In 2014, the Company’s Board of Directors (the “Board”) and stockholders approved and adopted the Company’s 2014 Stock Plan (the “2014 Plan”). The 2014 Plan permitted the grant of options and restricted stock awards (including restricted stock purchase rights and restricted stock bonus awards). The 2014 Plan was terminated on the date the Company’s 2020 Equity Incentive Plan (the “2020 Plan”), which is described

below, became effective, and since that date, no additional awards have been or will be made pursuant to the 2014 Plan. However, any outstanding awards granted under the 2014 Plan will remain outstanding, subject to the terms of the 2014 Plan award agreements, until such outstanding options are exercised or until any awards terminate or expire by their terms.

In 2020, the Board and the Company’s stockholders approved and adopted the 2020 Plan. The 2020 Plan permits the grant of options, restricted stock awards, stock appreciation rights, restricted stock unit awards, performance awards, and other awards. The maximum number of shares of common stock that were initially issuable under the 2020 Plan was a number not to exceed 6,494,510 shares of the Company’s common stock, which is the sum of (i) 2,152,080 new shares, plus (ii) an additional number of shares not to exceed 4,342,430 shares, consisting of any shares of the Company’s common stock subject to outstanding stock options or other stock awards granted under the 2014 Plan that, on or after the date on which the 2020 Plan became effective, terminated or expired prior to exercise or settlement; were not issued because the award was settled in cash; were forfeited because of the failure to vest; or were reacquired or withheld (or not issued) to satisfy a tax withholding obligation or the purchase or exercise price. In addition, the number of shares of the Company’s common stock reserved for issuance under the 2020 Plan automatically increases on January 1 of each year for a period of ten years, beginning on January 1, 2021 and continuing through January 1, 2030, in an amount equal to the lesser of (1) 5% of the total number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding year, or (2) a lesser number of shares determined by the Board no later than December 31 of the immediately preceding year.

In 2022, the Board approved and adopted the Company’s 2022 Inducement Plan (the “2022 Inducement Plan”). Under the 2022 Inducement Plan, initially 2,000,000 shares of common stock were reserved for issuance. The 2022 Inducement Plan permits the grant of options, restricted stock awards, stock appreciation rights, restricted stock unit awards, performance awards, and other awards.

The exercise price for each option and stock appreciation right shall be established at the discretion of the Board, provided that the exercise price of a stock option will not be less than 100% of the fair market value of the Company’s common stock on the date of grant. Specific vesting for stock options and stock appreciation rights is service related and determined in each award agreement, where stock options and stock appreciation rights are fully vested at the grant date or follow a graded vesting schedule. Stock options and stock appreciation rights granted under the plans generally expire ten years after the date of grant.

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company lacks company-specific historical and implied volatility information. Therefore, it estimated its expected stock volatility based on the historical volatility of a publicly traded set of peer companies in addition to its own historical volatility. 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 expected term of stock options granted to nonemployees is equal to the contractual term of the option award. 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 0% since 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 estimated grant-date fair value of stock options granted to employees and directors under the 2020 Plan and the 2022 Inducement Plan were as follows, presented as a weighted average:


	September 30,			September 30,
	2024			2023
Risk-free interest rate		3.92	%		3.56	%
Expected term (in years)		6.03			6.03
Expected volatility		85.10	%		86.71	%
Expected dividend yield		—			—

The following table summarizes the stock option activity under the 2014 Plan, the 2020 Plan and the 2022 Inducement Plan:


						Weighted
				Weighted		Average
				Average		Remaining		Aggregate
	Number of			Exercise		Contractual		Intrinsic
	Shares			Price		Term		Value
						(in years)		(in thousands)
Outstanding as of December 31, 2023		8,670,742		$	8.52		7.60	$		61,749
Granted		3,297,550			14.35	—			—
Exercised (1)		(389,043	)		3.64	—			—
Forfeited		(205,201	)		15.83	—			—
Outstanding as of September 30, 2024		11,374,048		$	10.06		7.30	$		44,235

Options vested and exercisable as of September 30, 2024		6,033,473		$	9.04		6.04	$		31,002
Options expected to vest as of September 30, 2024		5,340,575		$	11.22		8.71	$		13,233

(1)

Exercised amount includes shares returned for taxes withheld for exercise and net transactions.

The following table summarizes the restricted stock activity under the 2014 Plan during the nine months ended September 30, 2024:


	Number of Shares			Grant Date Fair Value
Unvested restricted stock as of December 31, 2023		92,659		$	2.40
Granted	—
Vested		(92,659	)		2.40
Forfeited	—
Unvested restricted stock as of September 30, 2024		—		$	—

In November 2022, the Company granted to certain employees 710,000 shares of performance-based restricted stock unit awards (the “PSUs”) under the 2020 Plan as consideration for services subject to performance conditions with a fair value based on the closing price of the underlying common stock on the date of grant. Pursuant to the terms of the PSUs, 65% of each PSU vests upon certification by the Compensation Committee of the Company of achieving a pre-determined performance goal by June 30, 2024, and, 35% of each PSU vests upon certification by the Compensation Committee of the Company of achieving a pre-determined performance goal by June 30, 2024. The performance goal related to the 35% tranche of the PSUs was met and related stock-based compensation expense was recorded in 2023. In June 2024, pursuant to the terms of the PSUs, the Compensation Committee of the Company approved an extension of the achievement of the performance goal related to the 65% tranche of the PSUs from June 30, 2024 to December 31, 2024.

Expense recognition for PSUs commences when it is determined that attainment of the performance goal is met. During the three and nine months ended September 30, 2024, no performance goal was met, and therefore, no related stock-based compensation expense was recorded.

The following table summarizes the performance-based restricted stock activity under the 2020 plan during the nine months ended September 30, 2024:


	Number of Shares		Grant Date Fair Value
Outstanding as of December 31, 2023		403,000	$	3.38
Granted		—
Vested		—
Forfeited		—
Outstanding as of September 30, 2024		403,000	$	3.38

In 2020, the Board and the Company’s stockholders approved and adopted the ESPP. The ESPP permits eligible employees who elect to participate in an offering under the ESPP to have up to 15% of their eligible earnings withheld, subject to certain limitations, to purchase shares of common stock pursuant to the ESPP. The price of the common stock purchased under the ESPP is equal to the lesser of (i) 85% of the fair market value of a share of the Company’s common stock on the first day of an offering; or (ii) 85% of the fair market value of a share of the Company’s common stock on the date of purchase. Each offering period is not to exceed 27 months and will include one or more purchase periods (each a “Purchase Period”) as approved by the Board in the offering. A total of 430,416 shares of common stock were initially reserved for issuance pursuant to the ESPP. Subsequently, the number of shares of the Company’s common stock reserved for issuance under the ESPP automatically increases on January 1 of each year for a period of up to ten years, commencing on January 1, 2021 and continuing through January 1, 2030, in amount equal to the lesser of (i) 1% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, (ii) 860,832 shares of common stock, or (iii) a lesser number of shares determined by the Board no later than December 31 of the preceding calendar year.

The ESPP is a compensatory plan as defined by the authoritative guidance for stock-based compensation. The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock offered under the ESPP. Stock-based compensation expense related to the ESPP was $0.1 million and $0.4 million for the three and nine months ended September 30, 2024, respectively.

Stock-based compensation expense related to awards granted under the 2014 Plan, the 2020 Plan, the ESPP and the 2022 Inducement Plan was classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development	$	4,280	$	2,801	$	11,925	$	8,858
General and administrative		1,346		1,304		4,334		4,047
Total	$	5,626	$	4,105	$	16,259	$	12,905