REVENUES (Tables)

12 Months Ended

Dec. 31, 2020

REVENUES

Schedule of revenues disaggregated by category

Revenues disaggregated by category were as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
Product sales:
Gross product sales	$	76,470	$	53,082	$	16,953
Discounts and allowances		(14,774)		(9,310)		(3,006)
Product sales, net	$	61,696	$	43,772	$	13,947
Revenues from collaborations:
License revenues		40,358	$	8,696		30,562
Development milestones		2,100		5,500		—
Research and development services and others		4,467		1,320		—
Total revenues from collaborations		46,925		15,516		30,562
Total revenues	$	108,621	$	59,288	$	44,509

Customer revenues (as a percentage of gross revenues)

The following table summarizes revenues from each of our customers who individually accounted for 10% or more (wherein * denotes less than 10%) of our gross revenues (as a percentage of gross revenues):

	Year Ended December 31,
	2020		2019		2018
Grifols		41%		*		—
ASD Healthcare and Oncology Supply		30%		37%		17%
McKesson Specialty Care Distribution Corporation		23%		30%		11%
Kissei		—		*		69%

Schedule of product revenue allowance and reserve categories

The following tables summarize the activities in chargebacks, discounts and fees, government and other rebates and returns during the years ended December 31, 2020 and 2019 (in thousands):

	Chargebacks,		Government
	Discounts and		and Other
	Fees		Rebates		Returns		Total
Balance at January 1, 2020	$	1,293	$	1,801	$	238	$	3,332
Provision related to current period sales		8,149		4,231		950		13,330
Adjustment related to prior period sales		(75)		(490)		565		—
Credit or payments made during the period		(6,906)		(3,427)		(264)		(10,597)
Balance at December 31, 2020	$	2,461	$	2,115	$	1,489	$	6,065

	Chargebacks,		Government
	Discounts and		and Other
	Fees		Rebates		Returns		Total
Balance at January 1, 2019	$	623	$	843	$	170	$	1,636
Provision related to current period sales		5,170		2,864		99		8,133
Credit or payments made during the period		(4,500)		(1,906)		(31)		(6,437)
Balance at December 31, 2019	$	1,293	$	1,801	$	238	$	3,332