Potent P1′ biphenylmethyl substituted aggrecanase inhibitors

Article abstract of DOI:10.1016/S0960-894X(01)00704-1

A series of cis-1(S)2(R)-amino-2-indanol based compounds with a biphenylmethyl group at the P1′ position was found to be potent aggrecanase inhibitors. Both compounds 2j and 2n possessed very high aggrecanase affinity (IC₅₀=1.5 nM), and showed

Full text of DOI:10.1016/S0960-894X(01)00704-1

Bioorganic & Medicinal Chemistry Letters 12 (2002) 101–104
Potent P10 Biphenylmethyl Substituted Aggrecanase Inhibitors
Wenqing Yao,a,* Michael Chao,a Zelda R. Wasserman,a Rui-Qin Liu,b
Maryanne B. Covington,b RobertNewton, b David Christ,c Ruth R. Wexlera
and Carl P. Deciccoa
aDepartment of Chemistry, Bristol-Myers Squibb Pharma Company, Experimental Station, Wilmington, DE 19880-0500, USA
bInflammatory Diseases Research, Bristol-Myers Squibb Pharma Company, Experimental Station, Wilmington, DE 19880-0500, USA
cDrug Metabolism and Pharmacokinetics Division, Bristol-Myers Squibb Pharma Company, Experimental Station,
Wilmington, DE 19880-0500, USA
Received 11 September 2001; accepted 15 October 2001
Abstract—A series of cis-1(S)2(R)-amino-2-indanol based compounds with a biphenylmethyl group at the P10 position was found to
be potent aggrecanase inhibitors. Both compounds 2j and 2n possessed very high aggrecanase affinity (IC50=1.5 nM), and showed
excellent selectivity over MMP-1 and MMP-9, with moderate selectivity against MMP-2. # 2001 Bristol-Myers Squibb Company.
Published by Elsevier Science Ltd. All rights reserved.
Aggrecanase, an ADAM-TS of the reprolysin family,
was recently isolated, cloned and expressed.1 Recent
studies suggest that aggrecanase plays a pivotal role in
the catabolism of aggrecan in human arthritic disease.2
Hence, there has been substantial interest in developing
a selective aggrecanase inhibitor to prevent the progres-
sion of joint destruction, and to delineate its role in
normal and disease states.3
increase the potency of 1 by modifying its general
structure without loss of the selectivity over MMP-1, -2
and -9. In this communication, we describe our efforts
to optimize compound 1 into a series of highly potent
and selective aggrecanase inhibitors by employing a
biphenylmethyl group at the P10 position (Fig. 1).
Comparison of the X-ray structure of MMP-1 to the
aggrecanase homology model indicates that the S10
pockets differ considerably. Aggrecanase has a deep
hydrophobic S10 pocket, whereas MMP-1 is much shal-
lower.5 We envisioned that large substitutents such as
the biphenyl methyl moiety could fit tightly into the S10
pocket of aggrecanase without perturbing the con-
formation of the native enzyme. In addition, a larger
biphenylmethyl group at the P10 position might provide
additional binding energy through strong hydrophobic
interaction to compensate the loss of a specific hydro-
We recently reported the discovery of a series of cis-
1(S)2(R)-amino-2-indanol based aggrecanase inhibi-
tors represented by structure 1 (IC50=64 nM), having
a 3-hydroxy benzyl and cis-1-amino-2-indanol athte
P10 and P20 positions, respectively.4 Although com-
pound 1 shows excellent selectivity for aggrecanase
relative to neutrophil collagenase 1 (MMP-1), human
gelatinase A (MMP-2), and human gelatinase B (MMP-
9), itis only moderaetly poetntfor aggrecanase. This
selectivity is postulated to be due to a specific hydro-
gen-bond interaction between the hydroxyl group of
the 3-hydroxylbenzyl (P10) and a threonine residue in
the aggrecanase S10 pocketata posiiton occupied by
valine in MMP-1, -2, and -9. In order to advance the
lead from this series into a viable drug candidate tar-
geting degenerative joint diseases, it was necessary to
*Corresponding author. Fax: +1-302-695-1173; e-mail: wenqing.
yao@dupontpharma.com
Figure 1.
0960-894X/02/$ - see front matter # 2001 Bristol-Myers Squibb Company. Published by Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00704-1

