The Company’s 2018 Stock Incentive Plan (the “2018 Plan”) provided for the Company to sell or issue incentive stock options or nonqualified stock options, restricted stock, and other equity awards to employees, directors and consultants of the Company. The 2018 Plan was administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions were determined at the discretion of the board of directors.

The total number of shares of common stock authorized under the 2018 Plan was 8,267,252 shares. Upon the effectiveness of the 2020 Plan, the Company ceased granting awards under the 2018 Plan, and the 1,928,487 shares of common stock remaining under the 2018 Plan became available for future issuance under the 2020 Plan.

In August 2020 the Company’s board of directors adopted and the Company’s stockholders approved the 2020 Plan (together with the 2018 Plan the “Plans”), which became effective on September 16, 2020. The 2020 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards to employees, directors, consultants and advisors of the Company. The 2020 Plan is administered by the Company’s board of directors or by a committee appointed by the board of directors. Upon the effectiveness of the 2020 Plan, the Company ceased granting awards under the 2018 Plan. The number of shares initially reserved for issuance under the 2020 Plan was 4,884,233. The number of shares of common stock reserved for issuance under the 2020 Plan automatically increases on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including the fiscal year commencing on, January 1, 2030, in an amount equal to the lower of (1) 5% of the shares of common stock outstanding on such date and (2) an amount determined by the Company’s board of directors. On January 1, 2021, 2,272,345 shares were added to the shares reserved for issuance under the 2020 Plan in the first of these annual increases. On January 1, 2022, 2,580,376 shares were added to the shares reserved for issuance under the 2020 Plan in the second of these annual increases.

As of December 31, 2021, 3,149,180 shares remained available for future issuance under the 2020 Plan.

In August 2020 the Company’s board of directors adopted and the Company’s stockholders approved the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which became effective September 16, 2020. The 2020 ESPP is administered by the Company’s board of directors or by a committee appointed by the board of directors. The 2020 ESPP initially provides participating employees with the opportunity to purchase up to an aggregate of 488,414 shares of common stock. The number of shares of common stock reserved for issuance under the 2020 ESPP will automatically increase on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including the fiscal year commencing on, January 1, 2030, in an amount equal to the lowest of (1) 1,953,656 shares of common stock, (2) 1% of the shares of common stock outstanding on such date, and (3) an amount determined by the board of directors. As of December 31, 2021, no offering periods have commenced under the 2020 ESPP and 488,414 shares remained available for issuance.

The Company typically grants stock options at exercise prices deemed by the Board to be equal to the fair value of the common stock at the time of grant. In the periods prior to the IPO, the fair value of the common stock was determined by the Board at each measurement date based on a variety of different factors, including the results obtained from independent third-party appraisals, the Company’s financial position and historical financial performance, the status of development of the Company’s programs, the current climate in the marketplace, the illiquid nature of the common stock, the effect of the rights and preferences of the preferred stockholders, and the prospects of a liquidity event, among others. In the periods following the IPO, the fair value is determined based upon the quoted price of the Company’s common stock.

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. For options with

service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The assumptions that the Company used to determine the grant-date fair value of options granted were as follows:


	Year Ended December 31,
	2021		2020
Expected volatility	74%		75%
Risk-free interest rate	0.82% — 1.34%		0.31% — 1.67%
Expected term (in years)	6			6
Expected dividend yield		—		—

The following table summarizes the option activity:


(in thousands, except share and per share data)	Options			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value
Outstanding January 1, 2021		6,421,589		$	6.97		9.5	$	90,112
Granted		2,240,816			15.84
Exercised		(147,499	)		3.96
Canceled		(547,156	)		9.44
Outstanding December 31, 2021		7,967,750		$	9.35		8.7	$	36,946
Options exercisable— December 31, 2021		1,872,885		$	6.13		8.7	$	13,227
Options vested or expected to vest— December 31, 2021		7,967,750		$	9.35		8.2	$	36,946

The intrinsic value of options exercised for the years ended December 31, 2021 and 2020 totaled $1.9 million and $0.2 million, respectively. The weighted-average grant date fair value of the options granted during the years ended December 31, 2021 and 2020 was $10.23 per share and $4.50 per share, respectively. As of December 31, 2021 there was $30.2 million of unrecognized compensation expense, which the Company expects to recognize over a weighted-average period of 2.5 years. In December 2021, the Company recognized compensation cost of $1.8 million related to stock options with performance-based vesting conditions for which performance was deemed probable.

A restricted stock unit (“RSU”) represents the right to receive one share of common stock upon vesting of the RSU. The Company grants RSUs with service conditions that vest in either four equal annual installments or sixteen equal quarterly installments provided that the employee remains employed with the Company. The Company also grants RSUs with performance conditions that vest upon the achievement of specified milestones. The fair value of each RSU is based on the closing price of the Company’s common stock on the date of grant. A summary of the Company’s RSU activity and related information for the 2020 Plan for the year ended December 31, 2021 is as follows:


	Number of Shares Underlying RSUs			Weighted Average Grant Date Fair Value
Issued and unvested as of January 1, 2021		403,355		$	23.60
Granted		793,629			14.76
Vested		(93,500	)		23.69
Forfeited		(46,500	)		23.35
Issued and unvested as of December 31, 2021		1,056,984		$	16.99

The weighted average grant date fair value of RSUs granted during the year ended December 31, 2020 was $23.60. As of December 31, 2021, there was $14.6 million of unrecognized compensation costs related to unvested RSUs, which are expected to be recognized over a weighted-average period of 3.4 years. In December 2021, the Company recognized compensation cost of $0.5 million related to RSUs with performance-based vesting conditions for which performance was deemed probable.

During the year ended December 31, 2018, the Company granted restricted common stock with service-based vesting conditions. Shares of unvested restricted common stock may not be sold or transferred by the holder. These restrictions lapse according to the time-based vesting conditions of each award. The grant date fair value of these shares was immaterial. The following table summarizes the Company’s restricted common stock award activity for the year ended December 31, 2021:


	Number of Restricted Shares
Issued and unvested as of January 1, 2021		370,329
Vested		(251,808	)
Forfeited		(80,380	)
Issued and unvested as of December 31, 2021		38,141

The Company recorded stock-based compensation expense in the following expense categories of its statements of operations:


	Year Ended December 31,
(in thousands)	2021		2020
Research and development	$	7,328	$	2,699
General and administrative		10,214		3,892
Total	$	17,542	$	6,591