Cetirizine and loratadine-based antihistamines with 5-lipoxygenase inhibitory activity

Article abstract of DOI:10.1016/j.bmcl.2004.08.060

Three different histaminergic H₁ scaffolds were attached by various linkers to a single 5-LO scaffold. Both activities were observed in vitro. Pharmacokinetic properties of the compounds were evaluated and both a cetirizine-based compound and a

Full text of DOI:10.1016/j.bmcl.2004.08.060

Bioorganic & Medicinal Chemistry Letters 14 (2004) 5591–5594
Cetirizine and loratadine-based antihistamines with
5-lipoxygenase inhibitory activity
Timothy A. Lewis,a,* Michelle A. Young,a Mark P. Arrington,a Lynn Bayless,a
Xiong Cai,a Philippe Collart,b Joseph B. Eckman,a James L. Ellis,a Doina G. Ene,a
Lyn Libertine,a Jean-Marie Nicolas,a Ralph T. Scannell,a Bruce F. Wels,a
Karen Wenberga and Donna M. Wypija
aUCB Research, 840 Memorial Dr., Cambridge, MA 02139, USA
bGlobal Product Safety and Metabolism Department, UCB Pharma SA, Chemin du Foriest, B-1420 Braine l’Alleud, Belgium
Received 15 July 2004; revised 25 August 2004; accepted 26 August 2004
Available online 25 September 2004
Abstract—A series of compounds possessing both H1 histamine receptor antagonist and 5-lipoxygenase (5-LO) inhibitory activities
was synthesized. The H1-binding scaffolds of cetirizine, efletirizine, and loratadine were linked to a lipophilic N-hydroxyurea, the
5-LO inhibiting moiety of zileuton. Both activities were observed in vivo, as was increased CYP3A4 inhibition compared to their
respective single-function drugs. Selected analogs in the series were shown to be orally active in guinea pig models.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Asthma is characterized by bronchial hyperresponsive-
ness and airway inflammation, with more than 50 medi-
ators involved.1 Not surprisingly, monotherapy does not
provide full control of the disease. The combination of
an inhaled corticosteroid with a beta-2 agonist is among
the best available treatment options.2 Histamine and
leukotrienes are key mediators in the pathogenesis of
asthma, being involved in both the early and late phase
asthmatic reactions.3 Clinical trials have demonstrated
the additive benefit of a combined leukotriene (LTD4)
receptor antagonist and H1 receptor antagonist treat-
ment.3,4 A 5-lipoxygenase (5-LO) inhibitor, which de-
creases the biosynthesis of all the leukotrienes, may be
more effective than a LTD4 receptor antagonist when
used concurrently with an antihistamine. An orally ac-
tive dual 5-LO inhibitor/H1 antagonist would provide
a valuable alternative to the currently available thera-
pies, circumventing the poor compliance usually associ-
ated with multiple and/or inhalation therapies.
show an unfavorable physicochemical profile due to
high molecular weight. The lipophilicity of the com-
pounds must not be such as to prevent acceptable oral
bioavailability, yet a certain degree of lipophilicity is
required for cell penetration to reach the intracellular
5-LO target.
We have previously reported the design of dual-function
compounds5 in which the H1 scaffold of cetirizine was
linked to an N-hydroxyurea, the 5-LO inhibiting moiety
of zileuton.6 A furan-based linker resulted in a com-
pound demonstrating dual activities both in vitro and
in vivo. Similar results are obtained replacing the furan
ring with the more metabolically favorable phenyl ring.
In this communication, we report the synthesis of dual-
function analogs in which the same N-hydroxyurea scaf-
fold was attached to three different H1 scaffolds by alkyl
linkers of varying length. We used the H1 scaffolds of the
Cl
O
Balancing H1 receptor antagonist activity and 5-LO
inhibition in a single drug represents a significant chal-
lenge. Such dual-active compounds were predicted to
R
O
N
OH
N
NR
N
Keywords: H1 antihistamine; 5-LO inhibitor.
*
R'
cetirizine R = Cl, R' = H
efletirizine R = R' = F
Corresponding author. Tel.: +1 508 460 5099; e-mail: timlewis1201@
comcast.net
loratadine R = COOEt
desloratadine R = H
0960-894X/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.08.060

