Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and cash equivalents	$ 12,594	$ 19,253
Marketable securities	36,398	52,696
Prepaid expenses and other current assets	5,273	2,556
Total current assets	54,265	74,505
Restricted cash	1,500	1,500
Property and equipment, net	4,244	2,385
Operating lease right-of-use assets	4,712	4,726
Other non-current assets	60	67
TOTAL ASSETS	64,781	83,183
CURRENT LIABILITIES
Accounts payable	3,618	3,154
Operating lease liabilities	293	351
Accrued and other current liabilities	13,227	14,854
Total current liabilities	17,138	18,359
Non-current operating lease liabilities	4,815	4,712
Other non-current liabilities	23	31
TOTAL LIABILITIES	21,976	23,102
Commitments and Contingencies (Note 8)
STOCKHOLDERS’ EQUITY
Preferred stock, $0.0001 par value; 10,000,000 shares authorized as of March 31, 2020 and December 31, 2019; no shares issued and outstanding as of March 31, 2020 and December 31, 2019
Common stock, $0.0001 par value; 500,000,000 shares authorized as of March 31, 2020 and December 31, 2019; 29,147,461 shares and 29,084,437 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	3	3
Additional paid-in capital	256,779	255,142
Accumulated other comprehensive (loss) income	(134)	51
Accumulated deficit	(213,843)	(195,115)
TOTAL STOCKHOLDERS’ EQUITY	42,805	60,081
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 64,781	$ 83,183