COMPASS PATHWAYS PLC, 10-Q filed on 11/4/2025
Quarterly Report
v3.25.3
Cover - shares
 9 Months Ended
Sep. 30, 2025
Oct. 30, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2025  
Document Transition Report false  
Entity File Number 001-39522  
Entity Registrant Name COMPASS Pathways plc  
Entity Incorporation, State or Country Code X0  
Entity Address, Address Line One 33 Broadwick Street  
Entity Address, City or Town London  
Entity Address, Postal Zip Code W1F 0DQ  
Entity Address, Country GB  
City Area Code 716  
Local Phone Number 676-6461  
Title of 12(b) Security American Depositary Shares, each representing one ordinary share, par value of £0.008 per share  
Trading Symbol CMPS  
Security Exchange Name NASDAQ  
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  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   96,017,044
Entity Central Index Key 0001816590  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
v3.25.3
Condensed Consolidated Balance Sheets - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
CURRENT ASSETS:    
Cash and cash equivalents $ 185,937 $ 165,081
Restricted cash 379 389
Prepaid expenses and other current assets 56,072 35,821
Total current assets 242,388 201,291
NON-CURRENT ASSETS:    
Operating lease right-of-use assets 3,931 2,006
Deferred tax assets 4,527 3,774
Long-term prepaid expenses and other assets 4,761 6,595
Total assets 255,607 213,666
CURRENT LIABILITIES:    
Accounts payable 5,246 12,283
Accrued expenses and other liabilities 12,023 14,495
Debt, current portion 12,669 5,513
Operating lease liabilities - current 1,949 1,725
Warrant liabilities 165,563 0
Total current liabilities 197,450 34,016
NON-CURRENT LIABILITIES:    
Debt, non-current portion 18,600 24,652
Operating lease liabilities - non-current 1,966 303
Total liabilities 218,016 58,971
Commitments and contingencies (Note 9)
SHAREHOLDERS' EQUITY:    
Ordinary shares, £0.008 par value; 96,002,044 and 68,552,215 shares authorized, issued and outstanding at September 30, 2025 and December 31, 2024, respectively 973 702
Additional paid-in capital 780,521 704,919
Accumulated other comprehensive loss (15,187) (16,194)
Accumulated deficit (728,716) (534,732)
Total shareholders' equity 37,591 154,695
Total liabilities and shareholders' equity $ 255,607 $ 213,666
v3.25.3
Condensed Consolidated Balance Sheets (Parenthetical) - £ / shares
Sep. 30, 2025
Dec. 31, 2024
Common stock, authorized (in shares) 96,002,044 68,552,215
Common stock, issued (in shares) 96,002,044 68,552,215
Common stock, outstanding (in shares) 96,002,044 68,552,215
Ordinary shares    
Common stock, par value (in GBP per share) £ 0.008 £ 0.008
v3.25.3
Condensed Statements of Operations and Comprehensive Loss - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
OPERATING EXPENSES:        
Research and development $ 27,325 $ 32,928 $ 88,530 $ 86,898
General and administrative 13,211 14,968 44,555 42,893
Total operating expenses 40,536 47,896 133,085 129,791
Loss from operations: (40,536) (47,896) (133,085) (129,791)
OTHER INCOME (EXPENSE), NET:        
Fair value change of warrant liabilities (101,318) 0 (84,398) 0
Benefit from R&D tax credit 3,924 4,084 16,659 10,894
Interest income 1,588 1,977 5,872 6,645
Foreign exchange (losses) gains (883) 4,452 3,599 3,894
Interest expense (1,105) (1,137) (3,380) (3,347)
Other income 383 191 1,010 486
Total other income, net (97,411) 9,567 (60,638) 18,572
Loss before income taxes (137,947) (38,329) (193,723) (111,219)
Income tax benefit (expense) 230 (173) (261) (571)
Net loss $ (137,717) $ (38,502) $ (193,984) $ (111,790)
Net loss per share attributable to ordinary shareholders - basic (in dollars per share) $ (1.44) $ (0.56) $ (2.09) $ (1.67)
Net loss per share attributable to ordinary shareholders - diluted (in dollars per share) $ (1.44) $ (0.56) $ (2.09) $ (1.67)
Weighted average ordinary shares outstanding - basic (in shares) 95,337,993 68,395,343 92,646,458 67,001,326
Weighted average ordinary shares outstanding - diluted (in shares) 95,337,993 68,395,343 92,646,458 67,001,326
Other comprehensive loss:        
Foreign exchange translation adjustment $ (605) $ 339 $ 1,007 $ 384
Comprehensive loss $ (138,322) $ (38,163) $ (192,977) $ (111,406)
v3.25.3
Condensed Consolidated Statements of Shareholders’ Equity - USD ($)
$ in Thousands
Total
At-The-Market Offering
ADDITIONAL PAID-IN CAPITAL
ADDITIONAL PAID-IN CAPITAL
At-The-Market Offering
ACCUMULATED OTHER COMPREHENSIVE (LOSS)/INCOME
ACCUMULATED DEFICIT
Ordinary shares
COMMON STOCK
Ordinary shares
COMMON STOCK
At-The-Market Offering
Beginning balance (in shares) at Dec. 31, 2023             61,943,471  
Beginning balance at Dec. 31, 2023 $ 225,744   $ 621,645   $ (16,926) $ (379,610) $ 635  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Exercise of share options (in shares)             86,510  
Exercise of share options 220   219       $ 1  
Issuance of ordinary shares, net of issuance costs (in shares)               2,509,798
Issuance of ordinary shares, net of issuance costs   $ 26,219   $ 26,194       $ 25
Issuance of ordinary shares to settle vested restricted stock units (in shares)             50,705  
Issuance of ordinary shares to settle warrants exercised (in shares)             3,752,050  
Issuance of ordinary shares to settle warrants exercised 37,258   37,220       $ 38  
Shares tendered for withholding taxes (185)   (185)          
Share-based compensation expense 5,129   5,129          
Unrealized gain (loss) on foreign currency translation (36)       (36)      
Net loss (35,187)         (35,187)    
Ending balance (in shares) at Mar. 31, 2024             68,342,534  
Ending balance at Mar. 31, 2024 259,162   690,222   (16,962) (414,797) $ 699  
Beginning balance (in shares) at Dec. 31, 2023             61,943,471  
Beginning balance at Dec. 31, 2023 225,744   621,645   (16,926) (379,610) $ 635  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Unrealized gain (loss) on foreign currency translation 384              
Net loss (111,790)              
Ending balance (in shares) at Sep. 30, 2024             68,409,068  
Ending balance at Sep. 30, 2024 193,030   700,273   (16,542) (491,400) $ 699  
Beginning balance (in shares) at Mar. 31, 2024             68,342,534  
Beginning balance at Mar. 31, 2024 259,162   690,222   (16,962) (414,797) $ 699  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Exercise of share options (in shares)             3,845  
Issuance of ordinary shares to settle vested restricted stock units (in shares)             4,438  
Vesting of equity awards under the employee purchase plan ( in shares)             36,652  
Vesting of equity awards under the employee purchase plan 210   210          
Share-based compensation expense 4,921   4,921          
Unrealized gain (loss) on foreign currency translation 81       81      
Net loss (38,101)         (38,101)    
Ending balance (in shares) at Jun. 30, 2024             68,387,469  
Ending balance at Jun. 30, 2024 226,273   695,353   (16,881) (452,898) $ 699  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Exercise of share options (in shares)             13,083  
Issuance of ordinary shares to settle vested restricted stock units (in shares)             8,516  
Shares tendered for withholding taxes (53)   (53)          
Share-based compensation expense 4,973   4,973          
Unrealized gain (loss) on foreign currency translation 339       339      
Net loss (38,502)         (38,502)    
Ending balance (in shares) at Sep. 30, 2024             68,409,068  
Ending balance at Sep. 30, 2024 $ 193,030   700,273   (16,542) (491,400) $ 699  
Beginning balance (in shares) at Dec. 31, 2024 68,552,215           68,552,215  
Beginning balance at Dec. 31, 2024 $ 154,695   704,919   (16,194) (534,732) $ 702  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Exercise of share options (in shares)             164,422  
Exercise of share options 2           $ 2  
Issuance of ordinary shares, net of issuance costs (in shares)               24,014,728
Issuance of ordinary shares, net of issuance costs   $ 54,816   $ 54,583       $ 233
