Note 12. Stock-Based Compensation
Stock-Based Compensation Plans
In December 2017, the Company adopted the 2017 Employee, Director and Consultant Equity Incentive Plan (the “2017 Plan”), under which it may grant incentive stock options, non-qualified stock options, RSUs, and other stock-based awards. As of December 31, 2017, the 2017 Plan allowed for the issuance of (1) up to 1.0 million shares of common stock and (2) up to 2.5 million shares of common stock represented by awards granted under the 2007 Stock Option and Grant Plan (which was terminated upon completion of the Company’s initial public offering) that were forfeited, expired, or cancelled without delivery of shares or which result in the forfeiture of shares of common stock back to the Company on or
after the date the 2017 Plan became effective. The 2017 Plan contains an “evergreen” provision, which allows for an annual increase in the number of shares of common stock available for issuance under the 2017 Plan on the first day of each fiscal year during the period beginning in 2019 and ending in 2027. The annual increase is equal to the lowest of (1) 4% of the number of shares of common stock outstanding as of such date and (2) an amount determined by the Company’s board of directors or compensation committee. As of December 31, 2025, 6.2 million shares were outstanding and there were 4.9 million shares available for grant under the 2017 Plan.
In December 2017, the Company adopted the 2017 Employee Stock Purchase Plan (the “2017 ESPP”). As of December 31, 2019, the 2017 ESPP allowed for the issuance of up to 0.6 million shares of common stock. The 2017 ESPP contains an “evergreen” provision, which allows for an increase in the number of shares under the plan on the first day of each fiscal year beginning with 2018 and ending in 2027. The increase is equal to the lowest of: (1) 1% of the number of shares of common stock outstanding on the last day of the immediately preceding fiscal year and (2) an amount determined by the Company’s board of directors or compensation committee. As of December 31, 2025, 1.9 million shares were available for grant under the 2017 ESPP. The 2017 ESPP provides for six-month offering periods commencing and ending on March 1 through August 31, and September 1 through February 28. During the years ended December 31, 2025, 2024, and 2023, employees purchased 0.2 million, 0.1 million, and 0.1 million shares, respectively, of the Company’s common stock pursuant to the 2017 ESPP.
In July 2025, the Company adopted the Quanterix Corporation Restricted Stock Unit Inducement Awards Plan (the "Inducement Plan"). The Inducement Plan allows for issuance of up to 0.5 million shares of Quanterix common stock, consisting of: (i) up to 0.2 million shares of Quanterix common stock that may be become available for issuance again under the 2021 Akoya Equity Incentive Plan pursuant to the terms of such plan and (ii) 0.3 million shares of Quanterix common stock issuable upon vesting of restricted stock units granted to Akoya employees as an inducement to employment with Quanterix following the Merger.
In November 2025, the Company adopted the 2025 Inducement Plan which allows for issuance of up to 0.9 million shares of Quanterix Common Stock, par value $0.001 per share.
In accordance with Nasdaq listing rules, equity awards issued under the Inducement Plan and the 2025 Inducement Plan are restricted to individuals who are not already employees or directors of the Company.
Stock Options
Under the 2017 Plan, stock options may not be granted with exercise prices of less than fair market value on the date of the grant. Options generally vest ratably over a four-year period with 25% vesting on the first anniversary and the remaining 75% vesting ratably on a monthly basis over the remaining three years. These options expire ten years after the grant date.
Stock option activity for the year ended December 31, 2025 is presented below (in thousands, except per share and contractual life amounts): | | | | | | | | | | | | | | | | | | | | | | | |
| Number of options | | Weighted-average exercise price per share | | Weighted-average remaining contractual life (in years) | | Aggregate intrinsic value |
| Outstanding at December 31, 2024 | 3,563 | | | $ | 19.94 | | | 7.7 | | $ | 678 | |
| Granted | 2,676 | | | 8.21 | | | | | |
| Exercised | (4) | | | 3.12 | | | | | |
| Forfeited/expired | (1,355) | | | 15.04 | | | | | |
| Outstanding at December 31, 2025 | 4,880 | | | $ | 14.89 | | | 7.9 | | $ | 170 | |
| Exercisable at December 31, 2025 | 2,042 | | | $ | 20.06 | | | 6.5 | | $ | 12 | |
| Vested and expected to vest at December 31, 2025 | 4,880 | | | $ | 14.89 | | | 7.9 | | $ | 170 | |
The weighted average grant-date fair value per share of awards granted was $5.85 in 2025, $14.43 in 2024, and $10.63 in 2023. The total intrinsic value of stock options exercised was not material in 2025, $1.9 million in 2024, and $1.9 million in 2023.
