Novel substituted pyrrolidines are high affinity histamine H3 receptor antagonists

Article abstract of DOI:10.1016/j.bmcl.2010.03.071

Pre-clinical characterization of novel substituted pyrrolidines that are high affinity histamine H₃ receptor antagonists is described. These compounds efficiently penetrate the CNS and occupy the histamine H₃ receptor in rat brain following oral administration. One compound, (2S,4R)-1-[2-(4-cyclobutyl-[1,4]diazepane-1-carbonyl)-4-(3-fluoro-phenoxy)-pyrrolidin-1-yl]-ethanone, was extensively profiled and shows promise as a potential clinical candidate.

Full text of DOI:10.1016/j.bmcl.2010.03.071

Bioorganic & Medicinal Chemistry Letters 20 (2010) 2755–2760
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Novel substituted pyrrolidines are high affinity histamine H3 receptor
antagonists
*
Emily M. Stocking , Leah Aluisio, John R. Atack, Pascal Bonaventure, Nicholas I. Carruthers,
Christine Dugovic, Anita Everson, Ian Fraser, Xiaohui Jiang, Perry Leung, Brian Lord, Kiev S. Ly,
Kirsten L. Morton, Diane Nepomuceno, Chandravadan R. Shah, Jonathan Shelton,
*
Akinola Soyode-Johnson, Michael A. Letavic
Johnson & Johnson Pharmaceutical Research & Development L.L.C., 3210 Merryfield Row, San Diego, CA 92121, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Pre-clinical characterization of novel substituted pyrrolidines that are high affinity histamine H3 receptor
antagonists is described. These compounds efficiently penetrate the CNS and occupy the histamine H3
receptor in rat brain following oral administration. One compound, (2S,4R)-1-[2-(4-cyclobutyl-[1,4]dia-
zepane-1-carbonyl)-4-(3-fluoro-phenoxy)-pyrrolidin-1-yl]-ethanone, was extensively profiled and
shows promise as a potential clinical candidate.
Received 16 February 2010
Revised 16 March 2010
Accepted 17 March 2010
Available online 20 March 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Histamine
Histamine H3
The modulation of histamine H3 receptor function is of signifi-
cant interest to neuroscientists. Numerous recent reports have
demonstrated that histamine H3 receptors regulate the sleep–wake
cycle in pre-clinical models and have demonstrated the potential
utility of histamine H3 antagonists for the treatment of various
conditions including ADHD, narcolepsy and Alzheimer’s disease.1
Towards that end, a number of companies have initiated clinical
trials for some of these indications and several reviews covering
the topic have appeared in the recent literature.2–4
amide moiety and aryloxy portion of 4 with replacement of the
central aromatic ring with other linkers as these groups showed
promise in our earlier efforts to prepare dual acting histamine H3
antagonists/SERT inhibitors.
Therefore we began investigating the properties of compounds
with the general structure 5 (Fig. 2), which contains an amide
linked through a heterocyclic ring (A) to an aromatic ring. We
now report one aspect of these efforts in which the A ring is a
pyrrolidine ring derived from proline as in compound 6,
Our foray into the field of H3 receptor antagonists include the
chemotypes shown in Figure 1: propyloxy-piperidines (1),5 2-aryl-
oxymethyl-morpholines (2),6 and (4-aminobutyn-1-yl)benzyl-
amines (3).7
We have also reported the discovery that benzyl amine-based
compounds, such as 4, are dual acting histamine H3 receptor antag-
onists and serotonin transporter (SERT) inhibitors.8 Each of these
chemotypes share structural features consisting of a basic amine
linked by four atoms to a central aromatic core, which is also
substituted by a meta- or para-benzylamine moiety.
