Discovery of Novel Indoline Cholesterol Ester Transfer Protein Inhibitors (CETP) through a Structure-Guided Approach

Article abstract of DOI:10.1021/acsmedchemlett.5b00404

Using the collective body of known (CETP) inhibitors as inspiration for design, a structurally novel series of tetrahydroquinoxaline CETP inhibitors were discovered. An exemplar from this series, compound 5, displayed potent in vitro CETP inhibition and was efficacious in a transgenic cynomologus-CETP mouse HDL PD (pharmacodynamic) assay. However, an undesirable metabolic profile and chemical instability hampered further development of the series. A three-dimensional structure of tetrahydroquinoxaline inhibitor 6 was proposed from ¹H NMR structural studies, and this model was then used in silico for the design of a new class of compounds based upon an indoline scaffold. This work resulted in the discovery of compound 7, which displayed potent in vitro CETP inhibition, a favorable PK-PD profile relative to tetrahydroquinoxaline 5, and dose-dependent efficacy in the transgenic cynomologus-CETP mouse HDL PD assay.

Full text of DOI:10.1021/acsmedchemlett.5b00404

Letter
pubs.acs.org/acsmedchemlett
Discovery of Novel Indoline Cholesterol Ester Transfer Protein
Inhibitors (CETP) through a Structure-Guided Approach
Jonathan E. Wilson,*,† Ravi Kurukulasuriya,† Mikhail Reibarkh,‡ Maud Reiter, Aaron Zwicker,
Kake Zhao,† Fengqi Zhang,† Rajan Anand,† Vincent J. Colandrea, Anne-Marie Cumiskey,§
Alejandro Crespo,‡ Ruth A. Duffy,§ Beth Ann Murphy,§ Kaushik Mitra,∥ Douglas G. Johns,⊥
Joseph L. Duffy,† and Petr Vachal†
‡
†Department of Medicinal Chemistry and Department of Structural Chemistry, Merck Research Laboratories, Merck & Co, Inc.,
P.O. Box 2000, Rahway, New Jersey 07065, United States
∥
⊥
§Department of Pharmacology, Department of Drug Metabolism and Pharmacokinetics, and Department of Biology, Merck
Research Laboratories, Merck & Co, Inc., P.O. Box 2000, Kenilworth, New Jersey 07033, United States
S
* Supporting Information
ABSTRACT: Using the collective body of known (CETP) inhibitors as inspiration for design, a structurally novel series of
tetrahydroquinoxaline CETP inhibitors were discovered. An exemplar from this series, compound 5, displayed potent in vitro
CETP inhibition and was efficacious in a transgenic cynomologus-CETP mouse HDL PD (pharmacodynamic) assay. However,
an undesirable metabolic profile and chemical instability hampered further development of the series. A three-dimensional
1
structure of tetrahydroquinoxaline inhibitor 6 was proposed from H NMR structural studies, and this model was then used in
silico for the design of a new class of compounds based upon an indoline scaffold. This work resulted in the discovery of
compound 7, which displayed potent in vitro CETP inhibition, a favorable PK−PD profile relative to tetrahydroquinoxaline 5,
and dose-dependent efficacy in the transgenic cynomologus-CETP mouse HDL PD assay.
KEYWORDS: CETP inhibition, cholesterol ester transfer protein, HDL, indoline, tetrahydroquinoxaline
ester transfer protein (CETP), a plasma protein that facilitates
the exchange of cholesterol esters from HDL particles to LDL
particles and triglycerides from LDL to HDL. Thus, inhibition
of CETP would augment cholesterol excretion by increasing
the HDL to LDL ratio and could hypothetically provide an
opportunity for the treatment of cardiovascular disease via
increased cholesterol efflux. Because of the prevalence of health
conditions caused by cardiovascular disease this hypothesis is
currently being tested in the clinic by multiple organiza-
tions.10−13
igh levels of plasma low-density lipoprotein (LDL) are
Hclinically associated with atherosclerosis and its con-
sequences, which can include coronary heart disease, stroke,
and peripheral vascular disease.1,2 Despite the successful
development of therapies targeting cholesterol absorption,
biosynthesis, and clearance, atherosclerosis remains a serious
public health issue.3 As such the development of additional,
novel therapies for cardiovascular disease is needed.
