EVALUATION OF THE POTENCY AND SELECTIVITY OF THE NOVEL FAAH INHIBITOR BIA 10‐2474 IN COMPARISON WITH PF‐04457845 AND JNJ‐42165279

In January 2016 one person died and others suffered adverse neurological effects during a Phase I clinical trial of the fatty acid amide hydrolase (FAAH) inhibitor BIA 10‐2474. We have compared the potency and selectivity of BIA 10‐2474 with two other mechanism‐based FAAH inhibitors PF‐04457845 and JNJ‐42165279 which appeared safe in human testing. In whole cells, BIA 10‐2474 inhibited FAAH with an IC 50 of 74.4 and 18 nM after 1h and 24h incubation respectively. This compares with 26.2 and 41.5 nM for JNJ‐42165279 at 1 and 24h and 4.3 nm for PF‐04457845 at 1h. All three compounds were characterised as irreversible FAAH inhibitors. Interestingly, BIA 10‐2474 and JNJ‐42165279 were more potent FAAH inhibitors in whole cells as compared to a membrane preparation (4–6 fold more active) when tested after 1h incubation whereas PF‐04457845 was equipotent in the two models (4.3 and 2.0 nM respectively). Neither BIA 10‐2474 nor JNJ‐42165279 accumulated inside the cells. Activity based protein profiling in vitro identified only ABHD6 as an off‐target for BIA 10‐2474 with no activity against other rat brain serine hydrolase enzymes up to 100 mM. In contrast PF‐04457845 and JNJ‐42165279 both interacted with ABHD11. BIA 10‐2474 had no significant activity against 220 other human off‐targets in binding and enzyme studies up to 50 μM. In contrast, PF‐04457845 showed significant activity (>50% inhibition) at 37 sites at 50 μM, including cannabinoid receptors, serotonin receptors, and several ion channels. In vivo, oral administration of BIA 10‐2474 inhibited rat brain and liver FAAH with ED 50 s of 13.5 and 6.2 mg/kg PO respectively and increased brain levels of fatty acid amides over the same dose range. This compares with 4.3 and 2.0 mg/kg PO for PF‐04457845 and 12.5 and 3.7 mg/kg PO for JNJ‐42165279. Exposure levels of BIA 10‐2474 in plasma and brain were consistent with the potency identified in whole cells and there was no evidence for accumulation in the brain of either BIA 10‐2474 nor its main metabolites following repeated administration. These data suggest that the in situ and in vivo potency and the selectivity of BIA 10‐2474 is comparable to other clinically tested FAAH inhibitors. These data also demonstrate that there is no unusual accumulation of BIA 10‐2474 or its metabolites in cells nor in the CNS. In conclusion, these results fail to identify an off‐target activity or a mechanism that could explain the clinical trial accident. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .