Mass General Hospital Experts Call a Hot Flash Drug Trial Promising but Say It Is Too Early to Judge

BOSTON — A single injection of an experimental drug sharply reduced hot flashes in a small clinical trial, but it is too soon to say it works better or is safer than existing treatments. That is the assessment of the Center for Women’s Mental Health at Massachusetts General Hospital, published Nov. 3.^[1] This story is part of our Mass General Hospital news coverage.

Related: Mass General Hospital’s ER Opioid Treatment Model Is Expanding to Salem and Western Massachusetts.

What the drug is

The drug, ABCL635, is made by AbCellera Biologics, which is also running the trial.^[2] It is not a hormone. It is an antibody that blocks the neurokinin 3 receptor, part of the brain system that regulates body temperature.^[1]

An approved pill, fezolinetant, sold as Veozah, targets the same receptor and is taken daily. ABCL635 is given as an injection under the skin and is being developed as a long-acting treatment.^[1]

What the trial found

AbCellera announced the results on Aug. 10. The trial enrolled 92 postmenopausal women who averaged about 10 moderate-to-severe hot flashes a day. They were randomly assigned to one 600-milligram dose of the drug or a placebo, and neither the women nor the investigators knew who got which.^[1][2]

After four weeks, women who got the drug had 8.8 fewer hot flashes a day on average, compared with 3.5 fewer for placebo. Severity fell 58% with the drug and 12% with placebo. Improvement showed up in the first week, and participants also reported better sleep.^[1]

No serious side effects were reported, and no one stopped treatment because of side effects. Headache, fatigue and injection-site reactions were more common with the drug than with placebo.^[1]

Why the Mass General center is cautious

The center pointed to two limits: only 46 women received the drug, and they were followed for four weeks. That is not enough to show how long the benefit lasts, how often the shot would be needed, or whether rare or long-term side effects appear with repeated doses.^[1]

The findings “should not yet be interpreted as evidence” that the drug beats current treatments, the center wrote. The numbers also come from the company’s own announcement of top-line results.

The trial is listed as active but no longer recruiting, with completion estimated for February 2027.^[2]

Why it matters

About 80% of women have hot flashes or night sweats around menopause, and for some the symptoms last for years. Hormone therapy remains one of the most effective treatments, but some women cannot take it or prefer not to, the center said.^[1] That leaves demand for non-hormonal options.

ABCL635 is still experimental, and nothing in the trial changes current care. Anyone weighing treatment for menopause symptoms should talk with their own clinician.

More coverage

Also in Mass General Hospital news today: the hospital’s emergency room opioid treatment model is expanding. Earlier, we reported that MGH and the Brigham sued Eli Lilly over drug discount data. See more health news and Boston and Massachusetts news.

Sources

1. MGH Center for Women’s Mental Health: ABCL635 Shows Promise for Menopausal Hot Flashes in Phase 2 Trial
2. ClinicalTrials.gov: Study Evaluating ABCL635 for Vasomotor Symptoms of Menopause (NCT07118891)

About the reporter: Nora Whitfield is an AI reporter covering Boston and Massachusetts news for The Boston Report. This article was produced with AI under our editorial policy. Read our AI and media disclosure.