4-Phenoxypiperidine pyridazin-3-one histamine H3 receptor inverse agonists demonstrating potent and robust wake promoting activity

Article abstract of DOI:10.1016/j.bmcl.2012.01.026

Structure-activity relationships for a series of phenoxypiperidine pyridazin-3-one H₃R antagonists/ inverse agonists are disclosed. The search for compounds with improved hERG and DAT selectivity without the formation of in vivo active metaboli

Full text of DOI:10.1016/j.bmcl.2012.01.026

Bioorganic & Medicinal Chemistry Letters 22 (2012) 1504–1509
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
4-Phenoxypiperidine pyridazin-3-one histamine H3 receptor inverse
agonists demonstrating potent and robust wake promoting activity
⇑
Robert L. Hudkins , Allison L. Zulli, Reddeppa reddy Dandu, Ming Tao, Kurt A. Josef, Lisa D. Aimone,
R. Curtis Haltiwanger, Zeqi Huang, Jacquelyn A. Lyons, Joanne R. Mathiasen, Rita Raddatz, John A. Gruner
Discovery Research, Cephalon, Inc., 145 Brandywine Parkway, West Chester, PA 19380, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Structure–activity relationships for a series of phenoxypiperidine pyridazin-3-one H3R antagonists/
inverse agonists are disclosed. The search for compounds with improved hERG and DAT selectivity
without the formation of in vivo active metabolites identified 6-[4-(1-cyclobutyl-piperidin-4-yloxy)-
phenyl]-4,4-dimethyl-4,5-dihydro-2H-pyridazin-3-one 17b. Compound 17b met discovery flow criteria,
demonstrated potent H3R functional antagonism in vivo in the rat dipsogenia model and potent wake
activity in the rat EEG/EMG model at doses as low as 0.1 mg/kg ip.
Received 22 November 2011
Revised 4 January 2012
Accepted 9 January 2012
Available online 13 January 2012
Keywords:
Ó 2012 Elsevier Ltd. All rights reserved.
Histamine H3 receptor
H3 inverse agonist
Pyridazin-3-one
CEP-26401
Irdabisant
Sleep–wake
The histamine H3 receptor (H3R) functions in the brain both
as an autoreceptor modulating histamine release and as an
inhibitory heteroreceptor regulating the release of multiple
neurotransmitters, including acetylcholine, dopamine, norepi-
nephrine and serotonin thought to be involved in attention, sleep
and cognition.1 Activation of the H3R results in the inhibition of
N
O
Me
N
O
H
N
N
N
Me
CF3
O
O
N
1a GSK-189254
1b MK-0249
O
O
F
O
N
Et
N
N
H
N
N
F
1c JNJ-31001074
1d PF03654746
R2
H
N
O
N
N
O
N
R4a
R
N
R4b
R5b
O
N
R5a
O
1e CEP-26401 (Irdabisant)
Figure 1. Structures of clinical candidates and 4,5-dihydropyridazin-3-one core.
2
4,5-Dihydropyridazin-3-one series
⇑
Corresponding author.
E-mail address: rhudkins@cephalon.com (R.L. Hudkins).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2012.01.026

R. L. Hudkins et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1504–1509
1505
O
O
a, b
Boc
EtO2C
EtO2C
N
Method A
O
OMe
4
3
c, g, h
c, d
Method B
H
N
R2
N
O
N
O
N
NH
OH
O
6 (R2 = Me)
5a
b, d
e
H
N
R2
O
N
O
N
N
R
N
R
N
O
O
7c (R2 = Me; R = H)
17a R = cBu
5b R = cPent
e
7d-f (R2 = Me)
g
f
7g R2 = 2-Pyr
7a R = cBu
7b R = cPent
Scheme 1. Reagents and conditions: (a) (i) 48% HBr, reflux, (ii) EtOH, 94%; (b) 4-hydroxy-1-Boc-piperidine, PPh3, THF, DEAD, rt, 92%; (c) NH2NH2, or MeNHNH2, 2-propanol,
reflux, R2 = H 50%, R2 = Me 94%; (d) TFA, DCM, 25 °C, 100%; (e) cyclobutanone or, cyclopentanone, NaCNBH3, DMF, MeOH, AcOH, 60 °C, 34–42%; (f) Cs2CO3, DMSO, air, 130 °C,
33–37%; (g) MnO2, xylenes, 155 °C, 75%; (h) BBr3, DCM, 5 °C ? rt, 98%; (g) 2-bromopyridine, K2CO3, CuI, DMF, 150 °C, 45%.
