Carboxylic acid bioisosteres acylsulfonamides, acylsulfamides, and sulfonylureas as novel antagonists of the CXCR2 receptor

Article abstract of DOI:10.1016/j.bmcl.2008.01.127

A series of novel acylsulfonamide, acylsulfamide, and sulfonylurea bioisosteres of carboxylic acids were prepared as CXCR2 antagonists. Structure-activity relationships are reported for these series. One potent orally bioavailable inhibitor had excellent PK properties and was active in a lung injury model in hyperoxia-exposed newborn rats.

Full text of DOI:10.1016/j.bmcl.2008.01.127

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 18 (2008) 1926–1930
Carboxylic acid bioisosteres acylsulfonamides, acylsulfamides,
and sulfonylureas as novel antagonists of the CXCR2 receptor
Michael P. Winters,a,* Carl Crysler,a Nalin Subasinghe,a Declan Ryan,a Lynette Leong,a
Shuyuan Zhao,a Robert Donatelli,a Edward Yurkow,a Marie Mazzulla,a Lisa Boczon,a
Carl L. Manthey,a Christopher Molloy,a Holly Raymond,b Lynne Murray,b
Laura McAlonanb and Bruce Tomczuka
aJohnson & Johnson Pharmaceutical Research and Development, 665 Stockton Drive, Exton, PA 19341, USA
bCentocor Research and Development, 145 King of Prussia Road, Radnor, PA 19087, USA
Received 18 December 2007; revised 30 January 2008; accepted 31 January 2008
Available online 7 February 2008
Abstract—A series of novel acylsulfonamide, acylsulfamide, and sulfonylurea bioisosteres of carboxylic acids were prepared as
CXCR2 antagonists. Structure–activity relationships are reported for these series. One potent orally bioavailable inhibitor had
excellent PK properties and was active in a lung injury model in hyperoxia-exposed newborn rats.
ꢀ 2008 Elsevier Ltd. All rights reserved.
Recruitment of neutrophils and monocytes is a normal
physiological response to infection and tissue damage.
However, excessive numbers of these cells can produce
additional tissue damage by releasing proteases, oxygen
radicals, and other mediators. Proteases in particular
can stimulate mucus secretion,1 and other airway events
associated with COPD,2 acute respiratory distress syn-
drome,3 asthma,2,4 chronic bronchitis,5 pulmonary
fibrosis,6 and cystic fibrosis.7 CXC chemokines that con-
tain the sequence Glu-Leu-Arg (ELR) before the first N-
terminal cysteine residue mediate, in part, the recruit-
ment of neutrophils and a subset of monocytes. ELR+
chemokines act through CXC chemokine receptors
CXCR1 and CXCR2. CXCR2 is selectively stimulated
by chemokines GRO-a, -b, and -c, NAP-2, ENA-78,
while IL-8 and GCP-2 stimulated both CXCR2 and
CXCR1.8,9 There is some contention whether human
neutrophil migration is mediated by IL-8 activation of
one or both CXC receptors, but studies with a selective
CXCR2 antagonist (SB-225002) indicate that neutrophil
chemotaxis may primarily be an effect of CXCR2
induction.10
Inhibitors of CXCR2 have been disclosed by several
groups of workers recently.11 In addition, a noncompet-
itive allosteric inhibitor of CXCR1 and CXCR2, reper-
taxin, is in Phase II clinical trials for the prevention of
reperfusion injury.12 Indolylbuteric acid 1 has been re-
ported as a sub-micromolar inhibitor of CXCR2
(Fig. 1).13 With the hope of identifying an orally bio-
available series of CXCR2 inhibitors, we evaluated ser-
ies of acylsulfonamides
2
(R1 is C-linked) and
acylsulfamides 2 (R1 is N-linked), and a series of sulfo-
nylureas 3, as carboxylic acid bioisosteres of 1.14 Other
acid bioisosteres, such as tetrazoles, were found to
greatly reduce potency and were not pursued further.
The general synthetic schemes to the acylsulfonamides
and acylsulfamides described are shown below (Fig. 2).
O2
S
O2
S
O
O
O
R1
R2
HO
N
N
NH
H
H
NC
NC
NC
F
F
F
N
H
N
H
N
H
Keywords: Carboxylic acid bioisosteres; Acylsulfonamides; Acylsulfa-
mides; Sulfonylureas; CXCR2; Chemokine; IL-8; CXCR1; Indole;
Neutrophils; COPD; Asthma.
1
2
3
*
Figure 1. Acylsulfonamide, acylsulfamide, and sulfonylurea-based
CXCR2 inhibitors.
