Discovery of N-benzyl-N′-(4-pipyridinyl)urea CCR5 antagonists as anti-HIV-1 agents (II): Modification of the acyl portion

Article abstract of DOI:10.1016/j.bmcl.2010.10.042

Modification of the acyl moiety in the CCR5 lead molecule 2 led to identification of several new classes of CCR5 antagonists. Antiviral activity and pharmacokinetic properties of the synthesized compounds were evaluated. Structure-activity relationship (S

Full text of DOI:10.1016/j.bmcl.2010.10.042

Bioorganic & Medicinal Chemistry Letters 20 (2010) 7401–7404
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Discovery of N-benzyl-N0-(4-pipyridinyl)urea CCR5 antagonists as anti-HIV-1
agents (II): Modification of the acyl portion
Maosheng Duan a, , Jennifer Peckham b, Mark Edelstein a, Robert Ferris a, Wieslaw M. Kazmierski a,
⇑
Andrew Spaltenstein a, Pat Wheelan a, Zhiping Xiong a
a Infectious Diseases Center for Excellence in Drug Discovery, GlaxoSmithKline, Five Moore Drive, Research Ttriangle Park, NC 27709, United States
b Metabolic Pathways Center for Excellence in Drug Discovery, GlaxoSmithKline, Five Moore Drive, Research Ttriangle Park, NC 27709, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Modification of the acyl moiety in the CCR5 lead molecule 2 led to identification of several new classes of
CCR5 antagonists. Antiviral activity and pharmacokinetic properties of the synthesized compounds were
evaluated. Structure–activity relationship (SAR) derived from these studies further guided the optimiza-
tion efforts, ultimately leading to the discovery of 36 with an acceptable drug-like profile.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 16 August 2010
Revised 6 October 2010
Accepted 8 October 2010
Available online 21 October 2010
Keywords:
CCR5 antagonist
HIV
Urea
CCR5 targeted viral entry inhibitors represents a novel antiviral
mechanism against HIV infection by preventing M-tropic virus
from entering host. Blockage of CCR5 has successfully demon-
strated the prevention of the viral infection.1 The recently ap-
proved CCR5-antagonist maraviroc2 has been shown to be an
effective component of highly active antiretroviral therapy
(HAART) for patients harboring predominately M-tropic virus.
However, novel CCR5 antagonists with improved phamarcokinet-
ics (PK) and safety profiles are needed to further expand the use
of this class of antiretrovirals in anti-HIV therapy.3
Boc, the unmasked piperidine in 10 was coupled with various acids
under HATU conditions to furnish 11–36.
All compounds were tested for antiviral activity in both Human
OsteoSarcoma (HOS) (n = 2) and peripheral blood lymphocytes
(PBL) cells (n P 4) against the Ba-L strain of HIV-1.6 Compound
induced cellular toxicity was also investigated using CellTiter-Glo
reagent (Promega). None of the compounds induced cell killing
up to 1
l
M (data not shown) indicating that the observed potency
In our preceding communication,4 we reported the optimization
of 1 at the amine portion, which led to identification of N0-[(4-cyano-
phenyl)methyl]-N-(3-fluorophenyl)-N-piperidinylurea as the opti-
mal amine moiety, exemplified in 2. This compound exhibited
highly potent antiviral activity and a promising pharmacokinetic
profile in rats, providing a foundation for the modification of the acyl
terminal in 3 with the aims to further improve the overall profile of
this class of CCR5 antagonists (Fig. 1).
O
O
O
S
F
N
N
F
H
O
Cl
N
O
R
N
N
N
H
N
R'
acyl portion
F
CN
amine portion
F
PBL IC50 0.4nM
HOS IC50 1.7nM
The synthesis of the acyl analogs 3 was carried out as depicted in
Scheme 1. Reductive amination of 1,1-dimethylethyl 4-oxo-1-piper-
idine carboxylate 4 with 3-fluoroaniline provided secondary aniline
5, one of the urea precursors. Next, 4-(aminomethyl) benzonitrile 6
was reacted with excess of phosgene in the presence of pyridine,
generating isocyanate 7, which was subsequently treated with 5 to
form urea 8. Removal of Boc in 8 followed by a second reductive
alkylation with aldehyde 95 yielded 10. After deprotection of the
1
2
O
R
N
F
modifcation on acyl portion
N
O
N
N
H
CN
F
3
⇑
Corresponding author. Fax: +1 919 483 6053.
E-mail address: maosheng.a.duan@gsk.com (M. Duan).
Figure 1. Evolution of the piperidine based CCR5 antagonists.
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.10.042

