On September 10, 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 that FDA has granted Fast Track designation for GLSI-100 in the HLA-A*02 patient population (Press release, Greenwich LifeSciences, SEP 10, 2025, View Source [SID1234655920]).
Schedule your 30 min Free 1stOncology Demo!
Discover why more than 1,500 members use 1stOncology™ to excel in:
Early/Late Stage Pipeline Development - Target Scouting - Clinical Biomarkers - Indication Selection & Expansion - BD&L Contacts - Conference Reports - Combinatorial Drug Settings - Companion Diagnostics - Drug Repositioning - First-in-class Analysis - Competitive Analysis - Deals & Licensing
Schedule Your 30 min Free Demo!
The designation specifically states that "GLSI-100 for the treatment of patients with HLA-A*02 genotype and HER2-positive breast cancer who have completed treatment with standard of care HER2/neu targeted therapy to improve invasive breast cancer free survival meets the criteria for Fast Track designation."
The Fast Track designation for GLSI-100 may lead to earlier drug approval as the Company and the FDA can communicate more frequently to expedite the Biologic License Application (BLA) filing of the clinical and manufacturing data from FLAMINGO-01. The Company may be able to utilize a rolling review process, where completed parts of the BLA can be submitted for review, even though other parts of the application are still being completed.
Dr. Jaye Thompson, VP Clinical and Regulatory Affairs, commented, "Greenwich is pleased that the FDA sees the potential of GLSI-100 to change important clinical outcomes in this population of breast cancer patients. We continue to work earnestly to collect data to support a BLA filing demonstrating this benefit."
CEO Snehal Patel commented, "We are excited to have received Fast Track designation. The FDA review of our Fast Track application included a review of the potential of GLSI-100 as a new drug to treat serious conditions and to fill unmet medical need. By showing the potential of GLSI-100 to prevent metastatic breast cancer recurrence in the patient population that we are studying, we were able to estimate the potential lives that could be saved. The Company plans to continue discussions with the FDA, and potentially the European regulatory authorities, to explore additional ways to make GP2 and GLSI-100 available to larger populations."
A description of the Fast Track criteria and process is available on the FDA website:
View Source
As described by the FDA website:
"Fast track is a process designed to facilitate the development, and expedite the review of drugs to treat serious conditions and fill an unmet medical need. The purpose is to get important new drugs to the patient earlier. Fast Track addresses a broad range of serious conditions…Filling an unmet medical need is defined as providing a therapy where none exists or providing a therapy which may be potentially better than available therapy…Once a drug receives Fast Track designation, early and frequent communication between the FDA and a drug company is encouraged throughout the entire drug development and review process. The frequency of communication assures that questions and issues are resolved quickly, often leading to earlier drug approval and access by patients."
The FDA website further states:
"Any drug being developed to treat or prevent a condition with no current therapy obviously is directed at an unmet need. If there are available therapies, a fast track drug must show some advantage over available therapy, such as:
Showing superior effectiveness, effect on serious outcomes or improved effect on serious outcomes
Avoiding serious side effects of an available therapy
Improving the diagnosis of a serious condition where early diagnosis results in an improved outcome
Decreasing a clinical significant toxicity of an available therapy that is common and causes discontinuation of treatment
Ability to address emerging or anticipated public health need
A drug that receives Fast Track designation is eligible for some or all of the following:
More frequent meetings with FDA to discuss the drug’s development plan and ensure collection of appropriate data needed to support drug approval
More frequent written communication from FDA about such things as the design of the proposed clinical trials and use of biomarkers
Eligibility for Accelerated Approval and Priority Review, if relevant criteria are met
Rolling Review, which means that a drug company can submit completed sections of its Biologic License Application (BLA) or New Drug Application (NDA) for review by FDA, rather than waiting until every section of the NDA is completed before the entire application can be reviewed. BLA or NDA review usually does not begin until the drug company has submitted the entire application to the FDA"
Previously Published Phase IIb Data
In the prospective, randomized, single-blinded, placebo-controlled, multi-center (16 sites led by MD Anderson Cancer Center) Phase IIb clinical trial of HLA-A*02 breast cancer patients, 46 HER2/neu 3+ over-expressor patients were treated with GLSI-100, and 50 placebo patients were treated with GM-CSF alone. After 5 years of follow-up, there was an 80% or greater reduction in cancer recurrences in the HER2/neu 3+ patients who were treated with GLSI-100, followed, and remained disease free over the first 6 months, which we believe is the time required to reach peak immunity and thus maximum efficacy and protection. The Phase IIb results can be summarized as follows:
80% or greater reduction in metastatic breast cancer recurrence rate over 5 years of follow-up compared to 20-50% reduction in recurrence rate by other approved products
Peak immune response at 6 months
No reported serious adverse events attributable to treatment
Well-tolerated safety profile
Full immunization was received in the Primary Immunization Series (PIS), which included the first 6 GLSI-100 injections over the first 6 months. The PIS elicited a potent immune response as measured by local skin tests and immunological assays. Further, booster injections given every 6 months prolonged the immune response, thereby providing longer-term protection. In the Phase IIb and three Phase I clinical trials, where 146 patients were treated, the GP2 immunotherapy was well tolerated, and there were no reported serious adverse events related to GLSI-100.
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.