Revenue (Tables)

12 Months Ended

Dec. 31, 2020

Revenue

Summary of revenue by type

	Year ended December 31,
(in thousands)	2018		2019		2020
Product revenue, net	$	—	$	1,538	$	108
Collaboration revenues		6,500		6,210		2,756
Research premium		2,594		1,311		1,227
Government grants		562		422		936
Total	$	9,656	$	9,481	$	5,027

Summary of gross-to-net ("GTN") adjustments

	Year Ended December 31,
(in thousands)	2019		2020
Product revenue, gross	$	2,173	$	484
GTN accruals
Chargebacks and cash discounts		48		16
Medicaid and Medicare rebates		223		52
Other returns, rebates, discounts and adjustments		364		115
Total GTN accruals		(635)		(183)
Product revenue		1,538		301
Adjustments to prior period accruals
Returns reserve (1)		—		(421)
GTN accrual adjustments		—		228
Product revenue, net	$	1,538	$	108