CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 31,228,192	$ 15,431,622
Short-term investments	106,979,224	158,168,832
Receivables	55,074	8,678
Prepaid expenses	1,737,308	772,579
Other assets	255,912	493,863
Total current assets	140,255,710	174,875,574
Property and equipment, net	3,205,077	3,398,398
Other noncurrent assets	33,567	111,605
Total assets	143,494,354	178,385,577
Current liabilities:
Accounts payable	1,381,545	1,262,565
Accrued wages and benefits	2,705,475	3,272,237
Accrued clinical trial expenses	861,293	804,066
Accrued expenses and other liabilities	613,861	850,125
Total current liabilities	5,562,174	6,188,993
Other liabilities, net of current portion	2,873	18,503
Deferred revenue, net of current portion	781,944	831,944
Total liabilities	6,346,991	7,039,440
Stockholders’ equity:
Common stock: $0.001 par value, 100,000,000 shares authorized; 42,034,733 and 42,377,522 shares issued and outstanding at December 31, 2015 and December 31, 2016	42,378	42,035
Additional paid-in capital	390,768,742	381,118,489
Accumulated other comprehensive (loss) income	(41,196)	(79,399)
Retained deficit	(253,622,561)	(209,734,988)
Total stockholders’ equity	137,147,363	171,346,137
Total liabilities and stockholders’ equity	$ 143,494,354	$ 178,385,577