Phenyl-oxazoles, a new family of inverse agonists at the H3 histamine receptor

Article abstract of DOI:10.1002/cmdc.200900446

(Chemical Equation Presented) Drug design: Oxazoles and thiazoles were designed and synthesised based on previously reported ligands of the 3rd histamine receptor (H₃R). The aminopropoxy-phenyl-oxazole chemotype was identified as a promising H<

Full text of DOI:10.1002/cmdc.200900446

MED
DOI: 10.1002/cmdc.200900446
Phenyl-oxazoles, a New Family of Inverse Agonists at the H3 Histamine
Receptor
Frꢀdꢀric Denonne,* Franck Atienzar, Sylvain Cꢀlanire, Bernard Christophe, Frꢀdꢀrique Delannois,
Christel Delaunoy, Marie-Laure Delporte, Vꢀronique Durieu, Michel Gillard, Bꢀnꢀdicte Lallemand,
Yves Lamberty, Geneviꢁve Lorent, Alain Vanbellinghen, Nathalie Van houtvin, Valꢀrie Verbois, and
Laurent Provins[a]
Biogenic amines, such as histamine, are very important in
human physiology. In particular, histamine is implicated in al-
lergy (H1 receptor),[1] gastric secretion (H2R),[2] sleep/wake
cycles or cognition (H3R)[3] and inflammatory/immunological
processes (H4R).[4] The cloning and characterisation of H3R[5]
have allowed many pharmaceutical companies to run high-
throughput screening (HTS) campaigns and successfully come
up with drug candidates. Pfizer, Sanofi-Aventis and Cephalon
all currently have a compound in phase I clinical trials (PF-
3654746,[6] SAR-110894,[7] and CEP-26401 for Alzheimer’s dis-
ease). Moreover GlaxoSmithKline, Johnson & Johnson, Biopro-
jet, Transtech and Schering-Plough each have a compound in
phase II (GSK-239512, BF2.649 and JNJ-31001074 as cognition
enhancers,[8,9] SCH-497079 and HPP-404 against obesity,[10] and
BF2.649 for schizophrenia[11]). A phase II study on another com-
pound, GSK-189254, for the treatment of narcolepsy has re-
cently been terminated.[12] Several other candidates are in pre-
clinical development or have reached some point in develop-
ment for which results are expected in the near future.[13]
the heterocycle, an important feature of their pharmacophore.
We have observed that this particular substitution pattern fa-
vours the rapid hydrolysis of the oxazoline ring in a much
faster reaction than on simple alkyl-substituted oxazolines. This
lower stability could be attributed to the increased protonation
of the ring nitrogen in the presence of a neighbouring amine
(step 1, Scheme 1).[15] Oxazoles were therefore designed to sta-
bilise the heterocycle through aromatisation. Phenyl-oxazoles
bearing an amine attached through a two-carbon linker at po-
sition 4 of the oxazoles have been reported.[16] While active at
H3R, those compounds do not bear the amino-propoxy chain,
which is essential in our series.
Most oxazoles were obtained by the route shown in
Scheme 2 for selected compounds, or a variation thereof.[17]
Condensation of benzamide 8a with dichloroacetone or ethyl
chloroacetoacetate gave the desired oxazoles 9 and 12a in
moderate to good yields. Interestingly, the yield of the conden-
sation reaction with acetoacetates increased fourfold by per-
forming the condensation on the naked phenol 7 rather than
on the corresponding ether 8a (the latter reaction did not pro-
ceed better in DMF).
Introduction of the amine functionality was achieved with
good selectivity, the benzylic chloride in 9 reacted at room
temperature, while its nonactivated counterpart required re-
fluxing acetonitrile and sodium iodide for efficient displace-
ment. The corresponding lactam 14 was rather difficult to in-
troduce by traditional SN2 displacement of a leaving group.
They could be obtained, although with somewhat varying
yields, through acid-catalysed substitution of alcohol 13.
