Genentech is halting development of an antibody for two rare genetic diseases after the candidate failed to boost muscle growth, raising questions about whether the molecule can preserve muscle in two still-ongoing obesity trials.
Roche’s Bay Area subsidiary disclosed the discontinued programs in separate March 19 letters to the patient communities for spinal muscular atrophy (SMA) and facioscapulohumeral muscular dystrophy (FSHD).
For both conditions, Genentech has “made the difficult decision not to advance emugrobart” into phase 3 trials, the company wrote in the letters.
A Genentech spokesperson confirmed to Fierce Biotech that the anti-myostatin antibody is still being tested in two obesity trials.
For SMA, emugrobart was being tested in a phase 2/3 trial called Manatee; for FSHD, the canned study is a phase 2 trial called Manoeuvre.
After an assessment of the data from both trials, Genentech determined that “emugrobart did not consistently deliver the hoped-for improvements in muscle growth and function” in either one. Genentech plans to share data from both trials at upcoming medical meetings, according to the letters.
Emugrobart is designed to block the activity of myostatin, which itself works to hold back muscle growth. By loosening myostatin’s grip, Genentech hoped that emugrobart could increase muscle mass in SMA and FSHD, two diseases characterized by progressive muscle weakness.
Emugrobart’s failure to improve muscle growth in these trials may be a bad sign for its phase 2 obesity trial, Gyminda. In that study, emugrobart is being paired with Eli Lilly’s tirzepatide in an effort to spare muscle mass from the weight loss triggered by the GLP-1 receptor agonist. While that study’s main endpoint is percent change in total weight, changes in lean mass and muscle volume are also being assessed as a secondary endpoint.
The antibody is also being tested in a smaller phase 1 study in patients with Type 2 Diabetes and obesity or overweight, which is meant to gauge the molecule’s effects on insulin sensitivity and muscle makeup.
Muscle loss is a well-known side effect of GLP-1 medicines, with an intense race underway to develop next-gen obesity drugs that protect muscles. AstraZeneca, Wave Life Sciences and Roche are just some of the players looking to take on the sector’s giants, Eli Lilly and Novo Nordisk by developing drugs that shed pounds without touching muscle.