Issuance of ordinary shares to settle vested restricted stock units (in shares)             116,961  
Issuance of ordinary shares to settle vested restricted stock units 0   (1)       $ 1  
Share-based compensation expense 3,935   3,935          
Unrealized gain (loss) on foreign currency translation (117)       (117)      
Net loss (17,864)         (17,864)    
Ending balance (in shares) at Mar. 31, 2025             92,848,326  
Ending balance at Mar. 31, 2025 $ 195,467   763,436   (16,311) (552,596) $ 938  
Beginning balance (in shares) at Dec. 31, 2024 68,552,215           68,552,215  
Beginning balance at Dec. 31, 2024 $ 154,695   704,919   (16,194) (534,732) $ 702  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Unrealized gain (loss) on foreign currency translation 1,007              
Net loss $ (193,984)              
Ending balance (in shares) at Sep. 30, 2025 96,002,044           96,002,044  
Ending balance at Sep. 30, 2025 $ 37,591   780,521   (15,187) (728,716) $ 973  
Beginning balance (in shares) at Mar. 31, 2025             92,848,326  
Beginning balance at Mar. 31, 2025 195,467   763,436   (16,311) (552,596) $ 938  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Exercise of share options (in shares)             682,682  
Exercise of share options 9   2       $ 7  
Issuance of ordinary shares to settle vested restricted stock units (in shares)             9,375  
Vesting of equity awards under the employee purchase plan ( in shares)             45,965  
Vesting of equity awards under the employee purchase plan 157   156       $ 1  
Share-based compensation expense 3,596   3,596          
Unrealized gain (loss) on foreign currency translation 1,729       1,729      
Net loss (38,403)         (38,403)    
Ending balance (in shares) at Jun. 30, 2025             93,586,348  
Ending balance at Jun. 30, 2025 162,555   767,190   (14,582) (590,999) $ 946  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Exercise of share options (in shares)             44,121  
Issuance of ordinary shares to settle vested restricted stock units (in shares)             26,909  
Issuance of ordinary shares to settle warrants exercised (in shares)             2,344,666  
Issuance of ordinary shares to settle warrants exercised 10,151   10,124       $ 27  
Share-based compensation expense 3,207   3,207          
Unrealized gain (loss) on foreign currency translation (605)       (605)      
Net loss $ (137,717)         (137,717)    
Ending balance (in shares) at Sep. 30, 2025 96,002,044           96,002,044  
Ending balance at Sep. 30, 2025 $ 37,591   $ 780,521   $ (15,187) $ (728,716) $ 973  
v3.25.3
Condensed Consolidated Statements of Shareholders’ Equity (Parenthetical) - £ / shares
Sep. 30, 2025
Dec. 31, 2024
Ordinary shares    
Common stock, par value (in GBP per share) £ 0.008 £ 0.008
v3.25.3
Condensed Consolidated Statements of Cash Flows - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
CASH FLOWS FROM OPERATING ACTIVITIES:    
Net loss $ (193,984) $ (111,790)
Adjustments to reconcile net loss to net cash used in operating activities    
Depreciation 210 183
Non-cash interest 1,104 1,037
Non-cash loss on foreign currency remeasurement (682) (802)
Non-cash share-based compensation 10,738 15,023
Non-cash lease expenses 1,114 1,687
Transaction costs allocated to warrants 5,778 0
Fair value change of warrant liabilities 84,398 0
Changes in operating assets and liabilities    
Prepaid expenses and other current assets (17,364) 14,479
Deferred and prepaid tax assets (753) 46
Other assets 2,035 643
Operating lease liabilities (1,150) (1,659)
Accounts payable (7,719) 1,947
Accrued expenses and other liabilities (3,177) 1,777
Net cash used in operating activities (119,452) (77,429)
CASH FLOWS FROM FINANCING ACTIVITIES:    
Proceeds from issuance of ordinary shares and Pre-funded Warrants, net of issuance costs 140,357 26,219
Proceeds from the exercise of warrants 0 37,258
Payments of withholding tax on stock award 0 (238)
Proceeds from issuance of shares under the employee share purchase plan 157 210
Proceeds from exercise of options 11 220
Net cash provided by financing activities 140,525 63,669
Effect of exchange rate changes on cash, cash equivalents and restricted cash (227) 464
Net increase in cash, cash equivalents and restricted cash 20,846 (13,296)
Cash, cash equivalents and restricted cash, beginning of the period 165,470 220,638
Cash, cash equivalents and restricted cash, end of the period 186,316 207,342
Reconciliation of the cash, cash equivalents and restricted cash    
Cash and cash equivalents 185,937 206,953
Restricted cash 379 389
Total cash, cash equivalents and restricted cash $ 186,316 $ 207,342
v3.25.3
Nature of Business
 9 Months Ended
Sep. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Nature of Business Nature of Business
Compass Pathways plc, or the Company, is a biotechnology company dedicated to accelerating patient access to evidence-based innovation in mental health. The Company is developing its investigational COMP360 psilocybin treatment through late-stage clinical trials in Europe and North America for patients with treatment-resistant depression.
The Company is subject to risks and uncertainties common to clinical stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary intellectual property and technology, compliance with government regulations and the ability to secure additional capital to fund operations. The therapeutic candidate currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s therapeutic development efforts are successful, it is uncertain when, if ever, the Company will realize revenue from sales.
The Company has funded its operations with proceeds from the sale of its ordinary shares, American Depository Shares, or ADSs, including in its offerings pursuant to its at-the-market, or ATM, offering program, proceeds from a loan agreement with Hercules Capital, Inc., and proceeds from a private placement transaction, or the PIPE. The Company was party to a Sales Agreement for its ATM offering program, dated October 8, 2021, with TD Securities (USA) LLC, or TD Cowen, under which the Company was able to issue and sell from time to time up to $150.0 million of its ADSs, each representing one ordinary share, through TD Cowen as the sales agent. Pursuant to the Sales Agreement dated October 8, 2021, through February 27, 2025, the Company sold 5,491,836 ADSs under the Company’s ATM offering program, resulting in $54.8 million in net proceeds. On February 27, 2025, the Company entered into a new Sales Agreement to govern the Company’s ATM offering program with TD Cowen, or the Sales Agreement, under which the Company may issue and sell from time to time up to $150.0 million of our ADSs, subject to the terms of the Sales Agreement. Sales of its ADSs, if any, will generally be made at market prices. To date, the Company has not sold any ADSs under this Sales Agreement.
On June 30, 2023, the Company entered into a Loan Agreement with Hercules, which provided for aggregate maximum borrowings of up to $50.0 million, including a term loan of $30.0 million, which was funded on June 30, 2023. On August 16, 2023, the Company entered into a Securities Purchase Agreement, pursuant to which the Company agreed to sell and issue in a private placement transaction (i) 16,076,750 ADSs and (ii) PIPE Warrants to purchase up to 16,076,750 ADSs, at a purchase price of approximately $7.78 per ADS and accompanying PIPE Warrant to purchase one ADS. Each PIPE Warrant has an exercise price of $9.93 per ADS and is exercisable for a three-year period beginning in February 2024. The PIPE Warrants may be exercised on a cashless basis if there is no effective registration statement registering the shares underlying the PIPE Warrants. Through September 30, 2025, PIPE Warrants were exercised for 3,752,050 ADS, resulting in $37.3 million in exercise proceeds. The Company will receive up to an additional approximately $122.4 million in gross proceeds if the PIPE Warrants are fully exercised for cash. During the three months ended September 30, 2025, no PIPE warrants were exercised.
