Taldefgrobep Alfa (BMS-986089)
Taldefgrobep alfa (BMS-986089) is an engineered anti-myostatin adnectin-Fc fusion protein — not a conventional antibody — that binds and neutralises myostatin. It was studied in Duchenne muscular dystrophy and later in spinal muscular atrophy and obesity, but a large SMA trial failed its primary endpoint.
01 Overview
Taldefgrobep alfa uses an adnectin (a small engineered binding scaffold derived from fibronectin) fused to an Fc domain to achieve myostatin neutralisation with a smaller binding module than a full antibody. It lowers free myostatin and was initially developed for DMD.
Development moved into spinal muscular atrophy and, more recently, obesity as a lean-mass-sparing agent. A Phase 3 SMA study (RESILIENT) did not meet its primary motor-function endpoint, illustrating again the gap between biomarker changes and functional benefit for myostatin inhibitors.
02 Mechanism
An adnectin-Fc fusion protein that binds free myostatin, reducing its activation of ActRIIB and de-repressing muscle growth.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Trial dosing | 15–50 mg/kg/wk | SubQ | Weight-based subcutaneous dosing studied in DMD; fixed dosing used later. Not marketed. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Reduced free myostatinCirculating free myostatin dropped substantially, confirming the mechanism. | Marked target engagement | Clinical | |
| Functional/motor benefitThe Phase 3 SMA trial did not meet its primary motor-function endpoint. | Not demonstrated | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Injection-site reactionsLocal reactions at subcutaneous injection sites. | Mild | Common | Clinical | |
| ImmunogenicityAnti-drug antibodies may form against the engineered protein. | Mild | Uncommon | Clinical |