Discovery of a potent parenterally administered factor XIa inhibitor with hydroxyquinolin-2(1H)-one as the P2′ moiety

Article abstract of DOI:10.1021/acsmedchemlett.5b00066

Structure-activity relationship optimization of phenylalanine P1′ and P2′ regions with a phenylimidazole core resulted in a series of potent FXIa inhibitors. Introducing 4-hydroxyquinolin-2-one as the P2′ group enhanced FXIa affinity and metabolic stability. Incorporation of an N-methyl piperazine amide group to replace the phenylalanine improved both FXIa potency and aqueous solubility. Combination of the optimization led to the discovery of FXIa inhibitor 13 with a FXIa K_i of 0.04 nM and an aPTT EC_2x of 1.0 μM. Dose-dependent efficacy (EC₅₀ of 0.53 μM) was achieved in the rabbit ECAT model with minimal bleeding time prolongation.

Full text of DOI:10.1021/acsmedchemlett.5b00066

Letter
pubs.acs.org/acsmedchemlett
Discovery of a Potent Parenterally Administered Factor XIa Inhibitor
with Hydroxyquinolin-2(1H)‑one as the P2′ Moiety
Zilun Hu,* Pancras C. Wong, Paul J. Gilligan, Wei Han, Kumar B. Pabbisetty, Jeffrey M. Bozarth,
Earl J. Crain, Timothy Harper, Joseph M. Luettgen, Joseph E. Myers, Jr., Vidhyashankar Ramamurthy,
Karen A. Rossi, Steven Sheriff, Carol A. Watson, Anzi Wei, Joanna J. Zheng, Dietmar A. Seiffert,
Ruth R. Wexler, and Mimi L. Quan
Research and Development, Bristol-Myers Squibb, Princeton, New Jersey 08543, United States
S
* Supporting Information
ABSTRACT: Structure−activity relationship optimization of phenylalanine P1′ and P2′
regions with a phenylimidazole core resulted in a series of potent FXIa inhibitors. Introducing
4-hydroxyquinolin-2-one as the P2′ group enhanced FXIa affinity and metabolic stability.
Incorporation of an N-methyl piperazine amide group to replace the phenylalanine improved
both FXIa potency and aqueous solubility. Combination of the optimization led to the
discovery of FXIa inhibitor 13 with a FXIa Ki of 0.04 nM and an aPTT EC2x of 1.0 μM. Dose-
dependent efficacy (EC50 of 0.53 μM) was achieved in the rabbit ECAT model with minimal
bleeding time prolongation.
KEYWORDS: Thrombosis, factor XIa, anticoagulant
hrombosis remains a primary cause of cardiovascular
morbidity and mortality. The established anticoagulants,
T
such as injectable heparin and warfarin, suffer from enhanced
risk of bleeding and narrow therapeutic index.1−3 The newer
anticoagulants, including apixaban, rivaroxaban, edoxaban, and
dabigatran, primarily target direct factor Xa (FXa) or thrombin
inhibition, respectively, which belong to the common pathway
in the coagulation cascade. These agents have shown an
improved efficacy and bleeding safety profile.4−9 Factor XIa
(FXIa) is positioned upstream in the coagulation cascade and is
involved in the amplification of thrombin production. Genetic
evidence suggests FXIa could be an antithrombotic target with
net clinical benefit.10 FXI deficient mice do not exhibit
prolonged provoked bleeding times.11−13 Deficiency of
human FXI is only associated with a mild bleeding diathesis.
Inhibiting FXIa could provide a reduction in thrombin to a
level sufficient to impede occlusive thrombosis, yet allow
enough thrombin generation to support hemostasis.14 Inhib-
ition of FXIa has been demonstrated to be a viable
antithrombotic approach with an improved benefit to risk
ratio in preclinical animal models,15,16 and recently in a clinical
phase II proof of concept study with FXIa antisense
oligonucleotide,17 with minimal effects on provoked bleeding
time.
Figure 1. FXIa inhibitors previously reported by our group.