N
N
O
N
O
O
O
N
1, hH3 Ki=0.97 nM
2, hH3 Ki=1.9 nM
Cl
Cl
The literature suggests that the most important feature of these
histamine H3 receptor antagonists is the tri-substituted basic
amine linked by four atoms to an aromatic ring.2–4 We were partic-
ularly interested in compounds that retained the piperazine-type
O
N
O
N
H
N
N
N
O
3, hH3 pKi=8.93
4, hH3 Ki=2.4 nM, hSERT Ki=6.3 nM
* Corresponding authors.
E-mail address: mletavic@its.jnj.com (M.A. Letavic).
Figure 1. Histamine H3 antagonist chemotypes.
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.03.071

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E. M. Stocking et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2755–2760
R2
Table 1
R2
Where:
Binding and functional data for the human H3 receptor for compounds 11 and 12
R1
X
R1
O
A=heterocycle
X=O, CH2
R1=alkyl
R2=aryl
R3=H, C1-4alkyl, C(O)C1-3alkyl,
SO2Me or CO2Me
R1
R3
R4
Human H3
Human H3
pA2
N
Compds
N
A
b
Kia (nM)
N
N
N
11a
11b
11c
11d
11e
11f
11g
11h
11i
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Pent
c-Pent
c-Pr
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Bu
H
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
H
5.3 2.2
2.8 0.1
5.2 1.2
4.7 0.8
1.3 0.5
5.0 1.0
2.8 0.1
1.3 0.5
4.1 0.7
3.4 1.7
1.6 0.4
2.0 0.9
2.5 1.5
2.4 0.8
4.1 3.3
3.2 1.4
8.09
O
R3
O
2-Me
3-Me
4-Me
3-Me, 4-Cl
3-OMe
4-SMe
3-Me, 4-Cl
4-CF3
3-F
5
6
8.94 0.06
Figure 2. Substituted pyrrolidines.
8.65 0.04
8.94 0.06
11j
11k
11l
8.68 0.09
8.90
9.02
9.28
8.68
wherein we examined the stereochemistry of the proline ring,
nitrogen substitutions for both R1 and R3 as well as aryl group
substitution, R2.
The initial synthesis of compounds 11 and 12 is outlined be-
low in Scheme 1.9 For the synthesis of the 2R,4S analogs, (2R,4R)-
cis-4-hydroxy-pyrrolidine-2-carboxylic acid (7) was first treated
with (Boc)2O to form 8. The N-Boc protected amino acid 8 was
4-F
4-Cl
3-Cl
4-CN
4-F
4-CN
4-CN
4-F
4-F
4-F
4-F
4-F
4-F
3-F
3-F
3-F
3-F
3-F
3-F
3-F
11m
11n
11o
11p
11q
12a
12b
12c
12d
12e
12f
12g
12h
12i
12j
12k
12l
8.80
9.15
—
23
5
Me
i-Pr
c-Pr
c-Bu
Ac
SO2Me
Ac
Ac
Ac
Ac
Ac
EtO2C
C(O)c-Pr
CH2c-Pr
Ac
Ac
Ac
1.8 0.7
9.13
9.87
12
13
17
4
1
3
then converted to the diazepane amides
9 using standard
methods. Next, a Mitsunobu reaction was utilized to invert the
C-4 stereochemistry to form compounds 10. Subsequent N-Boc
deprotection produced the substituted pyrrolidines as described
in Scheme 1 where R4 is defined as the substituents shown in
Tables 1 and 2. The same procedure outlined in Scheme 1 was
used to prepare compounds 13 and 14 from commercially avail-
able N-Boc-(2S,4R)-trans-4-hydroxypyrrolidine-2-carboxylic acid
using resin bound PPh3.10
Although a number of analogs were made using the synthesis
outlined in Scheme 1, the variability in yield and limited scope of
the Mitsunobu reaction led us to explore other synthetic routes
to prepare the desired compounds 11 and 12.
