Greenwich LifeSciences’ Vaccine Shows 80% Recurrence Reduction in FLAMINGO-01

Greenwich LifeSciences (NASDAQ:GLSI) reported early signs of efficacy from the open-label non-HLA-A*02 arm of its Phase 3 FLAMINGO-01 trial, saying preliminary analyses point to an approximately 80% reduction in breast cancer recurrence rates in the fully enrolled 250-patient cohort.

According to the company, two analytic methods yielded similarly encouraging directional trends.

Method 1 compared recurrence rates in patients who completed the Primary Immunization Series (PIS) with historical benchmarks from the T-DM1 arm of the KATHERINE trial, a frequently referenced standard in high-risk HER2-positive early breast cancer.

Method 2 compared recurrence events occurring during the six-month PIS period—representing 100 patient-years—with recurrence during post-PIS follow-up, covering 132 patient-years.

The first patient in this trial arm has now completed both primary and booster vaccinations, marking a key progression milestone for the study’s immunization schedule.

Greenwich emphasized that the results remain preliminary, noting that the arm is open-label, lacks a direct placebo comparator, and that datasets are not yet complete or fully reviewed.

The company cautioned that additional analyses, maturation of follow-up time, and full adjudication of recurrence events will be required before drawing definitive conclusions about clinical benefit.

FLAMINGO-01 is designed to evaluate a therapeutic breast cancer vaccine aimed at reducing recurrence in HER2-positive patients who have completed standard therapy.

The non-HLA-A*02 arm broadens the trial’s applicability across patient populations who may respond differently based on genetic presentation.