TLDR
- GLSI rallies after Phase III data signals 80% drop in breast cancer recurrence rates
- Open-label FLAMINGO-01 arm shows a strong efficacy trend after the full immunization series
- Recurrence rates fall sharply versus historical TDM1 benchmarks in early analysis
- Safety and immune response remain consistent with prior Phase IIb trial results
- Global trial expansion supports broader validation of GLSI-100 vaccine strategy
Greenwich LifeSciences, Inc. (GLSI) surged above $25 early today before retreating to $11.93, up 11.14% by 11:50 AM EST.
Greenwich LifeSciences, Inc., GLSI
The sharp early spike followed a major announcement of an 80% breast cancer recurrence reduction in its ongoing Phase III trial. The news comes as the company advances GLSI-100, its immunotherapy aimed at preventing cancer recurrence in HER2-positive breast cancer patients.
Non-HLA-A02 Arm Demonstrates 80% Recurrence Reduction
Greenwich LifeSciences revealed new data from its FLAMINGO-01 Phase III trial’s non-HLA-A02 open-label arm. This cohort, composed of 250 patients, showed an estimated 80% drop in recurrence rates following the full primary immunization series. The analysis used historical comparisons from the Katherine study and within-trial timing metrics to derive this result.
The data compares recurrence rates during and after the primary immunization series using exposure periods of 100 and 132 patient years, respectively. Patients showed significantly fewer recurrences after completing the first six GLSI-100 injections, which are necessary for peak immune protection. These results reflect a similar trend to GLSI’s Phase IIb trial outcomes, which also demonstrated reduced recurrence risk.
Though the non-HLA-A02 arm lacks a placebo group, results align closely with historical data from comparable treatment populations. Most participants previously received TDM1 (Kadcyla) before GLSI-100 treatment, further validating the observed outcome. The recurrence reduction trend supports the continued development of GLSI-100 in broader patient groups.
Safety, Immune Response Consistent With Phase IIb Data
The company reported safety and immune response profiles in the non-HLA-A02 group that mirrored previous Phase IIb trial results. The first patient in the open-label arm has now completed all 11 injections, marking a significant milestone in the trial timeline. Immune responses increased during treatment and remained comparable to earlier treated HLA-A02 patients.
The Primary Immunization Series was followed by booster shots every six months to extend immune protection. Preliminary safety data from the ongoing trial indicate tolerability consistent with earlier findings. The company noted these results as promising, yet emphasized that data is still under analysis and subject to change.
The FLAMINGO-01 trial remains blinded for placebo-controlled arms, but open-label observations continue to guide treatment plans. The study design includes up to 750 participants across multiple global sites. Full follow-up data and interim analysis will be needed to confirm long-term efficacy.
Background and Trial Expansion Efforts
Greenwich LifeSciences is currently enrolling patients across 140 sites in the US and Europe, recently expanding into Austria, Portugal, and Belgium. The company aims to prevent breast cancer recurrence in HER2/neu 3+ patients through a peptide-based immunotherapy approach. FLAMINGO-01 evaluates GLSI-100 combined with GM-CSF in patients post-surgery and post-HER2-directed therapies.
The company’s Phase IIb trial previously recorded over 80% recurrence reduction in a smaller HLA-A02 patient group. Those results laid the groundwork for the Phase III design, targeting a hazard ratio of 0.3 in invasive breast cancer-free survival. Interim results will be assessed after 14 recurrence events among 28 expected.
The company’s trial is led by Baylor College of Medicine and includes both double-blinded and open-label arms. Non-HLA-A02 patients receive GLSI-100 directly, while HLA-A02 patients are randomized to either GLSI-100 or placebo. The ultimate goal is to extend protection to a broader patient population beyond genetic subtypes.
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