Modulators of the human CCR5 receptor. Part 2: SAR of substituted 1-(3,3-diphenylpropyl)-piperidinyl phenylacetamides

Article abstract of DOI:10.1016/j.bmcl.2005.08.014

SAR and DMPK studies led to the identification of substituted N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-2-phenylacetamides as potent and orally bioavailable ligands for the human CCR5 chemokine receptor.

Full text of DOI:10.1016/j.bmcl.2005.08.014

Bioorganic & Medicinal Chemistry Letters 15 (2005) 5012–5015
Modulators of the human CCR5 receptor. Part 2: SAR
of substituted 1-(3,3-diphenylpropyl)-piperidinyl phenylacetamides
John G. Cumming,a,* Anne E. Cooper,b Ken Grime,b Chris J. Logan,b
Sharon McLaughlin,a John Oldfield,a John S. Shaw,a Howard Tucker,a Jon Wintera
and David Whittakera
aRespiratory & Inflammation Research Area, AstraZeneca, Mereside, Alderley Park, Macclesfield, Cheshire SK10 4TG, UK
bAstraZeneca R&D Charnwood, Bakewell Road, Loughborough LE11 5RH, UK
Received 27 July 2005; accepted 1 August 2005
Available online 9 September 2005
Abstract—SAR and DMPK studies led to the identification of substituted N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-2-
phenylacetamides as potent and orally bioavailable ligands for the human CCR5 chemokine receptor.
Ó 2005 Elsevier Ltd. All rights reserved.
The chemokine receptor CCR5 is expressed on T-lym-
phocytes, monocytes, macrophages, dendritic cells,
microglia and other cell types. These receptors detect
and respond to several chemokines, principally ‘‘regulat-
ed on activation normal T-cell expressed and secreted’’
(RANTES) and macrophage inflammatory proteins
(MIP) MIP-1a and MIP-1b, resulting in the recruitment
of cells of the immune system to sites of disease. CCR5
is also a co-receptor for HIV-1 and other viruses, allow-
ing these viruses to enter cells. Individuals who are
homozygous for a 32-bp deletion in the gene encoding
CCR5, whilst otherwise healthy, are strongly protected
against HIV-1 infection.1 Other studies indicate a role
for CCR5 and its ligands in disorders such as rheuma-
toid arthritis,2 multiple sclerosis,3 transplant rejection4
and inflammatory bowel disease.5 These observations
suggest that molecules that modulate the CCR5 receptor
would have potential benefit in a wide range of diseases.
The antagonism of CCR5 by small molecules has be-
come an active area of research in many pharmaceutical
companies.1
pounds for further optimisation. Compounds 16 had
been shown to be functional antagonists at the human
CCR5 receptor with binding IC50ꢀs below 100 nM. We
now wish to report further improvements in CCR5
potency by SAR studies around the diphenylpropyl part
of the structure.
R
N
N
O
SO2Me
1a: R = allyl
1b: R = cyclopropyl
1c: R = ethyl
We chose to fix on the amide N-ethyl substituent found
in 1c for our exploration of the SAR on the diphenyl
portion.7 A general scheme for the convergent synthesis
of analogues 3 is shown in Scheme 1. Variously substi-
tuted 3,3-diphenylpropanals 4 were used in a reductive
amination reaction with the piperidine 2, which was
prepared in three steps from 1-benzyl-4-piperidone.
Aldehyde 4a (used to prepare the di-(4-fluorophenyl)
analogue 3a) was prepared from the commercially avail-
able chlorobutyl compound 5 by elimination of the cor-
responding iodide followed by ozonolysis (Scheme 2).
The other aldehydes 4 were prepared either from
a substituted benzophenone 6 by Horner–Emmons
We have previously reported6 our initial investigations
into small molecule inhibitors of CCR5 which led to
the identification of N-alkyl-N-[1-(3,3-diphenylpropyl)-
piperidin-4-yl]phenylacetamides 1 as suitable lead com-
Keywords: CCR5; Chemokine receptor modulator.
*
Corresponding author. Tel.: +44
1625510823; e-mail: john.cumming@astrazeneca.com
0 1625517755; fax: +44 0
0960-894X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.08.014

