NuCana (NCNA) 6-K 18 Nov 21 2021 Q3 Unaudited Condensed Consolidated Statements of Operations Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2021
Cover [Abstract]
Document Type	6-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Registrant Name	NUCANA PLC
Entity Central Index Key	0001709626
Current Fiscal Year End Date	--12-31

Unaudited Condensed Consolidate

Unaudited Condensed Consolidated Statements of Operations - GBP (£) £ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Profit or loss [abstract]
Research and development expenses	£ (8,971)	£ (6,117)	£ (26,200)	£ (17,918)
Administrative expenses	(2,277)	(1,906)	(6,456)	(5,144)
Net foreign exchange gains (losses)	1,274	(1,601)	488	610
Operating loss	(9,974)	(9,624)	(32,168)	(22,452)
Finance income	22	26	81	234
Loss before tax	(9,952)	(9,598)	(32,087)	(22,218)
Income tax credit	1,911	1,204	5,198	3,797
Loss for the period	£ (8,041)	£ (8,394)	£ (26,889)	£ (18,421)
Basic and diluted loss per share	£ (0.15)	£ (0.24)	£ (0.52)	£ (0.55)

Unaudited Condensed Consolida_2

Unaudited Condensed Consolidated Statements of Comprehensive Loss - GBP (£) £ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of comprehensive income [abstract]
Loss for the period	£ (8,041)	£ (8,394)	£ (26,889)	£ (18,421)
Items that may be reclassified subsequently to profit or loss:
Exchange differences on translation of foreign operations	10	(15)	6	7
Other comprehensive income (expense) for the period	10	(15)	6	7
Total comprehensive loss for the period	(8,031)	(8,409)	(26,883)	(18,414)
Attributable to:
Equity holders of the Company	£ (8,031)	£ (8,409)	£ (26,883)	£ (18,414)

Unaudited Condensed Consolida_3

Unaudited Condensed Consolidated Statements of Financial Position - GBP (£) £ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Non-current assets
Intangible assets	£ 4,896	£ 4,753
Property, plant and equipment	952	1,189
Deferred tax asset	34	44
Other non-current assets	2,600	0
Total non-current assets	8,482	5,986
Current assets
Prepayments, accrued income and other receivables	5,133	4,628
Current income tax receivable	5,143	9,822
Cash and cash equivalents	71,027	87,356
Total current assets	81,303	101,806
Total assets	89,785	107,792
Capital and reserves
Share capital and share premium	143,136	142,937
Other reserves	70,395	66,887
Accumulated deficit	(136,084)	(110,594)
Total equity attributable to equity holders of the Company	77,447	99,230
Non-current liabilities
Provisions	46	46
Lease liabilities	195	367
Total non-current liabilities	241	413
Current liabilities
Trade payables	3,891	2,257
Payroll taxes and social security	152	177
Accrued expenditure	7,811	5,437
Lease liabilities	243	278
Total current liabilities	12,097	8,149
Total liabilities	12,338	8,562
Total equity and liabilities	£ 89,785	£ 107,792

Unaudited Condensed Consolida_4

Unaudited Condensed 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, 2019	£ 63,522	£ 1,299	£ 79,541	£ (339)	£ 20,620	£ (10)	£ 42,466	£ (80,055)
Loss for the period	(18,421)							(18,421)
Other comprehensive income (loss) for the year	7					7
Total comprehensive loss for the period	(18,414)					7		(18,421)
Share-based payments	3,069				3,069
Exercise of share options	15	1	14		(68)			68
Lapse of share options					(5)			5
Issue of share capital	66,581	747	65,834
Share issue expenses	(4,499)		(4,499)
Ending balance at Sep. 30, 2020	110,274	2,047	140,890	(339)	23,616	(3)	42,466	(98,403)
Beginning balance at Dec. 31, 2020	99,230	2,047	140,890	(339)	24,782	(22)	42,466	(110,594)
Loss for the period	(26,889)							(26,889)
Other comprehensive income (loss) for the year	6					6
Total comprehensive loss for the period	(26,883)					6		(26,889)
Share-based payments	4,919				4,919
Exercise of share options	181	40	159		(1,221)			1,203
Lapse of share options					(196)			196
Ending balance at Sep. 30, 2021	£ 77,447	£ 2,087	£ 141,049	£ (339)	£ 28,284	£ (16)	£ 42,466	£ (136,084)

