Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS
Cash and cash equivalents	$ 24,545	$ 22,461
Marketable securities	64,155	52,052
Prepaid expenses and other current assets	3,930	2,158
Total current assets	92,630	76,671
Restricted cash	1,500
Property and equipment, net	980	1,018
Operating lease right-of-use assets	4,872
Other non-current assets	114	50
TOTAL ASSETS	100,096	77,739
CURRENT LIABILITIES
Accounts payable	2,431	663
Operating lease liabilities	289
Accrued and other current liabilities	12,676	9,576
Total current liabilities	15,396	10,239
Non-current operating lease liabilities	4,867
Other non-current liabilities	38	72
TOTAL LIABILITIES	20,301	10,311
Commitments and Contingencies (Note 6 and 10)
STOCKHOLDERS’ EQUITY
Preferred stock, $0.0001 par value; 10,000,000 shares authorized as of September 30, 2019 and December 31, 2018; no shares issued and outstanding as of September 30, 2019 and December 31, 2018
Common stock, $0.0001 par value; 500,000,000 shares authorized as of September 30, 2019 and December 31, 2018; 28,923,241 shares and 24,140,097 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively	3	2
Additional paid-in capital	253,334	184,314
Accumulated other comprehensive income (loss)	78	(27)
Accumulated deficit	(173,620)	(116,861)
TOTAL STOCKHOLDERS’ EQUITY	79,795	67,428
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 100,096	$ 77,739