In contrast to LDL, high plasma levels of high-density
lipoprotein (HDL) are correlated with a cardioprotective
effect.4 This may be attributed to higher hepatic clearance of
cholesterol via HDL relative to LDL through a process known
as reverse cholesterol transport.5−7 However, HDL has
antioxidant and anti-inflammatory properties that may also
contribute to its antiatherogenic effects.8,9 The balance and
interplay between LDL and HDL is influenced by cholesterol
Due to our continuing interest in new therapies for
cardiovascular disease, including CETP inhibition, we initiated
Received: October 15, 2015
Accepted: January 4, 2016
© XXXX American Chemical Society
A
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Letter
an effort to identify structurally novel CETP inhibitors. We
were inspired by the structural homology of the CETP
inhibitors 1, 2, and 3 that had been described by Pfizer,
Pharmacia, and Johnson and Johnson for two reasons.14−16
First, these three classes of compounds had all demonstrated
efficacy in vivo. Second, we sought to investigate diverse
chemical matter that would be complementary to Merck’s
established class of oxazolidinone CETP inhibitors, exemplified
by the clinical compound, 4, anacetrapib (Figure 1).17 From
Figure 3. Proposed structures of oxidative metabolites observed after
incubation of compound 5 with human liver microsomes.
vivo in a transgenic cynomologus-CETP mouse pharmacody-
namic assay, it displayed highly nonlinear PK.21,22 These
observations lead us to view the pharmacodynamic effects of 5
with skepticism.
We first sought to address the oxidative liabilities of the core
by stabilizing the tetrahydroquinoxaline ring system through
introduction of a heteroatom or an electron withdrawing
substituent in the aromatic portion of the core. Unfortunately
these strategies generally led to a reduction in potency and little
or no change in the metabolic or chemical stability of the
compounds.23 Due to concerns about the generation of reactive
intermediates, the potential difficulties of progressing a
chemically unstable compound, and our inability to stabilize
the tetrahydroquinoxaline core without a substantial loss of
potency we chose to re-engineer this series.
Figure 1. Structures used as inspiration for design of structurally novel
CETP inhibitors.
this exercise we designed a novel series of substituted
tetrahydroquinoxalines that bear elements of the four
aforementioned classes of CETP inhibitors, while at the same
time being distinct from each of them. This investigation led to
the discovery of compound 5, which displayed promising in
vitro CETP inhibition and reasonable rat PK (Figure 2).18
Interestingly, the optimal stereochemistry at C-2 of the
tetrahydroquinoxaline is opposite to that found in tetrahy-
droquinoline 3.19
Faced with this challenge, we turned our attention to
elucidation of the three-dimensional structure of compounds
like 5 with the hope that structural insight would spur the
design of novel scaffolds that would mimic the three-
dimensional chemical shape of the tetrahydroquinoxalines but
would be devoid of the metabolic and chemical instability
1
inherent to this core. Stereochemical analysis by H NMR
revealed a dependence of the molecular conformation on the
relative stereochemistry of C-2 and the 1,1,1-trifluoropropanol
side chain that allowed for the assignment of the absolute
stereochemistry of compound 6. This led to the proposal of a
U-shaped three-dimensional structure in which the C-2
aromatic group is in a pseudoaxial position and the N-benzyl
group lies parallel to the C-2 group on the same face of the
tetrahydroquinoxaline core (Figure 4).24
Figure 2. In vitro and PK properties of tetrahydroquinoxaline CETP
inhibitor 5.
During the course of this work we discovered that compound
5, analogues of 5, and tetrahydroquinoxaline intermediates en
route to 5 would gradually oxidize to the monocationic and
aromatic dicationic quinoxalinium species when stored under
ambient conditions over a timespan of days. These degradation
products could be observed by LCMS. Additionally, metabolite
identification studies following incubation of 5 in human liver
microsomes showed extensive oxidative metabolism leading to
dealkylation and the formation of possible reactive intermedi-
ates (Figure 3).20 Although 5 was found to be efficacious in
Figure 4. Proposed three-dimensional structure of 6.
