Greenwich LifeSciences, Inc. (USA, Nasdaq: GLSI) announced new patent claims for its Fast Track-designated asset GLSI-100, a peptide-based immunotherapy composed of the GP2 antigen and the adjuvant GM-CSF, targeting breast cancer recurrence prevention in HER2-positive patients. The claims, filed with patent authorities and not yet granted, are grounded in statistically significant open-label immune response and recurrence rate data from the ongoing Phase III FLAMINGO-01 trial (NCT05232916). The filing seeks to extend coverage to non-HLA-A02 patients, a population previously outside the primary scope of the program. If granted following successful prosecution, the patent would provide protection through 2045.
GLSI-100 operates through antigen-specific cellular immunity. GP2 is a 9 amino acid transmembrane peptide derived from the HER2/neu protein, a cell surface receptor overexpressed in a subset of breast cancers. When administered with GM-CSF as an immunologic adjuvant, the formulation is designed to prime and expand HER2-specific cytotoxic T cells capable of recognizing and eliminating residual HER2-expressing tumor cells following surgery and standard HER2-directed therapy. The mechanism does not inhibit HER2 signaling directly but instead recruits the adaptive immune system to establish durable post-surgical surveillance against minimal residual disease.
The original clinical rationale for GLSI-100 centered on HLA-A02-positive patients, as GP2 was initially characterized as an epitope presented by the HLA-A02 allele. The new patent claims assert clinical benefit in non-HLA-A02 patients based on data from the open-label arm of FLAMINGO-01, in which 250 non-HLA-A02 patients were enrolled and all received GLSI-100. A preliminary analysis of recurrence rates following the Primary Immunization Series, defined as the first six injections administered over six months, showed an approximately 80% reduction in recurrence rate in this cohort. The company states that the immune response trajectory and safety profile in non-HLA-A02 patients trend similarly to the HLA-A02 arms of FLAMINGO-01 and to the earlier Phase IIb study. The company has noted that this data is preliminary, not fully reviewed, and not a prediction of final study outcomes.
The Phase IIb study, conducted at 16 sites led by MD Anderson Cancer Center, enrolled 46 HER2/neu 3+ overexpressor patients treated with GLSI-100 and 50 placebo-treated patients receiving GM-CSF alone. After five years of follow-up, an 80% or greater reduction in metastatic breast cancer recurrence rate was observed in treated patients who completed the Primary Immunization Series and remained disease-free over the first six months. The FLAMINGO-01 Phase III trial is designed to detect a hazard ratio of 0.3 in invasive breast cancer-free survival, with 28 events required for primary analysis and an interim analysis for superiority and futility triggered at 14 events.