Unaudited Condensed Consolida_5

Unaudited Condensed Consolidated Statements of Cash Flows - GBP (£) £ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities
Loss for the period	£ (26,889)	£ (18,421)
Adjustments for:
Income tax credit	(5,198)	(3,797)
Amortization and depreciation	673	667
Finance income	(81)	(234)
Interest expense on lease liabilities	15	20
Share-based payments	4,919	3,069
Net foreign exchange gains	(533)	(619)
Cash flows from (used in) operations before changes in working capital	(27,094)	(19,315)
Movements in working capital:
Increase in prepayments, accrued income and other receivables	(497)	(408)
Increase in trade payables	1,634	1,778
Increase in payroll taxes, social security and accrued expenditure	2,333	1,153
Movements in working capital	3,470	2,523
Cash used in operations	(23,624)	(16,792)
Net income tax received	9,888	4,152
Net cash used in operating activities	(13,736)	(12,640)
Cash flows from investing activities
Interest received	79	300
Payments for property, plant and equipment	(43)	(350)
Payments for intangible assets	(537)	(1,079)
Payments for other non-current assets	(2,597)
Net cash used in investing activities	(3,098)	(1,129)
Cash flows from financing activities
Payments of lease liabilities	(222)	(223)
Proceeds from issue of share capital – exercise of share options	198	15
Proceeds from issue of share capital	0	66,581
Share issue expenses		(4,499)
Net cash (used in) from financing activities	(24)	61,874
Net (decrease) increase in cash and cash equivalents	(16,858)	48,105
Cash and cash equivalents at beginning of period	87,356	51,962
Effect of exchange rate changes on cash and cash equivalents	529	611
Cash and cash equivalents at end of period	£ 71,027	£ 100,678

General Information

General Information	9 Months Ended
	Sep. 30, 2021
Disclosure Of General Information About Financial Statements [Abstract]
General information	1. General information NuCana plc (“NuCana” or the “Company”) is a clinical-stage biopharmaceutical company developing a portfolio of new medicines to treat 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 ordinary shares in the form of American Depositary Shares (“ADSs”) registered with the US Securities and Exchange Commission (the “SEC”) and has been listed on The Nasdaq Global Select Market (“Nasdaq”) since October 2, 2017. 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, Inc., NuCana Limited and NuCana BioMed Trustee Company Limited (together referred to as the “Group”). The financial information presented in these unaudited condensed consolidated financial statements does not constitute the Group’s statutory accounts within the meaning of section 434 of the U.K. Companies Act 2006. The Group’s statutory accounts for the year ended December 31, 2020 have been reported on by the Company’s auditor and delivered to the Registrar of Companies. The report of the auditor was (i) unqualified, (ii) did not include a reference to any matters to which the auditors drew attention by way of emphasis without qualifying their report, and (iii) did not contain a statement under section 498 (2) or (3) of the Companies Act 2006.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Disclosure Of Summary Of Significant Accounting Policies [Abstract]
Significant accounting policies	2. Significant accounting policies Basis of preparation The unaudited condensed consolidated financial statements (the “financial statements”) for the three months and nine months ended September 30, 2021 have been prepared in accordance with International Accounting Standard 34, “ Interim Financial Reporting ” The financial statements do not include all the information and disclosures required in the annual financial statements, and should be read in conjunction with the Company’s annual financial statements for the year ended December 31, 2020. In the opinion of management, these unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair statement of the results of operations, financial position and cash flows. The results of operations for the three months and nine months ended September 30, 2021 are not necessarily indicative of the results that can be expected for the Company’s fiscal year ending December 31, 2021. Going concern In common with many companies in the biopharmaceutical sector, the Company incurs significant expenditure in its early years as it researches and develops its potential products for market. The Company’s board of directors, having reviewed the operating budgets and development plans, considers that the Company has adequate resources to continue in operation for the foreseeable future. The board of directors is therefore satisfied that it is appropriate to adopt the going concern basis of accounting in preparing the financial statements. The Company believes that its cash and cash equivalents of £71.0 million at September 30, 2021 will be sufficient to fund its current operating plan for at least the next 12 months. Further, the directors have conducted an assessment of the impact of COVID-19 As the Company continues to incur losses, the transition to profitability is dependent upon the successful development, approval and commercialization of its product candidates and achieving a level of revenues adequate to support its cost structure. The Company may never achieve profitability, and unless and until it does, it will continue to need to raise additional capital. There can be no assurances, however, that additional funding will be available on acceptable terms. COVID-19 In response to the spread of COVID-19, on-site During the early months of the pandemic the Company announced that there was some temporary interruption to the enrollment of new patients in the Company’s ongoing clinical trials. In May 2020, the Company further announced that enrollment of new patients in the Company’s clinical trials had re-commenced. COVID-19 COVID-19. COVID-19 Judgements and estimates The accounting estimates and judgements made by management in applying the Group’s accounting policies that have the most significant effect on the amounts included within these financial statements, were the same as those that applied to the annual financial statements for the year ended December 31, 2020.

