Design and synthesis of a series of meta aniline-based LFA-1 ICAM inhibitors

Article abstract of DOI:10.1016/j.bmcl.2008.08.061

A series of meta-substituted anilines were designed and synthesized to inhibit the interaction of LFA-1 with ICAM for the treatment of autoimmune disease. Design of these molecules was performed by utilizing a co-crystal structure for structure-based drug

Full text of DOI:10.1016/j.bmcl.2008.08.061

Bioorganic & Medicinal Chemistry Letters 18 (2008) 5249–5251
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design and synthesis of a series of meta aniline-based LFA-1 ICAM inhibitors
*
Kevin M. Guckian , Edward Yin-Shiang Lin, Laura Silvian, Jessica E. Friedman, Donovan Chin,
Daniel M. Scott
Biogen Idec, 14 Cambridge Center, Cambridge, MA 02142, 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 meta-substituted anilines were designed and synthesized to inhibit the interaction of LFA-1
with ICAM for the treatment of autoimmune disease. Design of these molecules was performed by utiliz-
ing a co-crystal structure for structure-based drug design. The resulting molecules were found to be
potent and to possess favorable pharmaceutical properties.
Received 28 July 2008
Revised 14 August 2008
Accepted 18 August 2008
Available online 22 August 2008
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
LFA-1
ICAM
i-Domain
LFA-1/ICAM inhibitors
LFA-1 (Leukocyte function-associated antigen-1) is a cell sur-
face adhesion protein expressed on all leukocytes. The counter
receptors for LFA-1 are ICAMs 1, 2, and 3 (intracellular adhesion
molecule). The interaction of LFA-1 with the ICAM family of recep-
tors is necessary for extravasation of leukocytes from the blood to
the site of inflammation. Disruption of the LFA-1/ICAM interaction
should lead to decreased leukocyte migration to sites of inflamma-
tion and has become an important target in the treatment of auto-
immune disease.1–3 RaptivaÒ, an antibody that disrupts that LFA-1/
ICAM interaction was approved in 2003 for the treatment of auto-
immune disease.4
Figure 1. Scaffold targeted for further optimization.
lished results) with the B–C combination described above, a
series of molecules were docked to investigate substitution on
The LFA-1/ICAM interaction can be disrupted at the site of LFA-
1/ICAM interaction, the metal-ion-dependent adhesion site
(MIDAS), or through binding to an allosteric site (I domain alloste-
ric site, IDAS) on LFA-1 that causes it to adopt a conformation that
cannot bind to ICAM.5 Binding to the MIDAS site has been success-
fully achieved through peptide and peptidomimetic strategies by
researchers at Genentech.6 Our strategy focused on the allosteric
site through modification of a series of molecules originally de-
scribed by Abbott laboratories.7–13 Herein, we describe the discov-
ery of a series of potent inhibitors of the LFA-1/ICAM interaction by
utilizing a structure-based drug design approach.
The scaffold (Fig. 1) we chose for further investigation consists
of three rings designated A, B, and C. SAR studies (unpublished re-
sults) showed the B bis-trifluoromethyl C morpholino rings in
these positions to be a highly preferred substitution and was cho-
sen for further analoging. Utilizing a co-crystal structure (unpub-
Scheme 1. Synthetic scheme for the production of compound 4 and derivatives. (a)
Morpholine, HATU, DIPEA, rt o/n; (b) bis-trifluoromethylacetylene, DCE, À78 to
115 °C o/n then borontrifluoride diethyl etherate, DCE; (c) DCM, pyridine, triflic
anhydride 0–rt; (d) potassium t-butoxide, 3-aminothiophenol 78 °C; (e) ketone or
aldehyde, triacetoxyborohydride, acetic acid, DCE.
* Corresponding author.
E-mail address: kevin.guckian@biogenidec.com (K.M. Guckian).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.08.061

