Comparison of Ki and IC50 Values for Prototypical Inhibitors of ABC Transporters P-gp and BCRP

Scientific Resources Comparison of Ki and IC50 Values for Prototypical Inhibitors of ABC Transporters P-gp and BCRP

• Published on April 20, 2015
• Enzyme Inhibition
• Test Systems & Methods
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Full Title

Comparison of Ki and IC50 Values for Prototypical Inhibitors of ABC Transporters P-gp and BCRP

Abstract

K_i values were determined for prototypical inhibitors of ABC transporters P-gp and BCRP with an experimental design incorporating multiple substrate and inhibitor concentrations in vesicles. The EMA’s Guideline on the Investigation of Drug Interactions (2012) recommends K_i values for evaluating transporter inhibition. The use of IC₅₀ values is recommended only when Kideterminations are not possible. Although K_i values have been reported for inhibitors of various transporters, the methodology differs between labs and oftentimes relies on evaluation of a single probe substrate concentration combined with mathematical extrapolation.

These experiments were conducted to compare IC₅₀ and K_i values determined in transporter-expressing membrane vesicles.

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