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Stock-Based Compensation
 6 Months Ended
Jun. 30, 2026
Share-Based Payment Arrangement [Abstract]  
Stock-Based Compensation Stock-Based Compensation
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 Company’s 2015 Equity Incentive 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 June 30, 2026, the 2016 Plan had 15,084,463 shares available for future issuance, of which 6,876,693 shares were subject to outstanding option awards and restricted unit 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 June 30, 2026, the 2018 Plan had 6,481,956 shares available for future issuance, of which 5,981,072 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 June 30,Six Months Ended June 30,
2026202520262025
GrantsWeighted Average Grant Date Fair ValueGrantsWeighted Average Grant Date Fair ValueGrantsWeighted Average Grant Date Fair ValueGrantsWeighted Average Grant Date Fair Value
Stock options190,456$62.94 427,800$15.29 2,769,061$33.19 2,325,717$20.32 
Restricted stock units— — — — 125,400$30.61 — — 
2016 Employee Stock Purchase Plan
Under the Company’s Amended and Restated 2016 Employee Stock Purchase Plan (“2016 ESPP”), the Company issued and sold 19,967 shares of the Company’s common stock during the three and six months ended June 30, 2026, resulting in aggregate cash proceeds of $0.5 million.
There were no shares issued and sold during the three months ended June 30, 2025. The Company issued and sold 16,877 shares during the six months ended June 30, 2025, resulting in aggregate cash proceeds of $0.3 million.
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
June 30,		Six Months Ended
June 30,
2026202520262025
Research and development
$6,218 $4,100 $12,009 $7,612 
General and administrative7,294 5,278 14,309 10,625 
Total stock-based compensation expense
$13,512 $9,378 $26,318 $18,237 
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
June 30,		Six Months Ended
June 30,
2026202520262025
Stock Options Granted
Expected term (in years)5.935.746.025.97
Expected volatility67%74%73%76%
Risk-free interest4.16%4.02%3.88%4.38%
Dividend yield————
2016 ESPP
Expected term (in years)——0.500.50
Expected volatility——64%69%
Risk-free interest——3.59%4.23%
Dividend yield————