Pfizer: Myovant Sciences and Pfizer Announce FDA Acceptance of Supplemental New Drug Application for MYFEMBREE®

Myovant Sciences (NYSE: MYOV) and Pfizer Inc. (NYSE: PFE) announced today that the U.S. Food and Drug Administration (FDA) accepted for review a supplemental New Drug Application (sNDA) for MYFEMBREE® (relugolix 40 mg, estradiol 1 mg, and norethindrone acetate 0.5 mg). The sNDA proposes updates to MYFEMBREE’s United States Prescribing Information (USPI) based on safety and efficacy data from the Phase 3 LIBERTY randomized withdrawal study (RWS) of MYFEMBREE in premenopausal women with heavy menstrual bleeding associated with uterine fibroids for up to two years. The FDA set a target action date of January 29, 2023 for this sNDA under the Prescription Drug User Fee Act (PDUFA).

“Heavy menstrual bleeding is the most common symptom affecting women with uterine fibroids that can impact their daily life and activities over a long period of time,” said Juan Camilo Arjona Ferreira, M.D., Chief Medical Officer of Myovant Sciences, Inc. “We are pleased to submit these study results to the FDA as they show the value MYFEMBREE can potentially have on treating women’s uterine fibroid symptoms long term.”

Patients who completed the 24-week pivotal LIBERTY 1 and 2 studies were offered the option to receive MYFEMBREE for an additional 28 weeks in an open-label extension study. After completion of the LIBERTY 1 or LIBERTY 2 and the open-label extension studies, women who met the definition of responder (menstrual blood loss < 80 mL and a reduction from pivotal study baseline > 50%) could participate in an additional 52-week randomized withdrawal study (N=229) designed to provide two-year safety and efficacy data on MYFEMBREE and to evaluate the need for maintenance therapy. Women who entered the RWS were re-randomized to either MYFEMBREE or placebo for 52 additional weeks (N = 229), with the primary endpoint at Week 76. The LIBERTY randomized withdrawal study met its primary endpoint with 78.4% of women who continued on MYFEMBREE achieving the sustained responder rate (menstrual blood loss < 80 mL) through Week 76 compared with 15.1% of women who discontinued treatment and initiated placebo at Week 52 (p < 0.0001). All three key secondary endpoints in the LIBERTY randomized withdrawal study were also achieved, including sustained responder rate through Week 104, time to relapse of heavy menstrual bleeding, and amenorrhea rate (all p < 0.0001).

Bone mineral density remained stable in women who received MYFEMBREE in the randomized withdrawal study. Additionally, bone mineral density was maintained through two years in the subset of women continuously treated with MYFEMBREE (N = 31). The incidence of adverse events over one additional year of treatment was consistent with those observed in prior studies, with no new safety signals observed.

“Data from the MYFEMBREE RWS supports our mission to improve care for women living with uterine fibroids,” said James Rusnak, M.D., Ph.D., Senior Vice President, Chief Development Officer, Internal Medicine and Hospital, Global Product Development at Pfizer. “We look forward to the FDA’s review of the application and potential updates to the MYFEMBREE prescribing information based on these data.”

MYFEMBREE was approved in the U.S. in 2021 for the management of heavy menstrual bleeding associated with uterine fibroids in premenopausal women with a treatment duration of up to 24 months.