Elevation of peripheral platelet counts in thrombocytopenic HIV-infected chimpanzees by PEG-rHuMGDF. Three doses of PEG-rHuMGDF (25 μg/kg on days 1, 4, and 7) produced peripheral platelet counts that peaked at 599 ± 260 × 10³platelets/μL (P = .02 compared with pretreatment value of 64 ± 19) 3 days after discontinuing therapy. The timing of the 3 doses of PEG-rHuMGDF is indicated by the downward arrows. Platelet counts returned to baseline thrombocytopenic levels during the subsequent 2 weeks.