Summary of significant accounting policies (Policies)	6 Months Ended
Jun. 30, 2021
Summary of significant accounting policies
Use of estimates	Use of estimates The preparation of condensed consolidated financial statements in conformity with 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 expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual for research and development expenses, revenue recognition, share-based compensation expense, valuation procedures for right-of-use assets and liabilities, and income taxes, including the valuation allowance for deferred tax assets. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. Estimates are periodically reviewed in light of reasonable changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates or assumptions.
Significant Risks and Uncertainties	Significant Risks and Uncertainties In 2020, with the global spread of the ongoing COVID-19 pandemic, the Company established a cross-functional task force and implemented business continuity plans designed to address and mitigate the impact of the ongoing COVID-19 pandemic on the Company’s business. While the Company continues to experience limited financial impacts at this time, the extent to which the ongoing COVID-19 pandemic ultimately impacts the Company’s business, clinical development and regulatory efforts, corporate development objectives and the value of and market for the Company’s ADSs, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements in the United Kingdom, United States, Europe and other countries, and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects.
Unaudited Interim Financial Information	Unaudited Interim Financial Information Certain information in the footnote disclosures of the financial statements has been condensed or omitted pursuant to the rules and regulations of the SEC. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in the Company’s 2020 Annual Report. The accompanying condensed consolidated balance sheet at June 30, 2021, condensed consolidated statements of operations and comprehensive loss, condensed consolidated statements of shareholders’ equity for the three and six months ended June 30, 2021 and 2020, the condensed consolidated statements of cash flows for the six months ended June 30, 2021 and 2020, and the related financial information disclosed in these notes are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements for the year ended December 31, 2020, 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 as of June 30, 2021, the results of its operations for the three and six months ended June 30, 2021 and 2020, and its cash flows for the six months ended June 30, 2021 and 2020. The results for the three and six months ended June 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period.
Government grants	Government grants From time to time, the Company may enter into arrangements with governmental entities for the purpose of obtaining funding for research and development activities. The Company recognizes government grant funding in the condensed consolidated statements of operations and comprehensive loss as the related expenses being funded are incurred. The Company classifies government grants received under these arrangements as a reduction to the related research and development expense incurred. The Company analyzes each arrangement on a case-by-case basis. For the three and six months ended June 30, 2021, the Company recognized $0.8 million and $1.9 million, respectively, and for the three and six months ended June 30, 2020, the Company recognized zero and $0.1 million, respectively, as a reduction of research and development expense related to government grant arrangements.
Recently adopted accounting pronouncements	Recently adopted accounting pronouncements In 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 simplifies the accounting for income taxes and will be effective beginning after December 15, 2020. The adoption of ASU 2019‑12 did not have a material impact on the Company’s results of operations or cash flows. Recently issued accounting pronouncements In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 will change how companies account for credit losses for most financial assets and certain other instruments. For trade receivables, loans and held-to-maturity debt securities, companies will be required to recognize an allowance for credit losses rather than reducing the carrying value of the asset. In November 2019, the FASB issued ASU No. 2019-10, Financial Instruments — Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates to amend the effective date of ASU 2016-13, for entities eligible to be “smaller reporting companies,” as defined by the SEC, to be effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption is permitted. The Company has not elected to early adopt ASU No. 2016-13. The Company is currently evaluating the potential impact that the adoption of ASU 2016-13 will have on the Company’s financial position and results of operations.

Summary of significant accounting policies (Policies)

6 Months Ended

Jun. 30, 2021

Summary of significant accounting policies

The preparation of condensed consolidated financial statements in conformity with 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 expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual for research and development expenses, revenue recognition, share-based compensation expense, valuation procedures for right-of-use assets and liabilities, and income taxes, including the valuation allowance for deferred tax assets. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. Estimates are periodically reviewed in light of reasonable changes in circumstances, facts and experience.

Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates or assumptions.

Significant Risks and Uncertainties

In 2020, with the global spread of the ongoing COVID-19 pandemic, the Company established a cross-functional task force and implemented business continuity plans designed to address and mitigate the impact of the ongoing COVID-19 pandemic on the Company’s business. While the Company continues to experience limited financial impacts at this time, the extent to which the ongoing COVID-19 pandemic ultimately impacts the Company’s business, clinical development and regulatory efforts, corporate development objectives and the value of and market for the Company’s ADSs, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements in the United Kingdom, United States, Europe and other countries, and the effectiveness of actions taken globally to contain and treat the disease. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects.

Unaudited Interim Financial Information

Certain information in the footnote disclosures of the financial statements has been condensed or omitted pursuant to the rules and regulations of the SEC. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto for the year ended December 31, 2020 included in the Company’s 2020 Annual Report.

The accompanying condensed consolidated balance sheet at June 30, 2021, condensed consolidated statements of operations and comprehensive loss, condensed consolidated statements of shareholders’ equity for the three and six months ended June 30, 2021 and 2020, the condensed consolidated statements of cash flows for the six months ended June 30, 2021 and 2020, and the related financial information disclosed in these notes are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements for the year ended December 31, 2020, 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 as of June 30, 2021, the results of its operations for the three and six months ended June 30, 2021 and 2020, and its cash flows for the six months ended June 30, 2021 and 2020. The results for the three and six months ended June 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period.

Government grants

From time to time, the Company may enter into arrangements with governmental entities for the purpose of obtaining funding for research and development activities. The Company recognizes government grant funding in the condensed consolidated statements of operations and comprehensive loss as the related expenses being funded are incurred. The Company classifies government grants received under these arrangements as a reduction to the related research and development expense incurred. The Company analyzes each arrangement on a case-by-case basis. For the three and six months ended June 30, 2021, the Company recognized $0.8 million and $1.9 million, respectively, and for the three and six months ended June 30, 2020, the Company recognized zero and $0.1 million, respectively, as a reduction of research and development expense related to government grant arrangements.

Recently adopted accounting pronouncements

In 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”). ASU 2019-12 simplifies the accounting for income taxes and will be effective beginning after December 15, 2020. The adoption of ASU 2019‑12 did not have a material impact on the Company’s results of operations or cash flows.

Recently issued accounting pronouncements

In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 will change how companies account for credit losses for most financial assets and certain other instruments. For trade receivables, loans and held-to-maturity debt securities, companies will be required to recognize an allowance for credit losses rather than reducing the carrying value of the asset. In November 2019, the FASB issued ASU No. 2019-10, Financial Instruments — Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates to amend the effective date of ASU 2016-13, for entities eligible to be “smaller reporting companies,” as defined by the SEC, to be effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption is permitted. The Company has not elected to early adopt ASU No. 2016-13. The Company is currently evaluating the potential impact that the adoption of ASU 2016-13 will have on the Company’s financial position and results of operations.