Note 9. Stock-Based Compensation

The Company maintains the following equity incentive plans:

2011 Equity Incentive Plan

In 2011, the Company established its 2011 Equity Incentive Plan (the “2011 Plan”) that provided for the granting of stock options to employees and nonemployees of the Company. Under the 2011 Plan, the Company had the ability to issue incentive stock options (“ISOs”), non-statutory stock options (“NSOs”), stock appreciation rights ("SARs"), RSAs, and RSUs. Options under the 2011 Plan could be granted for periods of up to 10 years. The ISOs could be granted at a price per share not less than the fair value at the date of grant.

2019 Equity Incentive Plan

The Company’s board of directors adopted and the Company’s stockholders approved the 2019 Equity Incentive Plan (the “2019 Plan”) in May 2019 and June 2019, respectively. The 2019 Plan became effective in June 2019 in connection with the Company’s IPO, and serves as the successor to the 2011 Plan. Pursuant to the 2019 Plan, 7,440,524 shares of common stock were initially reserved for grant, including any shares that were reserved and available for issuance under the 2011 Plan at the time the 2019 Plan became effective, and any shares that become available upon forfeiture or repurchase by the Company under the 2011 Plan, will be reserved for future issuance. No further grants were made under the 2011 Plan after the adoption of 2019 Plan.

The 2019 Plan provides for the grant of ISOs, NSOs, SARs, RSAs, RSUs, PSAs, performance cash awards, and other forms of equity compensation. ISOs may be granted only to the Company’s employees and to any of the Company’s parent or subsidiary corporation’s employees. All other awards may be granted to employees, including officers, and to non-employee directors and consultants of the Company and any of the Company’s affiliates. The exercise price of a stock option generally cannot be less than 100% of the fair market value of the Company’s common stock on the date of grant. Options under the 2019 Plan may be granted for periods of up to 10 years. In addition, the number of shares of the Company's common stock available for grant and issuance shall be increased on January 1 of each calendar year during the term of the Plan by the lesser of (i) five percent (5%) of the number of shares of the common stock issued and outstanding on each December 31 immediately prior to the date of increase, or (ii) such number of shares determined by the Board.

2020 Inducement Plan

The Compensation Committee of the Company’s board of directors adopted the 2020 Inducement Plan (the “Inducement Plan”) in May 2020, which became effective upon adoption. The Inducement Plan was adopted without stockholder approval, as permitted by the Nasdaq Stock Market rules. The Inducement Plan provides for the grant of equity-based awards, including NSOs, SARs, RSAs, RSUs, PSAs, and other forms of equity compensation, and its terms are substantially similar to the stockholder-approved 2019 Plan. In accordance with relevant Nasdaq Listing Rules, awards under the Inducement Plan may only be made to individuals not previously employees or non-employee directors of the Company (or following such individuals’ bona fide period of non-employment with the Company), as an inducement material to the individuals' entry into employment with the Company. These Awards must be approved by either a majority of the Company’s independent directors or the Company’s compensation committee, provided such committee comprises solely independent directors (the “Independent Compensation Committee”) in order to comply with the exemption from the stockholder approval requirement for inducement grants provided under the Nasdaq Marketplace Rules. Pursuant to the Inducement Plan, which was last amended in February 2026, the aggregate number of shares of Common Stock that may be issued will not exceed 2,050,000 shares.

2019 Employee Stock Purchase Plan

The Company’s board of directors adopted and the Company’s stockholders approved the 2019 Employee Stock Purchase Plan (the “ESPP”) in May 2019 and June 2019, respectively. Pursuant to the ESPP, 250,000 shares of common stock were initially reserved for future issuance. In addition, on each January 1 for the first ten calendar years after the first offering date, the aggregate number of common stock reserved for issuance under the ESPP shall be increased automatically by the number of shares equal to the lesser of (i) one percent (1%) of the total number of outstanding shares of common stock on the immediately preceding December 31, or (ii) 500,000 shares of common stock. Subject to any plan limitations, the ESPP allows eligible employees to contribute, normally through payroll deductions, up to 15% of their earnings for the purchase of the Company’s common stock at a discounted price per share. The price at which common stock is purchased under the ESPP is equal to 85% of the fair market value of the Company’s common stock on the first or last day of the offering period, whichever is lower. The ESPP provides for separate six-month offering periods beginning on May 1 and November 1 of each year.

