Synthesis and SAR of bicyclic heteroaryl hydroxamic acid MMP and TACE inhibitors

Article abstract of DOI:10.1016/S0960-894X(03)00127-6

Potent and selective bicyclic heteroaryl hydroxamic acid MMP and TACE inhibitors were synthesized by a novel convergent route. Selectivity and efficacy versus MMPs and TACE could be controlled by appropriate substitution on the scaffolds and by variation of the P1′ group. Select compounds were found to be effective in in vivo models of arthritis.

Full text of DOI:10.1016/S0960-894X(03)00127-6

Bioorganic & Medicinal Chemistry Letters 13 (2003) 1487–1490
Synthesis and SAR of Bicyclic Heteroaryl Hydroxamic Acid
MMP and TACE Inhibitors
A. Zask,a,* Y. Gu,a J. D. Albright,a X. Du,a M. Hogan,a J. I. Levin,a J. M. Chen,a
L. M. Killar,b A. Sung,b J. F. DiJoseph,b M. A. Sharr,b C. E. Roth,b S. Skala,b G. Jin,a
R. Cowling,a K. M. Mohler,c D. Barone,c R. Black,c C. Marchc and J. S. Skotnickia
aWyeth-Ayerst Research, 401 N. Middletown Road, Pearl River, NY 10965, USA
bWyeth Research, PO Box CN800, Princeton, NJ 08543, USA
cImmunex Corporation, Seattle, WA 98101, USA
Received 6 November 2002; accepted 16 January 2003
Abstract—Potent and selective bicyclic heteroaryl hydroxamic acid MMP and TACE inhibitors were synthesized by a novel con-
vergent route. Selectivity and efficacy versus MMPs and TACE could be controlled by appropriate substitution on the scaffolds and
by variation of the P10 group. Select compounds were found to be effective in in vivo models of arthritis.
# 2003 Elsevier Science Ltd. All rights reserved.
Matrix metalloproteinases (MMPs)1 play a fundamental
role in a variety of pathological conditions that involve
extracellular matrix destruction (e.g., arthritis, tumor
metastasis). TNF-a converting enzyme (TACE)2 is
responsible for the release of soluble TNF-a (tumor
necrosis factor-a) whose over expression is character-
Figure 1. Representative anthranilic acid inhibitor.
istic of illnesses such as rheumatoid arthritis and
Crohn’s disease. Due to the broad therapeutic potential
of inhibiting these enzymes this area has been a major
focus of pharmaceutical research.3 The design of inhib-
itors of these zinc containing enzymes has been facili-
tated in recent years by the determination of NMR and
X-ray inhibitor-enzyme structures elucidating structural
requirements that determine potency and selectivity for
the different members of this class of enzymes.4
could explore interactions of inhibitors with new regions
of the enzymes through a rigid scaffold. Heterobicyclic
ring systems such as quinolines met these structural
requirements and allow for preparation of functiona-
lized inhibitors through ready synthetic access to
1-chloro-2-carboxyquinoline precursors. A novel sulfon-
amide anion displacement of chloride from these inter-
mediates facilitated the preparation of analogues
through a convergent synthesis route (Scheme 1).
The anthranilic acid scaffold as a template for hydroxamic
acid based MMP and TACE inhibitors was recently
reported.5,6 Crucial for potent enzyme inhibition in this
system are (1) an ortho relationship between the hydrox-
amic acid and sulfonamide P10 group and (2) a substituent
at the other position ortho to the P10 group (Fig. 1).
The bicyclic heteroaryl ring systems 1 were accessible by
condensation of an aniline or amino heterocycle 2 with
ethoxymethylenemalonate diethylester 3 followed by
thermally induced cyclization.7 Treatment with phos-
phorus oxychloride converted the hydroxy substituent
to the chloride in 4. A convergent route to sulfonamide
6 was designed using the anion of the fully elaborated
sulfonamide P10 group 5 to displace chloride on the
pyridine ring of 4. Hydrolysis of the ester 6 with sodium
Incorporation of the required ortho substituent into a
fused ring was proposed as an entry to a series which
*Corresponding author. Tel.: +1-845-602-2836; fax: +1-845-602-
5561; e-mail: zaska@wyeth.com
0960-894X/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0960-894X(03)00127-6