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T. A. Lewis et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5591–5594
Compound
n
2
3
4
OH
N
4
5
6
NH2
O
N
N
O
Cl
n
F
OH
N
Compound
n
2
3
4
NH2
7
8
9
O
N
N
O
F
n
OH
N
Compound
n
2
3
4
N
NH2
10
11
12
O
N
O
n
Cl
Figure 1. Dual-function H1/5-LO compounds.
OH
I
b
a
I
HO
Br
O
1
Br
O
OH
d, e
F
NH
c
N
F
8
1
N
O
+
N
2
3
F
F
Scheme 1. Reagents and conditions: (a) BrCH2CH2CH2Br, K2CO3, DMF (52%); (b) 3-butyn-1-ol, PdCl2(PPh3)2, CuI, Et3N, CH2Cl2 (56%);
(c) K2CO3, DMF (64%); (d) N,O-(bisphenoxycarbonyl)hydroxylamine, DIAD, PPh3, THF; (e) NH3/MeOH (60%, two steps).
second-generation antihistamines cetirizine,7 efletiriz-
ine,8 and loratadine/desloratadine.9
using standard assays (Table 1). 5-Lipoxygenase activity
was evaluated in a human whole blood (HWB) assay
monitoring the inhibition of calcium ionophore-induced
LTB4 formation with zileuton as the positive control.14
The three series showed potent inhibitory activity with
IC50 values ranging from 48 to 213nM, that is, at least
The synthetic routes for compounds 4–12 (Fig. 1) were
similar, a representative example is shown in Scheme
1. Alkylation of 4-iodophenol with 1,3-dibromopropane
followed by Sonogashira coupling with 3-butyn-1-ol
gave 1. Compound 1 was then treated with amine 2 to
give 3. Conversion of alcohol 3 to the N-hydroxyurea
8 was performed using a literature procedure.10 For
the cetirizine analogs, enantiomerically pure (R)-1-[(4-
chlorophenyl)-phenyl-methyl]-piperazine11 was used for
the N-alkylation step, the (R)-stereochemistry corre-
sponding to the eutomer of cetirizine, that is, levocetir-
izine.7 Desloratadine, obtained by basic hydrolysis of
loratadine,12 was alkylated with 1 and its analogs to pro-
vide the loratadine-based compounds. Yields for the
synthesis of the other compounds were similar to those
in Scheme 1, except for the alkylation of 4-iodophenol
with 1,2-dibromoethane in which the yield was typically
10–15%.13
Table 1. In vitro H1 and 5-LO activitiesa
Compound
H1 binding
(Ki, nM)
5-LO activity
(HWB, IC50, nM)
4
305 121 (11)
9
213 89 (10)
96 101 (4)
68
5
6 (7)
6
30 16 (2)
295 78 (2)
109 50 (4)
26 26 (25)
19 14 (8)
14 14 (8)
50
7
48
8
90 34 (6)
89 34 (12)
185 81 (10)
194 37 (2)
57
9
10
11
12
Zileuton
Cetirizine
Loratadine
Desloratadine
NT
873 391 (118)
NT
NT
14 6 (60)
414 131 (7)
0.97 0.23 (6)
NT
Compounds 4–12 were tested in vitro for both 5-LO
inhibitory activity and H1 receptor antagonist activity
a Mean SD (n); otherwise n = 1, NT = not tested.

