Sultam hydroxamates as novel matrix metalloproteinase inhibitors

Article abstract of DOI:10.1021/jm049833g

In this communication we describe the design, synthesis, and evaluation of novel sultam hydroxamates 4 as MMP-2, -9, and -13 inhibitors. Compound 26 was found to be an active inhibitor (MMP-2 IC₅₀ = 1 nM) with 1000-fold selectivity over MMP-1 and good oral bioavailability (F = 43%) in mouse. An X-ray crystal structure of 26 in MMP-13 confirms the key hydrogen bonds and prime side binding in the active site.

Full text of DOI:10.1021/jm049833g

J . Med. Chem. 2004, 47, 2981-2983
2981
Sch em e 1
Su lta m Hyd r oxa m a tes a s Novel Ma tr ix
Meta llop r otein a se In h ibitor s
Robert J . Cherney,* Ruowei Mo, Dayton T. Meyer,
Karl D. Hardman, Rui-Qin Liu,
Maryanne B. Covington, Mingxin Qian,
Zelda R. Wasserman, David D. Christ,
J ames M. Trzaskos, Robert C. Newton, and
Carl P. Decicco
Bristol-Myers Squibb Pharmaceutical Research Institute,
Princeton, New J ersey 08543-4000
Received February 27, 2004
Abstr a ct: In this communication we describe the design,
synthesis, and evaluation of novel sultam hydroxamates 4 as
MMP-2, -9, and -13 inhibitors. Compound 26 was found to be
an active inhibitor (MMP-2 IC50 ) 1 nM) with 1000-fold
selectivity over MMP-1 and good oral bioavailability (F ) 43%)
in mouse. An X-ray crystal structure of 26 in MMP-13 confirms
the key hydrogen bonds and prime side binding in the active
site.
Sch em e 2a
Matrix metalloproteinases (MMPs) are zinc-depend-
ent endopeptidases belonging to the metzincin super-
family.1 There are over 20 known MMPs, which include
gelatinases, collagenases, and stromelysins.2 The MMPs
are involved in the proteolysis of the extracellular
matrix, and they function to aid in the development,
maintenance, and repair of tissues. Under normal
conditions they are expressed in small amounts and are
controlled by endogenous inhibitors. However, uncon-
trolled expression leads to tissue damage that has been
linked to arthritis,3,4 angiogenesis,5 restenosis,6 and
multiple sclerosis.7 This association has created an
intense search for potent MMP inhibitors as potential
therapeutics. Primarily, this search has focused on two
main classes8 of inhibitors: anti-succinates 1 and sul-
fonamides 2 and 3 (Scheme 1). The first clinical com-
pounds were broad-spectrum inhibitors targeted mainly
for cancer.9 However, broad-spectrum MMP inhibition
has been linked to side effects in the clinic,10 and hence,
we sought to find new templates that might offer
different selectivity profiles upon optimization. From
modeling the known scaffolds and examining their
hydrogen bond network, we hypothesized that sultam
4 could be fashioned into a novel MMP inhibitor. Our
model indicated that the pro-S sulfonyl (blue, Scheme
1) of sultam 4 could be positioned to overlay with the
C(4) carbonyl of the anti-succinate class 1. In doing so,
the sultam sulfonyl is placed within hydrogen bond
distance of the conserved leucine on the MMP backbone.
To accommodate this hydrogen bond, the group con-
nected to the nitrogen of the sultam (L-P1′, Scheme 1)
would have a novel entry into the S1′ pocket of the
MMPs, and it was this trajectory that we would need
to optimize. In this communication, we describe the
synthesis and evaluation of sultams 4 as novel MMP
inhibitors.
a
Reagents: (a) (i) Cl2, EtOH/CHCl3, 0 °C; (ii) Et3N, CHCl3, -5
°C, 75%; (b) 4-Ph-Ph-B(OH)2, Cu(OAc)2, Et3N, 4 Å molecular
sieves, CH2Cl2, 13%; (c) H2NOH‚HCl, KOH, MeOH, 30%; (d)
DEAD,P(Ph)3,HOCH2CH2Ph-Ph,THF,88%;(e)K2CO3,ClCH2C6H4OBn,
DMF, Bu4NI, 89%; (f) H2, 5% PdBaSO4, MeOH, quantitative; (g)
Tf2O, (iPr)2NEt, CH2Cl2, 77%; (h) Pd(OAc)2, ArB(OH)2, P(Ph)3,
K2CO3, toluene.
Scheme 2 outlines our initial synthetic entry into the
sultams. Racemic homocystine 5 was oxidized to the
sulfonyl chloride and cyclized as described by Luisi and
Pinnen.11 The resulting sultam 6 was arylated via
copper-promoted chemistry12 to afford 7. Treatment of
7 with a basic hydroxylamine solution gave the hydrox-
amate target 8.
Sultam 6 served as a common intermediate that could
be alkylated to afford 9 or 11. Biaryl 9 was converted
into the target hydroxamate 10 in a manner analogous
to 8. Hydrogenation of 11 gave phenol 12, which was
converted into the aryl triflate 13. Subsequent Suzuki
reactions gave the biaryls 14, which were converted to
the hydroxamates 15 via standard chemistry. Homo-
chiral six-membered sultams were synthesized accord-
ing to Scheme 3. Alcohol 1613 was converted to the
thioacetate 17 prior to chlorine oxidation,14 selective
N-Boc removal, and cyclization to sultam 18. Chemistry
similar to that described in Scheme 2 resulted in the
hydroxamate 23. This procedure was altered to accom-
modate the 4-pyridyl group of 26, which was installed
in one pot15 through the aryl bromide 24. Treatment of
25 with TFA afforded the carboxylate, which was
* To whom correspondence should be addressed. Phone: 609-252-
3066. Fax: 609-252-6601. E-mail: robert.cherney@bms.com.
10.1021/jm049833g CCC: $27.50 © 2004 American Chemical Society
Published on Web 05/08/2004