1,4-tranexamic amide P1 in compound 2 identified neutral
FXIa inhibitor 3.21 Compound 3 has a Ki 3.7 nM in the FXIa
enzyme binding assay. It exhibits an EC2x of 19 μM in vitro
anticoagulant activity in the activated partial thromboplastin
time (aPTT) clotting assay. Herein, we describe the continued
SAR optimization at the phenylalanine P1 prime (P1′) and P2
prime (P2′) regions with compound 3 to further improve
potency, stability, and solubility toward the discovery of a
potent and efficacious parenteral FXIa inhibitor.
We have reported a reversible, small molecule FXIa inhibitor
with a tetrahydroquinoline core (1, Figure 1), which
demonstrated antithrombotic efficacy without prolonging
bleeding time in rabbit antithrombotic efficacy and bleeding
models.18,19 We have also reported the discovery of a series of
potent FXIa inhibitors (2) containing a phenylimidazole core.20
Structure−activity relationship (SAR) efforts to replace basic
Received: February 5, 2015
Accepted: April 8, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acsmedchemlett.5b00066
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ACS Medicinal Chemistry Letters
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Possible cleavage of the P2′ methylcarbamate in 3 to release
an aniline moiety was envisioned to be a potential safety issue.
One of the approaches to optimize P2′ was to utilize tied-back
fused ring systems to replace the aniline methyl carbamate. As
shown in Table 1, changing P2′ from methyl carbamate in 3 to
Table 2. SAR of Aspartate Amide Analogues
Table 1. P2′ Tied-Back SAR
a
Ki values were obtained from human enzyme and were averaged from
b
multiple determinations (n = 2), as described in ref 20. Activated
partial thromboplastin time (aPTT) in vitro clotting assay was
c
performed in human plasma, as described in ref 20. Amorphous, 50
d
mM pH 6.5 phosphate buffer. Human liver microsome half-life
(HLM T1/2) of compounds were determined by following the method
described in ref 22.
a
Ki values were obtained from human enzyme and were averaged from
b
multiple determinations (n = 2), as described in ref 20. Activated
partial thromboplastin time (aPTT) in vitro clotting assay was
c
performed in human plasma, as described in ref 20. Human liver
microsome half-life (HLM T1/2) of compounds were determined by
following the method described in ref 22.
dihydroquinolinone in 4 and quinolinone in 5 retained most of
the FXIa enzyme binding and in vitro anticoagulant aPTT
clotting potencies. From molecular modeling, it was envisioned
that additional affinity could be achieved by the interaction
between the quinolinone moiety and tyrosine 143 (Tyr 143) of
the enzyme. Indeed, introducing a hydroxyl group at the 4-
position of quinolinone, such as in analogues 6 and 7, improved
both FXIa binding and aPTT potency significantly with FXIa Ki
of 0.5 and 0.32 nM, and aPTT EC2x of 9.1 and 7.2 μM,
respectively. Human liver microsome half-life assay indicated
the analogues with ethylene linker, such as 5, 6, and 7 of the P1
groups, had poor metabolic stability. Incorporation of the
ethenyl linker in compound 8 improved FXIa Ki (0.18 nM)
while having similar aPTT (EC2x 11 μM) potency and
improved human liver microsome half-life.
Phenylalanine replacement SAR was explored to improve in
vitro anticoagulant activity and aqueous solubility by the
incorporation of polar groups. As listed in Table 2, changing
the R group from analogue of phenyl alanine (3) to aspartate
analogue of morpholine amide (9) afforded a very potent
inhibitor with a FXIa Ki of 0.7 nM and an aPTT EC2x of 7.4
μM. The X-ray crystal structure23 (Figure 2) indicated that 9
bound to the FXIa active site with the chlorophenyl tetrazole fit
Figure 2. X-ray crystal structure of 9 in FXIa. Final model is shown
with initial Fo-Fc map contoured at 2.5 rmsd. Hydrogen bonds are
shown as a series of prolate ellipsoids.
in the S1 pocket having an edge-to-face interaction between the
chlorophenyl and Tyr 228. The carbonyl of the acrylamide
formed hydrogen bond interactions with the backbone NH of
residues Gly 193 and Ser 195, which form part of the oxyanion
hole. The nitrogen of the acrylamide made a hydrogen bond via
a water to the backbone carbonyl of Ser 214. The 3-nitrogen of
the imidazole formed a hydrogen bond through a water to Leu
41 carbonyl and the OH of Ser 195. The chlorine formed a
lipophilic interaction with the side chain of Lys 192. The phenyl
methyl carbamate bound in the S2′ pocket and the nitrogen
formed a hydrogen bond with the backbone carbonyl of His 40.
