Megakaryocyte growth and development factor accelerates platelet recovery in peripheral blood progenitor cell...

We have investigated the potential of PEGylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), a molecule related to thrombopoietin (mpl ligand or TPO) in minimizing the thrombocytopenia associated with hematopoietic ablation and peripheral blood progenitor cell (PBPC) transplant. Irradiated mice that received PBPC mobilized by PEG-rHuMGDF or granulocyte colony-stimulating factor (G-CSF) had a reduced number of thrombocytopenic days with platelets below 100 x 10(6) per mL of blood. Recipients of unmobilized PBPC had a 9 day thrombocytopenic phase which was shortened to 7 days if they were given granulocyte-macrophage colony-stimulating factor (GM-CSF)-mobilized PBPC. This was further reduced to 2 or 3 days of thrombocytopenia in recipients of G-CSF- or PEG-MGDF-mobilized PBPC. Despite our observation that PEG-rHuMGDF is a relatively modest stimulator of the mobilization of myeloid progenitors to the blood, MGDF-mobilized PBPC do effect accelerated recovery of platelets after transplantation. However, the most effective use of PEG-rHuMGDF is when it is given during the recovery phase after PBPC transplantation to hematopoietically ablated mice. Posttransplant treatment with PEG-rHuMGDF reduces thrombocytopenia to a single day or less, in recipients of most types of PBPC. Mice that were treated during the first 2 weeks after PBPC transplant with PEG-rHuMGDF had 1 thrombocytopenic day compared to 9 days in carrier-treated recipients of unmobilized PBPC and 2 to 3 days in carrier-treated recipients of the optimally mobilized PBPC from G-CSF or G-CSF/PEG-rHuMGDF treated donors. In groups where PEG-rHuMGDF was included in the mobilization protocol and used to treat recipients as well thrombocytopenia was effectively eliminated. These data show that PEG-rHuMGDF is a highly effective agent in eliminating the thrombocytopenia associated with PBPC transplantation.