Synthesis and evaluation of acylguanidine FXa inhibitors

Article abstract of DOI:10.1016/j.bmcl.2008.07.004

A series of acylguanidine derivatives were prepared and investigated as inhibitors of Factor Xa (FXa). These compounds were made by guanidine acylation with carboxylic acids using carbonyl diimidazole (CDI) as the coupling reagent. Conditions for the rapid synthesis and purification of these compounds are described along with their ability to inhibit FXa. The best FXa inhibitor is 1 with a FXa IC₅₀ of 6 nM.

Full text of DOI:10.1016/j.bmcl.2008.07.004

Bioorganic & Medicinal Chemistry Letters 18 (2008) 4696–4699
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and evaluation of acylguanidine FXa inhibitors
a
a
b
b
Stephen P. O’Connor a, , Karnail Atwal , Chi Li , Eddie C.-K. Liu , Steven M. Seiler ,
*
Mengxiao Shi a, , Yan Shi a, Philip D. Stein a,à, Ying Wang a
a Department of Discovery Chemistry, Bristol-Myers Squibb Research and Development, PO Box 5400, Princeton, NJ 08543-5400, USA
b Department of Cardiovascular Diseases, Bristol-Myers Squibb Research and Development, PO Box 5400, Princeton, NJ 08543-5400, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of acylguanidine derivatives were prepared and investigated as inhibitors of Factor Xa (FXa).
These compounds were made by guanidine acylation with carboxylic acids using carbonyl diimidazole
(CDI) as the coupling reagent. Conditions for the rapid synthesis and purification of these compounds
are described along with their ability to inhibit FXa. The best FXa inhibitor is 1 with a FXa IC50 of 6 nM.
Ó 2008 Elsevier Ltd. All rights reserved.
Received 25 March 2008
Revised 27 June 2008
Accepted 1 July 2008
Available online 5 July 2008
Keywords:
Serine protease
Coagulation
Factor Xa
Heparin and CoumadinÒ are two of the most commonly admin-
istered anticoagulants. However, heparin must be used intrave-
nously, and both heparin and CoumadinÒ can lead to excessive
bleeding and hemorrhage. A safer and more convenient oral anti-
coagulant therapy is needed that would alleviate these liabilities
within the current treatment regimens.1 At the junction of the
intrinsic and extrinsic (tissue factor) coagulation cascades lies the
trypsin-like serine protease factor Xa (FXa).2 FXa inhibition offers
a reduced risk of unwarranted bleeding compared with thrombin
inhibitors.3 Inhibition of FXa has been an active area of pharmaceu-
tical development with many intravenous4 and orally active com-
pounds5 currently under investigation such as the parenteral
inhibitor fondaparinux6 and the small molecule inhibitors razax-
aban,7 apixaban,8 rivaroxaban (BAY 59-7939),9 and LY-517717.10
Earlier disclosures from these laboratories have elaborated a
series of lactam-based urea, thiourea, carbamate, amide, and sul-
fonamide derivatives11 as well as ketene aminal analogs.12 We re-
port herein the activity of a series of analogous lactam-based
acylguanidine derivatives as well as a method for their rapid syn-
thesis and purification from simple guanidine precursors.
an acylated guanidine 1 (IC50 = 6 nM), whose initial synthesis is
shown in Scheme 1.
The synthesis of 1 began by coupling 5-amino-2-methylbenzo-
furan with benzoyl isothiocyanate in chloroform (81% yield). The
product acylthiourea was then coupled with aminocaprolactam
compound 3 using EDCI to provide 1 (10% yield). While this was
a simple process, the low yield in the coupling step, albeit unop-
timized, as well as the limited availability of diverse acyl isothiocy-
anates precluded this approach for the rapid synthesis of a large
number of analogs. As we desired to explore diversity in the acyl
substituent using various aryl groups as replacements for the 2-
methylbenzofuran fragment,13 an alternative route to compounds
such as 6 was needed.
A more versatile route to acylguanidines is shown in Scheme 2.
An aryl amine can be converted to the corresponding isothiocya-
nate, coupled with aminolactam 3 to yield thiourea 4, aminated
to guanidine 5, and then acylated with a carboxylic acid to provide
Caprolactam pyrrolidine amide 311 and 5-amino-2-methylben-
zofuran12 have been described previously as providing potent
FXa inhibitors when linked as ureas and ketene aminals. We cre-
ated a potent, new chemotype by linking these groups through
* Corresponding author. Tel.: +1 609 818 4996; fax: +1 609 818 3450.
