WASHINGTON, D.C.: As the global weight-loss market explodes, drugmakers are now racing to solve a less visible problem: protecting muscle mass.

Existing treatments like Novo Nordisk's Wegovy and Eli Lilly's Zepbound have proven effective at helping people shed pounds, but not all the weight lost is fat. Muscle loss, especially in older patients, can raise the risk of falls and lower physical strength, spurring a wave of new drug development.

Here's a look at the key players and their experimental therapies designed to combat fat while preserving or even boosting lean muscle:

Eli Lilly
Lilly spent nearly $2 billion in 2023 to acquire Versanis Bio's bimagrumab, a treatment that inhibits the myostatin protein to help protect muscle. The company is testing the drug alone and with Novo's Wegovy in a mid-stage trial. It also partnered with China's Laekna to develop a similar drug.

Regeneron
Regeneron is evaluating trevogrumab—a similar myostatin-targeting antibody—in combination with Wegovy and another drug, garetosmab. The three-part study includes both healthy and obese participants and tracks changes in weight, fat, waist size, body composition, and thigh muscle volume. It is expected to wrap up next year.

Scholar Rock
Scholar Rock's apitegromab, also a myostatin inhibitor, is being tested with Lilly's Zepbound. A mid-stage study showed the combination helped preserve more lean mass than Zepbound alone.

Roche
Roche is studying RG6237, an anti-latent myostatin, in overweight individuals. Starting this year, it plans to combine this drug with its own GLP-1 candidate, CT-388, in a mid-stage trial.

Biohaven
Biohaven's taldefgrobep alfa recently fell short in treating spinal muscular atrophy, but in an early-stage obesity trial, it reduced fat mass and increased lean mass and bone density. A mid-stage obesity trial is planned.

Keros Pharma
Keros' KER-065 targets both myostatin and activin A. In preclinical trials, it boosted lean mass and cut fat in obese mice. A first-stage trial in obese men is underway, with results expected in Q1 2025.

Northstrive Biosciences
Northstrive, formerly Elevai Labs, bought two myostatin-targeting drugs (EL-22 and EL-32) from South Korea's MOA Life Plus. It plans to seek FDA clearance for human trials this year, paired with GLP-1 therapies.

Veru
Veru's oral drug enobosarm targets androgen hormones. In a mid-stage study, patients who took it with Wegovy lost 71 percent less muscle than those on Wegovy plus a placebo. A late-stage study will now assess stair climb power in patients 60 and older.

35 Pharma
35Pharma will soon begin early-stage testing of HS235, which targets activin and GDF ligands involved in muscle, bone, and blood metabolism. Data is expected in the second half of 2025.

Arrowhead Pharmaceuticals
Arrowhead is developing two RNA-based obesity drugs—ARO-INHBE and ARO-ALK7—that interrupt fat-storage signals. Human trials of ARO-INHBE, both solo and alongside Lilly's tripeptide, are planned for this year.

Six Peaks / AstraZeneca
In May 2024, AstraZeneca agreed to pay up to $80 million to Swiss biotech SixPeaks Bio for access to an antibody targeting activin cell receptors. The goal was to protect the muscle during weight loss and potentially acquire SixPeaks down the line.