Michael G. Kelly

Identification and characterization of novel TRPV4 modulators.

TRPV4, a close relative of the vanilloid receptor TRPV1, is activated by diverse modalities such as endogenous lipid ligands, hypotonicity, protein kinases and, possibly, mechanical inputs. While its multiple roles in vivo are being explored with KO mice and selective agonists, there is a dearth of selective antagonists available to examine TRPV4 function. Herein we detail the use of a focused library of commercial compounds in order to identify RN-1747 and RN-1734, a pair of structurally related small molecules endowed with TRPV4 agonist and antagonist properties, respectively. Their activities against human, rat and mouse TRPV4 were characterized using electrophysiology and intracellular calcium influx. Significantly, antagonist RN-1734 was observed to completely inhibit both ligand- and hypotonicity-activated TRPV4. In addition, RN-1734 was found to be selective for TRPV4 in a TRP selectivity panel including TRPV1, TRPV3 and TRPM8, and could thus be a valuable pharmacological probe for TRPV4 studies.

Oxime derivatives related to AP18: Agonists and antagonists of the TRPA1 receptor

AP18 1 was recently disclosed as an antagonist of the TRPA1 receptor by the research group of Patapoutian. However, no detailed structure-activity relationships around 1 have been disclosed. Thus, a small number of oximes related to AP18 were examined in order to characterize the determinants of TRPA1 activity. Congeners of AP18 were found to possess both agonist and antagonist activity, suggesting that AP18 may behave as a covalent antagonist of the TRPA1 ion-channel.

Identification of orally-bioavailable antagonists of the TRPV4 ion-channel.

Antagonists of the TRPV4 receptor were identified using a focused screen, followed by a limited optimization program. The leading compounds obtained from this exercise, RN-1665 23 and RN-9893 26, showed moderate oral bioavailability when dosed to rats. The lead molecule, RN-9893 26, inhibited human, rat and murine variants of TRPV4, and showed excellent selectivity over related TRP receptors, such as TRPV1, TRPV3 and TRPM8. The overall profile for RN-9893 may permit its use as a proof-of-concept probe for in vivo applications.

2-Amino-5-arylbenzoxazole derivatives as potent inhibitors of fatty acid amide hydrolase (FAAH)

2,5-Disubstituted benzoxazole derivatives were evaluated for their ability to inhibit hFAAH. Structure–activity studies indicated that an isoindoline group at the 2-position of the benzoxazole ring gave rise to particularly potent inhibitors. Further refinement resulted in compounds, such as 50, with low nanomolar potencies against hFAAH. Preliminary biochemical experiments revealed that model benzoxazole FAAH inhibitors inhibited the enzyme in a manner consistent with a reversible mechanism. Additionally, the species dependency of FAAH inhibition was measured. Of the species tested, inhibition of rabbit FAAH, but not rat and guinea pig FAAH, appeared to show close alignment to human FAAH. These results may suggest similarities between the active sites of the FAAH enzyme for these two species, and may also suggest that rabbit could be a viable species with which to conduct preclinical testing with benzoxazole FAAH inhibitors.

Mining biologically-active molecules for inhibitors of fatty acid amide hydrolase (FAAH): Identification of phenmedipham and amperozide as FAAH inhibitors

The screening of known medicinal agents against new biological targets has been shown to be a valuable approach for revealing new pharmacology of marketed compounds. Recently, carbamate, urea and ketone inhibitors of fatty acid amide hydrolase (FAAH) have been described as promising treatments for pain, anxiety, depression and other CNS-related conditions. In order to find novel FAAH inhibitors, a focused screen of molecules containing potentially reactive moieties or having in vivo effects that are possibly relevant to the biology of FAAH was conducted. These studies revealed phenmedipham 13 and amperozide 14 to be inhibitors of human FAAH, with an IC(50) of 377 nM and 1.34 microM, respectively.

Discovery of potent, non-carbonyl inhibitors of fatty acid amide hydrolase (FAAH)

Fatty acid amide hydrolase (FAAH) inhibition is a promising target for the treatment of pain, anxiety and depression. The vast majority of FAAH inhibitors contain an electrophilic moiety and are known to react covalently with the enzyme. Herein we present the discovery of potent inhibitors, such as RN-450 29, which are based upon a novel tetrahydropyridopyridine scaffold lacking an obvious electrophilic site, and which appear to inhibit FAAH in a reversible and non-covalent manner.