CompetitorsNarrow moat

Merck & Co. (MRK) — moat facet

Merck's main rival in cancer is also its royalty partner, and in China its rival is the vaccine that filled the space Merck left.

Merck's competitors are four different kinds of relationship, and none of them is simply a rival selling the same thing cheaper. Bristol Myers Squibb sells the other large PD-1 antibody, Opdivo, and is also Merck's partner on two drugs, paying Merck royalties on one and collecting royalties on another12. Pfizer is the incumbent in pneumococcal vaccines that Merck is attacking from well behind3. Xiamen Innovax is a Chinese vaccine maker with a domestic nine-valent HPV vaccine in the market Merck stopped supplying45. Zoetis is the larger specialist in Animal Health6.

PD-1 antibodies, 2025 sales ($M)31,641Keytruda (Merck)10,049Opdivo (BMS)Merck and Bristol Myers Squibb Forms 10-K FY2025
In cancer Merck sells three times what its nearest named rival does; in vaccines and animal health it trails.

Merck also works with companies that could have been competitors. Lynparza and Koselugo are shared with AstraZeneca, and Lenvima with Eisai7; the TROP2 antibody-drug conjugate sac-TMT comes from Kelun-Biotech8. Alliance revenue from Lynparza and Lenvima was $1,450 million and $1,053 million in 20259.

Competition in patented medicine is mostly decided before a product launches, in trials and patent courts, and after it, in formularies and government price-setting. Keytruda's contest with Opdivo is the one head-to-head rivalry Merck is clearly winning; in vaccines, Merck is the challenger in one market and has left another.

The competitive threat that matters most for Merck is not on this page at all. It is the biosimilar makers who will arrive after December 2028, covered under Keytruda's moat, and Halozyme's patent case against Keytruda Qlex.

The partnerships have their own weight in the accounts. Merck received royalties of $525 million on Bristol Myers Squibb's Reblozyl in 2025, against $17 million in 20211011, and alliance revenue from AstraZeneca's Koselugo was $436 million, including a $150 million upfront payment and $175 million of milestones12. Some of Merck's most useful relationships are with the companies it competes with elsewhere.

Merck holds its own against its named rivals. Pharmaceutical segment sales grew 5% to $14,760 million in the second quarter of 202613; growth that falls below the rate of Merck's patented rivals while Keytruda is still protected would mean share is being lost before the patents even expire.

Moat trajectory: Holding steady

Keytruda leads Opdivo about threefold; vaccines are the weaker front.

The number that tests this moat
Reported
Pharmaceutical segment sales, latest quarter
$14,760M, +5% (Q2 2026)

The human-medicine business against its rivals; growth below theirs before 2028 would mean share is going early.