The structure showed that the morpholine ring projected
toward the S2 pocket and differs from the benzyl group in
compound 3, which projected into the S1′ pocket. The P2
linker carbonyl made a hydrogen bond to Leu 41.
B
DOI: 10.1021/acsmedchemlett.5b00066
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ACS Medicinal Chemistry Letters
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Unfortunately, inhibitor 9 did not show improvement in
solubility or human liver microsome stability. The analogue of
4-acetylpiperazine amide (10) maintained excellent FXIa
binding and anticoagulation potency (FXIa Ki 0.6 nM and
aPTT EC2x 4.6 μM). With the incorporation of a more basic
methyl piperazine, analogue 11 not only demonstrated
excellent enzyme affinity (FXIa Ki 0.4 nM) and in vitro
anticoagulant potency (aPTT EC2x 3.7 μM) but also enhanced
aqueous solubility (44 μg/mL). The corresponding thiomor-
pholine 1,1-dioxide analogue 12 had excellent FXIa affinity
(FXIa Ki 0.3 nM), in vitro anticoagulant potency (aPTT EC2x
3.6 μM), and significant improvement of human liver
microsome stability, but unfortunately no increase in solubility.
Further SAR efforts to combine the P2′ hydroxyquinolinone
group in 8 and the P2 N-methylpiperazine amide in 11 into one
molecule (13) demonstrated additive effects on the FXIa
affinity and in vitro anticoagulation aPTT potency (Figure 3).
Figure 3. Combination of P2 and P2′ SAR.
Compound 13 has a FXIa Ki of 0.04 nM and an aPTT EC2x of
1.0 μM, with aqueous solubility of 17 μg/mL in pH 6.5 buffer.
In human liver microsome, 13 has a half-life measured at >200
min.
An X-ray crystal structure (Figure 4A) of compound 13
bound in the active site of FXIa was obtained at 2.2 Å
resolution.23 Similar to compound 9, the X-ray structure
showed that the chlorophenyltetrazole moiety occupied the S1
pocket. Additionally, the carbonyl of the acrylamide formed
hydrogen bond interactions with the oxyanion hole, and the 3-
nitrogen of the ring formed a hydrogen bond with Ser 195 OH
and Leu 41 carbonyl through a water. The N-methyl piperazine
bound above His 57 and was flanked by Tyr 58B in the P2
pocket.
In the S2′ region, both the NH and carbonyl of quinolinone
formed hydrogen bonds with His 40, while the OH formed a
hydrogen bond with Tyr 143. Figure 4B shows the super-
imposition comparison of the X-ray crystal structure of
compound 13 with compound 323 bound in the active site of
FXIa. The two compounds show a similar binding mode, with
extra interactions observed from the P2 and P2′ regions for
compound 13.
A representative synthesis of the P2′ analogues in Table 1 is
illustrated in Scheme 1 (see Supporting Information).
Condensation of N-Boc-L-phenylalaninal 1a and glyoxal trimer
with ammonia in methanol afforded 4,5-unsubstituted
imidazole 1b. Monochlorination with NCS, followed by
bromination with NBS, afforded 4-bromo-5-chloro imidazole
derivative 1c. Suzuki−Miyaura coupling of 1c with boronic acid
1e, which was prepared from 1d,24 gave quinolinone amine
derivative 1f after removal of the Boc group. Amide formation
of 1f with 1g21 afforded 5.
Figure 4. (A) X-ray crystal structure of 13 in FXIa. Final model is
shown with initial Fo-Fc electron density contoured at 2.5 rmsd. The
high B-factors of compound 13 in the final model suggest that it has
only partially occupied the site. As a consequence, a relatively low
contour level is needed, and the chlorine of the chloroimidazole is not
covered with density. (B) X-ray structure of 13 (cyan) superimposed
with the X-ray structure of 3 (magenta).
literature.25 The alkylation of N-Boc phenylalanine with 2-
bromo-1-(4-nitrophenyl) gave α-acyloxyketone 2a, which
underwent cyclization to form 4-arylimidazole 2b by heating
with NH4OAc in xylene. Chlorination at the C5 position with
NCS afforded 2c. Reducing the nitro group afforded amine 2d,
which was coupled with malonic acid mono-tert-butyl ester to
provide 2e. Cyclization of 2e under heating PPA conditions
provided 4-hydroxyquinolinone amino acid 2f in near
quantitative yield. This amino acid was reacted with N-
hydroxysuccinimide ester 2h, which was prepared from 2g,21 to
give the penultimate acid 2i. Final amide coupling under mixed
anhydride conditions afforded 13 in good overall yield (26%).
