TPO and Thrombocytopenia: Although PEG-rHuMGDF initially showed promise in early clinical trials by being safe and effective at increasing platelet levels, the development of neutralizing antibodies and severe thrombocytopenia in around 8% of exposed patients due to its homology with the native Tpo led to discontinuation of trails in the United States.37,38 On the other side, similar adverse effects were not encountered with the use of rhTpo.