Sale of future royalties (Tables)

12 Months Ended

Dec. 31, 2020

Other Liabilities Disclosure [Abstract]

Activity related to net liability

The table below shows the activity related to the net liability for the years ended December 31, 2020 and December 31, 2019:

	Twelve Months Ended December 31,
	2020		2019
	(in thousands)
Net liability related to sale of future royalties - beginning balance	$	18,992	$	—
Initial recognition of liability	—		30,000
Debt discount and issuance costs	—		(11,451)
Non-cash royalty revenue	(3,395)		(1,656)
Non-cash interest expense	3,957		2,099
Net liability related to sale of future royalties - ending balance	$	19,554	$	18,992