
	2025						2024
	Gross Carrying Amount		Accumulated Amortization		Net		Gross Carrying Amount		Accumulated Amortization		Net
Product rights	$	42,038	$	20,710	$	21,328	$	29,988	$	19,066	$	10,922
IPR&D	427		—		427		430		—		430
Trade names	2,881		1,158		1,723		2,881		954		1,927
Licenses and other	10,064		6,861		3,203		8,863		5,772		3,091
	$	55,410	$	28,729	$	26,681	$	42,162	$	25,792	$	16,370

Some of the more significant acquired intangibles included in product rights, on a net basis, related to human health marketed products at December 31, 2025 were Ohtuvayre $11.8 billion; Winrevair, $5.4 billion; and Reblozyl, $2.5 billion. Additionally, the Company had $3.7 billion of net acquired intangibles related to animal health at December 31, 2025, of which $1.3 billion related to product rights and $1.7 billion was attributable to trade names, primarily related to Allflex. At December 31, 2025, IPR&D primarily relates to MK-1026 (nemtabrutinib), obtained through the 2020 acquisition of ArQule, Inc., which had a balance of $418 million. Some of the more significant net intangible assets included in licenses and other above at December 31, 2025 include Keytruda Qlex $886 million, related to a license agreement with Alteogen; Lynparza, $844 million, related to a collaboration with AstraZeneca;

Lenvima, $201 million, related to a collaboration with Eisai; and Adempas, $280 million, related to a collaboration with Bayer. See Note 3 for additional information related to the intangible asset associated with the license agreement and Note 4 for additional information related to the intangible assets associated with the collaborations.

IPR&D that the Company acquires through business combinations represents the fair value assigned to incomplete research projects which, at the time of acquisition, have not reached technological feasibility. Amounts capitalized as IPR&D are accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of the projects. Upon successful completion of each IPR&D project, the Company will make a separate determination as to the then-useful life of the asset and begin amortization.

In 2023, the Company recorded a $779 million IPR&D impairment charge within Research and development expenses related to MK-7264, gefapixant, a non-narcotic, oral selective P2X3 receptor antagonist, that was in development for the treatment of refractory or unexplained chronic cough in adults. In December 2023, the FDA issued a Complete Response Letter (CRL) regarding the resubmission of Merck’s New Drug Application (NDA) for gefapixant. In the CRL, the FDA concluded that Merck’s application did not meet substantial evidence of effectiveness for treating refractory chronic cough and unexplained chronic cough. The CRL was not related to the safety of gefapixant. The marketing application for gefapixant was based on results from the COUGH-1 and COUGH-2 clinical trials. In January 2022, the FDA issued a CRL regarding Merck’s original NDA for gefapixant. In that CRL, the FDA requested additional information related to the cough counting system that was used to assess efficacy. Receipt of the second CRL from the FDA constituted a triggering event that required the evaluation of the gefapixant intangible asset for impairment. The Company estimated the current fair value of gefapixant utilizing an income approach, which calculates the present value of projected future cash flows. The market participant assumptions used to derive the forecasted cash flows were updated to reflect revised market launch plans, resulting in a reduction in the estimated fair value. The revised estimated fair value of gefapixant when compared with its related carrying value resulted in the impairment charge noted above.

Aggregate amortization expense primarily recorded within Cost of sales was $2.8 billion in 2025, $2.4 billion in 2024 and $2.0 billion in 2023. The estimated aggregate amortization expense for each of the next five years is as follows: 2026, $3.8 billion; 2027, $3.6 billion; 2028, $3.3 billion; 2029, $3.0 billion; 2030, $2.7 billion.