Preliminary in vitro assessment of pharmacokinetic drug-drug interactions of EST64401 and EST64514, two sigma-1 receptor antagonists.

EST64401 and EST64514 are two selective sigma-1 receptor ligands that showed a good profile in a lead optimization process for oral pain treatment. Their potential for pharmacokinetic-based drug-drug interactions was assessed to anticipate clinical interactions.Both compounds showed a low potential for CYP inhibition with percentages of inhibition <50% at 1 µM in recombinant human CYPs (CYP1A2, 2C9, 2C19, 2D6 and 3A4) and IC50 ≥75 µM for CYP3A4 and 2D6 in human liver microsomes.No CYP induction was observed for CYP1A2, 2B6 and 3A4 at concentrations ≤25 µM (EST64401) or ≤50 µM (EST64514) in human hepatocytes using as endpoints CYP activities and mRNA levels.More than one enzyme participated in compound metabolism. The main enzymes involved were CYP3A4 for EST64401 and CYP2D6 besides CYP3A4 for EST64514.Neither EST64401 nor EST64514 seemed to be substrates of P-gp or BCRP in Caco-2 cells (efflux ratio ≤2). Transporter inhibition was observed at concentrations ≥20 µM; EST64401 only inhibiting P-gp at higher concentrations (≥125 µM).Preliminary in vitro interaction studies suggest a similar profile for EST64401 and EST64514. Therefore, other properties will have to be considered for compound differentiation and selection for further development.

Preliminary in Vitro Assessment of the Potential of EST64454, a Sigma-1 Receptor Antagonist, for Pharmacokinetic Drug-Drug Interactions.

EST64454 is a selective sigma-1 receptor ligand intended for orally administered pain treatment that showed a promising profile in the lead optimization process. As part of the preliminary compound profiling, the potential for future drug-drug interactions was explored in vitro. Both direct and time-dependent CYP inhibition for CYP1A2, 2C9, 2C19, 2D6 and 3A4 was studied in human liver microsomes. EST64454 showed a low potential for CYP inhibition (IC50 between 100 and 1000 µM) and as time-dependent inhibitor (IC50 shift mainly around 1). CYP induction studies with HepaRG™ cells revealed no CYP induction at concentrations ≤50 µM, as shown by the CYP1A2, 3A4 and 2B6 activities measured. Reaction phenotyping was assessed after incubation with recombinant human enzymes. Although a very low metabolism was observed, several enzymes catalyzed the formation of metabolites, including CYP3A4, 2C19 and flavin monooxygenases (FMO) 1 and 3. EST64454 was not a P-glycoprotein (P-gp) substrate and was highly permeable in Caco-2 cells. P-gp inhibition was only observed at 200 µM, the highest concentration studied. Preliminary studies suggest that neither CYP nor P-gp interaction of EST64454 would be of any concern for further development. At later stages, the interaction kinetics and the clinical relevance of these findings will be thoroughly evaluated.