Adaptimmune Therapeutics (ADAP) 10-K 6 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2022	Mar. 03, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Document Transition Report	false
Entity File Number	001-37368
Entity Registrant Name	ADAPTIMMUNE THERAPEUTICS PLC
Entity Incorporation, State or Country Code	X0
Entity Address, Address Line One	60 Jubilee Avenue, Milton Park
Entity Address, City or Town	Abingdon, Oxfordshire
Entity Address, Country	GB
Entity Address, Postal Zip Code	OX14 4RX
City Area Code	44
Entity Tax Identification Number	00-0000000
Title of 12(b) Security	American Depositary Shares, each representing
Local Phone Number	1235 430000
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Trading Symbol	ADAP
Entity Common Stock, Shares Outstanding		991,831,158
Entity Public Float			$ 244,288,811
Entity Central Index Key	0001621227
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false
Auditor Name	KPMG LLP
Auditor Firm ID	1118
Auditor Location	Reading, United Kingdom

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 108,033,000	$ 149,948,000
Marketable securities - available-for-sale debt securities	96,572,000	219,632,000
Accounts receivable, net of allowance for doubtful accounts of $0 and $0	7,435,000	752,000
Other current assets and prepaid expenses	43,330,000	45,126,000
Total current assets	255,370,000	415,458,000
Restricted cash	1,569,000	1,718,000
Operating lease right-of-use assets, net of accumulated amortization of $9,470 and $7,253	18,019,000	20,875,000
Property, plant and equipment, net of accumulated depreciation of $38,588 and $36,253	53,516,000	30,494,000
Intangible assets, net of accumulated amortization of $4,676 and $4,051	442,000	1,000,000
Total assets	328,916,000	469,545,000
Current liabilities
Accounts payable	4,753,000	8,113,000
Operating lease liabilities, current	2,728,000	2,320,000
Accrued expenses and other current liabilities	31,215,000	29,909,000
Restructuring provision	2,285,000
Deferred revenue, current	23,520,000	22,199,000
Total current liabilities	64,501,000	62,541,000
Operating lease liabilities, non-current	20,349,000	23,148,000
Deferred revenue, non-current	160,892,000	177,223,000
Other liabilities, non-current	1,296,000	673,000
Total liabilities	247,038,000	263,585,000
Stockholders' equity
Common stock - Ordinary shares par value £0.001, 1,282,773,750 authorized and 982,719,936 issued and outstanding (2021: 1,240,853,520 authorized and 937,547,934 issued and outstanding)	1,399,000	1,337,000
Additional paid in capital	990,656,000	959,611,000
Accumulated other comprehensive loss	(875,000)	(11,142,000)
Accumulated deficit	(909,302,000)	(743,846,000)
Total stockholders' equity	81,878,000	205,960,000
Total liabilities and stockholders' equity	$ 328,916,000	$ 469,545,000

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares
CONSOLIDATED BALANCE SHEETS
Allowance for doubtful accounts	$ 0	$ 0
Property, plant and equipment, accumulated depreciation	38,588	36,253
Intangibles, accumulated amortization	4,676	4,051
Operating lease right-of-use assets, accumulated amortization	$ 9,470	$ 7,253
Common stock, shares authorized | shares	1,282,773,750	1,240,853,520
Common stock, shares issued | shares	987,109,890	937,547,934
Common stock, shares outstanding | shares	987,109,890	928,547,934

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue	$ 27,148	$ 6,149	$ 3,958
Operating expenses
Research and development	(127,726)	(111,090)	(91,568)
General and administrative	(63,387)	(57,305)	(45,795)
Total operating expenses	(191,113)	(168,395)	(137,363)
Operating loss	(163,965)	(162,246)	(133,405)
Interest income	1,542	1,095	2,313
Other (expense) income, net	(536)	3,852	1,162
Loss before income tax expense	(162,959)	(157,299)	(129,930)
Income tax expense	(2,497)	(791)	(162)
Net loss attributable to ordinary shareholders	$ (165,456)	$ (158,090)	$ (130,092)
Net loss per ordinary share
Basic (in dollars per share)	$ (0.17)	$ (0.17)	$ (0.15)
Diluted (in dollars per share)	$ (0.17)	$ (0.17)	$ (0.15)
Weighted average shares outstanding:
Basic (in shares)	967,242,403	934,833,017	854,783,763
Diluted (in shares)	967,242,403	934,833,017	854,783,763

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Net loss	$ (165,456)	$ (158,090)	$ (130,092)
Other comprehensive (loss) income, net of tax
Foreign currency translation adjustments, net of tax of $0, $0 and $0	60,421	5,808	(19,220)
Foreign currency (losses) gains on intercompany loan of a long-term investment nature, net of tax of $0, $0 and $0	(49,581)	(6,435)	16,364
Unrealized holding (losses) gains on available-for-sale debt securities, net of tax of $0 ,$0, and $0	(573)	(461)	161
Reclassification adjustment for gains on available-for-sale debt securities included in net loss, net of tax of $0, $0, and $0		(6)	(89)
Total comprehensive loss for the period	$ (155,189)	$ (159,184)	$ (132,876)

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Foreign currency translation adjustments, tax	$ 0	$ 0	$ 0
Foreign currency (losses) gains on intercompany loan of a long-term investment nature, tax	0	0	0
Unrealized holding (losses) gains on available-for-sale debt securities, tax	0	0	0
Reclassification adjustment for gains on available-for-sale debt securities included in net loss, tax	$ 0	$ 0	$ 0

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGE IN EQUITY - USD ($) $ in Thousands	Common stock January Offering	Common stock Over Allotment January	Common stock June Offering	Common stock Over Allotment June	Common stock	Additional paid in capital January Offering	Additional paid in capital Over Allotment January	Additional paid in capital June Offering	Additional paid in capital Over Allotment June	Additional paid in capital	Accumulated other comprehensive (loss) income	Accumulated deficit	January Offering	Over Allotment January	June Offering	Over Allotment June	Total
Balance at the beginning of the period, shares at Dec. 31, 2019					631,003,568
Balance at the beginning of the period at Dec. 31, 2019					$ 943					$ 585,623	$ (7,264)	$ (455,664)					$ 123,638
Increase (Decrease) in Stockholders' Equity
Issuance of shares upon exercise of stock options					$ 14					5,649							$ 5,663
Issuance of shares upon exercise of stock options (in shares)					11,401,390												11,401,390
Issuance of common stock	$ 165	$ 24	$ 155	$ 24		$ 78,451	$ 11,914	$ 209,831	$ 33,824				$ 78,616	$ 11,938	$ 209,986	$ 33,848
Issue of common stock (in shares)	126,000,000	18,900,000	123,000,000	18,450,000
Other comprehensive loss											(2,784)						$ (2,784)
Share-based compensation expense										10,414							10,414
Net loss												(130,092)					(130,092)
Balance at the end of the period at Dec. 31, 2020					$ 1,325					935,706	(10,048)	(585,756)					341,227
Balance at the end of the period, shares at Dec. 31, 2020					928,754,958
Increase (Decrease) in Stockholders' Equity
Issuance of shares upon exercise of stock options					$ 8					$ 751							$ 759
Issuance of shares upon exercise of stock options (in shares)					5,723,646												5,723,646
Issue of shares under At The Market sales agreement, net of commission and expenses (in shares)					3,069,330
Issue of shares under At The Market sales agreement, net of commission and expenses					4,000					2,525,000							2,529,000
Other comprehensive loss											(1,094)						$ (1,094)
Share-based compensation expense										$ 20,629							20,629
Net loss												(158,090)					(158,090)
Balance at the end of the period at Dec. 31, 2021					$ 1,337					959,611	(11,142)	(743,846)					$ 205,960
Balance at the end of the period, shares at Dec. 31, 2021					937,547,934												928,547,934
Increase (Decrease) in Stockholders' Equity
Issuance of shares upon exercise of stock options					$ 8					$ 42							$ 50
Issuance of shares upon exercise of stock options (in shares)					5,823,534												5,823,534
Issue of shares under At The Market sales agreement, net of commission and expenses (in shares)					43,738,422
Issue of shares under At The Market sales agreement, net of commission and expenses					54,000					12,763,000							12,817,000
Other comprehensive loss											10,267						$ 10,267
Share-based compensation expense										$ 18,240							18,240
Net loss												(165,456)					(165,456)
Balance at the end of the period at Dec. 31, 2022					$ 1,399					$ 990,656	$ (875)	$ (909,302)					$ 81,878
Balance at the end of the period, shares at Dec. 31, 2022					987,109,890												987,109,890

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities
Net loss	$ (165,456,000)	$ (158,090,000)	$ (130,092,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	5,266,000	5,630,000	6,627,000
Amortization	809,000	937,000	967,000
Share-based compensation expense	18,240,000	20,629,000	10,414,000
Unrealized foreign exchange (gains)/losses	(2,438,000)	540,000	(1,333,000)
Amortization on available-for-sale debt securities	2,525,000	5,276,000	3,836,000
Other	816,000	1,173,000	(55,000)
Changes in operating assets and liabilities:
(Increase)/decrease in receivables and other operating assets	(9,813,000)	(19,358,000)	1,747,000
Decrease in non-current operating assets			2,458,000
Increase in payables and other current liabilities	4,408,000	4,207,000	3,867,000
Increase in deferred revenue	3,874,000	149,785,000	47,973,000
Net cash (used in)/provided by operating activities	(141,769,000)	10,729,000	(53,591,000)
Cash flows from investing activities
Acquisition of property, plant and equipment	(29,496,000)	(8,574,000)	(2,341,000)
Acquisition of intangibles assets	(244,000)	(207,000)	(565,000)
Maturity or redemption of marketable securities	166,994,000	224,343,000	105,022,000
Investment in marketable securities	(48,117,000)	(139,762,000)	(381,040,000)
Net cash provided by/(used in) investing activities	89,137,000	75,800,000	(278,924,000)
Cash flows from financing activities
Proceeds from issuance of common stock from offerings, net of commissions and issuance costs	12,817,000	2,529,000	334,388,000
Proceeds from exercise of stock options	50,000	759,000	5,663,000
Net cash provided by financing activities	12,867,000	3,288,000	340,051,000
Effect of currency exchange rate changes on cash, cash equivalents and restricted cash	(2,299,000)	365,000	(960,000)
Net (decrease)/increase in cash, cash equivalents and restricted cash	(42,064,000)	90,182,000	6,576,000
Cash, cash equivalents and restricted cash at start of period	151,666,000	61,484,000	54,908,000
Cash, cash equivalents and restricted cash at end of period	109,602,000	151,666,000	61,484,000
Supplemental cash flow information
Interest received	5,149,000	7,765,000	6,216,000
Amortization on available-for-sale debt securities	2,525,000	5,276,000	3,836,000
Income taxes paid	$ 630,000	$ 535,000	$ 75,000

General

General	12 Months Ended
	Dec. 31, 2022
General
General	Note 1 — General Adaptimmune Therapeutics plc is registered in England and Wales. Its registered office is 60 Jubilee Avenue, Milton Park, Abingdon, Oxfordshire, OX14 4RX, United Kingdom. Adaptimmune Therapeutics plc and its subsidiaries (collectively “Adaptimmune” or the “Company”) is a clinical-stage biopharmaceutical company primarily focused on providing novel cell therapies to people with cancer. The Company is The Company is subject to a number of risks similar to other biopharmaceutical companies in the early stage of clinical development including, but not limited to, the need to obtain adequate additional funding, possible failure of preclinical programs or clinical programs, the need to obtain marketing approval for its cell therapies, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of its cell therapies, the need to develop a reliable commercial manufacturing process, the need to commercialize any cell therapies that may be approved for marketing, and protection of proprietary technology. If the Company does not successfully commercialize any of its cell therapies , it will be unable to generate product revenue or achieve profitability. The Company had an accumulated deficit of

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2 — Summary of Significant Accounting Policies (a) Basis of presentation The Consolidated Financial Statements of Adaptimmune Therapeutics plc and its subsidiaries and other financial information included in this Annual Report have been prepared in accordance with generally accepted accounting principles in the United States of America (“US GAAP”) and are presented in U.S. dollars. All significant intercompany accounts and transactions between the Company and its subsidiaries have been eliminated on consolidation. (b) Use of estimates in financial statements The preparation of financial statements, in conformity with U.S. GAAP and SEC regulations, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the Consolidated Financial Statements and reported amounts of revenues and expenses during the reporting period. Estimates and assumptions are primarily made in relation to revenue recognition, estimation of the incremental borrowing rate for operating leases, and valuation allowances relating to deferred tax assets. If actual results differ from the Company’s estimates, or to the extent these estimates are adjusted in future periods, the Company’s results of operations could either benefit from, or be adversely affected by, any such change in estimate. (c) Going concern In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. Management considers that there are no conditions or events, in the aggregate, that raise substantial doubt about the entity’s ability to continue as a going concern for a period of at least one year from the date the financial statements are issued. Although the financial statements have been prepared on a going concern basis, if the Company fails to obtain sufficient additional financing in future, this may raise substantial doubt over the Company’s ability to continue as a going concern in future reporting periods. ​ (d) Foreign currency The reporting currency of the Company is the U.S. dollar. The Company has determined the functional currency of the ultimate parent company, Adaptimmune Therapeutics plc, is U.S. dollars because it predominately raises finance and expends cash in U.S. dollars. The functional currency of subsidiary operations is the applicable local currency. Transactions in foreign currencies are translated into the functional currency of the subsidiary in which they occur at the foreign exchange rate in effect on at the date of the transaction. Monetary assets and liabilities denominated in foreign currencies at the balance sheet date are translated into the functional currency of the relevant subsidiary at the foreign exchange rate in effect on the balance sheet date. Foreign exchange differences arising on translation are recognized within other income (expense) in the Consolidated Statement of Operations. The Company’s U.K. subsidiary has an intercompany loan balance in U.S dollars payable to the ultimate parent company, Adaptimmune Therapeutics plc. Beginning on July 1, 2019, the intercompany loan was considered of a long-term investment nature as repayment is not planned or anticipated in the foreseeable future. It is Adaptimmune Therapeutics plc’s intent not to request payment of the intercompany loan for the foreseeable future. The foreign exchange gain or losses arising on the revaluation of intercompany loans of a long-term investment nature are reported within other comprehensive (loss) income, net of tax. ​ The results of operations for subsidiaries, whose functional currency is not the U.S. dollar, are translated at an average rate for the period where this rate approximates to the foreign exchange rates ruling at the dates of the transactions and the balance sheet are translated at foreign exchange rates ruling at the balance sheet date. Exchange differences arising from this translation of foreign operations are reported as an item of other comprehensive (loss) income. ​ Foreign exchange losses for the year ended December 31, 2022 of $536,000 and foreign exchange gains of $3,852,000 and $1,105,000 for the years ended December 31, 2021 and 2020 respectively, are included within Other (expense) income, net in the Consolidated Statement of Operations. ​ (e) Fair value measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The hierarchy defines three levels of valuation inputs: Level 1 — Quoted prices in active markets for identical assets or liabilities Level 2 — Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly Level 3 — Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability The carrying amounts of the Company’s cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses approximate fair value because of the short-term nature of these instruments. The fair value of marketable securities, which are measured at fair value on a recurring basis is detailed in Note 4, Financial Instruments. ​ (f) Accumulated other comprehensive (loss) income The Company reports foreign currency translation adjustments and the foreign exchange gain or losses arising on the revaluation of intercompany loans of a long-term investment nature within Other comprehensive (loss) income. Unrealized gains and losses on available-for-sale debt securities are also reported within Other comprehensive (loss) income until a gain or loss is realized, at which point they are reclassified to Other (expense) income, net in the Consolidated Statement of Operations. The following table shows the changes in Accumulated other comprehensive (loss) income (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ Accumulated ​ ​ Total ​ ​ foreign ​ unrealized ​ ​ accumulated ​ ​ currency ​ gains (losses) on ​ ​ other ​ translation available-for-sale ​ ​ comprehensive ​ ​ adjustments ​ debt securities ​ ​ (loss) income ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at January 1, 2020 $ (7,302) ​ $ 38 ​ $ (7,264) Foreign currency translation adjustments ​ ​ (19,220) ​ ​ — ​ ​ (19,220) Foreign currency gains on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ 16,364 ​ ​ — ​ ​ 16,364 Unrealized holding gains on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ 161 ​ ​ 161 Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0 ​ ​ — ​ ​ (89) ​ ​ (89) Balance at December 31, 2020 ​ ​ (10,158) ​ ​ 110 ​ ​ (10,048) Foreign currency translation adjustments ​ ​ 5,808 ​ ​ — ​ ​ 5,808 Foreign currency losses on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ (6,435) ​ ​ — ​ ​ (6,435) Unrealized holding losses on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ (461) ​ ​ (461) Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0 ​ ​ — ​ ​ (6) ​ ​ (6) Balance at December 31, 2021 ​ ​ (10,785) ​ ​ (357) ​ ​ (11,142) Foreign currency translation adjustments ​ ​ 60,421 ​ ​ — ​ ​ 60,421 Foreign currency losses on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ (49,581) ​ ​ — ​ ​ (49,581) Unrealized holding losses on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ (573) ​ ​ (573) Balance at December 31, 2022 ​ $ 55 ​ $ (930) ​ $ (875) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following amounts were reclassified out of Other comprehensive (loss) income (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount reclassified ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ Affected line item in ​ ​ ​ ​ ​ ​ ​ ​ ​ Component of accumulated other comprehensive income ​ 2022 ​ 2021 ​ 2020 ​ the Statement of Operations Unrealized gains on available-for-sale securities ​ ​ ​ ​ ​ ​ Reclassification adjustment for gains on available-for-sale debt securities $ — ​ $ (6) ​ $ (89) ​ Other (expense) income, net ​ ​ (g) Cash, cash equivalents and restricted cash The Company considers all highly liquid investments with a maturity at acquisition date of three months or less to be cash equivalents. Cash and cash equivalents comprise cash balances, commercial paper and corporate debt securities with maturities of three months or less at acquisition and short deposits with maturities of three months or less. The Company’s restricted cash consists of cash providing security for letters of credit in respect of lease agreements and credit cards. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same such amounts shown in the statement of cash flows (in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 108,033 ​ $ 149,948 Restricted cash ​ 1,569 ​ 1,718 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows ​ $ 109,602 ​ $ 151,666 ​ (h ) Available-for-sale debt securities As of December 31, 2022, the Company has the following investments in available-for-sale debt securities, (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Aggregate ​ ​ Remaining ​ Amortized ​ unrealized ​ unrealized ​ estimated ​ contractual maturity cost gains losses fair value Available-for-sale debt securities: ​ ​ ​ ​ Corporate debt securities Less than 3 months ​ $ 45,386 ​ $ — ​ $ (72) ​ $ 45,314 U.S. Treasury securities ​ Less than 3 months ​ ​ 5,953 ​ ​ 1 ​ ​ — ​ ​ 5,954 Agency bonds ​ 3 months to 1 year ​ ​ 5,008 ​ ​ — ​ ​ (154) ​ ​ 4,854 Corporate debt securities ​ 3 months to 1 year ​ ​ 41,154 ​ ​ — ​ ​ (704) ​ ​ 40,450 ​ ​ $ 97,501 ​ $ 1 ​ $ (930) ​ $ 96,572 ​ ​ As of December 31, 2021, the Company had the following investments in available-for-sale debt securities (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Aggregate ​ ​ Remaining ​ Amortized ​ unrealized ​ unrealized ​ estimated ​ contractual maturity cost gains losses fair value Available-for-sale debt securities: ​ ​ ​ ​ Corporate debt securities Less than 3 months ​ $ 45,304 ​ $ 22 ​ $ (21) ​ $ 45,305 Corporate debt securities ​ 3 months to 1 year ​ ​ 81,590 ​ ​ 11 ​ ​ (75) ​ ​ 81,526 Agency bonds ​ 1 year to 2 years ​ ​ 5,000 ​ ​ — ​ ​ (7) ​ ​ 4,993 Corporate debt securities ​ 1 year to 2 years ​ ​ 88,095 ​ ​ — ​ ​ (287) ​ ​ 87,808 ​ ​ $ 219,989 ​ $ 33 ​ $ (390) ​ $ 219,632 ​ At December 31, 2022, the Company has classified all of its available-for-sale debt securities as current assets on the accompanying Consolidated Balance Sheets based on the highly-liquid nature of these investment securities and because these investment securities are considered available for use in current operations. The investment in available-for-sale debt securities is measured at fair value at each reporting date. Unrealized gains and losses are excluded from earnings and are reported as a component of Other comprehensive (loss) income, net of tax. Realized gains and losses are included in Other income (expense), net. Interest income and amortization of premiums and discounts at acquisition are included in Interest income. In the year ended December 31, 2022, 2021 and 2020 proceeds from the maturity or redemption of available-for-sale debt securities were At each reporting date, the Company assesses whether each individual investment is impaired, which occurs if the fair value is less than the amortized cost, adjusted for amortization of premiums and discounts at acquisition. If the investment is impaired, the impairment is assessed to determine if it is other than temporary. Impairments judged to be other than temporary are included in other (expense) income, net when they are identified. The aggregate fair value (in thousands) and number of securities held by the Company (including those classified as cash equivalents) in an unrealized loss position as of December 31, 2022 and 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ December 31, 2021 ​ Fair market value of investments in an unrealized loss position ​ Number of investments in an unrealized loss position ​ Unrealized losses ​ Fair market value of investments in an unrealized loss position ​ Number of investments in an unrealized loss position ​ Unrealized losses Marketable securities in a continuous loss position for 12 months or longer: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 74,481 ​ ​ 16 ​ $ (679) ​ $ 8,232 ​ ​ 1 ​ $ (35) Agency bond ​ ​ 4,854 ​ ​ 1 ​ ​ (154) ​ ​ — ​ ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities in a continuous loss position for less than 12 months: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities $ 11,283 ​ 2 ​ $ (97) $ 163,258 ​ 34 $ (348) Agency bond ​ ​ — ​ ​ — ​ ​ — ​ ​ 4,993 ​ ​ 1 ​ ​ (7) ​ $ 90,618 ​ 19 ​ $ (930) $ 176,483 ​ 36 $ (390) ​ As of December 31, 2022 and 2021, these securities are not considered to be other than temporarily impaired because the impairments are not severe and are due to normal market and exchange rate fluctuations. Nineteen securities have been in an unrealized loss position for more than one year with a net total unrealized loss of $833,000. Furthermore, the Company does not intend to sell the debt securities in an unrealized loss position, and it is unlikely that the Company will be required to sell these securities before the recovery of the amortized cost. The cost of securities sold is based on the specific-identification method. Interest on debt securities is included in interest income. Our investment in available-for-sale debt securities is subject to credit risk. The Company’s investment policy limits investments to certain types of instruments, such as money market instruments and corporate debt securities, places restrictions on maturities and concentration by type and issuer and specifies the minimum credit ratings for all investments and the average credit quality of the portfolio. (i) Accounts receivable Accounts receivable include amounts billed to customers and accrued receivables where only the passage of time is required before payment of amounts due. Management analyses current and past due accounts and determines if an allowance for uncollectible accounts is required based on collection experience and other relevant information. As of December 31, 2022 and 2021, the allowance for doubtful accounts is $nil. The process of estimating the uncollectible accounts involves assumptions and judgments and the ultimate amounts of uncollectible accounts receivable could be in excess of the amounts provided. (j) Clinical materials Clinical materials for use in research and development with alternative future use are capitalized as either other current assets or other non-current assets, depending on the timing of their expected consumption. The Company assesses whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. (k) Property, plant and equipment Property, plant and equipment is stated at cost, less any impairment losses, less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. The following table provides the range of estimated useful lives used for each asset type: ​ ​ ​ Computer equipment 3 to 5 years Laboratory equipment 5 years Office equipment 5 years Leasehold improvements the expected duration of the lease ​ Assets under construction are not depreciated until the asset is available and ready for its intended use. The Company assesses property, plant and equipment for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. (l) Intangibles Intangibles primarily include acquired software licenses and third party software in development, which are recorded at cost and amortized over the estimated useful lives of approximately three years. Intangibles are assessed for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. ​ (m) Leases The Company determines whether an arrangement is a lease at contract inception by establishing if the contract conveys the right to use, or control the use of, identified property, plant, or equipment for a period of time in exchange for consideration. Leases may be classified as finance leases or operating leases. All the Company’s leases are classified as operating leases. Operating lease right-of-use (ROU) assets and operating lease liabilities recognized in the Consolidated Balance Sheet represent the right to use an underlying asset for the lease term and an obligation to make lease payments arising from the lease respectively. Operating lease ROU assets and operating lease liabilities are recognized at the lease commencement date based on the present value of minimum lease payments over the lease term. Since the rate implicit in the lease is not readily determinable, the Company uses its incremental borrowing rates (the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term for an amount equal to the lease payments in a similar economic environment) based on the information available at commencement date in determining the discount rate used to calculate the present value of lease payments. As the Company has no external borrowings, the incremental borrowing rates are determined using information on indicative borrowing rates that would be available to the Company based on the value, currency and borrowing term provided by financial institutions, adjusted for company and market specific factors. The lease term is based on the non-cancellable period in the lease contract, and options to extend the lease are included when it is reasonably certain that the Company will exercise that option. Any termination fees are included in the calculation of the ROU asset and lease liability when it is assumed that the lease will be terminated. The Company accounts for lease components (e.g. fixed payments including rent and termination costs) separately from non-lease components (e.g. common-area maintenance costs and service charges based on utilization) which are recognized over the period in which the obligation occurs. At each reporting date, the operating lease liabilities are increased by interest and reduced by repayments made under the lease agreements. The ROU asset is subsequently measured for an operating lease at the amount of the remeasured lease liability (i.e. the present value of the remaining lease payments), adjusted for the remaining balance of any lease incentives received, any cumulative prepaid or accrued rent if the lease payments are uneven throughout the lease term, and any unamortized initial direct costs. The Company has operating leases in relation to property for office and research facilities. All of the leases have termination options, and it is assumed that the initial termination options for the buildings will be activated for most of these. The maximum lease term without activation of termination options is to 2041. In May 2017, the Company entered into an agreement for the lease of a building at Milton Park, Oxfordshire, United Kingdom and in February 2018 the Company entered into the lease for that facility. The term of the lease expires on October 23, 2041, with termination options exercisable by the Company in October 2031 and October 2036. In September 2015, the Company entered into an agreement for a 25-year In July 2015, the Company entered into a 15-year 123 months In August 2021, the Company entered into a two-year The Company has elected not to recognize an ROU asset and lease liability for short-term leases. A short-term lease is a lease with a lease term of 12 months or less and which does not include an option to purchase the underlying asset that the lessee is reasonably certain to exercise. Operating lease costs are recognized on a straight-line basis over the lease term, and they are categorized within Research and development and General and administrative expenses in the Consolidated Statement of Operations. The operating lease cash flows are categorized under Net cash used in operating activities in the Consolidated Statement of Cash Flows. (n) Segmental reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company’s chief operating decision maker (the “CODM”), its Chief Executive Officer, manages the Company’s operations on an integrated basis for the purposes of allocating resources. When evaluating the Company’s financial performance, the CODM reviews total revenues, total expenses and expenses by function and the CODM makes decisions using this information on a global basis. Accordingly, the Company has determined that it operates in one operating segment. (o) Revenue Revenue is recognized so as to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve that core principle, an entity should apply the following steps: ​ Step 1: Identify the contract(s) with a customer. Step 2: Identify the performance obligations in the contract. Step 3: Determine the transaction price. Step 4: Allocate the transaction price to the performance obligations in the contract. Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation. ​ Variable consideration The Company determines the variable consideration to be included in the transaction price by estimating the most likely amount that will be received and then applies a constraint to reduce the consideration to the amount which is probable of being received. The determination of whether a milestone is probable includes consideration of the following factors: · whether achievement of a development milestone is highly susceptible to factors outside the entity’s influence, such as milestones involving the judgment or actions of third parties, including regulatory bodies or the customer; ​ · whether the uncertainty about the achievement of the milestone is not expected to be resolved for a long period of time; ​ · whether the Company can reasonably predict that a milestone will be achieved based on previous experience; and ​ · the complexity and inherent uncertainty underlying the achievement of the milestone. ​ Percentage of completion The determination of the percentage of completion requires the Company to estimate the costs-to-complete the project. The Company makes a detailed estimate of the costs-to-complete, which is re-assessed every reporting period based on the latest project plan and discussions with project teams. If a change in facts or circumstances occurs, the estimate will be adjusted and the revenue will be recognized based on the revised estimate. The difference between the cumulative revenue recognized based on the previous estimate and the revenue recognized based on the revised estimate would be recognized as an adjustment to revenue in the period in which the change in estimate occurs. Contract assets and liabilities The Company recognizes a contract asset, when the value of satisfied (or part satisfied) performance obligations is in excess of the payment due to the Company, and deferred revenue (contract liability) when the amount of unconditional consideration is in excess of the value of satisfied (or part satisfied) performance obligations. Once a right to receive consideration is unconditional, that amount is presented as a receivable. Changes in deferred revenue typically arise due to: ● adjustments arising from a change in the estimate of the cost to complete the project, which results in a cumulative catch-up adjustment to revenue that affects the corresponding contract asset or deferred revenue; ​ ● a change in the estimate of the transaction price due to changes in the assessment of whether variable consideration is constrained because it is not considered probable of being received; ​ ● the recognition of revenue arising from deferred revenue; and ​ ● the reclassification of amounts to receivables when a right to consideration to becomes unconditional. ​ A change in the estimate of variable consideration constrained (for example, if a development milestone becomes probable of being received) could result in a significant change in the revenue recognized and deferred revenue. (p) Research and development expenditures Research and development expenditures are expensed as incurred. Expenses related to clinical trials are recognized as services are received. Nonrefundable advance payments for services are deferred and recognized in the Consolidated Statement of Operations as the services are rendered. This determination is based on an estimate of the services received and there may be instances when the payments to vendors exceed the level of services provided resulting in a prepayment of the clinical expense. If the actual timing of the performance of services varies from our estimate, the accrual or prepaid expense is adjusted accordingly. Upfront and milestone payments to third parties for in-licensed products or technology which has not yet received regulatory approval and which does not have alternative future use in R&D projects or otherwise are expensed as incurred. The Company expensed acquired in-process R&D of $2,316,000, $562,000 and $889,000 in the years ended December 31, 2022, 2021 and 2020, respectively. Milestone payments made to third parties either on or subsequent to regulatory approval are capitalized as an intangible asset and amortized over the remaining useful life of the product. Research and development expenditure is presented net of R&D tax and expenditure credits from the U.K. government, which are recognized over the period necessary to match the reimbursement with the related costs when it is probable that the Company has complied with any conditions attached and will receive the reimbursement. As a company that carries out extensive research and development activities, Adaptimmune Limited is able to surrender the trading losses that arise from its qualifying research and development activities for a payable tax credit. Reimbursable R&D tax and expenditure credits were $30,226,000, $34,082,000 and $19,442,000 in the years ended December 31, 2022, 2021 and 2020, respectively. (q) Share-based compensation The Company awards certain employees options over the ordinary shares of the parent company. The cost of share-based awards issued to employees are measured at the grant-date fair value of the award and recognized as an expense over the requisite service period. The fair value of the options is determined using the Black-Scholes option-pricing model. Share options with graded-vesting schedules are recognized on a straight-line basis over the requisite service period for each separately vesting portion of the award. The Company has elected to account for forfeitures of stock options when they occur by reversing compensation cost previously recognized, in the period the award is forfeited, for an award that is forfeited before completion of the requisite service period. (r) Retirement benefits The Company operates defined contribution pension schemes for its directors and employees. The contributions to this scheme are expensed to the Consolidated Statement of Operations as they fall due. The pension contributions for the years ended December 31, 2022, 2021, and 2020 were (s) Interest income Interest income arises on cash, cash equivalents and available-for-sale debt securities and is net of amortization (accretion) of the premium (discount) on purchase of the debt securities of $2,525,000, $5,276,000, and $3,836,000 in the years ended December 31, 2022, 2021 and 2020, respectively. ​ (t) Income taxes Income taxes for the period comprise current and deferred tax. Income tax is recognized in the Consolidated Statement of Operations except to the extent that it relates to items occurring during the year recognized either in other comprehensive income or directly in equity, in which case it is recognized in other comprehensive income or equity. Current tax is the expected tax payable or receivable on the taxable income or loss for the current or prior periods using tax rates enacted at the balance sheet date. Deferred tax is accounted for using the asset and liability method that requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement carrying amount and the tax bases of assets and liabilities at the applicable tax rates and for operating loss and tax credit carryforwards. A valuation allowance is provided to reduce deferred tax assets to the amount that is more likely than not to be realized. The Company evaluates the realizability of its deferred tax assets and adjusts the amount of the valuation allowance, if necessary. The factors used to assess the likelihood of realization include the Company’s forecast of income, carryback availability, reversing taxable temporary differences and available tax-planning strategies that could be implemented to realize the deferred tax assets. Income tax positions must meet a more-likely-than-not recognition threshold to be recognized. Income tax positions that previously failed to meet the more-likely-than-not threshold are recognized in the first subsequent financial reporting period in which that threshold is met. Previously recognized tax positions that no longer meet the more-likely-than-not threshold are derecognized in the first subsequent financial reporting period in which that threshold is no longer met. Recognized income tax positions are measured at the largest amount that is greater than 50 percent likely of being realized. We recognize potential accrued interest and penalties related to an underpayment of income taxes within the Consolidated Statement of Operations as income tax expense. (u) Loss per share Basic loss per share is determined by dividing net loss attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. Diluted loss per share is determined by dividing net loss attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period, adjusted for the dilutive effect of all potential ordinary shares that were outstanding during the period. Potentially dilutive shares are excluded when the effect would be to increase diluted earnings per share or reduce diluted loss per share. The following table reconciles the numerator and denominator in the basic and diluted loss per share computation (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Numerator for basic and diluted loss per share ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (165,456) ​ $ (158,090) ​ $ (130,092) Net loss attributable to shareholders used for basic and diluted EPS calculation ​ $ (165,456) ​ $ (158,090) ​ $ (130,092) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for basic and diluted loss per share ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of shares used to calculate basic and diluted loss per share ​ ​ 967,242,403 ​ ​ 934,833,017 ​ ​ 854,783,763 ​ The effects of the following potentially dilutive equity instruments have been excluded from the diluted loss per share calculation because they would have an antidilutive effect on the loss per share for the period