Thiazoles were obtained using the same route after conver-
sion of amide 8a to the corresponding thioamide 8b with
Lawesson’s reagent. As expected, the condensation reaction
with an a-chloroketone to yield 12b occurred more readily
than with oxazoles.
Previously, we reported the discovery of a family of potent
H3R inverse agonists based on the aminopropoxy-phenyl-oxa-
zoline scaffold (I).[14] Herein, we disclose the structurally similar
phenyl-oxazoles and thiazoles (II). They have been designed to
stabilise those oxazolines bearing a second amino group on
Alternatively, the western side chain could be introduced
later in the synthesis, and the oxazole ring obtained separately
attached to the phenyl ring through a Suzuki coupling
(Scheme 3). This last route was particularly useful for the syn-
thesis of phenyl-substituted analogues (35–38).
Compounds bearing a 4-carboxamide group were obtained
by a straightforward condensation of amide 8a with ethyl bro-
mopyruvate, followed by standard functional group intercon-
version (Scheme 4).
[a] Dr. F. Denonne, Dr. F. Atienzar, Dr. S. Cꢀlanire,+ Dr. B. Christophe,
Dr. F. Delannois, C. Delaunoy, Dr. M.-L. Delporte, V. Durieu, Dr. M. Gillard,
B. Lallemand, Dr. Y. Lamberty, Dr. G. Lorent, A. Vanbellinghen,
N. Van houtvin, V. Verbois, Dr. L. Provins
The pyridyl-thiazole derivative 29 was obtained through a
Suzuki coupling of commercially available pyridine boronic
acid 25 followed by substitution on chloropyridine 28 with the
required alcoholate (Scheme 5).
UCB New Medicines, Chemin du Foriest, 1420 Braine-L’Alleud (Belgium)
Fax: (+32)2-3863669
E-mail: Frederic.denonne@ucb.com
[+] Current address: Addex Pharma, Geneva (Switzerland)
206
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2010, 5, 206 – 212

Linker length also had an influence, with the pro-
poxy being the best chain length compromise be-
tween the lower affinity of the ethoxy and the in-
creased lipophilicity of the butoxy (see 40, 41 & 42).
The methylene bridge between oxazole and amine
could also be elongated to an ethylene without
modification of the binding properties (data not
shown).
With the exception of a morpholine moiety (com-
pound 45), which negatively influenced binding,
amines placed on the oxazole ring did not exert sig-
nificant influence (Table 2). This lower affinity could
be attributed to a reduced basicity (pKa =6.0), how-
ever, difluoropiperidine 44 performed much better
with a similar pKa value (pKa =6.1).
Scheme 1. Oxazoline ring opening under acidic conditions.
Conversely, other nonbasic substituents, such as
heterocyclic rings (e.g., compound 47) in the R3 posi-
tion as well as amides (24, 49, 50) and lactams (54) corre-
sponding to the amines above, showed markedly reduced af-
finities. 5-Pyrrolidinomethyl-pyrrolidone 48 was an exception,
however, this probably resulted from the influence of its addi-
tional basic group. Introduction of a methylene spacer (com-
pounds 52, 53) did not improve the affinity. Together with the
morpholine results, this suggested the importance of a basic
group at R3. Switching amines from R3 to R4 while leaving a
methyl group at position 4 improved the affinity somewhat (cf.
56 & 46). As observed for R3, the same trend was observed on
changing amines into amides at R4 (56 vs 59). However, at the
R4 position, amides were much better tolerated especially
when compared to the equivalent ones at R3 (cf. 24 & 57 or 49
& 61).
Overall, all of the compounds tested in the diamine series
gave H3R binding affinities in the 10 nm range and showed
comparable antagonistic profiles (Table 1). Whereas in the oxa-
zoline series, some amines such as 2-methylpyrrolidine[14] gave
spectacular improvements in H3R affinity; the added basic site
on the oxazole moiety seemed to reduce the influence of the
aminopropoxy group on the binding properties of the mole-
cules. This extended to the chirality with a weak twofold differ-
ence between 33 and 34, the enantiomers of 32.
