (Detail) - GBP (£) £ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash and cash equivalents [abstract]
Cash and cash equivalents	£ 17,225	£ 41,912	£ 60,264	£ 87,356

Financial Instruments Risk Ma_3

Financial Instruments Risk Management - Additional Information (Details) - GBP (£)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	£ 17,225,000	£ 41,912,000	£ 60,264,000	£ 87,356,000
Interest Rate Risk [member]
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	£ 17,200,000	41,900,000
Increase in interest rates	0.50%
Increase in interest income on cash and cash equivalents held on variable and short term fixed rate deposits	£ 45,000	169,000
Currency Risk [member]
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	£ 10,949,000	27,924,000
Percentage of increase in foreign exchange rate	1%
Reduction in financial assets and liabilities in foreign currencies	£ 74,000	£ 283,000
Credit Risk [Member] | Bottom Of Range [Member]
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	£ 85,000

Financial Instruments Risk Ma_4

Financial Instruments Risk Management - Schedule of Financial Assets Subject to Fixed or Variable Interest Rates (Details) - GBP (£) £ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure Of Financial Instruments By Type Of Interest Rate [Line Items]
Cash and cash equivalents	£ 17,225	£ 41,912	£ 60,264	£ 87,356
Financial Assets at Short Term Fixed Rates [member]
Disclosure Of Financial Instruments By Type Of Interest Rate [Line Items]
Cash and cash equivalents	6,960	24,348
Financial Assets at Variable Rates [member]
Disclosure Of Financial Instruments By Type Of Interest Rate [Line Items]
Cash and cash equivalents	1,961	9,360
Non-Interest Bearing Cash Balances [member]
Disclosure Of Financial Instruments By Type Of Interest Rate [Line Items]
Cash and cash equivalents	£ 8,304	£ 8,204

Financial Instruments Risk Ma_5

Financial Instruments Risk Management - Summary of Financial Assets and Liabilities in Foreign Currencies, Primarily Held in U.S Dollars (Details) - GBP (£) £ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financial assets
Current income tax receivable	£ 5,123	£ 6,367	£ 7,188
Cash and cash equivalents	17,225	41,912	60,264	£ 87,356
Financial liabilities
Payroll taxes and social security	155	162
Lease liabilities	396	639	£ 371
Accrued expenditure	8,940	10,002
Currency Risk [member]
Financial assets
Prepayments, accrued income and other receivables	2,027	2,891
Current income tax receivable	2	1
Cash and cash equivalents	10,949	27,924
Financial liabilities
Trade payables	596	727
Lease liabilities	66	132
Accrued expenditure	£ 4,930	£ 1,694

Provisions - Summary of Provisi

Provisions - Summary of Provisions (Details) - GBP (£)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Provisions [Line Items]
At January 1, 2023	£ 4,146,000
Additions	21,000
Reverse unused	(46,000)
Utilized	(3,810,000)
Transfer from prepayments, accrued income and other receivables	(247,000)
Effect of foreign currency exchange differences	(6,000)
At December 31, 2023	58,000
Current		£ 4,100,000
Non-current	58,000	46,000
Total provisions	58,000
Legal Proceedings [member]
Disclosure Of Provisions [Line Items]
At January 1, 2023	4,100,000
Reverse unused	(46,000)
Utilized	(3,801,000)
Transfer from prepayments, accrued income and other receivables	(247,000)
Effect of foreign currency exchange differences	(6,000)
Dilapidations [member]
Disclosure Of Provisions [Line Items]
At January 1, 2023	46,000
Additions	21,000
Utilized	(9,000)
At December 31, 2023	58,000
Non-current	58,000
Total provisions	£ 58,000	£ 46,000

Provisions - Additional Informa

Provisions - Additional Information (Details) - GBP (£)	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Provisions [Line Items]
Provision	£ 58,000
Legal Proceedings [member] | U.K. [member]
Disclosure Of Provisions [Line Items]
Provision		£ 3,000,000
Legal Proceedings [member] | Germany [member]
Disclosure Of Provisions [Line Items]
Provision		1,100,000
Dilapidations [member]
Disclosure Of Provisions [Line Items]
Provision	£ 58,000	£ 46,000