P. H. Carter et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3311–3316
3315
i-Pr
Accordingly, we compared the modeled receptor-bound conforma-
tion of two representative compounds (Fig. 4).25 As shown, the
compounds are able to adopt very similar placements of the
benyzlamine and benzamide functionalities, consistent with
the similar SAR in these regions. Moreover, the amide carbonyl
(yellow structure) and hydroxyl (green structure) are forming
analogous intramolecular hydrogen bonds, as predicted. However,
in the low energy conformations, the alkyl side chain is oriented
quite differently in the 2S,3S-hydroxyalkyl series relative to the
amide series, which may underpin the distinctions observed with
regards to mouse activity and chemotaxis potency.
In conclusion, we have demonstrated that a hydroxyethyl iso-
stere offers advantages over an amide side chain in a series of
capped dipeptide CCR2 antagonists. Improvements in binding, che-
motaxis potency, mCCR2 binding, and mouse pharmacokinetics
were noted. Distinct structure–activity relationships within the
glyincamide and malonamide sub-series were discovered. Addi-
tional studies that describe the detailed characterization of 18 will
be published separately, as will studies to extend the SAR observa-
tions described herein.
HN
HN
O
O
H
N
19, R = H, 4.7nM
48, R = Me, 440 nM
49, R = i-Pr, 1,700 nM
N
N
H
R
O
HO
n-Pr
CF3
NH2
O
O
H
N
13, R' = H, 3.4 nM
50, R' = Me, 11 nM
N
N
H
H
O
R'O
n-Pr
CF3
X
51, S, X=3-NH2, 1230 nM
52, S, X=2-NH2, 900 nM
53, S, X=2-NHBoc, 1040 nM
54, R, X=2-NHBoc, 28,000 nM
N
N
N
H
*
H
O
HO
n-Pr
CF3
Figure 3. Masking proton donors. The CCR2 binding IC50 values are shown (see Ref.
13).
Acknowledgments
We gratefully acknowledge Ms. Ruowei Mo and Mr. Dayton
Meyer for their assistance in the preparation of intermediates for
compounds listed in Table 3. We also thank Dr. Mark Saulnier for
his comments on the manuscript.
References and notes
1. Gordon, S.; Taylor, P. R. Nat. Rev. Immunol. 2005, 5, 953.
2. Kang, Y. S.; Cha, J. Jo.; Hyun, Y. Y.; Cha, D. R. Expert Opin. Investig. Drugs 2011, 20,
745.
3. Charo, I. F.; Ransohoff, R. M. N. Engl. J. Med. 2006, 354, 610.
4. Feria, M.; Díaz-González, F. Exp. Opin. Ther. Patents 2006, 16, 49.
5. Carter, P. H.; Cherney, R. J.; Mangion, I. K. Annu. Rep. Med. Chem. 2007, 42, 211.
6. Xia, M.; Sui, Z. Exp Opin Ther Pat. 2009, 19, 295.
Figure 4. Shown is a comparison of the hypothetical receptor-bound conforma-
tions of analogous members of the original amide series (yellow, compound 50 in
Ref. 11; CCR2 IC50 = 11 nM, CTX IC50 = 260 nM) and the 2S, 3S-hydroxyalkylisostere
series (green, compound 13 in this manuscript; CCR2 IC50 = 3.4 nM, CTX
IC50 = 32 nM).
7. Struthers, M.; Pasternak, A. Curr. Top. Med Chem. 2010, 10, 1278.
8. Schall, T. J.; Proudfoot, A. E. I. Nat. Rev. Immunol. 2011, 11, 355.
9. Horuk, R. Nat. Rev. Drug Disc. 2009, 8, 23.
10. Cherney, R. J.; Mo, R.; Meyer, D. T.; Voss, M. E.; Lo, Y. C.; Yang, G.; Miller, P. B.;
Scherle, P. A.; Tebben, A. J.; Carter, P. H.; Decicco, C. P. Bioorg. Med. Chem. Lett.
2009, 19, 3418.
11. Carter, P. H.; Brown, G. D.; Friedrich, S. R.; Cherney, R. J.; Tebben, A. J.; Lo, Y. C.;
Yang, G.; Jezak, H.; Solomon, K. A.; Scherle, P. A.; Decicco, C. P. Bioorg. Med.
Chem. Lett. 2007, 17, 5455.
12. Alex, A.; Millan, D. S.; Perez, M.; Wakenhut, F.; Whitlock, G. A.
MedChemCommun 2011, 2, 669.