B
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Using the proposed solution-phase conformation of the
tetrahydroquinoxalines as inspiration, we designed molecules
that could adopt the U-shape that we speculated was critical for
CETP inhibition and that would lack the metabolic and
chemical instability of the tetrahydroquinoxaline core. Although
we were well aware that the solution-phase conformation may
not be representative of the active conformation of the
tetrahydroquinoxaline inhibitors when bound to CETP, we
nevertheless chose to pursue this strategy in the hope that we
would uncover novel CETP inhibitor chemotypes. Using this
strategy, we designed the 3,3-disubstituted indoline 7, which
overlaid well with the tetrahydroquinoxaline inhibitor 6 fixed in
the proposed U-shaped three-dimensional structure arrived at
from NMR structural studies (Figure 5).25 Compounds of this
Table 1. 3,3-Disubstituted Indoline CETP Inhibitor SAR
Figure 5. Overlay of tetrahydroquinoxaline 6 with 3,3-disubstituted
indoline 7 (hydrogens removed for clarity).
type should not inherently be prone to the oxidative chemical
instability associated with the tetrahydroquinoxaline core
because the aromatization process that results from oxidation
of 7 is not possible on an indoline scaffold in which the 3-
position is a fully substituted quaternary carbon atom.
In order to rapidly survey a broad range of substituents at the
C-3 position of the indoline core, compounds were evaluated
for CETP inhibition first as a mixture of diastereomers at C-3,
and the results are presented in Table 1. To our delight,
indoline 8 afforded significant intrinsic CETP inhibitory
potency with an IC50 of 69 nM. Truncation of the arene at
R1 or R2 completely ablated CETP activity (compounds 9 and
10). Substitution at the 3-position of the R1 arene was
preferred over unsubstituted, 2-substituted, and 4-substituted
benzenes (compounds 11, 12, and 13). Multiple 3-substituted
benzenes and heteroarenes were explored at R1. However,
none of these substituents were found to be superior to the 3-
trifluoromethoxy group (compounds 14 through 19). Attempts
to transpose the 3,5-bis-trifluoromethylbenzene group of
anacetrapib and torcetrapib onto the indoline core were
unsuccessful (compounds 20 and 21). The 3-trifluoromethox-
ybenzene was again found to be optimal at R2 despite attempts
to find suitable replacements (compounds 22 through 27).
Finally, 4-, 5-, 6-, and 7-substituted indolines were explored, but
the unsubstituted core was found to be superior to those that
were surveyed with respect to CETP inhibition (compounds 28
through 34).
a
The compounds are a 1:1 mixture of diastereomers (C-2 stereocenter
b
is racemic). This in vitro assay measures the ability of the compounds
to inhibit the CETP mediated transfer of [3H]-cholesterol or [3H]-
triolein from LDL to HDL. The assay was performed using
endogenous CETP in 95% human serum (HS), n = 1. Data for the
same in vitro assay run in 2% human serum are available in the
Supporting Information.
inhibition as would be expected from consideration of overlays
with compound 6. The remaining two diastereomers, 36 and
37, were also considerably less potent. From this data it appears
that the quaternary stereocenter is the primary driver for
potency (7 and 36 versus 35 and 37), while the alcohol
stereochemistry has a less of an impact on potency (7 versus
36). In the CETP RTA in vitro assay in 95% human serum
compound 7 is superior to compounds 2 and 3 (2, IC50 = 197
nM; 3, IC50 = 295 nM) and comparable with the clincical
The diastereomers and enantiomers of compound 8 were
synthesized and resolved to determine the impact of stereo-
chemistry on CETP inhibitory potency (Table 2). The C-3
diastereomers, 7 and 35, show a substantial difference in CETP
C
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In summary, a novel class of CETP inhibitors based on an
indoline scaffold has been discovered.28,29 The indoline series
was designed from in silico overlays with tetrahydroquinoxaline
CETP inhibitor 6, of which a three-dimensional structure was
Table 2. Effect of Stereochemistry on CETP Potency
1
proposed from structural information derived from H NMR
studies. Indoline 7 is a potent inhibitor of CETP in vitro,
displays improved metabolic and chemical stability relative to
its progenitor, tetrahydroquinoxaline 5, and shows dose-
dependent efficacy in the cynomologus-CETP mouse HDL
pharmacodynamic assay. Furthermore, the three-dimensional
structures of 6 and 7 proposed herein may be a useful template
from which to design additional novel classes of CETP
inhibitors.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acsmedchem-
lett.5b00404.