J. G. Cumming et al. / Bioorg. Med. Chem. Lett. 15 (2005) 5012–5015
5013
Et
N
Et
R1
O
a, b, c
d
N
N
O
SO2Me
N
HN
O
SO2Me
R2
2
3
Scheme 1. Reagents and conditions: (a) EtNH2ÆHCl, NaBH(OAc)3, MeOH, rt; (b) 4-SO2Me-C6H4CH2CO2H, iPr2NEt, DCCI, DMAP, CH2Cl2, rt;
(c) HCOONH4, 30%Pd/C, EtOH, rt; (d) 4, NaBH(OAc)3, CH2Cl2, rt.
F
F
Et
N
O
R
Cl
a, b, c
N
O
SO2Me
F
F
4a
5
3i: R = CO2Me
3j: R = CONH2
a, b
c
Scheme 2. Reagents and conditions: (a) NaI, acetone, reflux; (b)
KOtBu, THF, rt; (c) O3, CH2Cl2, ꢀ78 °C; PPh3, rt.
3k: R = CN
3n: R = SMe
3o: R = SO2Me
d, e
3p: R = NHBoc
3q: R = NH2
f
i
reaction followed by reduction of the alkene and two-
step conversion of the ester group to an aldehyde, or
from a substituted diphenylmethane 7 by C-alkylation
with allyl bromide followed by ozonolysis (Scheme 3).
Further compounds 3 were prepared by functional
group interconversion of compounds prepared via these
routes (Scheme 4). Thus, ester 3i was converted to pri-
mary amide 3j which was in turn dehydrated to give ni-
trile 3k. Sulfide 3n was oxidized with m-CPBA with
subsequent reduction of the piperidine N-oxide to give
sulfone 3o. Aniline 3q was obtained by removal of the
t-butyloxycarbonyl group from 3p and served as the pre-
cursor to amides 3r–3u and sulfonamides 3v–3x. CCR5
binding potency was assayed by displacement of the
binding of [125I]MIP-1a to membranes prepared from
Chinese hamster ovary (CHO) cells stably expressing
recombinant human CCR5.8 The results are shown in
Table 1.
g or h
3r-3u: R = NHCOR'
3v-3x: R = NHSO2R'
Scheme 4. Reagents and conditions: (a) NaOH, MeOH, rt; (b)
(COCl)2, CH2Cl2, rt; NH3/MeOH, rt; (c) (CF3CO)2O, pyridine,
dioxane, 0 °C to rt; (d) m-CPBA CH2Cl2, rt; (e) CH3COOCHO,
CH2Cl2, 0 °C to rt; (f) TFA, rt; (g) R0CO2H, CDI, Et3N, CH2Cl2, rt;
(h) R0COCl, Et3N, CH2Cl2, rt; (i) R0SO2Cl, Et3N, CH2Cl2, rt.
gave an increase in potency (IC50 < 10 nM), although
incorporation of chlorine in the 4-position of both rings
(3d) was just as detrimental to potency as fluorine. We
interpreted these results in terms of the two phenyl rings
having differing SAR requirements; it appeared that 4-
substitution with chlorine (though not with fluorine) in
one ring led to an increase in potency but was not toler-
ated on the other ring. Separation of the two enantio-
mers of 3c by chiral HPLC showed that the potency
resided in one enantiomer (data not shown). Substitu-
tion of the 3-position of one ring with chlorine (3e, 3f)
led to a drop in potency. We decided to explore further
substituents in the 4-position of one ring, keeping the
other unsubstituted (3g–3x). In general, there is a trend
for increasing potency with increasing electron-with-
drawing power of the 4-substituent, as estimated by
means of rp values9 (Fig. 1). Compounds with strongly
electron-withdrawing substituents such as cyano (3k),
methanesulfonyl (3o) and trifluoromethyl (3h) were the
most potent, while those with electron-donating substit-
uents such as phenyl (3m) and amino (3q) were weakly
active. However, the fluoro (3b) and carboxamido (3j)
analogues seem to be less potent than expected on the
basis of their electron-withdrawing power (Fig. 1). The
receptor tolerates quite large substituents in this posi-
tion, as shown by the phenylacetylamino (3s) and phen-
ylacetylsulfonyl derivatives (3w). Interestingly, there is a
marked drop in potency for the benzoylamino (3t) and
benzenesulfonyl (3x) analogues relative to the acetylami-
no (3r, 3s) and acetylsulfonyl (3v, 3w) analogues, respec-
tively. Clearly electronic effects alone are not sufficient
to explain the SAR. A number of compounds with sub-
Addition of fluorine in the 4-position of both phenyl
rings (3a) resulted in a dramatic loss of potency. Incor-
poration of fluorine in the 4-position of just one phenyl
ring (3b) also gave a drop in potency. In contrast, the
addition of chlorine in the 4-position of one ring (3c)
R1
R1
O
O
a, b, c, d
R2
R2
4
6
R1
e, f
R2
7
Scheme 3. Reagents and conditions: (a) LiN(SiMe3)2, (EtO)2P(O)CH2-
CO2Et, THF, 0 °C to rt; (b) Pd(OH)2, H2, EtOH, rt; (c) LiAlH4, THF,
0 °C; (d) DMP, CH2Cl2, rt; (e) LDA, allyl bromide, ꢀ78 °C to rt; (f)
O3, CH2Cl2, ꢀ78 °C; Me2S, rt.

