Stock and employee benefit plans (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of stock-based compensation expense for stock options granted to employees and non-employees

Total stock-based compensation expense recognized for stock options and RSUs is as follows (in thousands):

	Three Months Ended March 31,
	2020		2019
Research and development	160		182
General and administrative	$	224	$	247
Total	$	384	$	429

Schedule of stock option activity for employees and nonemployees

The following table summarizes stock option activity (shares in thousands):

	Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding at December 31, 2019	1,323		$	11.65		$	—
Granted	66		$	1.99
Exercised	—		$	—
Cancelled	(19	)	$	4.85
Outstanding at March 31, 2020	1,370		$	11.28	7.90	$	—
Exercisable at March 31, 2020	585		$	18.90	6.72	$	—