Prediction of human pharmacokinetics of typical compounds by a physiologically based method using chimeric mice with humanized liver

1. In this study, total body clearance (CL_t), volume of distribution at steady state (V_ss) and plasma concentration–time profiles in humans of model compounds were predicted using chimeric mice with humanized livers.

2. On the basis of assumption that unbound intrinsic clearance (CL_Uint) per liver weight in chimeric mice was equal to those in humans, CL_t were predicted by substituting human liver blood flow and liver weights in well-stirred model. V_ss were predicted by Rodgers equation using scaling factors of tissue-plasma concentration ratios (SF_Kp) in chimeric mice estimated from a difference between the observed and predicted V_ss. These physiological approaches showed high prediction accuracy for CL_t and V_ss values in humans.

3. We compared the predictability of CL_t and V_ss determined by the physiologically based predictive approach using chimeric mice with those from predictive methods reported by Pharmaceutical Research Manufacturers of America. The physiological approach using chimeric mice indicated the best prediction accuracy in each predictive method.

4. Simulation of human plasma concentration–time profiles were generally successful with physiologically based pharmacokinetic (PBPK) model incorporating CL_Uint and SF_Kp obtained from chimeric mice.

5. Combined application of chimeric mice and PBPK modeling is effective for prediction of human PK in various compounds.

     

Monoclonal Antibody Usage Strategies for Natural Products in Traditional Chinese Medicine

Monoclonal antibodies (MAbs) against natural products with low?molecular weights have become an important tool when combined with other analytical systems. Eastern blotting involves a typical staining system wherein, for example, glycosides can be blotted to a membrane and cross?linked and stained using MAbs. An immunoaffinity column combined with a monoclonal antibody allows a one?step purification of hapten compounds or preparation of a knockout extract that removes only the target hapten molecules from a crude extract. Here, we discuss the application of these extracts. Single?chain variable fragment (scFv) proteins have led to novel assay systems such as fluobodies or antibodies coupled with green fluorescent protein for natural products. A typical novel application of a scFv gene would be in the context of plant breeding; this is designated “missile?type” molecular breeding, intended to increase hapten molecule concentrations in transgenic plants