Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2019

Summary of Stock Based Compensation Expense

Stock compensation expense was allocated between departments in continuing operations as follows (in thousands).

	Year ended
	December 31, 2019		December 31, 2018
Research and development	$	158	$	205
General and administrative		667		982
Total	$	825	$	1,187

Schedule of Fair Value of Award Granted Using Black-Scholes Option Pricing Model

The fair value of each award granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions.

	Year Ended
	December 31, 2019	December 31, 2018
Expected life (years)	5.5-6.1	5.5-6.0
Risk-free interest rate	1.6%-2.6%	2.7%-2.8%
Volatility	70%-75%	70%-71%
Dividend rate	— %	— %

Summary of Stock Option and Restricted Stock Unit Transactions

The following table summarizes stock option and restricted stock unit transactions for the years ended December 31, 2019 and 2018 as issued under the 2014 Plan.

	Shares Available			Number of Options			Weighted- Average Exercise Price per		Weighted Average Remaining Contractual Term
	for Grant			Outstanding			Share		(in years)
Balance at January 1, 2018		1,571,212			1,026,987		$	9.99		7.94
Additional shares authorized		223,742
Shares allocated to grants of restricted stock units		(245,588	)
Options granted		(756,086	)		756,086		$	1.68
Options exercised		—			—			—		—
Options canceled/forfeited		115,920			(115,920	)	$	12.72		—
Balance at December 31, 2018		909,200			1,667,153		$	6.03		8.27
Additional shares authorized		223,742
Shares allocated to grants of restricted stock units		(61,218	)
Options granted		(658,285	)		658,285		$	1.77
Options exercised		—			—			—		—
Options canceled/forfeited		202,321			(202,321	)	$	6.99		—
Balance at December 31, 2019		615,760			2,123,117		$	4.62		7.87
Options vested at December 31, 2019					1,153,457		$	6.91		7.24
Options vested and expected to vest at December 31, 2019					2,123,117		$	4.62		7.87