Novel bis-(arylsulfonamide) hydroxamate-based selective MMP inhibitors

Article abstract of DOI:10.1016/j.bmcl.2008.04.035

A series of bis-(arylsulfonamide) hydroxamate inhibitors were synthesized. These compounds exhibit good potency against MMP-7 and MMP-9 depending on the nature, steric bulk, and substitution pattern of the substituents in the benzene ring. In general, the preliminary structure-activity relationships (SAR) suggest that among the DAPA hydroxamates (i) electron-rich benzene rings of the sulfonamides may produce better inhibitors than electron-poor analogs. However, potential H-bond acceptors can reverse the trend depending on the isozyme; (ii) isozyme selectivity between MMP-7 and -9 can be conferred through steric bulk and substitution pattern of the substituents in the benzene ring, and (iii) the MMP-10 inhibition pattern of the compounds paralleled that for MMP-9.

Full text of DOI:10.1016/j.bmcl.2008.04.035

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 18 (2008) 3333–3337
Novel bis-(arylsulfonamide) hydroxamate-based
selective MMP inhibitors
Rajesh Subramaniam,a Manas K. Haldar,a Shakila Tobwala,b Bratati Ganguly,b
D. K. Srivastavab,* and Sanku Mallika,*
aDepartment of Pharmaceutical Sciences, North Dakota State University, 1401 Albrecht Blvd, Fargo, ND 58105, USA
bDepartment of Chemistry, Biochemistry and Molecular Biology, North Dakota State University, Fargo, ND 58105, USA
Received 12 March 2008; revised 9 April 2008; accepted 10 April 2008
Available online 16 April 2008
Abstract—A series of bis-(arylsulfonamide) hydroxamate inhibitors were synthesized. These compounds exhibit good potency
against MMP-7 and MMP-9 depending on the nature, steric bulk, and substitution pattern of the substituents in the benzene ring.
In general, the preliminary structure–activity relationships (SAR) suggest that among the DAPA hydroxamates (i) electron-rich ben-
zene rings of the sulfonamides may produce better inhibitors than electron-poor analogs. However, potential H-bond acceptors can
reverse the trend depending on the isozyme; (ii) isozyme selectivity between MMP-7 and -9 can be conferred through steric bulk and
substitution pattern of the substituents in the benzene ring, and (iii) the MMP-10 inhibition pattern of the compounds paralleled
that for MMP-9.
ꢀ 2008 Elsevier Ltd. All rights reserved.
Matrix metalloproteinases (MMPs) are a family of more
than 26 zinc- and calcium-dependent endopeptidases
that mediate several physiological processes like tissue
remodeling, angiogenesis, and cell signaling, among oth-
ers.1 Abnormal MMP expression has been implicated in
various pathological conditions including cardiovascu-
lar diseases, cancer progression and metastasis, rheuma-
toid arthritis, and multiple sclerosis.2
Succinyl hydroxamate derivatives have been shown to
be potent inhibitors of MMPs (e.g., marimastat and
batimastat, Fig. 1).9,10 We initiated our efforts of
MMP inhibitor synthesis based on the 2,3-diaminoprop-
anoic acid (DAPA) scaffold for the following reasons: (i)
the DAPA scaffold is of comparable length to the succi-
nate scaffold, and thus the b-substituent can potentially
orient into the S10 pocket, commonly referred to as the
‘selectivity pocket’ of MMPs; (ii) simple synthesis proto-
cols; (iii) a sulfonamide derivative can provide crucial H-
bonding interactions to the enzyme backbone either as a
The MMP inhibitors in cancer clinical trials yielded dis-
appointing results.3 Part of the failure has been attrib-
uted to the lack of isozyme selectivity of the inhibitors
resulting in poor or indifferent clinical outcomes.3
Matrilysin (MMP-7) often is overexpressed by cancer
cells4 and has been implicated to facilitate cell transfor-
mation5 and resist apoptosis.6 MMP-9 has been shown
to promote tumor invasiveness and metastasis7 apart
from occasional tumor-preventive roles.4,8 Isozyme-
selective inhibition of MMPs can therefore potentially
result in better clinical outcomes.3
10
donor (NH) or as an acceptor (S@O), either in the P1
or in the P10 sites (Fig. 2) and (iv) the a-substituent may
contribute to increase the potency of the inhibitors.
O
S
O
H
HO
N
O
O
N
H
NHMe
H
N
HO
O
N
NHMe
H
OH
O
S
Keywords: MMP inhibitors; Bis-(arylsulfonamide); Hydroxamate.
*
Corresponding authors. Tel.: +1 701 231 7888; fax: +1 701 231 8331
(S.M.); e-mail addresses: dk.srivastava@ndsu.edu; sanku.mallik@
ndsu.edu
Marimastat
Figure 1. Succinyl hydroxamate derivatives.
Batimastat
0960-894X/$ - see front matter ꢀ 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.04.035

