Phase I study of recombinant human granulocyte-macrophage colony-stimulating factor in patients with bone marrow failure and malignancy.

Twenty-five patients with malignancy and/or bone marrow failure were treated with recombinant human granulocyte macrophage colony-stimulating factor (rh GM-CSF) (specific activity 5 x 10(7) units/mg, purity greater than 95%) given by continuous intravenous infusion at various fixed dose levels (15-500 micrograms/m2/day), as part of a phase I study. Treatment was associated with marked increases in white blood cell counts (2-70 fold), consisting mainly of neutrophilic granulocytes. Significant increases were also observed in eosinophils, monocytes and lymphocytes. In addition six patients had multilineage responses characterized by increases in platelet counts (greater than 2 fold and greater than 100,000/mm3) and reticulocyte counts (greater than 2 fold). Three of these 6 patients did not require red cell or platelet transfusion for 17 to 37 weeks. Treatment also resulted in an increase in bone marrow cellularity and myeloid: erythroid cell ratio. The common side effects were constitutional symptoms and bone pain. These findings demonstrate that rh GM-CSF is well tolerated when given by continuous IV infusion and is a potent stimulator of hematopoiesis in vivo.