5014
J. G. Cumming et al. / Bioorg. Med. Chem. Lett. 15 (2005) 5012–5015
Table 1. CCR5 binding data for diphenylpropylpiperidine compounds
unsubstituted ring, with the IC50ꢀs of the fluoro ana-
logues generally within about 2-fold of those of the cor-
responding des-fluoro analogues (e.g., compare 3y with
3c, 3aa with 3q and 3ac with 3v).
a
IC50 (nM)
Compound
R1
R2
1a
1b
1c
3a
3b
3c
3d
3e
3f
—
—
—
—
—
4-F
H
13
32
—
4-F
18
Compounds with IC50ꢀs below 10 nM were tested for
their stability to metabolism by rat hepatocytes in vitro
(at 1 lM).10 The results, expressed as intrinsic clearance
(Clint) values,11 are shown in Table 2.12 The methyl ester
(3i) and cyano (3k) analogues were very rapidly cleared
in vitro. Compounds 3c, 3h and 3l were also rather
unstable to metabolism. However, compounds 3o, 3ab,
and 3ac were more stable and were evaluated for oral
pharmacokinetics (PK) in the rat using a cassette dosing
protocol (compounds were dosed at ꢁ2 mg/kg in a
propyleneglycol formulation, n = 2 animals).13 The sul-
fonamido (3ab), acetamido (3ac) and phenylacetamido
(3s) compounds showed very low plasma levels (Table
2); however, the methanesulfonyl analogue 3o showed
a respectable area under the curve (AUC). Since the
intrinsic clearances of these compounds are similar, it
is possible that the absorption of 3s, 3ab and 3ac is low-
er, consistent with the presence of a hydrogen bond do-
nor in these three compounds but not in 3o.14 The active
enantiomer of 3c, the lead compound 1a and the weakly
potent di-(4-fluorophenyl) analogue 3a were also tested
for in vitro and in vivo PK (Table 2). 4-Chloro analogue
3c and the unsubstituted diphenyl 1a had a high intrinsic
clearance in vitro, high clearance in vivo and low bio-
availability. Compound 3a showed the best PK profile
of those tested, being stable in vitro with a low in vivo
clearance and good bioavailability. This seems likely
to be due to the two fluorine atoms reducing oxidative
metabolism on the phenyl rings of the diphenylpropyl
moiety and indicated to us a possible approach to
improving the oral PK in this series.
780
310
8.5
760
58
4-F
4-Cl
H
4-Cl
3-Cl
4-Cl
H
3,4-di-Cl
4-Me
4-CF3
H
78
28
3g
3h
3i
H
H
2.3
7.1
260
<1.0
6.3
85
4-CO2Me
4-CONH2
4-CN
H
3j
H
3k
3l
H
4-OMe
4-Ph
4-SMe
H
3m
3n
3o
3p
3q
3r
H
H
12
4-SO2Me
4-NHBoc
4-NH2
H
1.7
200
200
26
H
H
4-NHAc
4-NHCOBn
4-NHCOPh
4-NHCOtBu
4-NHSO2Me
4-NHSO2Bn
4-NHSO2Ph
4-Cl
H
3s
H
5.9
130
22
3t
H
3u
3v
3w
3x
3y
3z
3aa
3ab
3ac
H
H
18
11
H
H
740
19
3-F
3-F
3-F
3-F
3-F
4-NHBoc
4-NH2
89
105
7.9
9.1
4-NHAc
4-NHSO2Me
a IC50ꢀs were derived from triplicate measurements whose standard
errors were normally <5% in given assay. Assay to assay
variability was within 2-fold based on the results of the standard
a
compound 1a.
The compounds in this series are functional antagonists
at the CCR5 receptor as shown by their ability to inhibit
the effects of the ligands MIP-1a, MIP-1b and RANTES
9
CN
CF3
SO2Me
8.5
Table 2. Rat in vitro and in vivo PK data for selected compounds
OMe
CO2Me
Cl
a
Compound
Clint
AUCd
Cle
F%f
8
7.5
7
SMe
(lL/min/106 cells) (lM h) (mL/min/kg)
H
NHSO2Me
NHAc
34b
—
—
46g
—
—
—
—
—
—
—
—
10
54
3g
—
—
—
—
—
—
—
—
56
11
Me
3c
3h
3i
37b
>150b
88a
—
—
Ph
NHCOPh
3k
3l
41
—
NH2
-0.6
3o
3ab
3ac
3s
20 ( 3)c
17 ( 5)c
15 ( 4)c
nt
0.174
0.008
0.002
0.012
1.87
0.132
CONH2
F
6.5
NHSO2Ph
0.2
3a
1a
4 ( 0.8)c
54
-0.4
-0.2
0
0.4
0.6
a For procedure see Ref. 10; nt = not tested.
b Clint reported is mean of two separate experiments.
c Clint reported is mean of at least six separate experiments with stan-
Figure 1. Plot of CCR5 potency (ꢀlog10 molar IC50) versus rp values
of R1 for the compounds of Table 1 where R2 = H.
dard error of the mean shown in brackets.
d Plasma AUC 0–6 h, cassette dosing at ꢁ2 mg/kg p.o., n = 2 animals.
e Compounds dosed at 1 mg/kg i.v., n = 3 animals.
f Compounds dosed at 4–10 mg/kg p.o., n = 3 animals.
g Data for active enantiomer.
stituents in the 4-position of one ring and fluorine in the
3-position of the other ring were also examined (3y–
3ac). The SAR was parallel with that observed for the

