Discovery of potent, achiral matrix metalloproteinase inhibitors [4]

Full text of DOI:10.1021/jm980253r

3568
J . Med. Chem. 1998, 41, 3568-3571
Ch a r t 1. Selected MMP Inhibitors
Discover y of P oten t, Ach ir a l Ma tr ix
Meta llop r otein a se In h ibitor s
Stanislaw Pikul,*,† Kelly L. McDow Dunham,†
Neil G. Almstead,† Biswanath De,†
Michael G. Natchus,† Melanie V. Anastasio,‡
Sara J . McPhail,‡ Catherine E. Snider,‡
Yetunde O. Taiwo,† Timothy Rydel,†,§
C. Michelle Dunaway,‡,# Fei Gu,† and
Glen E. Mieling†
Procter and Gamble Pharmaceuticals, Health Care Research
Center, 8700 Mason-Montgomery Road, Mason, Ohio 45040,
and Procter and Gamble, Corporate Research Division,
Miami Valley Laboratories, Cincinnati, Ohio 45253
Received April 27, 1998
In t r od u ct ion . The matrix metalloproteinases
(MMPs) are a family of zinc-containing enzymes that
are capable of degrading many proteinaceous compo-
nents of the extracellular matrix.1 The enzymes have
been implicated in several pathological processes in-
cluding arthritis,2,3 tumor growth and metastasis,4
periodontal disease,5 and multiple sclerosis.6 Consider-
able research has been devoted to the discovery of potent
MMP inhibitors which may act as potential disease-
modifying agents in a number of important pathologies.7
The phase II pancreatic cancer clinical trial data
obtained with Marimastat, the most clinically advanced
MMP inhibitor, has now been reported.8,9
The hydroxamic acid-based MMP inhibitors have
been by far the most extensively studied class of
inhibitors due to the ability of the hydroxamate group
to efficiently complex the catalytic zinc and also to
develop two hydrogen bonds to Glu-202 and Ala-165.10
In addition to binding to the catalytic zinc, the hydrox-
amate-based MMP inhibitors require several more
binding interactions for potent inhibition of the target
enzymes. The S1′ and S2′ pockets have been extensively
used for this purpose. While the design of MMP
inhibitors is gradually becoming less complex, the
chirality of such molecules demands extensive use of the
chiral pool and/or stereoselective synthetic methods for
their preparation. Structures of several MMP inhibitors
that have progressed to early stages of clinical trial can
serve as illustrative examples (see Chart 1).11 We
believed that the design of MMP inhibitors could be
simplified by the introduction of a plane of symmetry.
Such an approach also offered the potential for develop-
ing favorable binding at the S1 pocket. Indeed, this
design, when applied to the sulfonamide-based MMP
inhibitors,11f has led to the discovery of a novel series
of simple, nonchiral, and potent in vitro inhibitors of
the matrix metalloproteinases.12,13
Ch em istr y. The synthesis of the MMP inhibitors
was considerably simplified by the symmetry of the
target molecules (see Scheme 1). Typically, a com-
mercially available R,ω-diaminoalkane 1 was converted
to the corresponding bis-sulfonamide 2 under the stand-
ard acylation conditions. In the next step the 1,3-diaza
ring was formed by condensation of 2 with methyl
glyoxalate polymer under the catalysis of sulfuric acid.
Water formed during this reaction was removed via
azeotropic distillation. The methyl ester 3 was then
subjected to basic hydroxylamine solution14 to provide
the target hydroxamic acid 4 in 40-70% overall yield.
X-ray crystallography data15 obtained for compound 4e
(see Figure 1, top) confirmed the desired structure and
symmetry of this series of MMP inhibitors. Compound
4e was found to assume a chair conformation with the
two methoxyphenylsulfonyl groups in equatorial posi-
tions and the hydroxamic acid group in an axial position.
The arylsulfonyl groups were located in a trans rela-
tionship to each other.
* To whom correspondence should be addressed.
† Procter and Gamble Pharmaceuticals, Health Care Research
Center.