1.5 1.0
1.2 0.2
1970 560
455 45
51 9.4
Me
i-Pr
i-Bu
c-Bu
c-Bu
c-Bu
c-Bu
c-Pent
THP
Bn
13 4.2
1.6 1.4
9.50 0.16
16
7
12m
12n
12o
12p
12q
7.5 0.8
7.0 0.2
2.2 0.8
69 7.5
150 15
3-F
3-F
3-F
3-F
In Scheme 2, (2R,4S)-trans-4-hydroxy-pyrrolidine-2-carboxylic
acid (15) is converted to 17 as described in Scheme 1 and then 17
is treated with an aryl iodide using copper catalysis to install the
aryloxy substituent with retention of configuration at the
4-position.
a
Ki’s are the mean of at least three experiments in triplicate. Ki s.d. is reported.
The result of a single or duplicate experiment, in triplicate, unless s.d. is shown,
b
then it is the mean of three experiments.
Compounds 18 were also synthesized using the route outlined
in Scheme 2 starting from (2R,4R)-cis-4-hydroxypyrrolidine-2-car-
boxylic acid. This route allowed for higher, more consistent yields
and also allowed for the introduction of heterocyclic aryl rings
using the corresponding aryl iodides. Thus, we also prepared com-
pounds 19 using this route.
tor with an unsubstituted phenoxy substituent (i.e., 11a, Table 1)
and that the addition of small substituents (R4) on the phenoxy
ring were tolerated (11b–q) regardless of their electronic contribu-
tion. Likewise, the heteroaryloxy substituents of 19a–g provided
acceptable affinity for the human H3 receptor. Replacement of
the cyclobutyl ring of the diazepane with other small branched al-
R4
O
R4
O
R4
O
Het
O
N
N
N
N
N
N
N
N
N
N
N
N
R3
R3
R3
R3
O
O
O
O
13
14
18
19
The carbon-linked analogs 20 and 21 were easily prepared as
detailed in Scheme 3 from the commercially available acids 22
and 23 using an amino acid coupling reaction followed by removal
of the Boc protecting group.
kyls was generally well tolerated (i.e., 11o–q, 12j, and 12o), how-
ever a hydrogen (12g), methyl (12h), tetrahydropyran, (12p) or
benzyl substituent (12q) resulted in a significant loss of histamine
H3 binding affinity.
Tables 1–4 detail the human histamine H3 receptor binding and
functional data for representative compounds that were prepared
in this series.11 First, it was determined that the cyclobutyl diaze-
pane amide provided sufficient affinity for the histamine H3 recep-
We also explored additional functionalization of the pyrrolidine
nitrogen (R3). Compounds 12a–g (Table 1) demonstrate that small
substituents on the nitrogen are preferred and that the acetamide
(12e, 12h–k) may be slightly better than the unsubstituted analogs

E. M. Stocking et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2755–2760
2757
R1
OH
OH
OH
N
(a)
(b)
(c)
N
HO
HO
N
N
N
H
O
O
O
O
O
O
O
7
8
9
R4
R4
R4
O
R1
O
R1
R1
O
N
N
N
(e)
(d)
N
N
N
N
N
N
H
R3
O
O
O
O
O
10
11
12
Scheme 1. Synthesis of compounds 11 and 12 from cis-4-hydroxy-pyrrolidine-2-carboxylic acid. Reagents and conditions: (a) (Boc)2O, NaOH, H2O, Dioxane (84%); (b) amine,
EDCI, Et3N, DMF (15–30%); (c) phenol, PPh3, DEAD, THF (15–40%); (d) TFA, DCM (74–98%); (e) RC(O)Cl or RSO2Cl with Et3N in THF or reductive amination.
compounds were also prepared. Compounds 19 (Table 3) demon-
strate that thienyl and pyridyl substituents are tolerated as
replacements for the phenoxy ring in compounds 12 and finally,
the carbon-linked compounds 20a–d and 21a–c (Table 4) have
somewhat lower affinity for the H3 receptor and were not pursued
further as they appeared to be inferior to the 4-aryloxy compounds
11 and 12.
