Azidothymidine and interferon-alpha in vitro effects on hematopoiesis: protective in vitro activity of IL-1 and GM-CSF.

Preclinical and clinical studies with an azidothymidine (AZT)/interferon-alpha (IFN-alpha) combination resulted in a marked and synergistic antiretroviral activity. The administration of the two drugs in HIV-seropositive patients affected with Kaposi's sarcoma, however, induced neutropenia, thrombocytopenia, and, in some cases, anemia. A possible means to improve the therapeutic index of AZT and/or IFN-alpha in AIDS patients could be the addition of hematopoietic growth factors. In vitro activity of cytokines on the hematotoxicity of the AZT-IFN-alpha association has not yet been studied. We have performed an in vitro study to evaluate the toxicity of AZT, IFN-alpha, or both on peripheral blood hematopoietic progenitors (CFU-GM and BFU-E) and to assess the activity of interleukin 1 (IL-1), granulocyte-macrophage colony-stimulating factor (GM-CSF), or both in modifying AZT-IFN-alpha hematotoxicity. Results indicate that AZT, IFN-alpha, and combinations of the two have a dose-dependent inhibitory effect on the in vitro growth of peripheral blood hematopoietic progenitors. Combinations of AZT and IFN-alpha inhibited CFU-GM and BFU-E proliferation in an additive manner. Neither IL-1 nor GM-CSF alone was able to induce a significant reduction of AZT-induced damage. Only the addition to the cultures of both cytokines partially curbed the antiproliferative activity of AZT at low dosages.