As uterine race with AbbVie heats up, Myovant eyes FDA approval with trial results from prostate cancer
Myovant has long had a secret weapon in its uterine rivalry with AbbVie: Men.
While the small Swiss biotech has jockeyed with the Illinois-based giant for a foothold in the endometriosis and uterine fibroid therapy market, the company has been developing the same lead compound, relugolix, for use in one of the most common cancers for the uterus-less: prostate cancer. Today, Myovant is out with positive topline results from its big Phase III trial on the gonadotropin-releasing hormone (GnRH) antagonist. They say they’ve reached every primary and secondary endpoint with p values less than .0001.
“It works quickly,” CEO Lynn Seely told Endpoints News. “It’s an oral pill and it suppresses hormone production and when you stop it, your hormones come back and you have the potential for improved quality of life.”
Myovant’s stock is up 95% premarket, from $6.06 to $11.80 per share
The trial tested a relugolix arm alongside a standard-of-care, leuprolide, arm in their ability to suppress testosterone in patients with advanced prostate cancer. Testosterone fuels prostate cancer’s growth. The primary endpoint was the percentage of men who reached and maintained medical castration, or less than 50 nanograms of testosterone per deciliter, over 48 weeks.
Relugolix achieved that in 96.7% of patients — safely clearing the FDA’s stated benchmark for approval of 90%, Seely said. For Japanese and European approval, they needed to show non-inferiority and did so, with their leuprolide arm showing only an 88% response rate.
The results set up an FDA application in Q2 of 2020 and European and Japanese applications shortly thereafter, adding to the company’s imminent US application for uterine fibroid therapy.
The underlying mechanism behind the two therapies is essentially inversed. Leuprolide is a GnRH agonist and desensitizes the receptor by hitting it repeatedly. Relugolix blocks it directly.
Myovant’s pitch centers around the speed at which the drug worked, its pill form — rather than leuprolide, which is injected every three months — and the tapering of some side effects, which can be lengthy when it comes to testosterone suppression, including hot flashes, fatigue, loss of muscle mass, sexual dysfunction and depression. Doctors have sometimes given “drug holidays” to manage the clinical benefit against the costs.
“Lowering the testosterone is better for treating prostate cancer,” Seely said. “But it’s not great for the man.”
The adverse event ratio for both drugs was around 93%, but Seely noted a lowered rate of major cardiovascular events in the relugolix group, 2.9% compared to 6.2%. The biotech also said hormone levels returned to normal 90 days after treatment in the relugolix group while sometimes remaining reduced at that point or longer for leuprolide patients — although they did not announce specific numbers.
So why isn’t AbbVie, Myovant’s uterine rival, pursuing a prostate treatment? Seely’s best guess is that it’s because AbbVie’s GnRH antagonist’s half-life is much shorter than Myovant’s. AbbVie requires higher doses in their uterine treatments than Myovant gives — which would mean even higher doses in the prostate therapies, she said.
The question, though, is if leuprolide is still largely effective and the side effects mostly the same, will doctors prescribe a new pill instead?
“I think the biggest concern is that leuprolide … has been in the field for decades,” she said. “Some people question if oncologists and urologists will change their practice.”