Stockholder's Equity (Tables)

9 Months Ended

Sep. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

Activity under the Company’s stock option plan is set forth below:

						Weighted
						Average
				Weighted		Remaining		Aggregate
				Average		Contractual		Intrinsic
	Number of			Exercise		Life		Value
	Shares			Price		(in years)		(in thousands)
Balances, January 1, 2019		1,515,923		$	18.65
Options granted		483,328			5.55
Options cancelled		(97,382	)		96.15
Options exercised		(2,000	)		0.66
Balances, September 30, 2019		1,899,869		$	11.35		7.0	$	9,294
Outstanding and expected to vest as of September 30, 2019		1,870,009		$	11.41		6.9	$	9,244
Exercisable as of September 30, 2019		1,490,943		$	12.01		6.3	$	8,612

Summary of Fair Value of Employee Stock Options

The fair value of employee stock options was estimated using the Black-Scholes model with the following weighted-average assumptions:

	September 30,
	2019
Expected volatility		111.0	%
Risk-free interest rate		2.4	%
Dividend yield		0.0	%
Expected life (in years)		6.0