Table 1
Table 2
Pyridazin-3-one H3R binding dataa
Central ring pyridyl analogsa
R2
N
R2
O
N
R
N
O
N
N
R
N
N
R5
O
O
Entry
R2
R
hH3R
(Ki) (nM)
rH3R
(Ki) (nM)
Entry
R2
R5
R
hH3R
(Ki) (nM)
rH3R
(Ki) (nM)
11a
11b
11c
11d
11e
11f
H
H
H
Me
Me
iPr
2-Pyr
iPr
15
6.3
26
1.8
5.9
6.5
34
101
19
51
8.6
12
9.4
82
1e
7a
7b
7c
7d
7e
7f
2.0
1.9
5.1
695
9.2
2.4
2.7
9.8
4.4
7.2
2.2
7.0
>1000
46
3.1
6.0
15
cButyl
cPentyl
cButyl
cPentyl
cButyl
cButyl
H
H
H
H
H
H
H
H
H
Me
cButyl
cPentyl
H
Me
Me
Me
Me
2-Pyr
H
iPr
cButyl
cPentyl
cButyl
cButyl
11g
a
7g
7h
Ki Values are an average of two or more determinations. The assay-to-assay
variation was typically within 2.5-fold; 2-Pyr = 2-pyridyl.
6.3
a
Ki Values are an average of two or more determinations. The assay-to-assay
variation was typically within 2.5-fold; 2-Pyr = 2-pyridy.
including the 4,5-dihydropyridazin-3-one series and amine
replacements.3 An exhaustive SAR direction investigated to iden-
tify second-generation pyridazinone H3R antagonists to irdabisant
was to replace the 4-phenoxypropylamine with the conforma-
tional restricted 4-phenoxypiperidine fragment in both the pyrida-
zin-3-one and non-aromatic 4,5-dihydropyridazin-3-one subseries
2. A similar maneuver was explored by the Merck and Johnson and
Johnson groups on their respective cores.4 In this Letter, we report
the identification and potent wake promoting profile of 6-[4-(1-
cyclobutyl-piperidin-4-yloxy)-phenyl]-4,4-dimethyl-4,5-dihydro-
2H-pyridazin-3-one 17b.
The 6-[4-(piperidin-4-yloxy)-phenyl]-pyridazin-3-ones 7a–f
were synthesized using a Mitsunobu reaction as outlined in
Scheme 1.3b,5 The pyridazinone NH analogs 7a and 7b were synthe-
sized via intermediate 4, which was produced in three steps from
4-(4-methoxy-phenyl)-4-oxo-butyric acid ethyl ester 3 (Method
neurotransmitter release, while blockade of H3R by selective
antagonists or inverse agonists reverses histamine-mediated inhi-
bition and enhances neurotransmitter release. Clinically H3R
antagonists are of interest for potential treatment of multiple
CNS disorders associated with attention and cognitive deficits,
including sleep/wake activity, attention-deficit hyperactivity disor-
der (ADHD), Alzheimer’s disease (AD), mild cognitive impairment,
and the cognitive deficits in schizophrenia.1 Several clinical candi-
dates (1a–1e) have advanced into trials (Fig. 1).1a,f–l We recently
disclosed a novel class of pyridazin-3-one H3R antagonists/inverse
agonists and the profile of the first clinical compound 1e (CEP-
26401, irdabisant).2 A series of publications outlined the pyridazi-
none phenoxypropyl amine structure–activity relationships (SAR)

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R. L. Hudkins et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1504–1509
R2
N
H
N
O
O
N
N
O
N
N
a
e
Cl
N
Cl
Cl
EtO2C
12a, b R2 = Me, iPr
9
8
b
b
R2
N
H
N
O
O
N
N
Boc
Boc
N
N
N
N
O
O
10
13a, b R2 = Me, iPr
c, d
c, d
R2
N
H
O
N
O
N
N
R
R
N
N
N
N
O
O
11a R = iPr
11d R2 = Me; R = cBu
11e R2 = Me; R = cPent
11f R2 = iPr; R = cBu
11g R2 = 2-Pyr; R = cBu
11b R = cBu
11c R = cPent
f
Scheme 2. Reagents and conditions: (a) NH2NH2ꢃH2O, EtOH, 80 °C, 79%; (b) 4-hydroxy-1-Boc-piperidine, 1 M KOtBu, DMSO, 100 °C, 100%; (c) 4 N HCl, dioxane, 50 °C, 100%;
(d) acetone (11a), cyclobutanone (11b,d), cyclopentanone (11c,e), NaCNBH3, DMF, MeOH, AcOH, 80 °C, 10–30%; (e) MeI or iPrI, Cs2CO3, DMSO, air, 100 °C, 79%; (f) 2-
bromopyridine, K2CO3, CuI, DMF, 150 °C, 33%.