Compound 13 was highly selective against other related
serine proteases except plasma kallikrein26 with a Ki of 7 nM
(Table 3). The in vitro and in vivo profiles of compound 13,
including enzyme binding, anticoagulation aPTT potency,
plasma protein binding, and pharmacokinetics across different
species, are summarized in Table 4. Compound 13 has a very
good human in vitro profile and, in addition, has a similar FXIa
affinity and aPTT in rabbit, the species used for animal
modeling, with a Ki of 0.58 nM and EC1.5x of 1.0 μM in rabbit,
respectively. Compound 13 demonstrated high free fractions in
Compound 13 was prepared following the procedure
described in Scheme 2. The imidazole intermediate 2b was
prepared by following a modified procedure as reported in
C
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a
Scheme 1
a
Reagents and conditions: (a) glyoxal trimer dihydrate, 7 N NH3 in MeOH, rt, 70%; (b) NCS, CH3CN, 0−50 °C, 36%; (c) NBS, CHCl3, rt, 71%;
(d) bis(neopentylglycolato)diboron, PdCl2(dppf), KOAc, DMSO, 85%; (e) Pd(t-Bu3P)2, K3PO4, dioxane/H2O, 80 °C, 78%; (f) TFA, DCM, 100%;
(g) EDC, HOBt, DIEA, DMF, 44%.
a
Scheme 2
a
Reagents and conditions: (a) Cs2CO3, 30 min, rt, 94%; (b) NH4OAc, xylene, reflux, 77%; (c) NCS, MeCN, 70 °C, 80%; (d) SnCl2, NH4Cl,
MeOH, 98%; (e) PyBOP, DIEA, DMF, 91%; (f) PPA, 130 °C, >95%; (g) N-hydroxysuccinimide, DIC, DMF, rt, 100%; (h) DIEA, DMSO, 89%; (i)
isobutylchloroformate, DIEA, DMF, 0 °C, 5 min, then N-methylpiperazine, 0 °C, 57%.
Table 3. Selectivity of Compound 13 against Related Enzymes
H.
P.
T.
enzyme
a
FXIa
FVIIa
FXa
FIXa
FXIIa
thrombin trypsin kallikrein
kallikrein chrymotripsin
tPA
urokinase
>1600
APC
Ki (nM) 0.04
>13330
>9000
>60000
>20000
7400
6200
7.0
>30000
400
29000
>54000
a
Ki values were obtained from human enzyme and were averaged from duplicated IC50 determinations.
plasma protein binding studies across the species evaluated,
with 8% free for human and cyno, 7% for rabbit, and 18% for
dog. In pharmacokinetics studies, the half-life was shown to be
suitable for iv administration (1 to 2 h across all species).
Compound 13 was evaluated in the rabbit electrically
induced carotid arterial thrombosis (ECAT) model.27 As
shown in Figure 5, 13 produced a dose-dependent increase in
integrated blood flow of the injured artery. A dose-dependent
increase in potency of thrombus reduction is demonstrated in
the antithrombotic concentration−response curve in the rabbit
ECAT with an EC50 of 0.53 μM (Figure 6). In the rabbit cuticle
bleeding time (CBT) model,28 only minimal bleeding time
prolongation was observed for 13 even at the highest dose
studied, as indicated in the bleeding time curve shown in Figure
6. At the top dose, 13 prolonged aPTT by 3.2-fold, but not
prothrombin time (PT) or thrombin time (TT), as expected
with the FXIa mechanism.
In summary, optimization of an imidazole series of FXIa
inhibitors at the P2 and P2′ regions led to the discovery of a
potent inhibitor 13 with a FXIa Ki of 0.04 nM, an aPTT EC1.5x
of 0.28 μM, and a short half-life suitable for parenteral dosing.