Experimental procedures and characterization for com-
pounds 5 through 37, a description of the in vitro assay,
and data for compounds 5−37 in the CETP RTA assay
run in 2% human serum (PDF)
a
This in vitro assay measures the ability of the compounds to inhibit
the CETP mediated transfer of [3H]-cholesterol oleate or [3H]-
triolein from LDL to HDL. The assay was performed using
endogenous CETP in 95% human serum (n = 1). Data for the
same assay run in 2% human serum are available in the Supporting
Information.
AUTHOR INFORMATION
Corresponding Author
*E-mail: jonathan_wilson@merck.com.
■
CETP inhibitors 1 and 4 (1, IC50 = 45 nM; 4, IC50 = 53
nM).15,16
The CETP inhibitory action of the indoline series was further
confirmed by the ability of 7 to increase HDL-cholesterol in an
exposure-dependent manner when orally administered to
cynomologus-CETP transgenic mice (Figure 6).21,26 This
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors gratefully acknowledge Dr. Christopher Sinz, Dr.
Christopher Plummer, and Eric Meade for reviewing the article
and providing comments.
ABBREVIATIONS
■
CETP, cholesterol ester transfer protein; HDL, high density
lipoprotein; PPB, plasma protein binding; HS, human serum;
LDL, low density lipoprotein; PK, pharmacokinetic; PD,
pharmacodynamic
REFERENCES
■
(1) Kearney, P. M.; Blackwell, L.; Collins, R.; Keech, A.; Simes, J.;
Peto, R.; Armitage, J.; Baigent, C. Efficacy of cholesterol-lowering
therapy in 18686 people with diabetes in 14 randomised trials of
statins: A meta-analysis. Lancet 2008, 371, 117−125.
Figure 6. Elevation of HDL-C 4 h postdose in cynomologus-CETP
transgenic mice orally administered compound 7.
(2) Baigent, C.; Keech, A.; Kearney, P. M.; Blackwell, L.; Buck, G.;
Pollicino, C.; Kirby, A.; Sourjina, T.; Peto, R.; Collins, R.; Simes, J.
Efficacy and safety of cholesterol-lowering treatment: Prospective
metaanalysis of data from 90,056 participants in 14 randomised trials
of statins. Lancet 2005, 366, 1267−1278.
exposure-dependent PD effect of 7, which displays good
pharmacokinetic properties in a rat (dose 0.15 mg/kg: Cl =
36.0 mL/min/kg; t1/2 = 4.76 h; Vdss = 6.70 L/kg) is in stark
contrast to 5, which exhibited an unusual exposure−PD
relationship. This difference is most likely due to the increased
chemical and metabolic stability of 7 relative to 5.
Unfortunately, the in vivo efficacy of 7 can not be directly
compared with compounds 1−4 because HDL measurements
from the cyno-CETP mouse PD assay were recorded at
different time points for the respective sets of compounds.27
However, the PK profile, promising in vivo efficacy, and
structural novelty of the indoline series render them an
attractive starting point for the development of future CETP
inhibitors.
(3) World Health Organization Cardiovascular DiseasesFact Sheet
No. 317. http://www.who.int/en/ (January 2015).
(4) Singh, I. M.; Shishehbor, M. H.; Ansell, B. J. High density
lipoprotein as a therapeutic target. J. Am. Med. Assoc. 2007, 298, 786.
(5) Bruce, C.; Chouinard, R. A., Jr.; Tall, A. R. Plasma lipid transfer
proteins, high-density lipoproteins, and reverse cholesterol transport.
Annu. Rev. Nutr. 1998, 18, 297−330.
(6) Pieters, M. N.; Schouten, D.; Berkel, T. J. C. Van. In Vitro and In
Vivo Evidence for the Role of HDL in Reverse Cholesterol Transport.
Biochim. Biophys. Acta, Mol. Basis Dis. 1994, 1225, 125−134.
(7) The association between HDL and reverse cholesterol transport
with cardiovascular outcomes is disputed. For a discussion of this, see:
D
DOI: 10.1021/acsmedchemlett.5b00404
ACS Med. Chem. Lett. XXXX, XXX, XXX−XXX

ACS Medicinal Chemistry Letters
Letter
Levinson, S. S.; Wagner, S. G. Implications of reverse cholesterol
transport: Recent studies. Clin. Chim. Acta 2015, 15, 154−161.
(8) Barter, P. J.; Nicholls, S.; Rye, K.-A.; Anantharamaiah, G. M.;
Navab, M.; Fogelman, A. M. Antiinflammatory properties of HDL.
