CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net loss	$ (107,500)	$ (33,693)	$ (29,029)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	219	208	285
Share-based compensation	1,237	1,283	1,381
Change in fair value of contingent consideration	71,620	8,800	9,100
Gain on sale of equipment	0	(5)	(108)
Other	0	0	(5)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(5,188)	(913)	164
Accounts payable	535	460	(760)
Accrued expenses and other liabilities	1,556	1,031	1,746
Deferred revenue	0	0	(425)
Due to related party	0	0	(114)
Net Cash Used in Operating Activities	(37,521)	(22,829)	(17,765)
Cash Flows from Investing Activities:
(Purchases) sales of property and equipment	136	2
(Purchases) sales of property and equipment			98
Net Cash (Used in) Provided by Investing Activities	(136)	(2)	98
Cash Flows from Financing Activities:
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	27,833	50,971	6,908
Proceeds from exercises of common stock warrants	5,481	7,315	45
Proceeds from issuance of common stock under ATM Offering, net of issuance costs	1,936	0	0
Proceeds from exercises of stock options	98	277	40
Proceeds from sales of common stock under 2014 ESPP	8	20	12
Net Cash Provided by Financing Activities	35,356	58,583	7,005
Net (Decrease) Increase in Cash, Cash Equivalents and Restricted Cash	(2,301)	35,752	(10,662)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	50,442	14,690	25,352
Cash, Cash Equivalents and Restricted Cash - End of Period	48,141	50,442	14,690
Supplemental disclosure of non-cash operating activities:
Right-of-use assets related to the adoption of ASC 842	236
Cash paid for amounts included in the measurement of lease liabilities	153
Supplemental disclosure of non-cash investing activities:
Adjustment to fair value of assets acquired and liabilities assumed in acquisition during provisional period	0	0	14,600
Supplemental disclosure of non-cash financing activities:
Issuance of pre-funded warrants to purchase common stock	$ 0	$ 0	$ 2,679