Agranulocytosis and hemolytic anemia in patients with renal cell cancer treated with interleukin-12.

Interleukin-12 (IL-12) is a cytokine with effects on immune function and hematopoiesis. In this article, the authors describe two patients with renal cell cancer in whom grade 4 neutropenia and grade 3 hemolytic anemia developed, respectively, during treatment with twice-weekly intravenous recombinant human interleukin-12 (rhIL-12) during a phase 1 trial. The severe neutropenia was associated with bone marrow agranulocytosis and a preponderance of large granular lymphocytes in the peripheral blood, whereas the hemolytic anemia was negative for the Coombs test and associated with splenomegaly. The agranulocytosis and hemolytic anemia persisted after the rhIL-12 was stopped, but both subsequently responded to treatment with cyclophosphamide. steroids, or both. These findings indicate that rhIL-12 can induce unique hematologic toxic effects that can be reversed with immunosuppressive drugs.