Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
CURRENT ASSETS
Cash and cash equivalents	$ 54,223	$ 19,253
Marketable securities	85,753	52,696
Prepaid expenses and other current assets	4,423	2,556
Total current assets	144,399	74,505
Restricted cash	1,500	1,500
Property and equipment, net	5,216	2,385
Operating lease right-of-use assets	4,394	4,726
Other non-current assets	122	67
TOTAL ASSETS	155,631	83,183
CURRENT LIABILITIES
Accounts payable	2,295	3,154
Operating lease liabilities	341	351
Accrued and other current liabilities	11,713	14,854
Total current liabilities	14,349	18,359
Non-current operating lease liabilities	4,947	4,712
Other non-current liabilities	61	31
TOTAL LIABILITIES	19,357	23,102
Commitments and Contingencies (Note 8)
STOCKHOLDERS’ EQUITY
Preferred stock, $0.0001 par value; 10,000,000 shares authorized as of September 30, 2020 and December 31, 2019; no shares issued and outstanding as of September 30, 2020 and December 31, 2019
Common stock, $0.0001 par value; 500,000,000 shares authorized as of September 30, 2020 and December 31, 2019; 44,692,030 shares and 29,084,437 shares issued and outstanding as of September 30, 2020 and December 31, 2019, respectively	5	3
Additional paid-in capital	389,543	255,142
Accumulated other comprehensive income	20	51
Accumulated deficit	(253,294)	(195,115)
TOTAL STOCKHOLDERS’ EQUITY	136,274	60,081
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 155,631	$ 83,183