Stock-Based Compensation

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

2016 Equity Incentive Plan

The Company's 2016 Equity Incentive Plan (the “2016 Plan”) became effective in April 2016 and serves as the successor to the 2015 Plan. Under the 2016 Plan, the Company may grant stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance awards, and stock bonuses. The 2016 Plan, as amended, provides for an automatic increase in the number of shares reserved for issuance thereunder on January 1 of each year for the remaining term of the plan equal to (a) 5.0% of the number of issued and outstanding shares of common stock (including such shares issuable pursuant to the exercise or conversion, as applicable, of any outstanding pre-funded warrants and nonvoting convertible preferred stock) on December 31 of the immediately preceding year, or (b) a lesser amount as approved by the board each year

(the “Evergreen Provision”). As a result of the Evergreen Provision, on January 1, 2026 and 2025, an additional 4,711,544 and 3,814,905 shares, respectively, became available for issuance under the 2016 Plan.

As of March 31, 2026, the 2016 Plan had 15,316,247 shares available for future issuance, of which 7,064,379 shares were subject to outstanding option awards.

2018 Equity Inducement Plan

The 2018 Equity Inducement Plan (“2018 Plan”) became effective in February 2018.

During the second quarter of 2025, the Company amended the 2018 Plan to increase the number of shares of common stock reserved for issuance by 750,000. After this amendment and as of March 31, 2026, the 2018 Plan had 7,317,800 shares available for future issuance, of which 6,680,012 shares were subject to outstanding option awards and restricted unit awards.

Service-based awards granted under the 2018 Plan and 2016 Plan generally vest over four years and expire after ten years, although awards have been granted with vesting terms less than four years. Under the 2016 Plan and 2018 Plan, the Company may grant stock-based awards with service conditions, performance conditions, and market conditions.

The following table summarizes the Company’s stock awards granted under all equity incentive and inducement plans for each of the periods indicated:


	Three Months Ended March 31,
	2026			2025
	Grants	Weighted Average Grant Date Fair Value		Grants	Weighted Average Grant Date Fair Value
Stock options	2,578,605	$	31.00	1,897,917	$	21.45
Restricted stock units	125,400	$	30.61	—	—

Parapyre Option Obligation

As of March 31, 2026, a total of 1,532,591 warrants with a weighted-average exercise price of $22.49 had been issued to Parapyre under the Parapyre Option Obligation. As of March 31, 2026, none of the warrants issued under the Parapyre Option Obligation have been exercised and all remain outstanding. There are no ongoing obligations under the Parapyre Option Obligation as of December 31, 2024.

2016 Employee Stock Purchase Plan

Under the Company’s 2016 Employee Stock Purchase Plan (“2016 ESPP”), the Company issued and sold 16,877 shares during the three months ended March 31, 2025, resulting in aggregate cash proceeds of $0.3 million, respectively. There were no ESPP sales during the three months ended March 31, 2026.

Stock-based Compensation Expense

Total stock-based compensation expense recognized from the Company’s equity incentive plans, 2018 Plan and 2016 ESPP during the periods presented was as follows (in thousands):


	Three Months Ended March 31,
	2026		2025
Research and development	$	5,791	$	3,512
General and administrative	7,015		5,347
Total stock-based compensation expense	$	12,806	$	8,859

The following table summarizes the weighted-average Black-Scholes option pricing model assumptions used to estimate the fair value of stock options granted under the Company's equity incentive plans, and the shares purchased under the 2016 ESPP during the periods presented:


	Three Months Ended March 31,
	2026	2025
Stock Options Granted
Expected term (in years)	6.03	6.03
Expected volatility	73%	76%
Risk-free interest	3.85%	4.46%
Dividend yield	—	—

2016 ESPP
Expected term (in years)	—	0.50
Expected volatility	—	69%
Risk-free interest	—	4.23%
Dividend yield	—	—