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W. Yao et al. / Bioorg. Med. Chem. Lett. 12 (2002) 101–104
gen-bonding interaction between the 3-hydroxybenzyl and
the threonine residue of aggrecanase. It was anticipated
that selectivity against MMP-1 could be achieved by this
large P10 substitutent due to its shallower S10 pocket.
Methyl substitution on the distal (or proximal) phenyl ring
(2b) at the 20 position is well tolerated by aggrecanase,
MMP-2 and MMP-9. However, the chlorine substituted
analogue 2c decreased the affinity for aggrecanase, but
slightly increased the selectivity against MMP-2 and -9.
Compounds 2e–g, which have a large and polar sub-
stituent at the 20 position, bind weakly to aggrecanase and
other MMPs. The poor activity of these compounds is
probably due to the desolvation energy required for
these polar groups to bind in the relatively hydrophobic
S10 pocket. The fact that the methoxy analogue 2d,
which has a substitutent similar in size to the hydroxyl-
methyl analogue 2g, binds tightly to aggrecanase sug-
gested that the poor activity of compounds 2e–g was
probably not the result from steric hindrance of these
substitutents. Compound 2d was the first compound
prepared to have an IC50 in the low nanomolar range.
However, 2d was found to be only moderately selective
againstMMP-9, and was notselective over MMP-2.
The synthesis of compound 2a is outlined in Scheme 1.
Compound 3 was prepared as described previously.4
The benzyl group of 3 was removed by hydrogenation
to furnish the phenol, which was then converted to the
corresponding triflate 4.6 Palladium catalyzed Suzuki
cross coupling of triflate 4 with phenyl boronic acid in
toluene afforded the cross coupling product 5 in high
yield.7 The tert-butyl group of 5 was removed by TFA in
methylene chloride, followed by coupling with O-benzyl
hydroxylamine and hydrogenation to afford the desired
product 2a.
Compound 2a, the first compound prepared in this ser-
ies, incorporates an unsubstituted biphenyl group at the
P10 position. Figure 2 shows the Vander Waals surface
of compound 2a docked in the active site of the aggre-
canase homology model.
A variety of small substitutions at the 30 position are
well tolerated for aggrecanase as well as MMP-2 and -9
(Table 1). The methyl analogue 2h, which has an IC50 of
11.5 nM, shows similar potency to the parent compound
2a. However, the larger isopropyl substitution was not
tolerated by aggrecanase. The poor activity of this
compound suggested that the steric nature of this sub-
stitutent imparts unfavorable interactions in this region,
since the relative small methoxy 2k and halogen 2l ana-
logues have IC50 values of 3.7 and 2.0 nM, respectively.
Compound 2a was found to have an IC50 of 9.8 nM in
the aggrecanase enzymatic assay, more than a 6-fold
increase in potency compared to the 3-hydroxybenzyl
analogue 1. We ascribe the higher potency of 2a to its
enhanced hydrophobic interaction. As expected, com-
pound 2a was extremely weak against MMP-1. How-
ever, 2a also binds tightly to MMP-2 and MMP-9 with
an IC50 of <1.0 and 5.4 nM, respectively. These results
suggested that additional potency and enhanced selec-
tivity might be achievable by further modification of the
biphenyl group.
In contrast to the isopropyl analogue, compound 2j
binds tightly to aggrecanase, more importantly, this
compound displayed more than 200-fold selectivity
against MMP-1 and MMP-9, and moderate selectivity
against MMP-2. Similarly, the methylsulfonamide ana-
logue 2n was also found to be highly potent in the
aggrecanase enzyme assay with an IC50 of 1.5 nM, and
selectivity profile is similar to that of 2j.
In summary, the synthesis of a new series of cis-1-amino-
2-indanol based compounds with biphenyl substitutents
Scheme 1. (a) H2, Pd/C, MeOH; (b) PhN(Tf)2, Et3N, CH2Cl2 (55%);
(c) PhB(OH)2, Pd(OAc)2, PPh3, toluene, H2O, Na2CO3 (96%); (d)
TFA, CH2Cl2 (100%); (e) BnONH2–HCl, TBTU, DMF; (f) H2, Pd/
BaSO4, MeOH (43%).
Figure 2. The active site of aggrecanase homology model docked with
compound 2a.