Shares of common stock available for issuance under the Company’s equity incentive plans at December 31, 2025 were as follows:

 

 

 

December 31, 2025

 

Outstanding stock awards

 

 

13,318,317

 

Reserved for future award grants

 

 

4,703,664

 

Reserved for future ESPP

 

 

118,646

 

Total common stock reserved for stock awards

 

 

18,140,627

 

 

Service-Based Stock Option Activity

A summary of the Company’s stock option activity (excluding performance-based stock option activity, which is presented separately below) for the years ended December 31, 2025 and 2024 is as follows:

 

 

 

Outstanding Options

 

(in thousands, except share and per share data)

 

Number of
Shares

 

 

Weighted-
Average
Exercise Price

 

 

Weighted-
Average
Remaining
Contractual
Term (in years)

 

 

Aggregate
Intrinsic
Value

 

Balance—December 31, 2023

 

 

5,805,586

 

 

$

7.40

 

 

 

6.90

 

 

$

64

 

Options granted

 

 

3,612,000

 

 

 

2.19

 

 

 

 

 

 

 

Options exercised

 

 

(80,998

)

 

 

2.46

 

 

 

 

 

 

 

Options forfeited or expired

 

 

(728,870

)

 

 

9.65

 

 

 

 

 

 

 

Balance—December 31, 2024

 

 

8,607,718

 

 

$

5.07

 

 

 

7.64

 

 

$

21,949

 

Options granted

 

 

4,911,000

 

 

 

4.35

 

 

 

 

 

 

 

Options exercised

 

 

(444,463

)

 

 

4.28

 

 

 

 

 

 

 

Options forfeited or expired

 

 

(552,695

)

 

 

7.06

 

 

 

 

 

 

 

Balance—December 31, 2025

 

 

12,521,560

 

 

$

4.73

 

 

 

7.71

 

 

$

51,539

 

Options vested and exercisable as of December 31, 2025

 

 

6,882,977

 

 

$

5.41

 

 

 

6.70

 

 

$

28,497

 

Options granted to new hires generally vest over a four-year period, with 25% vesting at the end of one year and the remaining vesting monthly thereafter. Options granted as merit awards generally vest monthly over a three- or four-year period.

The aggregate intrinsic value of unexercised stock options is calculated as the difference between the closing price of the Company’s common stock of $7.96 on December 31, 2025 and the exercise prices of the underlying stock options. Out-of-the money stock options are excluded from aggregate intrinsic value.

The weighted-average grant date fair value of options granted was $3.20 and $1.53 per share for the years ended December 31, 2025 and 2024, respectively. During the year ended December 31, 2025 and 2024, the total intrinsic value of options exercised was $1.6 million and $0.2 million, respectively. The income tax benefit related to the stock options exercised was $0.3 million and immaterial for the years ended December 31, 2025 and 2024, respectively. As of December 31, 2025, the unrecognized stock-based compensation of unvested options was $14.2 million, which is expected to be recognized over a weighted-average period of 2.1 years.

Valuation of Service-Based Stock Options

The Company estimated the fair value of stock options using the Black-Scholes option-pricing model. Fair value of stock options is recognized as compensation expense on a straight-line basis over the requisite service periods of the awards. Fair value of stock options was estimated using the following range of assumptions:

 

 

 

Year Ended December 31,

 

 

2025

 

2024

Expected term (in years)

 

5.50 - 6.08

 

5.50 - 6.08

Volatility

 

83.72 - 90.90%

 

72.61 - 83.68%

Risk-free interest rate

 

3.70 - 4.50%

 

3.48 - 4.65%

Dividend yield

 

%

 

%

 

Performance-Based Stock Option Activity

During 2024, the Company granted performance-based stock options ("PSOs") to the executive leadership team. Vesting of the PSOs is based upon attainment of certain Medicare reimbursement coverages by the end of 2025 and subject to continuous service by the executives. Fair value was estimated using the Black-Scholes option-pricing model. Total grant-date fair value of the PSOs was $0.3

million. As of December 31, 2025, not all the Medicare reimbursement coverages were obtained and the Company canceled a portion of the PSOs. Accordingly, the Company reversed previously recognized stock-based compensation expense associated with the performance conditions that were not met. As of December 31, 2025, the recognized stock-based compensation cost related to vested PSOs was immaterial.

