Perforin-IN-2 is a benzosulfonamide perforin inhibitor that alleviates transplant rejection during allogeneic bone marrow/stem cell transplantation. Perforin-IN-2 binds to plasma proteins with a binding rate of 99.8%. Perforin-IN-2 requires a higher concentration (> 900 μM) to achieve optimal perforin inhibition in vivo . Perforin-in-2 can effectively inhibit the lytic activity of recombinant perforin on Jurkat T ( IC 50 =6.65 μM) leukemia cells, and also inhibit the death of K562 leukemia target cells.