J. G. Cumming et al. / Bioorg. Med. Chem. Lett. 15 (2005) 5012–5015
5015
4. Fischereder, M.; Luckow, B.; Wuthrich, R. P.; Roth-
¨
in functional systems at concentrations close to their
binding IC50ꢀs. For example, compound 3v (binding
IC50 = 18 nM) inhibited MIP-1b-stimulated calcium
transients in CCR5-expressing CHO cells with an IC50
of 24 nM and inhibited the chemotaxis of human AlloT
cells in response to MIP-1b with an IC50 of 31 nM.
enpieler, U.; Schneeberger, H.; Panzer, U.; Stahl, R. A.
K.; Hauser, I. A.; Budde, K.; Neumayer, H.-H.;
Kra¨mer, B. K.; Land, W.; Schlo¨ndorff, D. Lancet
2001, 357, 1758.
5. Andres, P. G.; Beck, P. L.; Mizoguchi, E.; Mizoguchi, A.;
Bhan, A. K.; Dawson, T.; Kuziel, W. A.; Maeda, N.;
MacDermott, R. P.; Podolsky, D. K.; Reinecker, H. C.
J. Immunol. 2000, 164, 6303.
6. Burrows, J. N.; Cumming, J. G.; Fillery, S. M.; Hamlin,
G. A.; Hudson, J. A.; Jackson, R. J.; McLaughlin, S.;
Shaw, J. S. Bioorg. Med. Chem. Lett. 2005, 15, 25.
7. (a) Burrows, J.; Cooper, A.; Cumming, J.; McInally, T.;
Tucker, H. WO 01/087839, 2001; Chem. Abstr. 2002, 135,
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2003; Chem. Abstr. 2003, 138, 385312.
In summary, SAR studies around the diphenyl portion
of compounds 1 have led to the identification of 4-meth-
anesulfonyl analogue 3o as a highly potent (IC50
1.7 nM) CCR5 antagonist with significant oral expo-
sure. Further SAR and pharmacokinetic studies on this
series will be the subject of future publications.
8. SPA binding assays were conducted in 96-well Opti-
plates (Packard 6005190). Displacement of [125I]MIP-1a
(Amersham IM285) by compounds was measured using
membranes prepared from a h-CCR5 transfected CHO
cell line. Compounds were incubated overnight
Acknowledgments
The authors thank our colleagues Lucy Ashman, Susan
Mellor and Lorraine Newboult for developing and
carrying out the biological assays, and Anthony
Atkinson, the late Craig Martin and Steve Trigg for
carrying out the DMPK studies.
with 0.1 nM
[
125I]MIP-1a, SPA beads (Amersham
RPNQ0001) and membranes expressing the human
CCR5 receptor. The signal was read on a Packard
Topcount.
9. Hansch, C.; Leo, A.; Unger, S. H.; Kim, K. H.; Nikaitani,
D.; Lien, E. J. J. Med. Chem. 1973, 16, 1207.
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891.
12. Compounds were also tested for stability to metabolism
by human liver microsomes and in general the results
reflected the stability in rat hepatocytes (data not
shown).
13. For an example of this type of method, see Korfmacher,
W. A.; Cox, K. A.; Ng, K. J.; Veals, J.; Hsieh, Y.;
Wainhaus, S.; Broske, L.; Prelusky, D.; Nomeir, A.;
White, R. E. Rapid Commun. Mass Spectrom. 2001, 15,
335.
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