E-mail address: steve.oconnor@bms.com (S.P. O’Connor).
Present address: Wyeth Research, 401 N. Middletown Road, Pearl River, NY
10965, USA.
à
Present address: Redpoint Bio Corporation, 2005 Eastpark Blvd., Cranbury, NJ
Scheme 1. Reagents and conditions: (a) CHCl3, rt, 81%; (b) EDCI, DMF/CHCl3, rt,
08512, USA.
10%.
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.07.004

S. P. O’Connor et al. / Bioorg. Med. Chem. Lett. 18 (2008) 4696–4699
4697
A brief selection of acylation conditions (acid chloride; PyBop/
Et3N; CDI)16 suggested that the use of CDI17 was superior, based
on higher conversion and ease of purification. The acid chloride
method produced undesired by-products (mono- and di-acylated
species), while the use of PyBop concommitantly generates a phos-
phoramide which was difficult to separate from the products. The
only by-products for the CDI method were imidazole (neutral, pKa
6.9518
) and unreacted guanidine (basic) and carboxylic acid
(acidic) precursors. The wide differences in polarity or pKa’s for
these species suggested that a simple method of purification could
be developed. In order to investigate this, we optimized the reac-
tion conditions for quantitative conversion of guanidine 10 to
product 1: benzoic acid (1.5 equiv) was reacted with CDI
(1.5 equiv) in acetonitrile to which was then added the guanidine
1 (1.0 equiv). This reaction mixture was then used to find a purifi-
cation method that would be efficient (high yielding), effective
(high purity products), and simple (high throughput).
Our initial attempts at purification using anion or cation ex-
change resins were not successful as imidazole could not be sepa-
rated from the products.19 Purification on silica gel gave variable
results as different acylguanidine products displayed a wide range
of polarities and elution profiles. However, the method that we
used for the analysis of reaction progress, reverse phase C-18 (octa-
decyl-bound silica gel) liquid chromatography (LC), suggested a
simple solution. All of the reaction components and by-products
(benzoic acid, guanidine 10, imidazole) eluted faster from the C-
18 column than the product acylguanidine.20 A low concentration
(5–20%) of methanol or acetonitrile in water, when passed through
a column of C-18, should elute all of the undesired components.
Product 1 should not elute until a higher level of the organic com-
ponent was used.21 The reaction products proved to be suitable for
step-gradient purification on disposable C-18 sample cleanup
cartridges.22
Scheme 2. General synthesis of acyl guanidines through isothiocyanate, thiourea,
and guanidine.
the product 6. While this was a four-step process, the last step was
the key reaction, allowing a large number of products to be pro-
duced through the final combination of guanidines and carboxylic
acids. Thus, we chose to optimize the chemistry in this route, par-
ticularly the last step, and to devise a fast and simple method for
the purification of the final products. In order to establish the reg-
ioselectivity of the guanidine acylation, we optimized the route
with compound 1 as the target, because the position of the acyl
group had been unambiguously established through the isothiocy-
anate route described in Scheme 1.
Executing the general synthesis outlined in Scheme 2, 5-ami-
no-2-methylbenzofuran was reacted with commercially available
1,10-thiocarbonyldi-2(1H)-pyridone (7) to provide the corre-
sponding isothiocyanate 8 (91% yield, Scheme 3).14 The coupling
of the isothiocyanate with caprolactam amine 3 gave thiourea 9
in 87% yield. Conversion to guanidine 10 was carried out using
red mercury (II) oxide and 7 M ammonia in methanol (74%).15
While 2 M ammonia in methanol also provided product 10, we
had observed up to 30% of a by-product having a molecular
weight corresponding to the dimeric compound 11. We reasoned
that such a compound might arise by coupling between the
product guanidine and unreacted thiourea 9. As such, we were
gratified to find that the use of higher ammonia concentrations
(7 M) reduced the level of this by-product to less than 10%. With
a reliable method in hand to make a variety of guanidines, we
were now prepared to investigate the final acylation and purifi-
cation sequence.
