Identification of 2-{2-[2-(5-Bromo-2-methoxyphenyl)-ethyl]-3-fluorophenyl}-4, 5-dihydro-1H-imidazole (ML00253764), a Small Molecule Melanocortin 4 Receptor Antagonist That Effectively Reduces Tumor-Induced Weight Loss in a Mouse Model

Article abstract of DOI:10.1021/jm034244g

The melanocortin 4 receptor (MC4R) plays an important role in body weight regulation and energy homeostasis. Administration of peptidic MC4R antagonists (usually by intracerebro ventricular injection) has been shown in the literature to increase body weig

Full text of DOI:10.1021/jm034244g

1602
J . Med. Chem. 2004, 47, 1602-1604
Id en tifica tion of 2-{2-[2-(5-Br om o-2-
m eth oxyp h en yl)-eth yl]-3-flu or o-
p h en yl}-4,5-d ih yd r o-1H-im id a zole
(ML00253764), a Sm a ll Molecu le
Mela n ocor tin 4 Recep tor An ta gon ist
Th a t Effectively Red u ces Tu m or -In d u ced
Weigh t Loss in a Mou se Mod el
F igu r e 1. Elements of the benzamidine scaffold and general-
ized SAR results based on MC4R binding affinity (vide infra).
Ch a r t 1. Benzamidines Identified via HTS and Their
Associated MC4R Binding Affinities15
Tricia J . Vos,*,† Andrei Caracoti,† J ennifer L. Che,†
Mingshi Dai,† Cheryl A. Farrer,† Nancy E. Forsyth,†
Stacey V. Drabic,‡ Robert A. Horlick,‡
Diana Lamppu,‡ David L. Yowe,‡ Suresh Balani,§
Ping Li,§ Hang Zeng,§ Ingrid B. J . K. J oseph,|
Luis E. Rodriguez,| Martin P. Maguire,†
Michael A. Patane,† and Christopher F. Claiborne†
Departments of Medicinal Chemistry,
Molecular & Cellular Pharmacology, and
Drug Metabolism & Pharmacokinetics Millennium
Pharmaceuticals, Inc., 40 Landsdowne Street,
Cambridge, Massachusetts 02139 and
agouti-related protein (AgRP). In the absence of MSH
or upon disruption of receptor function (e.g., MC4R
knock out), hyperphagia and significant weight gain
result.9 Both natural and synthetic MC4R antagonist
peptides (e.g., AgRP,10 HS014,11 and SHU911912) pro-
duce robust chronic effects on feeding and body weight
when administered to rats via intracerebro ventricular
(icv) infusion. While these studies provide important
evidence for considering MC4R antagonism as a strat-
egy to increase body weight, in humans a peripheral or
oral agent is required.13
Our research focuses on the identification of novel
MC4R modulators as possible therapeutics for the
treatment of disease associated involuntary weight
loss.14 Herein, we describe the discovery of a novel small
molecule MC4R antagonist that effectively reduces
tumor-induced weight loss in mice after subcutaneous
(sc) administration.
High-throughput screening (HTS) facilitated the iden-
tification of several benzamidines with moderate MC4R
binding affinity (1-3, Chart 1). These compounds were
selected as a starting point for a lead generation
program. The framework of hits 1-3 was dissected into
four components and each fragment was optimized
(Figure 1). Areas of investigation included (1) substitu-
tion on the aromatic (A) ring, (2) the length and
constitution of the linking moiety between rings A and
B, (3) substituents on the B ring, and (4) the nature of
the amidine ring (C). Compounds with submicromolar
MC4R binding affinity that were determined to be
MC4R antagonists (cAMP assay) were further evaluated
for metabolic stability and CNS exposure following iv
administration in order to identify candidates suitable
for pharmacodynamic studies. A brief summary of the
optimization effort is presented below and the biological
data for select compounds is presented in Table 1.
Initially, MC4R activity was optimized by investigat-
ing the A ring. This work led to the identification of the
5-bromo-2-methoxyphenyl group as a moiety that en-
hances MC4R activity by 2 orders of magnitude relative
to the initial HTS hits (e.g., 4). While the sulfur-
containing linker proved useful for rapid analogue
synthesis, this group is readily oxidized in the presence
of human liver microsomes (data not shown). Analogues
Department of Cancer Chemotherapeutics,
Abbott Laboratories, 100 Abbott Park Road,
Abbott Park, Illinois 60064
Received December 2, 2003
Abstr a ct: The melanocortin 4 receptor (MC4R) plays an
important role in body weight regulation and energy homeo-
stasis. Administration of peptidic MC4R antagonists (usually
by intracerebro ventricular injection) has been shown in the
literature to increase body weight and/or food intake in several
rodent models. We report here the identification of a novel
nonpeptidic MC4R antagonist and its effects on tumor-induced
weight loss in mice following peripheral administration.
The involuntary weight loss that occurs as a conse-
quence of many diseases poses a serious medical prob-
lem. Sarcopenia,1 cancer cachexia,2 rheumatoid arthri-
tis,3 chronic obstructive pulmonary disease,4 congestive
heart failure,5 and hip fractures are prevalent conditions
that are often accompanied by involuntary weight loss.
Patients suffering from these ailments experience in-
creased catabolism of both lean and fat mass, which
exacerbates the anorectic state, thereby negatively
impacting overall health and quality of life.6 Although
estimates show that as many as 12 million individuals
are affected by disease-associated involuntary weight
loss, current treatment options remain limited. Agents
that are used, such as dronabinol and magesterone
acetate, provide only modest benefits and are associated
with a variety of side effects.7
The melanocortin 4 receptor (MC4R) plays an impor-
tant role in body weight regulation and energy homeo-
stasis.8 The signaling of this receptor is a tightly
regulated process that involves activation by the pro-
opiomelanocortin (POMC)-derived melanocyte stimulat-
ing hormones (R-, â-, and γ-MSH) and inactivation by
* To whom correspondence should be addressed. Phone: (617) 551-
8692. E-mail: tricia.vos@mpi.com.
† Department of Medicinal Chemistry.
‡ Department of Molecular and Cellular Pharmacology.
§ Department of Drug Metabolism and Pharmacokinetics.
| Department of Cancer Chemotherapeutics, Abbott Laboratories.
10.1021/jm034244g CCC: $27.50 © 2004 American Chemical Society
Published on Web 02/28/2004

