Pfizer and Myovant Announce Positive Phase III Results for Relugolix Combination Therapy in Uterine Fibroids

Compiled by River

On March 25, Pfizer and Myovant announced positive results from the LIBERTY Phase III clinical trial evaluating relugolix combination therapy for uterine fibroids in women. The combination therapy consists of relugolix 40 mg, estradiol 1.0 mg, and norethindrone acetate 0.5 mg. The trial was designed to assess the continuous administration of the relugolix combination regimen for up to two years.

This specialized study, the LIBERTY randomized withdrawal trial, was a Phase 3 clinical trial that enrolled eligible women who had completed the LIBERTY long-term extension study. Eligibility criteria included meeting the responder definition within one year, defined as a reduction in menstrual blood loss of 80 mL relative to baseline and a ≥50% decrease from baseline during the last 35 days of treatment, as measured by the alkaline hematin method. At Week 52, these women were randomized to once-daily relugolix combination therapy or placebo for a one-year double-blind treatment period. Additionally, women in the placebo group who experienced recurrence or severe menstrual bleeding during the trial could receive open-label relugolix combination therapy.

Given that many women with uterine fibroids spend years struggling to manage their symptoms, there is a significant need for non-invasive, long-term treatment options. Data from the LIBERTY randomized withdrawal study demonstrate the potential benefit of continuous treatment for uterine fibroids, showing that women receiving relugolix combination therapy experienced significant symptom relief for up to two years.

Relugolix is a once-daily oral gonadotropin-releasing hormone (GnRH) receptor antagonist that reduces ovarian estradiol production by blocking GnRH receptors in the pituitary gland; estradiol is a hormone known to stimulate the growth of uterine fibroids and endometriosis. Additionally, the drug inhibits testicular testosterone production, a hormone that can stimulate the growth of prostate cancer. In December 2020, the drug was officially approved by the FDA, becoming the first oral hormonal therapy for the treatment of advanced prostate cancer in adults.

The two companies signed a collaboration agreement in late December 2020 to cooperate in the United States and Canada, with Pfizer obtaining an exclusive option to develop the drug in the oncology field in markets outside these two regions (excluding Asian countries). They are developing and commercializing the drug under the brand name Orgovyx for advanced prostate cancer. If the combination therapy is approved, it will be used in conjunction with estradiol 1.0 mg and norethindrone acetate 0.5 mg for women’s health indications in the United States and Canada. They will share equally in the profits and certain expenses related to Orgovyx and relugolix.

As part of the transaction, Pfizer will pay Myovant up to $4.2 billion, including a $650 million upfront payment, $200 million in potential regulatory milestone payments, and tiered sales milestones totaling $2.5 billion upon reaching specific net sales thresholds for prostate cancer treatments and combined women’s health therapies. If Pfizer exercises its option to expand into oncology indications outside the United States and Canada, it will make an additional $50 million payment to Myovant and pay double-digit royalties on sales.

Reference Source: Myovant and Pfizer’s Relugolix Combo Effective in Treating Uterine Fibroids