2690
S. D. Linton et al. / Bioorg. Med. Chem. Lett. 14 (2004) 2685–2691
between the carbonyl of Arg 207 and the distal oxamyl
ꢀ
NH was noted, as well as a 2.7 A interaction between the
References and notes
1. For nomenclature of the caspase family, see: (a) Alnemri,
E. S.; Livingston, D. J.; Nicholson, D. W.; Salvesen, G.;
Thornberry, N. A.; Wong, W. W.; Yuan, J.-Y. Cell 1996,
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2. (a) Ellis, R. E.; Yuan, J.; Horvitz, H. R. Ann. Rev. Cell
Biol. 1991, 7, 663; (b) Reed, J. C.; Tomaselli, K. J. Curr.
Opin. Biotech. 2000, 11, 586.
amide hydrogen of Arg 207 and the proximal oxamyl
carbonyl. It was difficult to propose defined interactions
between the phenyl ring of substituted phenyl oxamide
analogs and residues in the P4 pocket, such as His 342
and Arg 383. This is not surprising given that the P4
pocket of caspase 1 is not a very well defined binding
pocket, generally picking up hydrophobic interactions.
This lack of defined phenyl interactions is borne out in
the methyl oxamide (36). Although not as potent as the
phenyl oxamide (41), or as the benzyl oxamide (58), the
methyl oxamide is in the same range and possesses
similar cellular activity. This is further reinforced by the
loss of activity seen with the methylated 1-naphthyl
oxamide (50). New analogues with more diverse sub-
stitution of the phenyl ring should prove interesting.
3. (a) Talanian, R. V.; Brady, K. D.; Cryns, V. L. J. Med.
Chem. 2000, 43, 3351; (b) Lee, D.; Long, S. A.; Murray, J.
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It was noted that the potency of caspase inhibition and
cellular activity do not correlate well. Lack of potency in
these cellular assays with analogues having good caspase
activity could be attributable to a number of factors,
ranging from protein binding, cell permeability to the
compounds stability in a 24 h assay run at 37 °C. Other
reasons for the poor correlation between overall caspase
inhibition and the cell assays are that some caspases are
more relevant to particular cell assays than others. For
example, the monocyte and THP-1 assays are solely
dependent on caspase 1. On the other hand, although
caspase 8 is highly relevant to the Jurkat assay, it is not
the only caspase involved. When evaluating in vitro data
of this type, it is best to look at general trends.
Based on in vitro activities (namely cellular data) ana-
logue 78 was one of several inhibitors selected for testing
in vivo. This inhibitor showed an 18% reduction in
infarct size when dosed iv at 30 mg kgꢀ1 in a rat per-
manent MCAO (Middle Cerebral Artery Occlusion)
model.16
4. Karanewsky, D. S.; Kalish, V. J.; Robinson, E. D.;
Ullman, B. R. U.S. Patent 6,242,422 B1, 2001.
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J. C.; Pham, B.; Kodandapani, L.; Smidt, R.; Diaz, J. L.;
Fritz, L. C.; Tomaselli, K. J. Bioorg. Med. Chem. Lett.
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A new, novel class of oxamyl dipeptide caspase inhibi-
tors were prepared. The SAR reveals that the activity of
this series can be optimized using either polyfluoro-
phenoxy, dichlorobenzoyloxy, or diphenylphosphinyl
as the warhead, valine, or tert-butyl valine at P2, and
2-substituted phenyl oxamides or halogenated phenyl
oxamides at P4. These analogues are potent, broad
spectrum caspase inhibitors (low nanomolar activity)
that are active in cellular models of apoptosis and
show promise in vivo. The nature of the SAR and the
limited diversity of the analogues discussed here show
that much work remains in exploring this series of
inhibitors.
6. Mittl, P. R. E.; DiMarco, S.; Krebs, J. F.; Bai, X.;
Karanewsky, D. S.; Priestle, J. P.; Tomaselli, K. J.;
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P.; Robinson, E. D.; Ullman, B. R.; Wu, J. C.; Pham, B.;
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057298, 2002.
9. Assay definitions: (a) Monocyte: Primary monocytes
isolated from peripheral human blood by Dextran sedi-
mentation and Ficoll. Cells were stimulated overnight with
staph A. Inhibition of IL-1b production evaluated with
human IL-1b ELISA assay (R&D Systems). See: Bleeker,
M. W. P.; Netea, M. G.; Kullberg, B. J.; van der Ven-
Jongekrijgg, J.; van der Meer, J. W. Immunology 1997, 91,
548; Hamon, Y.; Luciani, M.-F.; Becq, F.; Verrier, B.;
Rubartelli, A.; Chimini, G. Blood 1997, 90, 2911; (b) Con
A: Rat embryonic cortical neurons exposed to 100 nM
concanaval A for 24 h; survival measured by MTS
Acknowledgements
The authors wish to thank Alfred Spada, Tom Hayes,
and Judy Dryden for their contributions in preparing
this manuscript.