Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 63,049	$ 32,936
Marketable securities	3,000	35,209
Accounts receivable	211	250
Inventory	90	113
Prepaid expenses and other current assets	1,978	1,390
Total current assets	68,328	69,898
Property and equipment, net	9,619	3,313
Restricted cash	1,728	1,728
Total assets	79,675	74,939
Current liabilities:
Accounts payable	6,307	2,116
Accrued expenses and deferred rent	4,379	4,635
Notes payable, net of discount, current	2,444	1,549
Total current liabilities	13,130	8,300
Deferred rent, long-term	3,146	537
Notes payable, net of discount, long-term	15,374	14,094
Total liabilities	31,650	22,931
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized at June 30, 2017 and December 31, 2016; no shares issued or outstanding at June 30, 2017 and December 31, 2016
Common stock, $0.0001 par value; 100,000,000 shares authorized at June 30, 2017 and December 31, 2016; 29,055,460 and 25,024,100 shares issued and outstanding at June 30, 2017 and December 31, 2016, respectively	3	3
Additional paid-in capital	256,618	225,889
Accumulated deficit	(208,596)	(173,879)
Accumulated other comprehensive loss		(5)
Total stockholders' equity	48,025	52,008
Total liabilities and stockholders' equity	$ 79,675	$ 74,939