CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net loss	$ (9,999,537)	$ (10,262,518)
Adjustments to reconcile net loss to net cash used in operating activities:
Impairment loss	485,000	0
Depreciation and amortization	330,968	156,821
Stock based compensation expense	920,799	2,811,108
Accretion of final fee premium	125,012	93,062
Amortization of discount on debt	68,223	27,631
Amortization of premiums on short-term investments	10,877	0
Deferred rent	(66,119)	0
Interest income accrued on short-term investments	151,583	0
Change in fair value of derivative financial instruments—warrants	(555,506)	(533,750)
Changes in operating assets and liabilities:
Decrease in other assets	0	2,761
Decrease in accounts receivable	20,112	36,801
Decrease (increase) in prepaid expenses	110,957	(51,272)
(Decrease) increase in accounts payable and accrued expenses	(360,577)	1,072,343
Decrease in other liabilities	0	(268,694)
Net cash used in operating activities	(8,758,208)	(6,915,707)
Investing activities:
Capital expenditures, net	(11,452)	(352,023)
Maturities of short-term investments	14,000,000	0
Purchases of short-term investments	(8,804,604)	0
Net cash provided by (used in) investing activities	5,183,944	(352,023)
Financing activities:
Proceeds from exercise of options	0	133,613
Borrowings under equipment line of credit	0	550,297
Repayments of long-term debt	0	(919,864)
Repayments of equipment line of credit	(156,526)	0
Net cash used in financing activities	(156,526)	(235,954)
Effect of exchange rate changes on cash and cash equivalents	(844)	(34)
Net change in cash and equivalents	(3,731,634)	(7,503,718)
Cash and cash equivalents—Beginning of period	13,915,094	67,493,047
Cash and cash equivalents—End of period	10,183,460	59,989,329
Supplementary disclosure of cash flow activity:
Cash paid for interest	300,040	276,214
Supplemental disclosure of non-cash investing and financing activities:
Preferred stock dividends accrued	6,060	6,060
Leasehold improvements paid for by lessor	$ 0	$ 1,860,000