Intangible Assets

The following table summarizes the Company's intangible assets:



(In millions)	Currently marketed products			IPR&D		Other intangible assets			Total
September 30, 2017
Gross acquired intangible assets	$	31,786.3		$	5,113.0	$	840.3		$	37,739.6
Accumulated amortization	(4,094.0		)	—		(295.3		)	(4,389.3		)
Intangible assets, net	$	27,692.3		$	5,113.0	$	545.0		$	33,350.3

December 31, 2016
Gross acquired intangible assets	$	31,217.5		$	5,746.6	$	842.2		$	37,806.3
Accumulated amortization	(2,908.6		)	—		(200.2		)	(3,108.8		)
Intangible assets, net	$	28,308.9		$	5,746.6	$	642.0		$	34,697.5

Other intangible assets are comprised primarily of royalty rights and other contract rights associated with Baxalta, Dyax and NPS.

The change in the net book value of intangible assets for the nine months ended September 30, 2017 and 2016 is shown in the table below:



(In millions)	2017			2016
As of January 1,	$	34,697.5		$	9,173.3
Acquisitions	(1,397.0		)	30,377.7
Amortization charged	(1,280.5		)	(702.5		)
Impairment charges	(20.0		)	(8.9		)
Foreign currency translation	1,350.3			31.9
As of September 30,	$	33,350.3		$	38,871.5

The decrease in Intangible assets, net during the nine months ended September 30, 2017 relates to the measurement period adjustments of the acquisition of Baxalta and amortization of intangible assets. For a more detailed description of measurement period adjustments, refer to Note 2, Business Combinations, to these Unaudited Consolidated Financial Statements.

In connection with the acquisition of Baxalta, the Company acquired IP rights related to currently marketed products of $21,165.0 million, IPR&D assets of $160.0 million and other contract rights of $42.2 million. For a more detailed description of this acquisition, refer to Note 2, Business Combinations, to these Unaudited Consolidated Financial Statements.

In connection with the acquisition of Dyax on January 22, 2016, the Company acquired IP rights related to currently marketed products of $135.0 million, IPR&D assets of $4,100.0 million and royalty rights of $425.0 million. For a more detailed description of this acquisition, refer to Note 2, Business Combinations, to these Unaudited Consolidated Financial Statements.

The Company reviews its amortized intangible assets for impairment whenever events or circumstances suggest that their carrying value may not be recoverable. Unamortized intangible assets are reviewed for impairment annually or whenever events or circumstances suggest that their carrying value may not be recoverable.

Estimated amortization expense can be affected by various factors including future acquisitions, disposals of product rights, regulatory approval and subsequent amortization of acquired IPR&D projects, foreign exchange movements and the technological advancement and regulatory approval of competitor products. The estimated future amortization of acquired intangible assets for the next five years is expected to be as follows:



(In millions)	Anticipated future amortization
2017 (remaining three months)	$	476.5
2018	1,879.3
2019	1,656.1
2020	1,558.1
2021	1,524.6
2022	1,509.0