Streptozocin is a potent DNA-methylating antibiotic. Streptozotocin causes methylation of liver and kidney and pancreatic DNA, but no methylation in brain DNA. IC50 & Target: DNA alkylator^[1] In Vitro: Streptozocin (STZ) shows higher cytotoxic effect in vitro on hematological cell lines compared to Alloxan (ALX). ALX appeares not to be toxic for the studied cell lines with estimated IC₅₀ values of 2809, 3679 or over 4000 μg/mL for HL60, K562 and C1498 cells, respectively. Streptozocin is more toxic, especially for the human myeloid leukemia cell line, HL60. The IC₅₀ values of Streptozocin are 11.7, 904 and 1024 μg/mL for HL60, K562 and C1498 cells, respectively. Results also show that the murine leukemic cells are more resistant to Streptozocin and ALX cytotoxicity than human leukemic cells^[2]. In Vivo: Streptozocin (STZ)-injected mice show tendency to have lower body weight than that observed in animals injected with ALX. Streptozocin -injected mice have significantly fewer splenocytes (22.2±3.2×10⁶; n=10) compared to mice injected with ALX (60.7±4.3×10⁶; n=15; p=0.01)^[2].