Compound 13 demonstrated robust antithrombotic efficacy in
D
DOI: 10.1021/acsmedchemlett.5b00066
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ACS Medicinal Chemistry Letters
Letter
Table 4. Profile of Compound 13 in Different Species
ACKNOWLEDGMENTS
■
We thank Dr. Ying Han for generation of a P2 compound
library, and the Department of Discovery Synthesis and BMS
Biocon Research Center for the large-scale synthesis of
intermediate 1c. Use of the Advanced Photon Source was
supported by the U.S. Department of Energy, Office of Science,
Office of Basic Energy Sciences, under Contract No. DE-AC02-
06CH11357, and use of the IMCA-CAT beamline 17-BM at
the Advanced Photon Source was supported by the companies
of the Industrial Macromolecular Crystallography Association
through a contract with Hauptman-Woodward Medical
Research Institute.
human
rabbit
dog
rat
cyno
a
XIa Ki (nM)
0.10
0.28
8.0
0.58
1.0
aPTT EC1.5x (μM)
0.3
18
>20
2.6
0.3
8.0
1.9
free fraction (%)
7.0
b
PK half-life (h)
1.1
1.1
1.1
a
b
Determined at 37 °C. IV dosed at 1 mg/kg. Salt forms and
formulations: rabbit, 13-HCl salt, 10% DMAc/90% D5W (5%
dextrose in water); dog, 13-HCl salt, 10% DMAc/10% ethanol/10%
propylene glycol/70% water; rat, 13-TFA salt, 10% DMAc/90% water;
cyno, 13-HCl salt, 10% DMAc/90% water.
REFERENCES
■
(1) Ansell, J.; Hirsh, J.; Hylek, E.; Jacobson, A.; Crowther, M.;
Palareti, G. Pharmacology and management of the vitamin K
antagonists: American College of Chest Physicians Evidence-based
Clinical Practice Guidelines (8th Edition). Chest 2008, 133, 160S−
198S.
(2) Stein, P. D.; Grandison, D.; Hua, T. A. Therapeutic level of
anticoagulation with warfarin in patients with mechanical prosthetic
heart valves: review of literature and recommendations based on
internal normalized ratio. Postgrad. Med. J. 1994, 70 (suppl 1), S72−
S83.
(3) Hirsh, J.; Poller, L. The international normalized ratio. A guide to
understanding and correcting its problems. Arch. Int. Med. 1994, 154,
282−288.
(4) Yeh, C. H.; Fredenburgh, J. C.; Weitz, J. I. Oral direct factor Xa
inhibitors. Circ. Res. 2012, 111 (8), 1069−1078.
(5) Spinler, S. The pharmacology and therapeutic use of dabigatran
etexilate. J. Clin. Pharmacol. 2013, 53 (1), 1−13.
Figure 5. Antithrombotic effect of compound 13 in rabbit ECAT
model.
(6) Pinto, D. J. P.; Wong, P. C.; Knabb, R. M.; Wexler, R. R. Case
history: Eliquis (Apixaban), a potent and selective inhibitor of
coagulation factor Xa for the prevention and treatment of thrombotic
diseases. Annu. Rep. Med. Chem. 2012, 47, 123−139.
(7) Granger, C. B.; Alexander, J. H.; McMurray, J. J.; Lopes, R. D.;
Hylek, E. M.; Hanna, M.; Al-Khalidi, H. R.; Ansell, J.; Atar, D.;
Avezum, A.; Bahit, M. C.; Diaz, R.; Easton, J. D.; Ezekowitz, J. A.;
Flaker, G.; Garcia, D.; Geraldes, M.; Gersh, B. J.; Golitsyn, S.; Goto, S.;
Hermosillo, A. G.; Hohnloser, S. H.; Horowitz, J.; Mohan, P.; Jansky,
P.; Lewis, B. S.; Lopez-Sendon, J. L.; Pais, P.; Parkhomenko, A.;
Verheugt, F. W.; Zhu, J.; Wallentin, L. Apixaban versus warfarin in
patients with atrial fibrillation. N. Engl. J. Med. 2011, 365 (11), 981−
992.
Figure 6. Compound 13 in rabbit ECAT efficacy and CBT bleeding
models. (A) Antithrombotic concentration−response curve in the
rabbit ECAT. (B) Antithrombotic efficacy (blue) vs bleeding time
(red).