1488
A. Zask et al. / Bioorg. Med. Chem. Lett. 13 (2003) 1487–1490
the eight position. Transposing a bromine substituent
from the 6 or 7 position to the 8 position (8c,d) gave a
greater than nine-fold increase in TACE activity.
A systematic investigation of substituents at the eight
position (8h–r) revealed that this effect was general for a
variety of groups. In addition, a striking, adverse effect
on MMP-1 activity with a sterically bulky tert-butyl
group at the eight position (8r) was seen. To a lesser
extent, a C-8 trifluoromethyl group was also deleterious
to MMP-1 activity (8h). Molecular modeling using the
TACE and MMP-1 X-ray structures revealed that the
quinoline 8-position interacts with the S20 pocket of the
enzymes.
Replacement of the quinoline nucleus with a hetero-
bicyclic scaffold gave analogues 9 comparable in activity
to the quinolines against MMP-13, 9 and 1 but more
potent versus TACE (Table 2). In the pyrazolopyridines
(9: X=N), removal of the R3 methyl group (9b) led to a
decrease of activity versus all the enzymes. A methyl or
phenyl R4 substituent gave equivalent activity. The
inhibition profiles of the isoxazolopyridine (9: X=O)
and isothiazolopyridine (9: X=S) analogues were not
distinct from the pyrazolopyridines, though 9e appeared
to be more selective versus MMP-1.
Scheme 1. (a) 120–150 ꢀC; (b) Dowtherm, reflux; (c) POCl3; (d) NaH,
DMF; (e) NaOH; (f) (COCl)2; (g) NH2OH.
hydroxide followed by activation of the acid with oxalyl
chloride and reaction of the intermediate acid chloride
with hydroxylamine gave the hydroxamic acid 7.
The quinoline scaffold 8 gave potent, low nanomolar
inhibitors of MMP-13 and MMP-9, with selectivity
versus MMP-1 and TACE (Table 1).8 Substitution at
positions six and seven of the quinoline ring system did
not affect activity. In contrast, dramatic effects on TACE
and MMP-1 inhibition were seen upon substitution at
In these scaffolds (8 and 9) modification of the P10
group by replacement of the methoxy group with fluor-
ine, phenyl or methyl led to a loss of activity versus all
Table 1. Quinoline scaffold inhibitors
Compd
R1
R2
R6
R7
R8
MMP-1a
MMP-9a
MMP-13a
TACEa
8a
8b
8c
8d
8e
8f
8g
8h
8i
Ph
Ph
H
3-Pyr
Ph
3-Pyr
Ph
Ph
3-Pyr
3-Pyr
3-Pyr
3-Pyr
3-Pyr
H
Ph
Ph
Ph
Ph
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
Br
H
H
H
CF3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Br
H
H
H
CF3
CF3
H
H
H
H
H
H
H
H
H
H
H
H
H
Br
Br
H
H
108
172
225
65
172
77
172
933
75
8
11
2
2
11
4
11
2
3
2
3
2
4
5
—
2
6
7
2
1
7
1
7
1
3
1
4
2
3
5
26
4
9
16
>1000
>1000
296
124
>1000
ꢁ1000
>1000
190
H
CF3
I
OCH3
Ph
2-Thienyl
Bn
Vinyl
CH3
CH2CH3
i-Pr
t-Bu
H
124
226
120
161
336
205
627
314
8j
8k
8l
46
151
136
100
200
152
192
344
3100
4200
>1000
1012
956
875
8m
8n
8o
8p
8q
8r
8s
8t
6
8
589
401
124
OCH3
Ph
CH3
3-Pyr
3-Pyr
H
H
H
CF3
CF3
H
H
H
1162
>1000
1
50
>1000
H
H
Br
>1000
124
82
8u
8v
8w
O-4-Pyr
O-CH2CCCH3
O-CH2CCCH3
1
27
9
—
33
OCH3
17
aIC50, nM.

