Stony Brook joins global trial testing vaccine to prevent breast cancer recurrence

A 35-year-old breast-cancer survivor at Stony Brook is stepping into a global trial that could change what follow-up care looks like for a small, high-risk slice of patients: people whose HER2-positive disease has already been treated but could still come back.

Stony Brook University Hospital is the only Long Island site in FLAMINGO-01, a Phase III study testing GLSI-100, also called GP2 plus GM-CSF, against placebo. The trial is randomized, multicenter and placebo-controlled, with about 750 patients expected across roughly 150 to 160 sites worldwide. ClinicalTrials.gov lists the study start date as Aug. 11, 2022, and projects completion in December 2026.

The vaccine is not for newly diagnosed patients, and it is not a replacement for standard cancer treatment. It is designed for adults who are HLA-A*02-positive and HER2/neu-positive, and who have already completed trastuzumab-based neoadjuvant and postoperative adjuvant therapy. Eligible patients include those left with residual disease after surgery, as well as some who reached a high-risk pathologic complete response.

The idea is to train the immune system to recognize HER2/neu-expressing cells before they can return as metastatic disease. Participating centers describe the schedule as six intradermal primary immunization shots spread over six months, followed by booster injections later. Greenwich LifeSciences, which is developing the vaccine, has also said GLSI-100 received FDA Fast Track designation for HLA-A*02-positive and HER2-positive breast cancer.

For Suffolk County patients, the trial’s value is practical as much as scientific: the closest access point is in Stony Brook, without a trip to Manhattan or the mainland. It also comes with a hard truth about hope and hype. Early company-linked reporting on an open-label arm has described recurrence rates of less than 1% per year after the primary immunization series, but FLAMINGO-01 is still underway, and only the full randomized trial can show whether the vaccine truly lowers the odds of recurrence for the people most at risk.