Nonhormonal Drug Fezolinetant Found Safe for Hot Flashes in Yearlong Study

Tara Haelle

October 19, 2022

The drug fezolinetant, a selective neurokinin-3 receptor antagonist under investigation for treatment of menopausal vasomotor symptoms, showed acceptable long-term safety and tolerability during a 1-year phase 3 randomized controlled trial, according to data presented at the annual meeting of the North American Menopause Society. The study, called SKYLIGHT 4, examined fezolinetant treatment, especially in terms of endometrial health.

The findings mean that fezolinetant "may help bridge a gap in the management of vasomotor symptoms," according to lead author Genevieve Neal-Perry, MD, PhD, chair of the department of obstetrics and gynecology at the University of North Carolina at Chapel Hill.

This study was an important step in fezolinetant's path toward potential approval by the Food and Drug Administration for vasomotor symptoms.

"Moderate and severe vasomotor symptoms can adversely affect quality of life of those affected and result in sleep disruption as well as increased risk for heart disease and other high-risk medical problems," Neal-Perry said. "Although menopausal hormone therapy significantly improves vasomotor symptoms, it may not be desired or it may not be safe for some women," resulting in gaps in care and a need for targeted, nonhormonal therapies for hot flashes. A planned study will also assess the safety of the drug in patients with a diagnosis of hormone-sensitive cancer and disorders that increase the risk for blood clots.

"Fezolinetant has a low side effect profile, it is a nonhormonal option, and it is selective for the neurons that trigger and mediate hot flashes," Neal-Perry said.

Hot flashes are caused by kisspeptin, neurokinin B, and dynorphin neurons located in the hypothalamus. Fezolinetant works by selectively blocking the neurokinin 3 receptor (NK3R), which regulates a person's sense of temperature, Neal-Perry explained. Overactivation of NK3R, resulting from low estrogen levels, plays a role in the hot flashes and cold sweats women experience during menopause.

Drug development for hot flashes "has been hampered by a lack of knowledge regarding the biological cause," Neal-Perry said. "Now that we have a robust understanding of the basic biology of hot flashes, we can develop novel, highly effective, and targeted therapy."

This safety study involved 1,830 women, ages 40-65, who were experiencing menopausal vasomotor symptoms and were randomly assigned to one of three arms for 52 weeks: 45 mg of fezolinetant, 30 mg of fezolinetant, or a placebo once daily.

The primary endpoints included the percentage of women with endometrial hyperplasia, the percentage of women with endometrial cancer, and the frequency and severity of treatment-emergent adverse events (TEAEs). To meet the primary safety endpoint, no more than 1% of participants could have hyperplasia or malignancy, with an upper confidence interval boundary not greater than 4%. Women who met prespecified criteria for their endometrial health to be assessed, underwent endometrial biopsies at baseline and at the end of the study. Three independent pathologists analyzed the tissue without knowledge of which study arm each sample came from. Among the 599 endometrial biopsy samples, 0.5% of the 203 participants taking 45 mg fezolinetant had hyperplasia while none of the women in the other two arms did. Among the 210 women taking 30 mg of fezolinetant, 0.5% had a malignancy; no malignancies occurred in the other two arms.

Overall adverse events were similar across all three arms, including rates of adverse events leading to discontinuation. The most common adverse events were headache and COVID-19. TEAEs related to the drug were 18.1% in the 45-mg arm, 15.4% in the 30-mg arm, and 17.4% in the placebo arm. Serious adverse events were similar across all three arms, and only 0.5% of participants in the 45-mg arm experienced drug-related serious adverse events, compared with none of the women in the 30-mg arm and 0.2% of women in the placebo group.

"The frequency of transaminase elevations was low, and these TEAEs were generally isolated, transient, and resolved on treatment or with discontinuation," the authors reported.

The next steps for fezolinetant will be to assess its effect on mood and quality of life measures related to vasomotor symptoms, Neal-Perry said.

Samantha Dunham, MD, a NAMS-certified menopause practitioner and an associate professor of obstetrics and gynecology at New York University, suggested the drug's safety in the study is encouraging.

"As a medication that treats menopausal symptoms, the study confirmed there are no issues with the endometrium, or lining of the uterus, not that one would expect issues given the mechanism of action," Dunham, also codirector of NYU Langone's Center for Midlife Health and Menopause, said in an interview. Dunham was not involved in the study.

"Earlier versions of medication in this class have caused liver enzyme elevation." The trial of this medication showed that there were only transient elevations in liver enzymes, which resolved upon cessation of the medication. Dunham said. "If the medicine proves to be safe over long periods of time in different populations, this will be a very significant medication for treating menopausal vasomotor symptoms."

The research was funded by Astellas Pharma. Dunham had no disclosures. Neal-Perry is a scientific advisory board member for Astellas and Ferring Pharmaceuticals, and has received research funding from Merck and Overa.

This story originally appeared on MDedge.com, part of the Medscape Professional Network.

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