Who Merck buys from and sells to
Sells prescription drugs and vaccines, led by Keytruda, Gardasil and Winrevair, plus animal health.
Buys from 2
- Daiichi SankyoDSNKYDXd antibody-drug conjugates under a co-development deal
- WuXi AppTecresearch and manufacturing services in China
Sells to 4
- McKessonMCKdrug and vaccine wholesale in the US22% of receivables (FY2025 10-K)
- CencoraCORdrug wholesale in the US21% of receivables (FY2025 10-K)
- Cardinal HealthCAHdrug wholesale in the US13% of receivables (FY2025 10-K)
- US federal governmentpediatric vaccines bought through CDC programs
Where the chain could break
- Keytruda was 49% of 2025 sales, with US patent expiry from 2028
- Significant research and manufacturing in China exposed to US-China tensions
Competes with
- Bristol Myers SquibbBMYOpdivo against Keytruda in immuno-oncology
- AstraZenecaAZNImfinzi and Tagrisso in lung cancer
- PfizerPFEPrevnar against Capvaxive and Vaxneuvance
Mapped by hand from filings and company reporting, as of October 2026. It shows the relationships that matter most, not every contract: most are never disclosed, and agreements change.