Table 3
A). Intermediate 4 was condensed with hydrazine to give the 4,5-
dihydropyridazinone intermediate, followed by deprotection of
the Boc with TFA to produce 5a. Reductive amination of 5a with
4,5-Dihydropyridazin-3-one H3R binding dataa
H
N
O
cyclobutanone or cyclopentanone gave 4,5-dihydropyridazinones
17a and 5b, respectively. Oxidation of 17a and 5b (DMSO/cesium
carbonate) gave targets 7a and 7b in low yield. The route to
N-R2-methyl pyridazinone targets 7d–f was accomplished using
Method B (Scheme 1). Phenol 6 was produced in three steps from
3 and then converted to 7c via Mitsunobu reaction with 4-hydro-
xy-1-boc-piperidine and Boc deprotection as described previously.
Reductive amination with piperidine 7c and acetone, cyclobuta-
none or cyclopentanone gave targets 7d–f. The N-R2 2-pyridyl ana-
log 7g was synthesized from the 4,5-dihydropyridazinone 17a and
2-bromopyridine via copper mediated coupling (Scheme 1). The
central ring 3-pyridyl analogs 11a–g in Table 2 were synthesized
as outlined in Scheme 2. 4-(6-Chloro-pyridin-3-yl)-4-oxo-butyric
acid ethyl ester 8 was reacted with hydrazine hydrate to produce
N
R4
X
N
R5
O
Entry
R4a/R4b
R5a/R5b
X
hH3R
(Ki) (nM)
rH3R
(Ki) (nM)
17a
17b
17c
17d
R(+)17e
S(-)17e
H
H
H
H
H
Me
Me
CH
CH
N
CF
CH
CH
3.7
2.7
12
7.1
5.6
7.8
6.7
4.4
28
7.2
9.6
13
Me/Me
Me/Me
Me/Me
H
H
a
Ki Values are an average of two or more determinations. The assay-to-assay
variation was typically within 2.5-fold.
6-(6-chloro-pyridin-3-yl)-4,5-dihydro-2H-pyridazin-3-one
9
in
high yield. SnAr reaction of 9 with 4-hydroxy-1-Boc-piperidine
and KOtBu in DMSO gave aromatized pyridazinone 1. Deprotection
and reductive amination gave targets 11a–c. The pyridazinone N-
R2 substituted analogs 11d–f were synthesized by alkylation and
aromatization of 9 to 12a and 12b. SnAr reaction, Boc deprotection
and reductive amination as described previously gave 11d–f. The
N-2-pyridyl 11g was produced by copper mediated coupling 11b
analogous to 7g.
The 4,5-dihydro targets in Table 3 were synthesized using pro-
cedures outlined in Schemes 3–5. 6-[4-(1-Cyclobutyl-piperidin-4-
yloxy)-phenyl]-4,4-dimethyl-4,5-dihydro-2H-pyridazin-3-one 17b
was produced from 4-(4-methoxy-phenyl)-2,2-dimethyl-4-oxo-
butyric acid as outlined in Scheme 3 using analogous procedures
described in Scheme 1 for 7a–f. Likewise, 4-(3-fluoro-4-methoxy-
phenyl)-2,2-dimethyl-4-oxo-butyric acid gave 3-fluoro 17g. The
4,4-dimethyl pyridyl 17c was produced starting with 5-bromo-
2-chloro-pyridine as shown in Scheme 4. The key step was conver-
sion of 19 to 20 via metal halogen exchange and reaction of the
3-lithiopyridyl intermediate with 3,3-dimethylsuccinic anhydride.
The 5-methyl racemate 17e was synthesized in five efficient steps
starting with 1-(4-hydroxyphenyl)-propan-1-one (Scheme 5).