As far as the phenyl ring is concerned, small substituents
had little influence on the affinity when placed ortho to the ox-
azole ring (35, 36). However, substitution closer to the ether in-
creased the affinity by threefold (37, 38).
Scheme 2. Reagents and conditions: a) Cl(CH2)3Br, K2CO3, MEK, 808C; b) Lawesson’s reagent, CHCl3 (85%); c) (ClCH2)2CO, EtCN, 1308C, 3d. (83%); d) piperidine,
MeCN, 228C then 2-methylpyrrolidine, NaI, 808C, 12 h (56%); e) DMF, 1108C, 64 h (82%); e’) MeOH, 1208C, 70 h (Y=O: 23%; Y=S: 100%); f) LiBH4, THF,
MeOH (92%); g) pTsOH, PhMe, rfx (R=H, 95%); h) NaOH, MeOH/H2O (100%); i) (COCl)2, CH2Cl2, cat DMF then morpholine, Et3N, CH2Cl2 5–208C (72%).
ChemMedChem 2010, 5, 206 – 212
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemmedchem.org
207

MED
All compounds tested were inverse agonists as in-
dicated in a GTPgS assay,[18] with EC50 values in the 1–
10 nm range. In particular, the (R) enantiomers of
both morpholine amides 61 and 63 showed the
highest inverse agonism values of the series, with
EC50 values of 9.7 nm and 9.2 nm, respectively, in the
GTPgS assay.
In addition, increasing concentrations of 61 or 63
induced a parallel shift to the right of the maximal
amplitude of the concentration-response curve that
(R)-(À)-a-methylhistamine elicited on the guinea pig
isolated paced ileal myenteric plexus (calculated pA2
value of 9.3Æ0.2 (n=16) or 8.9Æ0.2 (n=16), respec-
tively, Schild slope: 0.77–1.18 as confidence limits at
95%). No decrease in the maximal amplitude of the
curve could be observed in this H3 receptor assay.[19]
These results suggest the existence of a potent com-
petitive antagonism between 61 or 63 and (R)-(À)-a-
methylhistamine on the histamine H3 receptors pres-
ent in this tissue.
Scheme 3. Reagents and conditions: a) BrCH2COCO2Me, EtOH, 908C (75%); b) CuCl,
tBuONO, MeCN, 708C (50%); c) DIBALH, THF, À708C (80%); d) MsCl, Et3N, CH2Cl2 then
(CH2)5NH, MeCN (66%); e) ArB(OH)2, aq K2CO3, Pd(PPh3)4, PhMe, 908C (27–50%); f) H2, Pd/
C, EtOH (67–76%); g) Cl(CH2)3Br, K2CO3, MEK, 808C; h) 2-methylpyrrolidine, NaI, MeCN,
808C, 12 h (45–56%).
In view of their good potential, 61 and 63 were
tested on a panel of 70 different targets (GPCRs,
monoamine transporters and ion channels) and only
showed moderate a2C and s1 affinity, with a 1000-
fold selectivity for H3R. In particular, inhibition of the
related H1, H2 and H4 receptors were below 30% at
10 mm.
Scheme 4. Reagents and conditions: a) ethyl bromopyruvate, EtCN, 1308C (43%);
b) NaOH, EtOH, 708C, 4 h (95%); c) piperidine, HOBt, EDCI, CH2Cl2 (95%); d) 2-methylpyr-
rolidine, NaI, MeCN, 808C, 12 h (53%).
As expected, all compounds were stable in aque-
ous solution between pH 1 and 10 at room tempera-
ture. These compounds contain strongly basic
amines and showed rather low logD values in ac-
cordance with their ionic character at pH 7.4
(Table 3), however, this does not prevent them from crossing
membranes as reflected in the reasonable Caco-2 permeability
values recorded. In addition, all compounds had low in vivo
metabolic clearances, both on microsomes and rat hepato-
cytes. Cytochrome P450 inhibition occurred at reasonably low
levels. Moreover, all compounds had moderate (<80%)
plasma-protein binding (data not shown).
