Greenwich LifeSciences, Inc. (GLSI) presented new open-label data from its pivotal Phase III FLAMINGO-01 trial of GLSI-100, an immunotherapy designed to prevent breast cancer recurrences, at the AACR Annual Meeting 2026 in San Diego.
The presentation marks the first abstract and poster jointly authored with the trial's Steering Committee, underscoring statistically significant immune response findings.
In the non- HLA-A*02 arm, where all 247 patients received GLSI-100, immune responses to GP2 were measured at baseline and over time using delayed-type hypersensitivity (DTH) skin tests. Results showed a four-fold increase in immune reactions, rising from 5.2% at baseline to 20.4% at month four or six (p < 0.001). Subgroup analysis across HLA types confirmed more frequent immune reactivity after treatment, with increases ranging from 100% to 700%.
These findings support the mechanism of action of GLSI-100, which stimulates the immune system against recurring cancer cells. Preliminary analyses suggest a 70-80% reduction in recurrence rates after the primary immunization series in non-HLA-A*02 patients, consistent with earlier Phase IIb results in HLA-A*02 patients. CEO Snehal Patel noted that the data strengthens the case for combining both HLA-A*02 and non-HLA-A*02 patients in the same randomized arms, enhancing statistical power for regulatory approval.
The FLAMINGO-01 trial has now screened over 1,300 patients across U.S. and European sites, reflecting strong patient interest. The study design includes six initial GLSI-100 injections over six months, followed by booster doses every six months for 2.5 years, aiming to sustain long-term protection.
Greenwich LifeSciences previously reported that its Phase IIb trial achieved an 80% or greater reduction in metastatic breast cancer recurrences over five years of follow-up, with a well-tolerated safety profile. The ongoing Phase III trial is expected to provide confirmatory evidence in a larger patient population, with interim analyses planned once sufficient recurrence events occur.
GLSI has traded between $7.78 and $34.10 over the past year. The stock closed Friday's trading (April 17, 2026) at $27.74, up 2.36%. In the pre-market trading session, the stock is at $28.712, up 3.48%.
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