In-vivo effect of interleukin 3 and erythropoietin, either alone or in combination, on the hematopoietic toxicity associated with zidovudine.

We studied the effect of erythropoietin (EPO) and interleukin 3 (IL-3), either alone or in combination, on the hematopoietic toxicity associated with zidovudine in vivo, as determined by peripheral blood indices, and assay of hematopoietic progenitors, i.e. erythroid (CFU-E/BFU-E), myeloid (CFU-GM) and megakaryocyte (CFU-Meg) from bone marrow and spleen. Previous studies from this laboratory have established that dose escalation of zidovudine to normal mice induced a dose-dependent decrease in hematocrit, white blood cells and platelets with altered populations of marrow and splenic erythroid, myeloid and megakaryocyte progenitors. Daily administration of EPO (50 U/animal, i.p.) and/or IL-3 (5 U/animal, i.p.) was associated with altered peripheral blood indices and progenitor cells. In general, use of EPO and IL-3 alone reduced zidovudine-induced toxicity, notably in erythropoiesis; however, combination EPO/IL-3 was associated with enhanced toxicity with an observed rebound only with the use of < 2.5 mg/ml drug; 2.5 mg/ml drug in the presence of combination EPO/IL-3 accelerated zidovudine-erythroid toxicity. A similar response was noted with circulating platelets and megakaryocyte progenitors. Use of EPO or IL-3, either alone or in combination, failed to reverse zidovudine-induced neutropenia. These studies demonstrate that use of EPO or IL-3, either alone or in combination may serve as an effective adjuvant therapy to modulate the erythroid toxicity associated with lower doses of zidovudine; however, this cytokine therapy was ineffective modulating zidovudine-induced myelosuppression when used in vivo. A reversal in zidovudine-induced myeloid toxicity, therefore may require the use of a myelopoiesis inducing cytokine.