Income Tax

Income Tax	9 Months Ended
	Sep. 30, 2021
Major Components Of Tax Expense Income [Abstract]
Income tax	3. Income tax For the Three Months Ended September 30, For the Nine Months Ended 2021 2020 2021 2020 (in thousands) (in thousands) £ £ £ £ Current tax: In respect of current period U.K. 1,845 1,230 5,139 3,834 In respect of current period U.S. — — — (1 ) In respect of prior period U.K. 70 (22 ) 70 (22 ) 1,915 1,208 5,209 3,811 Deferred tax: In respect of current period U.S. (4 ) (4 ) (11 ) (13 ) In respect of prior period U.S. — — — (1 ) Income tax credit 1,911 1,204 5,198 3,797 The income tax credit recognized primarily represents the U.K. research and development tax credit. In the United Kingdom, the Company is able to surrender some of its losses for a cash rebate of up to 33.35% of expenditure related to eligible research and development projects. September 30, December 31, (in thousands) £ £ Current income tax receivable U.K. tax 5,140 9,818 U.S. tax 3 4 5,143 9,822 Deferred tax asset U.S. deferred tax asset 34 44

Basic and Diluted Loss Per Shar

Basic and Diluted Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Basic and diluted loss per share	4. Basic and diluted loss per share For the Three Months Ended September 30, For the Nine Months Ended 2021 2020 2021 2020 (in thousands, except per share data) £ £ £ £ Loss for the period (8,041 ) (8,394 ) (26,889 ) (18,421 ) Basic and diluted weighted average number of shares 52,165 35,093 51,994 33,419 £ £ £ £ Basic and diluted loss per share (0.15 ) (0.24 ) (0.52 ) (0.55 ) Basic loss per share is calculated by dividing the loss for the period attributable to the equity holders of the Company by the weighted average number of shares outstanding during the period. The potential shares issued through 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.

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2021
Disclosure Of Intangible Assets [Abstract]
Intangible assets	5. Intangible assets Intangible assets comprise patents with a carrying value of £4.8 million as of September 30, 2021 (as of December 31, 2020: £4.6 million) and computer software with a carrying value of £0.1 million as of September 30, 2021 (as of December 31, 2020: £0.2 million). During the nine months ended September 30, 2021, the Company acquired intangible assets with a cost of £0.5 million in relation to patents. There were no disposals of intangible assets in the nine months ended September 30, 2021.

Other Non-Current Assets

Other Non-Current Assets	9 Months Ended
	Sep. 30, 2021
Disclosure Of Other Noncurrent Assets [Abstract]
Other non-current assets	6. Other non-current September 30, December 31, (in thousands) £ £ Other non-current 2,600 — In April 2021, the Company initiated legal proceedings against Gilead Sciences Ireland UC and Gilead Sciences GmbH for patent infringement in Germany. In June 2021, the Company was requested by the court to provide the defendants with a security of €3.0 million (£2.6 million) to cover the legal costs of the defendants in the event that the Company is unsuccessful in the final outcome of the legal proceedings. In July 2021, the Company provided the security in accordance with the court order by depositing €3.0 million with the court. The extent to which the sum deposited will be reimbursed to the Company is dependent on a range of potential outcomes, and the timing of those outcomes, with respect to the patent infringement litigation in Germany, which is currently indeterminable.

Cash and Cash Equivalents

Cash and Cash Equivalents	9 Months Ended
	Sep. 30, 2021
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	7. Cash and cash equivalents September 30, December 31, (in thousands) £ £ Cash and cash equivalents 71,027 87,356 Cash and cash equivalents comprise cash at banks with maturity terms of three months or less, and is subject to insignificant risk of changes in value. Cash at banks earns interest at fixed or variable rates based on the terms agreed for each account.

