Greenwich LifeSciences Provides Global Update on FLAMINGO-01, Screening Over 1,000 Patients to Date

On December 3, 2025 Greenwich LifeSciences, Inc. (Nasdaq: GLSI) (the "Company"), a clinical-stage biopharmaceutical company focused on its Phase III clinical trial, FLAMINGO-01, which is evaluating GLSI-100, an immunotherapy to prevent breast cancer recurrences, reported the following global update on FLAMINGO-01.

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Flamingo-01 Progress to Date

The Company has achieved a major milestone by screening over 1,000 patients in Flamingo-01, continuing its screening rate of approximately 150 patients per quarter or the equivalent of 600 patients per year in approximately 40 US sites and 100 EU sites for a total of 140 active sites. The Company is considering a strategy to continue enrolling in both the HLA-A*02 and non-HLA-A*02 arms until interim analyses are conducted and the appropriate size of each arm can be further assessed.

CEO Snehal Patel commented, "Reaching 1,000 screened patients confirms that the interest from doctors and patients is high. The clinical site start-up activities in Europe in 2025 have further increased the momentum in the study. We are also receiving interest from other countries to join FLAMINGO-01, driven by patient interest. The high screening rate will give the Company many options, including the opportunity to continue enrollment through multiple interim analyses, the potential to realize higher enrollment rates and event rates, and the potential to maximize indications by analyzing efficacy across multiple HLA types in larger patient populations."

About FLAMINGO-01 and GLSI-100

FLAMINGO-01 (NCT05232916) is a Phase III clinical trial designed to evaluate the safety and efficacy of GLSI-100 (GP2 + GM-CSF) in HER2 positive breast cancer patients who had residual disease or high-risk pathologic complete response at surgery and who have completed both neoadjuvant and postoperative adjuvant trastuzumab based treatment. The trial is led by Baylor College of Medicine and currently includes US and European clinical sites from university-based hospitals and academic and cooperative networks with plans to open up to 150 sites globally. In the double-blinded arms of the Phase III trial, approximately 500 HLA-A*02 patients will be randomized to GLSI-100 or placebo, and up to 250 patients of other HLA types will be treated with GLSI-100 in a third arm. The trial has been designed to detect a hazard ratio of 0.3 in invasive breast cancer-free survival, where 28 events will be required. An interim analysis for superiority and futility will be conducted when at least half of those events, 14, have occurred. This sample size provides 80% power if the annual rate of events in placebo-treated subjects is 2.4% or greater.

For more information on FLAMINGO-01, please visit the Company’s website here and clinicaltrials.gov here. Contact information and an interactive map of the majority of participating clinical sites can be viewed under the "Contacts and Locations" section. Please note that the interactive map is not viewable on mobile screens. Related questions and participation interest can be emailed to: [email protected]

About Breast Cancer and HER2/neu Positivity

One in eight U.S. women will develop invasive breast cancer over her lifetime, with approximately 300,000 new breast cancer patients and 4 million breast cancer survivors. HER2 (human epidermal growth factor receptor 2) protein is a cell surface receptor protein that is expressed in a variety of common cancers, including in 75% of breast cancers at low (1+), intermediate (2+), and high (3+ or over-expressor) levels.

(Press release, Greenwich LifeSciences, DEC 3, 2025, View Source [SID1234661092])