Corresponding author. Tel.: +1 610 458 5264; fax: +1 610 458
8249; e-mail: mwinter4@prdus.jnj.com
0960-894X/$ - see front matter ꢀ 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.01.127

M. P. Winters et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1926–1930
1927
Shown last is the synthesis of sulfonylurea derivative 16
(Fig. 4). The chloro of 12 was displaced by phthalimide
to give 13, which can then be converted to indole 14
using Fisher indole chemistry described in Figure 2.
The 5-bromoindole 14 was converted to the 5-cyano,
and the phthalimide group removed with hydrazine to
give 15. Treatment with carbonyldiimidazole gave the
isocyanate, which was converted onto the sulfonylurea
16 by reaction with benzenesulfonamide and potassium
carbonate.
O2
S
O
HO2C
CO2H
N
N
a
H
b, c
Br
NC
F
O
N
H
F
N
H
F
4
5
6
Figure 2. General acylsulfonamide and acylsulfamide synthesis.
Reagents and conditions: (a) 4-bromophenylhydrazine-HCl, ZnCl2,
HOAc, 70 ꢁC; (b) CuCN, NMP, 200 ꢁC, lwave; (c) Me2NSO2NH2,
EDC, DMAP, THF, DCM.
Early on, we found that the SAR of the acid mimetics
and the acids was quite similar in the CXCR2 binding
assay.17 At the 5-position of the indole, only CN and
Br were found to be active. At the 2-position of the in-
dole, only halogen-substituted aryl was active. These
positions were left constant in the subsequent SAR
investigation.
Starting with aryl ketone 4, treatment with 4-bro-
mophenylhydrazine hydrochloride and ZnCl2 in acetic
acid at 70 ꢁC afforded indole 5.13a Conversion of the
bromo to cyano with CuCN followed by EDC coupling
of the acid with dimethylsulfamide gave 6.15
A second general route was used to regioselectively syn-
thesize the 5,6-disubstituted indole derivatives (Fig. 3).
Reduction of 2-methoxy-4-nitrobenzonitrile 7 with so-
dium hydrosulfite followed by regioselective iodination
with N-iodosuccinimide furnished iodoaniline 8. Palla-
dium coupling of 8 with TMS-acetylene 9 gave the 2-
TMS-indole 10,16 which was subsequently converted to
the 2-iodoindole with iodine monochloride and then to
the 2-(4-fluorophenyl) derivative 11 by Suzuki coupling.
Acylsulfonamide and acylsulfamide derivatives of the
5,6-disubstituted indoles were synthesized using chemis-
try described in Figure 2.
We first explored the SAR around the acylsulfonamide
bioisostere (Table 1). The first compound made, the
methyl-substituted acylsulfonamide (17), was 72 nM.
First, replacement of the acidic N–H with N–Me (18) re-
sulted in a complete loss of potency confirming the
necessity of an acidic proton at R4 to activity. Replace-
Table 1. SAR of acylsulfonamide derivatives
O2
O
R1
S
N
R4
R2
F
R3
N
NC
I
NC
TMS
a, b
+
H
CO2Me
MeO
NO2
MeO
NH2
7
8
9
Compound
R1
R2
R3
R4
CXCR2 IC50 (lM)
MeO2C
HO2C
17
18
19
20
21
22
23
24
25
26
27
Me
Me
Me
Et
CN
CN
Br
H
H
Me
H
H
H
H
H
H
H
H
H
0.072
>2.0
0.170
0.064
1.30
c
d, e
H
NC
MeO
NC
H
TMS
F
CN
CN
CN
CN
CN
CN
CN
CN
H
N
H
N
H
MeO
n-Pr
Bn
H
10
11
H
1.40
0.22
i-Pr
Ph
H
Figure 3. General acylsulfonamide and acylsulfamide synthesis.
Reagents and conditions: (a) Na2S2O4, THF, H2O; (b) NIS, HOAc;
(c) PdCl2-DPPF-DCM, LiCl, Na2CO3, DMF, 100 ꢁC; (d) ICl, DCM,
0 ꢁC to rt; (e) 4-fluorophenylboronic acid, Pd(OAc)2, tri-o-tolylphos-
phine, Na2CO3, DME/H2O/EtOH, 80 ꢁC.