T. A. Lewis et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5591–5594
Table 2. In vitro pharmacokinetic properties
5593
Compound
Caco-2 permeability
(· 10À6 cm/s)
CYP3A4 inhibition
IC50 (lM)
Clint in liver microsomes
(lL/min/mg protein)
A > B
B > A
Rat
Guinea pig
Human
4
1.9
2.3
1.9
3.4
1.4
2.6
1.5
4.6
4.2
5.4
8.6
8.1
18
8
48
108
NT
138
101
NT
19
99
2
0
5
6
6
NT
111
105
NT
NT
13
15
NT
9
6
10
12
6
NT
NT = not tested.
Table 3. In vivo pharmacokinetic and activity profile
Compound
Rat oral/iv dosing at 2mg/kg
Guinea pig, 3h after oral dosing at 2mg/kg
Cmax (ng/mL)
AUC (ngh/mL)
F (%)
Inhibitory activity (%)
Bronchoconstrictiona LTB4 productionb
Plasma levels (ng/mL; lM)
4
10
66
30
300
83
23
8
62
65
4
5
41
84
5
4
187; 350
72; 129
a % Inhibition of bronchoconstriction after histamine-induced challenge.
b % Inhibition of calcium ionophore (A-23187) induced LTB4 formation.
4-fold more potent than zileuton in this assay. Com-
pounds 4, 9 (9 as the fumarate salt), and 10 were further
assessed using the RBL-2H3 cytosolic 5-LO assay.6 The
IC50 values (85 11nM, n = 4; 68 54nM, n = 3; 170,
n = 1, respectively) were found to be in broad agreement
with those measured in intact cells. These findings
demonstrated that the compounds were inhibiting the
intracellular lipoxygenase enzyme.
ity in NADPH-fortified liver microsomes from different
species.19 All of the analogs tested showed higher meta-
bolic clearance (Clint) in rat and guinea pig than in
human. Analog 4 showed the best in vitro metabolic
stability in all three species.
Compounds 4 and 10 were selected for a preliminary
evaluation of their in vivo pharmacokinetic profile and
their oral efficacy after single dosing at 2mg/kg (Table
3). As anticipated from the in vitro data, when com-
pared to 10, the cetirizine-based analog 4 demonstrated
somewhat higher exposure and improved oral bioavail-
ability in the rat. Three hours after single oral dosing
to male guinea pig, both 4 and 10 significantly inhibited
histamine-induced bronchoconstriction (Konzett–Ro¨ss-
ler protocol20) and ex vivo LTB4 production (calcium
ionophore-stimulated whole blood21). The mean plasma
levels were in the range of the concentrations active
in vitro, suggesting that the measured activities directly
derived from the parent drugs. With respect to their
H1 activity, compounds 4 and 10 were found to be less
potent than cetirizine (90% inhibition of histamine-
induced bronchocontriction at 0.5mg/kg).
Human H1 receptor binding was performed using CHO-
K1 cells expressing the recombinant human H1 recep-
tor.15 Cetirizine, loratadine, and desloratadine were used
as the positive controls, our data agreeing with the liter-
ature values.7,8 The three series showed potent H1 bind-
ing activity with Ki values ranging from 9nM (5) to
305nM (4). In the cetirizine/efletirizine series, the 2-car-
bon linker (4/7) consistently led to lower H1 binding
affinity than the 3- or 4-carbon linkers (5/6, 8/9). This
contrasts with the loratadine-containing analogs (10–
12) where linker length had minimal effect.
The next area of focus was to investigate the in vitro
pharmacokinetic properties of these dual-function ana-
logs (Table 2). Intestinal permeability was the primary
concern because of their unfavorable physicochemical
properties (MW > 500, cLogP P 5, up to 13 rotable
bonds). All the tested analogs demonstrated acceptable
apical-to-basolateral permeability in Caco-2 cells
(>1 · 10À6 cm/s).16 However, those derived from the lor-
atadine scaffold (10, 12) showed polarized transport.
This finding might be related to the ability of loratadine
to act as a P-glycoprotein substrate.17 The dual-function
analogs were found to inhibit human CYP3A4.18 Ana-
log 4 was the least inhibitory, with an IC50 of 18lM.
The IC50 values for cetirizine, loratadine, and zileuton
were >100, 32, and >100lM, respectively. Finally, the
analogs were assessed for their in vitro metabolic stabil-
In conclusion, a series of compounds has been devel-
oped combining the scaffolds of various H1 receptor
antagonists with that of zileuton, a reference 5-LO
inhibitor. The resultant dual-function analogs showed
potent in vitro activities. Compounds 4 and 10 were
demonstrated to be bioavailable and orally active in ani-
mal models of respiratory inflammation.
Acknowledgements
We would like to thank the Kilo-lab in Braine-lÕAlleud
for supplying the necessary piperazines.

