Stock-Based Compensation

6 Months Ended

Jun. 30, 2026

Share-Based Payment Arrangement [Abstract]

As of June 30, 2026, there were 8,542,710 shares subject to outstanding options, restricted stock units (RSUs) and performance restricted stock units (PSUs) under the Amended and Restated 2016 Equity Incentive Plan (2016 Plan). No awards remain in effect under the 2006 Equity Incentive Plan (2006 Plan, and together with the 2016 Plan, Plans), which expired by its terms in April 2016. In June 2016, the Company’s stockholders approved the 2016 Plan. The 2016 Plan has been amended a number of times since to increase the number of shares reserved for issuance, among other administrative changes, including, but not limited to, an amendment to eliminate its term. Each of the amendments to the 2016 Plan was approved by the Company’s stockholders. There is a total of 20,690,000 shares of common stock authorized for issuance under the 2016 Plan, 5,704,840 shares of which remained available for future grant as of June 30, 2026.

Stock Options

The Company has granted option awards under the Plans with service conditions (service option awards) that are subject to terms and conditions established by the compensation committee of the board of directors. Service option awards have 10-year contractual terms. Service option awards granted to employees and new directors, upon their election, vest and become exercisable over four years, with the first 25% of the shares subject to service option awards vesting on the first anniversary of the grant date and the remaining 75% of the shares subject to the service option awards in 36 equal monthly installments thereafter. Subsequent annual service option awards granted to directors vest and become exercisable in full on the first anniversary of the grant date. Service option awards granted to executive officers and certain other employees provide for partial acceleration of vesting if the executive officer or employee is subject to an involuntary termination, and full acceleration of vesting if the executive officer or employee is subject to an involuntary termination within 24 months after a change in control of the Company. Service option awards granted to directors provide for accelerated vesting if there is a change in control of the Company or if the director’s service terminates as a result of the director’s death or total and permanent disability.

As of June 30, 2026, $0.4 million of unrecognized compensation costs related to unvested service option awards are expected to be recognized over a weighted average period of 0.4 years. No option awards are classified as a liability as of June 30, 2026.

A summary of option activity under the Plans for the six months ended June 30, 2026 follows:


(in thousands, except for share and per share amounts)	Number of Shares	Weighted Average Exercise Price at Grant Date		Weighted Average Remaining Term (Years)	Aggregate Intrinsic Value
Outstanding at December 31, 2025	4,490,324	$	12.75	4.74	$	2,698

Forfeited	(17,762)	7.05
Expired	(297,330)	8.09

Outstanding at June 30, 2026	4,175,232	13.10		4.56	136
Exercisable at June 30, 2026	4,057,908	13.28		4.50	136
Vested and expected to vest at June 30, 2026	4,174,450	13.11		4.56	136

There were no options granted during the six months ended June 30, 2026 and 2025. There were no options exercised for the six months ended June 30, 2026 and 2025.

Restricted Stock Units

An RSU is a stock award that entitles the holder to receive shares of the Company’s common stock as the award vests. The fair value of each RSU is based on the closing price of the Company’s stock on the date of grant. The Company has granted RSUs under the Plans with service conditions (service RSUs) that are subject to terms and conditions established by the compensation committee of the board of directors. Service RSUs granted to employees and new directors, upon their election, vest in four equal annual installments. Subsequent annual service RSUs granted to directors vest on the first anniversary of the date of grant. Service RSUs granted to executive officers and certain other employees provide for accelerated vesting if the executive officer or employee is subject to an involuntary termination within 24 months after a change in control. Service RSUs granted to directors provide for accelerated vesting if there is a change in control of the Company.

As of June 30, 2026, $19.5 million of unrecognized compensation costs related to unvested service RSUs are expected to be recognized over a weighted average period of 1.9 years. No RSUs are classified as a liability as of June 30, 2026.

