What is apitegromab?
Apitegromab is an investigational, fully human monoclonal antibody developed by Scholar Rock. It is being evaluated in clinical trials as an adjunctive therapy for adults taking GLP-1 receptor agonist medications for weight loss. Apitegromab is not currently licensed for any indication in the UK and is not available for purchase.
Also known as a myostation inhibitor or muscle-preservation therapy, it works by selectively inhibiting myostatin - a protein naturally produced in skeletal muscle cells that limits muscle growth. By blocking myostatin activation, apitegromab is designed to support the preservation of lean muscle mass.
How does apitegromab work?
Apitegromab is a monoclonal antibody that selectively binds to the precursor forms of myostatin - known as pro-myostatin and latent myostatin - before they are activated.
Myostatin is a member of the TGF-beta superfamily of growth factors. It is expressed primarily in skeletal muscle, where it acts as a natural brake on muscle development. When myostatin is activated, it works alongside other signalling proteins to inhibit new muscle growth and maintenance.
By targeting myostatin in its precursor forms, apitegromab is designed to significantly reduce myostatin activity in skeletal muscle while reducing the risk of off-target effects on closely related growth factors.
It is important to note that Apitegromab does not directly contribute to weight loss. It is currently being studied to be used alongside GLP-1treatments such as Wegovy or Mounjaro to help preserve muscle mass during weight loss.
Why does muscle loss matter during GLP-1 treatment?
GLP-1 receptor agonists such as Wegovy (semaglutide) and Mounjaro (tirzepatide) are highly effective for weight loss. However, not all of the weight lost achieved with GLP-1 treatment comes from fat loss. Research has shown that a significant proportion of total weight loss on these medications is lean muscle mass loss - the muscle tissue the body needs for strength, metabolism and physical function.
In the Phase 2 EMBRAZE clinical trial, approximately 30% of the total weight lost in participants taking tirzepatide was attributed to lean muscle mass loss. Preserving muscle during weight loss is considered clinically important for long-term metabolic health, physical function and the sustainability of weight management after treatment. This is particularly relevant for older patients and those who are likely to remain on GLP-1 medications long-term.
What does the clinical evidence show?
The Phase 2 EMBRAZE trial was a randomised, double-blind, placebo-controlled study that enrolled 102 adults with overweight or obesity (BMI ≥27) taking tirzepatide (Mounjaro), conducted by Scholar Rock. Participants received either apitegromab at 10 mg/kg or placebo by intravenous infusion every four weeks for 24 weeks, alongside tirzepatide throughout the study period.
Results published in Nature Medicine in June 2026 showed that participants receiving apitegromab with tirzepatide preserved an additional 1.9 kg (approximately 4.2 pounds), or 54.9% more lean muscle mass compared to those receiving tirzepatide with placebo (p=0.001). The breakdown of weight lost in the apitegromab group was approximately 85% from fat and 15% from lean mass, compared with 70% from fat and 30% from lean mass in the placebo group.
Total weight loss was broadly similar between the two groups. Apitegromab was generally well tolerated, with adverse events comparable between groups and no serious safety events attributed to the treatment.
Is apitegromab available in the UK?
Apitegromab is not currently licensed or available in the UK. It is administered as an intravenous (IV) infusion in a clinical setting and is not a tablet or injectable pen that can be dispensed via an online pharmacy. As of June 2026, apitegromab has no approved indication in the UK, the European Union or the United States for the treatment of obesity or use alongside GLP-1 medications. The EMBRAZE data relate to a Phase 2 proof-of-concept study only, and no regulatory submission for this indication has been made.
The European Medicines Agency (EMA) is separately reviewing a Marketing Authorisation Application for apitegromab for the treatment of spinal muscular atrophy (SMA), an unrelated neuromuscular condition, with a decision anticipated in mid-to-late 2026. The UK's Medicines and Healthcare products Regulatory Agency (MHRA) makes its own independent licensing decisions.
How is apitegromab different to Wegovy or Mounjaro?
Wegovy (semaglutide) and Mounjaro (tirzepatide) are both licensed weight loss treatments available through Pharmica following a clinical consultation. They work by mimicking GLP-1 hormones to reduce appetite, increase feelings of fullness and slow digestion, supporting weight loss through a reduction in calorie intake.
Apitegromab works via a completely different mechanism - it targets myostatin in skeletal muscle and is not intended to drive weight loss directly. Rather, it is designed to be used alongside a GLP-1 medication to improve the quality of weight loss by ensuring more of what is lost is fat rather than muscle. The two approaches are complementary, not interchangeable. Apitegromab is also an IV-administered monoclonal antibody, unlike the subcutaneous self-injection pens used for Wegovy and Mounjaro.
What GLP-1 weight loss treatments does Pharmica offer?
While apitegromab is not available at Pharmica, we offer a range of licensed GLP-1 and weight loss treatments, including Wegovy (semaglutide injection) and Mounjaro (tirzepatide injection), subject to clinical eligibility. A short free online consultation is required to assess suitability. You can explore our full weight loss range using the links below.