Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and cash equivalents	$ 65,713	$ 19,253
Marketable securities	92,017	52,696
Prepaid expenses and other current assets	4,136	2,556
Total current assets	161,866	74,505
Restricted cash	1,500	1,500
Property and equipment, net	4,896	2,385
Operating lease right-of-use assets	4,557	4,726
Other non-current assets	92	67
TOTAL ASSETS	172,911	83,183
CURRENT LIABILITIES
Accounts payable	4,151	3,154
Operating lease liabilities	228	351
Accrued and other current liabilities	11,511	14,854
Total current liabilities	15,890	18,359
Non-current operating lease liabilities	4,695	4,712
Other non-current liabilities	68	31
TOTAL LIABILITIES	20,653	23,102
Commitments and Contingencies (Note 8)
STOCKHOLDERS’ EQUITY
Preferred stock, $0.0001 par value; 10,000,000 shares authorized as of June 30, 2020 and December 31, 2019; no shares issued and outstanding as of June 30, 2020 and December 31, 2019
Common stock, $0.0001 par value; 500,000,000 shares authorized as of June 30, 2020 and December 31, 2019; 44,599,847 shares and 29,084,437 shares issued and outstanding as of June 30, 2020 and December 31, 2019, respectively	5	3
Additional paid-in capital	387,475	255,142
Accumulated other comprehensive income	39	51
Accumulated deficit	(235,261)	(195,115)
TOTAL STOCKHOLDERS’ EQUITY	152,258	60,081
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 172,911	$ 83,183