Stock Option Plans

3 Months Ended

Mar. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock Option Plans

Stock Option Plans

2008 Long Term Incentive Plan

During 2008, the Company adopted the 2008 Long Term Incentive Plan, which allows for incentive stock options for its employees and nonqualified stock options (inclusive of restricted stock units and stock appreciation rights) (the “2008 Plan”) for employees and nonemployees under which an aggregate of 330,582 stock options and stock purchase rights may be granted. In December 2013, the total amount available for grant under the 2008 Plan was increased by 224,200 to 554,782. In March 2014, the Company’s board of directors approved an increase of 115,153 shares available for grant pursuant to the 2008 Plan to 669,935. In March 2015, the total amount of available to grant under the 2008 Plan was increased in conjunction with the Company’s offering of Series D preferred stock by 391,650 shares to 1,061,585. Options under the 2008 Plan have a maximum life of 10 years from the date of grant. Options vest at various intervals, as determined by the Company’s board of directors at the date of grant.

2015 Equity Incentive Plan

In August 2015, the Company’s board of directors approved the 2015 Equity Incentive Award Plan (the “2015 Plan”), which was effective in connection with the pricing of the IPO on September 30, 2015. The 2015 Plan provides for the granting of a variety of stock‑based compensation awards, including stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, deferred stock awards, dividend equivalent awards, stock payment awards, performance awards and other stock‑based awards. The 2015 Plan is the successor to the 2008 Plan and the 462,934 options outstanding in the 2008 Plan at March 31, 2017 may be transferred to the 2015 Plan if awards thereunder terminate, expire or lapse for any reason without the delivery of shares to the holder thereof. As of March 31, 2017, 316,932 shares have been transferred from the 2008 Long Term Incentive Plan to the 2015 Equity Incentive Plan for awards that have terminated, expired, or lapsed. Under the 2015 Plan, 1,671,800 shares of the Company’s common stock were initially authorized and reserved for issuance. In addition, 1,041,526 shares of the Company's common stock were authorized and reserved for issuance in the first quarter of 2017, for a total of 3,030,258 authorized for grant under the 2015 Plan at March 31, 2017.

2015 Employee Stock Purchase Plan

In August 2015, the Company’s board of directors approved the 2015 Employee Stock Purchase Plan (the “ESPP”), which was effective in connection with the pricing of the IPO on September 30, 2015. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP generally provides for set offering periods, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. Shares available for future purchase under the ESPP were 369,960 at March 31, 2017; however, as of December 2016, the Company has suspended future issuances of the Company's common stock under the ESPP plan.

Stock Option Activity

The Company’s stock option activity for the three months ended March 31, 2017 was as follows:

			Weighted‑
			Average		Weighted‑Average
	Number		Exercise		Contractual
	of Shares		Price		Life (years)
Outstanding at December 31, 2016	1,905,214		$	5.39	7.49
Granted	—		—
Exercised	(15,300	)	1.65
Forfeited/canceled	(278,593	)	5.52
Outstanding at March 31, 2017	1,611,321		$	5.40	8.12
Options exercisable at March 31, 2017	692,798		$	5.45	7.30

Stock Compensation Expense

Total stock-based compensation expense for the three and three months ended March 31, 2017 was recognized as follows in the statements of comprehensive loss (in thousands):

	Three Months Ended March 31,
	2017		2016
Research and development expense	$	41	$	171
General and administrative expense	323		276
Total stock based compensation	$	364	$	447

As of March 31, 2017, there was approximately $2.9 million of unrecognized compensation cost related to the stock options granted under the 2015 Plan, which is expected to be amortized over a weighted-average period of 2.4 years. There were no restricted stock units or stock appreciation rights granted under the 2015 Plan as of March 31, 2017.