(Reuters) -Current weight-loss methods such as lifestyle changes, surgery, and popular therapies like Novo Nordisk's Wegovy and Eli Lilly's ( LLY ) Zepbound result in both fat and muscle loss that can increase the risk of falls and decrease overall strength, which could be especially harmful for older patients. 

The following companies are developing weight-loss treatments that help preserve or grow muscles while patients shed pounds: 

Eli Lilly ( LLY )

The U.S. drugmaker spent nearly $2 billion in 2023 to acquire Versanis Bio's bimagrumab, which prevents the activity of a protein called myostatin to help preserve muscle. 

   Lilly is testing bimagrumab alone and in combination with Novo's Wegovy -- a mid-stage trial begun before the acquisition -- with a main goal of change in total body weight. It is also partnering with China-based Laekna ( LAEKF ) to develop a similar drug.

Regeneron 

Regeneron is testing its drug, trevogrumab, along with Wegovy and another treatment, garetosmab, in a three-part study with healthy and obese participants. Trevogrumab is an antibody that belongs to the same class of treatments as Lilly's bimagrumab. 

The study, expected to be completed next year, has a main goal of change in body weight, but also will measure change in fat mass, waist circumference, body composition, and thigh muscle volume. It is expected to be completed next year. 

Scholar Rock ( SRRK )

The drug developer is testing apitegromab, an experimental therapy that targets the myostatin protein, in combination with Eli Lilly's ( LLY ) weight-loss treatment Zepbound.

Its mid-stage study showed patients preserved more lean mass with the combination treatment than on Zepbound alone.

Roche

Swiss drugmaker Roche began a study last year of its experimental drug, RG6237, as a monotherapy in people with high body weight. The drug, known as an anti-latent myostatin, works by eliminating an inactive form of the protein from the blood.

Roche plans to start a mid-stage trial this year combining the drug and its own GLP-1 weight-loss drug candidate CT-388. 

Biohaven ( BHVN )

Biohaven ( BHVN ) is evaluating its myostatin targeting drug, taldefgrobep alfa, in an early-stage obesity trial.

The drug recently failed to improve motor function in patients with spinal muscular atrophy, but helped cut total body fat mass and showed numerically larger increases in lean mass and bone density compared to placebo. 

It said it plans to rapidly advance a mid-stage study of the drug in patients with obesity. 

Keros Pharma

Keros' drug, KER-065, which targets myostatin and activin A proteins, increased lean mass and reduced fat mass in obese mice when given alone and in combination with semaglutide, the active ingredient in Wegovy and Ozempic.

Keros said it will assess the drug's safety in an early-stage study of male patients with obesity. Data from this study is expected in the first quarter of 2025. 

Northstrive Biosciences

Northstrive Biosciences, a unit of PMGC Holdings ( ELAB ), acquired two myostatin targeting drugs - EL-22 and EL-32 - from South Korean firm MOA Life Plus last year. 

The company, previously known as Elevai Labs, plans to seek an FDA green light to begin human studies this year for both experimental drugs in combination with GLP-1 treatments.

Veru ( VERU )

Veru's ( VERU ) oral drug, enobosarm, targets the androgen hormones that play a role in body development and reproductive health. In a mid-stage study, patients who received the drug along with Wegovy lost 71% less lean, or muscle, mass on average than those who received Wegovy and a placebo over 16 weeks. 

The company will test whether its drug can improve stair climb power in patients aged 60 and older in a larger, late-stage study. 

35 Pharma

Montreal, Canada-based 35Pharma plans to test the safety of its experimental drug, HS235, in an early-stage study. The treatment targets activin and GDF ligands - two proteins that play a key role in regulating skeletal muscle, blood and bone metabolism. Data from this study is expected in the second half of this year. 

Arrowhead Pharmaceuticals ( ARWR )

Arrowhead Pharmaceuticals ( ARWR ) has two RNA-based obesity drugs in its pipeline - ARO-INHBE and ARO-ALK7 - that intervene in a pathway that signals the body to store fat. The company plans to evaluate ARO-INHBE in human studies this year, both as a monotherapy and in combination with Lilly's tirzepatide, the active ingredient in Zepbound and diabetes drug Mounjaro. 

Six Peaks/AstraZeneca ( AZN )

AstraZeneca ( AZN ) in May 2024 agreed to pay up to $80 million to SixPeaks Bio to work with the Swiss biotech start-up on its antibody that targets activin cell receptors to preserve muscle mass in people on weight-loss therapy.  Under the deal, Astra also obtained certain exclusive rights to acquire SixPeaks. 

(Reporting by Bhanvi Satija and Padmanabhan Ananthan in Bengaluru and Ludwig Burger in Frankfurt; Editing by Bill Berkrot and Devika Syamnath)