2982 J ournal of Medicinal Chemistry, 2004, Vol. 47, No. 12
Letters
Sch em e 3a
Ta ble 2. In Vitro Evaluation of Six-Membered Sultams
Ki (nM)a
compd
X
R
MMP-1
MMP-2
MMP-9
MMP-13
23a
23b
23c
26
C
C
C
N
OMe
Cl
tBu
938
318
3166
1085
0.4
<3.3
3.2
0.9
<2.1
8.5
1.2
<5
<5
3
1
10
a
Ki values are an average from three determinations. Standard
deviations are less than 15% in all cases.
a
Reagents: (a) AcSH, DIAD, PPh3, THF, 57%; (b) (i) Cl2, H2O,
(ii) 4 M HCl dioxane, THF; (ii) Et3N, CHCl3, 65%; (c) K2CO3,
ClCH2C6H4OBn, DMF, Bu4NI, 96%; (d) H2, 5% Pd/BaSO4, MeOH,
quantitative; (e) Tf2O, (iPr)2NEt, CH2Cl2, 90%; (f) Pd(OAc)2,
ArB(OH)2, PPh3, K2CO3, toluene; (g) (i) TFA, CH2Cl2, (ii) n-
PrOCOCl, NMM, DMF, -22 °C; (iii) H2NOH‚HCl, NMM, DMF;
(h) BrCH2C6H4Br, K2CO3, DMF, 83%; (i) (i) bis(pinacolato)diboron,
PdCl2(dppf), KOAc, THF, 80 °C, (ii) 4-bromopyridine‚HCl, PdCl2-
(dppf), 2 M Na2CO3, THF, 80 °C; (j) (i) TFA, CH2Cl2, (ii) H2NOBn,
EDC, THF, (iii) H2, 5% Pd/BaSO4, MeOH; (k) K2CO3, Br-CH2-
4-Ph-Ph, DMF.
Ta ble 1. In Vitro Evaluation of Five-Membered Sultams
F igu r e 1. X-ray crystal structure of 26 cocrystallized in
MMP-13.
moderate activity for MMP-2 (Ki ) 667 nM) and MMP-
13 (Ki ) 904 nM). Addition of a methylene afforded 30,
which displayed good affinity for MMP-2 (Ki ) 28.5 nM)
over MMP-1, -9, and -13. Addition of a second methylene
was detrimental because 10 lost substantial affinity for
all the MMPs tested. With the benzyl group established
as having the required trajectory into S1′, we turned
our attention to substitution on the distal ring. The
4-methoxy substitution of 15a provided a 7-fold increase
in affinity for MMP-2 compared to 30 while still
maintaining selectivity over MMP-1 (1000-fold) and
MMP-9 and -13 (10-fold). However, both 3,5-substitution
(15b) and 2-substitution (15c) afforded inactive com-
pounds. Ring size was assessed, and the six-membered
23a was found to be more potent against all the MMPs
tested compared to the five-membered 15a (Table 2).
In addition to the potent affinity, 23a still displayed at
least 700-fold selectivity for MMP-2, -9, and -13 over
MMP-1. As a result, we explored other substituents at
the 4-position using the six-membered ring scaffold. The
4-position proved to be rather accommodating because
electron-withdrawing and -donating substituents were
potent inhibitors (see 23b, 23c, and 26 in Table 2) with
excellent selectivity over MMP-1. In additional studies,
26 was also found to be selective for MMP-2, -9, and
-13 over tumor necrosis factor-R converting enzyme (for
26 TACE Ki >1000 nM).
Ki (nM)a
MMP-1 MMP-2 MMP-9 MMP-13
compd
L
R
8
H
H
H
>4949 667
>4949 28.5
>4949 433
>4949 3.8
>2128
446.7
702
904
206
1055
55
>5025
>5025
30b
10
CH2
CH2CH2
CH2
CH2
CH2
15a
15b
15c
4-OMe
46.7
3,5-diCl >4949 >3333 >2128
2-Me >4949 >3333 >2128
a
Ki values are an average from three determinations. Standard
b
deviations are less than 15% in all cases. Homochiral (R).
converted into the O-benzyl hydroxamate. Mild hydro-
genation16 of the O-benzyl hydroxamate afforded the key
target 26. Similar chemistry utilizing alcohol 27 and
sultam 28 provided the homochiral five-membered
target 30.
The newly synthesized hydroxamates were evalu-
ated17 as MMP-2 and -9 inhibitors for their potential in
cancer5 and as MMP-13 inhibitors for osteoarthritis.3
As previously mentioned, broad-spectrum MMP inhibi-
tors have been linked to side effects in clinical trials;
hence, we used a counterscreen of MMP-1 to assess
initial selectivity. Our first task was to identify a group
bonded to the sultam nitrogen capable of directing a
substituent into the S1′ pocket of the MMPs. Several
groups were attached, and an interesting trend was
observed for biaryl groups (Table 1). Direct attachment
of the biaryl to the sultam nitrogen (see 8) displayed
To better understand the binding of the sultams, 26
was cocrystallized in MMP-13. As shown in Figure 1,
the hydroxamate makes the classical bidentate ligation
to the active site zinc with the rest of the inhibitor