Restricted Stock Units
RSUs represent the right to receive shares of common stock upon meeting specified vesting requirements. Shares are delivered to the grantee upon vesting, less shares for the payment of withholding taxes. RSU activity for the year ended December 31, 2025 is presented below (in thousands, except per share amounts): | | | | | | | | | | | |
| Number of shares | | Weighted-average grant date fair value per share |
| Unvested as of December 31, 2024 | 1,115 | | | $ | 18.55 | |
| Assumed through acquisition of Akoya (1) | 253 | | | 6.54 | |
| Granted | 1,619 | | | 7.76 | |
| Vested | (677) | | | 10.44 | |
| Forfeited | (735) | | | 13.58 | |
| Unvested as of December 31, 2025 | 1,575 | | | $ | 11.33 | |
| Expected to convert at December 31, 2025 | 1,575 | | | $ | 11.33 | |
(1)Refer to Note 3 - Acquisitions.
The weighted average grant-date fair value per share of awards granted was $7.76 in 2025, $21.51 in 2024, and $15.90 in 2023.The total fair value of shares that vested was $13.0 million in 2025, $10.3 million in 2024, and $10.4 million in 2023.
Stock-Based Compensation Expense
Stock-based compensation expense was recorded in the following categories on the Consolidated Statements of Operations (in thousands): | | | | | | | | | | | | | | | | | |
| Year Ended December 31, |
| 2025 | | 2024 | | 2023 |
| Cost of product revenue | $ | 901 | | | $ | 1,132 | | | $ | 839 | |
| Cost of service and other revenue | 970 | | | 1,142 | | | 1,124 | |
| Research and development | 2,178 | | | 2,117 | | | 1,713 | |
| Selling, general and administrative | 16,669 | | | 15,596 | | | 13,147 | |
| Total stock-based compensation expense | $ | 20,718 | | | $ | 19,987 | | | $ | 16,823 | |
As of December 31, 2025, there was $30.7 million of total unrecognized stock-based compensation expense related to unvested RSUs and stock options, which is expected to be recognized over the remaining weighted-average vesting period of 2.5 years.
The fair value of the Company’s stock options granted and purchase rights to the ESPP were estimated using the Black-Scholes valuation model with the following assumptions: | | | | | | | | | | | | | | | | | |
| Year Ended December 31, |
| 2025 | | 2024 | | 2023 |
| Stock Options: | | | | | |
| Risk-free interest rate | 3.7% - 4.4% | | 3.4% - 4.6% | | 3.5% - 4.7% |
| Expected dividend yield | None | | None | | None |
| Expected term (in years) | 5.4 - 5.7 | | 5.3 - 5.4 | | 5.0 - 5.2 |
| Expected volatility | 82.1% - 84.5% | | 81.4% - 83.1% | | 71.1% - 83.1% |
| | | | | |
| Weighted-average grant date fair value per share | $ | 5.85 | | | $ | 14.43 | | | $ | 10.63 | |
| | | | | |
| Employee Stock Purchase Plan: | | | | | |
| Risk-free interest rate | 3.8% - 4.0% | | 4.3% - 4.9% | | 5.2% - 5.5% |
| Expected dividend yield | None | | None | | None |
| Expected term (in years) | 0.5 | | 0.5 | | 0.5 |
| Expected volatility | 72.3% - 91.1% | | 54.9% - 66.0% | | 72.8% - 82.5% |
| | | | | |
| Weighted-average grant date fair value per share | $ | 1.39 | | | $ | 3.84 | | | $ | 3.19 | |