Greenwich LifeSciences Completes Enrollment in Non-HLA-A*02 Arm of Phase III FLAMINGO-01 Trial for Breast Cancer Prevention
核心洞察
Greenwich LifeSciences has completed enrollment of 250 patients in the non-HLA-A*02 (搜索) arm of its Phase III FLAMINGO-01 trial evaluating GLSI-100 immunotherapy for preventing breast cancer recurrence.
The company has screened over 1,000 patients across 140 active sites globally, maintaining a screening rate of approximately 150 patients per quarter.
Preliminary analysis suggests promising trends in immune response and safety profiles similar to previous Phase IIb results, where breast cancer recurrences were reduced by up to 80%.
Greenwich LifeSciences has achieved a significant milestone in its Phase III FLAMINGO-01 trial by completing enrollment in the non-HLA-A*02 (搜索) arm, marking a major advancement in the development of GLSI-100, an immunotherapy designed to prevent breast cancer recurrences. The company announced on December 8, 2025, that it has successfully enrolled 250 patients in this open-label arm of the trial.
Trial Design and Patient Population
FLAMINGO-01 is structured as a comprehensive Phase III clinical trial with multiple arms targeting different patient populations based on HLA typing. The trial includes approximately 500 HLA-A02 patients randomized to GLSI-100 or placebo in double-blinded arms, while up to 250 patients of other HLA types receive GLSI-100 in the third open-label arm. Non-HLA-A02 patients, who lack the HLA-A*02 (搜索) allele from either parent, represent approximately 55% of the patient population in FLAMINGO-01.
The trial is designed to evaluate GLSI-100 in HER2 (搜索)-positive breast cancer patients who had residual disease or high-risk pathologic complete response at surgery and have completed both neoadjuvant and postoperative adjuvant trastuzumab-based treatment. The study has been powered to detect a hazard ratio of 0.3 in invasive breast cancer-free survival, requiring 28 events with an interim analysis planned when 14 events occur.
Global Screening Success
The company has demonstrated remarkable enrollment momentum, screening over 1,000 patients across approximately 140 active sites, including 40 US sites and 100 European sites. This represents a screening rate of approximately 150 patients per quarter, equivalent to 600 patients annually. CEO Snehal Patel noted that "reaching 1,000 screened patients confirms that the interest from doctors and patients is high."
The most commonly enrolled non-HLA-A02 types in FLAMINGO-01 include HLA-A03, HLA-A24, HLA-A01, HLA-A11, HLA-A68, HLA-A29, HLA-A30, HLA-A23, and HLA-A33.
Promising Early Results
Greenwich LifeSciences has reported encouraging preliminary observations from the non-HLA-A02 arm. The immune response at baseline prior to GLSI-100 treatment, the increasing immune response during the primary immunization series, and the safety profile of non-HLA-A02 patients are trending similarly to the HLA-A*02 (搜索) arms of FLAMINGO-01 and to the Phase IIb study results.
In the previous Phase IIb study, breast cancer recurrences were reduced by up to 80% or more, with no metastatic breast cancer recurrences reported. Patel emphasized the significance of the current dataset: "All 250 patients received GLSI-100, which is 5 times more than the approximately 50 patients treated in the Phase IIb trial."
Regulatory Strategy and Future Plans
The company has stopped enrolling in the non-HLA-A02 arm and is approaching regulatory agencies to seek approval for continued enrollment of new non-HLA-A02 patients in a randomized manner with a control arm. Greenwich LifeSciences has continued screening a large number of these patients to enable rapid enrollment if regulatory approval is received.
The enrollment of HLA-A*02 (搜索) patients in the 500-patient randomized arms continues unaffected, while the company seeks to increase the size of these arms to prevent enrollment stoppage prior to interim analyses.
Market Potential and Patent Strategy
Greenwich LifeSciences believes the non-HLA-A*02 (搜索) patient population could double the number of eligible patients in the US and Europe to approximately 88,000 new patients per year. Using drug prices comparable to Kadcyla or Enhertu, the company estimates a market potential in the range of $8-10 billion per year.
The company has positioned the use of GLSI-100 in the non-HLA-A*02 (搜索) patient population as its own invention, with patent claims that it believes are not subject to license, royalties, or milestone payments. These patent claims are intended to complement other recently filed patent claims that could potentially extend patent protection of GLSI-100 beyond 2040.
Treatment Context and Eligibility
FLAMINGO-01 continues to accept patients previously treated with Enhertu (trastuzumab deruxtecan), as Greenwich LifeSciences believes GLSI-100 will synergize with any trastuzumab-based treatment in neoadjuvant or adjuvant settings. The trial targets the significant breast cancer population, with one in eight US women developing invasive breast cancer over their lifetime, representing approximately 300,000 new breast cancer patients and 4 million breast cancer survivors.
HER2 (搜索) protein is expressed in 75% of breast cancers at various levels, making GLSI-100's mechanism of action broadly applicable across the breast cancer patient population. GLSI-100 consists of GP2, a 9-amino acid transmembrane peptide of the HER2 protein, combined with GM-CSF as an adjuvant.