In December 2019, the board of directors of the Company (the “Board”) adopted the 2019 Equity Incentive Plan (the “2019 Plan”). The 2019 Plan provides for the grant of share-based awards, including stock options and restricted stock units, to employees, directors, and non-employee service providers of the Company. As of December 31, 2022, there are approximately 6,921,233 shares available for future grants. The number of shares of common stock reserved for issuance under the 2019 Plan automatically increases on January 1 of each calendar year, starting on January 1, 2020 and continuing through January 1, 2029, in an amount equal to the least of (i) 5% of the total number of shares of the Company’s capital stock issued and outstanding on the last day of the calendar month before the date of each automatic increase; (ii) 1,000,000 shares; or (iii) a lesser number of shares determined by the Company’s board of directors. Subject to this provision, the Company added 1,824,900 shares available for grant to the 2019 Plan effective January 1, 2023.

In January 2021, the Board adopted the 2021 Employee Stock Purchase Plan (the “2021 ESPP”). The purpose of the 2021 ESPP is to secure the services of new employees, to retain the services of existing employees and to provide incentives for such individuals to exert maximum efforts toward the Company’s success. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the Code for U.S. employees. As of December 31, 2022, there were approximately 791,251 shares available for future grants under the 2021 ESPP. The number of shares of common stock reserved for issuance under the 2021 ESPP automatically increases on January 1 of each calendar year, starting on January 1, 2022 and continuing through January 1, 2031, in an amount equal to the lesser of (i) 1% of the total number of shares of the Company’s capital stock issued and outstanding on the last day of the calendar month before the date of each automatic increase; or (ii) a lesser number of shares determined by the Board. Subject to this provision, the Company added 402,548 shares available for grant to the 2021 ESPP effective January 1, 2023. As of December 31, 2022, no shares of common stock had been purchased under the 2021 ESPP.

In March 2022, the Board adopted the 2022 Inducement Plan. The 2022 Inducement Plan is a non-stockholder approved stock plan under which the Company may grant equity awards to induce highly-qualified prospective officers and employees who are not currently employed by the Company to accept employment and provide them with a proprietary interest in the Company. The Company intends that the 2022 Inducement Plan be reserved for persons to whom the Company may issue securities without stockholder approval as an inducement pursuant to Nasdaq Marketplace Rule 5635(c)(4). The number of shares of common stock reserved for issuance under the 2022 Inducement Plan was initially determined to be 1,000,000 shares. As of December 31, 2022, there were 1,000,000 shares available for future grants under the 2022 Inducement Plan.

In November 2021, the Company modified certain shares of an equity award that had previously been granted to the Company’s former Chief Executive Officer. The vesting of the unvested equity award was accelerated. During the year ended December 31, 2021, stock-based compensation expense of $0.3 million was recorded in connection with this modification and is included in general and administrative expenses in the accompanying consolidated statements of operations and comprehensive loss.

A summary of the Company’s stock option activity is as follows:


	Number of Shares			Weighted Average Exercise Price		Weighted Remaining Contract Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance as of December 31, 2021		1,688,789		$	8.69		9.0	$	1,651
Granted		3,112,681			0.90
Exercised		—			—
Forfeited/Expired		(1,492,818	)		8.06
Balance as of December 31, 2022		3,308,652		$	1.65		9.4	$	—
Exercisable and vested at December 31, 2022		493,804		$	4.52		8.8	$	—
Vested and expected to vest as of December 31, 2022		3,308,652		$	1.65		9.4	$	—

The total intrinsic value of stock options exercised was $0 and $1.3 million for the years ended December 31, 2022 and 2021, respectively.

The weighted average fair value of options to purchase common stock granted in the years ended December 31, 2022 and 2021 was $0.90 and $7.19, respectively.

The fair value of each stock option award is estimated on the grant-date using the Black-Scholes option pricing model. The inputs used below are subjective and require significant judgment to determine.


	Years Ended December 31,
	2022			2021
Expected term (in years)		6.0			5.7
Risk-free interest rate		3.2	%		0.8	%
Expected volatility		81.8	%		70.2	%
Dividend rate	—%			—%
Fair value of common stock	$	0.6		$	7.2

Risk-free interest rate. The Company bases the risk‑free interest rate assumption on the U.S. Treasury’s rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued.

Expected volatility. Due to our limited operating history and lack of Company-specific historical or implied volatility, the expected volatility assumption was determined by examining the historical volatilities of a group of industry peers whose share prices are publicly available, and is calculated based on a period consistent with the expected term of the option.

Expected term. The expected term represents the period of time that options are expected to be outstanding. Because the Company does not have historical exercise behavior, it determines the expected life assumption using the simplified method, which is an average of the contractual term of the option and its vesting period.

Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends.

The allocation of stock-based compensation expense was as follows (in thousands):


	Years Ended December 31,
	2022		2021
Research and development	$	638	$	2,545
General and administrative		1,333		1,573
Total stock-based compensation expense	$	1,971	$	4,118

At December 31, 2022, the unrecognized compensation cost related to outstanding time-based options was $2.0 million and is expected to be recognized as expense over approximately 3.2 years.