Apitegromab Reduces Lean Mass Loss With Tirzepatide in EMBRAZE Phase 2 Trial

A phase 2 clinical trial published in Nature Medicine on June 8, 2026, found that the drug apitegromab helps preserve lean mass in people losing weight via tirzepatide. Participants in the EMBRAZE study who received a combination of tirzepatide and apitegromab lost less lean mass than those who received tirzepatide and a placebo.

What were the findings of the EMBRAZE study?

According to the study results published June 8, 2026, the combination of tirzepatide and apitegromab was more effective at maintaining lean mass during weight loss than tirzepatide alone. The EMBRAZE trial was designed as a randomized, double-blind, placebo-controlled phase 2 study to evaluate this specific interaction.

In a double-blind trial, neither the participants nor the researchers know who is receiving the active treatment and who is receiving the placebo. This design is used to eliminate bias in the reporting and measurement of outcomes.

Why is lean mass preservation important during weight loss?

When individuals undergo significant weight loss, especially through pharmacological interventions like tirzepatide, the body often loses a combination of fat mass and lean mass. Lean mass includes skeletal muscle, organs, and water.

Maintaining lean mass is a primary goal in metabolic health because muscle tissue is more metabolically active than fat. A significant loss of muscle during weight loss can lead to a decrease in the resting metabolic rate, which may make it more difficult to maintain weight loss over the long term.

Furthermore, the preservation of lean mass is closely tied to physical strength, mobility, and overall functional independence, particularly in older adults or those with metabolic diseases.

How does this research fit into current metabolic treatment?

Tirzepatide is used to induce weight loss, but the accompanying loss of lean mass is a known challenge in obesity medicine. The EMBRAZE study suggests that adding apitegromab to the regimen may mitigate this specific side effect.

This represents a shift toward combination therapies. Rather than focusing solely on the total number on a scale, these researchers focused on the quality of the weight loss—specifically, ensuring that the weight lost is primarily adipose tissue rather than muscle.

What happens next for apitegromab?

Because this was a phase 2 trial, the results provide a proof-of-concept for the efficacy of apitegromab in preserving lean mass. Phase 2 trials are typically used to evaluate the effectiveness of a drug and to determine the safest dose for larger groups of people.

The findings published in Nature Medicine establish a basis for further research. Future studies would likely need to confirm these results in a phase 3 trial, which involves a much larger and more diverse participant pool to ensure the results are consistent and to monitor for any long-term safety concerns.