Revenue

Revenue	12 Months Ended
	Dec. 31, 2022
Revenue
Revenue	Note 3 — Revenue Revenue comprises the following categories (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ ​ 2022 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Development revenue ​ $ 27,148 $ 6,149 $ 3,958 ​ ​ $ 27,148 $ 6,149 $ 3,958 ​ ​ Deferred revenue decreased by $15,010,000 from $199,422,000 at December 31, 2021 to $184,412,000 at December 31, 2022 primarily due to a $20,601,000 decrease caused by the change in the exchange rate between pounds sterling and the U.S. dollar from £1.00 to $1.35 at December 31, 2021 to £1.00 to $1.21 at December 31, 2022 and due to $17,648,000 of revenue recognized during the period. This was offset by a $20,000,000 additional payment received under the Genentech Collaboration and License Agreement in December 2022. ​ Deferred revenue increased by $147,330,000 from $52,092,000 at January 1, 2021 to $199,422,000 at December 31, 2021 due to a $4,200,000 milestone payment received under the GSK Collaboration and License Agreement in June 2021 and the upfront payment of $150,000,000 received under the Genentech Collaboration and License Agreement in October 2021. This was offset by $1,498,000 of revenue recognized during the period. ​ The aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements as of December 31, 2022, was $340,713,000. The Genentech Collaboration and License Agreement On September 3, 2021, the Company entered into a Strategic Collaboration and License Agreement with Genentech, Inc. and F. Hoffman-La Roche Ltd, which became effective on October 19, 2021 upon expiry or termination of all applicable waiting periods under the Hart-Scott-Rodino Antitrust Improvements Act of 1976. ​ Under the Agreement, Genentech and Adaptimmune (each, a “party” and together, the “parties”) will collaborate to develop two types of allogeneic T-cell therapies: (i) “off-the-shelf” αβ T-cell therapies directed to initial collaboration targets, with Genentech having the right to designate additional collaboration targets, up to five collaboration targets in total, and (ii) personalized therapies utilizing αβ T-cell receptors (TCRs) isolated from a patient, with such therapies being administered to the same patient. ​ The parties will collaborate to perform a research program, initially during an eight year period (which may be extended for up to two additional two year terms at Genentech’s election upon payment of an extension fee for each two-year term), to develop the cell therapies, following which Genentech will determine whether to further develop and commercialize such therapies. Under the Agreement, Adaptimmune exclusively licenses Genentech certain intellectual property rights it controls to enable Genentech to research, develop, manufacture and commercialize (i) “off-the-shelf” T-cell therapies directed to the collaboration targets and (ii) personalized T-cell therapies developed within the scope of the Agreement, and Genentech is solely responsible for the clinical development and commercialization of any cell therapies arising from the collaboration. Adaptimmune will manufacture and supply cell therapies for Phase 1 trials of “off-the-shelf” T-cell therapies unless Genentech decides to assume responsibility for such manufacturing. ​ Under the Agreement, Adaptimmune is also subject to certain restrictions on its ability to further develop and commercialize certain cell therapies. In particular restrictions apply in relation to its ability to develop cell therapy products to nominated targets and to develop competing personalized cell therapies. This restriction does not prevent Adaptimmune from developing cell therapies to other targets or cell therapies containing different types of receptors. ​ Under the terms of the Agreement, Adaptimmune will receive $150 million as an upfront payment, which was received in the fourth quarter of 2021. Adaptimmune may also receive: ​ ● $150 million in additional payments spread over a period of 5 years from the effective date of the Agreement, unless the agreement is earlier terminated, of which $20 million was received in the fourth quarter of 2022; ● Research milestones of up to $50 million; ● Development milestones of up to $100 million in relation to the development of “off-the-shelf” T-cell therapies per collaboration target (unless Adaptimmune exercises its right to opt-in to receive a profit share) and up to $200 million in relation to the development of personalized T-cell therapies; ● Commercialization milestones of up to $1.1 billion for “off-the-shelf” T-cell therapies (unless Adaptimmune exercises its right to opt-in to receive a profit share and assuming “off-the-shelf” T-cell therapies are developed to 5 targets) and for personalized T-cell therapies; and ● Net sales milestones of up to $1.5 billion for “off-the-shelf” T-cell therapies (unless Adaptimmune exercises its right to opt-in to receive a profit share and assuming “off-the-shelf” T-cell therapies are developed to 5 targets) and for personalized T-cell therapies. ​ In addition, Adaptimmune will receive tiered royalties on net sales in the mid-single to low-double digits. Collaboration target designation fees apply if Genentech exercises its right to designate additional “off-the-shelf” collaboration targets up to a maximum of 5 targets. ​ Adaptimmune also has a right to opt-in to receive a profit share and to co-promote “off-the-shelf” T-cell therapies. If Adaptimmune elects to opt in, then Adaptimmune will be eligible to share 50 percent of profits and losses from U.S. sales on such products and to receive up to $800 million in ex-U.S. regulatory and sales-based milestone payments, as well as royalties on ex-U.S. net sales. ​ The payments to the Company under the contract are typically due upon achievement of milestones, when rights are exercised by Genentech or on achievement of specific events for the additional payments, and within standard payment terms. The contract does not include a significant financing component. The parties can terminate the Agreement in the event of material breach or insolvency of the other party. Genentech is entitled to terminate the Agreement in its entirety, on a product-by-product basis or collaboration target by collaboration target basis on provision of 180 days notice. Either party may terminate the Agreement on written notice in the event that the US Federal Trade Commission or US Department of Justice seeks a preliminary injunction under applicable antitrust laws against the parties or where HSR clearance has not occurred within 180 days of the effective date of the Agreement. The Agreement became effective on October 19, 2021 upon expiry of all applicable waiting periods under the Hart-Scott-Rodino Antitrust Improvements Act of 1976. ​ The Company has assessed the agreement under the provisions of ASC 606, Revenue from Contracts with Customers and ASC 808, Collaborative Arrangements. The Company determined that Genentech is a customer and has applied the provisions of ASC 606 to the contract and related performance obligations. The Company identified the following performance obligations under the agreement: (i) research services and rights granted under the licenses for each of the initial ‘off-the-shelf’ collaboration targets, (ii) research services and rights granted under the licenses for the personalized therapies, (iii) material rights relating to the option to designate each of the additional ‘off-the-shelf’ collaboration targets and (iv) material rights relating to the options to extend the research term. The Company began recognizing revenue for the performance obligations relating to the initial ‘off-the-shelf’ collaboration targets and the personalized therapies in 2021. ​ The aggregate transaction price at inception of the agreement was $313.6 million comprising the $150 million upfront payment, $150 million of additional payments and $13.6 million of other consideration. The fees for extension of the research program, additional collaboration target designation fees, and future research, development and commercialization milestones are not considered probable as of December 31, 2022 and have not been included in the transaction price. The Company may also receive sales milestones and royalties for future sales of the therapies. These amounts have not been included within the transaction price as of December 31, 2022 because they are sales-based and would be recognized when the subsequent sales occur. ​ The aggregate transaction price is allocated to the performance obligations depending on the relative standalone selling price of the performance obligations. In determining the best estimate of the relative standalone selling price, the Company considered internal pricing objectives it used in negotiating the contract, together with internal data regarding the cost and margin of providing research services and market data from comparable arrangements. ​ The amount of the transaction price allocated to the performance obligation is recognized as or when the Company satisfies the performance obligation. The Company expects to satisfy the performance obligations relating to the initial ‘off-the-shelf’ collaboration targets and the personalized therapies as development progresses and recognizes revenue based on an estimate of the percentage of completion of the project determined based on the costs incurred on the project as a percentage of the total expected costs. The Company considers that this depicts the progress of the project, where the significant inputs would be internal project resources and third-party costs. The Company expects to satisfy the performance obligations relating to the material rights to designate additional ‘off-the-shelf’ collaboration targets from the point that the options are exercised and then as development progresses, in line with the initial ‘off-the-shelf’ collaboration targets, or at the point in time that the rights expire. The Company expects to satisfy the performance obligations relating to the material rights to extend the research term from the point that the options are exercised and then over period of the extension, or at the point in time that the rights expire. ​ The amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreement as of December 31, 2022 was $283,206,000, of which $174,125,000 is allocated to the research services and rights granted for the initial ‘off-the-shelf’ collaboration targets, $90,169,000 is allocated to the research services and rights granted for the personalized therapies, $12,766,000 is allocated to the material rights to designate the additional ‘off-the-shelf’ collaboration targets, $4,917,000 is allocated to the material right for the first option to extend the research term and $1,229,000 is allocated to the material right for the option to extend the research term a second time. ​ The Astellas Collaboration Agreement ​ Upon successful completion of the Phase 1 trial for a product, Astellas and Adaptimmune will elect whether to progress with co-development and co-commercialization of such product, or to allow the other party to pursue the candidate independently. If the parties progress with co-development and co-commercialization of a product, then each party will grant the other party a co-exclusive license to co-develop and co-commercialize such product in the field of T-cell therapy. If a product is developed solely by one party, then the other party will grant to the continuing party an exclusive license to develop and commercialize such product in the field of T-cell therapy. ​ In June 2020, the parties nominated the target for the first collaboration program and the Company commenced development of this target under the agreement and began recognizing revenue for this performance obligation. In July 2021, the parties nominated the target for the second collaboration program and the Company commenced development of this target under the agreement and began recognizing revenue for this performance obligation. ​ In addition, Astellas was also granted the right to develop, independently of Adaptimmune, allogeneic T-cell therapy candidates directed to two targets selected by Astellas. Astellas will have sole rights to develop and commercialize products resulting from these two targets. ​ Under the terms of the agreement, Adaptimmune could be entitled to receive up to $847,500,000 in further payments, including: ​ ● development milestones of up to $73,750,000 for each co-developed and co-commercialized product; and ● development milestones of up to $147,500,000 per product and up to $110,000,000 in sales milestones for products developed unilaterally by Astellas. ​ In addition, Adaptimmune is entitled to receive research funding of up to $7,500,000 per year on a per collaboration target basis, which is payable on a quarterly basis within standard payment terms (typically 30 days), and tiered royalties on net sales in the mid-single to mid-teen digits. To the extent that Astellas and Adaptimmune co-develop and co-commercialize any product, the parties would share equally all worldwide costs and profits. Either party can terminate the agreement in the event of material breach or insolvency of the other party. Astellas can terminate the Agreement for convenience in its entirety or partly in relation to any targets and products directed to such targets. Adaptimmune can terminate the Agreement for convenience in relation to any target it is unilaterally developing and to products directed to such target. The payments to the Company under the contract are typically billed as the development services are performed or are due on achievement of milestones and within standard payment terms (typically 30 days for development services and 20 days for milestone achievement). Management has determined that the contract does not include a significant financing component because (i) the timing of initiation of the programs, the right to obtain the services and the right to terminate the contract resides with Astellas and (ii) a substantial amount of the consideration promised by the customer is variable, and the amount or timing of that consideration varies on the basis of the occurrence or nonoccurrence of a future event that is not substantially within the control of the customer or the Company. The Company has assessed the agreement under the provisions of ASC 606, Revenue from Contracts with Customers Collaborative Arrangements The aggregate transaction price at inception of the agreement was the $50,000,000 upfront payment. Future development milestones are not considered probable as of December 31, 2022 and have not been included in the transaction price. Reimbursement of the research funding over the co-development period (up until completion of a Phase 1 trial for products directed to such target) is variable consideration and included in the transaction price as of December 31, 2022 to the extent that a significant reversal of revenue is not probable. The Company may also receive sales milestones upon the achievement of specified levels of annual net sales by Astellas under an independent Astellas program. These amounts have not been included within the transaction price as of December 31, 2022 because they are sales-based and would be recognized when the subsequent sales occur. The aggregate transaction price is allocated to the performance obligations depending on the relative standalone selling price of the performance obligations. In determining the best estimate of the relative standalone selling price, the Company considered internal pricing objectives it used in negotiating the contract, together with internal data regarding the cost and margin of providing research services and adjusted-market data from comparable arrangements. The variable consideration is allocated to the performance obligation to which it relates. The amount of the transaction price allocated to the performance obligation is recognized as or when the Company satisfies the performance obligation. The Company expects to satisfy the performance obligations relating to the three co-development targets as development progresses and recognizes revenue based on an estimate of the percentage of completion of the project determined based on the costs incurred on the project as a percentage of the total expected costs. The Company considers that this depicts the progress of the project, where the significant inputs would be internal project resources and third-party costs. The revenue allocated to the research services will be recognized as development of products directed to the target progresses up until completion of a Phase 1 trial. The Company has determined that the performance obligations relating to the two independent Astellas targets would be recognized at a point-in-time, upon commencement of the licenses in the event of nomination of the target, since they are right-to-use licenses. The amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreement as of December 31, 2022 was $57,509,000, of which $13,474,000 is allocated to the rights granted for each of the two independent Astellas targets, $10,071,000 is allocated to research services and rights granted under the co-exclusive license for the first co-development target, $13,985,000 is allocated to research services and rights granted under the co-exclusive license for the second co-development target and $6,505,000 is allocated to research services and rights under the co-exclusive license for the third The parties mutually agreed to terminate the agreement as of March 6, 2023, see Note 16 for further information. As the termination was only triggered and effective after December 31, 2022, there was no impact on revenue recognized in relation to the agreement in the year ended December 31, 2022. ​ The GSK Collaboration and License Agreement ​ The GSK Collaboration and License Agreement consisted of multiple performance obligations, including the transition of the NY-ESO SPEAR T-cell program to GSK, the development of a second and third target, and an exclusive license (the “NY-ESO License”) to research, develop, and commercialize the Company’s NY-ESO SPEAR T-cell therapy program. In 2017, GSK exercised its option to obtain the NY-ESO License and in July 2018, the IND for the NY-ESO SPEAR T-cell program transferred to GSK. In 2017, GSK nominated a second target program which was completed in 2018. ​ In 2019, GSK nominated its third target under the Collaboration and License Agreement and the Company received $3,200,000 following the nomination of the target. The development of products to the third target is a separate performance obligation. Revenue allocated to this performance obligation is recognized as the development progresses. ​ Under the terms of the GSK Collaboration and License Agreement, the Company was also entitled to development milestones. The development and regulatory milestones were per product milestones and were dependent on achievement of certain obligations, the nature of the product being developed, stage of development of product, territory in which an obligation was achieved and type of indication or indications in relation to which the product was being developed. In June 2021 the Company received a $4,200,000 milestone payment following achievement of a development milestone for the third target under the GSK Collaboration and License Agreement. The Company would have also received commercialization milestones upon the first commercial sale of a product based on the indication and the territory and mid-single to low double-digit royalties on worldwide net sales. No revenue relating to royalties was recognized relating to the GSK Collaboration and License Agreement because they were sales or usage-based royalties promised in exchange for a license of intellectual property, which were to be recognized when the subsequent sale or usage occurs, and no such sales or usage occurred prior to termination. The payments to the Company under the contract are typically due upon achievement of milestones and within standard payment terms (approximating to 45 days). The contract does not include a significant financing component. The amount of the transaction price allocated to the performance obligation was recognized as or when the Company satisfied the performance obligation. The Company satisfied the performance obligations relating to the development of each target over time and recognized revenue based on an estimate of the percentage of completion of the project determined based on the costs incurred on the project as a percentage of the total expected costs. The Company considers that this depicted the progress of the project, where the significant inputs are internal project resource and third-party clinical and manufacturing costs. The collaboration was terminated by GSK in October 2022 and we are in discussions with GSK in relation to the transition of the NY-ESO and PRAME programs under the collaboration agreement to Adaptimmune. A further amendment to the collaboration agreement was entered into on December 19, 2022 for the deletion of certain provisions relating to GSK’s post termination manufacturing and supply obligations and payment of £5,000,000 by GSK to Adaptimmune. The amendment also meant that no further milestone payments or royalties were due from GSK to the Company. The Company accounted for the termination of the agreement and December 19, 2022 amendment agreement as a single combined contract modification. No performance obligations were identified as a result of the modification as there were no further goods or services to be provided by the Company and the modification resulted in the remaining partially satisfied performance obligation under the collaboration relating to the third target becoming fully satisfied. As discussions were still ongoing, and no formal agreement had been reached, as of December 31, 2022 regarding the potential transfer of the NY-ESO cell therapy program to Adaptimmune this was not accounted for in the year ended December 31, 2022. GSK continues to be responsible for the execution and costs of ongoing clinical trials. This matter will be assessed in future periods if and when an agreement is reached. The aggregate transaction price of the contract modification was $6,500,000 comprised of the £5,000,000 ($6,100,000) payment and the remaining deferred income under the collaboration that had not been recognized as revenue as of the date of the modification of $400,000. No non-cash consideration was identified and as the contract modification removed the Company’s entitlement to future milestone payments and royalties, no variable consideration was identified. The contract modification was accounted for on a cumulative catch-up basis. As all performance obligations were considered fully satisfied as a result of the modification and no additional performance obligations were identified, the transaction price of the modification was recognized as revenue in full in the year ended December 31, 2022 and there is n The previous performance obligation relating to the NY-ESO License was recognized at a point-in-time, upon commencement of the license in 2018.