In January 2025, the Company issued and sold (i) 24,014,728 American Depositary Shares, each representing one ordinary share, nominal value £0.008 each, of the Company and accompanying warrants to purchase up to 24,014,728 ADSs, and (ii) in lieu of ADSs, to certain investors, Pre-funded Warrants to purchase up to 11,044,720 ADSs and accompanying 2025 ADS Warrants to purchase up to 11,044,720 ADSs. The offering price was $4.2750 per ADS and accompanying 2025 ADS Warrant, and $4.2649 per Pre-funded Warrant and accompanying 2025 ADS Warrant. The Pre-funded Warrants have an exercise price of $0.0001 per ADS and are exercisable immediately. The Pre-funded Warrants expire when exercised in full. The 2025 ADS Warrants have an exercise price of $5.7960 per ADS and are exercisable following a specified data milestone. The 2025 ADS Warrants will expire three years after such warrants become exercisable. Once the ADS Warrants become exercisable, the Company may force the exercise of the 2025 ADS Warrants (by way of cash or cashless exercise, at the Company’s option), in whole or in part, by delivering a notice of forced exercise to the holders, provided that the closing price for the Company’s ADSs on Nasdaq exceeded the warrant exercise price of $5.7960 for the three consecutive trading days
prior to the date on which the notice of forced exercise is delivered. During the three months ended September 30, 2025, 2,344,720 Pre-funded warrants were exercised.
The Company has incurred recurring losses since its inception, including net losses of $194.0 million and $111.8 million for the nine months ended September 30, 2025 and 2024, respectively. In addition, as of September 30, 2025, the Company had an accumulated deficit of $728.7 million. The Company expects to continue to generate operating losses for the foreseeable future. The Company believes the cash and cash equivalents on hand as of September 30, 2025 of $185.9 million will be sufficient to fund its operating expenses and capital expenditure requirements for at least the next twelve months from the date of issuance of these condensed consolidated financial statements. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations. The Company’s inability to raise capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies. There can be no assurance that the current operating plan will be achieved or that additional funding will be available on terms acceptable to the Company, or at all. The Company may raise additional capital through a combination of equity offerings, debt financings, collaborations, and other strategic transactions, including marketing, distribution or licensing arrangements. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial conditions.
Market volatility, geopolitical tensions or instability (including from the effects of announced or future tariff increases), geopolitical conflict (such as the war between Ukraine and Russia and conflict in the Middle East), fluctuating inflation and interest rates and the related impact on U.S., UK and global economies, instability in the banking system, the risk of an economic slowdown or recession in the U.S., significant changes in U.S. policies or regulatory environment or the disruption to U.S. government agencies (whether from the continued government shutdown or reduced resources) or other factors could adversely impact the Company’s operations, financial results and ability to raise additional funding.
v3.25.3
Summary of Significant Accounting Policies
 9 Months Ended
Sep. 30, 2025
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Basis of Presentation
The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or U.S. GAAP. The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements as of and for the year ended December 31, 2024, and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, necessary for the fair statement of the Company’s financial position for the reported periods.
The results of the Company’s operations for any interim period are not necessarily indicative of the results of the Company’s operations for any other interim period or for a full fiscal year. These interim financial statements should be read in conjunction with the audited consolidated financial statements as of and for the year ended December 31, 2024, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the SEC, on February 27, 2025. The condensed consolidated balance sheet at December 31, 2024, was derived from audited annual consolidated financial statements but does not contain all of the footnote disclosures from the annual financial statements.
Principles of Consolidation
The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated on consolidation.
Significant Accounting Policies
The Company’s significant accounting policies are described in Note 2 of the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024.
Use of Estimates
The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of income and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, warrant liabilities. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ materially from those estimates.
Recently Issued Accounting Pronouncements
In December 2023, the FASB issued ASU 2023-09 - Income Taxes (Topic 740): Improvements to Income Tax Disclosures, designed to improve income tax disclosure requirements, primarily through increased disaggregation disclosures within the effective tax rate reconciliation as well as enhanced disclosures on income taxes paid. The guidance is effective for all fiscal years beginning after December 15, 2024. The new standard can be adopted on a prospective basis with an option to be adopted retrospectively and early adoption is permitted. We are currently evaluating this guidance to determine its impact on the Company’s year-end consolidated financial statement disclosures.
In November 2024, the FASB issued ASU 2024-03 - Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, designed to improve disclosures, primarily through increased expense disaggregation. Additionally, in January 2025, the FASB issued ASU 2025-01 to clarify the effective date of ASU 2024-03. The guidance is effective for all fiscal years beginning after December 15, 2026, and interim reporting periods within annual reporting periods beginning after December 15, 2027. The new standard can be adopted on a prospective basis with an option to be adopted retrospectively and early adoption is permitted. The Company is not early adopting the standard. We are currently evaluating this guidance to determine its impact on the Company’s consolidated financial statement disclosures.
One Big Beautiful Bill Act
On July 4, 2025, the One Big Beautiful Bill Act ("OBBBA") was signed into law. The OBBBA introduced multiple U.S. federal income tax changes such as deductibility of domestic research and development expenses, deductibility on certain property additions and limitations on interest expense deduction. The Company has assessed the legislation, and believes the impact of these provisions on our consolidated financial statements will not be material.
v3.25.3
Prepaid Expenses and Other Current Assets
 9 Months Ended
Sep. 30, 2025
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]  
Prepaid Expenses and Other Current Assets Prepaid Expenses and Other Current Assets
Prepaid expenses and other current assets consisted of the following (in thousands):
September 30,December 31,
20252024
UK R&D tax credit
$39,309 $20,712 
Prepaid research and development13,011 11,332 
VAT recoverable998 1,109 
Other current assets2,754 2,668 
$56,072 $35,821 
The Company was uncertain whether it would meet the R&D intensity condition and be eligible for the enhanced effective rate for its tax submission relating to the year ended December 31, 2023. The Company sought clarity from HMRC in the form of a non-statutory clearance and received a positive response in April 2025. The Company filed a resubmission claim relating to the year ended December 31, 2023 at the enhanced rate, which resulted in an increase in its R&D tax relief claim of $4.1 million.
v3.25.3
Debt
 9 Months Ended
Sep. 30, 2025
Debt Disclosure [Abstract]  
Debt Debt
On June 30, 2023, or the Effective Date, the Company entered into the Loan Agreement with Hercules, which was subsequently amended on October 31, 2024, and July 30, 2025 (the “Loan Agreement”) and provides for aggregate maximum borrowings of up to $50.0 million, consisting of (i) a term loan of $30.0 million, which was funded on the Effective Date, and (ii) subject to the approval of Hercules’ investment committee in its sole discretion, and available during the interest-only period, an additional term loan of $20.0 million.
The term loan will mature on July 1, 2027. The outstanding principal balance of the term loan bears interest at an annual rate equal to the greater of either (i) the prime rate as reported in The Wall Street Journal plus 1.50% or (ii) 9.75%. Accrued interest is payable monthly following the funding of each term loan. In addition to accrued interest, payment-in-kind (PIK) interest of 1.40% will be added to the balance of the loan. Payments under the Loan Agreement are interest only until the first principal payment is due on January 2, 2026 (subject to extension if a certain performance milestone is met), followed by
equal monthly payments of principal and interest through the scheduled maturity date, July 1, 2027. The carrying value of the Company’s outstanding debt approximates fair value, reflecting interest rates currently available to the Company.
The Company incurred fees and transaction costs totaling $3.3 million associated with the initial term loan, which are recorded as a reduction to the carrying value of the long-term debt in the condensed consolidated balance sheets. These fees included $0.4 million of facility fees, $0.8 million of company fees, $0.7 million in warrants, and $1.4 million of end of term charges. The fees, transaction costs, and the end of term charges are amortized to interest expense through the maturity date using the effective interest method. The effective interest rate of the Loan Agreement was 14.8% as of September 30, 2025.