As expected based on in vivo data of permeability and met-
abolic stability, all compounds had good oral bioavailability
when administered to rats (Table 4). All dibasic compounds
shared the same bi-exponential profile. They had a rapid distri-
bution phase followed by a terminal phase characterised by a
long half-life, high total plasma clearance and a very high
volume of distribution. These compounds exhibited low maxi-
mum plasma concentrations (Cmax); their plasma Cmax value was
reached slowly after oral administration.
Scheme 5. Reagents and conditions: a) Pd(PPh3)4, K2CO3, PhMe/EtOH (70%);
b) LiOH, THF/H2O (95%); c) morpholine, EDCI, HOBt, Et3N, CH2Cl2 (89%);
d) NaH, DMF (9%).
Basic lipophilic compounds are known to accumulate exten-
sively in tissues. This is usually explained by nonspecific bind-
ing to cellular membranes and accumulation in acidic lyso-
somes.[20] In our case, this accumulation does not correlate to
the lipophilicity of the compounds (e.g., 46 has a lower logD
value than 32) or to the pKa of the amino-propoxy side chain
(pKa >9.3) but rather to whether or not the compounds con-
tain a second basic group. Indeed, monobasic compounds
such as 61 or 63 showed different PK profiles with much more
Replacement of the phenyl ring with a pyridine resulted in a
dramatic loss of affinity (29), a surprising result considering the
earlier observations with phenyl substituted at this position
(37, 38, Table 1). In contrast with the previous series, R4 substi-
tution allowed for a much greater differentiation between
enantiomers, with a tenfold difference in binding affinities be-
tween the (R) and (S) isomers of 2-methylpyrrolidine deriva-
tives (63 & 64).
208
www.chemmedchem.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2010, 5, 206 – 212

Table 1. Structure and H3R binding affinities (pKi) of diamino-oxazoles.
Table 2. Structure–activity relationship data for oxazoles and thiazoles.
Compd
pKi[a] [nm]
X
Chirality[b]
Compd
10a
pKi[a] [nm]
8.3Æ0.4
8.4Æ0.1
Amine
n
R’
Series
1
H
H
1
2
44
45
8.2
7.4
CH
CH
rac
rac
30
1
1
31
32
33
34
35
36
37
38
8.4Æ0.3
8.2Æ0.1
8.6Æ0.2
8.3Æ0.3
7.8Æ0.1
7.9
H
H
H
H
2
1
1
1
1
1
1
1
46
47
7.9Æ0.2
7.6Æ0.1
CH
CH
rac
rac
1
1
1
1
1
1
1
24
48
7.2
CH
CH
rac
rac
3-F
3-Cl
2-F
8.4
8.4
49
50
7.2
7.6
CH
CH
rac
rac
8.6
2-Me
39
8.4
1
H
1
51
7.5
CH
rac
40
41
42
8.2
0
1
2
H
H
H
2
2
2
8.7Æ0.1
8.4Æ0.1
52
53
54
7.6
CH
CH
CH
rac
rac
rac
7.6Æ0.1
7.7
43
9.0
1
H
1
[a] H3R Binding affinities (pKi) were assessed by displacement of [3H]N-a-
methylhistamine in CHO cell membranes expressing human H3 receptors.
Results are the mean of 2–6 experiments; when only two experiments
were performed the two measurements were within 0.2 log units. [3H]N-
a-methylhistamine: Kd =0.4 nm; assay concentration: 0.2 nm; thiopera-
mide: pKi =6.82Æ0.13 (n>75).
55
56
7.4
8.6
CH
CH
rac
rac
reasonable half-lives, total plasma clearances and volumes of
distribution. This suggests lysosomal trapping rather than
membrane accumulation as the main mechanism of tissue ac-
cumulation.
