Intangible Assets, Net

6 Months Ended

Jun. 30, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Intangible Assets, Net

8. Intangible Assets, net

The following table presents intangible assets (in thousands):

	June 30,			December 31,			Estimated
	2020			2019			useful life
Acquired and in-licensed rights	$	2,262		$	2,262		7 - 21 Years
Capitalized regulatory approval milestones		90,000			90,000		16 Years
Less accumulated amortization		(12,135	)		(9,211	)
Total intangible assets, net	$	80,127		$	83,051

We recorded $1.4 million and $2.9 million, respectively, in amortization expense related to intangible assets during the three and six months ended June 30, 2020. For the same periods in 2019, we recorded $1.5 million and $2.9 million, respectively. Estimated future amortization expense for intangible assets as of June 30, 2020 is as follows (in thousands):

Years ended December 31,	Intangible Assets
Remainder of 2020	$	2,955
2021		5,861
2022		5,856
2023		5,843
2024		5,822
Thereafter		53,790
	$	80,127

The weighted average remaining amortizable life of our patents was 10.6 years at June 30, 2020.

For additional detail of our license agreements with Ionis, see Note 9, License Agreements and Services Agreement with Ionis.