Share-based Payments

Share-based Payments	9 Months Ended
	Sep. 30, 2021
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Abstract]
Share-based payments	8. Share-based payments The Company has six share-based payment plans for employees, directors and consultants. The share options granted will be settled in equity. Options granted under each of the six plans have a maximum life of 10 years. 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. As detailed in the table below, during the nine months ended September 30, 2021, 4,164,913 share options were granted under the 2020 Long-Term Incentive Plan (nine months ended September 30, 2020: 2,585,639 share options granted under the 2016 Share Option Scheme and 2020 Long-Term Incentive Plan). Options granted under these plans will vest if the option holder remains under respective contract of employment or contract of service for the agreed vesting period. The share options granted in the period will vest over a period of up to four 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 two 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 three years, the underlying expected volatility was determined by using the average of the historical volatility of similar listed entities as a proxy. Options granted with an estimated life of three years or less, have been valued using the Company’s own historical volatility rates. Options granted on January 13, 2021 February 10, 2021 February 10, 2021 February 10, 2021 Vesting dates January 13, 2022 February 10, 2022 February 10, 2022 February 10, 2022 January 13, 2023 February 10, 2023 February 10, 2023 February 10, 2023 January 13, 2024 February 10, 2024 February 10, 2024 February 10, 2024 January 13, 2025 February 10, 2025 February 10, 2025 February 10, 2025 Volatility 81.42 % 81.45 % 87.66 % 83.86 % Dividend yield 0 % 0 % 0 % 0 % Risk-free investment rate 0.01 % 0.11 % 0.01 % 0.05 % Fair value of option at grant date £ 2.37 £ 2.74 £ 4.49 £ 4.49 Fair value of share at grant date £ 3.92 £ 4.53 £ 4.53 £ 4.53 Exercise price at date of grant £ 3.92 £ 4.53 £ 0.04 £ 0.04 Lapse date January 13, 2031 February 10, 2031 — February 10, 2031 Expected option life (years) 4.5 4.5 2.5 3.5 Number of options granted 200,000 872,775 91,888 337,000 August 11, 2021 September 15, 2021 September 15, 2021 September 15, 2021 Vesting dates August 11, 2022 Sept. 15, 2022 Sept. 15, 2022 Sept. 15, 2022 August 11, 2023 Sept. 15, 2023 Sept. 15, 2023 Sept. 15, 2023 August 11, 2024 Sept. 15, 2024 Sept. 15, 2024 Sept. 15, 2024 August 11, 2025 Sept. 15, 2025 Sept. 15, 2025 Sept. 15, 2025 Volatility 81.07 % 79.60 % 82.06 % 80.90 % Dividend yield 0 % 0 % 0 % 0 % Risk-free investment rate 0.28 % 0.21 % 0.29 % 0.36 % Fair value of option at grant date £ 0.95 £ 1.67 £ 1.67 £ 1.04 Fair value of share at grant date £ 1.57 £ 1.71 £ 1.71 £ 1.71 Exercise price at date of grant £ 1.57 £ 0.04 £ 0.04 £ 1.71 Lapse date August 11, 2031 — Sept. 15, 2031 Sept. 15, 2031 Expected option life (years) 4.5 2.5 3.5 4.5 Number of options granted 430,000 140,650 603,900 1,488,700 For the three months ended September 30, 2021, the Company has recognized £1.3 million of share-based payment expense in the statement of operations (three months ended September 30, 2020: £1.4 million). For the nine months ended September 30, 2021, the Company has recognized £4.9 million of share-based payment expense in the statement of operations (nine months ended September 30, 2020: £3.1 million).

Share Capital and Share Premium

Share Capital and Share Premium	9 Months Ended
	Sep. 30, 2021
Disclosure Of Classes Of Share Capital [Abstract]
Share capital and share premium	9. Share capital and share premium September 30, December 31, (in thousands) £ £ Share capital 2,087 2,047 Share premium 141,049 140,890 143,136 142,937 September 30, December 31, Number (in thousands) Issued share capital comprises: Ordinary shares of £0.04 each 52,180 51,175 Number of Share Share (in thousands) £ £ Fully paid shares: Balance at December 31, 2020 51,175 2,047 140,890 Issue of shares on exercise of options 1,005 40 159 Balance at September 30, 2021 52,180 2,087 141,049

Contingent Liabilities

Contingent Liabilities	9 Months Ended
	Sep. 30, 2021
Disclosure Of Contingent Liabilities [Abstract]
Contingent liabilities	10. Contingent liabilities Under its 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 United Kingdom. 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 price of the Company’s ADSs on The Nasdaq Global Select Market on September 30, 2021, 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 £0.5 million (December 31, 2020: £0.8 million). As referenced in Note 6, in July 2021 the Company provided a security of €3.0 million to cover the legal costs of Gilead Sciences Ireland UC and Gilead Sciences GmbH in the event that the Company is unsuccessful in the final outcome of the patent infringement litigation in Germany. Any cost reimbursement by the Company to the defendants is dependent on a range of potential outcomes, and the timing of those outcomes, with respect to the litigation, which are currently indeterminable. Therefore, no provision has been recognised with respect to these legal costs.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Summary Of Significant Accounting Policies [Abstract]
Basis of preparation	Basis of preparation The unaudited condensed consolidated financial statements (the “financial statements”) for the three months and nine months ended September 30, 2021 have been prepared in accordance with International Accounting Standard 34, “ Interim Financial Reporting ” The financial statements do not include all the information and disclosures required in the annual financial statements, and should be read in conjunction with the Company’s annual financial statements for the year ended December 31, 2020. In the opinion of management, these unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair statement of the results of operations, financial position and cash flows. The results of operations for the three months and nine months ended September 30, 2021 are not necessarily indicative of the results that can be expected for the Company’s fiscal year ending December 31, 2021.
Going concern	Going concern In common with many companies in the biopharmaceutical sector, the Company incurs significant expenditure in its early years as it researches and develops its potential products for market. The Company’s board of directors, having reviewed the operating budgets and development plans, considers that the Company has adequate resources to continue in operation for the foreseeable future. The board of directors is therefore satisfied that it is appropriate to adopt the going concern basis of accounting in preparing the financial statements. The Company believes that its cash and cash equivalents of £71.0 million at September 30, 2021 will be sufficient to fund its current operating plan for at least the next 12 months. Further, the directors have conducted an assessment of the impact of COVID-19 As the Company continues to incur losses, the transition to profitability is dependent upon the successful development, approval and commercialization of its product candidates and achieving a level of revenues adequate to support its cost structure. The Company may never achieve profitability, and unless and until it does, it will continue to need to raise additional capital. There can be no assurances, however, that additional funding will be available on acceptable terms.
COVID-19	COVID-19 In response to the spread of COVID-19, on-site During the early months of the pandemic the Company announced that there was some temporary interruption to the enrollment of new patients in the Company’s ongoing clinical trials. In May 2020, the Company further announced that enrollment of new patients in the Company’s clinical trials had re-commenced. COVID-19 COVID-19. COVID-19
Judgements and estimates	Judgements and estimates The accounting estimates and judgements made by management in applying the Group’s accounting policies that have the most significant effect on the amounts included within these financial statements, were the same as those that applied to the annual financial statements for the year ended December 31, 2020.

