Bemagromab (Bimagrumab)

Overview

Bemagromab, also known as Bimagrumab (BYM338), is a fully human monoclonal antibody that targets and blocks activin type 2 receptors (ActRIIA and ActRIIB). Originally developed by Novartis and later advanced by Versanis Bio (acquired by Eli Lilly), Bemagromab has been studied for its ability to reduce fat mass while preserving or increasing lean muscle mass. FenaLife supplies Bemagromab for laboratory research use only.

Research Background

Bemagromab was initially investigated for rare muscle-wasting conditions including sarcopenia and inclusion body myositis. Later research pivoted toward obesity pharmacology, where its muscle-sparing and fat-reducing properties became of significant interest. A Phase 2 study published in Nature Medicine demonstrated that combining Bimagrumab with semaglutide produced 22.1% total weight loss at 72 weeks, with 92% of that loss derived from fat mass — outperforming semaglutide alone (15.7%). Phase IIb studies combining Bemagromab with tirzepatide are ongoing as of 2026.

Studied Mechanisms

By blocking ActRIIA and ActRIIB receptors, Bemagromab prevents myostatin, activin A, activin B, and GDF11 from binding and signaling. This inhibition of the activin receptor pathway reduces catabolic signaling in skeletal muscle and promotes net muscle protein accretion. Simultaneously, blockade of these receptors appears to promote adipose tissue remodeling, contributing to selective fat loss. The dual effect on body composition — muscle gain plus fat reduction — distinguishes Bemagromab from standard GLP-1-based weight loss agents.

Molecular Profile

Type: Fully human IgG1 monoclonal antibody. Target: Activin type IIA and IIB receptors (ActRIIA/ActRIIB). Also known as: BYM338, Bimagrumab. Developer: Novartis / Versanis Bio / Eli Lilly. Molecular weight: ~148 kDa (typical IgG1). Purity: ≥98% by HPLC.

Storage and Handling

Store lyophilized Bemagromab at -20°C protected from light. Reconstitute with sterile or bacteriostatic water. Store reconstituted solution at 4°C and use within 4 to 6 weeks. Avoid repeated freeze-thaw cycles.

Research Use Only

For laboratory research purposes only. Not for human or veterinary use. Certificate of Analysis available per batch.