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. To the extent such incentives were in the form of share options, the options were granted pursuant to the terms of the 2017 Equity Incentive Plan, or the 2017 Plan. In July 2019, the Company’s board of directors adopted the 2017 Plan. The 2017 Plan provided for the grant of Enterprise Management Incentive, or EMI, options, to its UK employees, for the grant of options to its U.S. employees and non-employees of the Company. The 2017 Plan was administered by the board of directors.

As of June 30, 2022, the Company was authorized to issue a total of 1,810,688 ordinary shares underlying outstanding options granted under the 2017 Plan prior to the IPO.

Options granted under the 2017 Plan, typically vest over a three or four-year service period with 33.3% and 25% respectively, of the award vesting on the first anniversary of the commencement date and the balance vesting monthly over the remaining years. Restricted share units granted under the 2017 Plan typically vest over a four-year service period with 25% of the award vesting on the first anniversary of the commencement date and quarterly thereafter.

The options granted before June 30, 2020 were subject to 100% vesting upon the date of the listing of the Company's ordinary shares on any stock exchange. The options granted on June 30, 2020 were subject to 25% vesting upon the earlier occurrence of (i) the one year anniversary of the date of grant, or (ii) the date of the listing of the Company's ordinary shares on any stock exchange. Upon completion of the IPO, 866,268 options vested due to the accelerated vesting and a total of $3.5 million was immediately recognized in share-based compensation expense, including $1.4 million in research and development expenses and $2.1 million in general and administrative expenses.

The options granted on June 30, 2020 are subject to 25% vesting upon the earlier occurrence of (i) the one year anniversary of the date of grant, or (ii) the date of the listing of the Company's ordinary shares on any stock exchange, followed by straight line vesting for three years for the remaining 75% of the allocation until vested in full.

The restricted share units granted on June 30, 2020 are subject to 25% vesting upon the earlier of (i) the one year anniversary of the date of grant, or (ii) the first day following the six-month anniversary of the listing of the Company's ordinary shares on any stock exchange on which the closing price of the shares is 20% higher than the listing price for at least five consecutive trading days. Options granted under the 2017 Plan generally expire 10 years from the date of grant.

The Company’s 2020 Employee Share Purchase Plan, or the ESPP, was adopted by the Board in September 2020 and approved by shareholders in September 2020 and became effective upon the effectiveness of the Company’s Registration Statement on Form F-1 in connection with the IPO. The ESPP initially reserves and authorizes the issuance of up to a total of 340,053 ordinary shares to participating employees. 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

January 1, 2022, by the lesser of (i) 1% of the outstanding number of ordinary shares on the immediately preceding December 31 or (ii) 510,058 ordinary shares. The number of shares reserved under the ESPP is subject to change in the event of a share split, share dividend or other change in our capitalization.

On October 1, 2021, the Company launched the SIP and the ESPP, through which employees can purchase shares at a discounted price. At the end of six months, shares will automatically be purchased at the lower of the opening and closing price of the shares for the saving period minus a 15% discount.

In September 2020, the Company’s board of directors adopted, and the Company’s shareholders approved, the 2020 Share Option and Incentive Plan, or the 2020 Plan, which became effective upon the effectiveness of the Company’s Registration Statement on Form F-1 in connection with the IPO. The 2020 Plan allows the compensation and leadership development committee to make equity-based and cash-based incentive awards to the Company’s officers, employees, directors and other key persons (including consultants).

Options granted under the 2020 Plan generally expire 10 years from the date of grant and typically vest over a 4 year service period with 25% of the vesting on the first anniversary of the commencement date and the balance vesting monthly over the remaining years.

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 our compensation and leadership development committee. This number is subject to adjustment in the event of a sub-division, consolidation, share dividend or other change in our capitalization. The total number of ordinary shares that may be issued under the 2020 Plan was 3,755,119 shares as of June 30, 2022, of which 1,037,283 shares remained available for future grant.

The options granted in February 2022 under the 2020 Plan to employees generally expire 10 years from the date of grant. There are three potential vesting conditions for the February 2022 grants including: i) 25% per year over four year service period, ii) four year service period with 25% of the vesting on the first anniversary of the commencement date and the balance vesting monthly over the remaining years; and iii) monthly vesting over four year service period.

During the six months ended June 30, 2022 and 2021, the Company granted options to purchase 1,217,818 and 312,132 ordinary shares to employees and non-employees, respectively.


	Number of Shares	Weighted Average Grant Date Fair Value
Unvested and Outstanding as of December 31, 2021	115,140	$	10.19
Granted	92,590	$	13.13
Vested	(21,319)	$	10.27
Forfeited	—	$	—
Unvested and Outstanding as of June 30, 2022	186,411	$	11.86

As of June 30, 2022 and 2021, there was $2.0 million and $1.8 million of unrecognized compensation cost related to unvested restricted share units, respectively, which is expected to be recognized over a weighted-average period of 2.95 years and 3.05 years, respectively. The exercise price of restricted share units is at a nominal value less than £0.01 per share.


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2021	3,915,503	$	13.53	8.64	$	51,162
Granted	1,217,818	$	13.97
Exercised	(431,885)	$	0.84
Forfeited	(360,551)	$	8.98
Outstanding as of June 30, 2022	4,340,885	$	14.62	8.63	$	18,283
Exercisable as of June 30, 2022	1,897,406	$	5.62	7.97	$	15,618
Unvested as of June 30, 2022	2,443,479	$	19.88	9.14	$	2,665

The aggregate intrinsic value of share options is calculated as the difference between the exercise price of the share options and the fair value of the Company’s ordinary shares for those share options that had exercise prices lower than the fair value of the Company’s ordinary shares.

The weighted average grant-date fair value of share options granted was $10.67 and $25.29 per share during the six months ended June 30, 2022, and 2021, respectively.

As of June 30, 2022 and 2021, there was $29.7 million and $21.5 million of unrecognized compensation cost related to unvested share options, which is expected to be recognized over a weighted-average period of 2.93 years and 3.20 years, respectively.

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the share options granted to employees and directors during the six months ended June 30, 2022, and 2021 were as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
	2022			2021			2022			2021
Expected option life (years)	5.50 years			6.00 years			5.85 years			6.05 years
Expected volatility	81.17		%	67.40		%	80.29		%	67.70		%
Risk-free interest rate	3.35		%	1.08		%	1.80		%	0.83		%
Expected dividend yield	—		%	—		%	—		%	—		%
Fair value of underlying ordinary shares	$	10.08		$	36.13		$	15.01		$	41.80


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	1,830		934		3,622		1,735
General and administrative	1,348		970		2,684		1,835
Total stock based compensation expense	$	3,178	$	1,904	$	6,306	$	3,570