K. J. Wilson et al. / Bioorg. Med. Chem. Lett. 11 (2001) 915–918
917
Table 3. Measured uPA inhibition of bicyclic substituted thiophene-
2-aminothiazoles
aminothiazole as a proximal binding pocket scaffold in
that primary, secondary, and tertiary 2-aminothiazoles
all show uPA inhibitory activity.
In conclusion, it has been demonstrated that the lead
compound 7 is an effective template for probing SARs of
the proximal binding pocket of urokinase. A significant
gain in potency can be realized by both aryl and alkyl
substitution from the 2-aminothiazole group. These
compounds can be prepared utilizing parallel synthetic
methods starting from compound 6. Also, replacement
of the thiophene S-methyl with a methyl group is well
tolerated. Presumably, the methyl and S-methyl deriva-
tives bind very similarly within the S1-binding region.
The use of larger, more rigid hydrophobicpharmaco-
phores gave the best activities. The increase in potency
observed in our 2-aminothiazole thiophene amidine
series that result from substitution at the thiophene
4-position allows a compelling argument to be made
that the proximal binding pocket can be exploited for
further inhibitor optimization.
Compd R Group: Z=SMe Ki Compd R Group: Z=SMe Ki
(mM)
(mM)
34
35
36
0.06
0.11
0.07
40
41
42
0.40
0.91
0.52
37
38
39
0.18
0.18
0.11
43
44
0.50
0.08
R Group: Z=Me
References and Notes
Table 4. Measured uPA inhibition of piperizinyl substituted thio-
phene-2-aminothiazoles
1. Reuning, U.; Magdolen, V.; Wilhelm, O.; Fisher, K.; Lutz,
V.; Graeff, H.; Schmitt, M. Int. J. Oncol. 1998, 13, 893.
2. Edwards, D. R.; Murphy, G. Nature 1998, 394, 527.
3. For an excellent review: Schmitt, M.; Wilhelm, O. G.;
Reuning, U.; Kruger, A.; Harbeck, N.; Lengyel, E.; Graeff,
H.; Gansbacher, B.; Kessler, H.; Burgle, M.; Strzebecher, J.;
Sperl, S.; Magdolen, V. Fibrinolysis Proteolysis 2000, 14, 114.
4. Hjertner, O.; Qvigstad, G.; Hjorth-Hansen, H.; Seidel, C.;
Woodliff, J.; Epstein, J.; Waage, A.; Sundan, A.; Borset, M.
Br. J. Haematol. 2000, 109, 815.
Compd
R Group
Ki (mm)
5. Magill, C.; Katz, B. A.; Mackman, R. L. Emerging Ther-
apeutic Targets 1999, 3, 109.
45
46
47
3-Methoxy
4-Methoxy
2-Fluoro
1.84
0.48
3.06
6. Nienaber, V. L.; Davidson, D.; Edalji, R.; Giranda, V. L.;
Klinghofer, V.; Henkin, J.; Magdalinos, P.; Mantei, R.; Mer-
rick, S.; Severin, J. M.; Smith, R. A.; Stewart, K.; Walter, K.;
Wang, J.; Wendt, M.; Weitzberg, M.; Zhao, X.; Rockway, T.
Structure 2000, 8, 553.
7. Zeslawska, E.; Schweinitz, A.; Karcher, A.; Sondermann,
P.; Sperl, S.; Sturzebecher, J.; Jacob, U. J. Mol. Biol. 2000,
301, 465.
8. Geyer, A. G.; McClellan, W. J.; Rockway, T. W.; Stewart,
K. D.; Weitzberg, M.; Wendt, M. D. Urokinase Inhibitors,
WO 99/05096, 1998.
9. Towle, M. J.; Lee, A.; Maduakor, E. C.; Schwartz, E.;
Bridges, A. J.; Littlefield, B. A. Cancer Res. 1993, 53, 2553.
10. Sturtzebecher, J.; Vieweg, H.; Steinmetzer, T.; Schweinitz,
A.; Stubbs, M. T.; Renatus, M.; Wikstrom, P. Bioorg. Med.
Chem. Lett. 1999, 9, 3147.
11. Preliminary disclosure: Wilson, K. J.; Illig, C. R.; Sub-
asinghe, N.; Hoffman, J. B.; Rudolph, M. J.; Soll, R.; Molloy,
C.; Bone, R.; Green, D.; Randall, T.; Zhang, M.; Lewan-
dowski, F.; Zhou, Z.; Sharp, C.; Maguire, D.; Grasberger, B.;
DesJarlais, R. L. Synthesis of Thiophene-2-carboxamidines
Containing 2-Aminothiazoles and Their Biological Evaluation
as Urokinase Inhibitors, 219th National Meeting of the
American Chemical Society, San Francisco, CA, March 26–
30, 2000; American Chemical Society: Washington, DC, 2000;
MEDI 234.
It seemed evident from these results that considerable
stericflexibility and therefore a variety of sacffolds
could be tolerated in the proximal binding region. We
next examined the effect of biaryl ether substituents and
other bicyclic proximal pocket pharmacophores (Table 3).
An improvement in activity is seen for this class of
compounds. Except for compound 41, all of the com-
pounds in this group displayed Ki values of 0.52 mM or
less with the most active compound being biaryl ether
34 (Ki=0.06 mm). The methyl derivative 44 did not show
a significant difference from 34 in activity. The boost in
potency of these compounds in relation to the simple
phenyl derivative 13 may be attributable to a more
extended, rigid conformation that allows better van der
Waals surface contacts with the proximal binding
pocket of urokinase.
Several piperazine derivatives 45–47 were also prepared
and tested (Table 4). Of the three compounds, only the
ortho-fluoro derivative 47 does not show significant
improvement over the lead compound 7. This last set
of compounds demonstrates the versatility of the
12. Tominaga, Y.; Luo, J.-K.; Castle, R. N. J. Heterocycl.
Chem. 1994, 31, 771.