OC144-093, a novel P glycoprotein inhibitor for the enhancement of anti-epileptic therapy.

Inhibitors of P gLycoprotein (Pgp) may be useful for the enhancement of blood-brain barrier penetration of anti-epileptic drugs (AEDs). Due to polypharmacy and the need for chronic treatment, Pgp inhibitors used in epilepsy should be highly specific and non-toxic. In particular, it may be essential to use compounds that produce minimal inhibition of enzymes involved in metabolism of AEDs and other drugs used by epilepsy patients. OC144-093 is a novel substituted diarylimidazole generated using the OntoBLOCK system, a solid-phase combinatorial chemistry technology, in combination with high-throughput cell-based screening. The compound is an extremely potent inhibitor of Pgp-mediated multidrug resistance (MDR) in cancer with an average FC50 of 32 nM, but does not inhibit multidrug resistance-associated protein (MRP1). OC144-093 is the least non-specifically toxic Pgp inhibitor described to date, with an average cytostatic IC50 of >60 microM in 15 cell types. It is not metabolized by cytochrome P450s CYP3A4, 2C8 or 2C9 enzymes involved in AED metabolism. OC144-093 does not produce a pharmacokinetic (PK) interaction with paclitaxel and has exhibited an excellent PK and safety profile in phase I clinical trials. Our results suggest that OC144-093 may represent an ideal candidate for use in enhancement of AED blood-brain barrier penetration.