3334
R. Subramaniam et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3333–3337
O
O
S
Ar
O
P1' substituent
H
N
1
H
R
O
N
H
O
HO
Other pocket-filling
substituents
R
HO
H
N
H
N
H
α
O
R
N
O S
Ar
P1 substituent
O
O
N
Figure 2. Succinyl hydroxamate derivatives versus DAPA sulfonamide hydroxamate derivatives.
The synthesis of the DAPA hydroxamates is shown in
Scheme 1. Racemic 2,3-DAPA was converted to the
bis-(arylsulfonamide) derivative under alkaline condi-
tions in one step by treating with the respective aryl sul-
fonylchloride. The bis-(arylsulfonamide) carboxylic acid
derivatives were converted to the corresponding O-ben-
zyl hydroxamates under standard peptide coupling
conditions. Removal of the benzyl group yielded the de-
O
S
Ar
O
P1'
N
O
H
HN
HO
N
H
n
N
H
O
S
sired hydroxamates in moderate to excellent yields
(Scheme 1).
H
O
O
Ar
N
Sulfonamide derivatives of a-amino hydroxamates have
been shown to be potent inhibitors of MMPs. One of the
key interactions for the potency was the a-sulfonamide
interaction with the ‘MMP selectivity’ P10 pocket by a
H-bond.10,11 Hence, bis-(arylsulfonamide) hydroxamate
derivatives of the L-ornithine and L-lysine were also pre-
pared (Scheme 1) to explore the x-substituent interac-
tion to the other pockets of the MMPs (P20, P30, etc.)
while the a-substituent was expected to act as the P10
substituent (Fig. 3).
Figure 3. a-Sulfonamide interaction in P10.
In order to be able to make a direct comparison, the hal-
ogenated bis-(arylsulfonamide) hydroxamates were pre-
pared (compounds 5– 8). It was observed that as the size
of the halogen increased, the inhibitory potency in-
creased for MMP-9, with the iodo derivative (compound
8) having single digit nanomolar inhibitory potency
(Ki = 2.6 nM, Table 1). The opposite behavior was ob-
served for MMP-7. The inhibitory potency of the chloro
derivative 6 was similar for both the MMP-7 and -9.
Thus, the iodo derivative 8 exhibited a higher selectivity
by at least three orders of magnitude toward MMP-9,
while the fluoro derivative 5 exhibited four times selec-
tivity for MMP-7 versus MMP-9 (Table 1).
The synthesized compounds were tested in vitro against
recombinant human MMP-7, -9 and -10. The results for
the DAPA derivatives are shown in Table 1. The effect
of the electron withdrawing and releasing properties of
the substituents on the arylsulfonamides was first stud-
ied (compounds 1–4). It was observed that for all the
MMPs studied, inhibitors with electron-rich aromatic
rings (p-OMe or 2,4-di-OMe) were more potent inhibi-
tors than electron-poor analogs (p-NO 2, p-CF3 or
C6F5). However, this pattern could be reversed by the
presence of strong H-bonding interactions as was seen
with halogenated derivatives in the case of MMP-7
(see below).
Surprisingly, compound 9 exhibited an inhibitory po-
tency that was similar to compound 5 (submicromolar)
for MMP-7, but did not inhibit MMP-9 or -10. Usually
longer alkyl or phenylalkyl groups have been employed
to achieve isozyme selectivity for MMP-9 over MMP-1
HATU, HOAt
HO2C NH2
10<pH<11
HO2C NHSO2Ar
BnONH2.HCl
+ ArSO2Cl
HX
NH2
(2N NaOH)
DIPEA, DMF
NHSO2Ar
12h.
n
n
n= 1,3,4
40-100%
O
O
NHSO2Ar
NHSO2Ar
NHSO2Ar
NHSO2Ar
H2, Pd/C, THF, 3-4h
BnOHN
HOHN
or
n
n
MsOH, CHCl3, 12h.
50-60%
Scheme 1. Synthesis of the bis-(arylsulfonamide) hydroxamate inhibitors.
40-95%

