Dihydropyridine neuropeptide Y Y1 receptor antagonists

Article abstract of DOI:10.1016/S0960-894X(01)00761-2

Dihydropyridine 5a was found to be an inhibitor of neuropeptide Y₁ binding in a high throughput ¹²⁵I-PYY screening assay. Structure-activity studies around certain portions of the dihydropyridine chemotype identified BMS-193885 (6e)

Full text of DOI:10.1016/S0960-894X(01)00761-2

Bioorganic & Medicinal Chemistry Letters 12 (2002) 379–382
Dihydropyridine Neuropeptide Y Y1 Receptor Antagonists
Graham S. Poindexter,* Marc A. Bruce, Karen L. LeBoulluec, Ivo Monkovic,
Scott W. Martin, Eric M. Parker, Larry G. Iben, Rachel T. McGovern,
Astrid A. Ortiz, Jennifer A. Stanley, Gail K. Mattson, Michael Kozlowski,
Meredith Arcuri and Ildiko Antal-Zimanyi
Pharmaceutical Research Institute, Bristol-Myers Squibb Co., 5 Research Parkway, Wallingford, CT 06492-7660, USA
Received 13 September 2001; accepted 9 November 2001
Abstract—Dihydropyridine 5a was found to be an inhibitor of neuropeptide Y1 binding in a high throughput 125I-PYY screening
assay. Structure–activity studies around certain portions of the dihydropyridine chemotype identified BMS-193885 (6e) as a potent
and selective Y1 receptor antagonist. In a forskolin-stimulated c-AMP production assay using CHO cells expressing the human Y1
receptor, 6e demonstrated full functional antagonism (Kb=4.5 nM). Compound 6e inhibited NPY-induced feeding in satiated rats
when dosed at 3.0 and 10.0 mg/kg (ip), and also decreased spontaneous overnight food consumption in rats at doses of 10 and 20
mg/kg (ip). # 2002 Elsevier Science Ltd. All rights reserved.
Neuropeptide Y (NPY) is a 36-amino acid peptide,
which was first isolated in 1982 from porcine brain.1
The peptide is a member of a larger peptide family
which also includes peptide YY (PYY), pancreatic pep-
tide (PP), and a non-mammalian fish pancreatic peptide
(PY).2 NPY is very highly conserved in a wide variety of
animal, reptile, and fish species and is found in many
central and peripheral sympathetic neurons. It is the
most abundant peptide observed in mammalian brain
and has long been implicated in the regulation of feed-
ing behavior and energy homeostasis.3À5 To date, NPY
remains the most potent orexigenic agent known.
bitory activity on feeding, although the effect remains
controversial.12,13 More recently, several new Y1
antagonists (LY357897 and J-104870) have appeared
which have reported inhibitory effects on feeding in
rodents and support the involvement of the Y1 receptor
on food intake.14,15
In-house high throughput screening efforts resulted in
the identification of the dihydropyridine derivative 5a
(BMY-20429). The compound was found to be an inhi-
bitor of NPY Y1 binding (Ki=109 nM) and subse-
quently shown to be a competitive Y1 receptor
antagonist. A synthetic program was initiated to more
fully examine structure–activity relationships around
certain portions of the dihydropyridine chemotype. This
communication will describe some of our structure–
activity efforts around the C-3 ester and terminal amine
portions of the molecule.
Currently six different NPY receptor subtypes have
been identified (Y1, Y2, Y4, Y5, and Y6).6,7 Although
recent evidence suggests the Y5 receptor is most closely
associated pharmacologically with the ‘‘feeding recep-
tor’’, it is generally believed that both Y1 and Y5 recep-
tors are involved in the feeding response to NPY.8 Over
the past several years a number of specific and selective,
small molecule Y1 and Y5 receptor antagonists have
been studied and their inhibitory effects on feeding
described (Fig. 1).9À11 With respect to the involvement
of Y1 receptor antagonists in feeding, BIBP 3226 was
the first potent, non-peptidic agent reported with inhi-
The synthesis of C-3 modified dihydropyridines 5 and 6
incorporating either piperazine or piperidine ring func-
tionality on the terminal side chain is shown in Scheme 1.
Reduction of the nitrophenyl substituted dihydropyridines
1 furnished the aniline derivatives 2 that were subsequently
converted to the respective isocyanates 3 by either one of
two methods. The first method employed conditions
described by Alper (conversion of 2 to an intermediate
methyl urethane derivative followed by treatment with B-
chlorocatecholborane).16 Alternatively, careful treat-
*Corresponding author. Fax: +1-203-677-7702; e-mail: graham.
poindexter@bms.com
0960-894X/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00761-2

