FLASH-Breast: Evaluating the Efficacy of Fezolinetant in Reducing Vasomotor Symptoms in Women With Breast Cancer on Endocrine Therapy

This is a phase II, randomized, double-blinded, placebo-controlled trial designed to evaluate the efficacy of fezolinetant (45 mg a day) vs. placebo in reducing moderate to severe vasomotor symptoms (VMS) in breast cancer survivors on endocrine therapy (tamoxifen, aromatase inhibitors). The trial will proceed in a single stage, and the total of 92 participants will be randomized in 1:1 fashion to fezolinetant or placebo arm respectively. After the 7-14-day screening period when all the baseline, pre-treatment measures will be collected, we will record daily data on frequency and severity of VMS and calculate weekly averages of both metrics. After the 12 weeks treatment period, formal efficacy analysis will be conducted and the treatment with fezolinetant will be deemed efficacious if the final weekly average of daily frequency of VMS will be significantly reduced compared to the 'week12 - baseline' difference of the placebo arm. Upon conclusion of the formal 12-week treatment assignment, once VMS final assessment has been recorded, we will unblind the study participants to their treatment assignment. Participants will be then allowed to cross over shall they choose to do so. Due to the vast availability of safety and efficacy data in general population, we did not include interim efficacy/futility or safety analysis.

Our hypothesis is that neurokinin blockade by fezolinetant will significantly reduce vasomotor symptoms in breast cancer survivors on endocrine therapy (tamoxifen or aromatase-inhibitor) measured by mean change in frequency of moderate to severe VMS based on patient-reported data from baseline to 12-weeks.