EX VIVO P-GP Inhibition Model

There is a strong evolutionary conservation between the insect blood brain barrier (BBB) and the mammalian BBB. This includes functional chemoprotective parallels between the human MDR1/P-gp transporter system and the insect Mdr65 transporter system. N2MO has developed an ex vivo model based on the locust brain for analyzing physiological properties of the BBB in the intact brain of locusts (Schistocerca Gregaria).

The model can be used to screen small-molecule compounds for permeability and to identify P-glycoprotein (Pgp) interactions of drug leads. The model can replace standard in vitro screen models in the early drug development screen cascade and supplement vertebrate models of BBB permeability.

In the ex vivo Pgp Locust BBB model the influence of Pgp inhibition on compound permeability is studied at constant test compound exposure of 1-10 μM and is independent of degrading enzymes, elimination and plasma protein binding. Data quality is high and the study outcome is always judged towards the response of an internal positive control.

The degree of active efflux can be quantified in the ex vivo Locust BBB model since a Pgp homolog (MDR65) is expressed in the insect brain barrier. This is exemplified with a study where locust brains were exposed to various concentrations of carbamazepine (a non Pgp CNS drug) and quinidine (a well known Pgp substrate) in the presence and absence of the prototypical Pgp inhibitor verapamil.

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“The ex vivo model allows identification and classification of Pgp transporter substrates and is a robust insect-based efflux assay able to categorize NCE as potential Pgp substrates and their interaction affinities.”

Key model advantages:

  • The locust blood brain barrier is the only ex vivo model of BBB permeability 
that is based on an intact natural biological brain barrier that retains its 
biological integrity and control functions during the test procedure similar to
 vertebrate in vivo BBB models.
  • The ex vivo Pgp Locust BBB permeability model can be used to identify
 Pgp substrates and to rank BBB permeability in both single and multiple
 dosing regimens.
  • Pgp identification by pharmacological inhibition of Pgp in the ex vivo Pgp
 BBB permeability model avoids the complexities of multiple transporters by 
focusing specifically on effect of Pgp efflux inhibition.
  • The Pgp Locust BBB permeability model permits test on ready made 
stock solutions.
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