All of the compounds tested for functional antagonism at the
human histamine H3 receptor were found to be potent antagonists
(pA2’s 7.7–9.9, Tables 1–3).11
Based on the in vitro data presented in Tables 1–4, and balanc-
ing in vitro microsomal data, hERG data and binding affinities, sev-
eral compounds were chosen for further screening. Prior to any
in vivo work, we typically verified in vitro functional antagonism
at the rat H3 receptor (i.e., rat pA2), and measured hERG affinity.
Table 5 shows the data for the compounds that were tested. The
compounds tested are all antagonists at the rat H3 receptor and
typically were slightly less potent at the rat H3 receptor than at
the human H3 receptor. Table 2 also shows hERG affinity for these
compounds. Compounds 11l, 11o, and 11p have some affinity for
the hERG channel in this assay. Following up on these initial find-
ings, 11j, 11k, and 12k were screened in a hERG patch clamp assay.
Table 2
Binding and functional data for the human H3 receptor for compounds 13, 14, and 18
R3
R4
Human H3 Kia (nM)
Human H3 pA2
b
Compds
13a
13b
13c
13d
14a
14b
14c
14d
18a
18b
18c
H
4-CN
4-SMe
3-F
4-F
3-F
4-CN
4-SMe
3-F
3-F
4-CN
3-F
184 65
50 13
717 85
55 11
Ac
Ac
c-Pr
H
H
H
Ac
H
H
7.68
37
45
4
1
7.92
143 24
600 230
54 33
89 62
840 440
Ac
a
Ki’s are the mean of at least three experiments in triplicate. Ki s.d. is reported.
The result of a single experiment, in triplicate, unless s.d. is shown, then it is the
b
mean of three experiments.
11. Compounds 13, 14 and 18 (Table 2) reveal that the 2S,4R ste-
reochemistry on the pyrrolidine ring (i.e., compounds 11 and 12)
is preferred for histamine H3 affinity.
In an attempt to alter the metabolism that was observed with
some aryloxy compounds, a few heteroaryloxy and carbon-linked
The compounds had IC50’s of 3.0 lM, 7.8 lM, and 6 lM,
R1
OH
OH
OH
N
(a)
(b)
(c)
N
HO
HO
N
N
N
H
O
O
O
O
O
O
O
15
16
17
R4
R4
R4
O
R1
O
R1
R1
O
N
N
N
(e)
(d)
N
N
N
N
N
N
H
R3
O
O
O
O
O
10
11
12
Scheme 2. Synthesis of compounds 11 and 12 from trans-4-hydroxy-pyrrolidine-2-carboxylic acid. Reagents and conditions: (a) (Boc)2O; (b) amine, EDCI, Et3N, DMF; (c) ArI,
CuI, Cs2CO3, 3,4,7,8-tetramethyl-1,10-phenanthroline, PhCH3, 100 °C (26–50%); (d) TFA, DCM; (e) RC(O)Cl or RSO2Cl with Et3N in THF or reductive amination.

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E. M. Stocking et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2755–2760
Table 5
R4
Functional data for the rat H3 receptor, hERG affinity, and rat in vivo data for select
compounds 11 and 12
R4
N
R.O.c (%)
Plasma/Brain concnd
a
b
Compds
Rat H3 pA2
hERG IC50
(a, b)
HO
N
N
N
11j
11k
11l
11m
11n
11o
11p
12e
12k
8.09
7.93
8.30
8.59
7.90
8.21
8.51
8.64
>10
>10
2.0
7.2
>10
4.6
2.9
>10
>10
95/96
95/96
99/100
97/100
94/97
100/97
96/98
67/46
84/56
3.88/3.70
3.71/3.40
6.55/5.28
9.94/8.16
3.93/3.76
0.56/0.76
0.38/0.40
0.77/0.12
0.72/0.43
H
O
O
O
O
22
20
R4
R4
8.22 0.21
a
The result of a single or duplicate experiment, in triplicate, unless s.d. is shown,
then it is the mean of three experiments.