In the case of compound 2d , complete hydrolysis of
the methyl ester occurred during the condensation step
(see Scheme 2). The carboxylic acid 5 was cleanly re-
esterified under standard conditions of thionyl chloride
in methanol to afford methyl ester 6, which upon
‡ Procter and Gamble, Corporate Research Division.
#
Present address: Procter and Gamble Pharmaceuticals, Health
Care Research Center.
§ Present address: Monsanto Corporate Research/Searle BB4K, 700
Chesterfield Parkway North, St. Louis, MO 63198.
S0022-2623(98)00253-2 CCC: $15.00 © 1998 American Chemical Society
Published on Web 08/22/1998

Communications to the Editor
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 19 3569
Sch em e 1a
Sch em e 2a
a
Reagents: (a) MeO2CCHO, H2SO4, benzene, reflux; (b) SOCl2,
a
Reagents: (a) ArSO2Cl, Et3N, CH2Cl2; (b) MeO2CCHO, H2SO4,
MeOH; (c) NH2OH, KOH, MeOH.
benzene, reflux; (c) NH2OH, KOH, MeOH.
Sch em e 3a
a
Reagents: (a) 1. J ones reagent, Me2CO, 2. MeO2CCHO, H2SO4,
benzene, reflux; (b) HS(CH2)3SH, BF3-OEt2; (c) NH2OH, KOH,
MeOH.
ase and stromelysin by these simple, nonchiral mol-
ecules, especially the potent inhibition observed for 4b
containing a six-membered ring. Compounds with five-
membered (4a ) and seven-membered (4c) central rings
were substantially less active with some preferential
inhibition of MMP-1 by the seven-membered ring-based
molecule over the five-membered ring compound. With
the 1,3-piperazine emerging as the most promising ring
size and a desire to maintain the plane of symmetry of
the inhibitors, we decided to explore position C(5) as a
site for further modification. Compounds 4d -f were
designed to test the MMP enzymes’ tolerance for hy-
drophilic and lipophilic substituents. We found that
addition of a hydroxyl group (compound 4d ) had no
effect on potency compared to 4b. However, the gem-
dimethyl substituent present in 4e noticeably improved
potency for all enzymes, especially matrilysin. Interest-
ingly, the larger size of substituent R1 (compound 4f)
seemed to have a somewhat negative effect on potency
especially for gelatinase-B. Another interesting effect
was observed when the R2 group was extended with the
hope of expanding binding opportunities of the alkoxy-
arylsulfonamide in the S1′ pocket. Introduction of the
n-butoxy group in place of the methoxy substituent (see
compound 4g) led to a dramatic loss of potency against
collagenase and gelatinase-B and to a lesser extent
against matrilysin while having no effect on the potency
against stromelysin. One possible explanation for this
effect is the inability of MMP-1 and MMP-7 to accom-
modate the n-butoxyphenyl substituent in their shallow
S1′ pockets. However, a similar effect was observed for
gelatinase-B, known to have a deep S1′ pocket.18 This
and the ability of both MMP-1 and MMP-7 to undergo
a conformational shift to accommodate inhibitors with
F igu r e 1. Conformation of 4e: (top) free, an ORTEP view,
and (bottom) stromelysin-bound.
treatment with hydroxylamine was directly converted
to the target hydroxamic acid 4d .
Compound 4f was prepared from 2d in four steps
(Scheme 3). J ones oxidation of 2d followed by 1,3-
piperazine ring formation as described above (see
Scheme 1) led to the keto ester 7. The thioketal
fragment was then introduced under standard condi-
tions to give 8 which was directly converted to 4f as
described above.
Biology. All compounds were tested for the inhibi-
tion of truncated collagenase-1 (MMP-116), stromelysin
(MMP-317), matrilysin (MMP-716), and gelatinase-B
(MMP-916), and the data are summarized in Table 1.
At first we investigated simple bis(4-methoxyphenyl-
sulfonamides) with different sizes of the central ring.