H
0.260
0.087
0.16
CF3
Me
Me
H
OMe
Me
0.019
O
O
O
N
b
O
a
O
Cl
N
O
Br
F
12
F
13
F
N
H
O2
14
O
S
NH2
Ph
N
H
NH
c, d
e, f
NC
F
NC
N
H
F
N
H
15
16
Figure 4. General sulfonylurea synthesis. Reagents and conditions: (a) potassium phthalimide, DMF, 100 ꢁC; (b) 4-bromophenylhydrazine-HCl,
ZnCl2, HOAc, 70 ꢁC; (c) hydrazine, EtOH, 80 ꢁC; (d) CuCN, NMP, 200 ꢁC, lwave; (e) CDI, CH3CN; (f) PhSO2NH2, K2CO3, acetone, 60 ꢁC.

1928
M. P. Winters et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1926–1930
ment of the 5-cyano with 5-bromo (19) at R2 resulted in
an approximate twofold loss in potency. Steric factors
on the acylsulfonamide R1 substituent appear to be
quite important; ethyl (20) and methyl are preferred,
but n-propyl (21) and benzyl (22) gave almost a 20-fold
loss in potency. Isopropyl (23) and phenyl (24) substitu-
tion demonstrate that branching at the a-carbon is toler-
ated, although not preferred. Replacement of the methyl
with CF3 (25) gave an almost equipotent compound
indicating that electron-withdrawing substituents are
tolerated. Finally, a brief investigation into 5, 6-disubsti-
tuted indoles (R3 substitution) revealed that the 6-meth-
oxy (26) gave a twofold drop in potency while the 6-
methyl (27) gave almost a fourfold improvement in po-
tency, 19 nM against CXCR2.
Table 3. SAR of N-linked sulfonylurea derivatives
O2
O
R1
S
N
NH
H
R2
F
N
H
Compound
R1
R2
CXCR2 IC50 (lM)
37
38
39
16
40
41
Me
Me
Br
0.25
0.64
0.12
0.14
0.40
0.52
CN
Br
Ph
Ph
CN
CN
CN
o-Cl-phenyl
p-F-phenyl
The activity of the acylsulfonamide series prompted the
investigation of the acylsulfamide series (Table 2). The
first compound made (6) had an IC50 of 50 nM, and
led to an exploration of the SAR of this novel series. Re-
moval of one methyl (28) gave more than a twofold loss
in potency, however, removal of the second methyl (29)
restored much of that loss in potency. As in the acylsulf-
onamide series, steric factors are important; replacement
of the dimethyl with diethyl (30) or n-butyl (31) gave a
dramatic decrease in potency, as did phenyl (32). How-
ever, the methoxyethyl (33) gave a much smaller loss in
potency compared to the similarly sized n-butyl imply-
ing an electronic factor may be important. The morpho-
line substitution (34) appears to confirm this electronic
benefit when compared to the diethyl (30). As in the
acylsulfonamide series, substitution at the 6-position of
the indole with methoxy (35) gave an equipotent com-
pound while methyl (36) gave the most potent com-
pound in the series, 24 nM.
the acylsulfonamide series, replacing the R2 bromo with
cyano (38) resulted in a two- to threefold loss in potency.
Substitution of the methyl at R1 with phenyl on both the
bromo (39) and cyano indoles (16) gave improved po-
tency with IC50s of 0.12 and 0.14 lM, respectively.
The sulfonylureas most likely have a different conforma-
tion than either the acylsulfonamides or acylsulfamides
accounting for the preference for phenyl at R1. Ortho-
(40) and para-(41) halogen substitution on the phenyl
are both disfavored.
Compounds from each series were selected for further
evaluation in a CXCR2 calcium flux FLIPR assay,18
and a rabbit neutrophil chemotaxis assay (Table 4).19
While there does not appear to be a strong correlation
between the absolute numbers in the CXCR2 binding
assay and the secondary cellular assays, there is a gen-
eral trend indicating that the more potent compounds
in the binding assay were among the more potent com-
pounds in both the FLIPR assay and the neutrophil che-
motaxis assay.
Next, we investigated the sulfonylurea series (Table 3).
As described below, the SAR of this series differed con-
siderably from the previous two series. The first com-
pound made, where R1 is methyl and R2 is bromo
(37), had an IC50 of 0.25 lM against CXCR2. Unlike
Due to its low IC50 in all three assays, compound 6 was
chosen for further testing. In a screen of cytochrome
P450s, 6 had an IC50 of 1.32 lM versus Cyp2C9, and
>5 lM for isoforms 1A2, 3A4, 2C19, and 2D6. 6 also
had excellent human and rat liver microsomal stability,
100% remaining at 10 min in rat and 76.8% remaining in
human. Plasma-protein binding was very high, >99%
for human and rat. Pharmacokinetic studies of 6 in rats
revealed an iv t1/2 of 2.7 h, very low clearance of 3.8 mL/
min/kg, and excellent oral bioavailability of 107%.
