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Stock Based Compensation
 3 Months Ended
Mar. 31, 2025
Share-Based Payment Arrangement [Abstract]  
Stock Based Compensation Stock Based Compensation
The Company has a 2013 Stock Option Plan (the “2013 Plan”), which is administered by the Compensation Committee of the Company’s board of directors. Under the 2013 Plan, stock options to purchase shares of common stock could be granted to eligible employees, officers, directors and consultants of the Company. The 2013 Plan terminated in August 2023 on the tenth anniversary of the 2013 Plan’s date of adoption by the board. No new awards were made under the 2013 Plan after such termination date, but awards previously granted may extend beyond such date.
In 2021, the Company established the 2021 Stock Incentive Plan (the “2021 Plan”), authorizing the granting of equity awards for the issuance of up to 3,000,000 shares of common stock. Upon adoption of the 2021 Plan, no more shares would be issued under the 2013 Plan. Starting on January 1, 2022, the shares authorized under the 2021 Plan shall have an annual increase of the lessor of (a) 3.5% of the aggregate number of shares of common stock outstanding on the final day of the preceding calendar year, or (b) such smaller amount as determined by the Board. On January 1, 2023 and January 1, 2024, an additional 238,700 and 479,828 shares were authorized under the 2021 Plan. On January 1, 2025, an additional 529,300 shares were authorized under the 2021 Plan. As of March 31, 2025, 2,455,011 shares were available for issuance under the 2021 Plan.
The Company recorded total stock-based compensation for its outstanding stock options and warrants in its Statements of Operations as follows (in thousands):
Three Months Ended March 31,
20252024
Research and development$160 $566 
General and administrative275 589 
Total stock-based compensation expense$435 $1,155 

Stock options
The following table summarizes the range of assumptions used to estimate the fair value of stock options issued using the Black-Scholes-Merton option pricing model:
Three Months Ended March 31,
20252024
Stock pricen/a$5.19
Exercise pricen/a$5.19
Expected volatilityn/a97.06%
Risk free interest ratesn/a4.12%
Expected term (years)n/a
5 to 6.25
The Company did not issue stock options for the three months ended March 31, 2025. For the three months ended March 31, 2024, a dividend yield of 0% was used because the Company has not historically paid and does not intend to pay a dividend on common stock in the foreseeable future. The expected stock price volatility assumption was estimated based on the historical volatilities for industry peers, as the Company had no active market for its stock prior to the IPO and limited history for issuance price of its stock. The risk-free rate assumption is determined using the yield currently available on U.S. Treasury zero coupon issues with a remaining term commensurate with the expected term of the award. The expected term of the option represents the period the options are expected to be outstanding.
The following table summarizes the activity for stock options for the three months ended March 31, 2025:
OptionsWeighted-
Average
Exercise Price		Weighted Average
Remaining
Contractual Term
(in years)		Aggregate
Intrinsic
Value (in
thousands)
Outstanding at December 31, 20242,587,129 $6.14 7.9$— 
Issued— $— 
Exercised— $— 
Forfeited and cancelled(44,062)$3.55 
Outstanding at March 31, 20252,543,067 $6.18 7.6$— 
Exercisable at March 31, 20251,435,229 $7.40 6.4$— 

All options expire 10 years from date of grant. Options outstanding begin to expire in September 2025. Options that were granted to employees and consultants have vesting periods that vary by award to recipient and range from immediate vesting to a period of up to 4 years.
As of March 31, 2025, total unrecognized compensation cost related to options was approximately $4.0 million and is expected to be recognized over the remaining weighted average service period of 2.5 years.
Warrants
The following table summarizes the range of assumptions used to estimate the fair value of warrants issued using the Black-Scholes-Merton option pricing model:
Three Months Ended March 31,
20252024
Stock pricen/a
$5.19
Exercise pricen/a
$5.19
Expected volatilityn/a
97.06%
Risk free interest ratesn/a
4.12%
Expected term (years)n/a
6.25
The Company did not issue warrants for the three months ended March 31, 2025. For the three months ended March 31, 2024, a dividend yield of 0% was used because the Company has not historically paid and does not intend to pay a dividend on common stock in the foreseeable future. The expected stock price volatility assumption was estimated based on the historical volatilities for industry peers, as the Company had no active market for its stock prior to the IPO and limited history for issuance price of its stock. The risk-free rate assumption is determined using the yield currently available on U.S. Treasury zero coupon issues with a remaining term commensurate with the expected term of the award. The expected term of the warrant represents the period the warrants are expected to be outstanding.
The following table summarizes the activity for warrants for the three months ended March 31, 2025:
WarrantsWeighted-
Average
Exercise Price		Weighted Average
Remaining Contractual Term
(in years)		Aggregate
Intrinsic
Value (in
thousands)
Outstanding at December 31, 20242,041,563 $4.32 4.7$— 
Issued— $— 
Exercised— $— 
Forfeited and cancelled— $— 
Outstanding at March 31, 20252,041,563 $4.32 4.4$— 
Exercisable at March 31, 2025753,450 $6.50 3.2$— 
All warrants outstanding are exercisable for purchase of common stock.
As of March 31, 2025, total unrecognized compensation cost related to warrants was approximately $0.2 million and is expected to be recognized over the remaining weighted average service period of 2.6 years.

Restricted Stock
In September 2024, the Company issued 11,750 restricted shares of its common stock (the “Restricted Stock”) to a consultant as compensation for its services to the Company through the end October 2024 valued at $51,000. The Restricted Stock included a restricted legend for a period of at least six months from the date of issuance. The six-month period has elapsed, and the Restricted Stock is no longer restricted.