ASCO--Both forms of recombinant human platelet growth factor currently under study have been shown to enhance platelet recovery after myelosup-pressive chemotherapy without serious side effects. The first four clinical trials of the two products--pegylated megakaryocyte growth and development factor (MGDF, Amgen), which is linked to polyethylene glycol to improve its stability and half-life; and thrombopoietin (rhTPO, Genentech)--were presented at an ASCO scientific symposium.
Two randomized, double-blind, placebo-controlled phase I/II trials, one in the United States and one in Australia, showed the safety and efficacy of MGDF. In the US trial, conducted at Emory, UCLA, and Duke, MGDF (at six dose levels ranging from .03 to 5 mcg/kg/day) proved safe and well tolerated when given after carboplatin(Drug information on carboplatin) (Paraplatin) and paclitaxel(Drug information on paclitaxel) (Taxol) therapy. The 53 patients had previously untreated stage III or IV non-small-cell lung cancer.
Administration of multiple injections of MGDF after chemotherapy resulted in significantly faster recovery of platelet counts (median, 14 days vs more than 21 days with placebo), said Michael Fanucchi, MD, associate professor of medicine, Emory University.
Post-chemotherapy platelet nadirs also were 70% higher in patients treated with MGDF than in those given placebo (median, 189,000 vs 110,000/mm³).
In the Australian trial, patients with previously treated advanced cancers were given placebo or MGDF together with G-CSF (Neupogen) either before (17 patients) or after (41 patients) therapy with carboplatin plus cyclophosphamide(Drug information on cyclophosphamide).
MGDF enhanced platelet recovery in a dose-dependent manner, said Dr. G. Begley, of the Centre for Developmental Cancer Therapeutics, Parkville, Victoria. Platelet counts also nadired earlier with MGDF than with placebo. Importantly, MGDF, in doses up to 5 mcg/kg/day, was well tolerated when given with G-CSF.