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Stock Plans and Stock-Based Compensation
 12 Months Ended
Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]  
Stock Plans and Stock-Based Compensation Stock Plans and Stock-Based Compensation
As of December 31, 2024, the Company had two shareholder-approved, stock-based compensation plans: (i) the Fifth Amended and Restated 2010 Stock Incentive Plan (“2010 Plan”) and (ii) the Amended and Restated 2010 Employee Stock Purchase Plan, (“ESPP”). New employees are generally issued options as an inducement equity award under Nasdaq Listing Rule 5635(c)(4) outside of the 2010 Plan (“Inducement Awards”).
The Fifth Amended and Restated 2010 Stock Incentive Plan
The 2010 Plan permits the granting of incentive and non-qualified stock options and stock awards to employees, officers, directors, and consultants of the Company and its subsidiaries at prices determined by the Company’s board of directors. In May 2024, the Company's stockholders approved the amendment and restatement of the 2010 Plan to reserve an additional 942,100 shares of common stock for issuance under the 2010 Plan. The Company can issue up to 2,101,600 shares of its common stock pursuant to awards granted under the 2010 Plan. Options vest and become exercisable based on a schedule determined by the board of directors and expire up to ten years from the date of grant. The 2010 Plan uses a “fungible share” concept under which each share of stock subject to awards granted as options and stock appreciation rights (“SARs”), will cause one share per share under the award to be removed from the available share pool, while each share of stock subject to awards granted as restricted stock, restricted stock units, other stock-based awards or performance awards where the price charged for the award is less than 100% of the fair market value of the Company’s common stock will cause 1.3 shares per share under the award to be removed from the available share pool. As of December 31, 2024, the Company has only granted options to purchase shares of the Company’s common stock with an exercise price equal to the closing market price of the Company’s common stock on the Nasdaq Capital Market on the grant date and issued restricted stock awards at no cost to Company employees, excluding officers.
During the year ended December 31, 2024, the Company’s board of directors granted options to purchase 457,670 shares of the Company’s common stock to officers and employees of the Company under the 2010 Plan. These options vest and become exercisable as to 25% of the shares underlying the award after the first year and as to an additional 6.25% of the shares underlying the award in each subsequent quarter, based upon continued employment over a four-year period, and are exercisable at a price equal to the closing price of the Company’s common stock on the grant date.
During the year ended December 31, 2024, the Company’s board of directors granted options to its non-employee directors to purchase 21,250 shares of common stock under the 2010 Plan, which will vest and become exercisable in one year from the date of grant. These options were granted at an exercise price that equaled the closing market price of the Company’s common stock on the grant date.
During the year ended December 31, 2023, the Company’s board of directors granted restricted stock awards ("RSAs"), for an aggregate amount of 117,000 shares to the employees of the Company, excluding officers, under the 2010 Plan. These RSAs vest as to 50% of the shares underlying the award on the first anniversary of the date of the grant and 50% after the second anniversary, based upon continued employment.
As of December 31, 2024, 912,598 shares remained available for grant under the 2010 Plan.
Inducement Awards
The Company grants Inducement Awards to certain new employees. These options generally vest as to 25% of the shares underlying the option on the first anniversary of the grant date, and as to an additional 6.25% of the shares underlying the option on each successive quarter thereafter. During the year ended December 31, 2024, the Company’s board of directors granted Inducement Awards to purchase 39,350 shares of common stock. These options were granted at an exercise price that equaled the closing market price of the Company’s common stock on grant date.
Stock Options
A summary of stock option activity under the 2010 Plan and Inducement Awards are summarized as follows:
Number of
Options		Weighted
Average
Exercise
Price per
Share		Weighted
Average
Remaining Contractual Life		Aggregate Intrinsic Value
(000's)
Outstanding, December 31, 2023
840,880 $47.58 7.16$91 
Granted518,270 11.39 
Exercised— — 
Canceled(198,899)45.82 
Outstanding, December 31, 2024
1,160,251 $33.44 7.19$— 
Exercisable at December 31, 2024
575,688 $55.36 5.50$— 
Vested and unvested expected to vest at December 31, 2024
1,160,251 $33.44 7.19$— 
The weighted average grant date fair values of stock options granted during the years ended December 31, 2024 and 2023 were $9.50 and $11.70, respectively, and were calculated using the following estimated assumptions under the Black-Scholes option pricing model:
For the Year Ended
December 31,
20242023
Expected term (years)6.05.5
Risk-free interest rate
3.9-4.5%
3.5-4.7%
Expected volatility
114-116%
115-116%
Expected dividend yieldNoneNone
As of December 31, 2024, there was approximately $5.7 million of unrecognized compensation cost related to unvested employee stock option awards outstanding, which is expected to be recognized as expense over a weighted average period of 2.3 years. There were no employee stock options exercised during the year ended December 31, 2024.
Restricted Stock Awards
The following table presents a summary of outstanding RSAs under the 2010 Plan as of December 31, 2024:
Number of
Shares		Weighted
Average
Grant Date Fair Value
Unvested, December 31, 2023
110,500 $18.20 
Awarded— — 
Vested(65,988)18.20 
Forfeited(4,375)18.20 
Unvested, December 31, 2024
40,137 $18.20 
As of December 31, 2024, there were 40,137 shares outstanding underlying RSAs that are expected to vest. As of December 31, 2024, there was $0.3 million of unrecognized compensation costs related to RSAs, which are expected to be recognized as expense over a remaining weighted average period of 0.4 years. The fair value of RSAs that vested during the year ended December 31, 2024 was $1.0 million. There were no RSAs that vested during the year ended December 31, 2023. The weighted average grant date fair value of RSAs granted during the year ended December 31, 2023 was $18.20.
Amended and Restated 2010 Employee Stock Purchase Plan
In May 2024, the Company's stockholders approved an amendment to the ESPP to reserve an additional 400,000 shares of common stock for issuance under the ESPP. The Company has reserved 500,000 shares of common stock for issuance under the ESPP. Eligible employees may purchase shares of the Company’s common stock at 85% of the lower closing market price of the common stock at the beginning of the enrollment period or ending date of the any purchase period within a two-year enrollment period, as defined. The Company has four six-month purchase periods per each two-year enrollment period. If, within any one of the four purchase periods in an enrollment period, the purchase period ending stock price is lower than the stock price at the beginning of the enrollment period, the two-year enrollment resets at the new lower stock price. During the
year ended December 31, 2024, 32,168 shares were issued under the ESPP. As of December 31, 2024, there were 394,463 shares available for future purchase under the ESPP.
For the years ended December 31, 2024 and 2023, the Company recorded compensation expense related to its ESPP and calculated the fair value of shares expected to be purchased under the ESPP using the Black-Scholes model.
Stock-Based Compensation Expense
For the years ended December 31, 2024 and 2023, the Company recorded stock-based compensation expense to the following line items in its costs and expenses section of the Consolidated Statements of Operations and Comprehensive Loss: 
For the Year Ended December 31,
20242023
Research and development expenses$2,760 $2,770 
General and administrative expenses3,167 3,230 
Total stock-based compensation expense$5,927 $6,000 
No income tax benefits have been recorded for the years ended December 31, 2024 and 2023, as the Company has recorded a full valuation allowance and management has concluded that it is more likely than not that the net deferred tax assets will not be realized (see Note 13, Income Taxes).