A summary of RSU activity for the 2016 Plan for the six months ended June 30, 2026 is as follows:


	Number of Shares	Weighted Average Grant Date Fair Value
Unvested at December 31, 2025	3,476,509	$	4.99
Granted	2,183,701	6.10
Forfeited	(304,675)	5.19
Vested	(1,353,057)	5.50
Unvested at June 30, 2026	4,002,478	5.41

The total fair value of the 1,353,057 RSUs that vested during the six months ended June 30, 2026 was $7.4 million.

Performance Restricted Stock Units

In the first quarter of 2026, the compensation committee of the board of directors granted PSUs under the 2016 Plan to the Company’s executive officers. The PSUs entitle each employee to earn a number of shares of the Company’s common stock ranging from 0% to 150% of the target number of PSUs granted, based on the Company’s Total Shareholder Return (TSR) relative to the TSR of the companies comprising the Nasdaq Biotechnology Index (Relative TSR), over the three-year performance period beginning on December 31, 2025 and ending on December 31, 2028 (the Performance Period), subject to the executive’s continued employment through the compensation committee of the board of director’s certification of performance following the end of the Performance Period. Following the end of the Performance Period, the compensation committee of the board of directors will determine the extent to which the applicable performance goals have been achieved and will determine the number of PSUs, if any, that have been earned, and any such earned PSUs will vest on March 1, 2029. The PSUs provide for accelerated vesting in certain scenarios, including in the event that the executive is subject to an involuntary termination within 24 months after a change in control.

As of June 30, 2026, $2.7 million of unrecognized compensation costs related to unvested PSUs are expected to be recognized over a weighted average period of 2.7 years. No PSUs are classified as a liability as of June 30, 2026.

A summary of PSU activity for the 2016 Plan for the six months ended June 30, 2026, based on award at target, is as follows:


	Number of Shares	Weighted Average Grant Date Fair Value
Unvested at December 31, 2025	—	$	—
Granted	405,000	8.03
Forfeited	(40,000)	8.03

Unvested at June 30, 2026	365,000	8.03

No PSUs vested during the six months ended June 30, 2026.

Stock-Based Compensation Expense

Stock-based compensation expense recognized for the three and six months ended June 30, 2026 and 2025 was comprised of the following:


	Three Months Ended				Six Months Ended
(in thousands)	June 30, 2026		June 30, 2025		June 30, 2026		June 30, 2025
Research and development	$	583	$	596	$	1,184	$	1,361
Selling, general and administrative	1,524		1,510		3,486		3,716
Total stock-based compensation expense	$	2,107	$	2,106	$	4,670	$	5,077

The fair value of each option award is estimated on the date of grant using the Black-Scholes-Merton option pricing model. Expected volatility rates are based on the historical volatility of the Company’s publicly traded common stock and other factors. The expected terms are determined based on a combination of historical exercise data and hypothetical exercise data for unexercised stock options. The risk-free interest rates are based on the U.S. Treasury yield for a period consistent with the expected term of the option in effect at the time of the grant. The Company has never paid cash dividends to its stockholders and does not plan to pay dividends in the foreseeable future. There were no options granted during the six months ended June 30, 2026 and 2025.

The fair value of each PSU is estimated on the date of grant using a Monte Carlo model because the performance target is based on a market condition. Expense related to these PSUs is recognized ratably over the three-year measurement period. The expected volatility rate is based on the historical volatility of the Company’s publicly traded common stock and other factors. The expected term is determined based on the remaining performance period of the award. The risk-free interest rate is based on the U.S. Treasury yield for a period consistent with the expected term of the PSUs in effect at the time of the grant. The Company has never paid cash dividends to its stockholders and does not plan to pay dividends in the foreseeable future. Assumptions used in the Monte Carlo model for PSUs granted during the six months ended June 30, 2026 were as follows:


	Six Months Ended
	June 30, 2026

Expected dividend yield	—	%
Expected volatility of the Company	61	%
Remaining performance period (years)	2.87
Risk-free rate	3.44	%