N
(a, b)
b
HO
N
The result, in lM, of a single experiment measuring the displacement of labeled
N
N
H
dofetilide from the hERG channel.
O
c
O
O
Receptor occupancy (R.O.) at 1 h/3 h after a 10 mpk po dose.
Plasma/Brain concentrations (lM) at 1 h after a 10 mpk po dose.
O
d
23
21
Scheme 3. Synthesis of the 2- and 4-benzyl-pyrrolidine-2-carboxylic acid amides
20 and 21. Reagents and conditions: (a) cyclobutyldiazepane–HCl, EDCI, Et3N, DMF;
(b) TFA, DCM (47–93% over two steps).
was primarily based on the fact that 12k showed robust receptor
occupancy which appeared to be clearing over time therefore the
compound was not likely to have a long tissue half-life. Additional
pre-clinical pharmacokinetic data in rat, dog, and mouse for 12k
are shown on Table 6.
Compound 12k on Table 6 has relatively high clearance, a rela-
tively short half-life and a moderately high Vss in all species tested.
Bioavailability was good (P30%) in rat and dog, but rather low in
mouse.
In a commercial panel of 50 receptor, ion channel and trans-
porter assays (CEREP, www.cerep.com) 12k did not have any sig-
Table 3
Binding and functional data for the human H3 receptor for compounds 19
R3
Het
Human H3 Kia (nM)
Human H3 pA2
8.65
b
Compds
19a
19b
19c
19d
19e
19f
H
H
H
Ac
Ac
Ac
Ac
3-Thienyl
2-Pyridyl
3-Pyridyl
2-Thienyl
3-Thienyl
2-Pyridyl
3-Pyridyl
5.3 0.6
4.6 0.5
2.6 0.2
3.7 0.4
2.7 0.3
5.4 0.3
6.0 0.4
nificant affinity (at 1 lM) for any of the targets that were
9.28
19g
Table 6
Pre-clinical pharmacokinetic data for compound 12ka
a
Ki’s are the mean of at least three experiments in triplicate. Ki s.d. is reported.
The result of a single experiment, in triplicate, unless s.d. is shown, then it is the
b
Species
Cl (mL/min/kg)
Vss (L/kg)
t1/2 (h)
% F
mean of three experiments.
Rat
Dog
Mouse
66
31
76
3.0
2.1
2.8
0.81
0.87
0.51
30
48
5
a
Table 4
For rat and mouse, the compound was dosed 1 mg/kg iv and 10 mg/kg po, for
Binding and functional data for the human H3 receptor for compounds 20 and 21
dog the doses were 1 mg/kg iv and 5 mg/kg po.
Compds
R4
Human H3 Kia (nM)
20a
20b
20c
20d
21a
21b
21c
4-F
3-F
4-CF3
H
H
3-F
4-F
16 8.7
44 12
100
90
80
70
60
50
40
30
20
10
0
200 73
11 (n = 1)
260 150
350 (n = 2)
300 230
PO
SC
a
Except where indicated Ki’s are the mean of at least three experiments in
triplicate. Ki s.d. is reported.
respectively, which is in acceptable agreement with the binding
data shown on Table 5.
Our strategy was next designed to identify compounds with
acceptable brain exposures and clearance after oral administration.
In order to determine whether a compound was likely to be of fur-
ther interest, the compound was dosed po in rats and then plasma
and brain concentrations, as well as ex vivo receptor occupancy,
were measured at 1 and 3 h post dose.11 The results of these
studies are also shown in Table 5. Most of the compounds showed
very high receptor occupancy and fairly high plasma and brain
exposures.