ChemMedChem 2010, 5, 206 – 212
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemmedchem.org
209

MED
pancy 1 h after ip administration of 1 mgkgÀ1 of 61 & 63, re-
spectively).
Table 2. (Continued)
In view of its favourable PK profile and shorter half-life, we
selected 63 for in vivo testing in animal models of cognitive
deficits.
The promnesiant effect of 63 was evaluated after intraperito-
neal (ip) administration in a two-trial object recognition test[21]
in mice. Scopolamine was used to induce recognition memory
deficits.[22] Full details of the test can be found in the Experi-
mental Section.
Compd
pKi[a] [nm]
X
Chirality[b]
The results of the two-trial object recognition test indicated
that scopolamine blocked recognition memory; the mice spent
an almost equivalent time exploring the familiar and novel
object during the retention trial (Figure 1). Compound 63 was
57
58
7.9Æ0.1
8.3Æ0.2
CH
CH
rac
rac
59
60
61
29
62
63
64
65
7.6Æ0.1
8.3Æ0.1
8.7Æ0.1
7.2
CH
CH
CH
N
rac
rac
R
rac
rac
R
8.2Æ0.3
8.6Æ0.1
7.5Æ0.1
8.3Æ0.1
CH
CH
CH
CH
Figure 1. Promnesiant effect of compound 63 during T2 in the two-trial
object recognition test in mice using scopolamine (0.3 mgkgÀ1, ip) to induce
recognition memory deficit. Results are expressed in terms of mean and
SEM (n=8). A statistical level of significance was set at p<0.01. NS: not stat-
istically significant; *p<0.05 **p<0.01, paired Student’s t-test (two-tailed)
applied on time spent exploring the novel (&) versus the familiar (&)
object. Controls: vehicle only; thioperamide (Thio) at 0.5 mgkgÀ1
.
S
rac
able to significantly prevent scopolamine-induced amnesia in a
dose-dependent manner.[23] This was indicated by the fact that
mice spent more time exploring the novel object compared to
the familiar one. The prototypical H3R antagonist thioperamide,
used as a positive control, was also shown to prevent scopola-
mine-induced deficit.[24] Compound 63 did not alter locomotor
activity (data not shown).
[a] H3R binding affinities (pKi); see footnote in Table 1 for more details.
[b] Chirality: rac=racemic mixture; (R) enantiomer; (S) enantiomer.
Compound 63 was well tolerated in a 4 day toxicity study in
Wistar rats up to a level of 200 mgkgÀ1 (no adverse effect
level), at which point a slight trend towards reduced body
weight gain was observed. No signs of genotoxicity were ob-
served, as measured by induction of DNA repair in bacteria (Vi-
totox)[25] and yeast (GreenScreen).[26] No mutagenic activity was
detected in the mini-Ames test.[27]
Most compounds were evaluated in ex vivo binding studies
on rat cerebral cortex. H3R occupancies were measured 60 min
after administration (ip) of the test compound (1 mgkgÀ1). All
dibasic compounds showed very good brain receptor occu-
pancies (data not shown). Compounds featuring a carbonyl
group on the oxazole or thiazole ring, such as 61 and 63, had
lower penetration levels overall but still maintained sufficient
receptor occupancies (63% and 43% H3 brain receptor occu-
Compound 63 inhibited (IC50 =23.0 mm) the human ether-a-
go-go-related gene (hERG)-encoded channel tail current re-
210
www.chemmedchem.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2010, 5, 206 – 212

Experimental Section
Table 3. In vivo DMPK and physicochemical data for selected compounds.
All experiments were approved by
the local ethics committee for
animal experimentation according
to Belgian law.
