A single injection reduced moderate-to-severe hot flashes by 83 percent over four weeks in a mid-stage trial, compared with 33 percent for placebo, in the first efficacy readout for an antibody approach to a symptom that affects most women going through menopause.
AbCellera reported Phase 2 results for ABCL635, an investigational neurokinin-3 receptor antagonist antibody, in an announcement this week. In absolute terms, treated participants averaged 8.8 fewer moderate-to-severe episodes per day at week four, compared with 3.5 fewer on placebo. In terms of severity, the drug produced a 58 percent reduction compared to 12 percent for placebo. The company also reported statistically significant improvements in sleep and in patients' own assessment of their overall condition.
The trial was small and short. It enrolled 92 postmenopausal women averaging roughly 10 moderate or severe hot flashes per day, randomized one-to-one to a single 600-milligram subcutaneous dose or placebo, with 46 participants per group, and results measured at four weeks.
That is the essential context for anyone reading such a large percentage. This is a Phase 2 result in fewer than 100 women followed for a month, not evidence that the drug works over years.
Why the Delivery Method Is the Actual Innovation
Blocking the NK3 receptor is not new. Fezolinetant, sold as Veozah, is an FDA-approved nonhormonal pill in the same receptor class, and MedicalDaily previously reported that the FDA issued its strongest warning on that drug over serious liver injury, with routine blood monitoring required during the first months of use.
The receptor sits on KNDy neurons in the hypothalamus, the region that regulates body temperature. When estrogen falls, signaling through this pathway becomes unstable, which is the mechanistic account of why hot flashes happen.
What differs here is the molecule. Small-molecule drugs are absorbed and processed through the liver, which is where the monitoring burden with existing options originates. An antibody is a large protein cleared differently, and it is long-acting by design. The company is developing ABCL635 as a long-acting subcutaneous treatment, which raises the prospect of infrequent dosing rather than daily pills. This is the first efficacy readout for that approach, following the compound's entry into clinical testing in 2025.
AbCellera described the tolerability profile as favorable. Detailed safety data have not been published in a peer-reviewed journal, and four weeks is not long enough to characterize the safety of a long-acting biologic.
The Women This Would Matter Most For
Vasomotor symptoms are among the most common and disruptive symptoms of menopause. The company estimates that roughly 12 million women in the United States experience moderate-to-severe symptoms, of whom more than six million seek treatment.
Hormone therapy remains effective and is appropriate for many women, but a substantial group cannot use it or chooses not to. Contraindications include a history of certain hormone-sensitive cancers, thromboembolic disease, and some liver conditions.
Women being treated for breast cancer with hormone-suppressing therapy sit at the center of this gap. Their treatment deliberately reduces estrogen; hot flashes are a common and severe consequence, and hormone therapy is generally not an option. This trial enrolled postmenopausal women rather than that specific population, so whether the drug helps women on cancer therapy is untested.
Sleep disruption is the outcome that often matters most in daily life. Night sweats fragment sleep, and the downstream effects on concentration, mood, and work capacity are frequently what drive women to seek care. The reported sleep improvement is therefore clinically meaningful if it holds up.
The Evidence Check Before Anyone Gets Excited
The study type is a randomized, double-blind, placebo-controlled trial, the Phase 2 portion of a Phase 1/2 study. That is a design, not an observational analysis, and it is a genuine strength.
The limitations are equally real. Ninety-two participants are a small sample, four weeks is a short follow-up for a condition that persists for years, and the reported figures come from a company announcement rather than a peer-reviewed publication. Topline press releases present selected results; full data allow independent assessment.
The placebo response is worth noting rather than dismissing. A 33 percent reduction in hot flash frequency in the placebo group is substantial, which is characteristic of this symptom and part of why trials require a control arm.
What the trial did not establish is durability, safety over longer exposure, effectiveness in women on hormone-suppressing cancer therapy, or how the drug compares directly with existing options. No head-to-head trial against fezolinetant or hormone therapy has been conducted, and the company's description of the results as best-in-class is a marketing characterization rather than a comparative finding.
What Women Dealing with Hot Flashes Can Do Now
This drug is investigational and is not available. Phase 3 trials would need to be conducted, completed, and reviewed by the FDA before any prescription is possible, a process that typically takes years.
Women with bothersome symptoms have options today and should not wait for this one. Hormone therapy remains the most effective treatment for vasomotor symptoms in women who are candidates for it, and the risk-benefit calculation depends on age, time since menopause, and personal medical history. That is a conversation for a clinician who knows the full picture.
Approved nonhormonal options exist, including fezolinetant and several antidepressants used for this purpose, each with its own side effect and monitoring profile. Women who tried one option and stopped because of side effects should know that others exist.
Anyone taking fezolinetant should follow the prescribed liver monitoring schedule and report symptoms such as yellowing of the skin or eyes, dark urine, unusual fatigue, nausea or abdominal pain to their clinician promptly. Nobody should start or stop a prescribed medication based on a news report about an investigational drug.
Women interested in participating in research can search for registered clinical trials and discuss eligibility with their own clinician. AbCellera has said it is continuing the Phase 2 study to further assess safety and efficacy and has not announced a Phase 3 timeline. MedicalDaily will report peer-reviewed publication of these data, any longer-term safety findings, and the start of late-stage trials.
Key Questions Answered
What did the trial find? A single 600-milligram subcutaneous dose of ABCL635 reduced moderate-to-severe hot flash frequency by 83 percent at four weeks versus 33 percent for placebo, and severity by 58 percent versus 12 percent.
How large was the study? Ninety-two postmenopausal women averaging about 10 moderate or severe hot flashes per day were randomized one-to-one in the Phase 2 portion of a Phase 1/2 trial.
How is this different from existing nonhormonal drugs? It targets the same NK3 receptor as the approved pill fezolinetant but is an antibody designed for long-acting subcutaneous dosing rather than a daily small-molecule tablet processed through the liver.
Is it available? No. It is investigational. Phase 3 trials and FDA review would be required first, a process that typically takes years.
What are the limitations? Small sample, four-week follow-up, company announcement rather than peer-reviewed publication, substantial placebo response, and no head-to-head comparison with existing treatments.
Who might benefit most? Women who cannot use hormone therapy, including those with certain contraindications, and potentially women on hormone-suppressing cancer treatment, though that population was not enrolled in this trial.
What should women with hot flashes do now? Discuss current options with a clinician, including hormone therapy for candidates and approved nonhormonal treatments. Do not start or stop medication based on investigational drug news.