13. For the details on the biological assays and on the synthesis of compounds 1–
26, 28, and 48–50, see: Carter, P.; Cherney, R. J. PCT Int. Appl. WO 2002050019.
14. The compounds with R = Et were synthesized via the intermediacy of an earlier
N-protection, as described in Ref. 5.
15. Smith, R. J.; Trzoss, M.; Buhl, M.; Bienz, S. Eur. J. Org. Chem. 2002, 2770.
16. Czajgucki, Z.; Sowinski, P.; Andruszkiewicz, R. Amino Acids 2003, 24, 289.
17. Midland, M. M.; McDowell, D. C.; Hatch, R. L.; Tramontano, A. J. Am. Chem. Soc.
1980, 102, 867.
18. Cherney, R. J.; Mo, R.; Meyer, D. T.; Nelson, D. J.; Lo, Y. C.; Yang, G.; Scherle, P. A.;
Mandlekar, S.; Wasserman, Z. R.; Jezak, H.; Solomon, K. A.; Tebben, A. J.; Carter,
P. H.; Decicco, C. P. J. Med. Chem. 2008, 51, 721.
19. De Lucca, G. V.; Kim, U. T.; Vargo, B. J.; Duncia, J. V.; Santella, J. B. I. I. I.; Gardner,
D. S.; Zheng, C.; Liauw, A.; Wang, Z.; Emmett, G.; Wacker, D. A.; Welch, P. K.;
Covington, M.; Stowell, N. C.; Wadman, E. A.; Das, A. M.; Davies, P.;
Yeleswaram, S.; Graden, D. M.; Solomon, K. A.; Newton, R. C.; Trainor, G. L.;
Decicco, C. P.; Ko, S. S. J. Med. Chem. 2005, 48, 2194.
pharmacokinetics in the murine context. Although the original
capped dipeptide series did not shown substantial binding activity
to the mouse receptor, the amino alcohols generally displayed
measureable binding affinity. The structure–activity relationships
from our limited survey suggested that both the propyl substituent
and the S-alcohol stereochemistry favored mouse CCR2 binding,
such that compounds like 6e, 7e, and 14 exhibited >10-fold reduc-
tions in affinity for mouse CCR2, whereas compounds like 7b, 13,
16, and 18 were equipotent for binding mouse and human CCR2.
We extended these observations by performing additional studies
with 18, and determined that it both blocked the chemotaxis of
mouse monocytes (IC50 = 4 nM) and exhibited useful levels of oral
bioavailability in the mouse (F = 29%), despite relatively high Cl
values (5.1 L/h/kg). Additional screening of compounds in mouse
PK models showed that a number of members of the series exhib-
ited oral bioavailability in the mouse, albeit in the same modest
range (data not shown).
The pharmacology of compound 18 was studied further. The
compound was
a full antagonist of multiple CCR2-mediated
functions (chemotaxis, calcium flux, and cAMP depression), and
was also an antagonist of all of the known CCR2 ligands. It was
>1000-fold selective in a panel of 140 other GPCRs, enzymes, and
transporters. Although it was selective versus CCR1 and CCR3, it
20. The synthesis of 27 followed along the lines of Scheme 1, and used 2-(5-
(trifluoromethyl)-1H-indazol-3-ylamino)acetic acid. This compound was
synthesized in three steps from 2-fluoro-5-(trifluoromethyl)benzonitrile:
hydrazine hydrate, refluxing butanol; ethyl glyoxalate, NaCNBH3; and aq
LiOH, MeOH. For details, see: Carter, P. H.; Cherney, R. J.; Batt, D. G.; Brown, G.
D.; Duncia, J. V.; Gardner, D. S.; Yang, M. G. PCT Intl. Appl. WO 2005020899.
21. Other investigators have also recently reported the synthesis of CCR2
antagonists containing indazoles. See: Zhang, X.; Hufnagel, H.; Hou, C.; Opas,
E.; McKenney, S.; Crysler, C.; O’Neill, J.; Johnson, D.; Sui, Z. Bioorg. Med. Chem.
Lett. 2011, 21, 6042.
did show measurable binding affinity for CCR5 (binding IC50
86 nM).
=
As described in the introduction, the hydroxyalkyl side chain
was designed to act as an amide isostere. While the data described
herein document that the compound series are indeed similar in
many aspects of the SAR, there are also important divergences.
22. Compounds 29–47 are all described in Carter, P. PCT Int. Appl. WO
2004098512.