With a method in hand for the synthesis and rapid purifica-
tion of acylguanidines of structure 6, our next goal was to
evaluate alternatives to the 2-methylbenzofuran portion of 1
while surveying the acyl component. The m-tolyl and p-anisyl
analogs were chosen due to the structural homology with
compound 1. A number of carboxylic acids were selected as
coupling components, and representative groups are shown in
Tables 1 and 2.24
Table 1
m-Tolyl acylguanidines
a
Compound #
R
FXa IC50 (nM)
Yield (%)
Purity (%)
12
13
14
15
16
17
18
19
20
21
22
23
24
Ph
245
276
709
517
371
198
835
373
222
271
396
400
1159
85
35
44
92
55
62
25
63
74
35
50
49
51
87
96
89
90
91
91
94
93
94
88
94
100
88
3-MeO-Ph
4-MeO-Ph
4-Me2N-Ph
3-Cl-Ph
4-Cl-Ph
3,5-Di-Cl-Ph
3-F-Ph
4-F-Ph
3,4-Di-F-Ph
3,5-Di-F-Ph
3,4-Di-MeO-Ph
3,5-Di-MeO-Ph
Scheme 3. Reagents and conditions: (a) CH2Cl2, rt, 91%; (b) 3 (1.1 equiv), CHCl3,
60 °C, 87%; (c) red HgO (10 equiv), 7 M NH3/CH3OH, rt, 74%; (d) PhCO2H (1.5 equiv),
CDI (1.5 equiv), CH3CN, rt, 68%.
a
IC50 measured against human FXa using the cleavage of synthetic substrate S-
2222.

4698
S. P. O’Connor et al. / Bioorg. Med. Chem. Lett. 18 (2008) 4696–4699
Table 2
p-Anisyl acylguanidines
and p-anisyl 25 (246 nM) analogs when compared to the corre-
sponding 2-methylbenzofuran-5-yl compound 1 (6 nM). Within
the set of carboxylic acids examined, all of the compounds in Ta-
bles 1 and 2 were nearly two orders of magnitude less potent
than compound 1.
For all of the compounds in Tables 1 and 2 the concentration
required to double the prothrombin-based clotting time in hu-
man plasma (EC2XPT) was greater than 50
the original lead 1 was only marginally better (EC2XPT = 48
l
M. This value for
a
Compound #
R
FXa IC50 (nM)
Yield (%)
Purity (%)
l
M).
25
26
27
28
29
30
31
32
33
34
35
36
37
Ph
246
193
227
403
267
294
546
256
368
272
208
494
872
71
69
74
52
65
58
40
53
54
42
25
42
66
97
96
97
98
97
93
92
91
95
85
82
95
83
In a further effort to improve the potency of the m-tolyl and
p-anisyl analogs relative to the 2-methylbenzofuran-5-yl com-
pounds, as well as to improve the prothrombin time effects,
we choose a small set of three additional carboxylic acids to
examine. Two heterocyclic acids (isoxazole-5-carboxylic acid
and 2,4-dimethylthiazole-5-carboxylic acid) and an amide con-
taining compound (1-benzoylpiperidine-4-carboxylic acid) were
selected. These compounds were chosen to assess the effects of
heterocycles and an amide functional group.
The synthesis and in vitro results for these compounds are
shown in Table 3. As expected, modest to good yields (19–
90%) were obtained with good levels of purity (87–100%). How-
ever, continuing the trend observed above, the 2-methylbenzofu-
ran-5-yl analogs 40/43/46 were significantly more potent (10–
17 nM) than the m-tolyl compounds 38/41/44 (462–1073 nM)
andp-anisyl compounds 39/42/45 (380–506 nM). In addition,
while the p-anisyl compounds 39 and 45 exhibited very modest
3-MeO-Ph
4-MeO-Ph
4-Me2N-Ph
3-Cl-Ph
4-Cl-Ph
3,5-Di-Cl-Ph
3-F-Ph
4-F-Ph
3,4-Di-F-Ph
3,5-Di-F-Ph
3,4-Di-MeO-Ph
3,5-Di-MeO-Ph
a
IC50 measured against human FXa using the cleavage of synthetic substrate S-
2222.