Financial instruments

Financial instruments	12 Months Ended
	Dec. 31, 2022
Financial instruments
Financial instruments	Note 4 — Financial instruments The Company’s financial instruments consist primarily of cash and cash equivalents, marketable securities, restricted cash, accounts receivable, accounts payable and accrued expenses. Assets and liabilities measured at fair value on a recurring basis based on Level 1, Level 2, and Level 3 fair value measurement criteria as of December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements using ​ ​ December 31, ​ Level 1 ​ Level 2 ​ Level 3 ​ 2022 ​ ​ ​ ​ ​ ​ Assets classified as cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 2,984 ​ $ 2,984 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets classified as available-for-sale debt securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 85,764 ​ $ 85,764 ​ $ — ​ $ — U.S. Treasury securities ​ ​ 5,954 ​ ​ — ​ ​ 5,954 ​ ​ — Agency bonds ​ 4,854 ​ ​ — ​ ​ 4,854 ​ ​ — ​ $ 96,572 ​ $ 85,764 $ 10,808 $ — ​ Assets and liabilities measured at fair value on a recurring basis based on Level 1, Level 2, and Level 3 fair value measurement criteria as of December 31, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ December 31, ​ Level 1 ​ Level 2 ​ Level 3 ​ ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets classified as available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 214,639 ​ $ 214,639 ​ $ — ​ $ — Agency bonds ​ ​ 4,993 ​ ​ — ​ ​ 4,993 ​ ​ — ​ ​ $ 219,632 ​ ​ 214,639 ​ ​ 4,993 ​ ​ — ​ The Company estimates the fair value of available-for-sale debt securities and corporate debt securities classified as cash equivalents with the aid of a third-party valuation service, which uses actual trade and indicative prices sourced from third-party providers on a daily basis to estimate the fair value. If observed market prices are not available (for example, securities with short maturities and infrequent secondary market trades), the securities are priced using a valuation model maximizing observable inputs, including market interest rates. Significant concentration of credit risk The Company held cash and cash equivalents of $108,033,000, marketable securities of $96,572,000 and restricted cash of $1,569,000 as of December 31, 2022. The cash and cash equivalents and restricted cash are held with multiple banks and the Company monitors the credit rating of those banks. The Company maintains cash balances in excess of amounts insured by the Federal Deposit Insurance Corporation in the United States and the U.K. Government Financial Services Compensation Scheme in the United Kingdom. The Company had three customers during the year-ended December 31, 2022, which are Genentech, Astellas and GSK. There were accounts receivable of $7,435,000 as of December 31, 2022, and $752,000 as of December 31, 2021. The Company has been transacting with Genentech since October 2021, Astellas since 2020 and GSK since 2014, during which time no impairment losses have been recognized. As of December 31, 2022, there were no overdue accounts receivable and no receivables, either accrued or billed, due from GSK that are no longer recoverable following the termination of the GSK Collaboration and License Agreement (see Note 3). Although there is economic uncertainty in various global markets, including the U.S. and Europe, the Company has determined that this has not significantly increased the recoverability risk relating to its receivables balances as of December 31, 2022. Foreign exchange risk The Company is exposed to foreign exchange rate risk because it operates in the United Kingdom and the United States. Expenses are generally denominated in the currency in which the Company’s operations are located, which are the United Kingdom and the United States. However, the U.K.-based subsidiary incurs significant research and development costs in U.S. dollars and, to a lesser extent, Euros. The results of operations and cash flows will be subject to fluctuations due to changes in foreign currency exchange rates, which could harm the Company’s business in the future. Management seeks to minimize this exposure by maintaining currency cash balances at levels appropriate to meet foreseeable expenses in U.S. dollars and pounds sterling. To date, the Company has not used forward exchange contracts or other currency hedging products to manage exchange rate exposure, although it may do so in the future. The exchange rate as of December 31, 2022, the last business day of the reporting period, was £1.00 to $1.21. Interest rate risk Surplus cash and cash equivalents are invested in interest-bearing savings, money market funds, corporate debt securities and commercial paper from time to time. Investments in corporate debt securities are subject to fixed interest rates. The Company’s exposure to interest rate sensitivity is impacted by changes in the underlying U.K. and U.S. bank interest rates and the fair market value of its corporate debt securities will fall in value if market interest rates increase. Management believes that an immediate one percentage point change in interest rates would not have a material effect on the fair market value of our portfolio, and therefore does not expect the operating results or cash flows to be significantly affected by changes in market interest rates.

Other current assets

Other current assets	12 Months Ended
	Dec. 31, 2022
Other current assets
Other current assets	Note 5 — Other current assets Other current assets consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Research and development credits receivable $ 30,162 $ 30,773 Prepayments ​ 9,472 ​ 9,043 Clinical materials ​ 1,279 ​ 746 VAT receivable ​ ​ 490 ​ ​ 2,482 Other current assets ​ 1,927 ​ 2,082 ​ ​ $ 43,330 ​ $ 45,126 ​

Property, plant and equipment,

Property, plant and equipment, net	12 Months Ended
	Dec. 31, 2022
Property, plant and equipment, net
Property, plant and equipment, net	Note 6 — Property, plant and equipment, net Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Computer equipment ​ $ 3,818 ​ $ 3,692 Laboratory equipment ​ ​ 30,173 ​ ​ 28,002 Office equipment ​ ​ 925 ​ ​ 953 Leasehold improvements ​ ​ 28,459 ​ ​ 28,704 Assets under construction ​ ​ 28,729 ​ ​ 5,396 ​ ​ ​ 92,104 ​ ​ 66,747 Less accumulated depreciation ​ ​ (38,588) ​ ​ (36,253) ​ ​ $ 53,516 ​ $ 30,494 ​ Depreciation expense was $5,266,000, $5,630,000 and $6,627,000 for the years ended December 31, 2022, 2021 and 2020, respectively.

Intangible assets, net

Intangible assets, net	12 Months Ended
	Dec. 31, 2022
Intangible assets, net
Intangible assets, net	Note 7 — Intangible assets, net Intangible assets, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Acquired software licenses ​ $ 4,930 ​ $ 4,842 Licensed IP rights – completed technology used in R&D ​ ​ 188 ​ ​ 209 ​ ​ ​ 5,118 ​ ​ 5,051 Less accumulated amortization ​ ​ (4,676) ​ ​ (4,051) ​ ​ $ 442 ​ $ 1,000 ​ Amortization expense was $809,000, $937,000, and $967,000 for the years ended December 31, 2022, 2021 and 2020 respectively. The estimated aggregate amortization expense expected to be recorded in respect of these assets for each of the five years ended 2027 is $309,000, $105,000, $43,000, $1,000 and $1,000, respectively.

Operating Leases

Operating Leases	12 Months Ended
	Dec. 31, 2022
Operating leases
Operating leases	​ Note 8 — Operating leases The following table shows the lease costs for the years ended December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ ​ December 31, ​ ​ 2022 2021 Lease cost: ​ ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 4,367 $ 4,259 Short-term lease cost ​ ​ 389 ​ 419 ​ ​ $ 4,756 $ 4,678 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ ​ December 31, ​ ​ ​ 2022 2021 Other information: ​ ​ ​ ​ ​ ​ ​ Operating cash outflows from operating leases (in thousands) ​ ​ $ 3,746 $ 4,101 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term - operating leases ​ ​ 6.9 years ​ 7.8 years Weighted-average discount rate - operating leases ​ ​ 6.8% ​ 6.8% ​ The maturities of operating lease liabilities as of December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ Operating leases ​ ​ ​ 2023 $ 4,170 2024 ​ 3,953 2025 ​ 4,001 2026 ​ 4,055 2027 ​ 5,471 after 2027 ​ 7,324 Total lease payments ​ ​ 28,974 Less: Imputed interest ​ ​ (5,897) Present value of lease liability ​ $ 23,077 ​ The Company has operating leases in relation to property for office, manufacturing and research facilities. The maximum lease term without activation of termination options is to 2041. On March 30, 2022, the Company entered into an agreement to modify the lease of 39 Innovation Drive, Milton Park, Abingdon, Oxfordshire, UK, and on June 15, 2022, the deeds associated with the modification were signed. However, for purposes of ASC 842 Leases, Upon modification, the lease liability has been remeasured using the current estimate of the Company’s incremental borrowing rate. The remeasurement of the lease liability also resulted in variable lease payments not previously included in the amount of the lease liability becoming included in the amount of the lease payments as at the date of the modification. The amount of the remeasurement of the lease liability due to the inclusion of variable lease payments that depend on an index or rate has been recognized as an adjustment to the corresponding right-of-use asset. The effect of the modification was to increase the lease liability and the corresponding right-of-use asset by $75,000.

Accrued expenses and other curr

Accrued expenses and other current liabilities	12 Months Ended
	Dec. 31, 2022
Accrued expenses and other current liabilities
Accrued expenses and other current liabilities	Note 9 — Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Accrued clinical and development expenditure ​ $ 16,749 ​ $ 13,436 Accrued employee expenses ​ ​ 8,232 ​ ​ 11,758 Other accrued expenditure ​ ​ 4,079 ​ ​ 4,388 Other ​ 2,155 ​ 327 ​ ​ $ 31,215 ​ $ 29,909 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Contingencies and commitments

Contingencies and commitments	12 Months Ended
	Dec. 31, 2022
Contingencies and commitments
Contingencies and commitments	Note 10 — Contingencies and commitments Leases Lease payments under operating leases as of December 31, 2022 and information about the Company’s lease arrangements are disclosed in Note 8. Capital commitments As of December 31, 2022, the Company had commitments for capital expenditure totaling $2,459,000 primarily relating to construction and related expenditure for its properties in the United Kingdom and United States, of which the Company expects to incur $2,261,000 within one year and $198,000 within one to three years. Commitments for clinical materials, clinical trials and contract manufacturing As of December 31, 2022, the Company had non-cancellable commitments for purchase of clinical materials, contract manufacturing, maintenance, and committed funding under the MD Anderson strategic alliance of up to $10,928,000, which the Company expects to incur $10,662,000 within one year, $133,000 within one to three years and $133,000 within three to five years. The amount and timing of these payments vary depending on the rate of progress of development. Future clinical trial expenses have not been included within the purchase commitments because they are contingent on enrollment in clinical trials and the activities required to be performed by the clinical sites. The Company’s subcontracted costs for clinical trials and contract manufacturing were $54,689,000, $46,469,000 and $33,744,000 for the years ended December 31, 2022, 2021, and 2020 respectively. MD Anderson Strategic Alliance On September 26, 2016, the Company announced that it had entered into a multi-year strategic alliance with The University of Texas MD Anderson Cancer Center (“MD Anderson”) designed to expedite the development of T-cell therapies for multiple types of cancer. The Company and MD Anderson are collaborating on a number of studies including clinical and preclinical development of the Company’s SPEAR T-cell therapies and will collaborate on future clinical stage first and second generation SPEAR T-cell therapies across a number of cancers. Under the terms of the agreement, the Company committed at least $19,644,000 to fund studies. Payment of this funding is contingent on mutual agreement to study orders in order for any study to be included under the alliance and the performance of set milestones by MD Anderson. The Company made an upfront payment of $3,412,000 to MD Anderson in the year ended December 31, 2017 and milestone payments of $2,326,000, $3,549,000 and $454,000 in the years ended December 31, 2018, 2020, and 2021, respectively. A further milestone of $2,326,000 was met and paid in the year ended December 31, 2022. The Company is obligated to make further payments to MD Anderson as certain milestones are achieved. These costs are expensed to research and development as MD Anderson renders the services under the strategic alliance. The agreement may be terminated by either party for material breach by the other party. Individual studies may be terminated for, amongst other things, material breach, health and safety concerns or where the institutional review board, the review board at the clinical site with oversight of the clinical study, requests termination of any study. Where any legal or regulatory authorization is finally withdrawn or terminated, the relevant study will also terminate automatically. Universal Cells Research, Collaboration and License Agreement and Co-development and Co-commercialization agreement On November 25, 2015, the Company entered into a Research, Collaboration and License Agreement relating to gene editing and Human Leukocyte Antigen (“HLA”) engineering technology with Universal Cells, Inc. (“Universal Cells”). The Company paid an upfront license and start-up fee of $2,500,000 to Universal Cells in November 2015, a milestone payment of $3,000,000 in February 2016 and further milestone payments of $200,000 and $900,000 were made in the year ended December 31, 2018 and 2017, respectively. ​ The agreement was amended and re-stated as of January 13, 2020, primarily to reflect changes to the development plan agreed between the parties. The agreement was further amended as of July 22, 2022, primarily to make certain changes to development milestones and to agree on the status thereof, as agreed between the parties. Following the amendment, milestone payments of $500,000, $600,000 and $400,000 were made in the year ended December 31, 2022. A further milestone of $1,800,000 has been accrued in accordance with the milestone schedule per the agreement but was not paid as of December 31, 2022. The upfront license and start-up fee and milestone payments were expensed to research and development when incurred. ​ This Agreement was terminated by notice on January 27, 2023, effective 30 days following receipt of notice of termination. As a result of termination, all licenses between the parties to the Agreement will cease and each party is required to return all confidential information of the other party. ​ Astellas Collaboration Agreement ​ Under the Astellas Collaboration Agreement, described further in Note 3, the Company could in certain circumstances elect to unilaterally develop a product using technology contributed by Astellas. If Adaptimmune unilaterally develops a product with technology contributed by Astellas, Astellas could be eligible to receive up to $552,500,000, including up to $147,500,000 in milestone payments per product, and up to $110,000,000 in sales milestones for products developed unilaterally by Adaptimmune. In addition, Astellas is entitled to receive tiered royalties on net sales in the mid-single to mid-teen digits. ​ Noile-Immune Collaboration Agreement On August 26, 2019, the Company entered into a collaboration and license agreement relating to the development of next-generation SPEAR T-cell products with Noile-Immune. An upfront exclusive license option fee of $2,500,000 was paid to Noile-Immune in 2019. This was recognized within Research and Development in the Consolidated Statement of Operations for the year ended December 31, 2019. Under the agreement, development and commercialization milestone payments up to a maximum of $312,000,000 may be payable if all possible targets are selected and milestones achieved. Noile-Immune would also receive mid-single-digit royalties on net sales of resulting products. Alpine Collaboration Agreement On May 14, 2019, the Company entered into a Collaboration Agreement relating to the development of next-generation SPEAR T-cell products with Alpine. The Company paid an upfront exclusive license option fee of $2,000,000 to Alpine in June 2019. Under the agreement, Adaptimmune will pay Alpine for ongoing research and development funding costs and development and commercialization milestone payments up to a maximum of $288,000,000 may be payable if all possible targets are selected and milestones achieved. The upfront payment of $2,000,000 and the payments for ongoing research was recognized within Research and development in the Consolidated Statement of Operations for the year ended December 31, 2019. A further payment of $1,000,000 was paid and recognized within Research and development in the Consolidated Statement of Operations for the year ended December 31, 2022. Alpine would also receive low single-digit royalties on worldwide net sales of applicable products. ThermoFisher License Agreement In 2012, the Company entered into a series of license and sub-license agreements with Life Technologies Corporation, part of ThermoFisher Scientific, Inc. (“ThermoFisher”) that provide the Company with a field-based license under certain intellectual property rights owned or controlled by ThermoFisher. The Company paid upfront license fees of $1,000,000 relating to the license and sublicense agreements and has an obligation to pay minimum annual royalties (in the tens of thousands of U.S. dollars prior to licensed product approval and thereafter at a level of 50% of running royalties in the previous year), milestone payments and a low single-digit running royalty payable on the net selling price of each licensed product. The upfront payment made in 2012 was expensed to research and development when incurred. Subsequent milestone payments have been recognized as an intangible asset due to the technology having alternative future use in research and development projects at the time of the payment. The minimum annual royalties have been expensed as incurred. In 2016, the Company entered into a supply agreement with ThermoFisher for the supply of the Dynabeads® CD3/CD28 technology. The Dynabeads® CD3/CD28 technology is designed to isolate, activate and expand human T-cells, and is being used in the manufacturing of the Company’s affinity enhanced T-cell therapies. The supply agreement runs until December 31, 2025. Under the supply agreement the Company is required to purchase its requirements for CD3/CD28 magnetic bead product from ThermoFisher for a period of 5 years. ThermoFisher has the right to terminate the supply agreement for material breach or insolvency.

