help mAb - monocloanal antibodies (Dec/24/2006 )

hi
any one knows about the reason for the large quantity of mAb for the injection to cancer patients, when compared to the therapeutic products.
for eg., anti CD20 monoclonal antibody is given as 50mg or 100mg or 150 mg according to the weight of the personand severity of the cancer, but the therapeutic drug such as EPO, GCSF are given to patient at pico gram or micro gram level. On what basis, the dosage level of drugs is administred ?.
please help with supportive literature.

thanks in advances

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The difference could be due to MW and mechanism of action. Ig G is considerably larger than both cytokines. In terms mechanism of action, EPO and GMCSF are strong stimuli whose actions are amplified through down stream signaling pathways after binding to their receptors, while Ab blocks target receptor molecules to prevent native ligands from binding to the receptors, its affinity towards receptors may not beat the native ligands, therefore higher doses are needed to achieve that. The effective dosages are usually predetermined in animal studies, then confirmed in clinical trials.

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in addition to genehunter-1´s answer, indeed, mAb and hormones/messengers work in totally different ways; another reason for relative high levels of mAb administered is that not all reach there target (mostly receptors) but some are absorbed unspecifically; this must be overcome by higher concentrations

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