The yields ranged from a modest 25% to 92% with purity levels
of 82–100%. In spite of some low yields, this represented a method
for rapid synthesis and purification of acylguanidines with good to
excellent levels of product purity. Some features worth noting are
(1) the simple ‘on–off’ cartridge purification that was used,25 (2)
minimal reaction optimization, and (3) significant quantities (10–
60 mg) of reasonably pure compounds were obtained for
evaluation.
The compounds in Tables 1 and 2 showed moderate FXa
inhibitory effects. Monosubstituted benzoic acids in general pro-
vided more potent acylguanidine products than disubstituted
analogs; however, disubstitution with fluorine was better toler-
ated than with chlorine or methoxy. The most apparent trend
was a significant drop in potency of the m-tolyl 12 (245 nM)
activity at best in the prothrombin assay (EC2XPT = 45 and 48
lM,
respectively),
(EC2XPT = 17.7
the
2-methylbenzofuran-5-yl
analogs
40
l
M), 43 (EC2XPT = 42
lM), and 46 (EC2XPT = 7.5
l
l
M),
M),
all had superior activity. Relative to lead 1 (EC2XPT = 48
amide 46 was sixfold more potent in the prothrombin assay sug-
gesting that polarity in this region of the molecule may improve
in vivo potency.
In summary, we have developed a simple method for the
efficient synthesis and purification of acylguanidines from car-
boxylic acid and guanidine precursors. The use of CDI as cou-
pling reagent and
a
reverse phase cartridge purification
strategy were key features that provided a rapid means for
Table 3
Comparison of selected acylguanidines
a
R
Core
Compound
FXa IC50 (nM)
EC2XPT
(l
M)
Yield (%)
Purity (%)
A
B
C
38
39
40
628
380
14
50
45
17.7
51
44
90
87
98
97
A
B
C
41
42
43
462
386
17
>50
>50
42
44
41
28
98
97
94
A
B
C
44
45
46
1073
506
10
>50
48
7.5
67
76
19
98
98
100
a
IC50 measured against human FXa using the cleavage of synthetic substrate S-2222.

S. P. O’Connor et al. / Bioorg. Med. Chem. Lett. 18 (2008) 4696–4699
4699
S. M.; Youssef, S.; Steinbacher, W. A.; Rendina, A. R.; Bozarth, J. M.; Peterson, T.
L.; Zhang, G.; Zahler, R. Bioorg. Med. Chem. Lett. 2005, 15, 5453.
13. Adam, W.; Ahrweiler, M.; Saha-Moller, C. R.; Sauter, M.; Schonberger, A.; Epe,
B.; Muller, E.; Schiffmann, D.; Stopper, H.; Wild, D. Toxicol. Lett. 1993, 67, 41.
14. Kim, S.; Yi, K. Y. J. Org. Chem. 1986, 51, 2613.
15. Wiggall, K. J.; Richardson, S. K. J. Heterocy. Chem. 1995, 32, 867.
16. Multiple acylation products were observed with benzoyl chloride and we
experienced difficulty in separating the PyBop-derived phosphoryl triamide
by-products from the desired acylguanidines without resorting to preparative
HPLC.
17. (a) Ahmad, S.; Doweyko, L. M.; Dugar, S.; Grazier, N.; Ngu, K.; Wu, S. C.; Yost, K.
J.; Chen, B.-C.; Gougoutas, J. Z.; DiMarco, J. D.; Lan, S.-J.; Gavin, B. J.; Chen, A. Y.;
Dorso, C. R.; Serafino, R.; Kirby, M.; Atwal, K. S. J. Med. Chem. 2001, 44, 3302; (b)
Ahmad, S.; Wu, S. C.; Atwal, K. S.; Dugar, S. U.S. Patent 6,011,059, 2000.; (c)
Kitano, M.; Nakano, K.; Ohashi, N. WO 2000044707, 2000.; (d) Owens, A. H.;
Goehring, R. R.; Lampe, J. W.; Erhardt, P. W.; Lumma, W. C., Jr.; Wiggins, J. Eur. J.
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obtaining products with good levels of purity. The FXa inhibi-
tory potential of these compounds revealed a strong preference
for the 2-methylbenzofuran in 1 (IC50 = 6 nM) relative to the
m-tolyl and p-anisyl portions of 12 (IC50 = 245 nM) and 25
(IC50 = 246 nM), respectively. However, while the intrinsic po-
tency of compound 1 was good, the concentration required
to double the prothrombin-based clotting time in human plas-
ma was low (EC2XPT = 48
lM). Compound 46 (IC50 = 10 nM;
EC2XPT = 7.5 M) displayed good intrinsic potency with a signif-
l
icantly improved prothrombin time. Further elaboration of this
chemotype will be disclosed in a more detailed publication in
the future.