Stockholders' equity

Stockholders' equity	12 Months Ended
	Dec. 31, 2022
Stockholders' equity
Stockholders' equity	Note 11 — Stockholders’ equity Ordinary shares Subject to any other provisions of our articles of association and without prejudice to any special rights, privileges or restrictions as to voting attached to any shares forming part of our share capital, the voting rights of shareholders are as follows. On a show of hands, each shareholder present in person, and each duly authorized representative present in person of a shareholder that is a corporation, has one vote. On a show of hands, each proxy present in person who has been duly appointed by one or more shareholders entitled to vote on a resolution has one vote, but a proxy has one vote for and one vote against a resolution if, in certain circumstances, the proxy is instructed by more than one shareholder to vote in different ways on a resolution. On a poll, each shareholder present in person or by proxy or (being a corporation) by a duly authorized representative has one vote for each share held by the shareholder. We are prohibited (to the extent specified by the Companies Act 2006) from exercising any rights to attend or vote at meetings in respect of any shares held by the Company as treasury shares. ​ Subject to the Companies Act 2006 and the provisions of all other relevant legislation, we may by ordinary resolution declare dividends out of our profits available for distribution in accordance with the respective rights of shareholders but no such dividend shall exceed the amount recommended by the directors. If, in the opinion of the directors, our profits available for distribution justify such payments, the directors may from time to time pay interim dividends to the holders of any class of shares. Subject to any special rights attaching to or terms of issue of any shares, all dividends shall be declared and paid according to the amounts paid up on the shares on which the dividend is paid. No dividend shall be payable to us in respect of any shares held by us as treasury shares (except to the extent permitted by the Companies Act 2006 and any other relevant legislation). As of December 31, 2022, Adaptimmune Therapeutics Plc and Adaptimmune Limited have accumulated net losses and, accordingly, no profits available for distribution out of which to declare or pay dividends. Subject to any special rights attaching to or the terms of issue of any shares, on any winding-up of the Company our surplus assets remaining after satisfaction of our liabilities will be distributed among our shareholders in proportion to their respective holdings of shares and the amounts paid up on those shares. Effective from May 25, 2022, the Directors were generally authorized to allot new shares or to grant rights to subscribe for or to convert any security into shares in the Company up to a maximum aggregate nominal amount of £310,638.00 . 2020 January Offering On January 24, 2020, the Company closed an underwritten public offering of 21,000,000 American Depository Shares (ADSs), which together with the full exercise by the underwriters on February 7, 2020 of their option to purchase an additional 3,150,000 ADSs, generated net proceeds of $90,554,000. 2020 June Offering On June 4, 2020, the Company closed an underwritten public offering of 20,500,000 ADSs, which together with the full exercise by the underwriters of their option to purchase an additional 3,075,000 ADSs, generated net proceeds of $243,834,000. At-the-Market Offerings On August 10, 2020 the Company entered into a sales agreement with Cowen and Company, LLC (“Cowen”) (the “Sales Agreement”) under which we may from time to time issue and sell American Depositary Shares (“ADSs”) representing our ordinary shares through Cowen in at-the-market (“ATM”) offerings for an aggregate offering price of up to $200 million. In the year ended December 31, 2021, the Company sold 511,555 ADSs representing 3,069,330 ordinary shares resulting in net proceeds to the Company of $2,529,000 after deducting commissions payable under the Sales Agreement and issuance costs. As of December 31, 2021, $197,360,000 remained available for sale under the Sales Agreement. On April 8, 2022 the Company entered into a new sales agreement with Cowen (the “2022 Sales Agreement”) under which we may from time to time issue and sell ADSs representing our ordinary shares through Cowen in ATM offerings for an aggregate offering price of up to $200 million. In the year ended December 31, 2022, the Company sold 7,289,737 ADSs under the agreement representing 43,738,422 ordinary shares resulting in net proceeds to the Company of $12,793,448.13 after deducting commissions payable under the 2022 Sales Agreement and estimated issuance costs. As of December 31, 2022, approximately $186,702,871 remained available for sale under the 2022 Sales Agreement. ​

Share-based compensation

Share-based compensation	12 Months Ended
	Dec. 31, 2022
Share-based compensation
Share-based compensation	Note 12 — Share-based compensation The Company grants options over ordinary shares in Adaptimmune Therapeutics plc under the following option plans: (i) the Adaptimmune Therapeutics plc Employee Share Option Scheme (adopted on January 14, 2016), (ii) the Adaptimmune Therapeutics plc 2015 Share Option Scheme (adopted on March 16, 2015) and (iii) the Adaptimmune Therapeutics plc Company Share Option Plan (adopted on March 16, 2015). The Adaptimmune Therapeutics plc Company Share Option Plan is a tax efficient option scheme intended to comply with the requirements of Schedule 4 to the Income Tax (Earnings and Pensions) Act 2003 of the United Kingdom, which provides for the grant of company share option plan (“CSOP”) options. Grants may not exceed the maximum value of £30,000 per participant for the shares under the option, which is a CSOP compliance requirement. Generally, the vesting dates for the options granted under these plans up to December 31, 2022 are 25% on the first anniversary of the grant date and 75% in monthly installments over the following three years . However, the options granted to non-executive directors under the Adaptimmune Therapeutics plc 2015 Share Option Scheme vest and become exercisable as follows: ​ ​ ​ ​ ​ ​ Options granted to non-executive directors on May 11, 2015: Immediately on grant date Options granted to a non-executive director on June 23, 2016: ​ 25% on the first Options granted to non-executive directors on August 11, 2016: ​ 100% on the first Options granted to non-executive directors on November 28, 2016: ​ 25% on the first Options granted to non-executive directors on July 3, 2017 ​ 100% on the first Options granted to non-executive directors on June 22, 2018: ​ 100% on the first Options granted to a non-executive director on July 5, 2018: ​ 25% on the first Options granted to non-executive directors on July 2, 2019: ​ 100% on the first Options granted to non-executive directors on July 1, 2020: ​ 100% on the first Options granted to non-executive directors on July 1, 2021: ​ 100% on the first Options granted to non-executive directors on July 1, 2022: ​ 100% on the first ​ Effective from January 2018, the Company has also granted restricted stock unit style options (“RSU-style”). The RSU-style options over ordinary shares in Adaptimmune Therapeutics plc are granted under the Adaptimmune Therapeutics plc Employee Share Option Scheme (adopted on January 14, 2016). These options have an exercise price equal to the nominal value of an ordinary share, of £0.001 , and generally vest over four years , with 25% on the first, and each subsequent, anniversary of the grant date. Options granted under these plans are not subject to performance conditions. The contractual term of options granted under these plans is ten years . The maximum aggregate number of options which may be granted under these plans and any incentive plans adopted by the Company cannot exceed a scheme limit that equates to 8% of the initial fully diluted share capital of the Company immediately following its IPO plus an automatic annual increase of an amount equivalent to 4% of the issued share capital on each 30 June (or such lower number as the Board, or an appropriate committee of the Board, may determine). The automatic increase is effective from July 1, 2016. Prior to December 31, 2014, the Company granted options to purchase ordinary shares in Adaptimmune Limited under three option schemes: (i) The Adaptimmune Limited Share Option Scheme was adopted on May 30, 2008. Under this scheme Enterprise Management Incentive (“EMI”) options (which are potentially tax-advantaged in the United Kingdom) have been granted (subject to the relevant conditions being met) to its employees who are eligible to receive EMI options under applicable U.K. tax law and unapproved options (which do not attract tax advantages) have been granted to its employees who are not eligible to receive EMI options, and to its Directors and consultants. In May 2014, the Company no longer qualified for EMI status and since that date, no further EMI options were granted under this scheme; however, unapproved options have been under granted under this scheme since that date. (ii) The Adaptimmune Limited 2014 Share Option Scheme was adopted on April 11, 2014. EMI options were granted (subject to the relevant conditions being met) under this scheme to our employees who are eligible to receive EMI options under applicable U.K. tax law. Unapproved options were granted to its employees who are not eligible to receive EMI options and to directors. In May 2014, the Company no longer qualified for EMI status and since that date, no further EMI options were granted under this scheme; however, unapproved options have been under granted under this scheme since that date. (iii) The Adaptimmune Limited Company Share Option Plan was adopted on December 16, 2014. This scheme allowed the grant of options to our eligible employees prior to the Company’s corporate reorganization in 2015. This scheme is a tax efficient option scheme and options were granted on December 19, 2014 and on December 31, 2014 to our part-time and full-time employees. As part of the corporate reorganization in connection with our IPO, the holders of options granted under these schemes over ordinary shares of Adaptimmune Limited were granted equivalent options on substantially the same terms over ordinary shares of Adaptimmune Therapeutics plc (“Replacement Options”) in exchange for the release of these options. The Company does not intend to grant any further options under these schemes. As of December 31, 2022, all the Replacement Options under the Adaptimmune Limited schemes have vested. The contractual life of options granted under these schemes is ten years . The following table shows the total share-based compensation expense included in the Consolidated Statements of Operations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Research and development $ 6,264 ​ $ 9,052 ​ $ 4,417 General and administrative 11,976 ​ 11,577 ​ 5,997 ​ $ 18,240 ​ $ 20,629 ​ $ 10,414 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ December 31, ​ 2022 2021 ​ 2020 Number of options over ordinary shares granted ​ 31,826,293 ​ ​ 21,300,998 ​ ​ 15,595,374 Weighted average fair value of ordinary shares options $ 0.37 ​ $ 0.70 ​ $ 0.59 Number of additional options with a nominal exercise price granted ​ 24,248,424 ​ ​ 17,765,778 ​ ​ 8,282,152 Weighted average fair value of options with a nominal exercise price $ 0.51 ​ $ 0.97 ​ $ 0.85 ​ The following table summarizes all stock option activity for the year ended December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ ​ ​ exercise price ​ contractual ​ intrinsic value ​ ​ Options ​ per option ​ term (years) ​ (thousands) Outstanding at January 1, 2022 114,915,438 ​ £ 0.52 ​ ​ ​ ​ ​ Changes during the period: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Granted 56,074,717 ​ £ 0.21 ​ ​ ​ ​ ​ Exercised ​ (5,823,534) ​ £ 0.01 ​ ​ ​ ​ ​ Expired ​ (3,238,371) ​ £ 0.69 ​ ​ ​ ​ ​ Forfeited (9,389,161) ​ £ 0.21 ​ ​ ​ ​ ​ Outstanding at December 31, 2022 152,539,089 ​ £ 0.44 7.0 ​ £ 8,082 Exercisable at December 31, 2022 75,064,373 ​ £ 0.64 5.3 ​ £ 1,077 ​ The following table summarizes information about stock options granted based on the market value at grant date which were outstanding as of December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ ​ ​ exercise price ​ contractual ​ intrinsic value ​ Options per option term (years) (thousands) Outstanding at January 1, 2022 87,387,314 ​ £ 0.68 ​ ​ ​ ​ ​ Changes during the period: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Granted 31,826,293 ​ £ 0.37 ​ ​ ​ ​ ​ Exercised ​ (318,222) ​ £ 0.11 ​ ​ ​ ​ ​ Expired ​ (3,077,532) ​ £ 0.72 ​ ​ ​ ​ ​ Forfeited (3,340,390) ​ £ 0.59 ​ ​ ​ ​ ​ Outstanding at December 31, 2022 112,477,463 ​ £ 0.60 6.5 ​ £ 68 Exercisable at December 31, 2022 69,769,359 ​ £ 0.68 5.2 ​ £ 18 ​ The following table summarizes information about RSU-style options which were outstanding as of December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ ​ ​ ​ remaining ​ Aggregate ​ ​ ​ ​ ​ contractual ​ intrinsic value ​ Options ​ term (years) (thousands) Outstanding at January 1, 2022 27,528,124 ​ ​ 8.5 ​ ​ 12,720 Changes during the period: ​ ​ ​ ​ ​ ​ ​ ​ Granted 24,248,424 ​ ​ ​ ​ ​ ​ Exercised ​ (5,505,312) ​ ​ ​ ​ ​ ​ Expired ​ (160,839) ​ ​ ​ ​ ​ ​ Forfeited (6,048,771) ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2022 40,061,626 ​ ​ 8.4 £ 8,014 Exercisable at December 31, 2022 5,295,014 ​ ​ 6.6 £ 1,059 ​ There were 5,823,534, 5,723,646 and 11,401,390 share options exercised in the years ended December 31, 2022, 2021 and 2020 respectively. In the years ended December 31, 2022, 2021 and 2020 the total intrinsic value of stock options exercised was $2,368,000, $4,321,000 and $8,195,000, respectively and the cash received from exercise of stock options was $50,000, $759,000 and $5,663,000 respectively. The Company recognizes tax benefits arising on the exercise of stock options regardless of whether the benefit reduces current taxes. The tax benefit arising on the exercise of stock options was $488,000, $862,000 and $1,265,000 for the years ended December 31, 2022, 2021 and 2020 respectively. The Company satisfies the exercise of stock options through newly issued shares. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding ​ Exercisable ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ average ​ Weighted- ​ ​ ​ Weighted- ​ ​ ​ Total share ​ remaining ​ average ​ Total share ​ average Exercise price options contractual life exercise price options exercise price £ 0 40,061,626 ​ 8.4 £ 0.00 ​ 5,295,014 £ 0.00 ​ 0.01 - 0.25 ​ 8,412,475 ​ 9.1 ​ ​ 0.22 ​ 738,325 ​ ​ 0.19 ​ 0.26 - 0.50 38,339,879 ​ 6.9 ​ 0.41 ​ 14,287,927 ​ 0.42 ​ 0.51 - 0.75 36,255,404 ​ 5.9 ​ 0.60 ​ 32,291,011 ​ 0.61 ​ 0.76 - 1.00 24,103,880 ​ 6.1 ​ 0.84 ​ 17,446,630 ​ 0.87 ​ 1.01 - 1.50 3,974,824 ​ 6.3 ​ 1.25 ​ 3,614,465 ​ 1.26 ​ 1.51 - 2.00 1,391,001 ​ 4.7 ​ 1.70 ​ 1,391,001 ​ 1.70 Total 152,539,089 7.0 £ 0.44 75,064,373 £ 0.64 ​ The fair value of the stock options granted during the period was calculated using the Black-Scholes option-pricing model using the following assumptions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Expected term 5 years 5 years 5 years Expected volatility ​ 99-101% ​ 98-100% ​ 90-99% Risk free rate 0.94-3.90% 0.00-0.61% 0.00-0.42% Expected dividend yield ​ 0% ​ 0% ​ 0% ​ We do not have sufficient history to determine the expected life based on internal data and therefore the estimate is based on empirical data.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2022
Income taxes
Income taxes	Note 13 — Income taxes Loss before income tax expense is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 U.S. ​ $ (3,245) ​ $ 1,625 ​ $ (1,359) U.K. ​ ​ (159,714) ​ ​ (158,924) ​ ​ (128,571) Loss before income tax expense ​ $ (162,959) ​ $ (157,299) ​ $ (129,930) ​ The components of income tax expense are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 United States: ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ $ 2,492 ​ $ 791 ​ $ 162 State and local ​ ​ 5 ​ ​ — ​ ​ — U.K. ​ ​ — ​ ​ — ​ ​ — Total current tax expense ​ ​ 2,497 ​ ​ 791 ​ ​ 162 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States: ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ ​ — ​ ​ — ​ ​ — State and local ​ ​ — ​ ​ — ​ ​ — U.K. ​ ​ — ​ ​ — ​ ​ — Total deferred tax expense ​ ​ — ​ ​ — ​ ​ — Total income tax expense ​ $ 2,497 ​ $ 791 ​ $ 162 ​ As of December 31, 2022 and 2021 the tax effects of temporary differences and carryforwards that give rise to deferred tax assets and liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Deferred tax liabilities ​ ​ ​ ​ ​ ​ Property, plant and equipment: ​ $ (3,486) ​ $ (922) Operating lease right-of-use assets ​ ​ (1,529) ​ ​ (1,757) Other ​ ​ (251) ​ ​ (238) Total ​ ​ (5,266) ​ ​ (2,917) ​ ​ ​ ​ ​ ​ ​ Deferred tax assets ​ ​ ​ ​ ​ ​ Share-based compensation expense ​ ​ 16,963 ​ ​ 15,584 Intangible assets ​ ​ 1,324 ​ ​ 2,401 Operating lease liabilities ​ ​ 1,958 ​ ​ 2,143 Net operating loss and tax credit carryforwards ​ ​ 136,592 ​ ​ 114,972 Capitalized research and development expenditure ​ ​ 8,409 ​ ​ — Other ​ ​ 532 ​ ​ 260 Total ​ ​ 165,778 ​ ​ 135,360 Valuation allowance ​ ​ (160,512) ​ ​ (132,443) ​ ​ ​ 5,266 ​ ​ 2,917 Net deferred tax asset/(liability) ​ $ — ​ $ — ​ The valuation allowance is primarily related to deferred tax assets for operating loss and tax credit carry-forwards and temporary differences relating to share-based compensation expense and research and development expenditure. Deferred tax assets have been recognized without a valuation allowance to the extent supported by reversing taxable temporary differences. A valuation allowance has been provided over the remaining deferred tax assets, which management considered are not more likely than not of being realized after weighing all available positive and negative evidence including cumulative losses in recent years and projections of future taxable losses. The movements in the deferred tax asset valuation allowance for the year ended December 31, 2022 and 2021 are as follows (thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 ​ 2021 Valuation allowance at January 1, ​ $ 132,443 ​ $ 82,398 Increase in valuation allowance through net loss ​ ​ 30,455 ​ ​ 50,046 Increase in valuation allowance through other comprehensive loss ​ ​ 9,836 ​ ​ 1,512 Foreign currency translation adjustments ​ ​ (12,222) ​ ​ (1,513) Net change in the valuation allowance ​ ​ 28,069 ​ ​ 50,045 ​ ​ $ 160,512 ​ $ 132,443 ​ ​ Reconciliation of the U.K. statutory income tax rate, the income tax rate of the country of domicile of the Company, to the Company's effective income tax rate is as follows (in percentages): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ ​ 2022 2021 2020 U.K. tax rate ​ 19.0 % 19.0 % 19.0 % Tax-exempt reimbursable tax credits included within pretax Research and development expense ​ 3.6 % 4.1 % 2.8 % Surrender of R&D expenditures for R&D tax credit refund ​ (10.5) % (10.3) % (8.4) % Expenses not deductible ​ (0.3) % (0.2) % (1.4) % Change in valuation allowances ​ (18.8) % (31.8) % (17.8) % Change in tax rates ​ — % 13.7 % 4.1 % Difference in tax rates ​ 5.5 % 4.4 % — % R&D tax credits generated ​ 2.1 % 2.0 % 1.8 % Other ​ (2.1) % (1.4) % (0.1) % Effective income tax rate ​ (1.5) % (0.5) % (0.0) % ​ The Company is headquartered in the United Kingdom and has subsidiaries in the United Kingdom and the United States. The Company incurs tax losses in the United Kingdom. The U.K. corporate income tax rate for the years ended December 31, 2022, 2021 and 2020 was The United Kingdom’s Finance Act 2021, which was enacted on June 10, 2021, maintained the corporate income tax rate at 19% up until the year commencing April 1, 2023, at which point the rate will rise to 25%. The planned increase remained in place as of December 31, 2022. As of December 31, 2022, the Company used a 25% and 21% tax rate in respect of the measurement of deferred taxes existing in the U.K. and the U.S., respectively, which reflects the currently enacted tax rates and the anticipated timing of the reversing of the deferred tax balances. In respect of the measurement of deferred taxes arising in the U.K, the increase in the income tax rate adopted by the Company from 19% as of the year ended December 31, 2020 to 25% for temporary differences reversing after the year ended December 31, 2023 increased the net deferred tax asset and corresponding valuation allowance by $21,481,000 in the year ended December 31, 2021. As of December 31, 2022, we do not have unremitted earnings in our U.S. subsidiary. As of December 31, 2022, we had U.K. net operating losses of approximately $526,784,000, expenditure credit carryforwards of $760,000 and U.S. tax credit carryforwards of $4,136,000. Unsurrendered U.K. tax can be carried forward indefinitely to be offset against future taxable profits; however, this is restricted to an annual £5,000,000 allowance in each standalone company or group and above this allowance, there will be a 50% restriction in the profits that can be covered by losses brought forward. U.K. tax credit carryforwards can be carried forward indefinitely to be offset against future tax liabilities of the company. Our tax returns are under routine examination in the U.K. and U.S. tax jurisdictions. The scope of these examinations includes, but is not limited to, the review of our taxable presence in a jurisdiction, our deduction of certain items, our claims for research and development credits, our compliance with transfer pricing rules and regulations and the inclusion or exclusion of amounts from our tax returns as filed. The Company is no longer subject to examinations by tax authorities for the tax years 2015 and prior in the U.K. and there are no ongoing enquiries in the U.K. However, U.K. net operating losses from the tax years 2015 and prior would be subject to examination if and when used in a future tax return to offset taxable income. Our U.K. income tax returns have been accepted by His Majesty’s Revenue and Customs through the period ended December 31, 2016. The Company is subject to examinations by taxing authorities in the United States for all tax years 2019 through 2022. Our U.S. federal income tax return for the year ended December 31, 2020 is currently undergoing an examination by the U.S. Internal Revenue Service. We are also subject to audits by U.S. state taxing authorities where we have operations. Unrecognized tax benefits arise when the estimated benefit recorded in the financial statements differs from the amounts taken or expected to be taken in a tax return because of uncertainties in the tax law. As of December 31, 2022 and 2021, the Company had no unrecognized tax benefits.

Geographic information

Geographic information	12 Months Ended
	Dec. 31, 2022
Geographic information
Geographic information	Note 14 — Geographic information Operations by geographic area Revenue represents recognized income from the Astellas Collaboration Agreement, the GNE Collaboration and License Agreement and the GSK Collaboration and License Agreement. All revenue was derived in the United Kingdom. Long-lived assets (excluding intangibles, deferred tax and financial instruments) were located as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 U.K. ​ $ 42,387 ​ $ 29,701 U.S. ​ 29,148 ​ 21,668 Total long-lived assets ​ $ 71,535 ​ $ 51,369 Major customers: During the year ended December 31, 2022, 21%, 50% and 29% of the Company’s revenues were generated from Astellas, Genentech and GSK, respectively.

Restructuring programme

Restructuring programme	12 Months Ended
	Dec. 31, 2022
Restructuring programme
Restructuring programme	Note 15 – Restructuring programme ​ On November 8, 2022, the Company announced that in order to extend the Company’s cash runway from early 2024 into early 2025, it was re-focusing the business on core programs and deprioritizing non-core programs. It also announced that it was to undertake a restructuring of the Company including a headcount reduction of approximately 25% to 30% to be completed in the first quarter of 2023. ​ The redundancy process was initiated in the fourth quarter of 2022 and completed in the first quarter of 2023 with a reduction of approximately 25% of global headcount. The redundancy packages to be paid to departing staff comprise a combination of contractual termination benefits, relating to payments that arise from terms of employment contracts and statutory redundancy pay, and one-time employee termination benefits that were provided or enhanced specifically for this redundancy process. Due to the structure of the redundancy scheme and the different employment regulations affecting the Company’s U.K. and U.S. employees, some of the expense associated with the one-time employee termination benefits will be recognized over the remaining period of employee service to be rendered. Contractual termination benefits and other one-time employee termination benefits have been expensed and recognized in full in the year ended December 31, 2022. All expenses have been recognized in General and administrative expenses in the Statement of Operations. ​ The amounts expected to be incurred in relation to the redundancy programme are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ One-time ​ ​ ​ ​ ​ Contractual ​ employee ​ Total ​ ​ termination ​ termination ​ restructuring ​ ​ benefits ​ benefits ​ costs Amount incurred in the year ended, and cumulative amount incurred to, December 31, 2022 ​ $ 1,171 ​ $ 1,114 ​ $ 2,285 Remaining amount expected to be incurred in future periods ​ ​ — ​ ​ 947 ​ ​ 947 Total amount expected to be incurred ​ $ 1,171 ​ $ 2,061 ​ $ 3,232 ​ A provision for restructuring costs has been recognised in current liabilities as all payments are expected to be settled in the first quarter of 2023. The table below is a summary of the changes in the restructuring provision in the consolidated balance sheets in the year ended December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ One-time ​ ​ ​ ​ Contractual ​ employee ​ Total ​ ​ termination ​ termination ​ restructuring ​ benefits ​ benefits ​ provision Provision at January 1, 2022 ​ $ — ​ $ — ​ $ — Costs incurred and charged to General and administrative expenses ​ ​ 1,171 ​ ​ 1,114 ​ ​ 2,285 Provision at December 31, 2022 ​ $ 1,171 ​ $ 1,114 ​ $ 2,285 ​ No impairment losses were recognised as a result of the restructuring.

