Phase III OASIS-4 Study Demonstrates Elinzanetant Significantly Reduces Vasomotor Symptoms in Women Undergoing Endocrine Therapy for Breast Cancer

The Phase III OASIS-4 study has shown that the investigational compound elinzanetant significantly reduces the frequency and severity of moderate to severe vasomotor symptoms (VMS) – commonly known as hot flashes. The results were presented at the 2025 ASCO Annual Meeting and simultaneously published in the New England Journal of Medicine.

Over a 52-week period, the study investigated 474 HR+ breast cancer patients undergoing endocrine therapy for treatment or prevention. Already by week 4, elinzanetant showed a statistically significant reduction in VMS frequency compared to placebo (LSMD: −3.5; p<0.001), with even stronger effects by week 12 (LSMD: −3.4; p<0.001).

Sleep disturbances and menopause-related quality of life also improved significantly. The PROMIS SD SF 8b total score improved by −10.6 vs. −4.1 (p<0.001), and the MENQOL total score by −1.3 vs. −0.5 (p<0.001), both favoring elinzanetant.

The safety profile of elinzanetant over the course of the study was generally consistent with previous trials, with fatigue, somnolence, and diarrhea being the most commonly reported side effects.

Currently, no approved treatment options exist for VMS associated with endocrine therapy, even though these symptoms are a major cause of treatment discontinuation. Elinzanetant could fill a critical gap in care and help improve treatment adherence.

Elinzanetant is the first dual neurokinin-targeted therapy in late-stage development, blocking NK-1 and NK-3 receptors. It is hormone-free, taken once daily by mouth, and works by targeting estrogen-sensitive neurons in the brain that regulate body temperature.

“These findings highlight the potential of elinzanetant to improve the quality of life for women undergoing treatment for HR+ breast cancer,” said Dr. Christian Rommel, Head of Research at Bayer.

Breast cancer is the most commonly diagnosed cancer in women worldwide, with 2.3 million new cases annually and about 70% being hormone receptor-positive. Endocrine therapy is standard but often comes with severe side effects, especially during or after menopause.

With OASIS-4, Bayer continues to expand its women’s health portfolio, reaffirming its commitment to developing innovative solutions for underserved medical needs. Marketing authorization submissions for elinzanetant are currently underway in the US, EU, and other regions.