References and notes
18. Lide, D. R. CRC Handbook of Chemistry and Physics, 78th ed.; CRC Press: Boca
Raton, 1997–1998.
19. Since the products were neutral and the potential impurities were either
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Drug Discovery; Abraham, D., Ed.; John Wiley, 2003; Vol. 3, p 283–338.
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Drugs 2003, 4, 272; (b) Betz, A. Expert Opin. Ther. Patents 2001, 11, 1007; (c)
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2001, 10, 845; (d) Sanderson, P. E. J.. In Annu. Rep. Med. ChemChem.; Doherty, A.
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Thromb. Haemost. 2007, 5, 2368; (b) Wong, P. C.; Crain, E. J.; Watson, C. A.;
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charged or very polar, we first examined ion exchange as
a means of
purification. While it was possible to remove the acidic unreacted carboxylic
acid using an anion-exchange cartridge and the basic unreacted guanidine
could be eliminated with a cation-exchange cartridge, the neutral by-product
imidazole (pKa 6.95) was problematic. This contaminant co-eluted with
product from both types of ion-exchange cartridges. In addition, silica gel did
not provide a general method of purification as the products had a range of
polarities and required tedious adjustment of the solvent composition for
efficient elution.
20. (a) The conditions for LC analysis were either (a) or (b): (a) YMC S5 ODS
4.6 ꢀ 50 mm column; gradient from 10% MeOH/0.1% aqueous TFA to 90%
MeOH/0.1% aqueous TFA over 4 min; flow rate = 4 mL/min; 220 nM detection.;
(b) Phenomenex Luna 5
0.2% aqueous H3PO4 to 90% MeOH/0.2% aqueous H3PO4 over 4 min; flow
rate = 4 mL/min; 220 nM detection.
l C-18 4.6 ꢀ 50 mm column; gradient from 10% MeOH/
21. An excess of benzoic acid and CDI was used to drive all of the guanidines to
product ensuring that the reaction mixture would contain, after an aqueous
quench, only the fast eluting benzoic acid and imidazole along with the less
polar product.
5. (a) Lam, P. Y. S.; Clark, C. G.; Li, R.; Pinto, D. J. P.; Orwat, M. J.; Galemmo, R. A.;
Fevig, J. M.; Teleha, C. A.; Alexander, R. S.; Smallwood, A. M.; Rossi, K. A.;
Wright, M. R.; Bai, S. A.; He, K.; Luettgen, J. M.; Wong, P. C.; Knabb, R. M.;
Wexler, R. R. J. Med. Chem. 2003, 46, 4405; (b) Hirayama, F.; Koshio, H.;
Katayama, N.; Kurihara, H.; Taniuchi, Y.; Sato, K.; Hisamichi, N.; Sakai-Moritani,
Y.; Kawasaki, T.; Matsumoto, Y.; Yanagisawa, I. Bioorg. Med. Chem. Lett. 2002,
10, 1509; (c) Choi-Sledeski, Y. M.; Kearney, R.; Poli, G.; Pauls, H.; Gardner, C.;
Gong, Y.; Becker, M.; Davis, R.; Spada, A.; Liang, G.; Chu, V.; Brown, K.; Collussi,
D., ; Leadley, R., Jr.; Rebello, S.; Moxey, P.; Morgan, S.; Bentley, R.; Kasiewski, C.;
Maignan, S.; Guilloteau, J.-P.; Mikol, V. J. Med. Chem. 2003, 46, 681; (d) Phillips,
G. A.; Buckman, B. O.; Davey, D. D.; Eagen, K. A.; Guilford, W. J.; Hinchman, J.;
Ho, E.; Koovakkat, S.; Liang, A.; Light, D. R.; Mohan, R.; Ng, H. P.; Post, J. M.;
Shaw, K. J.; Smith, D.; Subramanyam, B.; Sullivan, M. E.; Trinh, L.; Vergona, R.;
Walters, J.; White, K.; Whitlow, M.; Wu, S.; Xu, W.; Morrissey, M. M. J. Med.