Compd
Clearance
R micr[a]
Caco-2[c]
CYP
LogD[e]
pKa
H micr[a]
R hep[b]
2D6[d]
3A4[d]
32
46
61
63
<1
1
26
2
<1
4
9
<3
4
1
49
60
74
75
68
55
7
4
9
2
1.12
0.26
0.84
0.72
9.5/8.3
10.1/9.2
9.6
2
2
10
23
9.7
Two-trial object recognition
test[21]
[a] Human (H) and rat (R) intrinsic clearance in rat microsomes [mLminÀ1 (mg protein]À1]. [b] Intrinsic clearance
on rat hepatocytes [mLminÀ1 (106 cells)À1]. [c] Papps (permeability coefficient determined using the Caco-2 cell
permeability assay): apical-to-basolateral flux following incubation of the given compound at 20 mm with
Caco-2 monolayers for up to 3 h. [d] Cytochrome P450 inhibition on 2D6/3A4 isoforms (% inhibition at 50 mm).
[e] Measured at pH 7.4.
Adult C57 black male mice were
submitted to a habituation session
the day before the object recogni-
tion test and they were allowed to
explore a wooden arena for 30 min
in the presence of two objects. On the day of the experiment mice
were submitted to two trials.
Table 4. In vivo DMPK data for selected compounds.[a]
[b]
[c]
[e]
[f]
1
Compd
Vdss
t =
2
Cl[d]
DNCmax
tmax
F[g]
First trial (T1): mice were placed in an arena containing two identi-
cal objects and the time required to complete 20 s of object explo-
ration was determined with a 20 min cut-off time.
32
46
61
63
240
459
4.8
3.9
12
33
3
286
189
33
2
1
66
73
6
6
1
0.5
59
38
84
50
Retention trial or trial two (T2): performed an hour later, one of the
two objects had been replaced by a novel object, and the time
spent to explore each object was determined for 5 min. Com-
pound 63 (fumarate salt, 1.2–12.5 mgkgÀ1), thioperamide
(0.5 mgkgÀ1, positive control) or vehicle (1% methylcellulose +
5% DMSO in pure water) were administered 40 min before T1 and
scopolamine (0.3 mgkgÀ1) was ip administered 30 min before T1.
2
47
[a] Two animals per route/gender, 1 mgkgÀ1 iv or 6 mgkgÀ1 po; male
Sprague–Dawley rats, vehicle: phosphate buffer pH 7.4 or NaCl 0.9% (32
& 46) or male and female Wistar rats, vehicle: acetate buffer pH 5 in
saline solution (61 & 63). [b] Volume of distribution (LkgÀ1). [c] Half-life.
[d] Clearance (mLminÀ1 kgÀ1). [e] Dose-normalised maximum concentra-
tion (ngmLÀ1). [f] Time to reach maximum concentration. [g] Oral bioavail-
ability (%).
Acknowledgements
corded from HEK293 cells stably transfected with hERG cDNA
using the whole-cell patch clamp recording technique.[28]
Compound 63 changed the shape of the cardiac action po-
tential (threshold of activity 10 mm) recorded intracellularly on
the rabbit isolated Purkinje fibre. From this threshold concen-
tration, a concentration- and inverse-frequency-dependent in-
crease in action potential duration and triangulation was ob-
served, indicating an interaction with the IKr current. At the
higher tested concentration (100 mm) compound 63 induced
1) a decrease in the action potential amplitude and in the de-
polarisation rate, indicating an interaction with the INa+ current
and 2) a depolarisation of the resting membrane potential, in-
dicating a multichannel block. Based on the free plasma con-
centration measured at the dose allowing 50% brain receptor
occupancy[29] (0.038 mm), a safety window of 250-fold could be
estimated for 63.
The authors would like to thank Dr. L. Quere, Mrs. G. Longfils,
and Mrs. L. Ellens for lipophilicity and solubility measurements;
Ms. V. Pinilla for chromatographic purifications; Dr. R. Dieden, Dr.
B. Mathieu, Mr. A. Fauconnier, Mr. J. Claessens, and Mrs. C.
Derwa for analytical assistance; Mr. P. Collart for in vitro PK
measurements, and Dr. D. Harding for cardiac safety assessment.
