Effects of combining PEG-rHuMGDF and rHu-GCSF on hematopoietic regeneration. Administering PEG-rHuMGDF (2.5 μg/kg/d, or 10 μg/kg/d) concurrently with rHu-GCSF (10 μg/kg/d) increased platelet counts in a dose-dependent fashion (left) compared with hepsulfam alone controls (P < .03 in both cases), but significantly less than the peak platelet count of 856 ± 594 × 10⁹/L for posthepsulfam PEG-rHuMGDF (2.5 μg/kg/d) alone (P < .02 in both cases). Combination PEG-rHuMGDF and rHu-GCSF shortened the period of neutropenia (<1 × 10⁹ neutrophils/L) to 4 days (right); (P = .001 v hepsulfam alone controls) without significantly increasing the nadir (P < .2 for hepsulfam only controls). The (○) depict the counts for untreated hepsulfam controls. The (▴) represent counts in hepsulfam animals concurrently receiving 2.5 μg/kg PEG-rHuMGDF and 10 μg/kg rHu-GCSF. The (•) designate counts in hepsulfam animals concurrently receiving 10 μg/kg PEG-rHuMGDF and 10 μg/kg rHu-GCSF.