Greenwich LifeSciences, Inc. (Nasdaq: GLSI) announced on July 9, 2026 that the European Medicines Agency has completed its review and will allow use of commercially manufactured GP2 in the FLAMINGO-01 Phase III trial across European sites. The clinical-stage biopharmaceutical company is developing GLSI-100, an immunotherapy designed to prevent breast cancer recurrences.
The company manufactured the first three commercial lots of GP2 active ingredient in 2023 at an approved commercial facility, producing enough material for approximately 200,000 doses.
In 2024, the company completed the first commercial lot filling of GP2 into vials for clinical and commercial use, and it initiated drug stability programs across all four lots.
US And European Sites Align On Same GP2 Batch
The FDA reviewed data on the commercial lots and approved the first commercial lot of GP2 vials for use in FLAMINGO-01 in the US in early 2026.
Approximately 40 to 50 US sites have since received commercially manufactured GP2 vials and started treating patients. The company internalized its clinical team in the fourth quarter of 2025, which supported distribution of the vials and coordination with US pharmacists and warehouse partners.
With the EMA’s clearance, all US and European clinical sites are expected to use the same GP2 lot, and shipments to European pharmacies are already underway. Total site count for the trial has grown from 160 to approximately 170 to 180. Greenwich LifeSciences is separately pursuing regulatory approval to use the same lot in the UK and Canada.
FLAMINGO-01 Trial Reaches Key Enrollment And Data Milestones
FLAMINGO-01 has screened more than 1,300 patients, with a current screening rate of roughly 800 patients per year. The trial’s 250-patient non-HLA-A*02 arm, in which all participants receive GLSI-100, is now fully enrolled. This arm includes five times more treated patients than the roughly 50 patients treated in the earlier Phase IIb trial.
Treatment follows a Primary Immunization Series of six GLSI-100 injections over the first six months, followed by booster injections every six months to extend the immune response.
A preliminary analysis of the non-HLA-A02 arm, conducted after completion of the Primary Immunization Series, showed an approximate 70 to 80 percent reduction in recurrence rate.
The company noted this trend aligns with Phase IIb results, in which HLA-A02 patients saw recurrence reductions of up to 80 percent, compared with a 20 to 50 percent reduction reported for other approved products. The company cautioned that this comparison is directional rather than a formal head-to-head result.
Baseline immune response, immune response during the injection series, and the safety profile of non-HLA-A02 patients are trending similarly to the HLA-A02 arms of the trial and to the earlier Phase IIb study.
Data from posters presented at the AACR 2026 and ASCO 2026 meetings showed that delayed-type hypersensitivity and injection site reactions increased at a statistically significant rate over time, and that each HLA-A type showed more immune reactivity after GLSI-100 treatment than at baseline.
The company said this baseline reactivity suggests GP2 may function as a natural antigen, with GP2-specific T cells potentially present in some patients before treatment. Researchers observed a similar baseline response pattern in the Phase IIb trial and are seeing it in the blinded, randomized HLA-A*02 arms of FLAMINGO-01.
Greenwich LifeSciences noted that this open-label analysis was conducted in a way that preserves the trial’s blind, and that the underlying recurrence, immune response, and safety data remain preliminary and incomplete.
The company said that any comparison to Phase IIb data does not predict final study outcomes, which may differ once the trial concludes.
Phase IIb Study Results Behind GLSI-100
The Phase IIb trial was a prospective, randomized, single-blinded, placebo-controlled study conducted across 16 sites led by MD Anderson Cancer Center.
It enrolled 46 HER2/neu 3+ over-expressor breast cancer patients who received GLSI-100 and 50 patients who received placebo in the form of GM-CSF alone.
After five years of follow-up, patients treated with GLSI-100 who remained disease-free through the first six months, the period researchers consider necessary to reach peak immunity, showed an 80 percent or greater reduction in cancer recurrence.
The Primary Immunization Series produced a strong immune response, measured through local skin tests and immunological assays, and the trial reported a well-tolerated safety profile.
About FLAMINGO-01 And GLSI-100
FLAMINGO-01 (NCT05232916) is a Phase III trial evaluating the safety and efficacy of GLSI-100, which combines GP2 and GM-CSF and holds Fast Track designation from the FDA.
The trial enrolls HER2-positive breast cancer patients who had residual disease or a high-risk pathologic complete response at surgery and who completed neoadjuvant and postoperative adjuvant trastuzumab-based treatment.
Baylor College of Medicine leads the trial, which draws on US and European sites at university hospitals and academic and cooperative research networks, with plans to expand to 170 to 180 sites globally.
Breast Cancer And HER2/neu Positivity Context
Roughly one in eight women in the US will develop invasive breast cancer during her lifetime. The US sees approximately 300,000 new breast cancer diagnoses each year and is home to an estimated 4 million breast cancer survivors. HER2, a cell surface receptor protein, appears in about 75 percent of breast cancers at low, intermediate, or high expression levels.
About Greenwich LifeSciences, Inc.
Greenwich LifeSciences is a clinical-stage biopharmaceutical company developing GP2, an immunotherapy intended to prevent breast cancer recurrence in patients who have already undergone surgery.
GP2 is a nine amino acid transmembrane peptide derived from the HER2 protein, which is expressed in about 75 percent of breast cancers at varying levels. The company is currently running its Phase III FLAMINGO-01 trial. More information is available at the company’s website.