Subsequent events

Subsequent events	12 Months Ended
	Dec. 31, 2022
Subsequent events
Subsequent events	Note 16 – Subsequent events ​ The Astellas Collaboration Agreement termination ​ The Company and Universal Cells mutually agreed to terminate the Astellas Collaboration Agreement as of March 6, 2023 (the “Effective Date”). In connection with the termination, all licenses and sublicenses granted to either party pursuant to the Collaboration Agreement ceased, and each party is required to return all confidential information of the other party within 30 days of the Effective Date. Each party also agreed to destroy all cell lines and other materials of the other party in its possession within 30 days of the Effective Date. There were no termination penalties in connection with the termination. ​ ​ TCR 2 Therapeutics Inc merger agreement ​ On March 6, 2023 we announced entry into a definitive agreement under which we will combine with TCR² Therapeutics Inc in an all-stock transaction to create a preeminent cell therapy company focused on treating solid tumors. The combination provides extensive advantages for clinical development and product delivery supported by complementary technology platforms. The lead clinical franchises for the combined company utilize engineered T-cell therapies targeting MAGE A4 and mesothelin. These targets are expressed on a broad range of solid tumors and are supported by compelling early- and late-stage clinical data. The combined company also has a preclinical pipeline of additional target opportunities with development initially focused on PRAME and CD70. ​ The merger agreement was unanimously approved by the boards of directors of both companies. Following the closing of the transaction, Adaptimmune shareholders will own approximately 75% of the combined company and TCR2 stockholders will own approximately 25% of the combined company. The transaction is expected to close in Q2 2023, subject to the receipt of approvals by Adaptimmune shareholders and TCR2 stockholders and satisfaction or waiver of other customary closing conditions. Subject to the successful closing of the transaction, we currently estimate that the cash runway of the combined company will extend into early 2026. ​ As the transaction is not expected to close until Q2 2023, an estimate of the other financial effects of this event on the Company cannot yet be made. ​ ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Basis of presentation	(a) Basis of presentation The Consolidated Financial Statements of Adaptimmune Therapeutics plc and its subsidiaries and other financial information included in this Annual Report have been prepared in accordance with generally accepted accounting principles in the United States of America (“US GAAP”) and are presented in U.S. dollars. All significant intercompany accounts and transactions between the Company and its subsidiaries have been eliminated on consolidation.
Use of estimates in interim financial statements	(b) Use of estimates in financial statements The preparation of financial statements, in conformity with U.S. GAAP and SEC regulations, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the Consolidated Financial Statements and reported amounts of revenues and expenses during the reporting period. Estimates and assumptions are primarily made in relation to revenue recognition, estimation of the incremental borrowing rate for operating leases, and valuation allowances relating to deferred tax assets. If actual results differ from the Company’s estimates, or to the extent these estimates are adjusted in future periods, the Company’s results of operations could either benefit from, or be adversely affected by, any such change in estimate.
Going concern	(c) Going concern In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. Management considers that there are no conditions or events, in the aggregate, that raise substantial doubt about the entity’s ability to continue as a going concern for a period of at least one year from the date the financial statements are issued. Although the financial statements have been prepared on a going concern basis, if the Company fails to obtain sufficient additional financing in future, this may raise substantial doubt over the Company’s ability to continue as a going concern in future reporting periods. ​
Foreign currency	(d) Foreign currency The reporting currency of the Company is the U.S. dollar. The Company has determined the functional currency of the ultimate parent company, Adaptimmune Therapeutics plc, is U.S. dollars because it predominately raises finance and expends cash in U.S. dollars. The functional currency of subsidiary operations is the applicable local currency. Transactions in foreign currencies are translated into the functional currency of the subsidiary in which they occur at the foreign exchange rate in effect on at the date of the transaction. Monetary assets and liabilities denominated in foreign currencies at the balance sheet date are translated into the functional currency of the relevant subsidiary at the foreign exchange rate in effect on the balance sheet date. Foreign exchange differences arising on translation are recognized within other income (expense) in the Consolidated Statement of Operations. The Company’s U.K. subsidiary has an intercompany loan balance in U.S dollars payable to the ultimate parent company, Adaptimmune Therapeutics plc. Beginning on July 1, 2019, the intercompany loan was considered of a long-term investment nature as repayment is not planned or anticipated in the foreseeable future. It is Adaptimmune Therapeutics plc’s intent not to request payment of the intercompany loan for the foreseeable future. The foreign exchange gain or losses arising on the revaluation of intercompany loans of a long-term investment nature are reported within other comprehensive (loss) income, net of tax. ​ The results of operations for subsidiaries, whose functional currency is not the U.S. dollar, are translated at an average rate for the period where this rate approximates to the foreign exchange rates ruling at the dates of the transactions and the balance sheet are translated at foreign exchange rates ruling at the balance sheet date. Exchange differences arising from this translation of foreign operations are reported as an item of other comprehensive (loss) income. ​ Foreign exchange losses for the year ended December 31, 2022 of $536,000 and foreign exchange gains of $3,852,000 and $1,105,000 for the years ended December 31, 2021 and 2020 respectively, are included within Other (expense) income, net in the Consolidated Statement of Operations. ​
Fair value measurements	(e) Fair value measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The hierarchy defines three levels of valuation inputs: Level 1 — Quoted prices in active markets for identical assets or liabilities Level 2 — Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly Level 3 — Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability The carrying amounts of the Company’s cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses approximate fair value because of the short-term nature of these instruments. The fair value of marketable securities, which are measured at fair value on a recurring basis is detailed in Note 4, Financial Instruments. ​
Accumulated other comprehensive (loss) income	(f) Accumulated other comprehensive (loss) income The Company reports foreign currency translation adjustments and the foreign exchange gain or losses arising on the revaluation of intercompany loans of a long-term investment nature within Other comprehensive (loss) income. Unrealized gains and losses on available-for-sale debt securities are also reported within Other comprehensive (loss) income until a gain or loss is realized, at which point they are reclassified to Other (expense) income, net in the Consolidated Statement of Operations. The following table shows the changes in Accumulated other comprehensive (loss) income (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ Accumulated ​ ​ Total ​ ​ foreign ​ unrealized ​ ​ accumulated ​ ​ currency ​ gains (losses) on ​ ​ other ​ translation available-for-sale ​ ​ comprehensive ​ ​ adjustments ​ debt securities ​ ​ (loss) income ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at January 1, 2020 $ (7,302) ​ $ 38 ​ $ (7,264) Foreign currency translation adjustments ​ ​ (19,220) ​ ​ — ​ ​ (19,220) Foreign currency gains on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ 16,364 ​ ​ — ​ ​ 16,364 Unrealized holding gains on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ 161 ​ ​ 161 Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0 ​ ​ — ​ ​ (89) ​ ​ (89) Balance at December 31, 2020 ​ ​ (10,158) ​ ​ 110 ​ ​ (10,048) Foreign currency translation adjustments ​ ​ 5,808 ​ ​ — ​ ​ 5,808 Foreign currency losses on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ (6,435) ​ ​ — ​ ​ (6,435) Unrealized holding losses on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ (461) ​ ​ (461) Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0 ​ ​ — ​ ​ (6) ​ ​ (6) Balance at December 31, 2021 ​ ​ (10,785) ​ ​ (357) ​ ​ (11,142) Foreign currency translation adjustments ​ ​ 60,421 ​ ​ — ​ ​ 60,421 Foreign currency losses on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ (49,581) ​ ​ — ​ ​ (49,581) Unrealized holding losses on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ (573) ​ ​ (573) Balance at December 31, 2022 ​ $ 55 ​ $ (930) ​ $ (875) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following amounts were reclassified out of Other comprehensive (loss) income (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount reclassified ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ Affected line item in ​ ​ ​ ​ ​ ​ ​ ​ ​ Component of accumulated other comprehensive income ​ 2022 ​ 2021 ​ 2020 ​ the Statement of Operations Unrealized gains on available-for-sale securities ​ ​ ​ ​ ​ ​ Reclassification adjustment for gains on available-for-sale debt securities $ — ​ $ (6) ​ $ (89) ​ Other (expense) income, net ​ ​
Cash, cash equivalents and restricted cash	(g) Cash, cash equivalents and restricted cash The Company considers all highly liquid investments with a maturity at acquisition date of three months or less to be cash equivalents. Cash and cash equivalents comprise cash balances, commercial paper and corporate debt securities with maturities of three months or less at acquisition and short deposits with maturities of three months or less. The Company’s restricted cash consists of cash providing security for letters of credit in respect of lease agreements and credit cards. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same such amounts shown in the statement of cash flows (in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 108,033 ​ $ 149,948 Restricted cash ​ 1,569 ​ 1,718 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows ​ $ 109,602 ​ $ 151,666 ​
Available-for-sale debt securities	(h ) Available-for-sale debt securities As of December 31, 2022, the Company has the following investments in available-for-sale debt securities, (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Aggregate ​ ​ Remaining ​ Amortized ​ unrealized ​ unrealized ​ estimated ​ contractual maturity cost gains losses fair value Available-for-sale debt securities: ​ ​ ​ ​ Corporate debt securities Less than 3 months ​ $ 45,386 ​ $ — ​ $ (72) ​ $ 45,314 U.S. Treasury securities ​ Less than 3 months ​ ​ 5,953 ​ ​ 1 ​ ​ — ​ ​ 5,954 Agency bonds ​ 3 months to 1 year ​ ​ 5,008 ​ ​ — ​ ​ (154) ​ ​ 4,854 Corporate debt securities ​ 3 months to 1 year ​ ​ 41,154 ​ ​ — ​ ​ (704) ​ ​ 40,450 ​ ​ $ 97,501 ​ $ 1 ​ $ (930) ​ $ 96,572 ​ ​ As of December 31, 2021, the Company had the following investments in available-for-sale debt securities (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Aggregate ​ ​ Remaining ​ Amortized ​ unrealized ​ unrealized ​ estimated ​ contractual maturity cost gains losses fair value Available-for-sale debt securities: ​ ​ ​ ​ Corporate debt securities Less than 3 months ​ $ 45,304 ​ $ 22 ​ $ (21) ​ $ 45,305 Corporate debt securities ​ 3 months to 1 year ​ ​ 81,590 ​ ​ 11 ​ ​ (75) ​ ​ 81,526 Agency bonds ​ 1 year to 2 years ​ ​ 5,000 ​ ​ — ​ ​ (7) ​ ​ 4,993 Corporate debt securities ​ 1 year to 2 years ​ ​ 88,095 ​ ​ — ​ ​ (287) ​ ​ 87,808 ​ ​ $ 219,989 ​ $ 33 ​ $ (390) ​ $ 219,632 ​ At December 31, 2022, the Company has classified all of its available-for-sale debt securities as current assets on the accompanying Consolidated Balance Sheets based on the highly-liquid nature of these investment securities and because these investment securities are considered available for use in current operations. The investment in available-for-sale debt securities is measured at fair value at each reporting date. Unrealized gains and losses are excluded from earnings and are reported as a component of Other comprehensive (loss) income, net of tax. Realized gains and losses are included in Other income (expense), net. Interest income and amortization of premiums and discounts at acquisition are included in Interest income. In the year ended December 31, 2022, 2021 and 2020 proceeds from the maturity or redemption of available-for-sale debt securities were At each reporting date, the Company assesses whether each individual investment is impaired, which occurs if the fair value is less than the amortized cost, adjusted for amortization of premiums and discounts at acquisition. If the investment is impaired, the impairment is assessed to determine if it is other than temporary. Impairments judged to be other than temporary are included in other (expense) income, net when they are identified. The aggregate fair value (in thousands) and number of securities held by the Company (including those classified as cash equivalents) in an unrealized loss position as of December 31, 2022 and 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ December 31, 2021 ​ Fair market value of investments in an unrealized loss position ​ Number of investments in an unrealized loss position ​ Unrealized losses ​ Fair market value of investments in an unrealized loss position ​ Number of investments in an unrealized loss position ​ Unrealized losses Marketable securities in a continuous loss position for 12 months or longer: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 74,481 ​ ​ 16 ​ $ (679) ​ $ 8,232 ​ ​ 1 ​ $ (35) Agency bond ​ ​ 4,854 ​ ​ 1 ​ ​ (154) ​ ​ — ​ ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities in a continuous loss position for less than 12 months: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities $ 11,283 ​ 2 ​ $ (97) $ 163,258 ​ 34 $ (348) Agency bond ​ ​ — ​ ​ — ​ ​ — ​ ​ 4,993 ​ ​ 1 ​ ​ (7) ​ $ 90,618 ​ 19 ​ $ (930) $ 176,483 ​ 36 $ (390) ​ As of December 31, 2022 and 2021, these securities are not considered to be other than temporarily impaired because the impairments are not severe and are due to normal market and exchange rate fluctuations. Nineteen securities have been in an unrealized loss position for more than one year with a net total unrealized loss of $833,000. Furthermore, the Company does not intend to sell the debt securities in an unrealized loss position, and it is unlikely that the Company will be required to sell these securities before the recovery of the amortized cost. The cost of securities sold is based on the specific-identification method. Interest on debt securities is included in interest income. Our investment in available-for-sale debt securities is subject to credit risk. The Company’s investment policy limits investments to certain types of instruments, such as money market instruments and corporate debt securities, places restrictions on maturities and concentration by type and issuer and specifies the minimum credit ratings for all investments and the average credit quality of the portfolio.
Accounts receivable	(i) Accounts receivable Accounts receivable include amounts billed to customers and accrued receivables where only the passage of time is required before payment of amounts due. Management analyses current and past due accounts and determines if an allowance for uncollectible accounts is required based on collection experience and other relevant information. As of December 31, 2022 and 2021, the allowance for doubtful accounts is $nil. The process of estimating the uncollectible accounts involves assumptions and judgments and the ultimate amounts of uncollectible accounts receivable could be in excess of the amounts provided.
Clinical materials	(j) Clinical materials Clinical materials for use in research and development with alternative future use are capitalized as either other current assets or other non-current assets, depending on the timing of their expected consumption. The Company assesses whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable.
Property, plant and equipment	(k) Property, plant and equipment Property, plant and equipment is stated at cost, less any impairment losses, less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. The following table provides the range of estimated useful lives used for each asset type: ​ ​ ​ Computer equipment 3 to 5 years Laboratory equipment 5 years Office equipment 5 years Leasehold improvements the expected duration of the lease ​ Assets under construction are not depreciated until the asset is available and ready for its intended use. The Company assesses property, plant and equipment for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable.
Intangibles	(l) Intangibles Intangibles primarily include acquired software licenses and third party software in development, which are recorded at cost and amortized over the estimated useful lives of approximately three years. Intangibles are assessed for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable.
Leases	​ (m) Leases The Company determines whether an arrangement is a lease at contract inception by establishing if the contract conveys the right to use, or control the use of, identified property, plant, or equipment for a period of time in exchange for consideration. Leases may be classified as finance leases or operating leases. All the Company’s leases are classified as operating leases. Operating lease right-of-use (ROU) assets and operating lease liabilities recognized in the Consolidated Balance Sheet represent the right to use an underlying asset for the lease term and an obligation to make lease payments arising from the lease respectively. Operating lease ROU assets and operating lease liabilities are recognized at the lease commencement date based on the present value of minimum lease payments over the lease term. Since the rate implicit in the lease is not readily determinable, the Company uses its incremental borrowing rates (the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term for an amount equal to the lease payments in a similar economic environment) based on the information available at commencement date in determining the discount rate used to calculate the present value of lease payments. As the Company has no external borrowings, the incremental borrowing rates are determined using information on indicative borrowing rates that would be available to the Company based on the value, currency and borrowing term provided by financial institutions, adjusted for company and market specific factors. The lease term is based on the non-cancellable period in the lease contract, and options to extend the lease are included when it is reasonably certain that the Company will exercise that option. Any termination fees are included in the calculation of the ROU asset and lease liability when it is assumed that the lease will be terminated. The Company accounts for lease components (e.g. fixed payments including rent and termination costs) separately from non-lease components (e.g. common-area maintenance costs and service charges based on utilization) which are recognized over the period in which the obligation occurs. At each reporting date, the operating lease liabilities are increased by interest and reduced by repayments made under the lease agreements. The ROU asset is subsequently measured for an operating lease at the amount of the remeasured lease liability (i.e. the present value of the remaining lease payments), adjusted for the remaining balance of any lease incentives received, any cumulative prepaid or accrued rent if the lease payments are uneven throughout the lease term, and any unamortized initial direct costs. The Company has operating leases in relation to property for office and research facilities. All of the leases have termination options, and it is assumed that the initial termination options for the buildings will be activated for most of these. The maximum lease term without activation of termination options is to 2041. In May 2017, the Company entered into an agreement for the lease of a building at Milton Park, Oxfordshire, United Kingdom and in February 2018 the Company entered into the lease for that facility. The term of the lease expires on October 23, 2041, with termination options exercisable by the Company in October 2031 and October 2036. In September 2015, the Company entered into an agreement for a 25-year In July 2015, the Company entered into a 15-year 123 months In August 2021, the Company entered into a two-year The Company has elected not to recognize an ROU asset and lease liability for short-term leases. A short-term lease is a lease with a lease term of 12 months or less and which does not include an option to purchase the underlying asset that the lessee is reasonably certain to exercise. Operating lease costs are recognized on a straight-line basis over the lease term, and they are categorized within Research and development and General and administrative expenses in the Consolidated Statement of Operations. The operating lease cash flows are categorized under Net cash used in operating activities in the Consolidated Statement of Cash Flows.
Segmental reporting	(n) Segmental reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company’s chief operating decision maker (the “CODM”), its Chief Executive Officer, manages the Company’s operations on an integrated basis for the purposes of allocating resources. When evaluating the Company’s financial performance, the CODM reviews total revenues, total expenses and expenses by function and the CODM makes decisions using this information on a global basis. Accordingly, the Company has determined that it operates in one operating segment.
Revenue	(o) Revenue Revenue is recognized so as to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve that core principle, an entity should apply the following steps: ​ Step 1: Identify the contract(s) with a customer. Step 2: Identify the performance obligations in the contract. Step 3: Determine the transaction price. Step 4: Allocate the transaction price to the performance obligations in the contract. Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation. ​ Variable consideration The Company determines the variable consideration to be included in the transaction price by estimating the most likely amount that will be received and then applies a constraint to reduce the consideration to the amount which is probable of being received. The determination of whether a milestone is probable includes consideration of the following factors: · whether achievement of a development milestone is highly susceptible to factors outside the entity’s influence, such as milestones involving the judgment or actions of third parties, including regulatory bodies or the customer; ​ · whether the uncertainty about the achievement of the milestone is not expected to be resolved for a long period of time; ​ · whether the Company can reasonably predict that a milestone will be achieved based on previous experience; and ​ · the complexity and inherent uncertainty underlying the achievement of the milestone. ​ Percentage of completion The determination of the percentage of completion requires the Company to estimate the costs-to-complete the project. The Company makes a detailed estimate of the costs-to-complete, which is re-assessed every reporting period based on the latest project plan and discussions with project teams. If a change in facts or circumstances occurs, the estimate will be adjusted and the revenue will be recognized based on the revised estimate. The difference between the cumulative revenue recognized based on the previous estimate and the revenue recognized based on the revised estimate would be recognized as an adjustment to revenue in the period in which the change in estimate occurs. Contract assets and liabilities The Company recognizes a contract asset, when the value of satisfied (or part satisfied) performance obligations is in excess of the payment due to the Company, and deferred revenue (contract liability) when the amount of unconditional consideration is in excess of the value of satisfied (or part satisfied) performance obligations. Once a right to receive consideration is unconditional, that amount is presented as a receivable. Changes in deferred revenue typically arise due to: ● adjustments arising from a change in the estimate of the cost to complete the project, which results in a cumulative catch-up adjustment to revenue that affects the corresponding contract asset or deferred revenue; ​ ● a change in the estimate of the transaction price due to changes in the assessment of whether variable consideration is constrained because it is not considered probable of being received; ​ ● the recognition of revenue arising from deferred revenue; and ​ ● the reclassification of amounts to receivables when a right to consideration to becomes unconditional. ​ A change in the estimate of variable consideration constrained (for example, if a development milestone becomes probable of being received) could result in a significant change in the revenue recognized and deferred revenue.
Research and development expenditures	(p) Research and development expenditures Research and development expenditures are expensed as incurred. Expenses related to clinical trials are recognized as services are received. Nonrefundable advance payments for services are deferred and recognized in the Consolidated Statement of Operations as the services are rendered. This determination is based on an estimate of the services received and there may be instances when the payments to vendors exceed the level of services provided resulting in a prepayment of the clinical expense. If the actual timing of the performance of services varies from our estimate, the accrual or prepaid expense is adjusted accordingly. Upfront and milestone payments to third parties for in-licensed products or technology which has not yet received regulatory approval and which does not have alternative future use in R&D projects or otherwise are expensed as incurred. The Company expensed acquired in-process R&D of $2,316,000, $562,000 and $889,000 in the years ended December 31, 2022, 2021 and 2020, respectively. Milestone payments made to third parties either on or subsequent to regulatory approval are capitalized as an intangible asset and amortized over the remaining useful life of the product. Research and development expenditure is presented net of R&D tax and expenditure credits from the U.K. government, which are recognized over the period necessary to match the reimbursement with the related costs when it is probable that the Company has complied with any conditions attached and will receive the reimbursement. As a company that carries out extensive research and development activities, Adaptimmune Limited is able to surrender the trading losses that arise from its qualifying research and development activities for a payable tax credit. Reimbursable R&D tax and expenditure credits were $30,226,000, $34,082,000 and $19,442,000 in the years ended December 31, 2022, 2021 and 2020, respectively.
Share-based compensation	(q) Share-based compensation The Company awards certain employees options over the ordinary shares of the parent company. The cost of share-based awards issued to employees are measured at the grant-date fair value of the award and recognized as an expense over the requisite service period. The fair value of the options is determined using the Black-Scholes option-pricing model. Share options with graded-vesting schedules are recognized on a straight-line basis over the requisite service period for each separately vesting portion of the award. The Company has elected to account for forfeitures of stock options when they occur by reversing compensation cost previously recognized, in the period the award is forfeited, for an award that is forfeited before completion of the requisite service period.
Retirement benefits	(r) Retirement benefits The Company operates defined contribution pension schemes for its directors and employees. The contributions to this scheme are expensed to the Consolidated Statement of Operations as they fall due. The pension contributions for the years ended December 31, 2022, 2021, and 2020 were
Interest income	(s) Interest income Interest income arises on cash, cash equivalents and available-for-sale debt securities and is net of amortization (accretion) of the premium (discount) on purchase of the debt securities of $2,525,000, $5,276,000, and $3,836,000 in the years ended December 31, 2022, 2021 and 2020, respectively. ​
Income taxes	(t) Income taxes Income taxes for the period comprise current and deferred tax. Income tax is recognized in the Consolidated Statement of Operations except to the extent that it relates to items occurring during the year recognized either in other comprehensive income or directly in equity, in which case it is recognized in other comprehensive income or equity. Current tax is the expected tax payable or receivable on the taxable income or loss for the current or prior periods using tax rates enacted at the balance sheet date. Deferred tax is accounted for using the asset and liability method that requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement carrying amount and the tax bases of assets and liabilities at the applicable tax rates and for operating loss and tax credit carryforwards. A valuation allowance is provided to reduce deferred tax assets to the amount that is more likely than not to be realized. The Company evaluates the realizability of its deferred tax assets and adjusts the amount of the valuation allowance, if necessary. The factors used to assess the likelihood of realization include the Company’s forecast of income, carryback availability, reversing taxable temporary differences and available tax-planning strategies that could be implemented to realize the deferred tax assets. Income tax positions must meet a more-likely-than-not recognition threshold to be recognized. Income tax positions that previously failed to meet the more-likely-than-not threshold are recognized in the first subsequent financial reporting period in which that threshold is met. Previously recognized tax positions that no longer meet the more-likely-than-not threshold are derecognized in the first subsequent financial reporting period in which that threshold is no longer met. Recognized income tax positions are measured at the largest amount that is greater than 50 percent likely of being realized. We recognize potential accrued interest and penalties related to an underpayment of income taxes within the Consolidated Statement of Operations as income tax expense.
Loss per share	(u) Loss per share Basic loss per share is determined by dividing net loss attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. Diluted loss per share is determined by dividing net loss attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period, adjusted for the dilutive effect of all potential ordinary shares that were outstanding during the period. Potentially dilutive shares are excluded when the effect would be to increase diluted earnings per share or reduce diluted loss per share. The following table reconciles the numerator and denominator in the basic and diluted loss per share computation (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Numerator for basic and diluted loss per share ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (165,456) ​ $ (158,090) ​ $ (130,092) Net loss attributable to shareholders used for basic and diluted EPS calculation ​ $ (165,456) ​ $ (158,090) ​ $ (130,092) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for basic and diluted loss per share ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of shares used to calculate basic and diluted loss per share ​ ​ 967,242,403 ​ ​ 934,833,017 ​ ​ 854,783,763 ​ The effects of the following potentially dilutive equity instruments have been excluded from the diluted loss per share calculation because they would have an antidilutive effect on the loss per share for the period: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Weighted average number of share options (1) 155,673,264 115,225,480 93,812,818 ​ ​ From January 1, 2023 through to March 6, 2023, the Company granted 21,755,328 options over ordinary shares with an exercise price determined by reference to the market value of an ADS at the closing rate on the last business day prior to the date of grant, and 19,866,912 options over ordinary shares with an exercise price equal to the nominal value of the ordinary shares (£0.001 per share). These grants have not been included in the figures above.
Restructuring costs	(v) Restructuring costs Restructuring costs are comprised of amounts payable to employees because of redundancy related to restructuring programs. The Company classifies redundancy payments as either, contractual termination benefits if they relate to an ongoing benefit arrangement, including terms of employment contracts or termination benefits that arise from employment law in the relevant jurisdiction, or, one-time employee termination benefits if the benefits are not related to an ongoing benefit arrangement or represent a one-time enhancement to an ongoing benefit arrangement. based on the fair value of the liability as of the termination date and is recognized ratably over the required service period.
New accounting pronouncements	(w ) New accounting pronouncements Adopted in the year ended December 31, 2022 Disclosures by Business Entities about Government Assistance To be adopted in future periods Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU 2016-13 - Financial Instruments - Credit losses, which replaces the incurred loss impairment methodology for financial instruments in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The guidance is effective for the fiscal year beginning January 1, 2020, including interim periods within that fiscal year. In November 2019, the FASB issued ASU 2019-10 which resulted in the postponement of the effective date of the new guidance for eligible smaller reporting companies (as defined by the SEC), including the Company, at that time to the fiscal year beginning January 1, 2023. The Company intends to adopt the guidance in the fiscal year beginning January 1, 2023. The guidance must be adopted using a modified-retrospective approach and a prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the effective date. The Company has evaluated the impact of adopting the guidance on its Consolidated financial statements and does not expect there to be a material impact. ​ Accounting for Contract Assets and Contract Liabilities from Contracts with Customers ​

