Treatment of hairy cell leukemia with granulocyte colony-stimulating factor and recombinant consensus interferon or recombinant interferon-alpha-2b.

Patients with hairy cell leukemia and neutropenia (absolute neutrophil count less than 1.5 x 10(9)/L) were treated with recombinant granulocyte colony-stimulating factor (G-CSF) at doses of 3.6 and 7.2 micrograms/kg by daily subcutaneous injection, until normalization of neutrophil counts occurred. Patients then received either recombinant interferon-alpha-2b (r-IFN-alpha-2b) or a unique IFN, recombinant consensus IFN (rIFN-con-1), each given at doses of 10 micrograms/m2 subcutaneously three times a week, coupled with continued daily G-CSF therapy, for 3 months. After 3 months the G-CSF was discontinued; patients continued to take IFN for 1 year. All 10 patients responded to G-CSF with normalization of neutrophil counts within 2 weeks; the increase in neutrophil counts was greater in previously splenectomized patients. Four patients were treated with r-IFN-alpha-2b, and six were treated with rIFN-con-1. No patients developed recurrent neutropenia with the initiation of IFN therapy. Nine patients are evaluable for response to IFN. Five of six patients demonstrated hematologic improvement with rIFN-con-1, with two patients obtaining complete responses. All three patients receiving r-IFN-alpha-2b demonstrated hematologic improvement; one complete response was observed. Toxicities of both IFNs included influenza-like symptoms. We conclude that G-CSF can abrogate the myelosuppressive effects of IFN, and may be a useful adjunct to this therapy in neutropenic patients. We conclude that rIFN-con-1, the product of a synthetic gene, has activity in the treatment of hairy cell leukemia, and merits clinical investigation in other settings.