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M. Duan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 7401–7404
Boc
Table 2
N
Antiviral potency in HOS and PBL cell assays and pharmacokinetics in rats of primary
sulfonamides 16–19
Boc
NH
a
N
O
Compd
#
R
HOS IC50 PBL IC50 Cl (mL/min/kg) Papp (nM/s
(nM)
(nM)
(rat, 1 mg/kg) @ pH 7.05)
F
Boc
O
N
4
5
N
7
c
N
N
H
16
17
4
5.2
31
<3
<3
NH2
CN
O
b
NC
F
NC
6
8
6.8
5.7
0.9
2.8
9.7
Boc
N
F
d, e
18
19
16
25
<3
O
N
Boc
H
N
N
N
F
H
CN
O
6.6
2
NA
F
10
NA, not available.
9
O
R
N
F
O
N
inferior bioavailability in rats (Table 1). The pyrrolidyl moiety in
sulfonamides 13 and 15 consistently resulted in subnano molar
potencies in PBL assays; however, their PK properties were disap-
pointing. Hydroxylated pyrrolidine appeared even worse, increas-
ing rat clearance ꢀ2-folds (12 vs 13 and 14 vs 15). Therefore,
further optimization of the sulfonamides region was required to
improve pharmacokinetics.
The sulfonamides in Table 1 appeared to be highly hydrophobic
as suggested by their high c log P values. To increase the polarity
and also reduce the size of the sulfonamides, a series of primary
sulfonamides 16–19 was synthesized and evaluated as shown in
Table 2.
These sulfonamides maintained antiviral activity at a low single
digit nM level. Interestingly, halogen substituents appeared to
modulate the clearance in rats with a preference for chloro over
fluoro substituents. Disappointingly, the primary sulfonamides
were not bioavailable in rats presumably because of their poor per-
meability as suggested by their low apparent permeability coeffi-
f, g
N
N
11-36
H
CN
F
Scheme 1. Reagents and conditions: (a) 3-fluoroaniline, NaBH(OAc)3, AcOH,
CH2Cl2, rt, overnight, quant.; (b) phosgene, pyridine, CH2Cl2, 0 °C to rt., 3 h; (c) i-
Pr2EtN, CH2Cl2, rt., overnight, 90%; (d) HCl, rt, quant.; (e) compound 9, NaBH(OAc)3,
i-Pr2EtN, CH2Cl2, rt., 60%; (f) 4 M HCl, rt, quant.; (g) RCOOH, HATU, EtN3, DMF, rt,
30–60%.
is the result of an antiviral effect and not toxicity. Pharmacokinetic
properties were also evaluated in Sprague–Dawley rats at 1 mg/kg
using 5% mannitol with 0.05% acetic acid in DMSO as dose vehicle.
The data is presented in Tables 1–5.
The SAR of lead 2 from our preceding communication suggested
that further modification of the acyl portion is warranted. To this
end, tert-butyl based sulfonamide 11 with a different dichloro sub-
stitution pattern slightly improved PBL potency, but showed
Table 1
Antiviral potency in HOS and PBL cell assays and pharmacokinetics in rats of tert-butyl and pyrrolidyl sulfonamides 2, 11–15
Compd #
R
HOS IC50 (nM)
PBL IC50 (nM)
Rat PK (1 mg/kg)
Cl (mL/min/kg)
c log P (day light)
%F
2
0.4
3
1.7
0.8
18
22
7.5
7.7
11
9
10
12
13
14
1.5
1.5
1.3
0.9
0.5
0.6
NA
0.6
24
8
9
5.4
6.5
4.9
5.9
9.5
43
29
0
15
10
NA, not available.

