For women with hormone receptor-positive (HR+) breast cancer or women who are at high risk for breast cancer, endocrine therapy is often recommended by their care team as part of their approach to treatment. Hot flashes and night sweats (also known as vasomotor symptoms) are common side effects of endocrine therapy, which can not only be frustrating, but also affect your quality of life.

There’s promising news on this front. In October 2025, the FDA (Food and Drug Administration) approved elinzanetant, a non-hormonal treatment for moderate to severe hot flashes that works for women with a history of breast cancer, as outlined in a recent study. Here’s what we know.

What was the purpose of the OASIS-4 study?

The OASIS-4 study was a year-long, phase 4 clinical trial of 474 patients across 16 countries, aged 18-70, who either had HR+ breast cancer or were at high risk for it, and were experiencing severe hot flashes due to their endocrine therapy. To qualify, they were required to have at least 35 medium to severe hot flashes within a 7-day period leading up to the trial. 

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For some women on endocrine therapy, their quality of life and sleep quality are so affected by endocrine therapy that they choose to end treatment. With potential help from this new drug, it could be easier for patients to stay on their treatment path and improve their outcomes.

The women enrolled in the double-blind and randomized study were asked to keep a hot flash diary and note changes in the severity of their symptoms, at 4 weeks and then 12 weeks, and then throughout the year until week 52. Women were either on elinzanetant or given a placebo to start and then swapped over to the drug at week 12. 

What were the results of the OASIS-4 study?

By week 12 of the OASIS-4 study, women who were taking the elinzanetant reported a significant reduction in the frequency of their hot flashes at both week 4 and week 12, as compared to women taking the placebo. 

Even more promising news, pharmaceutical company Bayer’s head of research and development confirmed that “OASIS 4 is the first pivotal international study to assess the safety and efficacy of a non-hormonal treatment approach for women with or at high risk of breast cancer who [have] VMS caused by adjuvant endocrine therapy.”

Were there side effects from taking the drug?

Earlier trials (OASIS-1, 2 and 3)  found that elinzanetant was generally well tolerated and could possibly be a safe, nonhormonal alternative to hormone replacement therapy (HRT). The most notable side effects were fatigue and diarrhea, and other participants reported headache and drowsiness.

How exactly does elinzanetant work?

When estrogen levels decrease in your body, this can affect your body temperature, resulting in hot flashes and night sweats. The drop in estrogen triggers the neurons in your brain that affect your temperature to go into overdrive, resulting in hot flashes that can often be severe. Elinzanetant targets these neurons directly, but without using hormones like estrogen or progesterone to do so.

Is elinzanetant available yet?

According to Dr. JoAnn V. Pinkerton, a professor of obstetrics and gynecology at UVA Health, the rollout of this drug could not only help women with HR+ breast cancer or who are high risk and on endocrine therapy, but it could also help women with estrogen-sensitive cancer, blood clots, migraines, endometriosis, and large fibroids. 

It’s been recently approved by the FDA and is expected to be available in pharmacies starting in November 2025. If you’re experiencing hot flashes, ask your care team if this new drug can benefit you.

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