Bimagrumab

Bimagrumab is a new drug that has the potential to change how the body builds muscle and stores fat. Unlike other treatments for weight loss that focus on reducing appetite, bimagrumab works by targeting receptors that involve muscle growth.

Here, we’ll look into bimagrumab, including current clinical trials and whether it will be available in the UK in the future.

Bimagrumab is a new and experimental drug that is being tested as a weight loss treatment for people with obesity. It is primarily being looked at as a way to improve the quality of weight loss by preventing the loss of, or increasing, muscle mass while also improving overall metabolic health.

It is a ‘human monoclonal antibody’, which means it’s made in a lab but is identical to natural antibodies your body makes, so your body will think it’s the same. It is in development by Eli Lilly. Bimagrumab is taken once every 4 weeks (once a month) by an intravenous (IV) infusion (administered through a vein via an IV drip). The active ingredient in bimagrumab is bimagrumab.

Bimagrumab works by blocking activin receptor type II (ActRII) receptors. These receptors normally bind to proteins such as myostatin, which slow down and prevent muscle growth at a certain point. By stopping this binding, bimagrumab helps to promote muscle growth and prevent muscle loss.

Bimagrumab also increases the activity of brown fat, a type of fat that generates heat by burning calories, which may help in regulating body fat.

How long does bimagrumab last?

Bimagrumab has a half-life of 19 days, though it can stay in your system for around 76 to 95 days, but will slowly stop working during this time. It is given once a month in clinical trials to keep the active ingredient at a high enough level in your body to keep working effectively.

How long does bimagrumab take to work?

Bimagrumab starts to work within 4 weeks of the first dose. At this time, muscle volume had started to increase in comparison to a placebo.

How effective is bimagrumab?

Studies have found that bimagrumab can help to decrease fat mass by about 4.5kg (9.9lbs) and increase muscle size. Lean body mass was also found to increase by around 2kg (4.4lbs), but this did not always mean better strength or physical performance.

In clinical trials, bimagrumab is given in a hospital or clinical setting as a regular IV infusion. In trials, varying doses were given every 4 weeks over a 24 or 48-week period.

What if I miss a dose of bimagrumab?

As bimagrumab is still an investigational drug that is primarily used in clinical trials, what to do if you miss a dose will depend on the trial. If you miss a dose, it is best to contact the health care provider immediately for guidance.

What if I take too much bimagrumab?

Information regarding specific overdose symptoms is limited, as bimagrumab is still in the trial phase. If you think you may have taken too much bimagrumab, you should speak to a doctor straight away.

There is not yet a single set dose of bimagrumab approved for clinical use. Currently, many doses are being studied to find which dose is most effective and in what patient groups. The most common doses in current trials include:

• 70mg
• 210mg
• 700mg
• 10mg/kg

Bimagrumab is not currently available and likely will not be available in the UK for several years, as it is still undergoing clinical trials and the approval process has not yet begun. Results from some of the trials are set to be released in 2026.

Like all new medications, when bimagrumab is approved for use in the UK, it will be highly-regulated and a prescription-only medication.

In clinical trials, most reported side effects were mild and stopped on their own.

Common reported side effects of bimagrumab include:

• diarrhoea
• muscle spasms
• upper respiratory tract infection
• nausea
• increased lipase levels

Uncommon side effects include:

• hypertension
• rash

What to do if you get bimagrumab side effects

Most reported side effects of bimagrumab were mild and went away on their own. Many side effects can be treated easily at home. You can treat:

• diarrhoea by staying hydrated, eating small, bland meals, and avoiding caffeine and alcohol
• muscle spasms by stretching and massaging the muscle, using a warm compress, and staying well hydrated
• nausea by getting plenty of rest, eating bland foods, and getting fresh air

Bimugrumab is not better than Mounjaro or Wegovy as it is not meant to be an alternative. Instead, it’s meant to be used along with them to improve the quality of weight loss. Bimugrumab is being studied as a solution alongside glucagon-like peptide 1 (GLP-1) medications, such as Wegovy or Mounjaro, to reduce muscle loss that can occur alongside weight loss.

Bimagrumab vs Mounjaro

After 48 weeks, people taking bimagrumab had around a 4.5kg (9.9lbs) decrease in fat mass, and increased lean body mass by around 2kg (4.4lbs).

People taking Mounjaro can lose on average 22.5% of their starting weight while taking the highest maintenance dose of 15mg after 72 weeks.

The main difference between bimagrumab and Mounjaro is how they are taken. Bimagrumab is given via IV infusion at a hospital or clinical setting, given by a medical professional, whereas Mounjaro is given as an injection to inject yourself with doses.

Bimagrumab and Mounjaro can have similar side effects, including diarrhoea and nausea.

Bimagrumab vs Wegovy

People taking Wegovy can lose an average of 17% of their starting weight after 68 weeks when taking the 2.4mg maintenance dose.

Wegovy is also given as a once weekly injection that you give to yourself, whereas bimagrumab is administered to the vein via an IV drip.

Side effects of both bimagrumab and Wegovy include nausea and diarrhoea.

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