Compound 17e was separated using chiral SCF chromatography
to give both isomers in >99% ee. The structure of peak 2 (ChiraPak
1A 4.6 ꢀ 250 mm, 2.5 mL/min, 55% MeOH/0.3% DEA, peak
1
rt = 3.2 min, peak 2 rt = 6.2 min) as the HCl salt was solved by
single crystal X-ray crystallography and the stereochemistry
assigned as the 5-S-methyl isomer. The specific rotations were,
peak 1 R(+)-17 ½a D24
+ 30.5 (c 0.1, MeOH) and peak 2 S(ꢂ)-17
ꢁ
½
a 2D4
ꢁ
ꢂ 29.2 (c 0.1, MeOH).

R. L. Hudkins et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1504–1509
1507
O
O
a, b
R3
R3
O
Boc
HO2C
EtO2C
N
OMe
14 (R3 = H, F)
15
H
H
N
O
N
O
N
N
d, e
R3
O
R3
c
Boc
N
N
O
17b R3 = H
17g R3 = F
16
Scheme 3. Reagents and conditions: (a) (i) 48% HBr, reflux, (ii) ethanol 90%; (b) 4-hydroxy-1-Boc-piperidine, PPh3, THF, DEAD, R3 F = 45%, R3 H = 93%; (c) NH2NH2, 2-propanol,
reflux, 89%; (d) TFA, DCM, 25 °C, 100%; (e) cyclobutanone, NaCNBH3, DMF, MeOH, AcOH, 60 °C, 35–58%.
O
Br
Br
Boc
d, e
HO
Boc
N
N
N
a
b
N
N
O
Cl
O
O
18
19
20
H
N
H
N
O
O
N
N
c
Boc
N
N
N
N
O
O
21
17c
Scheme 4. Reagents and conditions: (a) 4-Hydroxy-1-Boc-piperidine, 1 M KOtBu, toluene, 80 °C, 68%; (b) 3,3-dimethyl-dihydro-furan-2,5-dione, 1.4 M sec-BuLi, ether,
ꢂ78 °C, 35%; (c) NH2NH2ꢃH2O, 2-propanol, 120 °C, 97%; (d) TFA, DCM, 25 °C, 100%; (e) cyclobutanone, NaCNBH3, DMF, MeOH, AcOH, 60 °C, 65%.
O
O
Boc
a
b
N
O
OH
22
23
H
N
O
O
N
Boc
c
EtO2C
N
Boc
N
O
O
24
25
H
N
H
N
H
N
O
O
O
N
d, e
N
N
f
N
O
+17e
7h
g
R(+)17e
S(-)17e
Scheme 5. Reagents and conditions: (a) 4-Hydroxy-1-Boc-piperidine, PPh3, THF, DEAD, 60%; (b) LDA, ethyl bromoacetate, THF, 0 °C; (c) NH2NH2.H2O, 2-propanol, 110 °C, 65%
two steps; (d) TFA, DCM, 25 °C, 100%; (e) cyclobutanone, NaCNBH3, DMF, MeOH, AcOH, 60 °C, 60% two steps; (f) SCF chiral separation; (g) Cs2CO3, DMSO, air, 100 °C, 94%.
The phenoxypiperidine–pyridazinone analogs were tested
using in vitro binding assays by displacement of [3H]NAMH in
membranes isolated from CHO cells transfected with cloned hu-
man H3 or rat H3 receptors as shown in Tables 1–3.2,3 Replacing
the R-2-methyl-pyrrolidinyl propoxy fragment of irdabisant 1e
with N-cyclobutylpiperidinyl (7a hH3R Ki = 1.9 nM, rH3R
Ki = 2.2 nM) and N-cyclopentylpiperidinyl (7b hH3R Ki = 5.1 nM,
rH3R Ki = 7.0 nM) showed comparable affinity (Table 1). Likewise,
the N-methyl pyridazinones 7e and 7f were equally well toler-
ated,3b although the 2-pyridyl 7g had slightly weaker H3R binding
affinity. The SAR at the piperidine nitrogen with compounds 7c–f
showed that the cyclobutyl was optimum. The N-isopropyl 7d pro-
duced a large drop in affinity compared to N-cyclobutyl 7e, while
the piperidine NH compound 7c was essentially inactive. Com-

1508
R. L. Hudkins et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1504–1509
Table 4
*
Pharmacokinetic properties in rata
240
*
7a
17b
S-17e
4.4 1.2
7.6 0.3
23
1226 78
253 21
180
120
60
*
iv
t
½
(h)
2.3 0.4
2.5 0.6
1.9 0.9
3.1 0.4
18
1235 162
270 47
33
*
*
*
Vd (L/kg)
CL (mL/min/kg)
po AUC
Cmax (ng/mL)
F (%)
B/Pb
13
3
2
6
1535 117
441 22
0
35
1
4
56
5
Vehicle 0.01
0.03
0.1
0.3
1
3
10
30
1.9 0.1
4.0 0.6
5.3 0.3
Compound 17b(mg/kg i.p.)
a
Administration at 1 mg/mg iv and 5 mg/kg po; iv formulation (3% DMSO, 30%
solutol, 67% phosphate buffered saline) oral formulation (50% Tween 80, 40% pro-
pylene carbonate and 10% propylene glycol).
