7200
A. R. Germain et al. / Bioorg. Med. Chem. Lett. 21 (2011) 7197–7200
Table 3 (continued)
Analog
R1
R2
IC50
T. cruzi inhibition
(
l
M)a
Selectivityb
Toxicity
IA
Me
O
N
N
N
N
N
N
Me
13b
0.054 0.012
0.054 versus inactive
CF3
Me
13c
13d
0.250 0.035
1.63 0.534
ND
ND
ND
ND
Me
OMe
13e
13f
0.518 0.653
1.57 1.58
19.5
ND
37.7
ND
OMe
OMe
OMe
Me
O
N
N
13g
16.5 3.5
ND
ND
O
Me
a
Average of at least three runs.
Selectivity = toxicity/inhibition; IA = inactive; ND = not determined.
b
are favored over other aromatic (13e) and aliphatic (13f) substitu-
ents. The N-propyl substituted pyrazole 13a was the most potent
analog. Modification of the phenyl ring yielded a range of potencies.
For example, electron-donating groups were favored over electron-
withdrawing groups 13c, and substitution at the para position with
the bulky t-butyl group 13d resulted in a significant decrease in
activity. Replacement of the linker group with an amide 13g results
in lower inhibition, either due to a conformational perturbation, or
removal of the basic nitrogen. The PBS solubilities of all the ketone
Supplementary data
Supplementary data associated (experimental protocols for the
preparation of compounds) with this article can be found, in the
References and notes
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analogs tested were greater than 200
lM. The solubility of 13a was
found to be >500 M and 13a and was also classified as a ‘static’
l
inhibitor based on the images from the immunofluorescence assay
(data not shown).
The current work evaluated over 300,000 compounds of the
NIH-MLPCN collection to identify compounds capable of inhibiting
T. cruzi replication. After triage through a series of counterscreens
and an orthogonal assay, 25 hits were identified to inhibit T. cruzi
replication. Scaffolds 3 and 4 were selected for further SAR investi-
gation and optimization efforts. As a result of these synthetic stud-
ies, compounds 12c and 13a emerged as the most potent and
selective inhibitors. Compounds 12c and 13a inhibit T. cruzi repli-
cation with an IC50 of 109 and 35 nM, respectively and displayed
no toxicity to the host cells up to 19.5 lM. Future studies will focus
on determining the mode of action of these inhibitors. Both of
these compounds have been registered with NIH Molecular Li-
braries Program (probes ML157 and ML158) and are available
upon request.13
9. Buckner, F. S.; Verlinde, C. L.; La Flamme, A. C.; Van Voorhis, W. C. Antimicrobe
Agents Chemothr. 1996, 40, 1000.
10. (a) Engel, J. C.; Ang, K. K. H.; Chen, S.; Arkin, M. R.; McKerrow, J. H.; Doyle, P. S.
Antimicrobe Agents Chemothr. 2010, 54, 3326; (b) Clayton, J. Nature 2010, 465,
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Acknowledgments
11. Ong, S.-E.; Schenone, M.; Margolin, A. A.; Li, X.; Do, K.; Doud, M. K.; Mani, D. R.;
Kuai, L.; Wang, X.; Wood, J. L.; Tolliday, N. J.; Koehler, A. N.; Marcaurelle, L. A.;
Golub, T. R.; Gould, R. J.; Schreiber, S. L.; Carr, S. A. PNAS 2009, 106, 4617.
12. Bettiol, E.; Samanovic, M.; Murkin, A. M.; Raper, J.; Buckner, F.; Rodriguez, A.
PLoS Negl. Trop. Dis. 2009, 3, 384.
The authors are grateful to Ms. Patti Aha and Ms. Lori Thomae
for their assistance in manuscript preparation. This work was
funded by the NIH-MLPCN Program (1 U54 HG005032-1 awarded
to S.L.S.). S.L.S is an investigator at the Howard Hughes Medical
Institute.
13. Compounds 12c (ML157) and 13a (ML158) are also available from commercial
vendors.