(8) Perzborn, E.; Roehring, S.; Straub, A.; Kubitza, D.; Misselwitz, F.
The discovery and development of rivaroxaban, an oral, direct factor
Xa inhibitor. Nat. Rev. Drug Discovery 2011, 10, 61−75.
(9) Straub, A.; Roehrig, S.; Hillisch, A. Entering the era of non-basic
P1 site groups: discovery of Xarelto (Rivaroxaban). Curr. Top. Med.
Chem. 2010, 10, 257−269.
(10) Franchini, M.; Veneri, D.; Lippi, G. Inherited factor XIa
deficiency: a concise review. Hematology 2006, 11, 307−309.
(11) Gailani, D.; Lasky, N.; Broze, G. A murine model of factor XI
deficiency. Blood Coagulation Fibrinolysis 1997, 8, 134−144.
(12) Wang, X.; Cheng, I.; Xu, I.; Feuerstein, G. Z.; Hsu, M.-Y.; Smith,
P. L.; Seiffert, D.; Schumacher, W. A.; Ogletree, M. L.; Gailani, D.
Effects of factor IX or factor XI deficiency on ferric chloride-induced
carotid artery occlusion in mice. J. Thromb. Haemostasis 2005, 3, 695−
702.
a rabbit ECAT thrombosis model with an EC50 of 0.53 μM. In
the rabbit CBT model, minimal increase in bleeding time was
observed. Overall, the favorable profile of compound 13
allowed further preclinical evaluation to determine its potential
as a parenteral antithrombotic agent.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental procedures and characterization data for com-
pounds 4−13. This material is available free of charge via the
Internet at http://pubs.acs.org.
(13) Rosen, E. D.; Gailani, D.; Castellino, J. F. FXI is essential for
thrombus formation following FeCl3-induced injury of the carotid
artery in the mouse. Thromb. Haemostasis 2002, 87, 774.
(14) Schumacher, W.; Luettgen, J.; Quan, M. L.; Seiffert, D.
Inhibition of factor XIa as a new approach to anticoagulant.
Arterioscler. Thromb. Vasc. Biol. 2010, 30, 388−392.
AUTHOR INFORMATION
Corresponding Author
*E-mail: zilun.hu@bms.com. Tel: (1) 609-818-5290.
Notes
■
The authors declare no competing financial interest.
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Letter
(15) van Montfoort, M. L.; Meijers, J. C. M. Anticoagulation beyond
direct thrombin and factor Xa inhibitors: indications for targeting the
intrinsic pathway? Thromb. Haemostasis 2013, 110, 223−232.
(16) Lowenberg, E. C.; Meijers, J. C. M.; Monia, B. P.; Levi, M.
̈
Coagulation factor XI as a novel target for antithrombotic treatment. J.
Thromb. Haemostasis 2010, 8, 2349−2357.
(17) Buller, H. R.; Bethune, C.; Bhanot, S.; Gailani, D.; Monia, B. P.;
̈
Raskob, G. E.; Segers, A.; Verhamme, P.; Weitz, J. I. Factor XI
antisense oligonucleotide for prevention of venous thrombosis. N.
Engl. J. Med. 2015, 372, 233−240 This was published after this work
was complete..
(18) Quan, M.; Wong, P. C.; Wang, C.; Woerner, F.; Smallheer, J.
M.; Barbera, F. A.; Bozarth, J. M.; Brown, R. L.; Harpel, M. R.;
Luettgen, J. M.; Morin, P. E.; Peterson, T.; Ramamurthy, V.; Rendina,
A. R.; Rossi, K. A.; Watson, C. A.; Wei, A.; Zhang, G.; Seiffert, D.;
Wexler, R. R. Tetrahydroquinoline derivatives as potent and selective
factor XIa inhibitors. J. Med. Chem. 2014, 57, 955−969.
(19) Wong, P. C.; Quan, M. L.; Watson, C.; Crain, E.; Wexler, R. R.;
Seiffert, D. Potent antithrombotic effect of a small-molecule, reversible
and direct inhibitor of factor XIa with minimum bleeding time effect in
rabbit models of arterial thrombosis and hemostasis; AHA: Dallas, TX,
Nov. 2013; APS.709.03, Poster 7050.
