In April 2006, the Company’s Board of Directors (the “Board”) adopted and the stockholders approved the 2006 Stock Option Plan (“2006 Plan”), which provided for the grant of incentive and non-statutory stock options. In February 2013, the Board adopted and the stockholders approved the 2013 Equity Incentive Plan (“2013 Plan”), which became effective on March 21, 2013. At that time, the Company ceased to grant equity awards under the 2006 Plan. Under the 2013 Plan, 643 shares of common stock were originally reserved for issuance. Additionally, all reserved and unissued shares under the 2006 Plan are eligible for issuance under the 2013 Plan. The 2013 Plan authorizes the award of incentive and non-statutory stock options, restricted stock awards, stock appreciation rights, RSUs, performance awards and stock bonuses to the Company’s employees, directors, consultants, independent contractors and advisors. On January 1 of each calendar year through 2023, the number of shares of common stock reserved under the 2013 Plan will automatically increase by an amount equal to 5% of the total outstanding shares as of immediately preceding December 31, or such lesser number of shares as determined by the Board. As of December 31, 2022, 734 shares of common stock were available for future grants under the 2013 Plan. Pursuant to the terms of the 2013 Plan, the shares available for issuance increased by 861 shares of common stock on January 1, 2023. The 2013 Plan expired in accordance with its terms in February 2023.

Under the 2006 Plan and the 2013 Plan, the term of options granted may not exceed ten years. Unless the terms of an optionee's stock option agreement provide otherwise, if an optionee's service relationship with the Company, or any of its affiliates, ceases for any reason other than disability or death, the optionee may exercise the vested portion of any options for three months after the date of such termination. If an optionee's service relationship with the Company, or any of its affiliates, ceases due to disability or death (or an optionee dies within a certain period following cessation of service), the optionee or a beneficiary may exercise any vested options for a period of 12 months. In no event, however, may an option be exercised beyond the expiration of its term.

A summary of stock option activity under the 2006 Plan and the 2013 Plan is as follows:


	Options Outstanding
	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Balance at December 31, 2020		389		$	23.57		5.77	$	—
Options forfeited and cancelled		(6	)		43.45		—
Balance at December 31, 2021		383		$	23.23		4.85	$	—
Options forfeited and cancelled		(46	)		49.87		—
Balance at December 31, 2022		337		$	19.59		4.45	$	—
Options exercisable as of December 31, 2022		322			20.31		4.36		—
Options vested as of December 31, 2022		322			20.31		4.36		—
Options vested and expected to vest as of December 31, 2022		337			19.59		4.45		—

The total estimated fair value of options vested was $31 during each of 2022 and 2021.

A summary of RSU activity under the 2013 Plan is as follows:


	RSUs Outstanding
	Number of Shares			Weighted Average Grant Date Fair Value Per Unit
Granted and unvested at December 31, 2020		1,006		$	2.80
RSUs granted		975			5.84
RSUs vested		(264	)		3.08
RSUs cancelled and withheld to cover taxes		(175	)		4.16
Granted and unvested at December 31, 2021		1,542		$	4.60
RSUs granted		1,142			1.90
RSUs vested		(593	)		3.72
RSUs cancelled and withheld to cover taxes		(277	)		5.91
Granted and unvested at December 31, 2022		1,814		$	2.99

In February 2013, the Board and stockholders approved the 2013 Employee Stock Purchase Plan (“2013 ESPP”), under which 143 shares of common stock were originally reserved for issuance. The 2013 ESPP became effective on March 22, 2013. The 2013 ESPP generally provides for six-month purchase periods and the purchase price for shares of common stock purchased under the 2013 ESPP is 85% of the lesser of the fair market value of the common stock on (1) the first trading day of the applicable offering period and (2) the last trading day of each purchase period in the applicable offering period. On January 1 of each calendar year following the first offering date, the number of shares reserved under the 2013 ESPP automatically increases by an amount equal to 1% of the total outstanding shares as of the immediately preceding December 31, but not to exceed 100 shares. Pursuant to the terms of the 2013 ESPP, the shares available for issuance increased by 100 shares on January 1, 2023. As of December 31, 2022, 346 shares were reserved for issuance under the 2013 ESPP. In 2022 and 2021, 27 and 23 shares, respectively, were issued under the 2013 ESPP. The 2013 ESPP expired in accordance with its terms in February 2023.