Table 2. SAR of acylsulfamide derivatives
O2
R1
R2
O
S
N
N
H
NC
R3
F
N
H
Compound R1
R2 R3
CXCR2 IC50 (lM)
Table 4. CXCR2 FLIPR and rabbit neutrophil chemotaxis assays
6
Me
Me
H
Me
H
H
H
H
H
H
H
H
0.050
0.12
0.066
1.10
1.10
0.88
0.26
0.15
Compound CXCR2
CXCR2 FLIPR Rabbit neutrophil
chemotaxis
28
29
30
31
32
33
34
35
36
H
H
Et
H
H
H
IC50 (lM) IC50 (lM)
IC50 (lM)
Et
n-Butyl
Ph
6
0.050
0.12
0.005
0.014
0.032
0.070
0.004
0.090
0.7
1.3
2.1
3.0
1.7
5.8
28
17
25
39
37
–CH2CH2OMe
Morpholine
Me
0.072
0.087
0.12
Me OMe 0.057
Me Me 0.024
Me
0.25

M. P. Winters et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1926–1930
1929
1200000
1000000
800000
600000
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Mayer-Ezel, R.; Jakway, J.; Hipkin, R.; Fossetta, J.;
Gonsiorek, W.; Bian, H.; Fan, X.; Terminelli, C.; Fine, J.;
Lundell, D.; Merritt, J.; Rokosz, L.; Kaiser, B.; Li, G.;
Wang, W.; Stauffer, T.; Ozgur, L.; Baldwin, J.; Taveras, A.
J. Med. Chem. 2006, 49, 7603.
12. Bertini, R.; Allegretti, M.; Bizzarri, C.; Moriconi, A.;
Locati, M.; Zampella, G.; Cervellera, M.; di Cioccio, V.;
Cesta, M.; Galliera, E.; Martinez, F.; di Bitondo, R.;
Troiani, G.; Sabbatini, V.; D’Anniballe, G.; Anacardio,
R.; Cutrin, J.; Cavalieri, B.; Mainiero, F.; Strippoli, R.;
Villa, P.; di Girolamo, M.; Martin, F.; Gentile, M.;
Santoni, A.; Corda, D.; Poli, G.; Mantovani, A.; Ghezzi,
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NC
O
N
H
N
H
N
NH
Br
N
Br
H
H
SB-265610
400000
200000
0
Air
SB-265610
3 mg/kg 3 mg/kg 10 mg/kg
6
6
Vehicle
Treatment Group
Figure 5. Effects of CXCR2 Inhibitor
neutrophil accumulation in newborn rats.
6 on hyperoxia-induced
13. (a) Barth, M.; Dodey, P.; Paquet, J.-L. WO Patent
2002092568-A1, 2002; Chem. Abstr. 2002, 137, 369969;
(b) Barth, M.; Dodey, P.; Paquet, J.-L. WO Patent
2002092567-A1; Chem. Abstr. 2002, 137, 369968; (c)
Paquet, J.-L.; Barth, M.; Pruneau, D.; Dodey, P. WO
Patent 2001038305-A2; Chem. Abstr. 2001, 135, 19550.
14. (a) Uehling, D.; Donaldson, K.; Deaton, D.; Hyman, C.;
Sugg, E.; Barrett, D.; Hughes, R.; Reitter, B.; Adkison,
K.; Lancaster, M.; Lee, F.; Hart, R.; Paulik, M.; Sherman,
B.; True, T.; Cowan, C. J. Med. Chem. 2002, 45, 567; (b)
Johansson, A.; Poliakov, A.; Akerblom, E.; Wiklund, K.;
Lindeberg, G.; Winiwarter, S.; Danielson, U.; Samuels-
son, B.; Hallberg, A. Bioorg. Med. Chem. 2003, 11, 2551.
15. EDC coupling of sulfonamides to acids was effective for
synthesis of the acylsulfonamide series.
Following the excellent PK results, 6 was chosen for a
lung injury model of hyperoxia-induced neutrophil
accumulation in newborn rat lungs and compared to a
known positive control, CXCR2 inhibitor SB-265610
(Fig. 5).20 Compound 6 at 10 mg/kg given intraperitone-
ally showed equivalent reduction, approximately 50%,
of hyperoxia-induced neutrophil accumulation in bronc-
hoaveolar lavage (BAL) to SB-265610 at 3 mg/kg.