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Schedule of changes in Accumulated other comprehensive (loss) income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ Accumulated ​ ​ Total ​ ​ foreign ​ unrealized ​ ​ accumulated ​ ​ currency ​ gains (losses) on ​ ​ other ​ translation available-for-sale ​ ​ comprehensive ​ ​ adjustments ​ debt securities ​ ​ (loss) income ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at January 1, 2020 $ (7,302) ​ $ 38 ​ $ (7,264) Foreign currency translation adjustments ​ ​ (19,220) ​ ​ — ​ ​ (19,220) Foreign currency gains on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ 16,364 ​ ​ — ​ ​ 16,364 Unrealized holding gains on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ 161 ​ ​ 161 Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0 ​ ​ — ​ ​ (89) ​ ​ (89) Balance at December 31, 2020 ​ ​ (10,158) ​ ​ 110 ​ ​ (10,048) Foreign currency translation adjustments ​ ​ 5,808 ​ ​ — ​ ​ 5,808 Foreign currency losses on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ (6,435) ​ ​ — ​ ​ (6,435) Unrealized holding losses on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ (461) ​ ​ (461) Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0 ​ ​ — ​ ​ (6) ​ ​ (6) Balance at December 31, 2021 ​ ​ (10,785) ​ ​ (357) ​ ​ (11,142) Foreign currency translation adjustments ​ ​ 60,421 ​ ​ — ​ ​ 60,421 Foreign currency losses on intercompany loan of a long-term investment nature, net of tax of $0 ​ ​ (49,581) ​ ​ — ​ ​ (49,581) Unrealized holding losses on available-for-sale debt securities, net of tax of $0 ​ ​ — ​ ​ (573) ​ ​ (573) Balance at December 31, 2022 ​ $ 55 ​ $ (930) ​ $ (875) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of amounts reclassified out of other comprehensive (loss) income	The following amounts were reclassified out of Other comprehensive (loss) income (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount reclassified ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ Affected line item in ​ ​ ​ ​ ​ ​ ​ ​ ​ Component of accumulated other comprehensive income ​ 2022 ​ 2021 ​ 2020 ​ the Statement of Operations Unrealized gains on available-for-sale securities ​ ​ ​ ​ ​ ​ Reclassification adjustment for gains on available-for-sale debt securities $ — ​ $ (6) ​ $ (89) ​ Other (expense) income, net ​ ​
Schedule of the reconciliation of cash, cash equivalents, and restricted cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same such amounts shown in the statement of cash flows (in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 108,033 ​ $ 149,948 Restricted cash ​ 1,569 ​ 1,718 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows ​ $ 109,602 ​ $ 151,666 ​
Schedule of investments in available-for-sale debt securities	As of December 31, 2022, the Company has the following investments in available-for-sale debt securities, (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Aggregate ​ ​ Remaining ​ Amortized ​ unrealized ​ unrealized ​ estimated ​ contractual maturity cost gains losses fair value Available-for-sale debt securities: ​ ​ ​ ​ Corporate debt securities Less than 3 months ​ $ 45,386 ​ $ — ​ $ (72) ​ $ 45,314 U.S. Treasury securities ​ Less than 3 months ​ ​ 5,953 ​ ​ 1 ​ ​ — ​ ​ 5,954 Agency bonds ​ 3 months to 1 year ​ ​ 5,008 ​ ​ — ​ ​ (154) ​ ​ 4,854 Corporate debt securities ​ 3 months to 1 year ​ ​ 41,154 ​ ​ — ​ ​ (704) ​ ​ 40,450 ​ ​ $ 97,501 ​ $ 1 ​ $ (930) ​ $ 96,572 ​ ​ As of December 31, 2021, the Company had the following investments in available-for-sale debt securities (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ Aggregate ​ ​ Remaining ​ Amortized ​ unrealized ​ unrealized ​ estimated ​ contractual maturity cost gains losses fair value Available-for-sale debt securities: ​ ​ ​ ​ Corporate debt securities Less than 3 months ​ $ 45,304 ​ $ 22 ​ $ (21) ​ $ 45,305 Corporate debt securities ​ 3 months to 1 year ​ ​ 81,590 ​ ​ 11 ​ ​ (75) ​ ​ 81,526 Agency bonds ​ 1 year to 2 years ​ ​ 5,000 ​ ​ — ​ ​ (7) ​ ​ 4,993 Corporate debt securities ​ 1 year to 2 years ​ ​ 88,095 ​ ​ — ​ ​ (287) ​ ​ 87,808 ​ ​ $ 219,989 ​ $ 33 ​ $ (390) ​ $ 219,632 ​
Schedule of aggregate fair value and number of securities held by the Company in an unrealized loss position	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ December 31, 2021 ​ Fair market value of investments in an unrealized loss position ​ Number of investments in an unrealized loss position ​ Unrealized losses ​ Fair market value of investments in an unrealized loss position ​ Number of investments in an unrealized loss position ​ Unrealized losses Marketable securities in a continuous loss position for 12 months or longer: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 74,481 ​ ​ 16 ​ $ (679) ​ $ 8,232 ​ ​ 1 ​ $ (35) Agency bond ​ ​ 4,854 ​ ​ 1 ​ ​ (154) ​ ​ — ​ ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities in a continuous loss position for less than 12 months: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities $ 11,283 ​ 2 ​ $ (97) $ 163,258 ​ 34 $ (348) Agency bond ​ ​ — ​ ​ — ​ ​ — ​ ​ 4,993 ​ ​ 1 ​ ​ (7) ​ $ 90,618 ​ 19 ​ $ (930) $ 176,483 ​ 36 $ (390) ​
Schedule of estimated useful lives of property, plant and equipment	Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. The following table provides the range of estimated useful lives used for each asset type: ​ ​ ​ Computer equipment 3 to 5 years Laboratory equipment 5 years Office equipment 5 years Leasehold improvements the expected duration of the lease ​
Schedule of numerator and denominator in the basic and diluted loss per share computation	The following table reconciles the numerator and denominator in the basic and diluted loss per share computation (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Numerator for basic and diluted loss per share ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (165,456) ​ $ (158,090) ​ $ (130,092) Net loss attributable to shareholders used for basic and diluted EPS calculation ​ $ (165,456) ​ $ (158,090) ​ $ (130,092) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for basic and diluted loss per share ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of shares used to calculate basic and diluted loss per share ​ ​ 967,242,403 ​ ​ 934,833,017 ​ ​ 854,783,763 ​
Schedule of potentially dilutive equity instruments excluded from the diluted loss per share calculation	The effects of the following potentially dilutive equity instruments have been excluded from the diluted loss per share calculation because they would have an antidilutive effect on the loss per share for the period: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Weighted average number of share options (1) 155,673,264 115,225,480 93,812,818 ​

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2022
Revenue
Summary of revenue categories	Revenue comprises the following categories (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ December 31, ​ ​ 2022 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Development revenue ​ $ 27,148 $ 6,149 $ 3,958 ​ ​ $ 27,148 $ 6,149 $ 3,958 ​ ​

Financial instruments (Tables)

Financial instruments (Tables)	12 Months Ended
	Dec. 31, 2022
Financial instruments
Summary of fair value of assets and liabilities on a recurring basis based on fair value measurement criteria	Assets and liabilities measured at fair value on a recurring basis based on Level 1, Level 2, and Level 3 fair value measurement criteria as of December 31, 2022 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements using ​ ​ December 31, ​ Level 1 ​ Level 2 ​ Level 3 ​ 2022 ​ ​ ​ ​ ​ ​ Assets classified as cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 2,984 ​ $ 2,984 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets classified as available-for-sale debt securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 85,764 ​ $ 85,764 ​ $ — ​ $ — U.S. Treasury securities ​ ​ 5,954 ​ ​ — ​ ​ 5,954 ​ ​ — Agency bonds ​ 4,854 ​ ​ — ​ ​ 4,854 ​ ​ — ​ $ 96,572 ​ $ 85,764 $ 10,808 $ — ​ Assets and liabilities measured at fair value on a recurring basis based on Level 1, Level 2, and Level 3 fair value measurement criteria as of December 31, 2021 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ December 31, ​ Level 1 ​ Level 2 ​ Level 3 ​ ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets classified as available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate debt securities ​ $ 214,639 ​ $ 214,639 ​ $ — ​ $ — Agency bonds ​ ​ 4,993 ​ ​ — ​ ​ 4,993 ​ ​ — ​ ​ $ 219,632 ​ ​ 214,639 ​ ​ 4,993 ​ ​ — ​

Other current assets (Tables)

Other current assets (Tables)	12 Months Ended
	Dec. 31, 2022
Other current assets
Summary of other current assets	Other current assets consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Research and development credits receivable $ 30,162 $ 30,773 Prepayments ​ 9,472 ​ 9,043 Clinical materials ​ 1,279 ​ 746 VAT receivable ​ ​ 490 ​ ​ 2,482 Other current assets ​ 1,927 ​ 2,082 ​ ​ $ 43,330 ​ $ 45,126

Property, plant and equipment_2

Property, plant and equipment, net (Tables)	12 Months Ended
	Dec. 31, 2022
Property, plant and equipment, net
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Computer equipment ​ $ 3,818 ​ $ 3,692 Laboratory equipment ​ ​ 30,173 ​ ​ 28,002 Office equipment ​ ​ 925 ​ ​ 953 Leasehold improvements ​ ​ 28,459 ​ ​ 28,704 Assets under construction ​ ​ 28,729 ​ ​ 5,396 ​ ​ ​ 92,104 ​ ​ 66,747 Less accumulated depreciation ​ ​ (38,588) ​ ​ (36,253) ​ ​ $ 53,516 ​ $ 30,494 ​

Intangible assets, net (Tables)

Intangible assets, net (Tables)	12 Months Ended
	Dec. 31, 2022
Intangible assets, net
Schedule of intangible assets, net	Intangible assets, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Acquired software licenses ​ $ 4,930 ​ $ 4,842 Licensed IP rights – completed technology used in R&D ​ ​ 188 ​ ​ 209 ​ ​ ​ 5,118 ​ ​ 5,051 Less accumulated amortization ​ ​ (4,676) ​ ​ (4,051) ​ ​ $ 442 ​ $ 1,000 ​

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2022
Operating leases
Schedule of lease cost	The following table shows the lease costs for the years ended December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ ​ December 31, ​ ​ 2022 2021 Lease cost: ​ ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 4,367 $ 4,259 Short-term lease cost ​ ​ 389 ​ 419 ​ ​ $ 4,756 $ 4,678 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ ​ December 31, ​ ​ ​ 2022 2021 Other information: ​ ​ ​ ​ ​ ​ ​ Operating cash outflows from operating leases (in thousands) ​ ​ $ 3,746 $ 4,101 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term - operating leases ​ ​ 6.9 years ​ 7.8 years Weighted-average discount rate - operating leases ​ ​ 6.8% ​ 6.8%
Schedule of maturities of operating lease liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ ​ December 31, ​ ​ 2022 2021 Lease cost: ​ ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 4,367 $ 4,259 Short-term lease cost ​ ​ 389 ​ 419 ​ ​ $ 4,756 $ 4,678 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ ​ ​ December 31, ​ ​ ​ 2022 2021 Other information: ​ ​ ​ ​ ​ ​ ​ Operating cash outflows from operating leases (in thousands) ​ ​ $ 3,746 $ 4,101 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ 2022 ​ 2021 ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term - operating leases ​ ​ 6.9 years ​ 7.8 years Weighted-average discount rate - operating leases ​ ​ 6.8% ​ 6.8%

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	12 Months Ended
	Dec. 31, 2022
Accrued expenses and other current liabilities
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Accrued clinical and development expenditure ​ $ 16,749 ​ $ 13,436 Accrued employee expenses ​ ​ 8,232 ​ ​ 11,758 Other accrued expenditure ​ ​ 4,079 ​ ​ 4,388 Other ​ 2,155 ​ 327 ​ ​ $ 31,215 ​ $ 29,909 ​

Share-based compensation (Table

Share-based compensation (Tables)	12 Months Ended
	Dec. 31, 2022
Share-based compensation
Summary of share-based compensation expense included in the consolidated statements of operations	The following table shows the total share-based compensation expense included in the Consolidated Statements of Operations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Research and development $ 6,264 ​ $ 9,052 ​ $ 4,417 General and administrative 11,976 ​ 11,577 ​ 5,997 ​ $ 18,240 ​ $ 20,629 ​ $ 10,414 ​
Summary of information about share options granted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ December 31, ​ 2022 2021 ​ 2020 Number of options over ordinary shares granted ​ 31,826,293 ​ ​ 21,300,998 ​ ​ 15,595,374 Weighted average fair value of ordinary shares options $ 0.37 ​ $ 0.70 ​ $ 0.59 Number of additional options with a nominal exercise price granted ​ 24,248,424 ​ ​ 17,765,778 ​ ​ 8,282,152 Weighted average fair value of options with a nominal exercise price $ 0.51 ​ $ 0.97 ​ $ 0.85
Summary of all stock option activity	The following table summarizes all stock option activity for the year ended December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ ​ ​ exercise price ​ contractual ​ intrinsic value ​ ​ Options ​ per option ​ term (years) ​ (thousands) Outstanding at January 1, 2022 114,915,438 ​ £ 0.52 ​ ​ ​ ​ ​ Changes during the period: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Granted 56,074,717 ​ £ 0.21 ​ ​ ​ ​ ​ Exercised ​ (5,823,534) ​ £ 0.01 ​ ​ ​ ​ ​ Expired ​ (3,238,371) ​ £ 0.69 ​ ​ ​ ​ ​ Forfeited (9,389,161) ​ £ 0.21 ​ ​ ​ ​ ​ Outstanding at December 31, 2022 152,539,089 ​ £ 0.44 7.0 ​ £ 8,082 Exercisable at December 31, 2022 75,064,373 ​ £ 0.64 5.3 ​ £ 1,077 ​
Summarizes information about stock options granted based on the market value at grant date which were outstanding	The following table summarizes information about stock options granted based on the market value at grant date which were outstanding as of December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ ​ ​ exercise price ​ contractual ​ intrinsic value ​ Options per option term (years) (thousands) Outstanding at January 1, 2022 87,387,314 ​ £ 0.68 ​ ​ ​ ​ ​ Changes during the period: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Granted 31,826,293 ​ £ 0.37 ​ ​ ​ ​ ​ Exercised ​ (318,222) ​ £ 0.11 ​ ​ ​ ​ ​ Expired ​ (3,077,532) ​ £ 0.72 ​ ​ ​ ​ ​ Forfeited (3,340,390) ​ £ 0.59 ​ ​ ​ ​ ​ Outstanding at December 31, 2022 112,477,463 ​ £ 0.60 6.5 ​ £ 68 Exercisable at December 31, 2022 69,769,359 ​ £ 0.68 5.2 ​ £ 18 ​
Summary of information about RSU-style options which are outstanding	The following table summarizes information about RSU-style options which were outstanding as of December 31, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Average ​ ​ ​ ​ ​ ​ ​ ​ remaining ​ Aggregate ​ ​ ​ ​ ​ contractual ​ intrinsic value ​ Options ​ term (years) (thousands) Outstanding at January 1, 2022 27,528,124 ​ ​ 8.5 ​ ​ 12,720 Changes during the period: ​ ​ ​ ​ ​ ​ ​ ​ Granted 24,248,424 ​ ​ ​ ​ ​ ​ Exercised ​ (5,505,312) ​ ​ ​ ​ ​ ​ Expired ​ (160,839) ​ ​ ​ ​ ​ ​ Forfeited (6,048,771) ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2022 40,061,626 ​ ​ 8.4 £ 8,014 Exercisable at December 31, 2022 5,295,014 ​ ​ 6.6 £ 1,059 ​
Summary of information about stock options outstanding	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding ​ Exercisable ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ average ​ Weighted- ​ ​ ​ Weighted- ​ ​ ​ Total share ​ remaining ​ average ​ Total share ​ average Exercise price options contractual life exercise price options exercise price £ 0 40,061,626 ​ 8.4 £ 0.00 ​ 5,295,014 £ 0.00 ​ 0.01 - 0.25 ​ 8,412,475 ​ 9.1 ​ ​ 0.22 ​ 738,325 ​ ​ 0.19 ​ 0.26 - 0.50 38,339,879 ​ 6.9 ​ 0.41 ​ 14,287,927 ​ 0.42 ​ 0.51 - 0.75 36,255,404 ​ 5.9 ​ 0.60 ​ 32,291,011 ​ 0.61 ​ 0.76 - 1.00 24,103,880 ​ 6.1 ​ 0.84 ​ 17,446,630 ​ 0.87 ​ 1.01 - 1.50 3,974,824 ​ 6.3 ​ 1.25 ​ 3,614,465 ​ 1.26 ​ 1.51 - 2.00 1,391,001 ​ 4.7 ​ 1.70 ​ 1,391,001 ​ 1.70 Total 152,539,089 7.0 £ 0.44 75,064,373 £ 0.64 ​
Summary of the assumptions used to estimate the fair values of the share options granted using the Black-Scholes option-pricing model	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 Expected term 5 years 5 years 5 years Expected volatility ​ 99-101% ​ 98-100% ​ 90-99% Risk free rate 0.94-3.90% 0.00-0.61% 0.00-0.42% Expected dividend yield ​ 0% ​ 0% ​ 0% ​

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income taxes
Schedule of loss before income tax expenses	Loss before income tax expense is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 U.S. ​ $ (3,245) ​ $ 1,625 ​ $ (1,359) U.K. ​ ​ (159,714) ​ ​ (158,924) ​ ​ (128,571) Loss before income tax expense ​ $ (162,959) ​ $ (157,299) ​ $ (129,930) ​
Schedule of components of income tax expense	The components of income tax expense are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ December 31, ​ December 31, ​ December 31, ​ 2022 2021 2020 United States: ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ $ 2,492 ​ $ 791 ​ $ 162 State and local ​ ​ 5 ​ ​ — ​ ​ — U.K. ​ ​ — ​ ​ — ​ ​ — Total current tax expense ​ ​ 2,497 ​ ​ 791 ​ ​ 162 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States: ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ ​ — ​ ​ — ​ ​ — State and local ​ ​ — ​ ​ — ​ ​ — U.K. ​ ​ — ​ ​ — ​ ​ — Total deferred tax expense ​ ​ — ​ ​ — ​ ​ — Total income tax expense ​ $ 2,497 ​ $ 791 ​ $ 162 ​
Schedule of deferred tax assets and liabilities	As of December 31, 2022 and 2021 the tax effects of temporary differences and carryforwards that give rise to deferred tax assets and liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 Deferred tax liabilities ​ ​ ​ ​ ​ ​ Property, plant and equipment: ​ $ (3,486) ​ $ (922) Operating lease right-of-use assets ​ ​ (1,529) ​ ​ (1,757) Other ​ ​ (251) ​ ​ (238) Total ​ ​ (5,266) ​ ​ (2,917) ​ ​ ​ ​ ​ ​ ​ Deferred tax assets ​ ​ ​ ​ ​ ​ Share-based compensation expense ​ ​ 16,963 ​ ​ 15,584 Intangible assets ​ ​ 1,324 ​ ​ 2,401 Operating lease liabilities ​ ​ 1,958 ​ ​ 2,143 Net operating loss and tax credit carryforwards ​ ​ 136,592 ​ ​ 114,972 Capitalized research and development expenditure ​ ​ 8,409 ​ ​ — Other ​ ​ 532 ​ ​ 260 Total ​ ​ 165,778 ​ ​ 135,360 Valuation allowance ​ ​ (160,512) ​ ​ (132,443) ​ ​ ​ 5,266 ​ ​ 2,917 Net deferred tax asset/(liability) ​ $ — ​ $ — ​
Schedule of movements in deferred tax asset valuation allowance	The movements in the deferred tax asset valuation allowance for the year ended December 31, 2022 and 2021 are as follows (thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 ​ 2021 Valuation allowance at January 1, ​ $ 132,443 ​ $ 82,398 Increase in valuation allowance through net loss ​ ​ 30,455 ​ ​ 50,046 Increase in valuation allowance through other comprehensive loss ​ ​ 9,836 ​ ​ 1,512 Foreign currency translation adjustments ​ ​ (12,222) ​ ​ (1,513) Net change in the valuation allowance ​ ​ 28,069 ​ ​ 50,045 ​ ​ $ 160,512 ​ $ 132,443 ​
Schedule of the effective tax rate reconciliation	Reconciliation of the U.K. statutory income tax rate, the income tax rate of the country of domicile of the Company, to the Company's effective income tax rate is as follows (in percentages): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended ​ Year ended ​ Year ended ​ ​ ​ December 31, ​ December 31, ​ December 31, ​ ​ ​ 2022 2021 2020 U.K. tax rate ​ 19.0 % 19.0 % 19.0 % Tax-exempt reimbursable tax credits included within pretax Research and development expense ​ 3.6 % 4.1 % 2.8 % Surrender of R&D expenditures for R&D tax credit refund ​ (10.5) % (10.3) % (8.4) % Expenses not deductible ​ (0.3) % (0.2) % (1.4) % Change in valuation allowances ​ (18.8) % (31.8) % (17.8) % Change in tax rates ​ — % 13.7 % 4.1 % Difference in tax rates ​ 5.5 % 4.4 % — % R&D tax credits generated ​ 2.1 % 2.0 % 1.8 % Other ​ (2.1) % (1.4) % (0.1) % Effective income tax rate ​ (1.5) % (0.5) % (0.0) % ​

Geographic information (Tables)

Geographic information (Tables)	12 Months Ended
	Dec. 31, 2022
Geographic information
Schedule of long-lived assets	Long-lived assets (excluding intangibles, deferred tax and financial instruments) were located as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2022 2021 U.K. ​ $ 42,387 ​ $ 29,701 U.S. ​ 29,148 ​ 21,668 Total long-lived assets ​ $ 71,535 ​ $ 51,369