A summary of the Company’s performance-based stock option activity for the years ended December 31, 2025 and 2024 is as follows:

 

 

Outstanding Performance-Based Options

 

(in thousands, except share and per share data)

 

Number of
Shares

 

 

Weighted-
Average
Exercise Price

 

 

Weighted-
Average
Remaining
Contractual
Term (in
years)

 

 

Aggregate
Intrinsic
Value

 

Balance—December 31, 2023

 

 

 

 

$

 

 

 

-

 

 

$

 

Options granted

 

 

271,500

 

 

 

1.61

 

 

 

 

 

 

 

Balance—December 31, 2024

 

 

271,500

 

 

$

1.61

 

 

 

9.20

 

 

$

1,133

 

Options forfeited or expired

 

 

(181,000

)

 

 

1.61

 

 

 

 

 

 

 

Balance—December 31, 2025

 

 

90,500

 

 

 

1.61

 

 

 

8.20

 

 

$

575

 

Options vested and exercisable as of December 31, 2025

 

 

90,500

 

 

$

1.61

 

 

 

8.20

 

 

$

575

 

 

Restricted Stock Units ("RSU") Activity and Valuation

A summary of the Company’s RSU activity for the years ended December 31, 2025 and 2024 is as follows:

 

 

 

Unvested Restricted Stock Units

 

(in thousands, except share and per share data)

 

Number of
Shares

 

 

Weighted-
Average
Grant Date
Fair Value

 

 

Aggregate
Fair Value

 

Balance—December 31, 2023

 

 

1,253,826

 

 

$

8.99

 

 

$

2,633

 

RSUs vested

 

 

(601,285

)

 

 

10.46

 

 

 

1,719

 

RSUs forfeited

 

 

(219,057

)

 

 

10.20

 

 

 

 

Balance—December 31, 2024

 

 

433,484

 

 

$

6.34

 

 

$

2,506

 

RSUs vested

 

 

(282,580

)

 

 

7.72

 

 

 

1,804

 

RSUs forfeited

 

 

(19,647

)

 

 

4.52

 

 

 

 

Balance—December 31, 2025

 

 

131,257

 

 

$

3.63

 

 

$

1,045

 

 

The Company grants RSUs to employees to receive shares of the Company’s common stock. The RSUs awarded are subject to the individual’s continued service to the Company through each applicable vesting date. RSUs granted to new hires generally vest annually over a four-year period. RSUs granted as merit awards generally vest semi-annually over a three- or four-year period. The Company accounts for the fair value of RSUs using the closing market price of the Company’s common stock on the date of grant.

The aggregate fair value of unvested RSUs is calculated using the closing price of the Company’s common stock of $7.96 on December 31, 2025. During the year ended December 31, 2025 and 2024, the total fair value of shares vested was $1.8 million and $1.7 million, respectively. The income tax benefit related to vested RSUs was $0.4 million for each of the years ended December 31, 2025 and 2024. As of December 31, 2025, the unrecognized stock-based compensation cost of unvested RSUs was $0.3 million, which is expected to be recognized over a weighted-average period of 0.8 years.

The Company’s default tax withholding method for RSUs is the sell-to-cover method, in which shares with a market value equivalent to the tax withholding obligation are sold on behalf of the holder of the RSUs upon vesting and settlement to cover the tax withholding liability and the cash proceeds from such sales are remitted by the Company to taxing authorities.

Performance-Based RSU Activity

In March 2025, the Company granted performance-based RSUs ("PSUs") to the executive leadership team. A percentage of the number of RSUs will vest based upon achieving the Company's operational target as of the end of 2026, and subject to continuous service by the executives throughout March 2028. Fifty percent of the aggregate number of achieved PSUs (if any) will vest upon certification in March 2027, with the remaining fifty percent vesting in March 2028. The total grant-date fair value of the PSUs was $2.1 million. As of December 31, 2025, the Company no longer considered the achievement of the operational target to be probable. Accordingly, the Company reversed previously recognized stock-based compensation expense and no stock-based compensation cost was recognized for the year ended December 31, 2025.