It was gratifying to see a notable inhibition of collagen-

3570 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 19
Ta ble 1. Inhibition of MMP-1, -3, -7, and -9 by Compounds 4
Communications to the Editor
IC50 (nM)a
MMP-3
1060
33
1290
41
compd
n
R1, R2
R3
MMP-1
4650
79
827
51
MMP-7
MMP-9
4a
4b
4c
4d
4e
4f
4g
0
1
2
1
1
1
1
H, H
H, H
H, H
C6H4-4-OMe
C6H4-4-OMe
C6H4-4-OMe
C6H4-4-OMe
C6H4-4-OMe
C6H4-4-OMe
C6H4-4-OBun
nd
460
nd
366
30
123
716
106
nd
3.9
nd
4.7
2.7
15.6
H, OH
Me, Me
-S(CH2)3S-
Me, Me
24
79
18.4
19.5
2322
22
101
CGS27023A
49.5 (33)b
16.9 (43)b
4.3 (8)b
a
Inhibitor concentrations were run in triplicate, and IC50 determinations were calculated from a 4-parameter logistic fit of the data
within a single experiment (see Supporting Information for details of the enzyme assays). nd, not determined. Ki values reported11 for
b
CGS27023A are given in parentheses.
F igu r e 2. Stereoview of the active site of stromelysin with bound 4e (all amino acid residues within 4-Å distance from the
inhibitor are shown).
larger P1′ groups10 might suggest that the P1 substitu-
ent is responsible for the selectivity observed with 4g.
X-r a y Cr ysta llogr a p h y. To better understand the
interactions of this new series of MMP inhibitors with
stromelysin we have obtained X-ray crystal data of
compound 4e with truncated stromelysin. The stereo-
view of the catalytic site of the enzyme with the bound
inhibitor is shown in Figure 2.19 The enzyme-bound 4e
has a plane of symmetry with a cis arrangement of the
two arylsulfonyl groups as opposed to the trans ar-
rangement observed in the crystal of 4e itself (compare
top and bottom panels in Figure 1). All interactions
involving the hydroxamic acid group, the P1′ alkoxyaryl
group, and the sulfonamide system linking them were
found to be the same as those previously described.20,10
F igu r e 3. Binding interactions between 4e and truncated
However, several interactions unique for this series of
MMP inhibitors can be observed with the second
alkoxyarylsulfonyl group binding to the S1/S2 pocket
(see Figure 3).21 The two sulfonyl oxygen atoms and
the imidazole ring of His-166 developed a network of
hydrogen bonds involving a bridging molecule of water.
This interaction seemed to compensate for the unfavor-
able interactions of the oxygens with the side chain of
stromelysin.
Val-163. The methoxyphenyl group developed several
favorable van der Waals contacts including interactions
of the phenyl ring with the His-166 side chain and the
imidazole ring and between the methyl group and the
aromatic ring of Phe-186. The C(5) carbon of the 1,3-
piperazine ring was pointing out to the solvent; however,

Communications to the Editor
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 19 3571
(8) Rasmussen, H. S.; McCann, P. P. Matrix Metalloproteinase
Inhibitors as a Novel Anticancer Strategy: A Review with
Special Focus on Batimastat and Marimastat. Pharmacol. Ther.
1997, 75, 69-75.
(9) Bramhall, S. R. The Matrix Metalloproteinases and their Inhibi-
tors in Pancreatic Cancer. Int. J . Pancreatol. 1997, 21, 1-12.
(10) Babine, E. R.; Bender, S. L. Molecular Recognition of Protein-
Ligand Complexes: Application to Drug Design. Chem. Rev.
1997, 97, 1359-1472.
the 5,5-gem-dimethyl substituents were still able to
maintain favorable van der Waals distances to the side
chains of both Val-163 and Pro-221. This interaction
could explain a beneficial effect of the hydrophobic
substituents at the C(5) position on potency against
MMP-3 which was observed for 4e-g. Overall, the
X-ray structure of 4e with stromelysin is consistent with
the observed structure-activity relationsip (SAR), al-
though it is not clear why inhibitors containing five- or
seven-membered rings are much less potent compared
to those with the six-membered ring.
