Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (56,080,593)	$ (29,747,724)
Adjustments to reconcile net loss to net cash used in operating activities:
Noncash stock compensation expense	7,485,183	3,347,362
Depreciation	41,070	23,319
Amortization of premium on investment securities	44,930	254,132
Change in fair value of notes payable	83,693	(90,384)
Changes in assets and liabilities:
Increase in restricted cash	(2,021)	(2,018)
Increase in other current assets	(4,251,493)	(5,700,293)
Decrease (increase) in leasehold interest	75,032	(1,968,734)
Decrease (increase) in accrued interest receivable	40,562	52,255
Decrease in other assets	395,375	(9,518)
Increase in accounts payable and accrued expenses	3,067,915	3,712,012
Increase in deferred rent	44,578	681,720
Decrease in deferred revenue	(76,191)	(76,191)
Net cash used in operating activities	(49,131,960)	(29,524,062)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property, plant and equipment	(2,227)	(310,056)
Investment in held-to-maturity securities	0	(15,199,922)
Proceeds from maturity of short-term securities	11,000,000	15,000,000
Net cash provided by (used in) investing activities	10,997,773	(509,978)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the exercise of warrants	2,143,083	50,271
Proceeds from sale of common stock, net	88,562,187	3,504,261
Financing costs	0	(3,989)
Net cash provided by financing activities	90,705,270	3,550,543
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	52,571,083	(26,483,497)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	25,031,280	55,061,329
CASH AND CASH EQUIVALENTS AT END OF PERIOD	77,602,363	28,577,832
NONCASH TRANSACTIONS
Accrued financing costs	233,646	0
Reclassification of deferred financing costs to additional paid-in capital	(2,645)	(56,988)
Conversion of convertible notes payable to common stock	$ 0	$ 30,601