Circ. Res. 2004, 95, 764−772.
the vehicle group. See ref 17 and the following reference for further
details of the pharmacodynamic assay. Marotti, K. R.; Castle, C. K.;
Murray, R. W.; Rehberg, E. F.; Polites, H. G.; Melchior, G. W. The
role of cholesteryl ester transfer protein in primate apolipoprotein A-I
metabolism. Insights from studies with transgenic mice. Arterioscler.,
Thromb., Vasc. Biol. 1992, 12, 736−44.
(22) Compound 5 did not show the expected dose−exposure
relationship when dosed orally at 1, 3, and 10 mg/kg in the transgenic
cynomolgus-mouse PD assay. The exposures were 1.3, 1.8, and 1.9
μM, respectively.
(9) Salman Bandeali, S.; Farmer, J. High-density lipoprotein and
atherosclerosis: The role of antioxidant activity. Curr. Atheroscler. Rep.
2012, 14, 101−107.
(10) Rader, D. J.; deGoma, E. M. Future of cholesteryl ester transfer
protein inhibitors. Annu. Rev. Med. 2014, 65, 385−403.
(23) Both isomers of the 1,2,3,4-tetrahydropyrido[2,3-b]pyrazine
core were prepared in addition to one isomer of the 1,2,3,4-
tetrahydropyrido[3,4-b]pyrazine core. Only one isomer of 1,2,3,4-
tetrahydropyrido[2,3-b]pyrazine showed CETP activity, but none of
the compounds showed improved chemical or metabolic stability.
Fluoro- and trifluoromethyl-quinoxalines were also explored but were
not found to have improved stability.
(11) Mantlo, N. B.; Escribano, A. Update on the discovery and
development of cholesteryl ester transfer protein inhibitors for
reducing residual cardiovascular risk. J. Med. Chem. 2014, 57, 1−17.
(12) Sikorski, J. A. Oral cholesteryl ester transfer protein (CETP)
inhibitors: A potential new approach for treating coronary artery
disease. J. Med. Chem. 2006, 49, 1.
(13) Johns, D. G.; Duffy, J. L.; Fisher, T.; Hubbard, B. K.; Forrest, M.
J. On- and off-Target pharmacology of torcetrapib: Current under-
standing and implications for the structure activity relationships
(SAR), discovery and development of cholesteryl ester-transfer protein
(CETP) inhibitors. Drugs 2012, 72, 491−507.
(14) DeNinno, M. P.; Magnus-Aryitey, G. T.; Ruggeri, R. B.; Wester,
R. T. 4-Carboxy-amino-2-substituted-1,2,3,4-tetrahydro-quinolines as
CETP inhibitors. Patent Application WO2000/17164, March 30,
2000.
(15) Reinhard, E. J.; Wang, J. L.; Durley, R. C.; Fobian, Y. M.;
Grapperhaus, M. L.; Hickory, B. S.; Massa, M. A.; Norton, M. B.;
Promo, M. A.; Tollefson, M. B.; Vernier, W. F.; Connolly, D. T.;
Witherbee, B. J.; Melton, M. A.; Regina, K. J.; Smith, M. E.; Sikorski, J.
A. Discovery of a simple picomolar inhibitor of cholesteryl ester
transfer protein. J. Med. Chem. 2003, 46, 2152−2168.
(16) Kuo, G.-H.; Rano, T.; Pelton, P.; Demarest, K. T.; Gibbs, A. C.;
Murray, W. V.; Damiano, B. P.; Connelly, M. A. Design, synthesis, and
biological evaluation of (2R,αS)-3,4-Dihydro-2-[3-(1,1,2,2-
tetrafluoroethoxy)phenyl]-5-[3-(trifluoromethoxy)-phenyl]-α-(tri-
fluoromethyl)-1(2H)-quinoline-ethanol as a potent and orally active
cholesteryl ester transfer protein inhibitor. J. Med. Chem. 2009, 52,
1768−1772.
(17) Smith, C. J.; Ali, A.; Hammond, M. L.; Li, H.; Lu, Z.;
Napolitano, J.; Taylor, G. E.; Thompson, C. F.; Anderson, M. S.;
Chen, Y.; Eveland, S. S.; Guo, Q.; Hyland, S. A.; Milot, D. P.; Sparrow,
C. P.; Wright, S. D.; Cumiskey, A.-M.; Latham, M.; Peterson, L. B.;
Rosa, R.; Pivnichny, J. V.; Tong, X.; Xu, S. S.; Sinclair, P. J. Biphenyl-
substituted oxazolidinones as cholesteryl ester transfer protein
inhibitors: Modifications of the oxazolidinone ring leading to the
discovery of anacetrapib. J. Med. Chem. 2011, 54, 4880−4895.
