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Inhibition studies

To determine the inhibitory potential of a test item the intracellular accumulation of the labeled probe substrate is performed in the absence or presence of increasing concentrations of the test item.
Experience has shown that a two-step procedure is recommendable:

First Step

Two point Inhibition: Inhibition of transporter-mediated uptake of a probe substrate by two different concentrations of a test item.


Two point Inhibition

Second Step
Determination of IC50 value: Concentration dependent inhibition of a probe substrate by a test item and determination of the half-maximal inhibition value (IC50). .

IC50 determination


Alternative Second Step
Determination of the inhibition character (Ki value): Dixon Plot analysis to determine competitive or non-competitive inhibition.




Drug transporter assays

  Study design

  Assay performance

  Inhibition studies

  Substrate studies

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37075 Göttingen
Tel : +49 551 309 66440
E-mail: PortaCellTec

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New validated products:

  • mNtcp
  • mOct1


3rd German Pharm-Tox Summit
Göttingen, Germany
26 February - 1 March 2018

Saarbrücken, Germany
8 March 2018


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Virginia, USA
16 - 18 April 2018


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Bad Herrenalb, Germany
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Greifswald, Germany
October 2018


Guidance for Industry (FDA and EMA)