Immunorestorative properties of ST 789 on experimentally immunosuppressed and infected mice.

ST 789, a newly synthesized chemical characterized by an aminoacidic group joined to the N9 position of the hypoxanthine ring, has recently been shown to be endowed with immunomodulatory properties. In this study we tested ST 789 in vivo for protective effects in Cyclophosphamide-immunosuppressed CD1 mice experimentally infected with several bacterial and fungal pathogens. We found that immunosuppressed mice infected with either fungi or bacteria were significantly protected, as evaluated both by percent mortality and survival time, when treated with doses of ST 789 even as low as 0.2 mg/kg/day. We also observed a marked synergism when the mice were first treated with ST 789 and then additionally treated with subeffective doses of antibiotics such as Amphotericin B, Ceftazidime, and Gentamicin. Even though further studies are required to elucidate the mechanisms underlying the ST 789 effects, these results show that ST 789 is a very promising new immunomodulator whose therapeutic potential has yet to be fully exploited.