Myovant is locked in a battle with AbbVie for women’s health applications of its GnRH inhibitor relugolix, but a planned regulatory submission in prostate cancer sidesteps its main rival.
The phase 3 HERO trial of Takeda-partnered relugolix has revealed a 97% response rate in men with advanced prostate cancer, setting up filings in the US in the second quarter of 2020 and in Europe and Japan a little later, says the biotech.
A response in the trial was defined as achieving and maintaining testosterone suppression at castration levels over the course of the 48-week study, and relugolix cleared the 90% rate required by the FDA to support regulatory approval.
Myovant is in a head-to-head battle with AbbVie and its rival GnRH inhibitor Orilissa (elagolix) in endometriosis-related pain and uterine fibroids, but has a clear run at the prostate cancer market as AbbVie has halted development in that indication, according to Adis Insight.
The data also showed that relugolix was also more effective than AbbVie’s older and widely-used injectable prostate cancer therapy Lupron (leuprolide acetate) in suppressing testosterone levels and prostate-specific antigen (PSA), a biomarker for prostate cancer.
“If approved, relugolix would become the first-of-its-kind oral option for men with advanced prostate cancer,” said Neal Shore of Carolina Urologic Research Centre, who is on the HERO steering committee.
Secondary endpoints from the study showed that relugolix was better than Lupron at suppressing testosterone quickly (four to 15 days after dosing started) suppressing PSA at day 15, and reducing levels of follicle-stimulating hormone (FSH), which can drive tumour growth in prostate cancer.
Myovant’s chief executive Lynn Seely said the results bring the company “closer to our goal of bringing a precision oral medicine to the broad spectrum of men with advanced prostate cancer”.
It’s also an important development as Myovant has delayed its filing for approval of relugolix in uterine fibroids to allow it to include 12-month safety data, placing it at risk of falling further behind AbbVie in the women’s health category.
Orilissa has been approved in endometriosis and filed for uterine fibroids, while Myovant is still waiting for phase 3 data from its SPIRIT phase 3 programme for relugolix in endometriosis, with results due next year.
The positive trial result is also good news for Japanese drugmaker Sumitomo Dainippon, which agreed a $3bn upfront deal to acquire a 45% stake in Myovant – and control of four other companies in the Roivant Sciences group headed by entrepreneur Vivek Ramaswamy – in September.