W. Yao et al. / Bioorg. Med. Chem. Lett. 12 (2002) 101–104
Table 1. Aggrecanase, MMP-1, MMP-2 and MMP-9 binding data
103
Compd
R
IC50 (nM)a,b
Aggrecanase
Ki (nM)a,b
MMP-1
MMP-2
MMP-9
1
—
H
2-Me
2-Cl
64
9.8
11.6
32
3.4
239
75
144
11.5
216
1.5
3.7
2.0
5.5
1.5
30,953
>5000
4107
>5000
>5000
>5000
4868
>5000
>5000
>5000
12,800
>5000
1820
1507
<1
<2.8
27
4.5
1133
2033
500
39
48
43
3324
5.4
4.2
150
347
277
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
2-MeO
—
2-tBuNHSO2
2-HOCH2
3-Me
3422
>2000
1085
87
309
2.8
<2.11
17.2
691
3-i-Pr
—
3-MeO
3-F
<2.8
<2.8
2.8
3-NO2
3-MeSO2NH
1931
>5000
31
aValues are ꢀSD of three determinations unless otherwise noted.
bThe IC50 values on aggrecanase and Ki values on MMPs were determined as previously described.8 All of the hydroxamic acids studies here were
assumed to act as competitive inhibitors of the enzyme, binding to the active site Zn atom as previously demonstrated by crystallographic and NMR
studies of MMPs complexed with related hydroxamic acids.9 On the basis of the assumption of competitive inhibition, the IC50 values were con-
verted to Ki values from the equation, Ki=C50/(1+[S]/Km), where IC50 is the concentration of competing compound producing 50% inhibition of
the enzymatic activity at the substrate concentration [S]. The Km is the substrate concentration that provides a reaction velocity that is half the
maximal velocity obtainable under saturating substrate conditions.
Duke, J. L.; Solomon, K.; George, H.; Bruckner, R.; Nagase,
0
atthe P1 position are reported. Replacing the potential
H.; Itoh, Y.; Ellis, D. M.; Ross, H.; Wiswall, B. H.; Murphy,
metabolically labile 3-hydroxybenzyl group of 1 with a
K.; Hillman, M. C., Jr.; Hollis, G. F.; Newton, R. C.;
substituted biphenyl group dramatically increase the
potency for aggrecanase. The selectivity was achieved
Magolda, R. L.; Trzaskos, J. M.; Arner, E. C. Science 1999,
284, 1664. (b) Abbaszade, I.; Liu, R.; Yang, F.; Rosenfeld,
by varying the substitutions on the distal phenyl ring.
Among the compounds synthesized, 2j and 2n are the
most potent aggrecanase inhibitors, and have excellent
selectivity over MMP-1, -9 and moderate selectivity
over MMP-2. The discovery of a potent and selective
aggrecanase inhibitor provides an important tool to
further study the biological function of this enzyme and
represents a lead in the development of new medications
for degenerative joint diseases.
S. A.; Ross, O. H.; Link, J. R.; Ellis, D. M.; Tortorella, M. D.;
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Acknowledgements
The authors acknowledge J. Austin, J. Giannaras and
Patty Welch for determination of IC50 values in the
aggrecanase, MMP-1, MMP-2, and MMP-9 assays.
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