Greenwich LifeSciences' Cancer Vaccine Trial Accelerates, Early Data Hints at Major Breakthrough

STAFFORD, TX – March 03, 2026 – A late-stage clinical trial for an immunotherapy designed to prevent breast cancer recurrence is advancing at a record pace, with promising early data reinforcing hopes for a new line of defense against the disease. Greenwich LifeSciences, Inc. (Nasdaq: GLSI) announced today a significant acceleration in patient screening for its Phase III trial, FLAMINGO-01, which is evaluating a novel treatment, GLSI-100.

The company reported a 33% increase in its annual patient screening rate, now exceeding 800 individuals per year across clinical sites in the United States and Europe. This surge in enrollment not only signals strong interest from clinicians and patients but also potentially shortens the timeline for obtaining definitive results for an immunotherapy that has already received Fast Track designation from the U.S. Food and Drug Administration.

Operational Prowess Fuels Trial Momentum

The dramatic increase in patient screening is a testament to the company's expanding operational footprint. According to the announcement, this momentum is largely driven by new clinical sites activated throughout 2025 and growing enthusiasm at existing locations. Over the last six months, Greenwich LifeSciences achieved a screening rate of approximately 200 patients per quarter, a new high for the study.

"While the approximately 33% increase to over 800 patients screened per year is impressive, marking our success in optimizing and expanding our clinical operations in 2025, we may have yet to see the peak screen rate for the study," commented CEO Snehal Patel.

This acceleration has led to a critical milestone: the full enrollment of the trial's 250-patient non-HLA-A*02 arm. In this open-label portion of the study, every participant receives the GLSI-100 immunotherapy, providing a substantial pool of data on the treatment's effects. The trial also includes a larger, double-blinded arm of approximately 500 patients with the HLA-A*02 genetic marker, who are randomized to receive either GLSI-100 or a placebo.

The company's execution has not gone unnoticed by the market. Shares of GLSI have surged approximately 134% over the past year, reflecting investor confidence in the trial's progress and the drug's potential. A recent financing round in January 2026 secured an additional $7 million, bolstering the company's cash reserves to over $12.5 million and positioning it to fund operations through the remainder of the year without issue.

Echoes of Success: Preliminary Data Mirrors Earlier Triumph

Beyond the operational milestones, the company shared a tantalizing glimpse of preliminary data from the now fully enrolled non-HLA-A*02 arm. An initial analysis reveals an approximately 80% reduction in the breast cancer recurrence rate for patients who have completed the initial six-month treatment course, known as the Primary Immunization Series (PIS).

This finding is particularly significant because it closely mirrors the landmark results from the company's earlier Phase IIb study. In that trial, which followed patients for five years, those treated with GLSI-100 saw a disease-free survival rate of 100% after completing the PIS, compared to 89.4% in the placebo group—a reduction in recurrence risk of over 80%. The consistency between the early Phase III observations and the robust Phase IIb data is a key indicator that clinical trial experts often look for as a sign of a drug's potential efficacy.

The company noted that the immune response and safety profile in the current trial are also trending similarly to the Phase IIb study, where GLSI-100 was well-tolerated with no serious adverse events attributed to the drug. To date, the independent Data Safety Monitoring Board for FLAMINGO-01 has met twice in 2025 and recommended the study continue without modification.

The Science of Prevention: Training the Immune System

GLSI-100 represents a different approach to fighting HER2-positive breast cancer, a type that affects a significant portion of patients. While many existing therapies are designed to attack active tumors, GLSI-100 is an immunotherapy—often described in vaccine-like terms—intended to prevent the cancer from ever coming back. It is administered to high-risk patients who have already completed surgery and standard adjuvant treatments like trastuzumab (Herceptin).

The treatment consists of GP2, a small peptide derived from the HER2 protein, combined with an immune-stimulant called GM-CSF. The combination is designed to "train" the patient's T-cells to recognize and destroy any lingering cancer cells that express the HER2 protein, thereby preventing a relapse. The initial six injections over six months constitute the PIS, aimed at building a peak immune response, followed by booster shots every six months to maintain long-term protection.

By including both HLA-A*02 and non-HLA-A*02 patient populations, the FLAMINGO-01 trial is designed to assess GLSI-100's effectiveness across a broad spectrum of individuals, which is crucial for its potential as a widely applicable therapy.

A New Strategy in a Crowded Field

The market for HER2-positive breast cancer therapies is a multi-billion dollar arena dominated by pharmaceutical giants and highly effective treatments. Monoclonal antibodies like Herceptin and Perjeta, and powerful antibody-drug conjugates (ADCs) such as Kadcyla and Enhertu, have revolutionized patient outcomes.

However, Greenwich LifeSciences is carving out a distinct and critical niche. Its focus is not on treating active metastatic disease but on preventing it in the first place for patients deemed to be at high risk of recurrence despite completing standard care. This preventative strategy addresses a profound area of unmet need and anxiety for survivors who live with the fear of their cancer returning. If successful, GLSI-100 would not necessarily compete with existing frontline therapies but would rather complement them, offering a new layer of protection after those treatments are finished.

The path forward for FLAMINGO-01 is clearly defined. The trial's primary endpoint is invasive breast cancer-free survival, and it is designed to run until 28 recurrence events are observed. A crucial interim analysis for superiority and futility is planned after just 14 events have occurred. With patient enrollment accelerating and promising early data in hand, Greenwich LifeSciences and the many patients hoping for a new tool to keep breast cancer at bay are watching these numbers with keen interest.