Effects of PEG-rHuMGDF on posthepsulfam hematopoietic regeneration. Daily subcutaneous injections of PEG-rHuMGDF (2.5 μg/kg/d), beginning 1 day after hepsulfam administration and continuing for 21 days, produced a biphasic increase in the peripheral platelet counts at or above prechemotherapy values (left). PEG-rHuMGDF dosing after hepsulfam chemotherapy shortened the duration of neutropenia from 22 to 12 days (P = .01), although the neutropenic nadir was not significantly changed (right). The open symbols depict the counts for untreated hepsulfam controls, and the closed symbols designate counts in PEG-rHuMGDF-treated hepsulfam animals.