Liabilities Related to the Sales of Future Royalties (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Liability Related to Potential Future Royalties

The following table shows the activity within the liability account during the year ended December 31, 2020 and for the period from the inception of the 2012 Purchase and Sale Agreement on February 24, 2012 (inception) and the 2020 Purchase and Sale Agreement on December 30, 2020 to December 31, 2020 (in thousands):


	Year-Ended December 31, 2020						Period from inception to December 31, 2020
	2012 Purchase and Sale Agreement		2020 Purchase and Sale Agreement		Total		2012 Purchase and Sale Agreement		2020 Purchase and Sale Agreement		Total
Liability related to the sale of future royalties—beginning balance	$	73,551	$	—	$	73,551	$	—	$	—	$	—
Royalty monetization proceeds	—		150,000		150,000		124,000		150,000		274,000
Non-cash royalty revenue	(37,938)		(10,625)		(48,563)		(245,080)		(10,625)		(255,705)
Non-cash interest expense	30,267		—		30,267		196,960		—		196,960
Payments to RPI	—		—		—		(10,000)		—		(10,000)
Liability related to the sale of future royalties – ending balance	65,880		139,375		205,255		65,880		139,375		205,255
Less: unamortized transaction costs	(1,165)		(3,750)		(4,915)		(1,165)		(3,750)		(4,915)
Liability related to the sale of future royalties, net	$	64,715	$	135,625	$	200,340	$	64,715	$	135,625	$	200,340

The following table presents our estimates of the annual interest rates over the lives of the agreements and the resulting prospective interest rates used to recognize non-cash interest expense for the years ended December 31, 2020, 2019 and 2018.


	2012 Purchase and Sale Agreement						2020 Purchase and Sale Agreement
	Year-Ended December 31,						Year-Ended December 31,
	2020		2019		2018		2020
Interest rates - end of period presented
Implicit interest rate over the life of the agreement	20.2	%	19.5	%	18.7	%	16.0	%
Prospective effective interest rate	48.0	%	38.0	%	29.0	%	16.0	%