The Company issued warrants to Hercules to purchase the Company’s Ordinary Shares equal to the quotient derived by dividing (i) the amount equal to (a) 2.5% times (b) the aggregate principal amount of term loan advances made and funded under the Loan Agreement by (ii) the exercise price of the warrants. Upon receipt of the first term loan in June 2023, 94,222 shares became exercisable to Hercules with a fair market value of $0.7 million.

The Loan Agreement includes a financial covenant requiring us to maintain a minimum level of $22.5 million of cash during the period commencing on July 1, 2024 (subject to adjustment if certain performance milestones are met). If the Company meets the performance milestones, the minimum cash covenant will not apply if its market capitalization is at least $750.0 million. The Company was in compliance with all covenants of the Loan Agreement as of September 30, 2025 and December 31, 2024.
Long-term debt consisted of the following (in thousands):
September 30,December 31,
20252024
Term loan payable$30,000 $30,000 
End of term charge1,425 1,425 
Future principal payments and end of term charge$31,425 $31,425 
PIK interest payable977 649 
Unamortized debt issuance costs(1,133)(1,909)
Carrying value of long-term debt$31,269 $30,165 
Less: current portion
$(12,669)$(5,513)
Non-current portion
$18,600 $24,652 
Future principal payments, including End of Term Charge, are as follows (in thousands):
December 31, 2025— 
December 31, 202618,252 
December 31, 202713,173 
Total$31,425 
Interest expense associated with the Loan Agreement for the nine months ended September 30, 2025 and 2024 was $3.4 million and $3.3 million, respectively.
v3.25.3
Fair Value Measurements
 9 Months Ended
Sep. 30, 2025
Fair Value Disclosures [Abstract]  
Fair Value Measurements Fair Value Measurements
The following table presents, as of September 30, 2025, information about the Company’s warrant liabilities that are measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation inputs the Company utilized to determine such fair value:
January 13, 2025September 30, 2025
LevelAmount
Level
Amount
Warrant Liabilities:
Pre-funded Warrants
2$37,220 2$49,850 
2025 ADS Warrants
355,7263115,713
Total Warrant Liabilities
$92,946 $165,563 
The Pre-funded Warrants and 2025 ADS Warrants are accounted for as liabilities in accordance with ASC 815-40, Derivatives and Hedging, Contracts in Entity’s Own Equity (“ASC 815-40”), as both warrants contain contingent exercise provisions that do not meet the requirements of the indexation guidance under ASC 815-40 and could require the Company to pay cash to settle the warrants. The warrants are presented within warrant liabilities in the accompanying condensed consolidated balance sheets. The warrant liabilities were measured at fair value at inception and on a recurring basis, with changes in fair value presented within the condensed consolidated statements of operations and comprehensive loss.
The Pre-funded Warrants are considered to be Level 2 in the fair value hierarchy as the inputs used to determine fair market value are observable against the Company’s stock price. The 2025 ADS Warrant are considered to be Level 3 in the fair value hierarchy as they have been recorded at fair value using the Black-Scholes model, using unobservable assumptions that have been probability-weighted for specified data milestones. As of September 30, 2025, the assumptions are as follows:
January 13, 2025September 30, 2025
Exercise price$5.7960$5.7960
Market price$3.37$5.73
Volatility
 146.1% to 158.7%
 150.0% to 153.6%
Risk-free rate4.6%3.7%
Dividend yield—%—%
Term (in years)
4.0 to 4.4 years
3.36 to 3.42 years
The following table reflects the fair value of the Company’s warrant liabilities for the nine months ended September 30, 2025:
Pre-Funded Warrants
ADS Warrants
Fair value as of December 31, 2024
$— $— 
Initial fair value as of January 13, 2025
37,22055,726
Exercise of warrant liabilities
(10,153)0
Fair value change of warrant liabilities
22,78359,987
Fair value as of September 30, 2025
$49,850 $115,713 
The fair value change of warrant liabilities at September 30, 2025 was $84.4 million, which included a $1.6 million loss upon issuance of the Pre-funded warrants and a $82.8 million loss in fair value between the initial fair value and the fair value as of the balance sheet date. During the nine months ended September 30, 2025, there were no transfers between Level 1, Level 2 and Level 3.
v3.25.3
Shareholders' Equity
 9 Months Ended
Sep. 30, 2025
Equity [Abstract]  
Shareholders' Equity Shareholders’ Equity
Ordinary Shares
Each ordinary share entitles the holder to one vote on all matters submitted to a vote of the Company’s shareholders. Ordinary shareholders are entitled to receive dividends, if any, as may be declared by the board of directors. Through September 30, 2025, no cash dividends had been declared or paid by the Company.

At-the-Market Facility
On October 8, 2021, the Company entered into a Sales Agreement with Cowen and Company, LLC, or Cowen, under which the Company was permitted to issue and sell from time to time up to $150.0 million of its ADSs, each representing one ordinary share, through Cowen as the sales agent. Pursuant to the Sales Agreement dated October 8, 2021, through February 27, 2025, we sold 5,491,836 ADSs under our ATM offering program, resulting in $54.8 million in net proceeds. On February 27, 2025, the Company entered into a new Sales Agreement under which the Company may issue and sell from time to time up to $150.0 million of our ADSs, subject to the terms of the Sales Agreement. Sales of the Company’s ADSs, if any, will generally be made at market prices. To date, the Company has not sold any ADSs under this Sales Agreement.
Warrants
Equity-classified
On June 30, 2023, the Company entered into a Warrant Agreement with Hercules, which provides Hercules with the right to purchase a number of the Company’s Ordinary Shares, equal to the quotient derived by dividing (i) the amount equal to (a) 2.5% times (b) the aggregate principal amount of term loan advances made and funded under the Loan Agreement by (ii) the exercise price. Upon receipt of each term loan, the Warrant will automatically become exercisable and will expire in 10 years (on June 30, 2033). On June 30, 2023, with the receipt of the first term loan, 94,222 shares became exercisable to Hercules with a fair market value of $0.7 million.

On August 18, 2023, in connection with the PIPE, the Company issued and sold warrants to purchase up to 16,076,750 ADSs, each representing one ordinary share, at a purchase price of $9.93 per ADS. The PIPE Warrants became exercisable for a three year period beginning in February 2024. Through September 30, 2025, PIPE Warrants were exercised for 3,752,050 ADSs, resulting in $37.3 million in exercise proceeds. During the three months ended September 30, 2025, no PIPE warrants were exercised.

Liability-classified
On January 13, 2025, in connection with the 2025 Financing, the Company issued and sold (i) 24,014,728 ADSs, each representing one ordinary share, (ii) in lieu of ADSs, Pre-funded Warrants to purchase up to 11,044,720 ADSs, and (iii) accompanying 2025 ADS Warrants to purchase up to 11,044,720 ADSs, each representing one ordinary share. The Pre-funded Warrants have an exercise price of $0.0001 per ADS and are exercisable immediately. The Pre-funded Warrants expire when exercised in full. The 2025 ADS Warrants have an exercise price of $5.7960 per ADS and are exercisable following a specified data milestone. The 2025 ADS Warrants will expire three years after such warrants become exercisable. Once the ADS Warrants become exercisable, the Company may force the exercise of the 2025 ADS Warrants (by way of cash or cashless exercise, at the Company’s option), in whole or in part, by delivering a notice of forced exercise to the holders, provided that the closing price for the Company’s ADSs on Nasdaq exceeded the warrant exercise price of $5.796 for the three consecutive trading days prior to the date on which the notice of forced exercise is delivered. During the three months ended September 30, 2025, 2,344,720 Pre-funded Warrants were exercised, resulting in a $10.2 million reduction in warrant liabilities.
