Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2019

Stockholders' Equity

Schedule of allocation of stock-based compensation expense

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Research and development	$	159	$	338	$	310	$	689
General and administrative		320		649		659		1,417
Total	$	479	$	987	$	969	$	2,106