In April 2012, the Company adopted the 2012 Stock Option Plan (“2012 Plan”). The 2012 Plan provides for the granting of stock-based awards to employees, directors, and consultants under terms and provisions established by the Company’s board of directors. Under the terms of the 2012 Plan, options may be granted at an exercise price not less than fair market value. For employees holding more than 10% of the voting rights of all classes of stock, the exercise prices for incentive and nonstatutory stock options must be at least 110% of fair market of the common stock on the grant date, as determined by the Company’s board of directors. The terms of options granted under the 2012 Plan may not exceed ten years.

The 2012 Plan was superseded by the 2017 Stock Option Plan (“2017 Plan”). Any outstanding awards under the 2012 Plan will continue to be governed by the terms of the 2012 Plan.

In August 2017, the Company adopted the 2017 Plan. The Company’s stockholders approved the 2017 Plan in September 2017 and it became effective immediately prior to the closing of the Company’s IPO. In connection with the adoption of the 2017 Plan, no additional awards and no shares of common stock remain available for future issuance under the 2012 Plan and shares reserved but not issued under the 2012 Plan as of the effective date of the 2017 Plan were included in the number of shares reserved for issuance under the 2017 Plan. In addition, shares subject to awards under the 2012 Plan that are forfeited or terminated will be added to the 2017 Plan. The number of shares available for issuance under the 2017 Plan will be automatically increased on the first day of each fiscal year beginning on January 1, 2018 and ending on (and including) January 1, 2027, in an amount equal to the lesser of (1) 4% of the outstanding shares of our common stock on the last day of the immediately preceding fiscal year, or (2) another amount determined by the Company’s board of directors. The automatic increase in the number of shares available for issuance under the 2017 plan for the fiscal year 2019 was 691,431 shares. The 2017 Plan provides for the granting of incentive stock options, or ISOs, within the meaning of Section 422 of the Internal Revenue Code to employees and the granting of nonstatutory stock options, or NSOs, to employees, non-employee directors, advisors and consultants. The 2017 Plan also provides for the grants of restricted stock, stock appreciation rights, or SARs, stock unit and cash-based awards to employees, non-employee directors, advisors and consultants.

The Company’s stock award activity under the stock incentive plan is summarized as follows:

Certain employees and directors have exercised option grants prior to vesting. The unvested shares are subject to a repurchase right held by the Company at the original purchase price. The proceeds initially are recorded as liability related to early exercised stock options and reclassified to common stock and additional paid in capital as the repurchase right lapses.

For the three months ended March 31, 2019 and 2018, there were no options early exercised. In addition, the Company did not repurchase any shares of unvested common stock related to early exercised stock options during the three months ended March 31, 2019 and 2018.

As of March 31, 2019 and December 31, 2018, 129,757 and 155,257 shares, respectively, held by employees and nonemployees were subject to repurchase at an aggregate price of $0.1 million and $0.1 million, respectively.

The Company’s stock option activity under the stock incentive plan is summarized as follows:

	Options Issued and Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
As of December 31, 2018		1,139,935		$	2.01		7.6	$	3,428
Granted		—		$	—
Exercised (1)		(46,666	)	$	1.38
Canceled		—		$	—
As of March 31, 2019		1,093,269		$	2.03		7.4	$	5,211
Options vested and expected to vest as of March 31, 2019		1,093,269		$	2.03		7.4	$	5,211
Options vested and exercisable as of March 31, 2019		453,169		$	1.80		7.1	$	2,265

(1)

Includes vesting of early-exercised options.

The stock options outstanding and exercisable by exercise price at March 31, 2019 are as follows:

		Options Outstanding						Options Vested and Exercisable
Exercise Price		Number Outstanding		Weighted- Average Remaining Contractual Life (Years)		Weighted- Average Exercise Price		Number Exercisable		Weighted- Average Exercise Price
$	0.16		64,950		4.8	$	0.16		64,950	$	0.16
$	0.37		180,088		6.2	$	0.37		71,413	$	0.37
$	0.97		150,084		7.0	$	0.97		65,684	$	0.97
$	2.51		179,945		7.4	$	2.51		70,085	$	2.51
$	2.89		49,000		7.9	$	2.89		16,750	$	2.89
$	2.93		334,002		8.1	$	2.93		122,172	$	2.93
$	3.18		135,200		8.3	$	3.18		42,115	$	3.18
			1,093,269		7.4	$	2.03		453,169	$	1.80

The aggregate intrinsic value of options exercised for the three months ended March 31, 2019 and 2018 was $0.1 million and $1.3 million, respectively. The Company has various vesting agreements with employees. Options granted generally vest over a five-year period and generally are exercisable up to 10 years.

	Units Issued and Outstanding			Weighted-Average Grant Date Fair Value
As of December 31, 2018		255,500		$	11.53
Granted		30,000		$	7.97
Released		(14,200	)	$	14.26
Canceled		(5,000	)	$	9.97
As of March 31, 2019		266,300		$	11.01

Restricted stock units are converted into shares of the Company’s common stock upon vesting on a one-for-one basis. Restricted stock unit awards generally vest over a five-year period and are subject to the grantee’s continued service with the Company.