The 2025 Financing comprising of ADSs, Pre-funded Warrants and 2025 ADS Warrants, resulted in aggregate proceeds of $149.8 million, with issuance costs of $9.4 million. Since the Pre-funded Warrants and 2025 ADS Warrants have been classified as a liability and recorded at fair value with changes in fair value recorded in the condensed consolidated income statement, the aggregate proceeds have been allocated first to these warrants at their respective fair values at the issuance date. The residual has been allocated to the ADSs issued as part of the 2025 Financing and recognized within equity.
v3.25.3
Share-Based Compensation
 9 Months Ended
Sep. 30, 2025
Share-Based Payment Arrangement [Abstract]  
Share-Based Compensation Share-Based Compensation
2017 Equity Incentive Plan
Under the Company’s historical shareholder and subscription agreements, the Company was authorized to issue restricted shares, restricted share units, as well as options, as incentives to its employees, non-employees and members of its board of directors.
As of September 30, 2025, the Company was authorized to issue a total of 440,101 ordinary shares underlying outstanding options granted under the 2017 Plan prior to our initial public offering, or IPO.
2020 Employee Share Purchase Plan
The Company’s 2020 Employee Share Purchase Plan, or the ESPP, provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2022 and each January 1 thereafter through termination of the 2020 Plan, by the lesser of (i) 1% of the outstanding number of ordinary shares on the immediately preceding December 31, (ii) 510,080 ordinary shares or (iii) such lesser number of ordinary shares as determined by the plan administrator.
2020 Share Option Plan
The Company’s 2020 Share Option and Incentive Plan, or the 2020 Plan, allows the compensation and leadership development committee to make equity-based, including options and restricted share units, and cash-based incentive awards to the Company’s officers, employees, directors and other key persons (including consultants).
The Company initially reserved 2,074,325 of its ordinary shares for the issuance of awards under the 2020 Plan. The 2020 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2022, by up to 4% of the outstanding number of ordinary shares on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation and leadership development committee. The total number of ordinary shares that were authorized for issuance under the 2020 Plan is 10,680,217 shares as of September 30, 2025, of which 2,697,219 shares remained available for future grant.

2022 Inducement Option Award
During 2022, the Company granted a non-qualified share option to purchase up to 600,000 ordinary shares as an inducement grant to our chief executive officer.
Share-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands):
Three Months Ended September 30,Nine Months Ended September 30,
2025202420252024
Research and development1,224 2,661 4,037 7,921 
General and administrative1,983 2,312 6,701 7,102 
Total share-based compensation expense
$3,207 $4,973 $10,738 $15,023 
v3.25.3
Net Loss Per Share
 9 Months Ended
Sep. 30, 2025
Earnings Per Share [Abstract]  
Net Loss Per Share Net Loss Per Share
The Company computes basic net loss per share by dividing net loss by the weighted-average number of shares outstanding. The Company computes diluted net loss per share by dividing net loss by the weighted-average number of shares and dilutive potential share equivalents then outstanding during the period. The Company’s potentially dilutive securities, which include unvested ordinary shares, unvested restricted share units, options granted and warrants, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the
weighted-average number of ordinary shares outstanding used to calculate both basic and diluted net loss per share attributable to ordinary shareholders is the same.
The Company excluded the following potential ordinary shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to ordinary shareholders for the periods presented because including them would have had an anti-dilutive effect:
Nine Months Ended September 30,
20252024
Employee share purchase plan
40,342 27,615 
Unvested restricted share units770,652 702,183 
Share options7,991,809 8,718,938 
Warrants - equity-classified
12,418,92212,418,922 
Warrants - liability-classified
43,759,448— 
64,981,17321,867,658
v3.25.3
Commitments and Contingencies
 9 Months Ended
Sep. 30, 2025
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and Contingencies
Legal Proceedings
From time to time, the Company may be a party to litigation or subject to claims incident to the ordinary course of business. The Company was not a party to any material litigation and did not have material contingency reserves established for any liabilities as of September 30, 2025 or December 31, 2024.
Indemnification
In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into deeds of indemnity with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers in accordance with the indemnification obligations under its Articles of Association. The Company currently has directors’ and officers’ insurance.
v3.25.3
Segment Reporting
 9 Months Ended
Sep. 30, 2025
Segment Reporting [Abstract]  
Segment Reporting Segment Reporting
The Company has one operating segment. The table below is a summary of the segment loss, including significant segment expenses (in thousands):
Three Months Ended September 30,Nine Months Ended September 30,
2025202420252024
Operating expenses:
Research and Development:
Development expenses
$17,862 $22,647 $61,000 $54,628 
Personnel expenses
6,416 6,409 18,598 19,893 
Non-cash share-based compensation expense
1,224 2,661 4,037 7,921 
Other expenses1
1,823 1,211 4,895 4,456 
General and Administrative:
Personnel expenses
4,780 5,169 14,459 16,325 
Legal and professional fees
4,440 4,393 17,171 10,143 
Facilities and other expenses1
2,007 3,093 6,223 9,322 
Non-cash share-based compensation expense
1,984 2,313 6,702 7,103 
Total operating expenses
40,536 47,896 133,085 129,791 
Operating loss
(40,536)(47,896)(133,085)(129,791)
Fair value change of warrant liabilities
(101,318)— (84,398)— 
Benefit from R&D tax credit3,924 4,084 16,659 10,894 
Interest income1,588 1,977 5,872 6,645 
Interest expense(1,105)(1,137)(3,380)(3,347)
Foreign exchange (losses) gains
(883)4,452 3,599 3,894 
Other income
383 191 1,010 486 
Income tax expense230 (173)(261)(571)
Net loss
$(137,717)$(38,502)$(193,984)$(111,790)
1Other expenses include subscriptions and memberships, consulting fees and company insurance.
v3.25.3
Insider Trading Arrangements
 3 Months Ended
Sep. 30, 2025
Trading Arrangements, by Individual  
Rule 10b5-1 Arrangement Adopted false
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
v3.25.3
Summary of Significant Accounting Policies (Policies)
 9 Months Ended
Sep. 30, 2025
Accounting Policies [Abstract]  
Basis of Presentation
Basis of Presentation
The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or U.S. GAAP. The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements as of and for the year ended December 31, 2024, and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, necessary for the fair statement of the Company’s financial position for the reported periods.
The results of the Company’s operations for any interim period are not necessarily indicative of the results of the Company’s operations for any other interim period or for a full fiscal year. These interim financial statements should be read in conjunction with the audited consolidated financial statements as of and for the year ended December 31, 2024, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the SEC, on February 27, 2025. The condensed consolidated balance sheet at December 31, 2024, was derived from audited annual consolidated financial statements but does not contain all of the footnote disclosures from the annual financial statements.
Principles of Consolidation
Principles of Consolidation
The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated on consolidation.
Use of Estimates
Use of Estimates
The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of income and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, warrant liabilities. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ materially from those estimates.
Recently Issued Accounting Pronouncements
Recently Issued Accounting Pronouncements
In December 2023, the FASB issued ASU 2023-09 - Income Taxes (Topic 740): Improvements to Income Tax Disclosures, designed to improve income tax disclosure requirements, primarily through increased disaggregation disclosures within the effective tax rate reconciliation as well as enhanced disclosures on income taxes paid. The guidance is effective for all fiscal years beginning after December 15, 2024. The new standard can be adopted on a prospective basis with an option to be adopted retrospectively and early adoption is permitted. We are currently evaluating this guidance to determine its impact on the Company’s year-end consolidated financial statement disclosures.
