Shares in Myovant Sciences jumped as much as 178% on Tuesday after the company reported that a Phase III study of relugolix in men with advanced prostate cancer met its primary efficacy endpoint and all six key secondary goals.
The company said results of the HERO [https://www.firstwordpharma.com/node/1453887?tsid=33] trial will be used to support a US marketing application for the oral GnRH receptor antagonist in the second quarter of 2020, as well as future regulatory submissions in Europe and Japan.
“An oral GnRH antagonist for advanced prostate cancer has been an aspiration for many years,”
commented Neal Shore, steering committee member for the HERO development programme, adding that “if approved, relugolix would become the first-of-its-kind oral option for men with advanced prostate cancer.”
The HERO trial included 934 patients with androgen-sensitive advanced prostate cancer who require at least one year of continuous androgen deprivation therapy. Subjects were randomised to receive relugolix once daily or a three-month depot injection of leuprolide, which AbbVie markets as Lupron. The primary endpoint to support US approval is the ability of relugolix to achieve and maintain testosterone suppression to castrate levels of below 50 ng/dL through 48 weeks, with Myovant noting that for the study to be successful, the lower bound of the 95% confidence interval of the response rate had to be at least 90%.
The company added that the trial also includes a further 139 men with metastatic prostate cancer, giving a total of 434 patients with metastatic disease, to support the analysis of a secondary goal of castration resistance-free survival, with data expected in the third quarter of next year, as well as 138 Chinese patients to support registration in China.
Results for the primary endpoint responder analysis showed that 96.7% of men receiving relugolix achieved sustained testosterone suppression to castrate levels. Myovant added that five key secondary goals demonstrated superiority to leuprolide, including rapid suppression of testosterone at days four and 15, profound suppression of testosterone at day 15, rapid suppression of prostate-specific antigen at day 15, and suppression of follicle-stimulating hormone after 24 weeks.
In addition, relugolix demonstrated non-inferiority to leuprolide on sustained testosterone suppression through 48 weeks, with a between-group difference of 7.9%, the primary endpoint required for regulatory submissions outside the US. Results also showed no testosterone flare after relugolix was initiated, and mean testosterone levels returned to normal within 90 days after the treatment was stopped.
According to Myovant, the overall incidence of adverse events in the relugolix group was 92.9%, versus 93.5% for those who received leuprolide. The company added that in the experimental drug group, 3.5% of men discontinued the study early due to adverse events compared with 2.6% of those given leuprolide.
Earlier this year, Myovant announced positive top-line data from the Phase III LIBERTY 1 and LIBERTY 2 studies, evaluating relugolix combination therapy in women with heavy menstrual bleeding associated with uterine fibroids, with the company planning to submit an FDA filing in this indication in April. Myovant also expects to release top-line results from the late-stage SPIRIT 2 and SPIRIT 1 trials investigating relugolix combination therapy for endometriosis-associated pain in the first and second quarters of 2020, respectively.
Takeda obtained approval for relugolix earlier this year in Japan, where it is sold by ASKA Pharmaceutical under the brand name Relumina for the treatment of uterine fibroids.