In September 2019, the Board adopted, and the Company's stockholders approved, the 2019 Plan. Under the 2019 Plan, which expires in September 2029, the Company may grant stock options, stock appreciation rights, restricted stock, RSUs and other awards to individuals who are then employees, officers, non-employee directors or consultants of the Company or its subsidiaries. The options generally expire ten years after the date of grant and are exercisable to the extent vested. Vesting is established by the Board and is generally four years from the date of grant or, for grants to new hires, date of hire. The 2019 Plan contains an "evergreen provision" that allows annual increases in the number of shares available for issuance on the first day of each calendar year through January 1, 2029 in an amount equal to the lesser of: (i) 4% of the outstanding capital stock on each December 31st, or (ii) such lesser amount determined by the Board. As of September 30, 2024, 2,122,271 shares of common stock remained available for future awards under the 2019 Plan.


	Number of Shares	Weighted- Average Grant Date Fair Value
Outstanding, December 31, 2023	1,387,459	$	4.24
Awards granted	1,287,225	$	2.09
Awards released	(293,209)	$	5.87
Awards canceled	(571,007)	$	4.16
Outstanding, September 30, 2024	1,810,468	$	2.47

As of September 30, 2024, all of the outstanding RSUs were unvested. The fair value of RSUs vested in the nine months ended September 30, 2024 and 2023 was $0.5 million and $0.4 million, respectively. The weighted average grant date fair value for RSUs granted in the nine months ended September 30, 2024 and 2023 was $2.09 and $2.42, respectively. As of September 30, 2024, total unrecognized compensation cost related to RSUs was $3.7 million, which is expected to be recognized over a remaining weighted-average vesting period of 3.0 years.


	Number of Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2023	986,819	$	11.87	6.44	$	228
Granted	55,500	$	1.99
Exercised	(85,124)	$	0.26
Forfeited	(9,518)	$	16.70
Expired	(371,526)	$	15.48
Outstanding, September 30, 2024	576,151	$	10.23	6.57	$	197
Vested and expected to vest, September 30, 2024	576,151	$	10.23	6.57	$	197
Options exercisable, September 30, 2024	552,686	$	10.56	6.45	$	177

There were 55,500 and 73,500 stock options granted in the nine months ended September 30, 2024 and 2023, respectively. The intrinsic value is calculated as the difference between the fair value of the Company's common stock and the exercise price of the stock options. The aggregate intrinsic value of options exercised during the nine months ended September 30, 2024 was $0.3 million. The aggregate intrinsic value of options exercised during the nine months ended September 30, 2023 was $0.2 million. As of September 30, 2024, total unrecognized compensation cost related to option awards was less than $0.1 million, which is expected to be recognized over a remaining weighted-average vesting period of 2.29 years.

In September 2019, the Board adopted, and the Company's stockholders approved, the ESPP. The ESPP became effective on the day the ESPP was adopted by the Board. The ESPP permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. The number of shares of common stock available for issuance under the ESPP will be annually increased on the first day of each calendar year during the term of the ESPP through January 1, 2029 in an amount equal to the lesser of (i) 1% of the outstanding capital stock on each December 31st, or (ii) such lesser amount determined by the Board. As of September 30, 2024, 523,744 shares of common stock remained available for issuance under the ESPP.

Total non-cash stock-based compensation expense recorded related to options granted, RSUs granted and stock purchase rights granted under the ESPP in the condensed statements of operations is as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Costs of revenue	$	47	$	45	$	103	$	161
Selling, general and administrative	114		792		1,058		2,497
Research and development	56		53		169		196
Total	$	217	$	890	$	1,330	$	2,854