Myovant and Pfizer’s endometriosis expansion bid for Myfembree has hit a pothole late in the FDA’s review process.
In a letter to the companies, the United States regulator has identified deficiencies that “preclude discussion of labeling and/or post-marketing requirements and commitments at this time.” The partners said there was no further explanation from the FDA and that the application remains under review.
The companies will work with regulators to determine the next steps in the application, they said.
In response, Myovant's shares were down 16% by mid-morning on Tuesday.
The FDA signed off on the new drug submission in September of last year and assigned a decision date of May 6. Last May, the FDA approved the drug to treat heavy menstrual bleeding linked to uterine fibroids in premenopausal women.
Endometriosis is an estrogen-dependent, inflammatory condition in which tissue, similar to the uterine lining, is found outside the uterine cavity, in the pelvis or lower abdomen on ovaries, the bladder or colon. The disorder can cause chronic pain and heavy bleeding, especially during ovulation or during or after intercourse and can lead to infertility.
Myfembree was shown to be effective in reducing the pain of endometriosis in studies that included more than 1,200 women.
Pfizer spent $650 million up front to get a piece of the drug in December 2020. The companies struck the deal shortly after Myovant scored an FDA green light for Orgovyx for the treatment of patients with advanced prostate cancer.
Myovant is eligible for a $100 million milestone payment from Pfizer if the drug wins an FDA approval in endometriosis.
In its use to treat those with uterine fibroids, Myfembree is limited to a 24-week regimen due to the risk of bone loss.
The drug’s label also includes a warning—as is the case for other estrogen and progestin combinations—of an increased risk of thromboembolic disorders and vascular events.