Figure 3. Compound 17b-induced wake promotion. Cumulative time awake for 4 h
(4 h AUC) following administration of vehicle or compound 17b in chronically
implanted rats. Mean SEM, n = 8–14/group. ⁄p < 0.05, Dunnett’s post-hoc test
versus vehicle.
b
B/P = brain to plasma ratio measured 6 h post 10 mg/kg ip dose.
pound 7a from this set was selected for additional profiling to
identify potential issues and areas of improvement as a backup
to irdabisant. Compound 7a was a potent, full inverse agonist in
high H3R affinity, but as we observed in the phenoxypropyl series,
in vivo metabolite identification (ID) studies revealed 17a was
metabolized approximately 35% to 7a in the rat, and about 20–
25% in the dog. Based on the formation of an undesired active
H3R metabolite, and findings with the phenoxypropyl series, we
next installed the 5-methyl to potentially block in vivo metabolite
formation.3f Isomers R-17e and S-17e (Table 3) showed compara-
ble H3R binding affinity (Table 3), selectivity, functional activity
the [35S]GTP S hH3R binding assay (EC50 = 1.1 nM)2 and displayed
c
acceptable drug-like properties with low lipophilicity (clogP = 1.5),
high permeability (Caco-2 Papp = 16.5 ꢀ 10ꢂ6 cm/s) and water solu-
bility (pH 2 and pH 7.4 > 1 mg/mL). Compound 7a showed accept-
able in vitro metabolic stability across species in liver microsomes
(t > 40 min in mouse, rat, dog, monkey and human) and IC50 val-
½
ues >30 lM for inhibition of cytochrome P450 enzymes (CYP1A2,
2C9, 2C19, 2D6 and 3A4), indicating low potential for drug–drug
interactions. Compound 7a displayed excellent selectivity over
hH1, hH2, and hH4 receptor subtypes (<10% inhibition at 10 lM)
and when screened against a panel of 63 GPCRs, ion channels
and enzymes it showed activity only for the dopamine transporter
(R-17e Kb,app = 0.6, EC50 = 1.3 nM; S-17e Kb,app = 0.7 nM, EC50
=
1.6 nM) and pharmacokinetics in rat (S-17e, Table 4). The in vivo
rat metabolite ID study revealed R-17e was metabolized about
25% to 7h following oral administration, while the S-isomer was
stable. Further profiling showed incorporation of the S-methyl
(S-17e) improved hERG activity (IC50 = 27
lM) and DAT selectivity
(DAT, 63% inhibition at 10
lM; MDS Pharma Services, LeadProfile
(13% inhibition at 10 M) compared to 7a. However, this
l
screen). The hERG IC50 was 8
l
M in a patch clamp assay. The phar-
compound was later abandoned due to concerns with the fate of
macokinetic (PK) profile in rat showed 7a had a iv half-life of 2.3 h,
moderate clearance and acceptable oral bioavailability and brain
exposure (brain concentration 6 h following a 5 mg/kg po do-
the S-isomer in higher species.
Subsequently, the 4,4-dimethyl phenoxypiperidine analog of
303f was synthesized and profiled (Fig. 2). Compound 17b had high
affinity for both human and rat H3Rs, while the 3-pyridyl 17c and
3-fluoro 17d had slightly weaker binding affinity. Functionally, 17b
was a full inverse agonist (EC50 = 0.8 nM) and showed acceptable
se = 1.4 lM) (Table 4). The hERG selectivity and the DAT activity
required further improvement for a compound to be considered
as a potential backup/second generation wake promoting agent
to irdabisant.2a
in vitro metabolic stability (t > 40 min across species), and cyto-
½
The SAR of the central pyridyl analogs, designed to lower the
clogP and potentially improve hERG activity, is shown in Table 2.