5250
K. M. Guckian et al. / Bioorg. Med. Chem. Lett. 18 (2008) 5249–5251
Table 1
the A-ring. Based on docking into X-ray co-crystal structures, the
meta-substituted aniline seemed to be in an optimal position to
form a hydrogen bond to the carbonyl oxygen of Glu 284 in the
A ring pocket and was chosen for analog synthesis.
Alkyl substitutiona
Synthesis of the target molecule occurred in four steps starting
from commercially available (E)-3-(furan-2-yl)acrylic acid
(Scheme 1). The acid (1) was first coupled to morpholine using
HATU and DIPEA then bis-trifluoromethylacetylene was added at
À78 °C and heated in a high pressure reactor to 115 °C overnight
to affect the Diels Alder reaction.14,15 The intermediate was then
concentrated and a rearrangement ensued upon addition of boron
trifluoride diethyl etherate and heating. The phenol (3) was then
activated as the triflate, which was displaced by the anion of 3-
aminothiophenol to give compound 4.
Compound 4 showed good inhibition of the LFA-1/ICAM inter-
action with an IC50 of 2.0 nM. It was further profiled and was found
to have 27% oral availability with a 4.5-h half-life when dosed at
1 mg/kg in rat. Furthermore, a co-crystal structure with LFA-1
was obtained that confirmed the design hypothesis of hydrogen
bond formation between the aniline N–H of compound 4 and the
carbonyl oxygen of Glu 284 (Fig. 2). To further optimize this com-
pound a series of meta-aniline analogs was investigated.
Compound
R
LFA-1/ICAM1-IG IC50 (nM)
1.7
4
5
4.4
23
6
7
28
8
45
We first looked at simple alkyl and cycloalkyl substitution on
the aniline. These compounds were synthesized by reacting the
parent aniline dissolved in dichloroethane with the corresponding
aldehyde or ketone in the presence of triacetoxyborohydride and
acetic acid (Scheme 1). Compounds 5 and 6 were synthesized by
an alternate route in the same reaction by addition of methyl io-
dide to a solution containing potassium carbonate and DMF.
N-Methyl and N,N-dimethyl aniline were synthesized to inves-
tigate the importance of the hydrogen bond to Glu 284. (A 5-fold
loss of potency was found going from mono-methyl to di-methyl
consistent with the binding hypothesis.) Several other substitu-
tions were investigated and a selected subset are shown in Table
1. To summarize, addition of unsubstituted cycloalkyls (7–9) re-
sults in a loss in potency relative to the unsubstituted aniline. Upon
introduction of polar functionality in the 4 position of the ring,
most of the binding affinity is restored (10–14). Of note are the
trans and cis isomers of the 1,4 cyclohexyl carboxylic acid (10
9
19
10
2.4
11
12
13
14
15
0.5
45
6.0
5.4
3.2
1.4
16
a
Assay was performed as described in Ref. 9.
and 11). The cis isomer (11) was found to be 3-fold more potent
than the unsubstituted aniline and 4-fold more potent than the
trans isomer (10). Furthermore the ester mixture of cis and trans
isomers (12) was found to lose between one and two orders of
magnitude in potency when compared to the corresponding acids
(10 and 11). Addition of a methylene between the aniline nitrogen
and the cyclohexane ring to give compounds 15 and 16 resulted in
a slight loss in potency when compared to compound 11. Further
investigation of compound 11 showed the molecule to have 13%
oral bioavailability in rats with a short half-life of 1.8 h and clear-
ance of 8.3 ml/min/kg when dosed at 1 mpk.
The most potent series of molecules was found when N-alkyl-
ated piperidines were introduced onto the aniline nitrogen (Table
Figure 2. Co-crystal structure of compound 4 bound within the LFA-1 I domain.
RCSB file name (3BQM).

