Stock-Based Compensation and Warrants (Tables)

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Activity Under Stock Incentive Plans

A summary of activity under the stock incentive plans is as follows (in thousands, except share data and price per share):

	Shares Subject to Outstanding Options			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
Outstanding — Balance at December 31, 2019		661,701		$	21.60	$	305
Options granted		491,494			4.32
Options exercised		—			—
Options forfeited		(131,849	)		6.39
Options expired		(40,463	)		48.57
Outstanding — Balance at September 30, 2020		980,883		$	13.87	$	1
Vested and expected to vest — September 30, 2020		965,445		$	14.03	$	1
Exercisable —September 30, 2020		540,267		$	21.51	$	—

Weighted-Average Fair Value Assumption of Stock Option Awards

The fair value of stock option awards to employees, executives, directors, and other service providers was estimated at the date of grant using the Black-Scholes Model with the following weighted-average assumption. There were 491,494 and 186,571 options granted during the nine months ended September 30, 2020 and 2019, respectively.

	Three Months Ended September 30,				Nine Months Ended September 30,
		2020		2019		2020		2019
Expected term (years)		6.01		6.24		6.50		7.13
Expected volatility	230%		99%		133%		99%
Risk-free interest rate	0.38%		1.84%		1.03%		2.05%
Dividend yield		—		—		—		—