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Greenwich LifeSciences, Inc. (NASDAQ: GLSI) is a clinical-stage biopharmaceutical company headquartered in Stafford, Texas. The company is developing GP2 (GLSI-100), a nine-amino-acid transmembrane peptide immunotherapy targeting the HER2/neu receptor to prevent breast cancer recurrences in post-surgical patients. As of December 26, 2025, the stock closed at $21.7250, reflecting a 26.23% increase, on a volume of 509,147 shares.
Corporate Structure
Greenwich LifeSciences operates under a governance framework led by Chairman David B. McWilliams, who has over 40 years of experience in the biopharmaceutical and healthcare sectors. The board and executive team have backgrounds in clinical research, gene-based therapies, corporate development, and investment banking. The company’s global Phase III trial network includes more than 150 active sites across the United States and Europe, with partnerships involving US Oncology, GEICAM (Spain), Unicancer (France), GBG (Germany), GIM (Italy), and a Polish network.
Breast cancer by Victoria Strukovskaya
Recent Developments
On April 3, 2025, Greenwich LifeSciences provided an update on its Flamingo-01 Phase III trial:
- Preliminary data for both HLA-A02 and non-HLA-A02 patient arms are aligning with expectations.
- The non-HLA-A*02 arm was expanded to 250 patients following regulatory approvals in the US and EU.
- Screening rates exceeded 150 patients per quarter in Q1 2025, translating to approximately 600 patients per year, across 40 US sites and 77 EU sites.
- The company plans to activate an additional 40 European sites by year-end, potentially increasing total global trial sites to over 150.
These developments warrant consideration of an open-label third arm, which may function as a parallel Phase III study to explore additional marketing approval pathways for GP2.
Financial and Strategic Analysis
As of November 14, 2025, Greenwich LifeSciences reported in its Quarterly Report (Form 10-Q):
- Net loss attributable to common shareholders: $19.48 million.
- Diluted EPS (TTM): –$1.46.
- Total cash on hand: $3.81 million.
- No revenues recognized to date, aligning with the company's focus on research and development expenditures.
The company’s market capitalization is approximately $180 million, with a 5-year beta of 2.92. Greenwich LifeSciences anticipates that GP2 could potentially address up to 30% of surgical breast cancer patients—around 44,000 new patients per year in the US—possibly preventing 4,000 to 5,000 recurrences annually. The ongoing Flamingo-01 trial is a primary component of its regulatory and commercialization strategy.
Market Position and Industry Context
Breast cancer presents a significant unmet need: in 2025, an estimated 700,000 new cases and 9.5 million survivors are projected in the US and EU. Standard HER2/neu therapies, including Herceptin and Kadcyla, reduce recurrence rates by approximately 50% in adjuvant and neoadjuvant settings, respectively. However, a significant proportion of patients still experience recurrence. In a 2018 Phase IIb trial led by MD Anderson, GP2 demonstrated an 80% or greater reduction in metastatic recurrence over five years for HER2/neu 3+ patients, with no serious adverse events reported. As an immunotherapy with a favorable safety profile, GP2 aims to offer an option for patients who do not respond to existing HER2/neu-targeted treatments.
tl;dr
On December 26, 2025, GLSI shares rose 26.23% to $21.7250 amid progress in the global Flamingo-01 Phase III trial. April 3, 2025, data indicate expected immune responses in both HLA-A02 and non-HLA-A02 arms, the latter now expanded to 250 patients. Screening rates reached 600 per year across 117 active sites in Q1 2025, with up to 40 new EU sites planned for activation. The company is evaluating the addition of a second parallel Phase III pathway to broaden regulatory approval and market reach for GP2.
