CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues, net:
Total revenues, net	$ 2,709	$ 1,767
Costs and expenses:
Cost of royalties	125	108
Research and development	7,473	4,074
General and administrative	3,593	3,143
Total costs and expenses	11,191	7,325
Loss from operations	(8,482)	(5,558)
Other expense:
Loss on debt extinguishment	0	(3,495)
Interest income	50	108
Imputed interest expense related to the sale of future royalties	(1,298)	(131)
Interest expense, debt	0	(791)
Other income (expense), net	21	(17)
Total other expense	(1,227)	(4,326)
Net loss	$ (9,709)	$ (9,884)
Net loss per common share (basic and diluted) (USD per share)	$ (0.28)	$ (0.30)
Weighted average common shares (basic and diluted) (shares)	34,453,189	33,150,869
Unrealized gain on marketable securities	$ 0	$ 0
Comprehensive loss	(9,709)	(9,884)
Royalties
Revenues, net:
Total revenues, net	2,515	2,137
Other revenue
Revenues, net:
Total revenues, net	211	0
Contra revenue, net
Revenues, net:
Total revenues, net	$ (17)	$ (370)