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10. Stewart, A. O.; Brooks, D. W. J. Org. Chem. 1992, 57,
5020.
References and notes
11. Opalka, C. J.; DÕAmbra, T. E.; Faccone, J. J.; Bodson, G.;
Cossement, E. Synthesis 1995, 766.
1. Barnes, P. J.; Chung, K. F.; Page, C. P. Pharmacol. Rev.
1998, 50, 515.
12. Piwinski, J. J.; Wong, J. K.; Chan, T.; Green, M. J.;
Ganguly, A. K. J. Org. Chem. 1990, 55, 3341.
13. All compounds tested were characterized by 1H NMR,
mass spectral, and IR analysis; purity was >95% as
determined by HPLC analysis with UV detection at
254nM and tandem mass spectral detection.
14. Carter, G. W.; Young, P. R.; Albert, D. H.; Bouska, J.;
Dyer, R.; Bell, R. L.; Summers, J. B.; Brooks, D. W.
J. Pharmacol. Exp. Ther. 1991, 256, 929.
15. Moguilevski, N.; Varsalona, F.; Noyer, M.; Gillard, M.;
Guillaume, J. P.; Garcia, L.; Szpirer, C.; Szpirer, J.;
Bollen, A. Eur. J. Biochem. 1994, 224, 489.
16. Gres, M. C.; Julian, B.; Bourrie, M.; Meunier, V.; Roques,
C.; Berger, M.; Boulenc, X.; Berger, Y.; Fabre, G. Pharm.
Res. 1998, 15, 726.
17. Polli, J. W.; Wring, S. A.; Humphreys, J. E.; Huang, L.;
Morgan, J. B.; Webster, L. O.; Serabjit-Singh, C. S.
J. Pharmacol. Exp. Ther. 2001, 299, 620.
18. Crespi, C. L.; Miller, V. P.; Penman, B. W. Anal. Biochem.
1997, 248, 188.
19. Houston, J. B. Biochem. Pharmacol. 1994, 47, 1469.
20. Konzett, H.; Ro¨ssler, R. Arch. Exp. Pathol. Pharmakol.
1940, 195, 71.
2. Nelson, H. S. J. Allergy Clin. Immunol. 2001, 107,
397.
3. Roquet, A.; Dahlen, B.; Kumlin, M.; Ihre, E.; Gudrun, A.;
Binks, S. Am. J. Respir. Crit. Care Med. 1997, 155,
1856.
4. Wilson, A. M.; Orr, L. C.; Sims, E. J.; Dempsey, O. J.;
Lipworth, B. J. Am. J. Respir. Crit. Care Med. 2000, 162,
1297.
5. Lewis, T. A.; Bayless, L.; Eckman, J. B.; Ellis, J. L.;
Grewal, G.; Libertine, L.; Nicolas, J. M.; Scannell, R. T.;
Wels, B. F.; Wenberg, K.; Wypij, D. M. Bioorg. Med.
Chem. Lett. 2004, 14, 2265; Scannell, R. T. et al. Inflamm.
Res. 2004, 53(Suppl. 1), 313; Selig, W. M.; Bayless, L.;
Libertine, L.; Eckman, J. B.; Wypij, D. M.; Wels, B. F.;
Eckert, M.; Young, M. A.; Nicolas, J. M.; Scannell, R. T.;
Ellis, J. L. Chest 2003, 123, 371.
6. Brooks, C. D.; Stewart, A. O.; Basha, A.; Bhatia, P.;
Ratajczyk, J. D.; Martin, J. G.; Craig, R. A.; Kolasa, T.;
Bouska, J. B.; Lanni, C.; Harris, R. R.; Malo, P. E.;
Carter, G. C.; Bell, R. L. J. Med. Chem. 1995, 38, 4768.
7. Gillard, M.; VanDerPerren, C.; Moguilevsky, N.; Mass-
ingham, R.; Chatelain, P. Mol. Pharmacol. 2002, 61,
391.
21. Spaethe, S. M.; Snyder, D. W.; Pechous, P. A.; Clarke, T.;
VanAlstyne, E. L. Biochem. Pharmacol. 1992, 43,
377.
8. Leeson, G. A.; Castaner, R. Drugs Future 1997, 22, 626.
9. Geha, R. S.; Meltzer, E. O. J. Allergy Clin. Immunol. 2001,
107, 751.