Genentech antibody emugrobart has failed in two rare diseases, raising questions over whether it can preserve muscle in ongoing obesity trials.
Roche’s Bay Area subsidiary disclosed the discontinued programmes in separate 19 March letters to the patient communities for spinal muscular atrophy (SMA) and facioscapulohumeral muscular dystrophy (FSHD).
For both conditions, Genentech said it had “made the difficult decision not to advance emugrobart” into phase 3 trials.
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 cancelled study was a phase 2 trial called Manoeuvre.
After assessing data from both trials, Genentech said “emugrobart did not consistently deliver the hoped-for improvements in muscle growth and function” in either one.
he company 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 works to hold back muscle growth.
By loosening myostatin’s grip, Genentech hoped emugrobart could increase muscle mass in SMA and FSHD, two diseases characterised 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 the study’s main endpoint is per cent 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 under way to develop next-generation obesity drugs that protect muscle.
AstraZeneca, Wave Life Sciences and Roche are among the companies looking to challenge Eli Lilly and Novo Nordisk by developing drugs that reduce weight without affecting muscle.