Mrs. V. Bertaina-Anglade, Mrs. E. Enjuanes, and Mr. C. Drieu la Ro-
chelle (Biotrial) are greatly acknowledged for the testing of com-
pounds in the two-trial object recognition model. The authors are
most grateful to Dr. C. Audouin and Dr. C. Gꢀnicot for their val-
uable comments in the preparation of this manuscript.
Keywords: biological activity
·
cognitive disorders
·
histamine · receptors · structure–activity relationships
In conclusion, we have successfully developed our initial ox-
azoline family of H3R inverse agonists into a larger collection of
more stable oxazoles and thiazoles. We have solved the PK
issues linked to their dibasicity by identifying a more polar,
nonbasic, amide substitution on the oxazole/thiazole ring.
These new compounds have good DMPK profiles and show
convincing antiamnesic effects in a rodent model. Early toxicity
assessment of key candidates showed no sign of toxicity in a
4 day rat toxicity study, no genotoxicity only weak cytotoxicity
and some signs of cardiac effects associated with a moderate
to wide safety window, supporting the therapeutic potential of
63.
[1] G. Barger, H. H. Dale, J. Physiol. 1910, 41, 19–59.
[2] W. Black, W. A. M. Duncan, G. J. Durant, C. R. Ganellin, M. E. Parsons,
Nature 1972, 236, 385.
[3] a) J. M. Monti, Life Sci. 1993, 53, 1331–1338; b) D. Vohora, IDrugs 2004,
7, 667–673; c) M. B. Passani, P. Blandina, Curr. Med. Chem. CNS Agents
2004, 4, 17–26; d) S. Cꢀlanire, F. Lebon, H. Stark in The Third Histamine
Receptor: Selective ligands as potential therapeutic agents in CNS disor-
ders, (Ed.: D. S. Vohora), Taylor & Francis, CRC Press, Boca Raton, 2008,
pp. 103–165 and references therein; e) K. Sander, T. Kottke, H. Stark,
Biol. Pharm. Bull. 2008, 31, 2163–2181; f) M. Wijtmans, R. Leurs, I.
de Esch, Expert Opin. Invest. Drugs 2007, 16, 967–985; g) S. Celanire, M.
Wijtmans, P. Talaga, R. Leurs, I. J. P. de Esch, Drug Discovery Today 2005,
10, 1613–1627; h) R. Leurs, R. A. Bakker, H. Timmerman, I. J. de Esch,
Nat. Rev. Drug Discovery 2005, 4, 107–120.
ChemMedChem 2010, 5, 206 – 212
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemmedchem.org
211

MED
[4] H. D. Lim, R. A. Smits, R. Leurs, I. J. de Esch, Curr. Top. Med. Chem. 2006,
6, 1365–1373; R. L. Thurmond, E. W. Gelfand, P. J. Dunford, Nat. Rev.
Drug Discovery 2008, 7, 41–53.
[5] T. W. Lovenberg, B. L. Roland, S. J. Wilson, X. Jiang, J. Pyati, A. Huvar,
M. R. Jackson, M. G. Erlander, Mol. Pharmacol. 1999, 55, 1101–1107.
[6] http://www.pfizer.com, Pfizer pipeline.
[20] W. A. Daniel, Prog. Neuro-Psychopharmacol. Biol. Psychiatry 2003, 27,
65–73.
[21] a) R. A. Bevins, J. Besheer, Nat. Protoc. 2006, 1, 1306–1311; b) X. Ligne-
au, D. Perrin, L. Landais, J.-C. Camelin, T. P. G. Calmels, I. Berrebi-Ber-
trand, J.-M. Lecomte, R. Parmentier, C. Anaclet, J.-S. Lin, V. Bertaina-An-
glade, C. Drieu la Rochelle, F. d’Aniello, A. Rouleau, F. Gbahou, J.-M.
Arrang, C. R. Ganellin, H. Stark, W. Schunack, J.-C. Schwartz, J. Pharma-
col. Exp. Ther. 2006, 320, 365–375.