R. Subramaniam et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3333–3337
3335
Table 1. Inhibition constants for various DAPA bis-(arylsulfonamide) hydroxamate derivatives
Compound #
Ar-
Ki value (lM)a
Yield (%)
70
MMP-7
MMP-9
0.227
MMP-10
O
S
O
1
2
3
4
5
6
7
8
2.8
0.356
0.335
22
O
S
O
44
93
72
50
72
70
75
0.605
6.6
0.039
1.7
H3CO
O2N
F3C
F
O
S
O
O
S
O
10
7.9
23
O
S
O
0.625
0.237
5.5
2.75
0.23
0.15
0.0026
4.57
ND
ND
1.6
O
S
O
Cl
O
S
O
Br
O
S
1.8
I
O
F3C
O
9
72
0.602
NI
NI
S
O
CF3
O
S
O
10
11
12
92
40
64
6.0
NI
NI
NI
372
O
S
O
8.6
212
124
C6F5
O
S
O
H3CO
0.289
OMe
N
O
S
13
46
4.8
150
ND
O
a NI, no inhibition; ND, not determined.
9
or -7. To the best of our knowledge, this is the first re-
port of achieving MMP-7 selective inhibition by
employing small P10 substituents. That the inhibitory
potencies of the compounds 5 and 9 were similar indi-
cated that P10 pocket of MMP-7 probably contained
an H-bond donor with which fluorine could have favor-
able interaction. In compound 4, the fluorine atoms
were probably forced against the wall of the P10 pocket
that the fluorines are not having a favorable orientation
to act as H-bond acceptors.
low micromolar inhibitory potency, while sparing
MMP-9 and -10. Also compound 11 exhibited Ki val-
ues that were comparable to compound 10 toward
MMP-7 and had a better inhibitory potency against
MMP-7 by at least two orders of magnitude com-
pared to MMP-9. Compound 11 did not inhibit
MMP-10.
The selectivity of an inhibitor toward a MMP could be
inversed by introducing another substituent in the aro-
matic ring. As shown in Table 1, compound 2 had an
inhibitory potency that was at least a magnitude higher
for MMP-9 compared to MMP-7. The introduction of
another methoxy group in the aromatic ring yielded
The presence of H-bond donors elsewhere in the P10
MMP-7 pocket is indicated by the fact that com-
pound 10 was a selective inhibitor for MMP-7 with