(18) Eveland, S. S.; Milot, D. P.; Guo, Q.; Chen, Y.; Hyland, S. A.;
Peterson, L. B.; Jezequel-Sur, S.; O’Donnell, G. T.; Zuck, P. D.; Ferrer,
M.; Strulovici, B.; Wagner, J. A.; Tanaka, W. K.; Hilliard, D. A.;
Laterza, O.; Wright, S. D.; Sparrow, C. P.; Anderson, M. S. A high-
precision fluorogenic cholesteryl ester transfer protein assay
compatible with animal serum and 3456-well assay technology. Anal.
Biochem. 2007, 368, 239−249.
(24) The details of the NMR studies can be found in the Supporting
Information.
(25) Ensemble conformations for both compounds 6 and 7 were
generated using omega (openeye scientific software); Hawkins, P. C.
D.; Skillman, A. G.; Warren, G. L.; Ellingson, B. A.; Stahl, M. T. J.
Chem. Inf. Model. 2010, 50, 572−584. and overlaid using rocs
(openeye scientific software); Hawkins, P. C. D.; Skillman, A. G.;
Nicholls, A. J. Med. Chem. 2007, 50, 74. The best overlaid pair was
then refined with the flexible alignment module of the MOE package
(Molecular Operating Environment, 2014.09; Chemical Computing
Group Inc., 1010 Sherbooke St. West, Suite #910, Montreal, QC,
Canada, H3A 2R7, 2015). Figures 4 and 5 were rendered using
PyMOL (The PyMOL Molecular Graphics System, Version 1.7.4
Schrodinger, LLC)..
̈
(26) The data in Figure 6 for the 2 mg/kg dose and the 10 and 30
mg/kg doses were collected on different days. A positive control,
structurally related to anacetrapib (CETP RTA IC50 in 95% human
serum = 43 nM) was run in both instances. The positive control
increased HDL by 67% on the day the 2 mg/kg dose was
administered. On the day of the 10 and 30 mg/kg dosing, the positive
control increased HDL by 191%.
(27) HDL measurements in the cyno-CETP mouse PD assay
conducted at Merck for compound 7 were measured at 4 h postdose,
while measurements for compounds 2 and 3 were taken at 18 h
postdose (compound 2, 30 mpk PO dose, −20% change in HDL 18 h
postdose relative to vehicle; compound 3, 30 mpk PO dose, +4.2%
change in HDL 18 h postdose relative to vehicle).
(28) Wilson, J. E.; Vachal, P.; Kurukulasuriya, R. 3,3′-Disubstituted
Indolines as Inhibitors of Cholesterol Ester Transfer Protein. PCT Int.
Appl., WO2015054088, April 16, 2015.
(29) Anand, R.; Colandrea, V. J.; Reiter, M.; Vachal, P.; Zwicker, A.;
Wilson, J. E.; Zhang, F.; Zhao, K. Benzopiperazine Derivatives As
CETP Inhibitors. PCT Int. Appl. WO2013028382 A1, December 4,
2014.
(19) The remaining three diastereomers were prepared and the
CETP RTA IC50 values for those compounds are as follows (alcohol
stereochemistry is listed first followed by the C-2 stereochemistry):
(R,S)-isomer = 3273 nM; (S,S)-isomer = 716 nM; (S,R)-isomer = 60
nM.
(20) Compound 5 (10 μmol) was incubated with C57 mouse liver
microsomes (1 mg/mL protein) for 60 min at 37 °C. Structure
assignments are tentative, based on LC−MS/MSE data. The elemental
compositions of the metabolites were confirmed by high-resolution
mass analysis (QTOF).
(21) Compounds or noncompound-containing vehicle were orally
administered to transgenic mice that overexpress the cynomolgus
cholesteryl ester transfer protein. HDL-cholesterol was measured from
plasma collected at 4 h postdose using a commercially available kit
(Wako Diagnostics). The effect of the test compound on HDL-
cholesterol is expressed as the percent elevation compared to that of
E
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