M. Duan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 7401–7404
7403
Table 3
Antiviral potency in HOS and PBL cell assays and pharmacokinetics in rats of benzoic acid derivatives 20–24
Compd #
R
HOS IC50 (nM)
PBL IC50 (nM)
Rat PK (1 mg/kg)
Cl (mL/min/kg)
c log P (day light)
DOF IC50 (uM)
%F
20
21
1.9
2.6
6.5
NA
18.6
13.3
19
6
1.2
1
19
7.2
22
23
24
6.6
13
32
26
11.3
8.1
20
46
23
0
6
0.8
0.4
20
5.2
4.7
3.7
NA
NA, not available.
Table 5
Table 4
Antiviral potency in HOS and PBL cell assays and pharmacokinetics in rats of aliphatic
acid derivatives 31–36
Antiviral potency in HOS and PBL cell assays and pharmacokinetics in rats of
heterocyclic acyl derivatives 25–30
Compd #
R
HOS IC50 PBL IC50
Rat PK (1 mg/kg)
t1/2 (hr) %F
Compd #
R
HOS IC50 PBL IC50
Rat PK (1 mg/kg)
(nM)
(nM)
Cl
(nM)
(nM)
Cl (mL/min/kg) t1/2 (hr) %F
(mL/min/kg)
31
32
11
19
5.3
20
10
22
2.4
2.6
11
63
25
26
27
2.7
19
4.8
13
24
4.9
5.8
3.4
50
64
60
14.6
22.5
33
34
22
17
NA
22
26
25
4.4
2.6
7
11
6.4
6.1
35
36
6.4
8
49
12
28
4.3
4.4
28
53
8.1
28
17
22
25
13
2.6
11
NA, not available.
Table 6
29
30
8.2
1.1
NA
41
7.2
NA
3
0
Pharmacokinetics of 36 in dog and monkey at 1 mg/kg dosea
Animal
Cl (mL/min/kg)
t
(h)
%F
½
124
Dog
Monkey
12
30
6.6
2.2
45
14
a
Dose vehicle: 5% mannitol with 0.05% acetic acid in DMSO.
NA, not available.
Table 7
cients (Papp) using MDCK cell line as well as high polar surface
area (PSA (Ertl) = 140).
Physical properties of 2 and 36 and their oral exposures in rat and dog (AUC) at 1 mg/
kg dose
We then focused our efforts on removing the sulfonamide moi-
ety altogether in order to further reduce the size and PSA. The
di-halogen substituted benzene analogs 20 and 21 offered similar
potency, and dramatically improved bioavailability as compared
to the primary sulfonamides (Table 3). Small polar groups CN
and OH on the benzene ring (22 and 23) were detrimental to inhib-
itory potency in PBL assays though they did increase compound
bioavailability in rats. In contrast, amide in 24 retained potent
Compd #
MW
c log P
PSA(Ertl)
AUC (ng hr/mL)(1 mg/kg p.o.)
Rat
Dog
2
36
849
644
7.5
4.8
126
100
205
383
22
515
Heterocyclic acyls with reduced lipophilicity were subsequently
explored (Table 4). In particular, pyridine analogs 25, 26 and 27 not
only maintained single digit nM IC50s without dofetilide binding
concerns (data not shown), but also exhibited superior pharmaco-
kinetic properties in rats; unfortunately, these compound were
HOS IC50, but was not bioavailable. In addition, hERG liability
7
measured by dofetilide binding assay (DOF IC50
)
became a con-
cern for this class of compounds (except for 24) most likely due
to the increase in lipophilicity.