Con clu sion . In summary, we have introduced a
symmetry element to the design of MMP inhibitors
which led to the discovery of a novel series of MMP
inhibitors that are both nonchiral and very easy to
synthesize. The compounds based on the 1,3-piperazine
heterocycle are potent inhibitors of collagenase, stromel-
ysin, and gelatinase-B and moderate inhibitors of
matrilysin. On the basis of X-ray crystallography of the
inhibitor-enzyme complex, the binding of 4e with
stromelysin was found to involve several novel interac-
tions at the S1/S2 pocket in addition to the interactions
commonly observed for an arylsulfonamide-hydroxamic
acid framework. Further exploration of this series is
in progress and will be reported in due course.
(11) (a) Broadhurst, M. J .; Brown, P. A.; J ohnson, W. H.; Lawton, G.
Amino acid derivatives. Eur. Pat. Appl. EP 497192, 1992. (b)
Galardy, R. E. Galardin. Drugs Future 1993, 18, 1109-1111.
(c) Ngo, J .; Castaner, G. J . Batimastat. Drugs Future 1996, 21,
1215-1220. (d) Beckett, R. P.; Davidson, A. H.; Drummond, A.
H.; Huxlay, P.; Whittaker, M. Drug Discovery Today 1996, 1,
16-26. (e) Broadhurst, M. J .; Brown, P. A.; Lawton, G.; Ballan-
tyne, N.; Borkakoti, N.; Bottomley, K. M. K.; Cooper, M. I.;
Eatherton, A. J .; Kilford, I. R.; Malsher, P. J .; Nixon, J . S.; Lewis,
E. J .; Sutton, B. M.; J ohnson, W. H. Design and Synthesis of
the Catrilage Protective Agent (CPA, Ro32-3555). Bioorg. Med.
Chem. Lett. 1997, 7, 2299-2302. (f) MacPherson, L. J .; Bayburt,
E. K.; Capparelli, M. P.; Carroll, B. J .; Goldstein, R.; J ustice,
M. R.; Ziu, L. J .; Hu, S.-i.; Melton, R. A.; Fryer, L.; Goldberg, R.
L.; Doughty, J . R.; Spirito, S.; Blancuzzi, V.; Wilson, D.; O′Byrne,
E. M.; Ganu, V. S.; Parker, D. T. Discovery of CGS 27023A, a
Non-Peptidic, Potent, and Orally Active Stromelysin Inhibitor
That Blocks Cartilage Degradation in Rabits. J . Med. Chem.
1997, 40, 2525-2532. (g) Zook, S. E.; Dagnino, R., J r.; Deason,
M. E.; Bender, S. L.; Melnick, M. J . Metalloproteinase Inhibitors,
Pharmaceutical Compositions Containing Them and Their
Pharmaceutical Uses, and Methods and Intermediates Useful
for Their Preparation. Int. Appl. WO9720824, 1997.
(12) Pikul, S.; McDow Dunham, K. L.; Almstead, N. G.; De, B.;
Natchus, M. G.; Taiwo, Y. O. New Heterocyclic Derivatives are
Metalloproteinase Inhibitors - Useful for the Treatment of e.g.
Musculosceletal Disease, Cachexia and Arthritis. Int. Appl.
WO9808822, 1998.
(13) While our work was in progress several patent applications were
published which disclosed novel ring-based MMP inhibitors. For
a review of the recent patent literature, see: Beckett, R. P.;
Whittaker, M. Matrix Metalloproteinase Inhibitors 1998. Exp.
Opin. Ther. Patents 1998, 8, 259-282.
(14) Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis; J ohn
Willey and Sons: New York, 1967; Vol. 1, pp 478-479.
(15) We thank Dr. Fred C. Wireko of Corporate Research Division,
Procter & Gamble Co., for providing us with the high-resolution
X-ray structure of 4e.
Ack n ow led gm en t. The authors wish to thank the
numerous P&GP scientists associated with the MMP
project whose hard work and dedication over many
years have contributed toward the completion of this
work.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and NMR data for the synthesis of 4e; details of
enzyme expression, purification, and inhibition assays; X-ray
crystallographic data for 4e (8 pages). Ordering information
is given on any current masthead page.
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J M980253R