Clinical and in vitro antiproliferative properties of recombinant DNA-derived human interferon-α₂

The properties of the recombinant DNA-derived human leukocyte interferon, HuIFNα₂, were studied in patients with advanced leukemia or lymphoma. In vitro, HuIFNα₂induced an increased activity of 2-5A synthetase in leukemic and in control cells indicating cellular responsiveness to IFN. HuIFNα₂also produced a doseresponsive decline in marrow leukemia blast progenitor colony growth, and in normal hematopoietic colony formation in vitro, confirming its antiproliferative effect. A course of intravenous therapy given to a lymphoma patient produced a modest decline in peripheral white blood cell (WBC) and neutrophil counts; higher, more frequent doses in a second patient induced a profound drop in WBC’s, neutrophils, and platelets. When the leukemia patients were given an intravenous course of HuIFNα₂as a sole agent, blast cytoreduction was seen in peripheral blood in three patients, and in marrow of one patient with acute myeloblastic leukemia (AML). Elevated 2-5A synthetase levels could be detected after therapy. No modulation of leukemic cell markers was seen after in vitro or in vivo treatment with HuIFNα₂, implying that the cytoreduction was not linked to blast cell differentiation. These studies suggest that this subtype of recombinant DNA-derived IFN has antileukemic properties, and indicates the possibilities for IFN as an adjunctive form of therapy in leukemia.