Restructuring programme (Tables

Restructuring programme (Tables)	12 Months Ended
	Dec. 31, 2022
Restructuring programme
Schedule of movement in the restructuring provision	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ One-time ​ ​ ​ ​ Contractual ​ employee ​ Total ​ ​ termination ​ termination ​ restructuring ​ benefits ​ benefits ​ provision Provision at January 1, 2022 ​ $ — ​ $ — ​ $ — Costs incurred and charged to General and administrative expenses ​ ​ 1,171 ​ ​ 1,114 ​ ​ 2,285 Provision at December 31, 2022 ​ $ 1,171 ​ $ 1,114 ​ $ 2,285 ​
Schedule of amounts expected to be incurred in relation to the redundancy programme.	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ One-time ​ ​ ​ ​ ​ Contractual ​ employee ​ Total ​ ​ termination ​ termination ​ restructuring ​ ​ benefits ​ benefits ​ costs Amount incurred in the year ended, and cumulative amount incurred to, December 31, 2022 ​ $ 1,171 ​ $ 1,114 ​ $ 2,285 Remaining amount expected to be incurred in future periods ​ ​ — ​ ​ 947 ​ ​ 947 Total amount expected to be incurred ​ $ 1,171 ​ $ 2,061 ​ $ 3,232 ​

General (Details)

General (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
General
Accumulated deficit	$ 909,302,000	$ 743,846,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Foreign currency (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Other (expense) income, net
Foreign exchange gains (losses)	$ (536,000)	$ 3,852,000	$ 1,105,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Changes in Accumulated other comprehensive (loss) income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Changes in the Accumulated other comprehensive loss (income)
Balance at the beginning of the period	$ 205,960	$ 341,227	$ 123,638
Foreign currency translation adjustments	60,421	5,808	(19,220)
Foreign currency gains (losses) on intercompany loan of a long-term investment nature, net of tax of $0	(49,581)	(6,435)	16,364
Unrealized holding gain (losses) on available-for-sale debt securities, net of tax of $0	(573)	(461)	161
Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0		(6)	(89)
Balance at the end of the period	81,878	205,960	341,227
Foreign currency gain (losses) on intercompany loan of a long-term investment nature, tax	0	0	0
Unrealized holding gains (losses) on available-for-sale debt securities, tax	0	0	0
Reclassification adjustment for gains on available-for-sale debt securities included in net loss, tax	0	0	0
Accumulated other comprehensive (loss) income
Changes in the Accumulated other comprehensive loss (income)
Balance at the beginning of the period	(11,142)	(10,048)	(7,264)
Foreign currency translation adjustments	60,421	5,808	(19,220)
Foreign currency gains (losses) on intercompany loan of a long-term investment nature, net of tax of $0	(49,581)	(6,435)	16,364
Unrealized holding gain (losses) on available-for-sale debt securities, net of tax of $0	(573)	(461)	161
Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0		(6)	(89)
Balance at the end of the period	(875)	(11,142)	(10,048)
Accumulated foreign currency translation adjustments
Changes in the Accumulated other comprehensive loss (income)
Balance at the beginning of the period	(10,785)	(10,158)	(7,302)
Foreign currency translation adjustments	60,421	5,808	(19,220)
Foreign currency gains (losses) on intercompany loan of a long-term investment nature, net of tax of $0	(49,581)	(6,435)	16,364
Balance at the end of the period	55	(10,785)	(10,158)
Accumulated unrealized gains (losses) on available-for-sale debt securities
Changes in the Accumulated other comprehensive loss (income)
Balance at the beginning of the period	(357)	110	38
Unrealized holding gain (losses) on available-for-sale debt securities, net of tax of $0	(573)	(461)	161
Reclassification from accumulated other comprehensive (loss) income of gains on available-for-sale debt securities included in net income, net of tax of $0		(6)	(89)
Balance at the end of the period	$ (930)	$ (357)	$ 110

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Reclassification out of Other comprehensive (loss) income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reclassification adjustment for gains on available-for-sale debt securities	$ (6)	$ (89)
Other (expense) income, net
Reclassification adjustment for gains on available-for-sale debt securities	$ (6)	$ (89)

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary of Significant Accounting Policies
Cash and cash equivalents	$ 108,033	$ 149,948
Restricted cash	1,569	1,718
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$ 109,602	$ 151,666	$ 61,484	$ 54,908

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Available-for-sale debt securities (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) security	Dec. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($)
Marketable securities
Proceeds from the maturity or redemption of available-for-sale debt securities	$ 166,994,000	$ 224,343,000	$ 105,022,000
Realized gain on available-for-sale debt securities	0	6,000	$ 89,000
Fair market value of investments in an unrealized loss position	$ 90,618,000	$ 176,483,000
Number of available-for-sale securities in an unrealized loss position, less than 12 months | security	19	36
Unrealized losses, 12 months or longer	$ (833,000)
Unrealized losses, less than 12 months	(930,000)	$ (390,000)
Marketable securities
Marketable securities
Amortized cost	97,501,000	219,989,000
Gross unrealized gains	1,000	33,000
Gross unrealized losses	(930,000)	(390,000)
Aggregate estimated fair value	96,572,000	219,632,000
Corporate Debt Securities Maturity Period Less Than Three Months | Marketable securities
Marketable securities
Amortized cost	45,386,000	45,304,000
Gross unrealized gains		22,000
Gross unrealized losses	(72,000)	(21,000)
Aggregate estimated fair value	$ 45,314,000	$ 45,305,000
Corporate Debt Securities Maturity Period Less Than Three Months | Maximum | Marketable securities
Marketable securities
Available for sale securities debt maturity period	3 months	3 months
U.S. Treasury Securities Maturity Period Less Than Three Months
Marketable securities
Amortized cost	$ 5,953,000
Gross unrealized gains	1,000
Aggregate estimated fair value	$ 5,954,000
U.S. Treasury Securities Maturity Period Less Than Three Months | Maximum | Marketable securities
Marketable securities
Available for sale securities debt maturity period	3 months
Corporate Debt Securities Maturity Period Three Months To One Year | Marketable securities
Marketable securities
Amortized cost	$ 41,154,000	$ 81,590,000
Gross unrealized gains		11,000
Gross unrealized losses	(704,000)	(75,000)
Aggregate estimated fair value	$ 40,450,000	$ 81,526,000
Corporate Debt Securities Maturity Period Three Months To One Year | Minimum | Marketable securities
Marketable securities
Available for sale securities debt maturity period	3 months	3 months
Corporate Debt Securities Maturity Period Three Months To One Year | Maximum | Marketable securities
Marketable securities
Available for sale securities debt maturity period	1 year	1 year
Corporate Debt Securities Maturity Period One Year To Two Years | Marketable securities
Marketable securities
Amortized cost		$ 88,095,000
Gross unrealized gains
Gross unrealized losses		(287,000)
Aggregate estimated fair value		$ 87,808,000
Corporate Debt Securities Maturity Period One Year To Two Years | Minimum | Marketable securities
Marketable securities
Available for sale securities debt maturity period		1 year
Corporate Debt Securities Maturity Period One Year To Two Years | Maximum | Marketable securities
Marketable securities
Available for sale securities debt maturity period		2 years
Agency Bond Maturity Period One Year To Two Years | Marketable securities
Marketable securities
Amortized cost	$ 5,008,000	$ 5,000,000
Gross unrealized gains
Gross unrealized losses	(154,000)	(7,000)
Aggregate estimated fair value	$ 4,854,000	4,993,000
Fair market value of investments in an unrealized loss position		$ 4,993,000
Number of available-for-sale securities in an unrealized loss position, less than 12 months | security		1
Unrealized losses, less than 12 months		$ (7,000)
Agency Bond Maturity Period One Year To Two Years | Minimum | Marketable securities
Marketable securities
Available for sale securities debt maturity period	3 months	1 year
Agency Bond Maturity Period One Year To Two Years | Maximum | Marketable securities
Marketable securities
Available for sale securities debt maturity period	1 year	2 years
Agency Bond Continuous Loss Position For Less Than 12 Months | Marketable securities
Marketable securities
Fair market value of investments in an unrealized loss position	$ 4,854,000
Number of available-for-sale securities in an unrealized loss position, 12 months or longer | security	1
Unrealized losses, 12 months or longer	$ (154,000)
Corporate Debt Securities Continuous Loss Position For 12 Months Or Longer | Marketable securities
Marketable securities
Fair market value of investments in an unrealized loss position	$ 74,481,000	$ 8,232,000
Number of available-for-sale securities in an unrealized loss position, 12 months or longer | security	16	1
Unrealized losses, 12 months or longer	$ (679,000)	$ (35,000)
Corporate Debt Securities Continuous Loss Position For Less Than 12 Months | Marketable securities
Marketable securities
Fair market value of investments in an unrealized loss position	$ 11,283,000	$ 163,258,000
Number of available-for-sale securities in an unrealized loss position, less than 12 months | security	2	34
Unrealized losses, less than 12 months	$ (97,000)	$ (348,000)

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Accounts receivable (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Accounts receivable
Allowance for doubtful accounts

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Property, plant and equipment (Details)	12 Months Ended
	Dec. 31, 2022
Computer equipment | Minimum
Property, plant and equipment
Estimated useful lives (in years)	3 years
Computer equipment | Maximum
Property, plant and equipment
Estimated useful lives (in years)	5 years
Laboratory equipment
Property, plant and equipment
Estimated useful lives (in years)	5 years
Office equipment
Property, plant and equipment
Estimated useful lives (in years)	5 years

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Intangibles (Details)	12 Months Ended
	Dec. 31, 2022
Third party software licenses and development
Intangibles
Estimated useful life (in years)	3 years

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Leases (Details)	1 Months Ended
	Jul. 31, 2015	Aug. 31, 2021	Sep. 30, 2015
Lease term (in years)	15 years
Lease for Offices and Research facilities in Philadelphia, U.S.
Early termination option (in months)	123 months
Lease for Research and development facility in Oxfordshire, U.K.
Lease term (in years)			25 years
Lease of Building at Milton Park, Oxfordshire, United Kingdom
Lease term (in years)		2 years

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Segment Reporting (Details)	12 Months Ended
	Dec. 31, 2022 segment
Segmental reporting
Number of operating segments	1

Summary of Significant Accou_14

Summary of Significant Accounting Policies - Research and Development Expenditure (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Summary of Significant Accounting Policies
Acquired in-process R&D expensed	$ 2,316,000	$ 562,000	$ 889,000
Research and Development Asset Acquired Other than through Business Combination, Writeoff, Statement of Income or Comprehensive Income [Extensible Enumeration]	Research and Development Expense	Research and Development Expense	Research and Development Expense
Reimbursement of Research and Development Tax and Expenditure Credit	$ 30,226,000	$ 34,082,000	$ 19,442,000

Summary of Significant Accou_15

Summary of Significant Accounting Policies - Retirement Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Summary of Significant Accounting Policies
Pension contributions	$ 2,810,000	$ 2,505,000	$ 2,070,700

Summary of Significant Accou_16

Summary of Significant Accounting Policies - Interest income (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Summary of Significant Accounting Policies
Amortization (accretion) of the premium (discount)	$ 2,525,000	$ 5,276,000	$ 3,836,000

Summary of Significant Accou_17

Summary of Significant Accounting Policies - Loss per share (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator for basic and diluted loss per share
Net loss	$ (165,456)	$ (158,090)	$ (130,092)
Net loss attributable to shareholders used for basic and diluted EPS calculation	$ (165,456)	$ (158,090)	$ (130,092)
Denominator for basic and diluted loss per share
Weighted average number of shares used to calculate basic and diluted loss per share	967,242,403	934,833,017	854,783,763

Summary of Significant Accou_18

Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share options
Antidilutive securities
Weighted average number of share options (in shares)	155,673,264	115,225,480	93,812,818

Summary of Significant Accou_19

Summary of Significant Accounting Policies - Options (Details) - £ / shares	2 Months Ended
	Mar. 14, 2022	Dec. 31, 2022	Dec. 31, 2021
Nominal value of ordinary shares		£ 0.001	£ 0.001
Exercise price determined by reference to the market value of an ADS at the date of grant
Number of options over ordinary shares granted (in shares)	21,755,328
Exercise price equal to the nominal value of the ordinary shares
Number of options over ordinary shares granted (in shares)	19,866,912

Revenue - Revenue from contract

Revenue - Revenue from contracts with customers (Details)			1 Months Ended			12 Months Ended
	Jan. 01, 2022 USD ($)	Jan. 01, 2021 USD ($)	Dec. 31, 2022 USD ($)	Oct. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Revenue
Revenue						$ 27,148,000	$ 6,149,000	$ 3,958,000
Increase (decrease) in deferred revenue	$ 15,010,000	$ 147,330,000				3,874,000	149,785,000	47,973,000
Deferred revenue	$ 199,422,000	$ 52,092,000	$ 184,412,000			184,412,000	$ 199,422,000
Amount of decrease in deferred income caused by the change in the exchange rate						$ 20,601,000
Exchange rate			1.21			1.21	1.35
Revenue recognized in the period						$ 17,648,000		1,498,000
Development revenue
Revenue
Revenue						27,148,000	$ 6,149,000	$ 3,958,000
GSK Collaboration And License Agreement
Revenue
Milestone payments received					$ 4,200,000
Genentech, Inc.
Revenue
Milestone payments received			$ 20,000,000
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements			$ 340,713,000			$ 340,713,000
Upfront payment received				$ 150,000,000

Revenue - Collaboration Agreeme

Revenue - Collaboration Agreement - The Genentech Collaboration and License Agreement (Details) $ in Thousands		3 Months Ended	12 Months Ended
	Sep. 03, 2021 USD ($) item	Dec. 31, 2021 USD ($)	Dec. 31, 2022 USD ($)
Revenue
Number of additional terms | item	2
Collaboration target basis days	180 days
Number of days without HSR clearance after effective date before termination	180 days
Strategic Collaboration and License Agreement
Revenue
Number of types of therapies to be co-developed | item	2
Initial period of collaborated research	8 years
Number of additional terms | item	2
Number of additional years	2 years
Number of years additional payments are due	5 years
Upfront payment received		$ 150,000
Amount of additional payments receivable under the research program	$ 150,000
Total Number off the Shelf Collaboration Targets | item	5
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements			$ 283,206
Amount of transaction price of the agreement at inception			313,600
Collaboration Agreement Research Service and Rights, Upfront Payment Earned			150,000
Collaboration Agreement Research Service and Rights, Additional Payment Earned			150,000
Collaboration Agreement Research Service and Rights, Other Consideration			13,600
Strategic Collaboration and License Agreement | Material Right to Designate the Additional Off the Shelf Collaboration Target
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements			12,766
Strategic Collaboration and License Agreement | Research Service Rights Granted for Initial Off the Shelf Collaboration Targets
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements			174,125
Strategic Collaboration and License Agreement | Research Service Rights Granted for Personalized Therapies
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements			90,169
Strategic Collaboration and License Agreement | Material Right for First Option Extend the Research Term
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements			4,917
Strategic Collaboration and License Agreement | Material Right for Second Option Extend the Research Term
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements			$ 1,229
Development Milestone | Strategic Collaboration and License Agreement | Maximum
Revenue
Milestone payments	$ 200,000
Development Milestone - Off The Shelf Member T-cell Therapies | Strategic Collaboration and License Agreement | Maximum
Revenue
Milestone payments	100,000
Research Milestone | Strategic Collaboration and License Agreement | Maximum
Revenue
Milestone payments	$ 50,000
Commercialisation Milestone | Strategic Collaboration and License Agreement
Revenue
Total Number off the Shelf Collaboration Targets | item	5
Commercialisation Milestone | Strategic Collaboration and License Agreement | Maximum
Revenue
Milestone payments	$ 1,100,000
Sales Milestone | Strategic Collaboration and License Agreement
Revenue
Number of co-development targets | item	5
Sales Milestone | Strategic Collaboration and License Agreement | Maximum
Revenue
Milestone payments	$ 1,500,000
Regulatory, Sales, And Royalties Milestones | Strategic Collaboration and License Agreement
Revenue
Percentage of profit (loss) sharing ratio	50%
Regulatory, Sales, And Royalties Milestones | Strategic Collaboration and License Agreement | Maximum
Revenue
Milestone payments	$ 800,000

Revenue - Collaboration Agree_2

Revenue - Collaboration Agreement - The Astellas Collaboration Agreement (Details) - Astellas Collaboration Agreement.		12 Months Ended
	Jan. 13, 2020 USD ($) item	Dec. 31, 2022 USD ($) item
Revenue
Upfront payment received	$ 50,000,000
Number Of Co Development Target | item	3
Number of independent targets | item	2	2
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements		$ 57,509,000
Amount of transaction price of the agreement at inception	$ 50,000,000
Rights granted, first and second independent target
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements		13,474,000
Research services and rights granted under the co-exclusive license, first co-development target
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements		10,071,000
Research services and rights under the co-exclusive license, second co-development target
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements		13,985,000
Research services and rights under the co-exclusive license, third co-development target
Revenue
Aggregate amount of the transaction price that is allocated to performance obligations that are unsatisfied or partially satisfied under the agreements		$ 6,505,000
Maximum
Revenue
Potential milestone payments to be received	847,500,000
Research funding the entity is entitled to receive per year on a per collaboration target basis	7,500,000
Development milestone for each co-developed and co-commercialized product | Maximum
Revenue
Potential milestone payments to be received	73,750,000
Development milestone per product developed unilaterally | Maximum
Revenue
Potential milestone payments to be received	147,500,000
Sales milestone for products developed unilaterally | Maximum
Revenue
Potential milestone payments to be received	$ 110,000,000

Revenue - Collaboration Agree_3

Revenue - Collaboration Agreement - The GSK Collaboration and License Agreement (Details) - GSK Collaboration And License Agreement	1 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($)	Dec. 31, 2019 USD ($)	Dec. 19, 2022 USD ($)	Dec. 19, 2022 GBP (£)
Revenue
Amount of development milestone achieved		$ 3,200,000
Milestone payments received	$ 4,200,000
Payment by GSK due to termination of collaboration | £				£ 5,000,000
Aggregate transaction price of the contract modification			$ 6,500,000
Payment on contract modification			(6,100,000)	£ 5,000,000
Amount of remaining deferred income under the collaboration that had not been recognized as revenue			$ 400,000

Financial instruments - Fair va

Financial instruments - Fair value of assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Marketable securities:
Assets classified as available for sale debt securities	$ 96,572	$ 219,632
Recurring basis
Marketable securities:
Assets classified as available for sale debt securities	96,572	219,632
Recurring basis | Level 1
Marketable securities:
Assets classified as available for sale debt securities	85,764	214,639
Recurring basis | Level 2
Marketable securities:
Assets classified as available for sale debt securities	10,808	4,993
Corporate debt securities | Recurring basis
Marketable securities:
Assets classified as cash equivalents	2,984
Assets classified as available for sale debt securities	85,764	214,639
Corporate debt securities | Recurring basis | Level 1
Marketable securities:
Assets classified as cash equivalents	2,984
Assets classified as available for sale debt securities	85,764	214,639
U.S. Treasury securities | Recurring basis
Marketable securities:
Assets classified as available for sale debt securities	5,954
U.S. Treasury securities | Recurring basis | Level 2
Marketable securities:
Assets classified as available for sale debt securities	5,954
Agency bond | Recurring basis
Marketable securities:
Assets classified as available for sale debt securities	4,854	4,993
Agency bond | Recurring basis | Level 2
Marketable securities:
Assets classified as available for sale debt securities	$ 4,854	$ 4,993

Financial instruments - Cash Eq

Financial instruments - Cash Equivalents and Short-term Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Financial instruments
Cash and cash equivalents	$ 108,033	$ 149,948
Marketable securities	96,572
Restricted cash	$ 1,569

Financial instruments - Collabo

Financial instruments - Collaboration and License Agreement (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) customer	Dec. 31, 2021 USD ($)
Financial instruments
Number of customers | customer	3
Trade receivables	$ 7,435,000	$ 752,000
Impairment losses	0
Amounts past due	$ 0

Financial instruments - Foreign

Financial instruments - Foreign Exchange Risk (Details)	Dec. 31, 2022	Dec. 31, 2021
Financial instruments
Exchange rate	1.21	1.35

Other current assets (Details)

Other current assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Other current assets
Corporate income taxes receivable	$ 30,162	$ 30,773
Prepayments	9,472	9,043
Clinical materials	1,279	746
VAT receivable	490	2,482
Other current assets	1,927	2,082
Total	$ 43,330	$ 45,126

Property, plant and equipment_3

Property, plant and equipment, net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, plant and equipment
Property, plant & equipment, gross	$ 92,104	$ 66,747
Less accumulated depreciation	(38,588)	(36,253)
Property, plant and equipment, net	53,516	30,494
Computer equipment
Property, plant and equipment
Property, plant & equipment, gross	3,818	3,692
Laboratory equipment
Property, plant and equipment
Property, plant & equipment, gross	30,173	28,002
Office equipment
Property, plant and equipment
Property, plant & equipment, gross	925	953
Leasehold improvements
Property, plant and equipment
Property, plant & equipment, gross	28,459	28,704
Assets under construction
Property, plant and equipment
Property, plant & equipment, gross	$ 28,729	$ 5,396

Property, plant and equipment_4

Property, plant and equipment, net - Depreciation Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, plant and equipment, net
Depreciation expense	$ 5,266,000	$ 5,630,000	$ 6,627,000

Intangible assets, net - Tabula

Intangible assets, net - Tabular Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Intangible assets, net
Intangible assets, gross	$ 5,118	$ 5,051
Less accumulated amortization	(4,676)	(4,051)
Intangible assets, net	442	1,000
Acquired software licenses
Intangible assets, net
Intangible assets, gross	4,930	4,842
Licensed IP rights - completed technology used in R&D
Intangible assets, net
Intangible assets, gross	$ 188	$ 209

Intangible assets, net - Amorti

Intangible assets, net - Amortization Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Intangible assets, net
Amortization expense	$ 809,000	$ 937,000	$ 967,000

Intangible assets, net - Aggreg

Intangible assets, net - Aggregate Amortization Expense (Details)	Dec. 31, 2022 USD ($)
Estimated aggregate amortization expense
Estimated amortization expense for 2023	$ 309,000
Estimated amortization expense for 2024	105,000
Estimated amortization expense for 2025	43,000
Estimated amortization expense for 2026	1,000
Estimated amortization expense for 2027	$ 1,000

Operating Leases (Details)

Operating Leases (Details) - USD ($)		12 Months Ended
	Mar. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Operating leases
Amount of increase (decrease) in obligation and right-of-use asset for operating lease following lease modification	$ 75,000
Operating lease cost		$ 4,367,000	$ 4,259,000
Short-term lease cost		389,000	419,000
Total		4,756,000	4,678,000
Operating cash outflows from operating leases		$ 3,746,000	$ 4,101,000
Weighted-average remaining lease term - operating leases		6 years 10 months 24 days	7 years 9 months 18 days
Weighted-average discount rate - operating leases		6.80%	6.80%

Operating Leases - Maturities (

Operating Leases - Maturities (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Maturities of operating lease liabilities
2023	$ 4,170
2024	3,953
2025	4,001
2026	4,055
2027	5,471
after 2027	7,324
Total lease payments	28,974
Less: Imputed interest	(5,897)
Present value of lease liability	$ 23,077

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued expenses and other current liabilities
Accrued clinical and development expenditure	$ 16,749	$ 13,436
Accrued employee expenses	8,232	11,758
Other accrued expenditure	4,079	4,388
Other	2,155	327
Total	$ 31,215	$ 29,909

Contingencies and commitments -

Contingencies and commitments - Capital Commitments (Details) - Capital commitments	Dec. 31, 2022 USD ($)
Contingencies and commitments
Committed amount	$ 2,459,000
Committed amount expected to be paid in one year	2,261,000
Committed amount expected to be paid in one to three years	$ 198,000