Letters
J ournal of Medicinal Chemistry, 2004, Vol. 47, No. 12 2983
(2) For a review, see: Skiles, J . W.; Gonnella, N. C.; J eng, A. The
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Ther. Targets 2003, 7, 19-34.
Ta ble 3. Mouse Pharmacokinetic Data for 26
mouse PK parameters
iv (n ) 3)a
po (n ) 3)a
dose (mg/kg)
Cl ((L/h)/kg)
Vss (L/kg)
T1/2 (h)
AUC (nM‚h)
F (%)
10
30
5.6
7.3
2.5
3774
4895
43
(5) Fingleton, B. Matrix Metalloproteinase Inhibitors for Cancer
Therapy: The Current Situation and Future Prospects. Expert
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a
Values are an average from three animals.
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431-433.
extending toward the prime side. As suggested by the
SAR, the N-methylene of the sultam gives the biaryl
the critical turn necessary to align the biaryls into the
S1′ pocket. The crystal structure also confirms the
hypothesis that the pro-S sulfonyl of the sultam can be
positioned within the hydrogen bond distance of Leu-
185. In fact, the conformation of the six-membered ring
may help in the formation of this hydrogen bond when
compared to the five-membered ring. The ring carbons
appear to point toward the solvent-exposed area of the
active site and are not involved in any contacts with
the protein.
To assess the pharmacokinetics of the sultams, 26
was selected for a discrete mouse study. Mouse blood
samples were collected serially and analyzed by LC/MS
as shown in Table 3. Although clearance from the blood
was high, 26 was orally bioavailable (F ) 43%).
In conclusion, sultam hydroxamates have been intro-
duced as a new template for MMP inhibition. Proper
alignment of the P1′ group necessitates having a benzyl
alkylated sultam nitrogen. Biaryl groups with para
substitution were found to be potent MMP inhibitors
that spared MMP-1 inhibition. The crystal structure of
26 in MMP-13 indicates that the pro-(S) sultam sulfonyl
is capable of a hydrogen bond to Leu-185. Initial mouse
pharmacokinetics (PK) suggests that the sultam hy-
droxamates are orally bioavailable.
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Ack n ow led gm en t. We thank Dianna L. Blessing-
ton, J ohn V. Giannaras, Sherrill A. Nurnberg, and Paul
J . Strzemienski for in vitro data. We also thank Drs.
Percy H. Carter and J ames J .-W. Duan for a critical
review of the manuscript.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and compound characterization data for target and
intermediate compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
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