I. Sellitto et al. / Bioorg. Med. Chem. Lett. 20 (2010) 387–391
391
Table 4
In summary, further SAR investigation in the previously re-
ported sulfonamide series of CB2 agonists, led to the identification
of several compounds (15, 16, 28–31) demonstrating potent affin-
ity for the CB2 receptor (Ki <10 nM) and improved CB1/CB2 receptor
selectivity (>200-fold), when compared to the original lead 8. Com-
pound 14 displayed the best overall in vitro profile and demon-
strated robust efficacy in an animal model of post-operative pain.
The lipophilic amide moiety of 14 was found to be of crucial impor-
tance for potent affinity at the CB2 receptor. Among the various
templates investigated, the xylene moiety of 14 was optimal to ob-
tain good affinity and selectivity for the CB2 receptor while main-
taining moderate in vitro metabolic stability.
Pharmacokinetic parameters of 14 in male Sprague-Dawley rats after iv and po
administration
Pharmacokinetic
iv
po
Dose (mg/kg)
CLs (L/h/kg)
Vdss (L/kg)
1.0
100
—
4.2 0.2
2.5 0.7
0.7 0.1
237 13
—
—
t1/2 (h)
ndc
a
AUC0-1 (ng * h/mL)
4805 2051
6 (6–8)
1221 450
b
Tmax (h)
Cmax (ng/mL)
F (%)
—
—
22
9
Values represent the mean standard deviation of three animals.
a
Expressed as harmonic mean.
Expressed as median and range.
nd: not determined.
b
References and notes
c
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R. G. Pharmacol. Rev. 2002, 54, 161.
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32
28
24
20
16
12
8
Vehicle
*
Compound14 (30 mg/kg i.p.)
Morphine (3 mg/kg i.p.)
*
8. Cheng, Y.; Hitchcock, S. A. Expert Opin. Invest. Drugs 2007, 16, 951.
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4
0
30 MIN
60 MIN
120 MIN
240 MIN
Figure 3. Time course of the in vivo activity of 14 in the rat hindpaw incision
model. Mechanical paw withdrawal thresholds for the left hindpaw, compound 14,
a non-sedating dose of morphine and vehicle treatment groups. Data are plotted as
the mean ( SEM) withdrawal threshold for the left hindpaw. All statistical analysis
was performed with one-way ANOVA followed by post-hoc comparisons (protected
t-test) among groups. * p <0.05 compared to vehicle-treated, surgery group.
Structure–activity relationships at the sulfonamide moiety of
14 were also studied. A 230 member library of sulfonamides, direct
analogs of 14, was prepared and screened at the CB2 receptor. Com-
pounds displaying a CB2 Ki of less than 100 nM were resynthesized
and further purified in order to confirm the binding data obtained
for the library compounds. The results are summarized in Table 3.
We identified from this study several derivatives (e.g., 28–31) dis-
playing +high affinity and selectivity for the CB2 receptors. How-
ever, these compounds all exhibited poor metabolic stability.
Based on its favorable in vitro profile, compound 14 was se-
lected for pharmacokinetic studies. The pharmacokinetic parame-
ters of 14 after iv (1 mg/kg) and po (100 mg/kg) administration
to male rats are summarized in Table 4. Compound 14 demon-
strates high systemic clearance with a short half-life of 0.7 h (iv).
The oral bioavailability of 14 was 22%. Additional in vivo efficacy
studies demonstrated that compound 14 (30 mg/kg, ip) exhibited
a robust antiallodynic effect in the hindpaw incisional rodent mod-
el of post-surgical pain (Fig. 3).
17. Ermann, M.; Riether, D.; Walker, E. R.; Mushi, I. F.; Jenkins, J. E.; Noya-Marino,
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21. Binding assays were performed by modification of the method of: Pinto, J. C.;
Potie, F.; Rice, K. C.; Boring, D.; Johnson, M. R.; Evans, D. M.; Wilken, G. H.;
Cantrell, C. H.; Howlett, A. Mol. Pharmacol. 1994, 46, 516; The [35S]GTP
cS
binding method is a major modification of the method by: Selley, D. E.; Stark,
S.; Sim, L. J.; Childers, S. R. Life Sci. 1996, 59, 659. Additional details are given in
Ref. 19.