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inhibition with (+)-1, (À)-ent-1 (57) and ( )-rac-1 (9) consistent with
mechanism-based inhibition. All other compounds tested in this series at
multiple FAAH incubation times showed similar behaviour (Unpublished
results).
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3.3 L/kg. The low oral exposure was speculated to be due to first
pass metabolism in the liver and this was investigated further by
comparing sampling from the hepatic portal vein (HPV) versus
the vena cava (VC). The HPV plasma exposure was 17-fold greater
than for the VC confirming that the low bioavailability was due to
first pass metabolism. Due to the low bioavailability, we decided to
investigate the in vivo FAAH inhibitory properties of 1 using intra-
venous (IV) dosing for proof-of-concept. 1 was dosed to male rats
at 0.3, 1 and 3 mg/kg IV. Baseline levels of AEA were raised for bio-
analysis with a 20 mg/kg intraperitoneal dose 30 min post-1 and
samples were taken for analysis 30 min later. 1 exhibited FAAH
inhibition by raising brain AEA levels in a dose-dependent manner.
Fold-changes versus vehicle were calculated with a maximum
change of 5.1-fold at 3 mg/kg 1 (Table 5).
In conclusion, we have described our efforts to improve the phar-
macological profile of our FAAH inhibitor VER-156084 (1). The unfa-
vourable disconnection between human and rat FAAH inhibition
was maintained throughout the series, and improvements in physi-
cochemical properties and metabolic turnover could not be com-
bined with significant potency improvements. Molecular docking
studies were unable to distinguish between two possible binding
modes for these compounds with certainty. We have demonstrated
in vivo proof-of-concept of FAAH inhibition in a dose-dependant
manner with VER-156084 (1) following IV dosing in an ananda-
mide-loading study, but discontinued development of this com-
pound in favour of alternative chemotypes with improved oral
bioavailability which will be described in future communications.
Acknowledgment
The authors are indebted to Dr. Hans Meissner for helpful dis-
cussions during the preparation of this manuscript.
28. Davidson, J. E. P., Bentley, J. M., Dawson, C. E., Mansell, H. L., Pratt, R. M., Ruston,
V. J., Roffey, J. R. A., Pither, A. L., and Harrison, K. Azetidinecarboxamide
derivatives and their use in the treatment of cb1 receptor mediated disorders.
[WO2004/96794]. 2004.
Supplementary data
29. Roughley, S. D.; Hart, T. Tet. Lett. 2010, 51, 5191.
30. Full synthetic procedures for all compounds are provided in the Supplementary
data.
31. The assay was performed using purified rat or human FAAH enzyme, following
the procedure described in: Ramarao, M. K.; Murphy, E. A.; Shen, M. W. H.;
Wang, Y.; Bushell, K. N.; Huang, N.; Pan, N.; Williams, C.; Clark, J. D. Anal.
Biochem. 2005, 343, 143.
Supplementary data (full synthetic procedures for all com-
pounds are provided, along with MAGL assay details and additional
in vivo pharmacokinetic data) associated with this article can be
32. Bracey, M. H.; Hanson, M. A.; Masuda, K. R.; Stevens, R. C.; Cravatt, B. F. Science
2002, 298, 1793. PDB ID: 1MT5.
33. Glide. [5.7]. 2011. New York, NY, Schrödinger, LLC.
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