8-Azaguanine is a purine analogue which shows antineoplastic activity. In Vitro: 8-Azaguanine is a purine analogue which shows antineoplastic activity. The results show that cell viability decreases after incubation with 8-Azaguanine, in a dose and time dependent manner. After 24 h of treatment with 8-Azaguanine the IC₅₀ for CEM cell line is about 100 μM while for MOLT3 cell line the IC₅₀ is about 10 μM. CEM and MOLT3 cells surface expression of CD26 increases after treatment with 8-Azaguanine in a concentrations dependent manner^[1].