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M. Duan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 7401–7404
relatively potent inhibitors of CPY 3A4 (data not shown). In addi-
tion, the five-membered heterocyles 28, 29 and 30 failed to im-
prove either potency or PK.
Modulation of physiochemical properties of the molecule by
reducing mass, lowering c log P and decreasing PSA (Table 7)
finally led to the identification of 36, a potent CCR5 antagonist with
substantial improvement in oral exposures across animal species,
particularly, in dog. This compound was progressed to further
preclinical studies and the results will be published in due
time.
Aliphatic acyl groups were also pursued (Table 5). The tert-butyl
derivative 31 had good antiviral activity in PBL, however, its bio-
availability was not satisfactory. The mono-hydroxylated tert-butyl
analog 32 lost antiviral potency, but, surprisingly, showed the
highest %F among the compounds reported in this communication.
Both the di-hydroxyl and the THP analogs 33 and 34 did not exhibit
an improvement in either antiviral potency or DMPK properties.
The gem-dimethyl nitrile 35 had the most promising pharmacoki-
netics in rats, but, unfortunately, its antiviral activity in the PBL as-
says was substantially decreased. The dimethyl hydroxyl 36
demonstrated the most balanced antiviral and rat PK profiles with
single digit nM IC50s in both HOS and PBL assays and 53% bioavail-
ability in rats.
References and notes
1. Dragic, T.; Litwin, V.; Allaway, P. G.; Martin, R. S.; Huang, Y.; Nagashima, A. K.;
Cayanan, C.; Maddaon, J. P.; Koup, A. R.; Moore, P. J., et al Nature 1996, 381, 667.
2. Price, D. A.; Armour, D.; De Groot, M.; Leishman, D.; Napier, C.; Perros, M.;
Stamman, B. L.; Wood, A. Bioorg. Med. Chem. Lett. 2006, 16, 4633.
3. Kazmierski, W. M.; Gudmundsson, K. S.; Piscitelli, S. C. Annu. Rep. Med. Chem.
2007, 42, 301.
4. Duan, M.; Peckham, J.; Edelstein, M.; Ferris, R.; Kazmierski, M. W.; Wheelan, P.;
Xiong, Z. Bioorg. Med. Chem. Lett. 2010, 20, 7397.
5. Kazmierski, W. M.; Aquino, C.; Chauder, B.; Deanda, F.; Ferris, R.; Jones-Hertog,
D.; Kenakin, T.; Koble, C.; Watson, C.; Wheelan, P.; Yang, H.; Youngman, M. J.
Med. Chem. 2008, 51, 6538.
6. Muniz-Medina, V.; Jones, S.; Maglich, J.; Galardi, C.; Hollinggswirth, R.;
Kazmierski, W.; Ferris, R.; Edelstein, M.; Chiswell, K.; Kenakin, T. Mol.
Pharmacol. 2009, 75, 490.
7. (a) Singleton, D. H.; Boyd, H.; Steidl-Nichols, J. V.; Deacon, M.; Croot, M. J. D.;
Price, D.; Nettleton, D. O.; Wallace, N. K.; Troutman, M.; Williams, C.; Boyd, J. G. J.
Med. Chem. 2007, 50, 2931; (b) Deacon, M.; Singleton, D. H.; Szalkki, N.;
Pasieczny, R.; Peacock, C.; Price, D.; Boyd, J.; Boyd, H.; Steidl-Nichols, J. V.;
Williams, C. J. Pharmacol. Toxicol. Methods 2007, 55, 255.
Additional evaluation of 36 for dofetilide binding (IC50 = 10 lM),
CYP inhibitions and the reactive metabolite assays suggested no
associated concerns. It was then advanced to dog and monkey PK
studies. Encouragingly, 36 demonstrated low clearance and high
bioavailability in dogs at 1 mg/kg dose. Unfortunately, its monkey
PK was slightly disappointing with 14% bioavailability due to the rel-
atively high clearance (Table 6).
In summary, several classes of acyl analogs of 2 were synthe-
sized and evaluated in antiviral assays and animal PK models.