L-K6L9, a cytolytic peptide comprised of L-isomer leucine and lysine, demonstrates cytotoxicity against both androgen-independent (LNCaP-CL1) and androgen-dependent (22Rv1 and LNCaP) human prostate cancer cells, with LC50 values of 4, 4, and 6 µM, respectively. It also affects non-cancerous cells, including NIH3T3 mouse fibroblasts and OL human foreskin fibroblasts, with LC50s of 7 and 5 µM, respectively. Furthermore, at a concentration of 100 µM, L-K6L9 induces hemolysis in isolated human erythrocytes.