In November 2024, the FASB issued ASU 2024-03 - Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, designed to improve disclosures, primarily through increased expense disaggregation. Additionally, in January 2025, the FASB issued ASU 2025-01 to clarify the effective date of ASU 2024-03. The guidance is effective for all fiscal years beginning after December 15, 2026, and interim reporting periods within annual reporting periods beginning after December 15, 2027. The new standard can be adopted on a prospective basis with an option to be adopted retrospectively and early adoption is permitted. The Company is not early adopting the standard. We are currently evaluating this guidance to determine its impact on the Company’s consolidated financial statement disclosures.
v3.25.3
Prepaid Expenses and Other Current Assets (Tables)
 9 Months Ended
Sep. 30, 2025
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]  
Schedule of Prepaid Expenses and Other Current Assets
Prepaid expenses and other current assets consisted of the following (in thousands):
September 30,December 31,
20252024
UK R&D tax credit
$39,309 $20,712 
Prepaid research and development13,011 11,332 
VAT recoverable998 1,109 
Other current assets2,754 2,668 
$56,072 $35,821 
v3.25.3
Debt (Tables)
 9 Months Ended
Sep. 30, 2025
Debt Disclosure [Abstract]  
Schedule of Long-Term Debt
Long-term debt consisted of the following (in thousands):
September 30,December 31,
20252024
Term loan payable$30,000 $30,000 
End of term charge1,425 1,425 
Future principal payments and end of term charge$31,425 $31,425 
PIK interest payable977 649 
Unamortized debt issuance costs(1,133)(1,909)
Carrying value of long-term debt$31,269 $30,165 
Less: current portion
$(12,669)$(5,513)
Non-current portion
$18,600 $24,652 
Schedule of Maturities of Long-Term Debt
Future principal payments, including End of Term Charge, are as follows (in thousands):
December 31, 2025— 
December 31, 202618,252 
December 31, 202713,173 
Total$31,425 
v3.25.3
Fair Value Measurements (Tables)
 9 Months Ended
Sep. 30, 2025
Fair Value Disclosures [Abstract]  
Schedule of Fair Value, Liabilities Measured on Recurring Basis
The following table presents, as of September 30, 2025, information about the Company’s warrant liabilities that are measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation inputs the Company utilized to determine such fair value:
January 13, 2025September 30, 2025
LevelAmount
Level
Amount
Warrant Liabilities:
Pre-funded Warrants
2$37,220 2$49,850 
2025 ADS Warrants
355,7263115,713
Total Warrant Liabilities
$92,946 $165,563 
Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions The 2025 ADS Warrant are considered to be Level 3 in the fair value hierarchy as they have been recorded at fair value using the Black-Scholes model, using unobservable assumptions that have been probability-weighted for specified data milestones. As of September 30, 2025, the assumptions are as follows:
January 13, 2025September 30, 2025
Exercise price$5.7960$5.7960
Market price$3.37$5.73
Volatility
 146.1% to 158.7%
 150.0% to 153.6%
Risk-free rate4.6%3.7%
Dividend yield—%—%
Term (in years)
4.0 to 4.4 years
3.36 to 3.42 years
Schedule of Fair Value of Warrant Liabilities
The following table reflects the fair value of the Company’s warrant liabilities for the nine months ended September 30, 2025:
Pre-Funded Warrants
ADS Warrants
Fair value as of December 31, 2024
$— $— 
Initial fair value as of January 13, 2025
37,22055,726
Exercise of warrant liabilities
(10,153)0
Fair value change of warrant liabilities
22,78359,987
Fair value as of September 30, 2025
$49,850 $115,713 
v3.25.3
Share-Based Compensation (Tables)
 9 Months Ended
Sep. 30, 2025
Share-Based Payment Arrangement [Abstract]  
Summary of Share-based Compensation Expense
Share-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands):
Three Months Ended September 30,Nine Months Ended September 30,
2025202420252024
Research and development1,224 2,661 4,037 7,921 
General and administrative1,983 2,312 6,701 7,102 
Total share-based compensation expense
$3,207 $4,973 $10,738 $15,023 
v3.25.3
Net Loss Per Share (Tables)
 9 Months Ended
Sep. 30, 2025
Earnings Per Share [Abstract]  
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share
The Company excluded the following potential ordinary shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to ordinary shareholders for the periods presented because including them would have had an anti-dilutive effect:
Nine Months Ended September 30,
20252024
Employee share purchase plan
40,342 27,615 
Unvested restricted share units770,652 702,183 
Share options7,991,809 8,718,938 
Warrants - equity-classified
12,418,92212,418,922 
Warrants - liability-classified
43,759,448— 
64,981,17321,867,658
v3.25.3
Segment Reporting (Tables)
 9 Months Ended
Sep. 30, 2025
Segment Reporting [Abstract]  
Schedule of Segment Reporting Information, by Segment The table below is a summary of the segment loss, including significant segment expenses (in thousands):
Three Months Ended September 30,Nine Months Ended September 30,
2025202420252024
Operating expenses:
Research and Development:
Development expenses
$17,862 $22,647 $61,000 $54,628 
Personnel expenses
6,416 6,409 18,598 19,893 
Non-cash share-based compensation expense
1,224 2,661 4,037 7,921 
Other expenses1
1,823 1,211 4,895 4,456 
General and Administrative:
Personnel expenses
4,780 5,169 14,459 16,325 
Legal and professional fees
4,440 4,393 17,171 10,143 
Facilities and other expenses1
2,007 3,093 6,223 9,322 
Non-cash share-based compensation expense
1,984 2,313 6,702 7,103 
Total operating expenses
40,536 47,896 133,085 129,791 
Operating loss
(40,536)(47,896)(133,085)(129,791)
Fair value change of warrant liabilities
(101,318)— (84,398)— 
Benefit from R&D tax credit3,924 4,084 16,659 10,894 
Interest income1,588 1,977 5,872 6,645 
Interest expense(1,105)(1,137)(3,380)(3,347)
Foreign exchange (losses) gains
(883)4,452 3,599 3,894 
Other income
383 191 1,010 486 
Income tax expense230 (173)(261)(571)
Net loss
$(137,717)$(38,502)$(193,984)$(111,790)
1Other expenses include subscriptions and memberships, consulting fees and company insurance.