0
4
8
12
16
20
24
Time (hr)
Figure 3. Ex vivo H3 receptor occupancy with compound 12k in rat striatum: time
dependency after oral or subcutaneous administration (10 mg/kg). Results are
expressed as average percentage receptor occupancy versus vehicle treated
rats SEM. (n = 3).
Balancing the in vitro data and receptor occupancy/exposure
data compound 12k was chosen for further studies. This choice

E. M. Stocking et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2755–2760
2759
100
90
80
70
60
50
40
30
20
10
0
120
**
**
90
60
Vehicle
3
10
30
Figure 5. Dose–response effects of compound 12k (3–30 mg/kg sc, n = 7 animals
per dose) on total wake duration (minutes, mean SEM) during the first 4 h
following the administration at the beginning of the light phase. p <0.05, p <0.01,
1
10
100
1000
10000
Plasma Concentration (ng/mL)
*
**
Newman–Keuls post-hoc test following One Way ANOVA.
Figure 4. Ex vivo H3 receptor occupancy with compound 12k in rat striatum: dose
dependency after oral administration. Results are presented as percentage receptor
occupancy versus vehicle treated rats (each data point represents an individual
animal).
The wake promoting properties of 12k in rat were also
investigated by EEG. As detailed in Figure 5, the compound
dose dependently increases total wake time after sc
administration.
Finally, selective histamine H3 antagonist is expected to
modulate the levels of acetylcholine in the brain.12 In order
to verify this was the case for our compound, we used microdi-
alysis experiments in freely moving rats (shown in Fig. 6)
which clearly demonstrate a dose dependent increase in extra-
cellular level of acetylcholine following oral administration of
12k.
In conclusion, we have designed and prepared a series of pyrrol-
idines that are high affinity histamine H3 receptor antagonists. Se-
lected members efficiently penetrate the CNS and occupy the
histamine H3 receptor. One compound, 12k, was extensively char-
acterized, and was found to occupy the rat H3 receptor, promote
wake in rat and to increase the levels of extracellular acetylcholine
in rat cortex. This compound has potential as a clinical candidate
based on its strong pre-clinical profile.
screened. The compound was also evaluated for the potential to be
subject to efflux using a Caco-2 assay. The compound is highly per-
meable (A–B = 13.7 Â 10À6 cm/s, B–A = 52.9 Â 10À6 cm/s) and has
a relatively low potential for efflux (ratio of B–A/A–B = 3.9).
More extensive ex vivo H3 receptor occupancy experiments
were then conducted in order to set doses for pharmacology exper-
iments. Figure 3 shows receptor occupancy versus time in rat fol-
lowing oral and subcutaneous dosing (10 mg/kg) and Figure 4
shows a dose response for receptor occupancy versus plasma con-
centration.11 Good receptor occupancy is achieved following oral
dosing and the compound clears from the H3 receptor quickly over
time.
Figure 3 also shows that 12k achieves maximal (90%) H3 receptor
occupancy in rat at a plasma concentration of ꢀ450 ng/mL, which
considering the differences in affinities for the human and rat hista-
mine H3 receptors (pA2’s 9.50 and 8.33, respectively) should conser-
vatively translate to a human Ceff of under 45 ng/mL, assuming >90%
H3 receptor occupancy is required for efficacy.13
Veh (n=6)
3 mg/kg (n=4)
10 mg/kg (n=6)
B
A
30 mg/kg (n=5)
350
***
15000
10000
5000
0
300
250
200
150
100
50
**
0
-120
-60
0
60
120
180
Time Post Dose (min)
Figure 6. (A) Effects of compound 12k (3, 10, 30 mg/kg po) on extracellular ACh levels from rat prefrontal cortex. (B) Area under the curve values of the data presented in
**
***
P <0.001 versus vehicle Dunnett’s
panel A. All rats were administered the drug after measuring stable baseline. Data represents the means SEM, n = 4–6. P <0.01,
multiple comparison post-hoc following One Way ANOVA.12

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E. M. Stocking et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2755–2760
9. Additional synthetic details and compound characterization are described in
References and notes
Carruthers, N. I.; Letavic, M. A.; Ly, K. S.; Mani, N. S.; Pippel, D. J.; Shah, C. R.;