Income Tax (Tables)

Income Tax (Tables)	9 Months Ended
	Sep. 30, 2021
Major Components Of Tax Expense Income [Abstract]
Schedule of Major Components of Income Tax	For the Three Months Ended September 30, For the Nine Months Ended 2021 2020 2021 2020 (in thousands) (in thousands) £ £ £ £ Current tax: In respect of current period U.K. 1,845 1,230 5,139 3,834 In respect of current period U.S. — — — (1 ) In respect of prior period U.K. 70 (22 ) 70 (22 ) 1,915 1,208 5,209 3,811 Deferred tax: In respect of current period U.S. (4 ) (4 ) (11 ) (13 ) In respect of prior period U.S. — — — (1 ) Income tax credit 1,911 1,204 5,198 3,797 September 30, December 31, (in thousands) £ £ Current income tax receivable U.K. tax 5,140 9,818 U.S. tax 3 4 5,143 9,822 Deferred tax asset U.S. deferred tax asset 34 44

Basic and Diluted Loss Per Sh_2

Basic and Diluted Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Loss Per Share	For the Three Months Ended September 30, For the Nine Months Ended 2021 2020 2021 2020 (in thousands, except per share data) £ £ £ £ Loss for the period (8,041 ) (8,394 ) (26,889 ) (18,421 ) Basic and diluted weighted average number of shares 52,165 35,093 51,994 33,419 £ £ £ £ Basic and diluted loss per share (0.15 ) (0.24 ) (0.52 ) (0.55 )

Other Non-Current Assets (Table

Other Non-Current Assets (Tables)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Other Noncurrent Assets [Abstract]
Disclosure of Other Non-current Assets	September 30, December 31, (in thousands) £ £ Other non-current 2,600 —

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	9 Months Ended
	Sep. 30, 2021
Cash And Cash Equivalents [Abstract]
Schedule of Cash and Cash Equivalents	September 30, December 31, (in thousands) £ £ Cash and cash equivalents 71,027 87,356

Share-based Payments (Tables)

Share-based Payments (Tables)	9 Months Ended
	Sep. 30, 2021
Text block [abstract]
Summary of Principal Assumptions Used for Valuation of Share Options	Options granted on January 13, 2021 February 10, 2021 February 10, 2021 February 10, 2021 Vesting dates January 13, 2022 February 10, 2022 February 10, 2022 February 10, 2022 January 13, 2023 February 10, 2023 February 10, 2023 February 10, 2023 January 13, 2024 February 10, 2024 February 10, 2024 February 10, 2024 January 13, 2025 February 10, 2025 February 10, 2025 February 10, 2025 Volatility 81.42 % 81.45 % 87.66 % 83.86 % Dividend yield 0 % 0 % 0 % 0 % Risk-free investment rate 0.01 % 0.11 % 0.01 % 0.05 % Fair value of option at grant date £ 2.37 £ 2.74 £ 4.49 £ 4.49 Fair value of share at grant date £ 3.92 £ 4.53 £ 4.53 £ 4.53 Exercise price at date of grant £ 3.92 £ 4.53 £ 0.04 £ 0.04 Lapse date January 13, 2031 February 10, 2031 — February 10, 2031 Expected option life (years) 4.5 4.5 2.5 3.5 Number of options granted 200,000 872,775 91,888 337,000 August 11, 2021 September 15, 2021 September 15, 2021 September 15, 2021 Vesting dates August 11, 2022 Sept. 15, 2022 Sept. 15, 2022 Sept. 15, 2022 August 11, 2023 Sept. 15, 2023 Sept. 15, 2023 Sept. 15, 2023 August 11, 2024 Sept. 15, 2024 Sept. 15, 2024 Sept. 15, 2024 August 11, 2025 Sept. 15, 2025 Sept. 15, 2025 Sept. 15, 2025 Volatility 81.07 % 79.60 % 82.06 % 80.90 % Dividend yield 0 % 0 % 0 % 0 % Risk-free investment rate 0.28 % 0.21 % 0.29 % 0.36 % Fair value of option at grant date £ 0.95 £ 1.67 £ 1.67 £ 1.04 Fair value of share at grant date £ 1.57 £ 1.71 £ 1.71 £ 1.71 Exercise price at date of grant £ 1.57 £ 0.04 £ 0.04 £ 1.71 Lapse date August 11, 2031 — Sept. 15, 2031 Sept. 15, 2031 Expected option life (years) 4.5 2.5 3.5 4.5 Number of options granted 430,000 140,650 603,900 1,488,700

