Intangible Assets, Net

9 Months Ended

Sep. 30, 2019

Goodwill And Intangible Assets Disclosure [Abstract]

Intangible Assets, Net

6. Intangible Assets, net

The following table presents intangible assets (in thousands):

	September 30,			December 31,			Estimated
	2019			2018			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		(7,733	)		(3,348	)
Total intangible assets, net	$	84,529		$	88,914

We recorded $1.5 million and $4.4 million, respectively, in amortization expense related to intangible assets during the three and nine months ended September 30, 2019. For the three and nine months ended September 30, 2018, we recorded $0.7 million and $0.8 million, respectively. Estimated future amortization expense for intangible assets as of September 30, 2019 is as follows (in thousands):

	Total
2019	$	1,478
2020		5,879
2021		5,861
2022		5,856
2023		5,843
Thereafter		59,612
	$	84,529

The weighted average remaining amortizable life of our patents was 11.05 years at September 30, 2019.

For additional detail of Akcea's license agreements with Ionis see Note 8, License Agreements and Services Agreement with Ionis.