BARCELONA — Elinzanetant reduced the severity and frequency of hot flushes and night sweats in women taking endocrine therapy for breast cancer, it was reported here at the 15th European Breast Cancer Conference.

Greater improvements were seen across endocrine therapy subgroups in the phase 3 OASIS-4 trial, in which 265 women had received tamoxifen, 209 an aromatase inhibitor, 136 ovarian function suppression, and 338 no ovarian function suppression.

“You see an improvement in symptoms immediately, and it's sustained throughout the treatment,” study investigator Fátima Cardozo, MD, of Centre Antoine Lacassagne in Nice, France, and president of the Advanced Breast Cancer (ABC) Global Alliance, told Medscape News Europe.

Vasomotor symptoms are a well-known side effect of endocrine therapy for breast cancer and can affect multiple aspects of a person’s life, she explained. “They are associated with sleep disturbances, affect quality of life, and they affect their ability to perform their usual responsibilities,” all of which can affect patient adherence. 

“It's quite obvious that if you help people stay with the treatment for breast cancer, it will have a positive impact,” Cardozo said. 

The main results of OASIS-4 were published in The New England Journal of Medicine last year to coincide with their presentation at the American Society of Clinical Oncology (ASCO) 2025 annual meeting. These showed a clear and significant (P < .001) reduction in vasomotor symptoms with elinzanetant vs placebo of -6.5 and -3.5 episodes, respectively, at 4 weeks, and -7.8 and -4.2 episodes, respectively, at 12 weeks. 

“A question that always came up was, does it work the same if we are giving tamoxifen or if we are giving an AI that reduces the estrogen level even further?” Cardozo said, explaining the rationale for the subanalysis by type of endocrine therapy. Also, “Does it work the same in postmenopausal women and in the younger women where we block the ovaries with ovarian function suppression?”

Looking at all 474 women taking adjuvant endocrine therapy for hormone receptor-positive breast cancer who had been included in the trial, 265 had received endocrine treatment with tamoxifen, 209 an aromatase inhibitor , 136 a GnRH analog, and 338 no GnRH analog. 

Cardozo pointed out in her presentation that all the women had moderate-to-severe vasomotor symptoms at baseline, defined as experiencing 35 or more vasomotor symptoms per week.

The daily reduction in the frequency of vasomotor symptoms at weeks 1, 4, and 12 in women treated with tamoxifen in the elinzanetant group were, respectively, -4.2, -6.8, and -8.1 from a baseline of 11.6 symptoms. Corresponding values were -1.6, -2.5, and -3.0 from a baseline of 10.8 in the placebo group. 

Similar reductions were seen for the other endocrine therapies and for the reduction in severity of vasomotor symptoms. 

Consistent with the main trial findings, elinzanetant reduced vasomotor symptom frequency and severity more than placebo, with rapid onset and sustained effects over 52 weeks, regardless of endocrine therapy type, Cardozo concluded.

Commenting on the trial, Antonio Di Meglio, MD, Gustave Roussy Cancer Center, Villejuif, France, said that many nonpharmacologic and pharmacologic options have been tested with various levels of efficacy and quality of evidence. OASIS-4 and the subgroup analysis by type of endocrine therapy supported elinzanetant as a promising new treatment for people with breast cancer with bothersome vasomotor symptoms while receiving endocrine therapy, he said.

“OASIS-4 specifically adds evidence in the space of women suffering from hot [flushes] while taking endocrine therapy for hormone receptor positive breast cancer. And additional data will come from the HIGHLIGHT-1 trial that is looking at fezolinetant in the same population,” Di Meglio said. 

What remains to be seen is whether reducing vasomotor symptoms could ultimately have an effect on breast cancer outcomes. Such data would be informative if limited, he said. Also, it may be interesting to perform additional subgroup analyses according to age, menopause, BMI, or smoking history, “to better define who derives the greatest benefit,” he suggested. 

Di Meglio also noted that even if inexpensive or reimbursed, adding the drug would still be an additional cost of treatment, and whether people would want to take one drug long term to offset the side effects of another would need to be answered. Also, the safety and efficacy of combining elinzanetant with CDK 4/6 inhibitors would need to be assessed.

Elinzanetant (Lynkuet) was approved for use for the treatment of severe vasomotor symptoms associated with menopause by the MHRA in July 2025, the FDA in October 2025, and the European Commission in November 2025. Only the latter specifically considered vasomotor symptoms associated with adjuvant endocrine treatment for breast cancer. 

The study was funded by Bayer. Cardoso reported paid consultancy for Amgen, Astellas/Medivation, AstraZeneca, Bayer, Celgene, Daiichi Sankyo, Eisai, GE Oncology, Genentech, Gilead, GlaxoSmithKline, IQVIA, MacroGenics, Medscape, Merck Sharp, Merus, Mylan, Mundipharma, Novartis, Pfizer, Pierre Fabre, priME Oncology, Roche, Sanofi, Samsung Bioepis, Seagen, Teva, and touchIME. Di Meglio was not involved in the study and reported no relevant financial relationships. 

Sara Freeman is a medical journalist based in London.