M. Packiarajan et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6500–6504
6503
Table 6
Summary of data for selected compounds data15
c
c
d
e
Compound
NPY5 Kia (nM)
cLogP
Solb
(l
g/mL)
hClint (L/min)
rClint (mL/min)
CLp (L/h/kg)
Vss (L/kg)
%Ff
8c
16a
1
12
7.6
1.4
2.82
1.84
4.32
233
690
0.04
2.2
1.8
2.5
72
110
40
23
8.4
1.1
22
47
3.3
49
26
92
a
b
c
d
e
f
For the binding assay description see footnote in Table 1.
The solubility (Sol) measurements see footnote in Table 1.
The hClint and rClint are human (L/min) and rat (mL/min) intrinsic clearances, respectively (see footnote in Table 3).
CLp = plasma clearance (L/h/kg).
Vss = volume of distribution at steady state (L/kg).
%F = absolute oral bioavailability in rats.
10
Fig. 3) similar to that of compound 1.10a,c Pharmacokinetic analysis
of satellite animals from this study indicated that brain and plasma
levels at this dose at the time of the experiment are 4 ng/g and
12 ng/mL, respectively (po dose). The lowest estimated free brain
level (ꢀ1.2 nM, rat fu 3.7%, rat free fraction from brain homoge-
nate) corresponding with efficacy is consistent with the rat Y5
potency (Ki = 5.4 nM).
In summary, we have shown that opening the dihydro-
benzo[2,3]thiepine and cyclohexyl rings of compound 1 and
re-optimization of the aryl and sulfonamide regions resulted in
compounds with moderate to high affinity for the NPY5 receptor.
In general, the 2-pyridyl moiety is preferred over other heterocy-
cles. Sulfonamide 8c and sulfamide 16a analogs were identified
as potent NPY5 antagonists with low cLogP and improved solubil-
ity. However, the high in vivo clearance remains an issue for com-
pounds of this type. Further optimization of 2-pyridyl thiazole
analogs are in progress and will be reported in due course.
9
8
7
6
5
4
3
2
1
0
***
*** p < 0.001
***
vehicle-cPP
Compound 16a-cPP
Veh-Veh
Figure 3. Effect of compound 16a on 1 h food intake in response to cPP.16 Male
Sprague Dawley rats received 0.6 nmol of cPP 1 h after administration of compound
16a (3 mg/kg, po) in 20% cyclodextrin vehicle or vehicle alone. Results are presented
as mean 1 h food intake (g) SEM from 8 to 10 animals per group. Data for each time
point were expressed as food intake in grams relative to the vehicle + cPP group and
analyzed with one-way analysis of variance. The Newman–Keuls test was used for
post-hoc analysis.
Acknowledgments
We thank our colleagues Dahai Dong and Manual Cajina (bioan-
alytical), Priya Rao (formulation), Asanthi Pieris (pharmacokinet-
ics), Martha Vallejo (in vitro metabolism) and Chi Zhang
(physico-chemical) for providing assay support. We acknowledge
Kiho Han and Noel J. Boyle (binding assay) and Natalia Betancourt
(preparation of the NPY cells). Also we thank Dr. John M. Peterson
and Dr. Andrew D. White for their helpful discussions.
treatment of TFA salt of the amine 7 with the corresponding dial-
kylaminosulfonyl chlorides as outlined in Scheme 1. On the other
hand, compounds 16d–16g were synthesized in moderate yields
by heating compound 16a and the respective amines in dioxane
in a sealed tube.
Both the dimethyl 16a and diethyl sulfamide 16c analogs were
potent at the NPY5 receptor with significant improvements in sol-
ubility. The dimethyl sulfamide 16a had comparable in vitro clear-
ance with 8c while the diethyl analog 16c had much higher in vitro
clearance presumably due to its higher lipophilicity (Table 5). Re-
moval of the alkyl substitution 16b or making it larger (16d–16g)
reduced the NPY5 affinity akin to bulkier sulfonamide analogs
(8g–8j).
Compounds 8c and 16a were chosen for evaluation in rat phar-
macokinetic studies (Table 6). Both analogs exhibited much higher
clearance (Clp = 23 and 8.4 L/h/kg) than compound 1 with modest
bioavailabilities (F = 49% and 26%). Compound 16a was selected
for further profiling over 8c because of its high solubility. Profiling
of compound 16a revealed that the compound is selective among
NPY subtypes and did not display cross-reactivity when tested
against an in-house panel of 18 recombinant GPCR targets. Com-
pound 16a is a weak inhibitor of Cytochrome P450 CYP1A2,
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micromolar inhibition of CYP2D6 (IC50 = 950 nM). In rats, com-
pound 16a exhibits low exposure in the brain after 10 mg/kg, po
dosing at 4 h (brain = 12 ng/g; plasma = 24 ng/mL). Compound
16a partially blocked the increase in food intake elicited by
intracerebrovascular (i.c.v.) administration of the NPY5 agonist
[cPP1–7,NPY19-23,Ala31,Aib32,Gln34]-human pancreatic polypeptide
polypeptide (cPP) at a dose of 3 mg/kg, po (ꢀ37% reduction,