v3.25.3
Nature of Business (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended 9 Months Ended 22 Months Ended 41 Months Ended
Jan. 13, 2025
day
$ / shares
shares
Aug. 18, 2023
$ / shares
shares
Aug. 16, 2023
$ / shares
shares
Oct. 08, 2021
USD ($)
Jan. 31, 2025
day
$ / shares
shares
Sep. 30, 2025
USD ($)
$ / shares
shares
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Sep. 30, 2024
USD ($)
Jun. 30, 2024
USD ($)
Mar. 31, 2024
USD ($)
Sep. 30, 2025
USD ($)
$ / shares
shares
Sep. 30, 2024
USD ($)
Jun. 30, 2025
USD ($)
shares
Feb. 27, 2025
USD ($)
shares
Jan. 31, 2025
£ / shares
shares
Dec. 31, 2024
USD ($)
Feb. 29, 2024
$ / shares
Jun. 30, 2023
USD ($)
Conversion of Stock [Line Items]                                      
Ordinary share conversion ratio (in shares)   1   1                              
Proceeds from the exercise of warrants                       $ 0 $ 37,258            
Net loss           $ (137,717) $ (38,403) $ (17,864) $ (38,502) $ (38,101) $ (35,187) (193,984) (111,790)            
Accumulated deficit           728,716           728,716         $ 534,732    
Cash and cash equivalents           $ 185,937     $ 206,953     185,937 $ 206,953       $ 165,081    
PIPE Warrants                                      
Conversion of Stock [Line Items]                                      
Sale of stock, shares issued in transaction (in shares) | shares           0               3,752,050          
Proceeds from the exercise of warrants                       37,300   $ 37,300          
Proceeds from warrant exercises, fully exercised                       $ 122,400              
2025 ADS Warrants                                      
Conversion of Stock [Line Items]                                      
Warrant exercise price (in dollars per share) | $ / shares $ 5.7960         $ 5.7960           $ 5.7960              
Loan Agreement                                      
Conversion of Stock [Line Items]                                      
Convertible notes, face amount                                     $ 50,000
Loan Agreement, Term Loan One                                      
Conversion of Stock [Line Items]                                      
Convertible notes, face amount                                     $ 30,000
Initial Public Offering | American Depositary Shares                                      
Conversion of Stock [Line Items]                                      
Maximum amount of stock that may be sold       $ 150,000                              
Amount authorized       $ 150,000                     $ 150,000        
At-The-Market Offering                                      
Conversion of Stock [Line Items]                                      
Sale of stock, shares issued in transaction (in shares) | shares                             5,491,836        
Consideration received on transaction                             $ 54,800        
At-The-Market Offering | American Depositary Shares                                      
Conversion of Stock [Line Items]                                      
Amount authorized                             $ 150,000        
Private Placement                                      
Conversion of Stock [Line Items]                                      
Ordinary share conversion ratio (in shares)     1                                
Sale of stock, shares issued in transaction (in shares) | shares   16,076,750 16,076,750                 3,752,050              
Sale of stock, price per share (in dollars per share) | $ / shares     $ 7.78                                
Warrant exercise price (in dollars per share) | $ / shares                                   $ 9.93  
Private Placement | PIPE Warrants                                      
Conversion of Stock [Line Items]                                      
Warrant exercise price (in dollars per share) | $ / shares   $ 9.93                                  
Term (in years)                                   3 years  
Underwritten Offering | 2025 ADS Warrants                                      
Conversion of Stock [Line Items]                                      
Ordinary share conversion ratio (in shares) 1       1                            
Sale of stock, shares issued in transaction (in shares) | shares 24,014,728       24,014,728                            
Sale of stock, price per share (in dollars per share) | (per share)         $ 4.2750                     £ 0.008      
Warrant exercise price (in dollars per share) | $ / shares         $ 5.7960                            
Term (in years)         3 years                     3 years      
Purchase of warrants (in shares) | shares         24,014,728                     24,014,728      
Threshold consecutive trading days | day 3       3                            
Underwritten Offering | Pre-funded Warrants                                      
Conversion of Stock [Line Items]                                      
Sale of stock, price per share (in dollars per share) | $ / shares         $ 4.2649                            
Warrant exercise price (in dollars per share) | $ / shares         $ 0.0001                            
Purchase of warrants (in shares) | shares         11,044,720                     11,044,720      
Warrants exercised (in shares) | shares           2,344,720           2,344,720              
v3.25.3
Prepaid Expenses and Other Current Assets (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2023
Sep. 30, 2025
Dec. 31, 2024
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]      
UK R&D tax credit   $ 39,309 $ 20,712
Prepaid research and development   13,011 11,332
VAT recoverable   998 1,109
Other current assets   2,754 2,668
Prepaid expense and other current assets   $ 56,072 $ 35,821
Increase to research and development tax credits $ 4,100    
v3.25.3
Debt - Narrative (Details) - USD ($)
$ in Millions
 9 Months Ended
Jun. 30, 2023
Sep. 30, 2025
Sep. 30, 2024
Debt Instrument [Line Items]      
Fees and transaction costs   $ 3.3  
Number of shares available for purchase, percent of principal amount of term loan (as a percent) 0.025 0.025  
Number of options exercisable (in shares) 94,222    
Fair value of exercisable options $ 0.7    
Debt interest expense   $ 3.4 $ 3.3
Facility Fees      
Debt Instrument [Line Items]      
Fees and transaction costs   0.4  
Company Fees      
Debt Instrument [Line Items]      
Fees and transaction costs   0.8  
Warrants - liability-classified      
Debt Instrument [Line Items]      
Fees and transaction costs   0.7  
End of Term Charge      
Debt Instrument [Line Items]      
Fees and transaction costs   $ 1.4  
Loan Agreement      
Debt Instrument [Line Items]      
Convertible notes, face amount $ 50.0    
Interest rate, prime margin (as a percent) 1.50%    
Stated interest rate 9.75%    
Paid-in-kind interest rate 0.0140    
Effective interest rate   14.80%  
Market capitalization   $ 750.0  
Loan Agreement, Term Loan One      
Debt Instrument [Line Items]      
Convertible notes, face amount $ 30.0    
Loan Agreement, Term Loan Two      
Debt Instrument [Line Items]      
Convertible notes, face amount $ 20.0    
Loan Agreement, Term Loan Three      
Debt Instrument [Line Items]      
Debt instrument covenant, cash on hand   $ 22.5  
v3.25.3
Debt - Components of Debt (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Debt Disclosure [Abstract]    
Term loan payable $ 30,000 $ 30,000
End of term charge 1,425 1,425
Future principal payments and end of term charge 31,425 31,425
PIK interest payable 977 649
Unamortized debt issuance costs (1,133) (1,909)
Carrying value of long-term debt 31,269 30,165
Less: current portion (12,669) (5,513)
Non-current portion $ 18,600 $ 24,652
v3.25.3
Debt - Schedule of Principal Payments (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Debt Disclosure [Abstract]    
December 31, 2025 $ 0  
December 31, 2026 18,252  
December 31, 2027 13,173  
Future principal payments and end of term charge $ 31,425 $ 31,425
v3.25.3
Fair Value Measurements - Schedule of Fair Value, Liabilities Measured on Recurring Basis (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Jan. 13, 2025
Dec. 31, 2024
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Warrant liabilities $ 165,563 $ 92,946 $ 0
Pre-funded Warrants | Fair Value, Recurring | Level 2      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Warrant liabilities 49,850 37,220  
2025 ADS Warrants | Fair Value, Recurring | Level 3      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Warrant liabilities $ 115,713 $ 55,726  
v3.25.3
Fair Value Measurements - Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions (Details) - 2025 ADS Warrants
Sep. 30, 2025
$ / shares
Jan. 13, 2025
$ / shares
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Exercise price $ 5.7960 $ 5.7960
Market price    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Warrants and rights outstanding 5.73 3.37
Risk-free rate    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Warrants and rights outstanding 0.037 0.046
Dividend yield    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Warrants and rights outstanding 0 0
Minimum    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Term (in years) 3 years 4 months 9 days 4 years
Minimum | Volatility    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Warrants and rights outstanding 1.500 1.461
Maximum    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Term (in years) 3 years 5 months 1 day 4 years 4 months 24 days
Maximum | Volatility    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Warrants and rights outstanding 1.536 1.587
v3.25.3
Fair Value Measurements - Schedule of Fair Value of Warrant Liabilities (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Jan. 13, 2025
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Fair value change of warrant liabilities $ (101,318) $ 0 $ (84,398) $ 0  
Pre-funded Warrants          
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Beginning balance of fair value     0    
Initial fair value as of January 13, 2025 49,850   49,850   $ 37,220
Exercise of warrant liabilities     (10,153)    
Fair value change of warrant liabilities     22,783    
Ending balance of fair value 49,850   49,850    
2025 ADS Warrants          
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Beginning balance of fair value     0    
Initial fair value as of January 13, 2025 115,713   115,713   $ 55,726
Exercise of warrant liabilities     0    
Fair value change of warrant liabilities     59,987    
Ending balance of fair value $ 115,713   $ 115,713    
v3.25.3
Fair Value Measurements - Narrative (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Fair value change of warrant liabilities $ (101,318) $ 0 $ (84,398) $ 0
Loss in fair value between initial fair value and balance sheet fair value     (82,800)  
Pre-funded Warrants        
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Fair value change of warrant liabilities     22,783  
Loss on issuance of warrants     $ (1,600)  
v3.25.3
Shareholder's Equity (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended 9 Months Ended 22 Months Ended 41 Months Ended
Jan. 13, 2025
USD ($)
day
$ / shares
shares
Aug. 18, 2023
$ / shares
shares
Aug. 16, 2023
shares
Oct. 08, 2021
USD ($)
Jan. 31, 2025
day
$ / shares
shares
Sep. 30, 2025
$ / shares
shares
Sep. 30, 2025
USD ($)
$ / shares
shares
Sep. 30, 2024
USD ($)
Jun. 30, 2025
USD ($)
shares
Feb. 27, 2025
USD ($)
shares
Feb. 29, 2024
$ / shares
Jun. 30, 2023
USD ($)
shares
Class of Stock [Line Items]                        
Ordinary share conversion ratio (in shares)   1   1                
Number of shares available for purchase, percent of principal amount of term loan (as a percent)           0.025 0.025         0.025
Number of options exercisable (in shares) | shares                       94,222
Fair value of exercisable options                       $ 700
Proceeds from the exercise of warrants             $ 0 $ 37,258        
PIPE Warrants                        
Class of Stock [Line Items]                        
Sale of stock, shares issued in transaction (in shares) | shares           0     3,752,050      
Proceeds from the exercise of warrants             $ 37,300   $ 37,300      
2025 ADS Warrants                        
Class of Stock [Line Items]                        
Warrant exercise price (in dollars per share) | $ / shares $ 5.7960         $ 5.7960 $ 5.7960          
Exercise of warrant liabilities             $ 0          
Proceeds from exercise of options $ 149,800                      
Issuance costs of warrant $ 9,400                      
Pre-funded Warrants                        
Class of Stock [Line Items]                        
Exercise of warrant liabilities             $ 10,153          
Hercules Capital, Inc.                        