(20) Hangeland, J. J.; Friends, T. J.; Rossi, K. A.; Smallheer, J. M.;
Wang, C.; Sun, Z.; Corte, J. R.; Fanf, T.; Wong, P. C.; Rendina, A. R.;
Barbera, F. A.; Bozarth, J. M.; Luettgen, J. M.; Watson, C. A.; Zhang,
G.; Wei, A.; Morin, P. E.; Bisacchi, G. S.; Seiffert, D.; Wexler, R. R.;
Quan, M. L. Optimization of phenylimidazole coagulation Factor XIa
inhibitors: discovery of trans-N-((S)-1-(4-(3-amino-1H-indazol-6-yl)-
5-chloro-1H-imidazol-2-yl)-2-phenylethyl)-4-(aminomethyl)cyclo-hex-
anecarboxamide, a potent Factor XIa inhibitor with in vivo
antithrombotic activity. J. Med. Chem. 2014, 57, 9915−9932.
(21) Pinto, D. J. P.; Smallheer, J. M.; Corte, J. R.; Austin, E. J. D.;
Wang, C.; Fang, T.; Smith, L. M., II; Rossi, K. A.; Rendina, A. R.;
Bozarth, J. M.; Zhang, G.; Wei, A.; Ramamurthy, V.; Sheriff, S.; Myers,
J. E., Jr; Morin, P. E.; Luettgen, J. M.; Seiffert, D. A.; Quan, M. L.;
Wexler, R. R. Structure-based design of inhibitors of coagulation factor
XIa with novel P1 moieties. Bioorg. Med. Chem. Lett. 2015, 25, 1635−
1642.
(22) McNaney, C. A.; Dexler, D. M.; Hnatyshyn, S. Y.; Zvyaga, T. A.;
Knipe, J. O.; Belcastro, J. V.; Sanders, M. An automated liquid
chromatography-mass spectrometry process to determine metabolic
stability half-life and intrinsic clearance of drug candidates by substrate
depletion. Assay Drug Dev. Technol. 2008, 6, 121−129.
(23) Coordinates for the enzyme/inhibitor structures, data collection
and refinement statistics, and the X-ray diffraction data have been
deposited with the Protein Data Bank (PDB). The PDB deposition
IDs are for compounds 3 (4Y8X), 9 (4Y8Y), and 13 (4Y8Z).
(24) Baston, E.; Palusczak, A.; Hartmann, R. W. 6-Substituted 1H-
quinolin-2-ones and 2-methoxy-quinolines: synthesis and evaluation as
inhibitors of steroid 5-alpha reductases types 1 and 2. Eur. J. Med.
Chem. 2000, 35, 931−940.
(25) Gordon, T. D.; Singh, J.; Hansen, P. E.; Morgan, B. A. Synthetic
approaches to the ‘Azole’ peptide mimetics. Tetrahedron Lett. 1993, 34,
1901−1904.
́
(26) Roles of plama kallikrein: (a) Bjorkqvist, J.; Jamsa, A.; Renne, T.
̈
̈
̈
Plasma kallikrein: the bradykinin-producing enzyme. Thromb. Haemo-
stasis 2013, 110, 399−407. (b) Feener, E. P.; Zhou, Q.; Fickweiler, W.
Role of plasma kallikrein in diabetes and metabolism. Thromb.
Haemostasis 2013, 110, 434−441.
(27) Wong, P. C.; Crain, E. J.; Knabb, R. M.; Meade, R. P.; Quan, M.
L.; Watson, C. A.; Wexler, R. R.; Wright, M. R.; Slee, A. M. Electrically
Induced Carotid Artery Thrombosis. J. Pharmacol. Exp. Ther. 2000,
295, 212−218.
(28) Wong, P. C.; Crain, E. J.; Watson, C. A.; Zaspel, A. M.; Wright,
M. R.; Lam, P. K.; Pinto, D. J. P.; Wexler, R. R.; Knabb, R. M.
Nonpeptide factor Xa inhibitors III: effects of DPC423, an orally-
active pyrazole antithrombotic agent, on arterial thrombosis in rabbits.
J. Pharmacol. Exp. Ther. 2002, 303, 993−1000.
F
DOI: 10.1021/acsmedchemlett.5b00066
ACS Med. Chem. Lett. XXXX, XXX, XXX−XXX