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Favezelimab · MK-4280

Monoclonal antibody · Antagonist of LAG3 · developed by Merck &

Phase 1/2 Most advanced trial (none active)

MRK Developer

1 Registered trials

What is Favezelimab?

Favezelimab is a humanized IgG4 monoclonal antibody that binds LAG3 on tumor-infiltrating lymphocytes, blocking its interaction with MHC class II molecules on tumor cells. This activates antigen-specific T-lymphocytes and enhances cytotoxic T-cell-mediated tumor cell lysis. It is studied in renal cell carcinoma.

Summary written with AI from the sources listed at the end of this page.

At a glance

Also known as: MK-4280
Drug type: Monoclonal antibody
Targets: LAG3
Mechanism: Antagonist of LAG3
Pathways: immune checkpoint inhibition, T-cell activation
Therapy area: Oncology
Developer: Merck & Co. (MRK)
FDA status: Investigational, not approved in the US. Most advanced trial: Phase 1/2
UNII: H1396W7D1H

🧪 Clinical trials

Trial	Phase	Condition	Status	Sponsor
NCT04626479	Phase 1/2	Carcinoma, Renal Cell	Completed	MRK

Trials of the companies BioRadar tracks, from ClinicalTrials.gov, most advanced phase first.

Conditions studied

Carcinoma, Renal Cell

Other drugs acting on LAG3

Relatlimab FDA approved Fianlimab Phase 1/2 Tobemstomig Phase 1/2

More from Merck &

BCG Live FDA approved Belzutifan FDA approved Berahyaluronidase Alfa FDA approved Berahyaluronidase Alfa and Pembrolizumab FDA approved Enlicitide FDA approved Ensifentrine FDA approved Letermovir FDA approved Pembrolizumab FDA approved Probenecid FDA approved Alimatravir Phase 2 Bomedemstat Phase 2/3 Calderasib Phase 3

Sources

Updated Oct 3, 2026. Something wrong or missing? Report it on the MRK page.

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Data: FDA (Drugs@FDA, Purple Book, DailyMed), NIH (NCI Thesaurus, GSRS, RxNorm), ClinicalTrials.gov • Informational purposes only, not medical or investment advice. • All drugs A–Z