CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 26,588,400	$ 15,431,622
Short-term investments	128,020,599	158,168,832
Receivables	2,469	8,678
Prepaid expenses	968,185	772,579
Other assets	259,788	493,863
Total current assets	155,839,441	174,875,574
Property and equipment, net	3,506,192	3,398,398
Other noncurrent assets	61,496	111,605
Total assets	159,407,129	178,385,577
Current liabilities:
Accounts payable	1,360,079	1,262,565
Accrued wages and benefits	1,677,090	3,272,237
Accrued clinical trial expenses	885,220	804,066
Accrued expenses and other liabilities	621,707	850,125
Total current liabilities	4,544,096	6,188,993
Other liabilities, net of current portion	11,483	18,503
Deferred revenue, net of current portion	806,944	831,944
Total liabilities	5,362,523	7,039,440
Stockholders’ equity:
Common stock: $0.001 par value, 100,000,000 shares authorized; 42,034,733 and 42,252,598 shares issued and outstanding at December 31, 2015 and June 30, 2016	42,253	42,035
Additional paid-in capital	387,756,495	381,118,489
Accumulated other comprehensive (loss) income	96,246	(79,399)
Retained deficit	(233,850,388)	(209,734,988)
Total stockholders’ equity	154,044,606	171,346,137
Total liabilities and stockholders’ equity	$ 159,407,129	$ 178,385,577