Shares of Greenwich LifeSciences (NASDAQ:GLSI) advanced in premarket trading Monday, rising by more than 4% after the company released data from its late-stage FLAMINGO-01 study of the GLSI-100 vaccine.
The company reported that GLSI-100 generated a stronger immune response in participants of the FLAMINGO-01 trial. The study is designed to test the vaccine's ability to prevent breast cancer from returning after patients complete standard treatment.
GLSI-100 specifically targets HER2-positive breast cancer, a subtype described by the company as aggressive and with a higher likelihood of recurrence. In a subset of patients who do not carry a particular immune system gene known as HLA-A02, the measured immune response rose to 20.4% after treatment, up from 5.2% at the trial’s start, Greenwich LifeSciences said.
Alongside that increase in immune response, the company reported a decline in breast cancer recurrence of up to 80% in the same HLA-A02-negative patient group following the initial series of injections. Greenwich LifeSciences noted that these findings are consistent with earlier results.
The company added that it may pursue regulatory approval for GLSI-100 in both genetic subgroups covered by the trial, with a decision contingent on final trial results. That conditional approach underscores the role of the remaining study endpoints in shaping any approval strategy.
Investors responded promptly to the interim data, pushing the stock higher in premarket trading on Monday. The firm framed the reported immune and recurrence signals as supportive of the vaccine’s potential benefit in the tested population, while reserving broader conclusions pending the complete dataset.
Contextual note - The FLAMINGO-01 study is characterized in the company’s statement as a late-stage trial, and the reported figures reflect the responses observed after the initial set of injections in the specified patient subgroup.