Three Months Extension! FDA Delays Pfizer's Myfembree Supplemental New Drug Application

Just a month ago, the US FDA expressed concern about the supplemental new drug application for the drug Myfembree (relugolix) jointly developed by Pfizer and Myovant Sciences. Recently, the FDA decided to extend the review period of the Myfembree application from May 6 to August. 

Pfizer has been advancing the U.S. FDA approval of Myfembree for the treatment of moderate-to-severe pain associated with endometriosis. Regarding the reason for the delay, both companies said that the review period was extended to allow the regulator more time to review other evidence related to the sNDA application.

Juan Camilo Arjona Ferreira, chief medical officer of Myovant Sciences, responded optimistically, saying that the two companies remain confident in the clinical profile of Myfembree and the drug's potential as a treatment for endometriosis-related pain. Myovant and Pfizer will maintain a relationship with the US FDA. Work closely to further support ongoing sNDA review efforts.

Myfembree was approved last year to treat heavy menstrual bleeding associated with uterine fibroids in premenopausal women. Subsequently, the companies hope to expand the indication to include the treatment of pain associated with endometriosis.

Myfembree's sNDA application is supported by Phase III Spirit program data. The program includes the Spirit1 and Spirit2 studies involving more than 1,200 female subjects with endometriosis-related pain. In 2020, the companies reported that Myfembree met criteria for both the co-primary and secondary endpoints in the SPIRIT1 study.

Results of the trial showed that the drug produced clinically meaningful pain reduction in 74.5% of women with dysmenorrhea or dysmenorrhea and 58.5% of women with nonmenstrual pelvic pain, compared with placebo. In the SPIRIT2 study, Myfembree had an efficacy response rate of 75.2% for dysmenorrhea and a 66% response rate for nonmenstrual pelvic pain compared to placebo.

It is estimated that nearly 200 million women worldwide suffer from endometriosis. In the United States, approximately 7.5 million premenopausal women are estimated to have endometriosis. Pfizer and Myovant noted that a diagnosis of endometriosis can take anywhere from four to 11 years. Just last month, the U.S. FDA notified the two companies that it had found a fatal flaw in the Myfembree new drug application, but the specific content of the flaw has not been disclosed by the U.S. FDA as of today.