Balance Sheets - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 13,876,090	$ 9,912,674
Marketable securities	22,632,019	27,159,272
Prepaid and other current assets	1,982,031	796,818
Total current assets	38,490,140	37,868,764
Property and equipment, net	344,734	237,066
Other assets	892,394	342,051
Total assets	39,727,268	38,447,881
Current liabilities:
Accounts payable and accrued expenses	2,545,894	3,003,612
Accrued compensation	1,436,804	1,171,621
Total current liabilities	3,982,698	4,175,233
Note payable	1,000,000	1,000,000
Deferred rent	$ 204,224	$ 58,699
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.0001 par value; 200,000,000 shares authorized; 19,877,857 shares issued and 19,845,611 shares outstanding, excluding 32,246 shares subject to repurchase, at December 31, 2015; 15,695,834 shares issued and 15,560,614 shares outstanding, excluding 135,220 shares subject to repurchase, at December 31, 2014	$ 1,984	$ 1,556
Additional paid-in capital	155,441,280	129,976,075
Accumulated other comprehensive loss	(3,907)	(13,297)
Accumulated deficit	(120,899,011)	(96,750,385)
Total stockholders’ equity	34,540,346	33,213,949
Total liabilities and stockholders’ equity	$ 39,727,268	$ 38,447,881