CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 103,986	$ 56,461
Marketable securities		1,498
Prepaid expenses and other current assets	2,201	1,242
Total current assets	106,187	59,201
Property and equipment, net	2,626	2,181
Restricted cash	205	205
Other long-term assets		50
Total assets	109,018	61,637
Current liabilities:
Accounts payable	1,809	1,359
Accrued expenses	3,360	2,796
Deferred rent		228
Loan payable	578	641
Capital lease payable	14
Total current liabilities	5,761	5,024
Long-term portion of deferred rent	886	468
Long-term portion of loan payable		398
Long-term portion of capital lease payable	28
Warrant to purchase redeemable security		37
Total liabilities	6,675	5,927
Commitments and contingencies (Note 9)
Convertible preferred stock (Series A-1, A-2, A-3, A-4, B and C), $0.001 par value; no shares authorized, issued or outstanding as of September 30, 2018; 43,157,651 shares authorized and 43,135,911 shares issued and outstanding as of December 31, 2017 (aggregate liquidation preference of $109,561 as of December 31, 2017)		109,232
Stockholders’ equity (deficit):
Preferred stock, $0.001 par value; 10,000,000 and no shares authorized at September 30, 2018 and December 31, 2017, respectively; no shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively
Common stock, $0.001 par value; 150,000,000 shares authorized and 25,241,766 shares issued and outstanding as of September 30, 2018; 60,000,000 shares authorized and 3,970,586 shares issued and outstanding as of December 31, 2017	25	4
Additional paid-in capital	194,204	4,001
Accumulated other comprehensive loss		(2)
Accumulated deficit	(91,886)	(57,525)
Total stockholders’ equity (deficit)	102,343	(53,522)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 109,018	$ 61,637