The rhGM-CSF-EPO hybrid protein MEN 11300 induces anti-EPO antibodies and severe anaemia in rhesus monkeys |
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Authors: | Coscarella A Liddi R Di Loreto M Bach S Faiella A van der Meide P H Mele A De Santis R |
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Institution: | Menarini Ricerche S.p.A., Department of Biotechnology Research, Via Tito Speri 10-00040 Pomezia, Rome, Italy. |
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Abstract: | A recombinant human GM-CSF-EPO hybrid protein named MEN 11300 was administered biweekly for a total of 6 weeks to rhesus monkeys in order to evaluate its pharmacokinetic behaviour, tolerability and immunogenicity. In this primate species a strong antibody response was induced which neutralized the in vitro biological activity of human EPO while no antibody response could be detected against human GM-CSF. A severe drop in reticulocyte counts at approximately 2 weeks after initiation of treatment was followed by a dramatic decrease in the number of erythrocytes. No effects were observed on GM-CSF-dependent hematopoietic lineages and the clinical chemistry analyses did not reveal signs of general toxicity. Reticulocyte and erythrocyte counts started to recover 3-4 weeks after discontinuation of treatment in concert with a decline in anti-EPO antibody titres. Nevertheless, cell numbers remained below basal levels up to 50 days after the last MEN 11300 administration. Haematological impairment indicates that the administration to non-human primate of human EPO fused to human GM-CSF, induces neutralizing autoantibodies to the self EPO. Present data do not allow prediction of the immunogenic potential of the fusion protein in humans and a dose-escalating phase I study should be addressed to investigate the safety of the product. |
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Keywords: | GM-CSF fusion protein/immunogenicity/primate model |
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