Goodwill and Intangible Assets

Goodwill

The following table summarizes the changes in the carrying amount of goodwill:



(in millions)
Balance as of December 31, 2018	$	15,663
Foreign currency translation adjustments	(57		)
Balance as of March 31, 2019	$	15,606

The company performs its annual goodwill impairment assessment in the third quarter, or earlier if impairment indicators exist. As of March 31, 2019, there were no accumulated goodwill impairment losses.

Intangible Assets, Net

The following table summarizes intangible assets:



	March 31, 2019							December 31, 2018
(in millions)	Gross carrying amount		Accumulated amortization			Net carrying amount		Gross carrying amount		Accumulated amortization			Net carrying amount
Definite-lived intangible assets
Developed product rights	$	15,865	$	(5,857	)	$	10,008	$	15,872	$	(5,614	)	$	10,258
License agreements	7,865		(1,947		)	5,918		7,865		(1,810		)	6,055
Total definite-lived intangible assets	23,730		(7,804		)	15,926		23,737		(7,424		)	16,313
Indefinite-lived research and development	4,920		—			4,920		4,920		—			4,920
Total intangible assets, net	$	28,650	$	(7,804	)	$	20,846	$	28,657	$	(7,424	)	$	21,233

Indefinite-Lived Intangible Assets

Indefinite-lived intangible assets represent acquired IPR&D associated with products that have not yet received regulatory approval. Indefinite-lived intangible assets as of March 31, 2019 and December 31, 2018 relate to the 2016 acquisitions of Boehringer Ingelheim compounds and Stemcentrx. The company performs its annual impairment assessment of indefinite-lived intangible assets in the third quarter, or earlier if impairment indicators exist. No indefinite-lived intangible asset impairment charges were recorded for the three months ended March 31, 2019 and 2018.

In the fourth quarter of 2018, the company recorded an impairment charge of $5.1 billion related to IPR&D acquired as part of the 2016 Stemcentrx acquisition following the decision to stop enrollment in the TAHOE trial. AbbVie continues to evaluate information as it becomes available with respect to the Stemcentrx-related clinical development programs and will monitor the remaining $1.0 billion of IPR&D assets for further impairment.

Definite-Lived Intangible Assets

Amortization expense was $385 million for the three months ended March 31, 2019 and $330 million for the three months ended March 31, 2018. Amortization expense was included in cost of products sold in the condensed consolidated statements of earnings. No definite-lived intangible asset impairment charges were recorded for the three months ended March 31, 2019 and 2018.