Intangible assets

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets, net of accumulated amortization, are summarized as follows (in thousands):


	As of December 31,										As of December 31,
	2019										2018
	Cost		Accumulated amortization		Net		Cost		Accumulated amortization		Net
Developed technology	$	30,100	$	(20,694)	$	9,406	$	30,100	$	(16,931)	$	13,169
In-licensed rights	5,224		(304)		4,920		—		—		—
Total	$	35,324	$	(20,998)	$	14,326	$	30,100	$	(16,931)	$	13,169

Amortization expense for intangible assets was $4.1 million, $3.8 million, and $3.8 million for each of the years ended December 31, 2019, 2018 and 2017, respectively.

Developed technology

The Company's developed technology was obtained through its acquisition of Pregenen, a privately-held biotechnology company. As a result, the Company obtained gene editing and cell signaling technology with a broad range of potential therapeutic applications. The Company considered the intangible asset acquired to be developed technology, as at the date of the acquisition it could be used the way it was intended to be used in certain ongoing research and development activities. The gene editing platform intangible asset is being amortized on a straight-line basis over its expected useful life of approximately eight years from the date of the acquisition. Please refer to Note 4, Fair value measurements, and Note 9, Commitments and contingencies, for further information.

In-licensed rights

In-licensed rights consist of capitalized milestone payments made to third parties upon receiving regulatory approval of ZYNTEGLO in the EU. The in-licensed rights are being amortized on a straight-line basis over the remaining life of the related patents of approximately ten years, as the life of the related patents reflects the expected time period that the Company will benefit from the in-licensed rights.

The following table summarizes the estimated future amortization for intangible assets for the next five years (in thousands):


	As of December 31, 2019
2020	$	4,285
2021	4,285
2022	2,404
2023	522
2024	522
Total	$	12,018