Stock based compensation - (Tables)

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of fair value of stock option awards on the grant date using the black-scholes option valuation model

The Company estimates the fair value of stock option awards on the grant date using the Black-Scholes option valuation model with the following weighted-average assumptions:

	Three and Six Months Ended June 30,
	2020		2019
Risk-free interest rate		N/A		1.30	%
Expected term (in years)		N/A		5.75
Expected volatility		N/A		70.0	%
Dividend yield		N/A		—

Summary of activity under the company's stock option plan

The following table summarizes the activity under the Company’s stock option plan during the six months ended June 30, 2020:

	Number of Options		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2019		1,073,044	$	2.45		8.7	$	906
Granted		—	$	—
Forfeited		—	$	—
Exercised		—	$	—
Outstanding at June 30, 2020		1,073,044	$	2.45		8.2	$	906
Vested and expected to vest at June 30, 2020		1,073,044	$	2.45		8.2	$	906
Exercisable at June 30, 2020		426,980	$	2.23		7.6	$	468

Summary of total stock-based compensation expense

Total stock-based compensation expense was classified in the accompanying condensed statements of operations and comprehensive loss as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
	( in thousands)				(in thousands)
Research and development	$	39	$	25	$	78	$	49
General and administrative		61		53		123		108
Total stock-based compensation expense	$	100	$	78	$	201	$	157