Greenwich LifeSciences, Inc. (Nasdaq: GLSI) announced that UK regulators have approved the expansion of its Phase III clinical trial, FLAMINGO-01, into the United Kingdom, adding potentially 5 to 10 sites to the approximately 170 to 180 already approved in the US and Europe.

The trial is evaluating GLSI-100, an immunotherapy candidate intended to prevent breast cancer recurrences in HER2-positive patients who have undergone surgery. Greenwich LifeSciences said it is collaborating with The Royal Marsden cancer center on the expansion, with discussions underway at academic sites in London, Cambridge, Edinburgh, Oxford, Manchester, Southampton, Cardiff, and other cities. The principal investigator at The Royal Marsden will serve as the UK national principal investigator and plans to join the trial's Steering Committee.

According to 2019 and 2021–2022 data from Cancer Research UK, approximately 59,400 new breast cancer cases are diagnosed in the UK each year, representing 30% of all new female cancer cases.

The company also provided an update on open-label Phase III data. More than 1,500 patients have been screened at a rate of approximately 600 to 800 per year. The 250-patient non-HLA-A*02 arm is fully enrolled, and a preliminary analysis showed an approximately 70% to 80% reduction in recurrence rate after completion of the Primary Immunization Series. The company cautioned that the data is preliminary and not a prediction of final results.

FLAMINGO-01 is led by Baylor College of Medicine. The trial targets HER2-positive breast cancer patients who had residual disease or high-risk pathologic complete response at surgery and completed trastuzumab-based treatment.