Letters
J ournal of Medicinal Chemistry, 2004, Vol. 47, No. 7 1603
F igu r e 2. Brain concentration vs time profiles of compounds
4-7 after 0.2 mg/kg iv injection of mice. AUC 0-3 h (nM‚h):
7, 1160 ( 330; significantly different from 6, 470 ( 130; 5,
14.4 ( 1.6; and 4, 9.8 ( 1.8 (P < 0.05).
F igu r e 3. Brain and plasma concentration vs time profiles
of 7 after 30 mg/kg sc administration to C57Bl/6 mice. AUC-
(0-inf) (nM‚h): brain, 29 900 ( 15 400; significantly different
from plasma, 8800 ( 5300 (P < 0.05).18
Ta ble 1. Benzamidines and Their Associated MC4R Activitiesa
F igu r e 4. Effect of 7 on body weight changes in CT-26 tumor-
bearing BALB/c mice. Dosing of 7 began on day 2. Average
body weight of the na¨ıve group was 19.2 g (day 1), 19.7 g (day
10), and 19.9 g (day 13). *Statistically significant weight loss
of tumor bearing vs na¨ıve groups (P ) 0.01). **Statistically
significant weight gain of tumor bearing animals treated with
7 vs vehicle (P < 0.001).
a
Measurements are ( SD and represent the average of at least
b
three measurements. Binding affinity measured in a membrane
filtration assay using 125I-[NDP]-R-MSH as radioligand. c Func-
tional antagonism measured by inhibition of cAMP production
induced by [NDP]-R-MSH in a whole cell assay.
was chosen to evaluate the effects of the MC4R antago-
nist 7 on body weight. Disease-induced weight loss in
this cancer model is readily measurable before tumor
load becomes a complicating factor. The results of this
study are shown in Figure 4. Two days post CT-26
inoculation, mice (n ) 10/group) were dosed sc with 7
on a b.i.d. (16 mg/kg per dose) schedule for the duration
of the study. Weight loss in tumor-bearing (TB) mice
vs na¨ıve controls was first noted on day 10 (0.5 g) and
became statistically significant (P ) 0.01)21 by day 13.22
Interestingly, the TB animals receiving drug weighed
2.5 g more than the untreated vehicle-dosed group (P
) 0.0003) and 2 g more than na¨ıve controls on day 10.
The drug-treated TB animals on day 13 were 2 g heavier
than the untreated TB vehicle control group (P <
0.0001) and 1 g heavier than the na¨ıve mice. These
results suggest that the MC4R antagonist 7 is effective
in reducing the magnitude of cancer-induced weight loss
in this model. A more comprehensive understanding of
the effects of compound in na¨ıve mice, the source of
weight loss protection (fat vs lean body mass), and
potential changes in food intake are needed but were
not within the scope of this initial plan.
of 4, where the thiomethyl ether group is replaced by
an ethylene unit, are approximately equipotent MC4R
antagonists (cf., 4 and 5) that show improved metabolic
stability. For example, compounds 4 and 5 were incu-
bated with human liver microsomes and after a 60 min
exposure, 11% of 4 was detected, whereas 70% of 5
remained.16
The benzamidines 4-7 were administered iv to mice
in order to evaluate their CNS exposure. All tetrahy-
dropyrimidines dosed (e.g., 4 and 5) were nearly unde-
tectable in the brain (Figure 2).17 Dihydroimidazole 6
had low but detectable brain exposure while the fluoro-
substituted analogue 7 showed significantly enhanced18
brain exposure with a concomitant increase in MC4R
antagonism.19
Benzamidine 7 was also administered to mice sc at
several doses (3, 10, or 30 mg/kg), and plasma and brain
concentration profiles were evaluated (Figure 3). Since
7 achieved brain concentrations in excess of its func-
tional MC4R IC50 for longer than 6 h following a sc dose
of 30 mg/kg, this compound was chosen for evaluation
in a mouse efficacy model.
In summary, a novel class of small molecule MC4R
antagonists has been identified and optimized for
potency, metabolic stability, and CNS penetration fol-
A CT-26-derived mouse (BALB/c) xenograft model20

1604 J ournal of Medicinal Chemistry, 2004, Vol. 47, No. 7
Letters
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Ackn owledgm en t. The authors thank Nelson Troupe
and Ashok Patil for assistance with compound purifica-
tion, Dun-Xu Mu for PK studies, and J oanne Nguyen
for bioanalytical support.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and characterization data for compounds 4-7; meth-
ods for animal studies described in Figures 2-4. This material
is available free of charge via the Internet at http://pubs.
acs.org.
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J M034244G