Lilly's Bimagrumab Shows Promise in Muscle Preservation During Weight Loss

Eli Lilly's bimagrumab has demonstrated significant potential in preserving muscle mass while promoting fat loss when used in combination with Novo Nordisk's semaglutide (Wegovy). The results, presented at the American Diabetes Association annual meeting, showcase a new frontier in obesity treatment that addresses the common concern of muscle loss during weight reduction.

Phase IIb BELIEVE Study Results

The placebo-controlled Phase IIb BELIEVE study, which enrolled over 500 patients, revealed that the combination of bimagrumab and semaglutide led to a 22.1% weight reduction at 72 weeks. Remarkably, 92.8% of this weight loss was attributed to fat reduction. In comparison, patients receiving semaglutide alone experienced a 15.7% weight loss, with 71.8% coming from fat loss. Bimagrumab monotherapy resulted in a 10.8% weight reduction, entirely from fat loss.

The study's design involved weekly subcutaneous semaglutide injections and intravenous bimagrumab administered at weeks 4, 16, 28, and 40. This regimen not only surpassed the weight loss achieved by semaglutide alone but also demonstrated superior muscle preservation capabilities.

Muscle Preservation Comparisons

Analysts at BMO Capital Markets highlighted that patients taking the bimagrumab-semaglutide combination lost only 2.6% of their lean muscle at 48 weeks, compared to a 7.9% loss in those on semaglutide alone. This translates to a 67% increase in preserved muscle mass, outperforming recent results from competitors Regeneron and Scholar Rock.

Regeneron's Phase II COURAGE study showed that their antibody trevogrumab improved muscle preservation by 51.3% when combined with semaglutide. Adding garetosmab further enhanced preservation to 80.9%. Meanwhile, Scholar Rock's apitegromab, used with Eli Lilly's tirzepatide (Zepbound), demonstrated a 55% improvement in lean muscle mass retention compared to tirzepatide alone.

Safety Considerations and Future Outlook

While the efficacy data for bimagrumab is promising, BMO Capital Markets expressed some concerns regarding its safety profile. Transient increases in alanine aminotransferase (ALT) and more persistent elevations in lipases were noted, suggesting that Lilly will need to address these tolerability questions in future trials.

Bimagrumab, an investigational monoclonal antibody that binds to activin/myostatin type II receptors, came under Lilly's portfolio following their acquisition of Versanis Bio for nearly $2 billion in July 2023. The BELIEVE study, originally sponsored by Versanis, now positions Lilly at the forefront of the emerging muscle preservation space in obesity treatment.

As the pharmaceutical industry continues to innovate in the field of weight management, the focus on maintaining muscle mass during weight loss represents a significant advancement. The combination of effective weight loss agents with muscle-preserving biologics could potentially address a critical need in obesity treatment, offering patients a more holistic approach to improving body composition and overall health.