** Shares of biotech firm Greenwich LifeSciences GLSI.O rise 4.3% to $28.94 premarket

** Co says its experimental breast cancer vaccine shows stronger immune response

** Says the late-stage FLAMINGO‑01 study tests GLSI‑100, an experimental vaccine aimed at preventing breast cancer from coming back after standard treatment

** The vaccine targets HER2‑positive breast cancer, an aggressive form of the disease that is more likely to return

** In patients without a specific immune system gene (HLA‑A*02), immune response rose to 20.4% after treatment from 5.2% at the start, co says

** Says breast cancer recurrence in this group fell by up to 80% after the initial set of injections, consistent with earlier results

** Adds it may seek approval for the vaccine in both genetic subgroups depending on final trial results

** As of last close, shares up ~32% this year