380
G. S. Poindexter et al. / Bioorg. Med. Chem. Lett. 12 (2002) 379–382
Figure 1. Y1 Receptor antagonists.
Scheme 1. Synthesis of dihydropyridines 5 and 6. (a) Fe, NH4Cl, MeOH; (b) ClCO2Me, pyridine, CH2Cl2; (c) B-chlorocatecholamine, Et3N, THF;
(d) COCl2, THF; (e) 4, CH2Cl2.
ment of 2 with excess phosgene in THF directly furn-
ished the respective isocyanates. These were then con-
densed with the appropriate N-aminopropylpiperazine
or piperidine intermediates 417 to afford the respective
dihydropyridine urea derivatives 5 and 6.
BMY-20429 (5a, R1=CO2Et), larger substituents (5c,
R1=CO2n-Bu and 5d, R1=CO2t-Bu) dramatically
reduced binding affinity. In contrast, substitution at the C-3
position with a smaller methyl substituent (5b, R1=
CO2Me) considerably enhanced binding potency (Ki=12
nM). The small cyano substituent in 5e (R1=CN) was less
potent than 5a, suggesting the ester group contributes to
binding. Interestingly, it should be noted that conversion of
the asymmetric methyl ethyl ester derivative 5a to the
symmetrical bis methyl ester congener 5b not only
enhanced Y1 binding potency but also rendered the C-4
position of the dihydropyridine ring achiral.19
Dihydropyridines 5 and 6 were examined in a competi-
tion binding affinity assay using 125I-PYY as the
radioligand in SK-N-MC cell membranes which
endogenously express the human Y1 receptor.18 The
results are summarized in Tables 1 and 2 for the piper-
azine and piperidine containing dihydropyridines 5a–5n
and 6a–6i, respectively. For the piperazine containing
derivatives 5, substitution at the C-3 ester position on
the dihydropyridine ring had a profound effect on Y1
binding affinity. In comparison to the initial lead ester
Aryl substitution at the N-4 position of the piperazine
ring had a less pronounced effect on binding potency
except for p-phenyl substituents. Rank ordering of the

