Myovant Stumbles on FDA Concerns Over Pfizer-Partnered Endometriosis Drug

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Shares of Myovant Sciences have plunged more than 25% after the company announced the U.S. Food and Drug Administration raised concerns over the supplemental New Drug Application for Myfembree (relugolix) as a treatment for the management of moderate to severe pain associated with endometriosis.

Myovant said that the FDA provided notice it had found deficiencies that will preclude any potential discussion of labeling or post-marketing requirements at this time. The FDA did not provide additional details regarding its announcement, Myovant said in a statement. Although the FDA noted in its letter to the company and partner Pfizer that the deficiencies do not reflect a final decision on the sNDA, Myovant investors expressed their opinion by selling off shares of the Roivant Sciences spinout.

Myovant and Pfizer will continue to work with the FDA to determine next steps with sNDA, which remains under review, the companies said. The two companies partnered on Myfembree as a treatment in both oncology and women’s health in late 2020. When the FDA accepted the sNDA last year, the regulatory agency set a PDUFA date of May 6. Although it was not publicly suggested by either company, an issue with the sNDA revealed less than a month before the PDUFA date could herald a Complete Response Letter from the FDA.

The sNDA was supported by data from the Phase III SPIRIT program, which included the SPIRIT 1 and SPIRIT 2 studies that involved more than 1,200 women with pain associated with endometriosis. In the SPIRIT 2 study, data showed that Myfembree demonstrated a 75.2% response rate for dysmenorrhea, which is menstrual pain and a 66% response rate for non-menstrual pelvic pain in comparison to placebo. The trial data showed that women who received Myfembree had a 75% reduction in pain on average. The pain reduction was dropped from severe to mild on the Numerical Rating Scale for dysmenorrhea in endometriosis patients.

In the SPIRIT 1 study, Myfembree hit the mark in its co-primary endpoints, as well as its secondary endpoints, the company reported in June 2020. In this study, Myfembree generated clinically-meaningful pain reductions for 74.5% of women with dysmenorrhea and 58.5% of women with non-menstrual pelvic pain compared to placebo.

Last year, the two companies announced their findings from a long-term Phase III extension study that continued to show a reduction in menstrual pain and non-menstrual pelvic pain in women with endometriosis who were treated with Myfembree, a combination of relugolix with estradiol and norethindrone acetate. Myfembree has been approved by the FDA as a once-daily oral treatment for heavy menstrual bleeding associated with uterine fibroids in premenopausal women.

Endometriosis occurs when tissue that is similar to that normally found in the uterus grows outside of the organ. This can lead to long-term pelvic pain (during or between menstrual cycles), pain during intercourse and other painful symptoms. The pain from endometriosis is typically managed with nonsteroidal anti-inflammatory drugs (NSAIDs), opioids and hormonal therapies.