Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 54,682	$ 32,936
Marketable securities	25,697	35,209
Accounts receivable	244	250
Inventory	96	113
Prepaid expenses and other current assets	2,557	1,390
Total current assets	83,276	69,898
Property and equipment, net	5,693	3,313
Restricted cash	1,728	1,728
Total assets	90,697	74,939
Current liabilities:
Accounts payable	3,754	2,116
Accrued expenses and deferred rent	4,005	4,635
Notes payable, net of discount, current	897	1,549
Total current liabilities	8,656	8,300
Deferred rent, long-term	1,315	537
Notes payable, net of discount, long-term	16,821	14,094
Total liabilities	26,792	22,931
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized at March 31, 2017 and December 31, 2016; no shares issued or outstanding at March 31, 2017 and December 31, 2016
Common stock, $0.0001 par value; 100,000,000 shares authorized at March 31, 2017 and December 31, 2016; 28,934,454 and 25,024,100 shares issued and outstanding at March 31, 2017 and December 31, 2016, respectively	3	3
Additional paid-in capital	253,813	225,889
Accumulated deficit	(189,902)	(173,879)
Accumulated other comprehensive loss	(9)	(5)
Total stockholders' equity	63,905	52,008
Total liabilities and stockholders' equity	$ 90,697	$ 74,939