 

 

 

Unvested Performance-Based Restricted Stock Units

 

(in thousands, except share and per share data)

 

Number of
Shares

 

 

Weighted-
Average
Grant Date
Fair Value

 

 

Aggregate
Fair Value

 

Balance—December 31, 2024

 

 

 

 

$

 

 

$

 

PSUs granted

 

 

575,000

 

 

 

3.63

 

 

 

 

Balance—December 31, 2025

 

 

575,000

 

 

$

3.63

 

 

$

4,577

 

ESPP Activity and Valuation

During the years ended December 31, 2025 and 2024, 381,415 and 583,695 shares of common stock were purchased under the ESPP, respectively. The fair value of stock purchase rights granted under the ESPP was estimated using the following range of assumptions:

 

 

 

Year Ended December 31,

 

 

2025

 

2024

Expected term (in years)

 

0.5

 

0.5

Volatility

 

78.55 - 92.85%

 

61.35 - 95.66%

Risk-free interest rate

 

3.79 - 4.22%

 

4.42 - 5.43%

Dividend yield

 

–%

 

–%

Fair value

 

$1.59 - $3.60

 

$0.51 - $2.14

Stock-based Compensation Expense

The following is a summary of stock-based compensation expense by function (in thousands):

 

 

 

Year Ended December 31,

 

 

 

2025

 

 

2024

 

Cost of revenue

 

$

718

 

 

$

658

 

Research and development

 

 

3,204

 

 

 

4,039

 

Selling, general and administrative

 

 

5,507

 

 

 

5,989

 

Total stock-based compensation expense

 

$

9,429

 

 

$

10,686

 

 

The following is a summary of stock-based compensation expense by award type (in thousands):

 

 

 

Year Ended December 31,

 

 

 

2025

 

 

2024

 

Service-based stock options

 

$

7,151

 

 

$

5,017

 

Performance-based stock options

 

 

(28

)

 

 

112

 

Service-based RSUs

 

 

1,601

 

 

 

5,251

 

Performance-based RSUs

 

 

 

 

 

 

ESPP

 

 

705

 

 

 

306

 

Total stock-based compensation expense

 

$

9,429

 

 

$

10,686

 

At-the-Market Equity Offerings

In December 2021, the Company entered into an At-the-Market ("ATM") Sales Agreement with BTIG, LLC (“BTIG”), as amended in December 2023 (the “Sales Agreement”), under which it was permitted to offer and sell its common stock from time to time through BTIG as its sales agent. BTIG agreed to use commercially reasonable efforts to sell the Company’s common stock from time to time, based upon instructions from the Company (including any price, time or size limits or other customary parameters or conditions the Company may impose). The Company agreed to pay BTIG a commission of up to 3% of the gross sales proceeds of any common stock sold through BTIG under the Sales Agreement. The Company was not obligated to make any sales of common stock under the Sales Agreement.

In December 2024, the Company entered into an Amended and Restated At-the-Market Sales Agreement (the “Amended Sales Agreement”) with Piper Sandler & Co. (“Piper”) and BTIG. The Amended Sales Agreement amends and restates the Sales Agreement with BTIG, previously entered into in December 2021, as amended in December 2023, to add Piper as a sales agent (Piper and BTIG, together, the “Sales Agents”), among certain other changes. The Sales Agents have agreed to use commercially reasonable efforts to sell the Company’s common stock from time to time, based upon instructions from the Company (including any price, time or size limits or other customary parameters or conditions the Company may impose). The Company will pay the applicable Sales Agent a commission

of up to 3% of the gross sales proceeds of any common stock sold through such Sales Agent under the Amended Sales Agreement. The Company is not obligated to make any sales of common stock under the Amended Sales Agreement.

The Company issued and sold 16,196,287 and 6,660,731 shares of its common stock at a weighted-average price of $7.95 and $4.61 per share under the Sales Agreement and received $126.8 million and $30.1 million in proceeds, net of commissions, during 2025 and 2024, respectively.

About Stock Compensation Disclosures

Stock-based compensation disclosures detail the equity awards granted to employees and executives — including stock options, restricted stock units (RSUs), and performance shares — along with the valuation methods and assumptions used to expense them. This section reveals the true cost of talent retention and the alignment between management incentives and shareholder interests.

Key signals: total unrecognized compensation expense and its expected recognition period signal future earnings headwinds from already-granted awards. For stock options, examine Black-Scholes assumptions — expected volatility, risk-free rate, and expected term — as understating any of these reduces reported compensation expense. Compare stock compensation expense as a percentage of revenue against peers to assess dilution cost. Watch vesting schedules for acceleration clauses tied to change-of-control events. Performance-based awards with undemanding targets may indicate weak governance. Add back stock compensation to operating cash flow to calculate a more conservative free cash flow figure.