Share Capital and Share Premi_2

Share Capital and Share Premium (Tables)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Classes Of Share Capital [Abstract]
Summary of Share Capital and Share Premium	September 30, December 31, (in thousands) £ £ Share capital 2,087 2,047 Share premium 141,049 140,890 143,136 142,937 September 30, December 31, Number (in thousands) Issued share capital comprises: Ordinary shares of £0.04 each 52,180 51,175
Summary of Movement in the Share Capital	Number of Share Share (in thousands) £ £ Fully paid shares: Balance at December 31, 2020 51,175 2,047 140,890 Issue of shares on exercise of options 1,005 40 159 Balance at September 30, 2021 52,180 2,087 141,049

General Information - Additiona

General Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021Subsidiary
Disclosure Of General Information About Financial Statements [Abstract]
Description of nature of entity's operations	clinical-stage biopharmaceutical company developing a portfolio of new medicines to treat cancer
Name of reporting entity	NuCana plc
Domicile of entity	United Kingdom
Country of incorporation	England and Wales
Number of subsidiaries	3
Name of subsidiary	NuCana, Inc., NuCana Limited and NuCana BioMed Trustee Company Limited

Significant Accounting Polici_3

Significant Accounting Policies - Additional Information (Detail) - GBP (£) £ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Disclosure Of Summary Of Significant Accounting Policies [Abstract]
Cash and cash equivalents	£ 71,027	£ 87,356	£ 100,678	£ 51,962

Income Tax - Schedule of Major

Income Tax - Schedule of Major Components of Income Tax Credit (Detail) - GBP (£) £ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Current tax:
Total current tax	£ 1,915	£ 1,208	£ 5,209	£ 3,811
Deferred tax:
Income tax credit	1,911	1,204	5,198	3,797
U.K. [member]
Current tax:
In respect of current period	1,845	1,230	5,139	3,834
In respect of prior period	70	(22)	70	(22)
U.S. [member]
Current tax:
In respect of current period		0		(1)
Deferred tax:
In respect of current period	£ (4)	£ (4)	£ (11)	(13)
In respect of prior period				£ (1)

Income Tax - Additional Informa

Income Tax - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021
U.K. [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Percentage of losses surrendered for R&D tax credit	33.35%

Income Tax - Schedule of Majo_2

Income Tax - Schedule of Major Components of Income Tax Assets (Detail) - GBP (£) £ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current income tax receivable
Current income tax receivable	£ 5,143	£ 9,822
Deferred tax asset
Deferred tax asset	34	44
U.K. [member]
Current income tax receivable
Current income tax receivable	5,140	9,818
U.S. [member]
Current income tax receivable
Current income tax receivable	3	4
Deferred tax asset
Deferred tax asset	£ 34	£ 44

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	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Loss for the period	£ (8,041)	£ (8,394)	£ (26,889)	£ (18,421)
Basic and diluted weighted average number of shares	52,165	35,093	51,994	33,419
Basic and diluted loss per share	£ (0.15)	£ (0.24)	£ (0.52)	£ (0.55)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - GBP (£) £ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Disclosure of detailed information about intangible assets [line items]
Intangible assets, carrying value	£ 4,896	£ 4,753
Patents [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets, carrying value	4,800	4,600
Intangible assets, acquired	500
Computer Software [member]
Disclosure of detailed information about intangible assets [line items]
Intangible assets, carrying value	£ 100	£ 200

