Shares of common stock reserved for issuance under the Company’s equity incentive plans were as follows:


	March 31, 2025
Outstanding stock awards		13,220,288
Reserved for future award grants		5,094,744
Reserved for future ESPP		500,061
Total common stock reserved for stock awards		18,815,093

A summary of the Company’s service-based stock option activity (excluding performance-based stock option activity, which is presented separately below) for the three months ended March 31, 2025 is as follows:


	Outstanding Service-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, 2024		8,607,718		$	5.07		7.64	$	21,949
Options granted		3,467,500			3.66
Options exercised		(62,022	)		2.13
Options forfeited or expired		(48,780	)		9.49
Balance—March 31, 2025		11,964,416		$	4.66		8.17	$	7,914
Options vested and exercisable as of March 31, 2025		4,945,104		$	6.88		6.49	$	3,119

The weighted-average grant date fair value of options granted was $2.65 and $1.61 per share for the three months ended March 31, 2025 and 2024, respectively. As of March 31, 2025, the unrecognized stock-based compensation cost of unvested options was $14.3 million, which is expected to be recognized over a weighted-average period of 2.3 years.

The Company estimated the fair value of service-based 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:


	Three Months Ended March 31,
	2025	2024
Expected term (in years)	5.77 - 6.08	5.50 - 6.08
Volatility	83.72 - 84.08%	72.63 - 80.28%
Risk-free interest rate	4.15 - 4.50%	3.88 - 4.33%
Dividend yield	–%	–%

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 March 31, 2025, the unrecognized stock-based compensation cost of unvested PSOs was $0.1 million, which is expected to be recognized by the end of 2025.

A summary of the Company's performance-based stock option activity for the three months ended March 31, 2025 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, 2024		271,500	$	1.61		9.20	$	1,133
Balance—March 31, 2025		271,500	$	1.61		8.96	$	517
Options vested and exercisable as of March 31, 2025		—	$	—		—	$	—

A summary of the Company’s RSU activity for the three months ended March 31, 2025 is as follows:


	Unvested Service-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		433,484		$	6.34	$	2,506
RSUs vested		(21,970	)		17.23		118
RSUs forfeited		(2,142	)		6.61
Balance—March 31, 2025		409,372		$	5.75	$	1,437

As of March 31, 2025, the unrecognized stock-based compensation cost of unvested RSUs was $1.2 million, which is expected to be recognized over a weighted-average period of 1.1 years.

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 RSUs (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.

A summary of the Company's PSUs activity for the three months ended March 31, 2025 is as follows:


	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		—	$	—	$	—
RSUs granted		575,000		3.63
RSUs vested		—		—		—
RSUs forfeited		—		—
Balance—March 31, 2025		575,000	$	3.63	$	2,018

As of March 31, 2025, the unrecognized stock-based compensation cost of unvested PSUs was $2.0 million, which is expected to be recognized over a weighted-average of 2.4 years.

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


	Three Months Ended March 31,
	2025		2024
Service-based stock options	$	1,221	$	1,215
Performance-based stock options		35		6
Service-based RSUs		745		1,408
Performance-based RSUs		39		—
ESPP		179		58
Total stock-based compensation expense	$	2,219	$	2,687

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


	Three Months Ended March 31,
	2025		2024
Cost of revenue	$	197	$	154
Research and development		856		947
Selling, general and administrative		1,166		1,586
Total stock-based compensation expense	$	2,219	$	2,687