A. Zask et al. / Bioorg. Med. Chem. Lett. 13 (2003) 1487–1490
Table 2. Heterobicyclic scaffold inhibitors
1489
Compd
R1
R2
R3
R4
X
MMP-1a
MMP-9a
MMP-13a
TACEa
9a
9b
9c
9d
9e
9f
9g
9h
9i
3-Pyr
3-Pyr
3-Pyr
3-Pyr
3-Pyr
H
H
H
H
H
OCH3
OCH3
OCH3
OCH3
OCH3
CH3
H
CH3
Ph
Ph
—
N
N
N
O
S550
N
N
N
N
39
913
115
111
2
6
2
9
2
20
3
160
435
138
147
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
10
—
2
3
535
F
OC4H9
CH3
CH3
CH3
CH3
CH3
—
177
1922
116
1805
595
7
1
170
3
1
>1000
86
356
>100
30
O-4-CIPh
O-4-Pyr
OCH2CCCH3
OCH2CCCH3
OCH2CCCH3
2
1
9j
9k
9l
N
O
S2333
ꢁ1000
ꢁ100
ꢁ100
H
H
1911
244
150
6
—
95
34
14
aIC50, nM.
Table 3. Cartilage explant, dialysis and sponge data for 8u and 9i
Table 4. Inhibition of TNF-a release
Compd
Cartilage explanta,b
Dialysisa
Spongea,c
Compd
TACEa
THPb
LPSpo/ip c
8u
9i
42% (44%)
61% (32%)
90% (88%)d
54% (55%)e
44% (39%)
46% (55%)
8v
8w
9j
9k
9l
82
17
30
6
32
58
60
57
42
—
60/95
48/-
52/80
60/81
aCGS-27023A values in parenthesis.
b% Inhibition at 100 nM.
14
c% Inhibition at 50 mpk po bid.
d% Inhibition at 50 mpk po 1 h after dosing.
e% Inhibition at 25 mpk po 1 h after dosing.
aIC50, nM.
b% Inhibition at 3 mM.
c% Inhibition at 100 mpk 1 h after dosing.
enzymes, with the exception of TACE activity when R2
was phenyl (8s). In other modifications, MMP activity
was maintained so long as the oxygen of R2 was present.
A 4-pyridyloxy substituent gave very potent and selec-
tive inhibitors on both the quinoline (8u) and pyr-
azolopyridine (9i) scaffolds and these two compounds
were chosen for further biological evaluation based on
the expected favorable effect of basic substituents on
oral bioavailability.
inhibition. These results demonstrate that 8u and 9i are
orally bioavailable, potent MMP inhibitors active in in
vivo models of osteoarthritis.
Based on molecular modeling studies of the TACE
X-ray crystal structure13 showing that an acetylenic P10
group could fit in the tunnel connecting the S10 and S30
pockets,6 incorporation of a butynyloxy group into the
P10 position of these bicyclic scaffolds gave rise to
In the secondary in vitro assay, quinoline 8u demon-
strated effective ex vivo inhibition of cartilage degrada-
tion (42% @ 100 nM) in the bovine articular cartilage
explant assay (Table 3).9 In the primary in vivo model,
it demonstrated oral bioavailability with 90% inhibition
of MMP-13 at 50 mpk in the mouse dialysis tubing
implant assay.10 In a secondary in vivo model, the rat
sponge-wrapped cartilage implant model of osteoar-
thritis,11 8u showed 44% inhibition of cartilage degra-
dation at 50 mpk po bid. The pyrazolopyridine 9i
showed comparably favorable activity to 8u with 61%
inhibition @100 nM in the cartilage explant assay, 54%
inhibition at 25 mpk po in the dialysis tubing implant
model and 46% inhibition at 50 mpk po bid in the
sponge wrapped cartilage model. Novartis’ sulfonamide-
hydroxamate MMP inhibitor CGS-27023A12 was used
as a standard in the above models giving comparable
Figure 2. Cartilage induced arthritis assay.

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A. Zask et al. / Bioorg. Med. Chem. Lett. 13 (2003) 1487–1490
potent and selective TACE inhibitors. The iso-
xazolopyridine 9k had an IC50 of 6 nM against TACE
and was ꢁ300-fold selective versus MMP-1 and
ꢁ25-fold selective versus MMP-13. Importantly, in
addition to the potent TACE activity, and in contrast to
their non-butynyloxy counterparts, these compounds
were more potent in vitro in the THP cellular assay of
TNF-a release14 and in the mouse in vivo LPSinduced
TNF-a release assay14,15 (Table 4). Compound 8w was
also shown to be effective in the mouse collagen induced
arthritis model of arthritis16 at 100 mpk bid ip with a
reduction of the mean clinical score relative to control
(HulgG) comparable to EnbrelTM (etanercept) dosed at
150 ug/day (Fig. 2).
F. C.; Venkatesan, A. M.; Wehr, T.; Zask, A.; DiJoseph, J.;
Killar, L. M.; Skala, S.; Sung, A.; Sharr, M.; Roth, C.; Jin, G.;
Cowling, R.; Mohler, K. M.; Black, R. A.; March, C. J.;
Skotnicki, J. S. Bioorg. Med. Chem. Lett. 2001, 11, 2189. (c)
Levin, J. I.; Du, M. T.; DiJoseph, J. F.; Killar, L. M.; Sung,
A.; Walter, T.; Sharr, M. A.; Roth, C. E.; Moy, F. J.; Powers,
R.; Jin, G.; Cowling, R.; Skotnicki, J. S. Bioorg. Med. Chem.
Lett. 2001, 11, 235.
6. (a) Chen, J. M.; Jin, G.; Sung, A.; Levin, J. I. Bioorg. Med.
Chem. Lett. 2002, 12, 1195. (b) Levin, J. I.; Chen, J. M.; Du,
M. T.; Nelson, F. C.; Killar, L. M.; Skala, S.; Sung, A.; Jin,
G.; Cowling, R.; Barone, D.; March, C. J.; Mohler, K. M.;
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7. Price, C. C.; Roberts, R. M. J. Am. Chem. Soc. 1946, 68,
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In summary, bicyclic heteroaryl scaffolds have utility in
the preparation of potent and selective MMP and
TACE inhibitors. Variation of substituents on the rings
and the P10 group altered potency and selectivity of the
inhibitors through interaction with enzyme subsites.
Advanced biological evaluation of inhibitors with
appropriate P10 functionality revealed oral activity in in
vivo models of osteo and rheumatoid arthritis.
11. Bishop, J.; Greenham, A. K.; Lewis, E. J. J. Pharmacol.
Toxicol. Meth. 1993, 30, 19.
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