Greenwich LifeSciences Reports Promising Phase III Data For FLAMINGO-01 Trial Evaluating GLSI-100, Showing Significant Drop In Breast Cancer Recurrence Rates

Greenwich LifeSciences, Inc. has shared a preliminary update from its fully enrolled Phase III FLAMINGO-01 trial evaluating GLSI-100, an investigational immunotherapy designed to prevent breast cancer recurrence. The update highlights continued improvement in outcomes among patients enrolled in the open-label non-HLA-A*02 arm of the study.

Six months of additional follow-up data show that patients who completed the primary immunisation series (PIS) experienced an annual recurrence rate of less than 1%. The company reported that virtually all patients in this arm have completed the first six monthly vaccinations that form the PIS. On average, about 110 patient-years of new data are added to the study database every six months.

Because this arm lacked a placebo comparator, researchers compared outcomes with historical data from the KATHERINE trial. That study reported an annual recurrence rate of roughly 4% among patients treated with Kadcyla. Most participants in FLAMINGO-01 also received Kadcyla before treatment with GLSI-100.

Based on an average follow-up of 1.2 years, the GLSI-100 treated group recorded a 0.7% annual recurrence rate compared with 4% in the historical control, representing an 83% reduction. The difference was statistically significant (Chi-square test, p < 0.005). Greenwich LifeSciences noted that these findings are preliminary and will continue to be refined as data collection and validation progress.

The company said the trend is consistent with earlier Phase IIb results, where recurrence reductions reached up to 80% in treated patients. FLAMINGO-01 also allows enrollment of patients treated with Enhertu, and future changes in standard of care could influence recurrence assumptions built into the study design. Additional updates may be presented at upcoming scientific meetings.