FDA Fast Tracks Immunotherapy for HER2-Positive Breast Cancer Recurrence

The U.S. Food and Drug Administration (FDA) has granted fast track designation for Greenwich LifeSciences’ lead immunotherapy candidate GLSI-100 in HLA-A*02–positive, HER2-positive breast cancer patients who have completed standard HER2-targeted therapy. The designation recognizes GLSI-100’s potential to improve invasive breast cancer–free survival and addresses a significant unmet need in preventing metastatic recurrence.

GLSI-100 is designed to train the immune system to recognize and attack HER2-expressing cancer cells that may remain after surgery and standard HER2-targeted therapy (such as trastuzumab). By stimulating a long-lasting cytotoxic T-cell response, it aims to reduce the risk of cancer relapse and progression to metastatic disease.

The designation was based on promising data from a Phase IIb randomized, placebo-controlled trial that showed 80 percent or greater reduction in metastatic breast cancer recurrence after five years; peak immune response achieved at six months, sustained with booster doses; noo serious adverse events attributable to GLSI-100; and favorable safety and tolerability profile across 146 patients in Phase I/II trials. According to the researchers, these results suggest GLSI-100, based on the GP2 peptide combined with GM-CSF, could offer durable protection against recurrence in high-risk HER2-positive patients.

There is an ongoing FLAMINGO-01 Phase III trial that aims to confirm GLSI-100’s efficacy and safety in a larger global cohort. That trial will include approximately 500 HLA-A*02 patients randomized to GLSI-100 or placebo. There will be an additional 250 patients of other HLA types receiving GLSI-100 in an open-label arm. The stud is being led by Baylor College of Medicine, with plans for 150 clinical sites worldwide. An interim analysis will assess superiority and futility after 14 events, ensuring early insights into clinical benefit.