Diabetes Research Today is a free monthly online journal that collates and summarizes the latest research about Diabetes, including details on insulin, type i, type ii, diet, treatment, prevention. | ||||||||
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Establishment of correlation between in vitro enzyme binding potency and in vivo pharmacological activity: application to liver glycogen phosphorylase a inhibitors.Yu LJ, Chen Y, Treadway JL, McPherson RK, McCoid SC, Gibbs EM, Hoover DJ Department of Pharmacokinetics, Groton Laboratories, Pfizer Global Research & Development, Pfizer Inc., Groton, Connecticut, USA. li.yu@mpi.com In drug discovery, establishing a correlation between in vitro potency and in vivo activity is critical for the validation of the selected target and for developing confidence in the in vitro screening strategy. The present study developed a competition equilibrium dialysis assay using a 96-well dialysis technique to determine the intrinsic Kd for 13 inhibitors of human liver glycogen phosphorylase a (GPa) in the presence of liver homogenate to mimic the physiological environment. The results provided evidence that binding of an inhibitor to GPa was affected by extra cofactors present in the liver homogenate. A good correlation was demonstrated between the in vitro Kd determined under liver homogenate environment and free liver concentration of an inhibitor at the minimum efficacious dose in diabetic ob/ob mice. This study revealed important elements (such as endogenous cofactors missing from the in vitro assay and free concentration at the target tissue) that contributed to a better understanding of the linkage between in vitro and in vivo activity. The approach developed here may be applied to many drugs in pharmacology studies in which the correlation between in vitro and in vivo activities for the target tissue (such as solid tumors, brain, and liver) is critical. Published 19 May 2006 in J Pharmacol Exp Ther, 317(3): 1230-7.
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