Soyode-Johnson, A.; Stocking, E. M.; Young, L. PCT Int. Appl. (2009), WO
2009143153 A1.
1. Esbenshade, T. A.; Browman, K. E.; Bitner, R. S.; Strakhova, M.; Cowart, M. D.;
Brioni, J. D. Br. J. Pharmacol. 2008, 154, 1166.
2. Gemkow, M. J.; Davenport, A. J.; Harich, S.; Ellenbroek, B. A.; Cesura, A.; Hallett,
D. Drug Discovery Today 2009, 14, 509.
10. The use of resin bound PPh3 gave incomplete inversion in the Mitsunobu
reaction. Compounds 13 and 14 were separated by reverse phase HPLC (0–99%
MeCN in 20 mM NH4OH) after N-Boc deprotection. Typical yields are shown on
the schemes.
11. The affinity of test compounds for the human recombinant H3 receptor was
determined as described in Ref. 6. Functional data (i.e., pA2 data) and all rat
in vivo data was determined as described in Barbier, A. J.; Berridge, C.; Dugovic,
C.; Laposky, A. D.; Wilson, S. J.; Boggs, J.; Aluisio, L.; Lord, B.; Mazur, C.; Pudiak,
C. M.; Langlois, X.; Xiao, W.; Apodaca, R.; Carruthers, N. I.; Lovenberg, T. W. Br. J.
Pharmacol. 2004, 143, 649.
3. Sander, K.; Kottke, T.; Stark, H. Biol. Pharm. Bull. 2008, 31, 2163.
4. Stocking, E. M.; Letavic, M. A. Curr. Top. Med. Chem. 2008, 8, 988.
5. Apodaca, R.; Dvorak, C. A.; Xiao, W.; Barbier, A. J.; Boggs, J. D.; Wilson, S. J.;
Lovenberg, T. W.; Carruthers, N. I. J. Med. Chem. 2003, 46, 3938.
6. Letavic, M. A.; Keith, J. M.; Ly, K. S.; Bonaventure, P.; Feinstein, M. A.; Lord, B.;
Miller, K. L.; Motley, S. T.; Nepomuceno, D.; Sutton, S. W.; Carruthers, N. I.
Bioorg. Med. Chem. Lett. 2008, 18, 5796.
7. Dvorak, C. A.; Apodaca, R.; Xiao, W.; Jablonowski, J. A.; Bonaventure, P.;
Dugovic, C.; Shelton, J.; Lord, B.; Miller, K.; Dvorak, L. K.; Lovenberg, T. W.;
Carruthers, N. I. Eur. J. Med. Chem. 2009, 44, 4098.
12. Bonaventure, P.; Letavic, M.; Dugovic, C.; Wilson, S.; Aluisio, L.; Pudiak, C.; Lord,
B.; Mazur, C.; Kamme, F.; Nishino, S.; Carruthers, N.; Lovenberg, T. Biochem.
Pharmacol. 2007, 73, 1084.
8. Ly, K. S.; Letavic, M. A.; Keith, J. M.; Miller, J. M.; Stocking, E. M.; Barbier, A. J.;
Bonaventure, P.; Lord, B.; Jiang, X.; Boggs, J. D.; Dvorak, L.; Miller, K. L.;
Nepomuceno, D.; Wilson, S. J.; Carruthers, N. I. Bioorg. Med. Chem. Lett. 2008, 18,
39.
13. The relative binding affinities in rat and human could also be used to estimate
human Ceff. The rat Ki for 12k is 27 nM, therefore the ratio of binding affinities
would suggest a human Ceff of ꢀ30 nM.