Class of Stock [Line Items]                        
Term (in years)                       10 years
Number of options exercisable (in shares) | shares                       94,222
Fair value of exercisable options                       $ 700
At-The-Market Offering                        
Class of Stock [Line Items]                        
Sale of stock, shares issued in transaction (in shares) | shares                   5,491,836    
Consideration received on transaction                   $ 54,800    
Private Placement                        
Class of Stock [Line Items]                        
Ordinary share conversion ratio (in shares)     1                  
Sale of stock, shares issued in transaction (in shares) | shares   16,076,750 16,076,750       3,752,050          
Warrant exercise price (in dollars per share) | $ / shares                     $ 9.93  
Private Placement | PIPE Warrants                        
Class of Stock [Line Items]                        
Term (in years)                     3 years  
Warrant exercise price (in dollars per share) | $ / shares   $ 9.93                    
Underwritten Offering | 2025 ADS Warrants                        
Class of Stock [Line Items]                        
Ordinary share conversion ratio (in shares) 1       1              
Sale of stock, shares issued in transaction (in shares) | shares 24,014,728       24,014,728              
Term (in years)         3 years              
Warrant exercise price (in dollars per share) | $ / shares         $ 5.7960              
Purchase of warrants (in shares) | shares         24,014,728              
Threshold consecutive trading days | day 3       3              
Underwritten Offering | Pre-funded Warrants                        
Class of Stock [Line Items]                        
Warrant exercise price (in dollars per share) | $ / shares         $ 0.0001              
Purchase of warrants (in shares) | shares         11,044,720              
Warrants exercised (in shares) | shares           2,344,720 2,344,720          
American Depositary Shares | Initial Public Offering                        
Class of Stock [Line Items]                        
Amount authorized       $ 150,000           150,000    
American Depositary Shares | At-The-Market Offering                        
Class of Stock [Line Items]                        
Amount authorized                   $ 150,000    
v3.25.3
Share-Based Compensation - 2020 Employee Share Purchase Plan (Details) - shares
 9 Months Ended
Sep. 30, 2025
Dec. 31, 2022
Sep. 30, 2020
2020 Share Option Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares issued (in shares) 10,680,217    
2020 Share Option Plan | Ordinary shares      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares reserved for future issuance (in shares)     2,074,325
Maximum percentage of shares outstanding number of shares reserved for issuance may increase (in percent)     4.00%
2022 Inducement Grant Option Award | Ordinary shares      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares available for grant (in shares)   600,000  
Employee Stock Option | 2017 Equity Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized (in shares) 440,101    
Employee stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allowable increase in shares authorized for issuance, percentage of outstanding stock (in percent) 1.00%    
Maximum increase in shares available for issuance (in shares) 510,080    
Number of shares available for grant (in shares) 2,697,219    
v3.25.3
Share-Based Compensation - Schedule of Share-based Compensation Expense (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total share-based compensation expense $ 3,207 $ 4,973 $ 10,738 $ 15,023
Research and development        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total share-based compensation expense 1,224 2,661 4,037 7,921
General and administrative        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total share-based compensation expense $ 1,983 $ 2,312 $ 6,701 $ 7,102
v3.25.3
Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share (in shares) 64,981,173 21,867,658
Employee share purchase plan    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share (in shares) 40,342 27,615
Unvested restricted share units    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share (in shares) 770,652 702,183
Share options    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share (in shares) 7,991,809 8,718,938
Warrants - equity-classified    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share (in shares) 12,418,922 12,418,922
Warrants - liability-classified    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share (in shares) 43,759,448 0
v3.25.3
Segment Reporting (Details)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Sep. 30, 2024
USD ($)
Jun. 30, 2024
USD ($)
Mar. 31, 2024
USD ($)
Sep. 30, 2025
USD ($)
segment
Sep. 30, 2024
USD ($)
Segment Reporting [Abstract]                
Number of operating segments | segment             1  
Revenue, Major Customer [Line Items]                
Research and development $ 27,325     $ 32,928     $ 88,530 $ 86,898
General and administrative 13,211     14,968     44,555 42,893
Total operating expenses 40,536     47,896     133,085 129,791
Operating loss (40,536)     (47,896)     (133,085) (129,791)
Fair value change of warrant liabilities (101,318)     0     (84,398) 0
Benefit from R&D tax credit 3,924     4,084     16,659 10,894
Interest income 1,588     1,977     5,872 6,645
Interest expense 1,105     1,137     3,380 3,347
Foreign exchange (losses) gains (883)     4,452     3,599 3,894
Other income 383     191     1,010 486
Income tax expense (230)     173     261 571
Net loss (137,717) $ (38,403) $ (17,864) (38,502) $ (38,101) $ (35,187) (193,984) (111,790)
Single Operating Segment                
Revenue, Major Customer [Line Items]                
Total operating expenses 40,536     47,896     133,085 129,791
Operating loss (40,536)     (47,896)     (133,085) (129,791)
Fair value change of warrant liabilities (101,318)     0     (84,398) 0
Benefit from R&D tax credit 3,924     4,084     16,659 10,894
Interest income 1,588     1,977     5,872 6,645
Interest expense (1,105)     (1,137)     (3,380) (3,347)
Foreign exchange (losses) gains (883)     4,452     3,599 3,894
Other income 383     191     1,010 486
Income tax expense 230     (173)     (261) (571)
Net loss (137,717)     (38,502)     (193,984) (111,790)
Development expenses | Single Operating Segment                
Revenue, Major Customer [Line Items]                
Research and development 17,862     22,647     61,000 54,628
Personnel expenses | Single Operating Segment                
Revenue, Major Customer [Line Items]                
Research and development 6,416     6,409     18,598 19,893
General and administrative 4,780     5,169     14,459 16,325
Non-cash share-based compensation expense | Single Operating Segment                
Revenue, Major Customer [Line Items]                
Research and development 1,224     2,661     4,037 7,921
General and administrative 1,984     2,313     6,702 7,103
Other expenses | Single Operating Segment                
Revenue, Major Customer [Line Items]                
Research and development 1,823     1,211     4,895 4,456
Legal and professional fees | Single Operating Segment                
Revenue, Major Customer [Line Items]                
General and administrative 4,440     4,393     17,171 10,143
Facilities and other expenses | Single Operating Segment                
Revenue, Major Customer [Line Items]                
General and administrative $ 2,007     $ 3,093     $ 6,223 $ 9,322