Consolidated Balance Sheets - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 56,717,847	$ 25,031,280
Short-term investment securities	27,998,810	19,853,860
Interest receivable	108,468	83,852
Prepaid research and development	8,055,486	5,678,755
Other current assets	436,789	216,397
Total current assets	93,317,400	50,864,144
Restricted cash	587,291	583,208
Leasehold interest, net	2,429,434	2,042,281
Equipment, net	248,020	328,148
Goodwill	799,391	799,391
Other assets	0	164,375
Total assets	97,381,536	54,781,547
Current liabilities:
Accounts payable and accrued expenses	25,877,218	15,267,668
Accrued compensation	1,800,000	1,389,516
Current portion of deferred revenue	152,381	152,381
Notes payable	127,614	68,875
Total current liabilities	27,957,213	16,878,440
Deferred rent	1,364,601	816,257
Deferred revenue, net of current portion	1,066,667	1,219,048
Total liabilities	30,388,481	18,913,745
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value per share (10,000,000 shares authorized, none issued and outstanding as of December 31, 2017 and 2016)	0	0
Common stock, $0.001 par value per share (150,000,000 shares authorized, 73,181,750 and 56,820,422 shares issued, 73,140,441 and 56,779,113 shares outstanding at December 31, 2017 and 2016, respectively)	73,182	56,820
Additional paid-in capital	422,017,042	272,432,139
Treasury stock, at cost, 41,309 shares at December 31, 2016 and 2015	(234,337)	(234,337)
Accumulated deficit	(354,862,832)	(236,386,820)
Total stockholders' equity	66,993,055	35,867,802
Total liabilities and stockholders' equity	$ 97,381,536	$ 54,781,547