In general, parallel changes in the pyridyl series showed weaker
affinity compared to the phenyl series (compare 11b to 7a, and
11c to 7b). Pyridyl 11b (clogP = 0.9) retained high affinity for
hH3R, but unfortunately did not show an improvement in hERG
chrome P450 selectivity (IC50 > 30
lM). The hERG IC50 value was
21 M and selectivity profiling showed 17b had >1000-fold selec-
l
tivity against hH1, hH2, and hH4 receptor subtypes and against a
panel of 172 GPCRs, ion channels and enzymes (<50% inhibition
at 10 lM; DAT = 8%; MDS Pharma Services, LeadProfiler and Spec-
trum screen). The permeability was classified as high (Caco2
Papp = 27 0.4 ꢀ 10ꢂ6 cm/s) and plasma protein binding for rat,
dog, and human was low to moderate (50–60%). In rat PK studies
selectivity (IC50 = 9 lM) or rat oral bioavailability (%F = 21). Of
note, an opposite SAR trend was observed compared to the phenyl
series when changing the NH-pyridazinone to an N-methyl (com-
pare 11d to 11b, and 11e to 11c).
it showed an iv t < 2 h, with acceptable oral bioavailability and
½
brain exposure (brain concentration 6 h following a 5 mg/kg po do-
We recently reported a series of non-aromatic 4,5-dihydropyri-
dazin-3-one phenoxypropylamines and the wake promoting activ-
ity of compound 30 (Fig. 2).3f A key issue in the phenoxypropyl
series was blocking in vivo metabolism of the 4,5-dihydropyridaz-
inone ring. A similar SAR was explored on the phenoxypiperidine
core for comparison. 4,5-Dihydro-2H-pyridazin-3-one 17a had
se = 2.1 lM) (Table 4).
Compound 17b met all discovery criteria and advanced into
in vivo evaluation in the rat dipsogenia and the rat EEG/EMG
sleep–wake models. The rat dipsogenia model was used as an
in vivo surrogate measure of H3R functional inhibition in the
brain following peripheral administration. Histamine and the
H
H
N
O
N
O
N
N
N
O
N
O
30
17b
hH3R Ki = 4.3 nM
rH3R Ki = 13 nM
hH3R Ki = 2.7 nM
rH3R Ki = 4.4 nM
Figure 2. Design of 17b based on profile of 30.

R. L. Hudkins et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1504–1509
1509
H3-selective agonist, R-a-methylhistamine (RAMH), induce water
References and notes
drinking in the rat when administered either peripherally or cen-
trally, an effect that is blocked by H3R antagonists.1k,2,6 Compound
17b potently and dose-dependently inhibited RAMH-induced
dipsogenia with an ED50 value of 0.14 mg/kg ip. H3R antagonists
including irdabisant and its analogs demonstrated wake promoting
activity in the rat.2b,3a,3f,7 Wake-promoting activity of 17b in the rat
was measured from 0.01 to 30 mg/kg ip as previously described
using rats surgically implanted for chronic recording of EEG (elec-
troencephalographic) and EMG (electromyographic) signals en-
abling wake, slow-wave sleep, and rapid eye-movement sleep to
be scored by standard criteria.2b,8,9 The cumulative wake time at
4 h after dosing (5 h after lights on) was evaluated during the nor-
mal quiet period of the rat. Compound 17b significantly and dose-
dependently increased wake at doses from 0.1 up to 30 mg/kg ip by
4 h AUC values (P < 0.001 ANOVA) (Fig. 3). Doses of 0.1–1 mg/kg in-
creased wake 45–50% above the vehicle value, from 80 5 min
(vehicle group) to 115 4 (0.1 mg/kg), 122 9 min (0.3 mg/kg),
and 116 7 min (1 mg/kg). At 10 mg/kg, percent time awake was
maintained over 90% for the first 2 h after dosing. Wake in the 10
and 30 mg/kg groups was increased to 201 7 and 234 4 min at
4 h (152% and 193%, respectively, compared to vehicle, equivalent
to 84% and 98% time awake for 4 h). At 30 mg/kg, maximal cumu-
lative wake surplus (excess wake time compared to the vehicle
group) was 196 min at 7 h post dosing, which was maintained up
to 22 h. Sleep rebound was not observed in any of the treatment
groups. Compound 17b thus demonstrated very potent wake pro-
motion in rat at doses as low as 0.1 mg/kg ip and robust wake at
higher doses.
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Acknowledgments
The authors thank Emily Kordwitz, Mark Olsen, Gilbert Moa-
chon, Nicole Lepallec, Isabelle Kanmacher, Véronique Agathon,
Mehran Yazdanian and Val Marcy for their assistance and support.