K. M. Guckian et al. / Bioorg. Med. Chem. Lett. 18 (2008) 5249–5251
5251
Table 2
In addition to the alkyl and cycloalkyl substitutions discussed
above, several other functionalities were investigated. A sulfon-
amide series was designed to increase the acidity of the aniline
N–H and make it a better H-bond acceptor. However, sulfonamide
substitution led to equipotent or less potent compounds and the
PK properties of these compounds were poor relative to that seen
with many of the alkyl-substituted compounds. In addition, urea,
thiourea, amide, and carbamate substitutions were investigated.
None were found to contain the properties seen by the alkyl-
substituted piperidines or cis-cyclohexanecarboxylic acid substitu-
tion (unpublished results).
Piperdine substitutiona
Compound
R
LFA-1/ICAM1-IG IC50 (nM)
1.4
17
To summarize we have designed a series of potent meta-substi-
tuted aniline containing LFA-1/ICAM inhibitors. Several molecules
within this class contain good pharmaceutical properties and are
currently subject to further evaluation.
18
19
20
21
22
0.5
References and notes
1.4
1. Giblin, P. A.; Lemieux, R. M. Curr. Pharm. Des. 2006, 12, 2771.
2. Staunton, D. E.; Lupher, M. L.; Liddington, R.; Gallatin, W. M. Adv. Immun. 2006,
91, 111.
3. Shimaoka, M.; Springer, T. A. Curr. Top. Med. Chem. 2004, 4, 1485.
4. Gottlieb, A.; Krueger, J. G.; Bright, R.; Ling, M.; Lebwohl, M.; Kang, S.; Feldman,
S.; Spellman, M.; Wittkowski, K.; Ochs, H. D.; Jardieu, P.; Bauer, R.; White, M.;
Dedrick, R.; Garovoy, M. J. Am. Acad. Dermatol. 2000, 42, 428.
5. Luo, B.-H.; Carman, C. V.; Springer, T. A. Ann. Rev. Immun. 2007, 25, 619.
6. Gadek, T. R.; Burdick, D. J.; McDowell, R. S.; Stanley, M. S.; Marsters, J. C., Jr.;
Paris, K. J.; Oare, D. A.; Reynolds, M. E.; Ladner, C.; Zioncheck, K. A.; Lee, W. P.;
Gribling, P.; Dennis, M. S.; Skelton, N. J.; Tumas, D. B.; Clark, K. R.; Keating, S. M.;
Beresini, M. H.; Tilley, J. W.; Presta, L. G.; Bodary, S. C. Science 2002, 295, 1086.
7. Winn, M.; Reilly, E. B.; Liu, G.; Huth, J. R.; Jae, H.-S.; Freeman, J.; Pei, Z.; Xin, Z.;
Lynch, J.; Kester, J.; von Geldern, T. W.; Leitza, S.; DeVries, P.; Dickinson, R.;
Mussatto, D.; Okasinski, G. F. J. Med. Chem. 2001, 44, 4393.
0.35
0.9
0.94
7.0
8. Pei, Z.; Xin, Z.; Liu, G.; Li, Y.; Reilly, E. B.; Lubbers, N. L.; Huth, J. R.; Link, J. T.; von
Geldern, T. W.; Cox, B. F.; Leitza, S.; Gao, Y.; Marsh, K. C.; DeVries, P.; Okasinski,
G. F. J. Med. Chem. 2001, 44, 2913.
23
9. Liu, G.; Link, J. T.; Pei, Z.; Reilly, E. B.; Leitza, S.; Nguyen, B.; Marsh, K. C.;
Okasinski, G. F.; von Geldern, T. W.; Ormes, M. J. Med. Chem. 2000, 43, 4025.
10. Zhu, G.-D.; Arendsen, D. L.; Gunawardana, I. W.; Boyd, S. A.; Stewart, A. O.; Fry,
D. G.; Cool, B. L.; Kifle, L.; Schaefer, V.; Meuth, J.; Marsh, K. C.; Kempf-Grote, A.
J.; Kilgannon, P.; Gallatin, W. M.; Okasinski, G. F. J. Med. Chem. 2001, 44, 3469.
11. Liu, G.; Huth, J. R.; Olejniczak, E. T.; Mendoza, R.; DeVries, P.; Leitza, S.; Reilly, E.
B.; Okasinski, G. F.; Fesik, S. W.; von Geldern, T. W. J. Med. Chem. 2001, 44, 1202.
12. Stewart, A. O.; Bhatia, P. A.; McCarty, C. M.; Patel, M. V.; Staeger, M. A.;
Arendsen, D. L.; Gunawardana, I. W.; Melcher, L. M.; Zhu, G.-D.; Boyd, S. A.; Fry,
D. G.; Cool, B. L.; Kifle, L.; Lartey, K.; Marsh, K. C.; Kempf-Grote, A. J.; Kilgannon,
P.; Wisdom, W.; Meyer, J.; Gallatin, W. M.; Okasinski, G. F. J. Med. Chem. 2001,
44, 988.
a
Assay was performed as described in Ref. 9.
2). Both large and small alkyl groups were well tolerated, but acetyl
substitution (23) resulted in a loss in potency. Interestingly, the
tropinone derivative (22) is very potent, demonstrating the large
size of the A ring pocket. In general, molecules in this subseries
were orally available; for example compound 20 was found to have
32% oral bioavailibility and a 7-h half-life when dosed at 1 mpk in
rats.
13. Link, J. T.; Sorensen, B.; Liu, G.; Pei, Z.; Reilly, E. B.; Leitza, S.; Okasinski, G.
Bioorg. Med. Chem. Lett. 2001, 11, 973.
14. Zhu, G.-D.; Staeger, M. A.; Boyd, S. A. Org. Lett. 2000, 2, 3345.
15. Barlow, M. G.; Suliman, N. N. E.; Tipping, A. E. J. Fluor. Chem. 1995, 70, 95.