Source: Merck Q2 2026 results release ↗
Dig deeper
DIG DEEPER 01
Bristol Myers Squibb: Rival in PD-1, Partner in Two Drugs
Keytruda outsells Opdivo about three to one, and Bristol Myers Squibb still pays Merck royalties on another drug.
DIG DEEPER 02
Pfizer: The Incumbent in Pneumococcal Vaccines
Merck's pneumococcal vaccines sell about a quarter of Pfizer's Prevnar, and they are winning adults while losing children.
DIG DEEPER 03
Innovax: The Chinese Vaccine in the Market Merck Left
China approved its own nine-valent HPV vaccine three months after Merck stopped shipping Gardasil there.
DIG DEEPER 04
Zoetis: The Larger Animal Health Specialist
Zoetis sells about half again as much animal medicine as Merck, which grew faster in 2025 partly by buying.
References
  1. ReportedBristol Myers Squibb sells the other large PD-1 antibody, Opdivo, and is also Merck's partner on two drugs, paying Merck royalties on one and collecting royalties on another.
    Bristol Myers Squibb Form 10-K for fiscal 2025 - Opdivo revenue of $10,049 million (+8%) and Opdivo Qvantig $238 million. — FY2025 · publ. February 2026 · source ↗
  2. ReportedBristol Myers Squibb sells the other large PD-1 antibody, Opdivo, and is also Merck's partner on two drugs, paying Merck royalties on one and collecting royalties on another.
    Merck & Co. Form 10-K for fiscal 2025 - patents, exclusivity dates, biosimilar competition and royalties. — FY2025 · publ. 24 February 2026 · source ↗
  3. ReportedPfizer is the incumbent in pneumococcal vaccines that Merck is attacking from well behind.
    Pfizer Form 10-K for fiscal 2025 - Prevnar family revenue of $6,494 million, $4,151 million in the U.S. — FY2025 · publ. February 2026 · source ↗
  4. ReportedXiamen Innovax is a Chinese vaccine maker with a domestic nine-valent HPV vaccine in the market Merck stopped supplying.
    Xinhua, 30 May 2025 - China approves its first domestically developed nine-valent HPV vaccine, Cecolin 9. — May 2025 · publ. 30 May 2025 · source ↗
  5. ReportedXiamen Innovax is a Chinese vaccine maker with a domestic nine-valent HPV vaccine in the market Merck stopped supplying.
    Caixin Global, 17 July 2026 - China's first homegrown nine-valent HPV vaccine, Cecolin 9, and the market Merck left. — July 2026 · publ. 17 July 2026 · source ↗
  6. ReportedZoetis is the larger specialist in Animal Health.
    Zoetis Form 10-K for fiscal 2025 - revenue of $9,467 million, $9,256 million and $8,544 million for 2025-2023 and net income attributable of $2,673 million. — FY2025 · publ. February 2026 · source ↗
  7. ReportedLynparza and Koselugo are shared with AstraZeneca, and Lenvima with Eisai; the TROP2 antibody-drug conjugate sac-TMT comes from Kelun-Biotech.
    Merck & Co. Form 10-K for fiscal 2025 - Item 1 business: products, customers, segments and people. — FY2025 · publ. 24 February 2026 · source ↗
  8. ReportedLynparza and Koselugo are shared with AstraZeneca, and Lenvima with Eisai; the TROP2 antibody-drug conjugate sac-TMT comes from Kelun-Biotech.
    Merck second-quarter 2026 results release, Form 8-K exhibit 99.1 - sales by product and pipeline highlights. — Q2 2026 · publ. 4 August 2026 · source ↗
  9. ReportedAlliance revenue from Lynparza and Lenvima was $1,450 million and $1,053 million in 2025.
    Merck & Co. Form 10-K for fiscal 2025 - Item 7 MD&A and product sales note: sales by product, segment and country. — FY2025 · publ. 24 February 2026 · source ↗
  10. ReportedMerck received royalties of $525 million on Bristol Myers Squibb's Reblozyl in 2025, against $17 million in 2021, and alliance revenue from AstraZeneca's Koselugo was $436 million, including a $150 million upfront payment and $175 million of milestones.
    Merck & Co. Form 10-K for fiscal 2025 - patents, exclusivity dates, biosimilar competition and royalties. — FY2025 · publ. 24 February 2026 · source ↗
  11. ReportedMerck received royalties of $525 million on Bristol Myers Squibb's Reblozyl in 2025, against $17 million in 2021, and alliance revenue from AstraZeneca's Koselugo was $436 million, including a $150 million upfront payment and $175 million of milestones.
    Merck & Co. Form 10-K for fiscal 2023 - product sales for 2021-2023, the Prometheus, Daiichi Sankyo and Imago charges, impairments, receivables concentration and the Zhifei distribution arrangement in China. — FY2023 · publ. February 2024 · source ↗
  12. ReportedMerck received royalties of $525 million on Bristol Myers Squibb's Reblozyl in 2025, against $17 million in 2021, and alliance revenue from AstraZeneca's Koselugo was $436 million, including a $150 million upfront payment and $175 million of milestones.
    Merck & Co. Form 10-K for fiscal 2025 - patents, exclusivity dates, biosimilar competition and royalties. — FY2025 · publ. 24 February 2026 · source ↗
  13. ReportedPharmaceutical segment sales grew 5% to $14,760 million in the second quarter of 2026; growth that falls below the rate of Merck's patented rivals while Keytruda is still protected would mean share is being lost before the patents even expire.
    Merck second-quarter 2026 results release, Form 8-K exhibit 99.1 - sales by product and pipeline highlights. — Q2 2026 · publ. 4 August 2026 · source ↗
Sources
Generated September 25, 2026