Contingencies and commitments_2

Contingencies and commitments - Clinical Trials and Contract Manufacturing Commitments (Details) - Clinical trials and contract manufacturing commitments - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Contingencies and commitments
Subcontract costs	$ 54,689,000	$ 46,469,000	$ 33,744,000
Other commitments, due within one year	10,662,000
Other commitments, due in one to three years	133,000
Other commitments, due in three to five years	133,000
Maximum
Contingencies and commitments
Other commitments	$ 10,928,000

Contingencies and commitments_3

Contingencies and commitments - MD Anderson Strategic Alliance (Details) - MD Anderson Strategic Alliance - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2017	Sep. 26, 2016
Contingencies and commitments
Upfront payment					$ 3,412,000
Milestone Payments		$ 454,000	$ 3,549,000	$ 2,326,000
Milestone met and paid in current period	$ 2,326,000
Minimum
Contingencies and commitments
Potential milestone payments						$ 19,644,000

Contingencies and commitments_4

Contingencies and commitments - Universal Cells Research, Collaboration and License Agreement and Co-development and Co-commercialization agreement (Details) - Collaboration and license agreement - Universal Cells, Inc. - USD ($)	1 Months Ended		12 Months Ended
	Feb. 29, 2016	Nov. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2022
Contingencies and commitments
Upfront license and start-up fees		$ 2,500,000
Milestone payments	$ 3,000,000		$ 200,000	$ 900,000
First milestone payment					$ 500,000
Second milestone payment					600,000
Third milestone payment					400,000
Maximum
Contingencies and commitments
Milestone payment accrued but not yet paid					$ 1,800,000

Contingencies and commitments_5

Contingencies and commitments - Astellas Collaboration Agreement (Details) - Astellas Collaboration Agreement. - Maximum $ in Thousands	Jan. 13, 2020 USD ($)
Contingencies and commitments
Milestone payments	$ 552,500
Development milestone per product developed unilaterally
Contingencies and commitments
Potential milestone payments	147,500
Sales milestone for products developed unilaterally
Contingencies and commitments
Potential milestone payments	$ 110,000

Contingencies and commitments_6

Contingencies and commitments - Noile-Immune Collaboration Agreement (Details) - License agreement - Noile Immune Biotech Inc. - USD ($)	Aug. 26, 2019	Dec. 31, 2022
Contingencies and commitments
Upfront license fees	$ 2,500,000
Maximum
Contingencies and commitments
Potential milestone payments		$ 312,000,000

Contingencies and commitments_7

Contingencies and commitments - Alpine Collaboration Agreement (Details) - Research and development - Alpine Immune Sciences Inc. - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2022	Dec. 31, 2020
Contingencies and commitments
Upfront license fees	$ 2,000,000		$ 2,000,000
Milestone payments		$ 1,000,000
Maximum
Contingencies and commitments
Potential milestone payments	$ 288,000,000

Contingencies and commitments_8

Contingencies and commitments - ThermoFisher License Agreement (Details) - License agreement - ThermoFisher - USD ($)		12 Months Ended
	Jun. 16, 2016	Dec. 31, 2012	Dec. 31, 2022
Contingencies and commitments
Upfront license fees		$ 1,000,000
Minimum Annual Royalties, Percentage of Prior Year Running Royalties			50%
Period of Supply Contract Agreement	5 years

Stockholders' equity - Ordinary

Stockholders' equity - Ordinary Shares (Details)	Dec. 31, 2022	May 14, 2021 GBP (£)
Stockholders' equity
Number of votes per share on a show of hands	1
Number of votes per share on a poll	1
Maximum aggregate nominal amount		£ 310,638
Maximum aggregate nominal amount of shares without offering to existing shareholders holding proportion		£ 310,638

Stockholders equity - Offerings

Stockholders equity - Offerings (Details) - USD ($)						12 Months Ended
	Apr. 08, 2022	Aug. 10, 2020	Jun. 04, 2020	Feb. 07, 2020	Jan. 24, 2020	Dec. 31, 2022	Dec. 31, 2021
Sales Agreement
Shareholders' equity
Remaining amount under the Sales Agreement							$ 197,360,000
Sales Agreement | Maximum
Shareholders' equity
Aggregate offering price of ADS shares under At The Market sales agreement		$ 200,000,000
2022 Sales Agreement
Shareholders' equity
Remaining amount under the Sales Agreement						$ 186,702,871
2022 Sales Agreement | Maximum
Shareholders' equity
Aggregate offering price of ADS shares under At The Market sales agreement	$ 200,000,000
Common stock
Shareholders' equity
Number of ordinary shares sold (in shares)						43,738,422	3,069,330
Common stock | Sales Agreement
Shareholders' equity
Number of ordinary shares sold (in shares)							3,069,330
Common stock | 2022 Sales Agreement
Shareholders' equity
Number of ordinary shares sold (in shares)						43,738,422
American Depository Shares (ADSs) | Sales Agreement
Shareholders' equity
Sold shares represented by American Depositary Shares (in shares)							511,555
Net proceeds							$ 2,529,000
American Depository Shares (ADSs) | 2022 Sales Agreement
Shareholders' equity
Sold shares represented by American Depositary Shares (in shares)						7,289,737
Net proceeds						$ 12,793,448
American Depository Shares (ADSs) | Underwritten public offering
Shareholders' equity
Sold shares represented by American Depositary Shares (in shares)			20,500,000		21,000,000
Issuance of shares represented by American Depositary Shares (in shares)			3,075,000	3,150,000
Net proceeds			$ 243,834,000		$ 90,554,000

Share-based compensation - Opti

Share-based compensation - Option Plans (Details)

12 Months Ended

Jul. 01, 2022

Jul. 01, 2021

Jul. 01, 2020

Jul. 02, 2019

Jul. 05, 2018

Jun. 22, 2018

Jul. 03, 2017

Nov. 28, 2016

Aug. 11, 2016

Jun. 23, 2016

Mar. 16, 2015 GBP (£) item

Dec. 31, 2022 shares

Share based compensation

Contractual term (in years)

10 years

Number of option schemes | item

3

RSU

Share based compensation

Exercise price | shares

0.001

Vesting percentage (as a percent)

25%

Vesting period (in years)

4 years

Contractual term (in years)

10 years

Scheme limit, grants as a percentage of fully diluted share capital of the Company immediately following the IPO (as a percent)

8%

Scheme limit, automatic increase percentage (as a percent)

4%

Options granted in January 2016 and March 2015

Share based compensation

Maximum value of option grants per participant | £

£ 30,000

Options granted in January 2016 and March 2015 | First anniversary

Share based compensation

Vesting percentage (as a percent)

25%

Options granted in January 2016 and March 2015 | Monthly installments over the following three years

Share based compensation

Vesting percentage (as a percent)

75%

Vesting period (in years)

3 years

Non-executive director | Options granted on June 23, 2016 | First anniversary

Share based compensation

Vesting percentage (as a percent)

25%

Vesting period (in years)

1 year

Non-executive director | Options granted on June 23, 2016 | Monthly installments over the following two years

Share based compensation

Vesting percentage (as a percent)

75%

Vesting period (in years)

2 years

Non-executive director | Options granted on August 11, 2016 | First anniversary

Share based compensation

Vesting percentage (as a percent)

100%

Vesting period (in years)

1 year

Non-executive director | Options granted on November 28, 2016 | First anniversary

Share based compensation

Vesting percentage (as a percent)

25%

Vesting period (in years)

1 year

Non-executive director | Options granted on November 28, 2016 | Monthly installments over the following two years

Share based compensation

Vesting percentage (as a percent)

75%

Vesting period (in years)

2 years

Non-executive director | Options granted on July 3, 2017 | First anniversary

Share based compensation

Vesting percentage (as a percent)

100%

Vesting period (in years)

1 year

Non-executive director | Options granted on June 22, 2018 | First anniversary

Share based compensation

Vesting percentage (as a percent)

100%

Vesting period (in years)

1 year

Non-executive director | Options granted in July 5, 2018 | First anniversary

Share based compensation

Vesting percentage (as a percent)

25%

Vesting period (in years)

1 year

Non-executive director | Options granted in July 5, 2018 | Monthly installments over the following two years

Share based compensation

Vesting percentage (as a percent)

75%

Vesting period (in years)

2 years

Non-executive director | Options granted in July 2, 2019 | First anniversary

Share based compensation

Vesting percentage (as a percent)

100%

Vesting period (in years)

1 year

Non-executive director | Options granted in July 1, 2020 | First anniversary

Share based compensation

Vesting percentage (as a percent)

100%

Vesting period (in years)

1 year

Non-executive director | Options granted in July 1, 2021 | First anniversary

Share based compensation

Vesting percentage (as a percent)

100%

Vesting period (in years)

1 year

Non-executive director | Options granted in July 1, 2022 | First anniversary

Share based compensation

Vesting percentage (as a percent)

100%

Vesting period (in years)

1 year

Share-based compensation - Shar

Share-based compensation - Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Total share-based compensation expense included in the consolidated statements of operations
Total share-based compensation expense	$ 18,240	$ 20,629	$ 10,414
Research and development
Total share-based compensation expense included in the consolidated statements of operations
Total share-based compensation expense	6,264	9,052	4,417
General and administrative
Total share-based compensation expense included in the consolidated statements of operations
Total share-based compensation expense	$ 11,976	$ 11,577	$ 5,997

Share based compensation - Unre

Share based compensation - Unrecognized Compensation Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Share based compensation
Unrecognized compensation cost	$ 14,899
Expected weighted-average cost recognition period (in years)	2 years 7 months 6 days

Share-based compensation - Op_2

Share-based compensation - Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Options granted on market value at grant date
Number of options over ordinary shares granted (in shares)	31,826,293	21,300,998	15,595,374
Weighted average fair value of ordinary shares options (in dollars per share)	$ 0.37	$ 0.70	$ 0.59
Options with nominal exercise price
Number of additional options with a nominal exercise price granted	24,248,424	17,765,778	8,282,152
Weighted average fair value of options with a nominal exercise price	$ 0.51	$ 0.97	$ 0.85

Share based compensation - Opti

Share based compensation - Option Activity (Details) - GBP (£) £ / shares in Units, £ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Options
Exercised (in shares)	(5,823,534)	(5,723,646)	(11,401,390)
Stock options
Options
Outstanding at the beginning of the period (in shares)	114,915,438
Granted (in shares)	56,074,717
Exercised (in shares)	(5,823,534)
Expired (in shares)	(3,238,371)
Forfeited (in shares)	(9,389,161)
Outstanding at the end of the period (in shares)	152,539,089	114,915,438
Weighted Average Exercise Price Per Option
Outstanding at the beginning of the period (in dollars per share)	£ 0.52
Granted (in dollars per share)	0.21
Exercise price (in dollars per share)	0.01
Expired (in dollars per share)	0.69
Forfeited (in dollars per share)	0.21
Outstanding at the end of the period (in dollars per share)	£ 0.44	£ 0.52
Additional disclosures
Outstanding - Average Remaining Contractual Term (Years)	7 years
Outstanding - Aggregate Intrinsic Value	£ 8,082
Exercisable - Options	75,064,373
Exercisable - Weighted Average Exercise Price Per Option	£ 0.64
Exercisable - Average Remaining Contractual Term (Years)	5 years 3 months 18 days
Exercisable - Aggregate Intrinsic Value	£ 1,077
Options with nominal exercise price
Options
Outstanding at the end of the period (in shares)	40,061,626
Additional disclosures
Exercisable - Options	5,295,014
Options granted on market value at grant date
Options
Outstanding at the beginning of the period (in shares)	87,387,314
Granted (in shares)	31,826,293	21,300,998	15,595,374
Exercised (in shares)	(318,222)
Expired (in shares)	(3,077,532)
Forfeited (in shares)	(3,340,390)
Outstanding at the end of the period (in shares)	112,477,463	87,387,314
Weighted Average Exercise Price Per Option
Outstanding at the beginning of the period (in dollars per share)	£ 0.68
Granted (in dollars per share)	0.37
Exercise price (in dollars per share)	0.11
Expired (in dollars per share)	0.72
Forfeited (in dollars per share)	0.59
Outstanding at the end of the period (in dollars per share)	£ 0.60	£ 0.68
Additional disclosures
Outstanding - Average Remaining Contractual Term (Years)	6 years 6 months
Outstanding - Aggregate Intrinsic Value	£ 68
Exercisable - Options	69,769,359
Exercisable - Weighted Average Exercise Price Per Option	£ 0.68
Exercisable - Average Remaining Contractual Term (Years)	5 years 2 months 12 days
Exercisable - Aggregate Intrinsic Value	£ 18
RSU
Options
Outstanding at the beginning of the period (in shares)	27,528,124
Granted (in shares)	24,248,424
Exercised (in shares)	(5,505,312)
Expired (in shares)	(160,839)
Forfeited (in shares)	(6,048,771)
Outstanding at the end of the period (in shares)		27,528,124
Additional disclosures
Outstanding - Average Remaining Contractual Term (Years)	8 years 4 months 24 days	8 years 6 months
Outstanding - Aggregate Intrinsic Value	£ 8,014	£ 12,720
Exercisable - Average Remaining Contractual Term (Years)	6 years 7 months 6 days
Exercisable - Aggregate Intrinsic Value	£ 1,059

Share based compensation - Op_2

Share based compensation - Options Exercised (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share based compensation
Option Exercised (in shares)	5,823,534	5,723,646	11,401,390
Intrinsic value of stock options exercised	$ 2,368,000	$ 4,321,000	$ 8,195,000
Proceeds from exercise of stock options	50,000	759,000	5,663,000
Tax benefit from stock option exercises	$ 488,000	$ 862,000	$ 1,265,000

Share based compensation - Stoc

Share based compensation - Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2022 £ / shares shares
Share-based compensation
Outstanding - Total Share Options | shares	152,539,089
Outstanding - Weighted-Average Remaining Contractual Life	7 years
Outstanding - Weighted Average Exercise Price	£ 0.44
Exercisable - Total Share Options | shares	75,064,373
Exercisable - Weighted-Average Exercise Price	£ 0.64
Exercise Price $0
Share-based compensation
Exercise price | shares	0
Outstanding - Total Share Options | shares	40,061,626
Outstanding - Weighted-Average Remaining Contractual Life	8 years 4 months 24 days
Outstanding - Weighted Average Exercise Price	£ 0
Exercisable - Total Share Options | shares	5,295,014
Exercisable - Weighted-Average Exercise Price	£ 0
Exercise Price $0.01 - $0.25
Share-based compensation
Exercise Price, Lower Range Limit	0.01
Exercise Price, Upper Range Limit	£ 0.25
Outstanding - Total Share Options | shares	8,412,475
Outstanding - Weighted-Average Remaining Contractual Life	9 years 1 month 6 days
Outstanding - Weighted Average Exercise Price	£ 0.22
Exercisable - Total Share Options | shares	738,325
Exercisable - Weighted-Average Exercise Price	£ 0.19
Exercise Price $0.26 - $0.50
Share-based compensation
Exercise Price, Lower Range Limit	0.26
Exercise Price, Upper Range Limit	£ 0.50
Outstanding - Total Share Options | shares	38,339,879
Outstanding - Weighted-Average Remaining Contractual Life	6 years 10 months 24 days
Outstanding - Weighted Average Exercise Price	£ 0.41
Exercisable - Total Share Options | shares	14,287,927
Exercisable - Weighted-Average Exercise Price	£ 0.42
Exercise Price $0.51 - $0.75
Share-based compensation
Exercise Price, Lower Range Limit	0.51
Exercise Price, Upper Range Limit	£ 0.75
Outstanding - Total Share Options | shares	36,255,404
Outstanding - Weighted-Average Remaining Contractual Life	5 years 10 months 24 days
Outstanding - Weighted Average Exercise Price	£ 0.60
Exercisable - Total Share Options | shares	32,291,011
Exercisable - Weighted-Average Exercise Price	£ 0.61
Exercise Price $0.76 - $1.00
Share-based compensation
Exercise Price, Lower Range Limit	0.76
Exercise Price, Upper Range Limit	£ 1
Outstanding - Total Share Options | shares	24,103,880
Outstanding - Weighted-Average Remaining Contractual Life	6 years 1 month 6 days
Outstanding - Weighted Average Exercise Price	£ 0.84
Exercisable - Total Share Options | shares	17,446,630
Exercisable - Weighted-Average Exercise Price	£ 0.87
Exercise Price $1.01 - $1.50
Share-based compensation
Exercise Price, Lower Range Limit	1.01
Exercise Price, Upper Range Limit	£ 1.50
Outstanding - Total Share Options | shares	3,974,824
Outstanding - Weighted-Average Remaining Contractual Life	6 years 3 months 18 days
Outstanding - Weighted Average Exercise Price	£ 1.25
Exercisable - Total Share Options | shares	3,614,465
Exercisable - Weighted-Average Exercise Price	£ 1.26
Exercise Price $1.51 - $2.00
Share-based compensation
Exercise Price, Lower Range Limit	1.51
Exercise Price, Upper Range Limit	£ 2
Outstanding - Total Share Options | shares	1,391,001
Outstanding - Weighted-Average Remaining Contractual Life	4 years 8 months 12 days
Outstanding - Weighted Average Exercise Price	£ 1.70
Exercisable - Total Share Options | shares	1,391,001
Exercisable - Weighted-Average Exercise Price	£ 1.70

Share-based compensation - Fair

Share-based compensation - Fair Value Assumptions (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assumptions used to estimate the fair values of the share options granted using the Black-Scholes option-pricing model
Expected term (in years)	5 years	5 years	5 years
Expected dividend yield (as a percent)	0%	0%	0%
Minimum
Assumptions used to estimate the fair values of the share options granted using the Black-Scholes option-pricing model
Expected volatility (as a percent)	99%	98%	90%
Risk free rate (as a percent)	0.94%	0%	0%
Maximum
Assumptions used to estimate the fair values of the share options granted using the Black-Scholes option-pricing model
Expected volatility (as a percent)	101%	100%	99%
Risk free rate (as a percent)	3.90%	0.61%	0.42%

Income taxes - Loss before Inco

Income taxes - Loss before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income taxes
Loss before income tax expense	$ (162,959)	$ (157,299)	$ (129,930)
U.S.
Income taxes
Loss before income tax expense	(3,245)	1,625	(1,359)
U.K.
Income taxes
Loss before income tax expense	$ (159,714)	$ (158,924)	$ (128,571)

Income taxes - Components of In

Income taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
United States:
Federal	$ 2,492	$ 791	$ 162
State and local	5
Total current tax expense	2,497	791	162
United States:
Total income tax expense	$ 2,497	$ 791	$ 162

Income taxes - Reconciliation o

Income taxes - Reconciliation of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax liabilities
Property, plant and equipment	$ (3,486)	$ (922)
Operating lease right-of-use assets	(1,529)	(1,757)
Other	(251)	(238)
Total	(5,266)	(2,917)
Deferred tax assets
Share-based compensation expense	16,963	15,584
Intangibles	1,324	2,401
Operating lease liabilities	1,958	2,143
Net operating loss and expenditure credit carryforwards	136,592	114,972
Capitalized research and development expenditure	8,409
Other	532	260
Total	165,778	135,360
Valuation allowance	(160,512)	(132,443)	$ (82,398)
Deferred tax assets, net	$ 5,266	$ 2,917

Income taxes - Change in Valuat

Income taxes - Change in Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Valuation allowance, beginning	$ 132,443	$ 82,398
Foreign currency translation adjustments	(12,222)	(1,513)
Net change in the valuation allowance	28,069	50,045
Valuation allowance, ending	160,512	132,443
Net loss
Increase in valuation allowance	30,455	50,046
Other comprehensive loss
Increase in valuation allowance	$ 9,836	$ 1,512

Income taxes - Reconciliation_2

Income taxes - Reconciliation of Effective Tax Rate (Details) - His Majesty's Revenue and Customs (HMRC)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income taxes
UK tax rate	19%	19%	19%
Tax-exempt reimbursable tax credits included within pretax Research and development expense	3.60%	4.10%	2.80%
Surrender of R&D expenditures for R&D tax credit refund	(10.50%)	(10.30%)	(8.40%)
Expenses not deductible	(0.30%)	(0.20%)	(1.40%)
Change in valuation allowances	(18.80%)	(31.80%)	(17.80%)
Change in tax rates		13.70%	4.10%
Difference in tax rates	5.50%	4.40%
R&D tax credits generated	2.10%	2%	1.80%
Other	(2.10%)	(1.40%)	(0.10%)
Effective income tax rate	(1.50%)	(0.50%)	0%

Income taxes - Change in Tax Ra

Income taxes - Change in Tax Rate (Details)		12 Months Ended
	Apr. 01, 2023	Dec. 31, 2023	Dec. 31, 2022 GBP (£)	Dec. 31, 2021 USD ($)	Dec. 31, 2020	Dec. 31, 2022 USD ($)
Income taxes
Increase in net deferred tax asset and corresponding valuation allowance				$ 21,481,000
U.K.
Income taxes
Tax rate (as a percent)	19%		19%	19%	19%
Difference in tax rates			25%
U.K. | Forecast
Income taxes
Tax rate (as a percent)	25%	25%
U.S.
Income taxes
Difference in tax rates			21%	21%	21%
His Majesty's Revenue and Customs (HMRC)
Income taxes
Tax rate (as a percent)			19%	19%	19%
Operating Loss Carryforwards						$ 526,784,000
Expenditure credit carryforward						$ 760,000
Annual allowance | £			£ 5,000,000
Percentage on taxable profit						50%
Internal Revenue Service (IRS)
Income taxes
Tax credit carryforwards						$ 4,136,000
Tax credit carried forward period			20 years

Income taxes - Unrecognized Tax

Income taxes - Unrecognized Tax Benefits (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Income taxes
Unrecognized tax benefits	$ 0

Geographic information - Operat

Geographic information - Operations by Geographic Area - Long-lived Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Operations by Geographic Area
Long-lived assets	$ 71,535	$ 51,369
U.K.
Operations by Geographic Area
Long-lived assets	42,387	29,701
U.S.
Operations by Geographic Area
Long-lived assets	$ 29,148	$ 21,668

Geographic information - Major

Geographic information - Major Customers (Details) - Revenues - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2022
Astellas Pharma Inc.
Major Customers
Concentration risk (as a percentage)	21%
Genentech, Inc.
Major Customers
Concentration risk (as a percentage)	50%
GSK Collaboration And License Agreement
Major Customers
Concentration risk (as a percentage)	29%

Restructuring programme (Detail

Restructuring programme (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Restructuring programme
Restructuring and Related Cost, Cost Incurred to Date	$ 2,285
Remaining amount expected to be incurred in future periods	947
Total amount expected to be incurred	$ 3,232
Minimum
Restructuring programme
Percent of headcount reduction	25%
Maximum
Restructuring programme
Percent of headcount reduction	30%
General and administrative expenses
Restructuring programme
Total provision	$ 2,285
Contractual termination benefits
Restructuring programme
Restructuring and Related Cost, Cost Incurred to Date	1,171
Total amount expected to be incurred	1,171
Contractual termination benefits | General and administrative expenses
Restructuring programme
Total provision	1,171
One-time employee termination benefits
Restructuring programme
Restructuring and Related Cost, Cost Incurred to Date	1,114
Remaining amount expected to be incurred in future periods	947
Total amount expected to be incurred	2,061
One-time employee termination benefits | General and administrative expenses
Restructuring programme
Total provision	$ 1,114

Subsequent events (Details)

Subsequent events (Details) - USD ($)	Mar. 06, 2023	Dec. 31, 2022
Subsequent events. | TCR2 Therapeutics
Ownership percentage	25%
Subsequent events. | Adaptimmune
Ownership percentage	75%
Astellas Collaboration Agreement
Amount of remaining deferred income under the collaboration that had not been recognized as revenue		$ 43,070,000
Astellas Collaboration Agreement | Subsequent events.
Amount of termination penalties in connection with the termination.	$ 0