What Is Efinopegdutide?

1. What Is Efinopegdutide?

Efinopegdutide is an investigational molecule developed by Merck under the code name MK-6024. It is a once-weekly subcutaneous peptide designed to activate two receptors: the GLP-1 receptor and the glucagon receptor.

It belongs to the GLP-1/glucagon dual-agonist family, alongside pemvidutide and survodutide. What sets it apart is its clear emphasis on the liver.

2. A Long Naming History

Efinopegdutide has changed hands more than once, which is why several code names appear in older literature. Originally developed by Hanmi Pharmaceutical as HM12525A, it was licensed to Janssen (Johnson & Johnson) as JNJ-64565111, returned, and then licensed to Merck as MK-6024. They are all the same molecule.

• HM12525A — Hanmi’s original code.
• JNJ-64565111 — Janssen’s designation during its earlier development.
• MK-6024 — Merck’s current designation; the molecule’s name is efinopegdutide.

3. Why a GLP-1/Glucagon Dual Agonist for the Liver?

The molecule is derived from oxyntomodulin, a natural peptide with both GLP-1 and glucagon activity. The two arms are designed to complement each other:

• GLP-1 arm: appetite suppression and glucose-dependent insulin effects.
• Glucagon arm: increased energy expenditure and hepatic (liver) fat oxidation, directly reducing liver fat.

That direct liver mechanism is the rationale for targeting MASH, a disease in which fat, inflammation, and fibrosis build up in the liver.

4. Is Efinopegdutide FDA-Approved?

No. Efinopegdutide is not FDA-approved as of June 2026. It is investigational, has no marketed product, and is available only through Merck clinical trials. It holds FDA Fast Track designation for NASH, which is intended to facilitate development and review; it is not an approval.

5. What Did the Phase 2a Liver-Fat Trial Show?

The Phase 2a trial (NCT04944992) compared efinopegdutide directly against semaglutide in adults with fatty liver disease (liver fat of at least 10%). Over 24 weeks, Merck reported that efinopegdutide produced a greater relative reduction in liver fat content, measured by MRI, than semaglutide. The result was published in the Journal of Hepatology in 2023.

This was a liver-fat imaging endpoint in a defined population, not a general statement that one drug is better than the other. See What Is Semaglutide? for the comparator.

6. The Phase 2b MASH Trial

Merck advanced efinopegdutide into a Phase 2b trial (NCT05877547) in adults with precirrhotic MASH, comparing it against both semaglutide and placebo, with a primary endpoint of MASH resolution without worsening of fibrosis at 52 weeks. The trial completed in late 2025; detailed topline results were not yet published in a peer-reviewed or press source at the time of writing, so they should be treated as pending.

7. Efinopegdutide vs Pemvidutide vs Survodutide

These three GLP-1/glucagon agonists are often grouped together. The main differences are the balance between the two receptor arms and how far each program has advanced.

• Efinopegdutide (Merck): liver-fat focus; notable for a published head-to-head versus semaglutide on liver fat.
• Pemvidutide (Altimmune): described as balanced roughly 1:1; emphasis on lean-mass preservation; positive Phase 2b MASH data.
• Survodutide (Boehringer Ingelheim/Zealand): described as more GLP-1-weighted; the most advanced of the three, in Phase 3 for both MASH and obesity.

8. Where Efinopegdutide Stands

• Efinopegdutide is the molecule; MK-6024 is its current code name.
• Investigational describes its regulatory status.
• GLP-1/glucagon dual receptor agonist is the accurate mechanism description.
• MASH (liver disease) is the lead focus, not obesity alone.

9. What Is Efinopegdutide FAQ

• What is efinopegdutide in simple terms?

  Efinopegdutide is Merck's investigational once-weekly injection that activates two receptors, GLP-1 and glucagon. The glucagon arm acts on the liver, which is why its main focus is the liver disease MASH rather than weight loss alone.

• Is efinopegdutide FDA-approved?

  No. Efinopegdutide is investigational and not approved by the FDA or any regulator as of June 2026. It is available only to participants in Merck clinical trials. It does hold FDA Fast Track designation for NASH, which speeds review but is not an approval.

• Why is efinopegdutide focused on the liver?

  Its glucagon receptor arm increases energy expenditure and hepatic fat oxidation, directly reducing liver fat. Combined with the GLP-1 arm's appetite and metabolic effects, this makes it a candidate for MASH, a fatty-liver disease with inflammation and fibrosis.

• How did efinopegdutide compare with semaglutide?

  In a Phase 2a trial in people with fatty liver disease, Merck reported that efinopegdutide produced a greater relative reduction in liver fat at 24 weeks than semaglutide. This was a liver-fat imaging endpoint in a defined trial population, not a general comparison of the two drugs.

• How is it different from pemvidutide and survodutide?

  All three are GLP-1/glucagon dual agonists studied in liver disease. They differ mainly in the balance between the GLP-1 and glucagon arms and in how far along each program is. Efinopegdutide is notable for a published head-to-head versus semaglutide on liver fat.

10. Sources