Last reviewed 2026-04-23 · How we verify

MK-3415A

MK-3415A is a monoclonal antibody that targets and inhibits OX40, a costimulatory immune checkpoint receptor, to enhance T-cell activation and anti-tumor immunity.

MK-3415A is a monoclonal antibody that targets and inhibits OX40, a costimulatory immune checkpoint receptor, to enhance T-cell activation and anti-tumor immunity. Used for Advanced or metastatic solid tumors (in combination with checkpoint inhibitors).

At a glance

Mechanism of action

OX40 is an inducible T-cell costimulatory molecule that plays a key role in T-cell proliferation and survival. By blocking OX40 signaling, MK-3415A enhances T-cell-mediated immune responses against cancer cells. This approach aims to overcome immune suppression in the tumor microenvironment and improve anti-tumor efficacy, often in combination with other immunotherapies.

Approved indications

• Advanced or metastatic solid tumors (in combination with checkpoint inhibitors)

Common side effects

• Fatigue
• Nausea
• Diarrhea
• Immune-related adverse events

Key clinical trials

• A Study of MK-3415, MK-6072, and MK-3415A in Participants Receiving Antibiotic Therapy for Clostridium Difficile Infection (MK-3415A-001) (PHASE3)
• A Study of MK-6072 and MK-3415A in Participants Receiving Antibiotic Therapy for Clostridium Difficile Infection (MK-3415A-002) (PHASE3)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• MK-3415A CI brief — competitive landscape report
• MK-3415A updates RSS · CI watch RSS
• Merck Sharp & Dohme LLC portfolio CI