Stock-based Compensation

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

7. Stock-based Compensation

In January 2019, the number of shares of common stock available for issuance under the 2018 Equity Incentive Plan was increased by approximately 1.5 million shares as a result of the automatic increase provision in the 2018 Plan.

Stock Options

Stock option activity under the 2018 Plan and 2015 Equity Incentive Plan is summarized as follows (in thousands, except share and per share data).

				Outstanding Awards
	Number of Shares Available for Grant			Number of Shares Underlying Outstanding Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Balance, December 31, 2018		3,024,404			5,135,267		$	5.99		9.07	$	10,681
Shares authorized		1,473,194			—
Options exercised		—			(80,000	)	$	1.04				290
Balance, March 31, 2019		4,497,598			5,055,267		$	6.14		8.69		8,769
Options granted		(449,988	)		449,988		$	8.40
Options forfeited or canceled		15,804			(15,804	)	$	7.00
Options exercised		—			(21,284	)	$	2.77				190
Balance, June 30, 2019		4,063,414			5,468,167		$	6.34		8.60	$	29,716

Stock-based compensation is classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	703	$	312	$	1,409	$	365
General and administrative		541		345		992		384
Total stock-based compensation	$	1,244	$	657	$	2,401	$	749

As of June 30, 2019, the unrecognized stock-based compensation of unvested employee options and unvested RSAs and RSUs was $14.9 million and it is expected to be recognized over a weighted-average period of 2.48 years.