The Company maintains two equity compensation plans, the 2017 Stock Incentive Plan (as amended, the “2017 Plan”) and the 2019 Inducement Equity Incentive Plan (the “2019 Inducement Plan”), which provide for the grant of stock-based awards to its directors, officers and employees. The equity plans provide for the grant of non-qualified and incentive stock options, as well as restricted stock units (“RSUs”), restricted stock and other stock-based awards.

In August 2021, the Company's shareholders approved amendments to the 2017 Plan. The amendments provide for the following: (i) increases the number of shares of the Company’s common stock authorized for issuance under the 2017 Plan by 3,170,254 shares, (ii) removes the “evergreen” provision historically included in the 2017 Plan, and (iii) makes certain other amendments.

The weighted-average grant date fair value of options, estimated as of the grant date using the Black-Scholes option pricing model, was $7.96 and $14.57 per option for those options granted during the three months ended March 31, 2022 and 2021 respectively.

The following table summarizes stock option activity under all equity plans (excluding RSUs) during the three months ended March 31, 2022:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2021		4,890,716		$	11.75		7.62	$	24,263
Granted		952,604			11.15		—		—
Exercised		(17,616	)		10.72		—		—
Forfeited or cancelled		(50,636	)		14.80		—
Outstanding as of March 31, 2022		5,775,068		$	11.63		7.61	$	3,951
Outstanding as of March 31, 2022 - vested and expected to vest		5,775,068		$	11.63		7.61	$	3,951
Exercisable at March 31, 2022		2,868,263		$	9.47		6.29	$	3,684

As of March 31, 2022, a total of 8,720,127 shares have been authorized and reserved for issuance under all equity plans and 1,143,299 shares were available for future issuance under such plans.

The Company granted 657,757 RSUs to employees during the three months ended March 31, 2022.

The following table summarizes RSU activity under all equity plans during the three months ended March 31, 2022:


	Number of RSU Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2021		513,690			17.08
Granted		657,757			11.14
Vested and released		—			—
Forfeited or cancelled		(7,800	)		15.51
Outstanding as of March 31, 2022		1,163,647			13.73

As of March 31, 2022, there was approximately $14.9 million of total unrecognized compensation expense related to RSUs, which is expected to be recognized over a weighted-average period of approximately 3.67 years.

The fair value of the RSUs is determined on the date of grant based on the market price of the Company’s ordinary shares on that date. Each RSU represents the right to receive one share of the Company’s common stock, $0.001 par value per share, upon vesting. The RSUs vest in four equal annual installments, subject to the individual’s continued service to the Company through the applicable vesting date, and are subject to the terms and conditions of the Company’s form of RSU agreement under the 2017 Plan.

The Company recorded share-based compensation expense related to incentive stock options, nonqualified stock options, stock grants, and stock-based awards in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):


	Three Months Ended March 31,
	2022		2021

Research and development expenses	$	1,363	$	840
General and administrative expenses		1,840		1,169
Total	$	3,203	$	2,009