[7] Sanofi-Aventis, 1st quarter 2009 financial results.
[8] http://www.gsk.com, product pipeline.
[9] http://clinicaltrials.gov/; ref. number: NCT00880217.
[22] J. C. Dodart, C. Mahis, A. Ungerer, Neuroreport 1997, 8, 1173–1178.
[23] W. M. Westerink, J. C. Stevenson, A. Lauwers, G. Griffioen, G. J. Horbach,
W. G. Schoonen, Mutat. Res. 2009, 676, 113–130.
[24] Rat H3R affinities: compound 63, pKi =7.6; thioperamide, pKi =7.4. Mice
H3R affinities have not been measured but there is 98% homology be-
tween the receptors of the two species: J. Chen, C. Liu, T. W. Lovenberg,
Eur. J. Pharmacol. 2003, 467, 57–65.
[25] A. W. Knight, N. Billinton, P. A. Cahill, A. Scott, J. S. Harvey, K. J. Roberts,
D. J. Tweats, P. O. Keenan, R. M. Walmsley, Mutagenesis 2007, 22, 409–
416.
[26] N. Flamand, J. Meunier, P. Meunier, C. Agapakis-Caussꢀ, Toxicol. in vitro
2001, 15, 105–114.
[10] http://clinicaltrials.gov/; ref. number: NCT00642993.
[11] http://clinicaltrials.gov/; ref. number: NCT00690274.
[12] http://clinicaltrials.gov/; ref. number: NCT00366080.
[13] E. Tiligada, E. Zampeli, K. Sander, H. Stark, Expert Opin. Invest. Drugs
2009, 18, 1519–1531.
[14] S. Cꢀlanire, B. Christophe, P. Collart, I. de Esch, D. Dassesse, C. Delaunoy,
F. Denonne, V. Durieu, M. Gillard, B. Lallemand, Y. Lamberty, F. Lebon, J.-
M. Nicolas, L. Quꢀrꢀ, A. Vanbellinghen, N. Van houtvin, V. Verbois, M.
Wijtmans, H. Timmerman, P. Talaga, R. Leurs, and L. Provins, ChemMed-
Chem 2009, 4, 1063–1068.
[15] For a glimpse at oxazoline metabolism, see L. B. Turnbull, C. P. Johnson,
Y. H. Chen, L. F. Sancilio, R. B. Bruce, J. Med. Chem. 1974, 17, 45–48.
[16] L. S. Beavers, S. L. Boulet, T. P. Finn, R. A. Gadski, W. J. Hornback, C. D. Je-
sudason, R. T. Pickard, F. C. Stevens, G. M. Vaught, (Eli Lilly & Co.),
WO2006019833, 2006.
[27] The affinity (Ki) of compound 63 for rat H3R is 25 nm. It has not been
measured on mice.
[28] Z. Zhou, Q. Gong, Z. Fan, J. C. Makielski, G. A. Robertson, Biophys. J.
1998, 74, 230–241.
[17] For detailed synthetic procedures, see: S. Cꢀlanire, F. Denonne, (UCB
Pharma, S.A.), WO2006103045, 2006.
[29] This ED50 value falls within the range of active doses in the novel object
recognition test.
[18] Inverse agonism activities were measured in a [35S]GTPgS binding assay
in CHO cell membranes expressing human H3 histamine receptors as
described in: T. R. Miller, J. L. Baranowski, B. R. Estvander, D. G. Witte,
T. L. Carr, A. M. Manelli, K. M. Krueger, M. D. Cowart, J. D. Brioni, T. A. Es-
benshade, Assay Drug Dev. Technol. 2008, 6, 339–349.
Received: October 26, 2009
Revised: December 8, 2009
[19] G. K. Menkveld, H. Timmerman, Eur. J. Pharmacol. 1990, 186, 343–347.
Published online on December 30, 2009
212
www.chemmedchem.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2010, 5, 206 – 212