Potent multitarget FAAH-COX inhibitors: Design and structure-activity relationship studies

Non-steroidal anti-inflammatory drugs (NSAIDs) exert their pharmacological effects by inhibiting cyclooxygenase (COX)-1 and COX-2. Though widely prescribed for pain and inflammation, these agents have limited utility in chronic diseases due to serious mechanism-based adverse events such as gastrointestinal damage. Concomitant blockade of fatty acid amide hydrolase (FAAH) enhances the therapeutic effects of the NSAIDs while attenuating their propensity to cause gastrointestinal injury. This favorable interaction is attributed to the accumulation of protective FAAH substrates, such as the endocannabinoid anandamide, and suggests that agents simultaneously targeting COX and FAAH might provide an innovative strategy to combat pain and inflammation with reduced side effects. Here, we describe the rational design and structure-active relationship (SAR) properties of the first class of potent multitarget FAAH-COX inhibitors. A focused SAR exploration around the prototype 10r (ARN2508) led to the identification of achiral (18b) as well as racemic (29a-c and 29e) analogs. Absolute configurational assignment and pharmacological evaluation of single enantiomers of 10r are also presented. (S)-(+)-10r is the first highly potent and selective chiral inhibitor of FAAH-COX with marked in vivo activity, and represents a promising lead to discover novel analgesics and anti-inflammatory drugs.