Other Non-Current Asstes - Add

Other Non-Current Asstes - Additional Information (Detail) £ in Millions	Jul. 01, 2021GBP (£)	Jul. 01, 2021EUR (€)	Jun. 30, 2021GBP (£)	Jun. 30, 2021EUR (€)
Disclosure Of Other Noncurrent Assets [Abstract]
Security deposit to cover legal costs			£ 2.6	€ 3,000,000
Payment of security deposit to cover legal costs	£ 3	€ 3,000

Other Non-Current Assets - Disc

Other Non-Current Assets - Disclosure of Other Non-current Assets (Details) - GBP (£) £ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Disclosure Of Other Noncurrent Assets [Line Items]
Other non-current assets	£ 2,600	£ 0

Cash and Cash Equivalents - Sch

Cash and Cash Equivalents - Schedule of Detailed Information About Cash and Cash Equivalents (Detail) - GBP (£) £ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	£ 71,027	£ 87,356	£ 100,678	£ 51,962

Share-based Payments - Addition

Share-based Payments - Additional Information (Details) £ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021GBP (£)	Sep. 30, 2020GBP (£)	Sep. 30, 2021GBP (£)shares	Sep. 30, 2020GBP (£)shares
Disclosure of terms and conditions of share-based payment arrangement [line items]
Share-based payment expense | £	£ 1.3	£ 1.4	£ 4.9	£ 3.1
Long-Term Incentive Plan [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of share options granted in share-based payment arrangement | shares			4,164,913	2,585,639
Share options granted, vesting period			4 years

Share Based Payments - Summary

Share Based Payments - Summary of Principal Assumptions used for Valuation of Share Options (Detail) - 9 months ended Sep. 30, 2021 - 2020 Share Options [member]	GBP (£)sharesSubsidiaryyr£ / shares	GBP (£)sharesSubsidiaryyr$ / shares
Grant Date June 10, 2020 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Lapse date	Jan. 13, 2031	Jan. 13, 2031
Grant Date January 13, 2021 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	81.42%	81.42%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.01%	0.01%
Fair value of option at grant date | £	£ 2,370	£ 2,370
Fair value of share at grant date	£ 3.92
Exercise price at date of grant	£ 3.92
Expected option life (years) | yr	4.5	4.5
Number of options granted | shares	200,000	200,000
Grant Date January 13, 2021 [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Jan. 13, 2022	Jan. 13, 2022
Grant Date January 13, 2021 [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Jan. 13, 2023	Jan. 13, 2023
Grant Date January 13, 2021 [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Jan. 13, 2024	Jan. 13, 2024
Grant Date January 13, 2021 [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Jan. 13, 2025	Jan. 13, 2025
Grant Date February 10, 2021 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	81.45%	81.45%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.11%	0.11%
Fair value of option at grant date | £	£ 2,740	£ 2,740
Fair value of share at grant date	£ 4.53
Exercise price at date of grant	£ 4.53
Lapse date	Feb. 10, 2031	Feb. 10, 2031
Expected option life (years) | yr	4.5	4.5
Number of options granted | shares	872,775	872,775
Grant Date February 10, 2021 [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2022	Feb. 10, 2022
Grant Date February 10, 2021 [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2023	Feb. 10, 2023
Grant Date February 10, 2021 [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2024	Feb. 10, 2024
Grant Date February 10, 2021 [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2025	Feb. 10, 2025
Grant Date February 10, 2021 One [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	87.66%	87.66%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.01%	0.01%
Fair value of option at grant date | £	£ 4,490	£ 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	2.5
Number of options granted | shares	91,888	91,888
Grant Date February 10, 2021 One [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2022	Feb. 10, 2022
Grant Date February 10, 2021 One [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2023	Feb. 10, 2023
Grant Date February 10, 2021 One [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2024	Feb. 10, 2024
Grant Date February 10, 2021 One [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2025	Feb. 10, 2025
Grant Date February 10, 2021 Two [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	83.86%	83.86%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.05%	0.05%
Fair value of option at grant date | £	£ 4,490	£ 4,490
Fair value of share at grant date | $ / shares		£ 4.53
Exercise price at date of grant | $ / shares		£ 0.04
Lapse date	Feb. 10, 2031	Feb. 10, 2031
Expected option life (years) | yr	3.5	3.5
Number of options granted | Subsidiary	337,000	337,000
Grant Date February 10, 2021 Two [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2022	Feb. 10, 2022
Grant Date February 10, 2021 Two [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2023	Feb. 10, 2023
Grant Date February 10, 2021 Two [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2024	Feb. 10, 2024
Grant Date February 10, 2021 Two [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Feb. 10, 2025	Feb. 10, 2025
Grant Date August 11, 2021 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	81.07%	81.07%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.28%	0.28%
Fair value of option at grant date | £	£ 950	£ 950
Fair value of share at grant date	£ 1.57
Exercise price at date of grant	£ 1.57
Lapse date	Aug. 11, 2031	Aug. 11, 2031
Expected option life (years) | yr	4.5	4.5
Number of options granted | Subsidiary	430,000	430,000
Grant Date August 11, 2021 [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Aug. 11, 2022	Aug. 11, 2022
Grant Date August 11, 2021 [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Aug. 11, 2023	Aug. 11, 2023
Grant Date August 11, 2021 [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Aug. 11, 2024	Aug. 11, 2024
Grant Date August 11, 2021 [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Aug. 11, 2025	Aug. 11, 2025
Grant Date September 15, 2021 [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	79.60%	79.60%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.21%	0.21%
Fair value of option at grant date | £	£ 1,670	£ 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	2.5
Number of options granted | Subsidiary	140,650	140,650
Grant Date September 15, 2021 [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2022	Sep. 15, 2022
Grant Date September 15, 2021 [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2023	Sep. 15, 2023
Grant Date September 15, 2021 [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2024	Sep. 15, 2024
Grant Date September 15, 2021 [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2025	Sep. 15, 2025
Grant Date September 15 2021 One [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	82.06%	82.06%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.29%	0.29%
Fair value of option at grant date | £	£ 1,670	£ 1,670
Fair value of share at grant date	£ 1.71
Exercise price at date of grant	£ 0.04
Lapse date	Sep. 15, 2031	Sep. 15, 2031
Expected option life (years) | yr	3.5	3.5
Number of options granted | Subsidiary	603,900	603,900
Grant Date September 15 2021 One [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2022	Sep. 15, 2022
Grant Date September 15 2021 One [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2023	Sep. 15, 2023
Grant Date September 15 2021 One [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2024	Sep. 15, 2024
Grant Date September 15 2021 One [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2025	Sep. 15, 2025
Grant Date September 15 2021 Two [Member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Volatility	80.90%	80.90%
Dividend yield	0.00%	0.00%
Risk-free investment rate	0.36%	0.36%
Fair value of option at grant date | £	£ 1,040	£ 1,040
Fair value of share at grant date | $ / shares		£ 1.71
Exercise price at date of grant | $ / shares		£ 1.71
Lapse date	Sep. 15, 2031	Sep. 15, 2031
Expected option life (years) | yr	4.5	4.5
Number of options granted | Subsidiary	1,488,700	1,488,700
Grant Date September 15 2021 Two [Member] | Vesting Dates One [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2022	Sep. 15, 2022
Grant Date September 15 2021 Two [Member] | Vesting Dates Two [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2023	Sep. 15, 2023
Grant Date September 15 2021 Two [Member] | Vesting Dates Three [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2024	Sep. 15, 2024
Grant Date September 15 2021 Two [Member] | Vesting Dates Four [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting dates	Sep. 15, 2025	Sep. 15, 2025

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	Sep. 30, 2021	Dec. 31, 2020
Disclosure Of Classes Of Share Capital [Abstract]
Share capital	£ 2,087	£ 2,047
Share premium	141,049	140,890
Share capital and share premium	£ 143,136	£ 142,937
Ordinary shares of £0.04 each	52,180	51,175

Share Capital and Share Premi_4

Share Capital and Share Premium - Summary of Share Capital and Share Premium (Parenthetical) (Detail)	Sep. 30, 2021£ / shares	Dec. 31, 2020$ / shares
Ordinary shares [member]
Disclosure of classes of share capital [line items]
Par value per share | (per share)	£ 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	9 Months Ended
	Sep. 30, 2021GBP (£)shares	Sep. 30, 2020GBP (£)
Disclosure of classes of share capital [line items]
Beginning balance, Shares | shares	51,175
Beginning balance	£ 99,230	£ 63,522
Issue of shares on exercise of options | shares	1,005
Issue of shares on exercise of options	£ 181	15
Ending balance, Shares | shares	52,180
Ending balance	£ 77,447	110,274
Share Capital [member]
Disclosure of classes of share capital [line items]
Beginning balance	2,047	1,299
Issue of shares on exercise of options	40	1
Ending balance	2,087	2,047
Share Premium [member]
Disclosure of classes of share capital [line items]
Beginning balance	140,890	79,541
Issue of shares on exercise of options	159	14
Ending balance	£ 141,049	£ 140,890

Contingent Liabilities - Additi

Contingent Liabilities - Additional Information (Detail) £ in Millions	Jul. 01, 2021GBP (£)	Jul. 01, 2021EUR (€)	Sep. 30, 2021GBP (£)	Dec. 31, 2020GBP (£)
Disclosure Of Contingent Liabilities [Abstract]
Prevailing rate of employer national insurance			13.80%
Employer national insurance contingent liability			£ 0.5	£ 0.8
Payment of security deposit to cover legal costs	£ 3	€ 3,000