A review in Drug Safety, published on 14 October, revisits an imbalance in neoplasm events seen in the phase 3 programme of fezolinetant, a neurokinin-3 receptor antagonist licensed for menopausal vasomotor symptoms. Regulators had judged it a chance finding without a plausible mechanism.
The authors note that exposure-adjusted rates of non-benign neoplasms rose with dose: 0.2, 0.7 and 1.2 per 100 subject-years on placebo, 30 mg and 45 mg. The relative risk at the licensed dose was 6.6, but with a very wide confidence interval that includes 1. They argue that most references used to dismiss a mechanism concerned a different receptor, and they outline several possible pathways, none needing new cancer formation.
This is an argument for closer surveillance, not proof of harm. For prescribers, it is a reason to record a clear indication, discuss the uncertainty, and report any new neoplasm on treatment.
- Discuss the unresolved neoplasm signal when starting fezolinetant.
- Report any new neoplasm in a patient on fezolinetant to pharmacovigilance.
- Use the licensed dose; the imbalance rose with dose.
- Regulators had judged the imbalance a chance finding; this analysis disputes that reasoning.
Why it matters
It reopens a safety question that regulators had closed, in a drug used by healthy women for symptoms.
Don't overread it
The imbalance was not statistically significant; this is a case for surveillance, not evidence that fezolinetant causes cancer.
The statistics, in plain English
A relative risk of 6.6 with a 95% confidence interval of 0.9 to 51.3 reflects very few events. The interval includes 1, so chance cannot be excluded; its width means the true effect could also be large. A dose-related pattern is what makes the signal worth watching.
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