Bioorganic & Medicinal Chemistry Letters
Discovery of diamide compounds as diacylglycerol acyltransferase 1
(DGAT1) inhibitors
a
a
b
a
Katsumasa Nakajima a, , Myriam April , Jason T. Brewer , Thomas Daniels , Cornelia J. Forster ,
Thomas A. Gilmore a, Monish Jain c, Aaron Kanter a, Youngshin Kwak a, Jingzhou Li a, Les McQuire a,
Michael H. Serrano-Wu a, Ryan Streeper b, Paul Szklennik a, James Thompson b, Bing Wang a
⇑
a Global Discovery Chemistry, Novartis Institutes for Biomedical Research, 100 Technology Square, Cambridge, MA 02139, USA
b Cardiovascular and Metabolism, Novartis Institutes for Biomedical Research, 100 Technology Square, Cambridge, MA 02139, USA
c Metabolism and Pharmacokinetics, Novartis Institutes for Biomedical Research, 250 Massachusetts Avenue, Cambridge, MA 02139, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Diamide compounds were identified as potent DGAT1 inhibitors in vitro, but their poor molecular prop-
erties resulted in low oral bioavailability, both systemically and to DGAT1 in the enterocytes of the small
intestine, resulting in a lack of efficacy in vivo. Replacing an N-alkyl group on the diamide with an N-aryl
group was found to be an effective strategy to confer oral bioavailability and oral efficacy in this lipophilic
diamide class of inhibitors.
Received 24 November 2015
Revised 8 January 2016
Accepted 9 January 2016
Available online xxxx
Ó 2016 Elsevier Ltd. All rights reserved.
Keywords:
DGAT1 inhibitors
Diamide compounds
1,2,4-Triazole
Oral bioavailability
Triglyceride
While triglyceride is an important energy source, its excess
accumulation in the body contributes to the pathogenesis of car-
diovascular disease1 and pancreatitis.2 Inhibition of triglyceride
synthesis can offer a potential therapeutic opportunity towards
treatment of these diseases.
absorption of dietary triglyceride, DGAT1 inhibitors must be
absorbed into enterocytes, but systemic exposure is not required.10
Our high throughput screening using recombinant human
DGAT1 enzyme identified diamide compound 1 as a DGAT1 inhibi-
tor (Table 1). Despite excellent potency (DGAT1 IC50 = 0.007 l
M),11
Triglyceride synthesis involves two biochemical pathways: one
starts from monoacylglycerol, a metabolite of hydrolysis of dietary
triglyceride in the gut. The other starts from glycerol-3-phosphate.
Both routes ultimately provide a common intermediate diacylglyc-
erol, which is then coupled with fatty acyl-CoA to generate triglyc-
eride. This final step is catalyzed by two enzymes known as
diacylglycerol acyltransferases, DGAT13 and DGAT2.4 While DGAT2
knockout mice die shortly after birth,5 DGAT1 knockout mice are
healthy, resistant to diet-induced obesity and have improved insu-
lin sensitivity relative to wild-type.6 This phenotype of DGAT1
knockout mice has led a number of groups to develop DGAT1
inhibitors.7,8
1 was neither bioavailable nor efficacious when dosed orally to rats
at 10 mg/kg,12 suggesting that it does not reach the target in ente-
rocytes. Gut permeability and stability of 1 against CYP enzymes
while it resides in the enterocytes are unlikely the problem based
on Caco-2 and rat liver microsomal (RLM) clearance13 data, respec-
tively. Therefore poor stability and/or solubility of 1 in gastroin-
testinal fluid likely hindered 1 from reaching the target in the
enterocytes. A medicinal chemistry program to optimize 1 into
an orally efficacious DGAT1 inhibitor was then initiated. Although
systemic exposure for analogs of 1 is not required for efficacy, we
nevertheless measured it to confirm that molecules were being
absorbed into enterocytes.
DGAT1 is a membrane-bound protein localized to the endoplas-
mic reticulum. It is ubiquitously expressed, but is most abundant
in the enterocytes of the small intestine where it plays an impor-
tant role in dietary triglyceride uptake.3,9 In order to suppress
Our initial approach was to simply replace the ester groups of 1
with groups that were predicted to be more stable to hydrolytic
degradation. This provided potent DGAT1 inhibitors 2 and 3
(Table 1). In particular, 2 was stable in vitro in simulated gastric
fluid in the presence of pepsin (83 % remained after 1 h of
incubation). Nevertheless, after oral suspension administration
to rats, these analogs still showed poor systemic exposure
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Corresponding author.
0960-894X/Ó 2016 Elsevier Ltd. All rights reserved.