9. Share‑based compensation

Employee incentive pool

2019 Share Option Plan

In May 2019, the Company adopted the 2019 Share Option Plan (the “2019 Plan”), which became effective in conjunction with the IPO. In September 2019, the Compensation Committee of the Company’s Board of Directors approved immaterial clarifying amendments to the 2019 Plan which did not have an impact to the condensed consolidated financial statements. The 2019 Plan provides for the grant of options to purchase ordinary shares and other share-based awards to officers, employees, directors and other key persons (including consultants).

The Company initially reserved 2,470,583 ordinary shares for future issuance under the 2019 Plan. The number of ordinary shares reserved for issuance of the 2019 Plan will automatically increase on the first day of January, commencing on January 1, 2020, in an amount equal to 4% of the total number of ordinary shares outstanding on the last day of the preceding year, or a lesser number of shares determined by the Company’s board of directors, subject to adjustment in the event of a share split, share dividend or other change in capitalization. The number of shares reserved for issuance under the 2019 Plan was increased by 719,748 shares effective January 1, 2020. As of March 31, 2020, there were 567,433 shares available for issuance under the 2019 Plan.

Share options issued under the 2019 Share Option Plan have a 10 year contractual life, and generally either vest monthly over a three year service period, or over a four‑year service period with 25% of the award vesting on the first anniversary of the commencement date and the balance thereafter in 36 equal monthly installments. Certain awards granted to our directors are fully vested on the date of grant. The exercise price of share options issued under the 2019 Share Option Plan shall not be less than the fair value of ordinary shares as of the date of grant.

Pre-IPO Share Options and restricted shares

Prior to the IPO, the Company issued share options and ordinary shares, as administered by the board of directors, using standardized share option and share subscription agreements. To the extent such incentives were in the form of share options, the options may have been granted pursuant to a potentially tax-favored Enterprise Management Incentive (“EMI”) scheme available to U.K. employees, directors and consultants of the Company. Upon completion of the IPO, shares reserved for future issuance outside of the 2019 Share Option Plan were cancelled.

Options granted, as well as restricted shares granted as employee incentives prior to the IPO, typically vest over a four‑year service period with 25% of the award vesting on the first anniversary of the commencement date and the balance thereafter in 36 equal monthly installments and expire no later than 10 years from the date of grant.

Certain equity awards were issued in 2017 and 2018 for which 20% of the award vests upon the first anniversary of the vesting start date, 60% vests thereafter in 36 equal monthly installments, and 20% vest upon the earlier of the fourth anniversary of the vesting start date, or the achievement of a specified revenue threshold from the Company’s collaboration arrangements.

Options issued to U.K. employees prior to the IPO generally had an exercise price of £0.01 per share. The exercise price for share options granted to U.S. employees, had an exercise price that was not less than the fair value of ordinary shares as determined by the board of directors as of the date of grant. Prior to the IPO, the Company’s board of directors valued the Company’s ordinary shares based on input from management, considering the most recently available valuation of ordinary share performed by an independent third‑party valuation firm as well as additional factors which may have changed since the date of the most recent contemporaneous valuation through the date of grant.

Employee Share Purchase Plan (“ESPP”)

In May 2019, the Company adopted the 2019 Employee Stock Purchase Plan (the “ESPP”), which became effective in conjunction with the IPO. The Company initially reserved 215,000 ordinary shares for future issuance under this plan. The ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2020 and each January 1 thereafter through January 1, 2029, by the least of (i) 1% of the outstanding number of ordinary shares on the immediately preceding December 31; (ii) 430,000 ordinary shares or (iii) such lesser number of shares as determined by the Compensation Committee. The number of shares reserved under the ESPP is subject to adjustment in the event of a split-up, share dividend or other change in our capitalization. On January 1, 2020, the total number of shares available for issuance under the ESPP was increased by 179,937 ordinary shares pursuant to this provision.

Each offering to the employees to purchase shares under the ESPP will begin on each June 1 and December 1 and will end on the following November 30 and May 31, respectively. On each purchase date, which falls on the last date of each offering period, ESPP participants will purchase ordinary shares at a price per share equal to 85% of the lesser of (1) the fair market value of the shares on the offering date or (2) the fair market value of the shares on the purchase date. The occurrence and duration of offering periods under the ESPP are subject to the determinations of the Company’s compensation committee. As of March 31, 2020, there have been no offering periods to employees under ESPP.

Share‑based compensation

The Company recorded share‑based compensation expense in the following expense categories of its condensed consolidated statements of operations and comprehensive loss (in thousands):


	Three Months Ended
	March 31,
	2020		2019
Research and development expenses	$	675	$	108
General and administrative expenses		1,446		168
	$	2,121	$	276

Share options

The following table summarizes the Company’s option activity since December 31, 2019:


				Weighted
		Weighted		Average	Aggregate
	Number of	Average		Contractual	Intrinsic
	Shares	Exercise Price		Term	Value
				(in years)	(in thousands)
Outstanding as of December 31, 2019	2,634,346	$	9.57	9.04	$	2,868
Granted	1,030,361		10.17	—		—
Exercised	(1,071)		1.47	—		—
Forfeited	(8,748)		8.67	—		—
Outstanding as of March 31, 2020	3,654,888	$	9.74	9.17	$	14,973
Vested and expected to vest as of March 31, 2020	3,654,888	$	9.74	9.17	$	14,973
Options exercisable as of March 31, 2020	984,491	$	7.71	8.79	$	5,993

The weighted average grant‑date fair value of share options granted during the three months ended March 31, 2020 and 2019 was $6.68 per share and $3.68 per share, respectively.

Total share-based compensation expense for share options granted was $2.1 million for the three months ended March 31, 2020, and $0.2 million for the three months ended March 31, 2019. Expense for non-employee consultants for the three months ended March 31, 2020 and 2019 was immaterial.

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. The aggregate intrinsic value of share options exercised was immaterial during each of the three months ended March 31, 2020 and 2019.

The following table presents, on a weighted average basis, the assumptions used in the Black‑Scholes option‑pricing model to determine the fair value of share options granted to employees and directors:


	Three
	Months
	Ended
	March 31,
	2020		2019
Risk-free interest rate	1.6	%	2.7	%
Expected volatility	73.7	%	79.6	%
Expected dividend yield	—		—
Expected term (in years)	5.95		6.07

As of March 31, 2020, total unrecognized compensation expense related to the unvested employee and director share‑based awards was $15.3 million, which is expected to be recognized over a weighted average period of 2.9 years.

Restricted shares

The Company had granted restricted shares with service‑based vesting conditions. In conjunction with the IPO in May 2019, the board of directors modified the vesting terms to accelerate vesting for all then unvested restricted shares. As of March 31, 2020 and December 31, 2019 there are no unvested restricted ordinary shares. Total share-based compensation for unvested restricted shares granted was zero for the three months ended March 31, 2020, and $0.1 million for the three months ended March 31, 2019.

The fair value of employee restricted share awards vested, based on estimated fair values of the ordinary shares underlying the restricted share awards on the day of vesting, was zero during the three ended March 31, 2020, and $0.1 million during the three months ended March 31, 2019.

As of March 31, 2020, there was no unrecognized compensation cost related to the unvested employee and director restricted share awards.