G. S. Poindexter et al. / Bioorg. Med. Chem. Lett. 12 (2002) 379–382
381
binding affinities for the five Topliss derivatives 5f
(R2=Ph), 5j (R2=3,4-Cl2Ph), 5k (R2=4-ClPh), 5l (R2=4-
MePh), and 5m (R2=4-MeOPh) suggests a detrimental
steric interaction (E4) at the para position.22 Ortho and
meta substituents were well tolerated and in some cases
enhanced binding potency relative to the initial lead 5a
(e.g., 5i, R2=3-HOPh). The simple piperazine 5n
showed considerably less binding affinity, suggesting
substitution at N-4 is important for recognition.
The piperidine derivatives listed in Table 2 displayed Y1
binding potencies in the same range as the piperazines.
Similarly, bis methyl ester substitution enhanced bind-
ing affinity relative to the asymmetric ethyl methyl ester
derivative (6a, R1=CO2Et vs 6b, R1=CO2Me). Sub-
stitutions at the C-4 position on the piperidine ring with
either aryl (6c, R2=2-MeOPh, 6d, R2=3-HOPh, and
6e, R2=3-MeOPh) or alkyl (6h, R2=c-hexyl) sub-
stituents were well tolerated; however, the simple,
unsubstituted piperidine 6i (R2=H) was inactive in the
assay, reflecting similar steric and/or lipophilic demands
as the piperazines at this position.
Table 1. Y1 Binding affinities for piperazine containing dihydropyr-
idines 5a–5n
The piperidine containing dihydropyridine derivative 6e
was selected for further investigation. Scatchard analy-
sis of 6e on the effect of 125I-PYY binding in SK-N-MC
cell membranes suggests the binding inhibition is com-
petitive [6e at 10 nM concentration reduced PYY bind-
ing affinity (Kd of 0.65 vs 0.35 nM) without affecting its
binding capacity (Bmax of 0.16 vs 0.16 pmol/mg pro-
tein)].23 Functional studies in CHO cells expressing the
human Y1 receptor found that 6e antagonized the NPY-
mediated inhibition of forskolin-stimulated c-AMP
accumulation in a competitive manner (Kb=4.5 nM),
indicating the compound is a full functional antago-
nist.24 In other competition binding experiments, 6e
showed no affinity for other cloned human NPY recep-
tor subtypes (Y2, Y4, and Y5, Ki’s >1000 nM).
Compda,b
R1
R2
Y1 (Ki, nM)c
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
CO2Et
CO2Me
CO2n-Bu
CO2t-Bu
CN
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Me
2-MeOPh
2-MeOPh
2-MeOPh
2-MeOPh
2-MeOPh
Ph
2-MePh
2-HOPh
3-HOPh
3,4-Cl2Ph
4-ClPh
105
12
995
1162
684
66
96
108
37
677
322
503
405
>1000
4-MePh
4-MeOPh
H
aStandard reference agent BIBP 3226 displayed Ki of 14.9 nM in this
Y1 binding assay.
bDihydropyridines 5a and 5c–5m are racemic mixtures.
c125I-PYY binding in SK-N-MC cell membranes. The Ki’s were
obtained from a single experiment (n=1) with each point being run in
duplicate.
The compound was further examined in several animal
models of feeding to assess its ability to inhibit food
intake. Administration of 6e, at doses of 10 and 30 mg/
kg (ip), antagonized the increase in food consumption
induced by icv infusion of 10 mg of NPY b y 33Æ13%
and 57Æ11%, respectively, in satiated rats.25 There was
no effect of 6e administered alone on food consumption
when dosed at 10 mg/kg (ip). Additionally, administra-
tion of 6e at 10 and 20 mg/kg (ip) decreased sponta-
neous nocturnal food intake in rats 29Æ6% and
54Æ11%, respectively, relative to vehicle treated con-
trols.15
Table 2. Y1 Binding affinities for piperidine containing dihydropyr-
idines 6a–6i
In summary, dihydropyridine 6e (BMS-193885) is a
potent, selective, and competitive Y1 receptor antago-
nist with the ability to inhibit NPY-induced and spon-
taneous overnight feeding in rats. The dihydropyridine
chemotype as depicted by 5 and 6 represents another
novel class of selective Y1 receptor antagonists with
demonstrated anti-orexigenic properties. The compound
provides an additional example of the potential utility of
Y1 antagonists for the treatment of hyperphagia and
obesity. More detailed examples of 6e and related com-
pounds will be reported in the future.
Compda
R1
R2
Y1 (Ki, nM)b
6a
6b
6c
6d
6e
6f
6g
6h
6i
CO2Et
CO2Me
CO2Me
CO2Me
CO2Me
CO2Me
CO2Me
CO2Me
CO2Me
Ph
Ph
89
10
2-MeOPh
3-HOPh
3-MeOPh
3-PhPh
CH2Ph
c-Hexyl
H
4.1
2.7
3.3
188
84
9.5
523
Acknowledgements
aDihydropyridine 6a is a racemic mixture.
bSee footnote c in Table 1.
We thank Linda I. Callaghan and Herbert L. Smith for
their help and assistance.

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enheimer, S. L.; Gitter, B. D.; Iyengar, S.; Schober, D. A.;
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