Chem. 1998, 41, 3557.
22. Optimized conditions developed for the final reaction and purification steps
were as follows: to benzoic acid (18 mg, 0.15 mmol, 1.5 equiv) in 0.4 mL of
acetonitrile was added CDI (24 mg, 0.15 mmol, 1.5 equiv). After stirring at
room temperature for 5 min, compound 10 (41 mg, 0.10 mmol) was added and
the reaction progress monitored by LC. Within 2 h, the reaction was complete.
After quenching with 1 mL of water, the resulting slurry was placed directly
onto a 2 g C-18 cartridge23 and eluted with 40 mL of 20% acetonitrile in water.
The cartridge was then eluted with 5 mL of acetonitrile to yield, after
concentration, product 1 (35 mg, 0.068 mmol, 68%) as a tan foam in 96%
purity by LC analysis. This material was identical by 1H and 13C NMR, and co-
eluted on LC, LC-MS, and TLC with compound 1 produced by the alternative
method shown in Scheme 1.
6. Samama, M. M.; Gerotziafas, G. T. Thromb. Res. 2003, 109, 1.
23. The cartridges were first washed sequentially with 4–5 vol each of
methanol then water. Reaction mixtures were loaded onto the cartridges
under water. We have achieved comparable results using Varian 2 g
MegaBondElut C18 HF cartridges (cat. #14256015), United Chemical
Technologies 2.5 g Endcapped C-18 cartridges (cat. #CEC181(2500)6), or
7. Quan, M. L.; Lam, P. Y. S.; Han, Q.; Pinto, D. J. P.; He, M. Y.; Li, R.; Ellis, C. D.;
Clark, C. G.; Teleha, C. A.; Sun, J.-H.; Alexander, R. S.; Bai, S.; Luettgen, J. M.;
Knabb, R. M.; Wong, P. C.; Wexler, R. R. J. Med. Chem. 2005, 48, 1729.
8. Pinto, D. J. P.; Orwat, M. J.; Koch, S.; Rossi, K. A.; Alexander, R. S.; Smallwood, A.;
Wong, P. C.; Rendina, A.; Luettgen, J. M.; Knabb, R. M.; He, K.; Xin, B.; Wexler, R.
R.; Lam, P. Y. S. J. Med. Chem. 2007, 50, 5339.
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Reinemer, P.; Perzborn, E.; Roehrig, S. J. Med. Chem. 2005, 48, 5900; (b) Eriksson,
B. L.; Borris, L.; Dahl, O. E.; Haas, S.; Huisman, M. V.; Kakkar, A. K. J. Thromb.
Haemost. 2006, 4, 121.
cartridges prepared with 2 g of J.T. Baker Bakerbond C-18 40
Packing (cat. #7025-01).
lM Prep LC
24. A modification of the reaction conditions described above was made when
synthesizing multiple acylguanidines simultaneously: the carboxylic acid
(1.5 equiv) and CDI (1.5 equiv) were combined and allowed to react for 2 h.
The guanidine (1.0 equiv) was then added and the reaction mixture was stirred
for 16 h.
10. (a) Liebeschuetz, J. W.; Jones, S. D.; Wiley, M. E.; Young, S. C. Struct. Based Drug
Des. 2006, 173; (b) Hampton, T. JAMA 2006, 295, 743.
25. We viewed this as an ‘on–off’ cartridge purification strategy whereby the
product would remain ‘on’ the C-18 packing with a high concentration of
water, while the undesired components would elute ‘off’. The concentration of
the organic component in the solvent could then be increased to elute the
product.
11. Bisacchi, G. S.; Stein, P. D.; Gougoutas, J. Z.; Hartl, K. S.; Lawrence, R. M.; Liu, E.;
Pudzianowski, A.; Schumacher, W. A.; Sitkoff, D.; Steinbacher, T. E.; Sutton, J.;
Seiler, S. M. Lett. Drug Des. Discov. 2005, 2, 563.
12. Shi, Y.; Zhang, J.; Stein, P. D.; Shi, M.; O’Connor, S. P.; Bisaha, S. N.; Li, C.; Atwal,
K. S.; Bisacchi, G. S.; Sitkoff, D.; Pudzianowski, A. T.; Liu, E. C.; Hartl, K. S.; Seiler,