FPT-155 is a native CD80 fusion protein that functions by (i) enhancing its costimulatory T cell activity without inducing T cell hyperactivation through binding to CD28, and (ii) preventing CTLA-4 from competitively binding to endogenous CD80, thereby allowing CD28 signaling to become dominant in T cell activation in the tumor microenvironment. The gene discussed is CTLA4; the disease is neoplasm.