3336
R. Subramaniam et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3333–3337
compound 12 that had at least three orders of magni-
tude higher inhibitory potency toward MMP-7 as op-
posed to MMP-9 and -10. This selectivity is probably
conferred by the H-bond donor present in the MMP-7
P10 pocket that interacts favorably with the o-methoxy
group in the aromatic ring.
However, this was not found to be the case (Tables 2
and 3). With longer methylene spacers in the bis-(aryl-
sulfonamide) hydroxamate derivatives, the sulfon-
amide on the a-carbon still seemed to orient to the
P1 pocket as opposed to the P10 pocket, while the
x-sulfonamide interacted elsewhere or was oriented to-
ward the solvent. Among the ornithine derivatives,
compounds 14, 16, and 20 appeared to be selective
for MMP-7 and inhibit the enzyme with low micro-
molar potency (Table 2). Compound 14 was particu-
larly selective for MMP-7 while not inhibiting
MMP-9 and -10. Compound 16 exhibited about 50-
fold selectivity for MMP-7 compared to MMP-9 and
-10. Compound 20 was more selective for MMP-7
(44·) than MMP-9, while not inhibiting MMP-10 at
all. On the other hand, compound 15 did not inhibit
MMP-7 and was about four times more selective to-
ward MMP-9 than MMP-10.
Increasing steric bulk also conferred selectivity for
MMP-7. As shown in Table 1, the bis-(dansylsulfona-
mide) derivative had low micromolar inhibitory potency
against MMP-7 compared to MMP-9.
At this point it should be noted that the synthesized bis-
(arylsulfonamide) hydroxamate derivatives of DAPA
were racemic compounds. It has been shown that while
chirality with small a-substituents does not make any
significant difference to the inhibitory potency, larger
groups can cause at least one to two orders of magni-
tude higher inhibitory potency to one enantiomer versus
the other.11 Currently, we are synthesizing the bis-(aryl-
sulfonamide) derivatives of both enantiomers of DAPA,
and the inhibitory potencies of these compounds will be
reported in the future.
The corresponding carboxylic acids were also tested for
their inhibitory potency. Surprisingly, except for the
DAPA derivative of bis-(4-iodobenzene sulfonamide)
none of the carboxylate derivatives showed any appre-
ciable inhibition of the MMPs studied. In fact, some
of the carboxylate derivatives increased the activity for
MMP-9 and/or MMP-10. The bis-(4-iodobenzene sul-
fonamide) DAPA derivative, however, was a potent
inhibitor with submicromolar Ki values (0.327 lM,
0.936 lM, and 65 lM for MMP-7, MMP-9, and
MMP-10, respectively). The studies are underway to
understand this inhibition pattern.
The structure–activity relationships of the L-ornithine
and L-lysine derivatives were also explored toward
MMP-7, -9, and -10. Based on literature reports, it
was anticipated that the sulfonamide group on the a-
carbon could potentially occupy the P10 pocket10,11
and the longer methylene spacer in these derivatives
could provide hydrophobic interactions with the enzyme
backbone while the sulfonamide on the x-carbon pro-
vides interaction in the other pockets (P20, P30, etc.) of
the targeted MMPs.
Among the lysine derivatives (Table 3), only compounds
23 and 24 inhibited MMP-7 with low micromolar Ki val-
Table 2. Inhibition constants for various bis-(arylsulfonamide) hydroxamate derivatives of (L)-ornithine
Compound #
Ar-
Ki value (lM)a,b
MMP-7
Yield (%)
64
MMP-9
NI
MMP-10
NI
O
S
O
14
15
16
17
18
19
3
O
S
O
50
46
58
63
60
79
NI
4.2
16
H3CO
F3C
F
O
S
O
7
329
NI
337
O
S
O
17%b
31%b
32%b
5
20%b
34.5%b
16.4%b
NI
O
S
O
NI
Cl
O
S
O
9.3%b
221
Br
O
S
20
I
O
a NI, no inhibition.
b % Inhibition at 10 lM inhibitor concentration.

R. Subramaniam et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3333–3337
3337
Table 3. Inhibition constants for various bis-(arylsulfonamide) hydroxamate derivatives of (L)-lysine
Compound #
Ar-
Ki value (lM)a,b
MMP-7
Yield (%)
41
MMP-9
7.5b
MMP-10
O
S
O
21
22
23
24
44b
24b
3.1
34.5b
1.8b
O
S
O
71
69
42
45
NI
NI
NI
NI
F3C
F
O
S
O
27.4b
34.5b
30.9b
O
S
O
2.2
Br
I
O
S
25
46%b
O
a NI, no inhibition.
b % Inhibition at 10 lM inhibitor concentration.
ues, while not inhibiting MMP-10 appreciably and
MMP-9 only sparingly. We do not yet understand the
reason for these observations and mechanistic studies
are underway to gain a better understanding of the
inhibition.
References and notes
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In conclusion, we have developed a series of bis-(aryl-
sulfonamide) hydroxamates as novel MMP inhibitors.
Preliminary data suggest that among the DAPA
hydroxamates (i) electron-rich benzene rings of the sul-
fonamides may provide better inhibitors than electron-
poor analogs. However, potential H-bond acceptors
can reverse the trend depending on the isozyme; (ii) iso-
zyme selectivity between MMP-7 and -9 can be con-
ferred through steric bulk and substitution pattern of
the substituents in the benzene ring, and (iii) the
MMP-10 inhibition pattern of the compounds parallels
that for MMP-9. Detailed structure–activity relation-
ship studies involving these inhibitors and the synthesis
of bis-(arylsulfonamide) hydroxamate derivatives of
DAPA with other groups appended on the b-carbon
to access other MMP pockets are currently in progress
to make more potent and isozyme selective inhibitors
for MMPs.
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This research was supported by the NIH Grant 1R01
CA113746, and NSF DMR-0705767 to S.M. and
D.K.S.
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Supplementary data
Experimental details and characterization data for the
synthesis of the compounds reported in Tables 1–3 are
available as Supplementary data. Supplementary data
associated with this article can be found, in the online
version, at doi:10.1016/j.bmcl.2008.04.035.