In conclusion, we identified multiple series of potent
inhibitors of CXCR2. One example, compound 6, has
been shown to have excellent oral bioavailability and
has demonstrated good activity in vivo in a rat model
of lung injury.
16. Ujjainwalla, F.; Walsh, T. Tetrahedron Lett. 2001, 42,
6441.
17. DELFIA binding assays measured binding of Europium-
labeled human IL-8 to cloned human CXCR2 receptor sf9
membrane lysates coexpressed with Gai3b1c2 proteins
(Perkin-Elmer). In a reaction volume of 100 lL in 96-well
0.45 lm HV filtration plates (Millipore) test compound in
assay buffer (50 mM Tris, pH 7.5, 5 mM MgCl2, 25 lM
EDTA, 0.2% BSA, 50 lg/mL saponin, 2 mM CaCl2) was
mixed, in triplicate, with 2 nM Eu-IL-8. Reaction was
initiated by addition of 40 lg/mL suspended lysates, and
incubated for 90 min at room temperature. Plates were
washed 4 times with DELFIA L*R wash buffer (Perkin-
Elmer), (200 lL/well). DELFIA Enhancement Solution
(Perkin-Elmer, 200 lL/well) was added to the plate, the
plate was shaken for 15 min at room temperature, and
time-resolved fluorescence was recorded at 340 ex/612 em
with a 400 ls delay. Binding response was a measure of
maximal fluorescent signal from background (200 nM
unlabeled human IL-8, Biosource), and IC50s were calcu-
lated using GraphPad Prismꢂ software and a four-
parameter logistics equation.
18. IL-8 induced calcium flux (FLIPR, Molecular Devices)
was performed with Chem-1 cells (Chemicon) that contain
a cloned human CXCR2 coupled to Gi/o protein. Con-
fluent cells (100 lL of 5 · 105 cells/mL) were allowed to
adhere to 96-well black, clear-bottom plates overnight in
DMEM without G-418. Growth media was replaced with
100 lL half-strength Calcium 3 fluorescent dye (Molecular
Devices) in assay buffer (Hank’s balanced salt solution
with Ca+2 and Mg+2, 20 mM Hepes, pH 7.4, 2.5 mM
probenecid), 50 lL test compound in assay buffer, in
triplicate, and incubated at 37 ꢁC for 30 min, followed by
an additional 30 min at room temperature. The reaction
was initiated by addition of 50 lL human IL-8 (R&D
Systems, 4 nM in assay buffer with 0.25% BSA), and
fluorescence (485 ex/525 em) was monitored every 2 s for
Acknowledgments
We thank the members of the Johnson and Johnson
PRD Spring House early ADME and PK teams for
their assistance in performing assays on numerous
CXCR2 compounds.
References and notes
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1930
M. P. Winters et al. / Bioorg. Med. Chem. Lett. 18 (2008) 1926–1930
1 min. Agonist response was a measure of maximal
fluorescent signal from background, and IC50s were
determined as for Ref. 17.
1 hour. Cells migrating into the bottom chamber were
measured against background (no GRO-a) using Cell
Titer Glo (Promega), and IC50s were determined as for
Ref. 17.
19. Rabbit neutrophil chemotaxis was performed using a
variation of the method described by Frevert.21 Neu-
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centrifugation on lymphocyte separation media, Accu-
paque (Accurate Chemical). RPMI media containing
0.1% BSA with or without 38 nM GRO-a (R&D
Systems) was preincubated in the bottom chamber of
a 3 lm 96-well ChemTx plate (Neuroprobe) for 1 h at
37 ꢁC. Twenty-five microliters of RPMI media contain-
ing 0.1% BSA and rabbit neutrophils (3 · 106 cells/ml)
were mixed with an equal volume of media containing
test compound and applied to quadruplicate wells on
the top of the membrane, and incubated at 37 ꢁC for
20. Auten, R.; Richardson, R.; White, J.; Mason, N.; Vozzelli,
M; Whorton, M. J. Pharm. Exp. Ther. 2001, 299, 90. Rat
pups were exposed to air or 95% O2–5% air beginning the
day of birth (day 0). On days 2, 3, and 4 the pups were
treated (ip) with indicated amounts of the compounds. On
day 7, the animals were euthanized and the lungs were
lavaged with two volumes of buffer. The number of cells in
the lavages was counted and the proportion of neutrophils
was determined from Wright–Giemsa stained cytospins
using standard methods.
21. Frevert, C.; Wong, V.; Goodman, R.; Goodwin, R.;
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