Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 21,371	$ 7,042
Marketable securities	111,425	100,986
Prepaid expenses	3,270	1,491
Other current assets	22	15
Total current assets	136,088	109,534
Restricted cash	245	84
Property and equipment, net	325	321
Total assets	136,658	109,939
Current liabilities:
Accounts payable	8,242	2,989
Accrued liabilities	1,464	2,727
Total current liabilities	9,706	5,716
Other liabilities	11	19
Total liabilities	9,717	5,735
Commitments and contingencies (Note 10)
Stockholders’ equity:
Common stock, $0.0001 par value, 150,000,000 shares authorized as of June 30, 2019 and December 31, 2018; 35,817,393 and 28,055,344 shares issued and outstanding as of June 30, 2019 and December 31, 2018, respectively; 35,817,393 and 28,054,344 shares vested as of June 30, 2019 and December 31, 2018, respectively	4	3
Additional paid-in capital	227,561	175,635
Accumulated deficit	(100,794)	(71,393)
Accumulated other comprehensive gain (loss)	170	(41)
Total stockholders’ equity	126,941	104,204
Total liabilities and stockholders’ equity	$ 136,658	$ 109,939