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Endogenous
thrombopoietin (TPO) is a cytokine which promotes
platelet production by regulating growth and maturation
of megakaryocztes, therefore increases the platelet
level in the circulation. Nowadays the recombinant human
thrombopoietin is preferred as agent of therapy for
Thrombocytopenic purpura and radiation-induced or
chemical-induced thrombocytopenia.
rhTPO is a full-length molecule identical to natural
form. It is a single chain, composed of 353 amino acids
and including 21 amino acids in the signal peptide.
rhTPO is glycoprotein, its molecular size is 70-120KD.
The development of rhTPO was initiated in 1995 .The
process of development and pre-clinical studies were
completed at the end of 1998. The application for
clinical trails was approved as new drug of Class I by
State Drug and Food Administration (SFDA) of China In
1999. The whole clinical study (Phase I, II and III) has
been already completed until May, 2003.
The human cDNA containing TPO ORF was cloned from fetal
lung cDNA library. rhTPO was expressed in Chinese
Hamster Ovary cell Line (CHO). Fermentation was carried
out in a large-scale, continuous perfusion cell culture
system using packed-bed bioreactors (Celligen Plus). To
ensure high purity, rhTPO was purified by multi-step
method. The overall recovery rate was 16-25%. The
specific activity of rhTPO in bulk was 280,000 IU/mg.
Impurity: Residual DNA (<100pg/50μg), Endotoxin
(<10EU/50μg). Finally rhTPO was formulated with
human serum albumin (HSA) and other additives in the
environment of pH: 6.4-7.4. Aqua dose form, 50μg/Vial,
stored at 2-8 Celsius degree.
The clinical study demonstrated that rhTPO was well
tolerated by patients. It could accelerate the platelet
recovery after radiotherapy or chemotherapy, decrease
the requirement for platelet transfusion significantly.
rhTPO was safe and effective in the treatment of
radiation-induced or chemical-induced Thrombocytopenia.
There was no influence of rhTPO on HB, WBC, the function
of kidney or liver, no influence on platelet form,
platelet aggregation function or coagulation. Only a few
slight adverse events occurred during clinical study.
Low titer of antibody was observed in a few patients,
but it didn't have neutralizing ability.
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