R. P. Robinson et al. / Bioorg. Med. Chem. Lett. 20 (2010) 1569–1572
1571
Me
Et
a, b, c
O
3, 4
HO
BnO
OBn
d-g
Me
OBn
Et
Me
Et
O
O
O
O
BnO
OBn
OBn
h- j
BnO
OBn
OBn
k
16
Scheme 3. Reagents and conditions: (a) PhCH(OMe)2/HBF4ÁOEt2/DMF/rt/overnight;
(b) BnBr/Bu4N+IÀ/DMF/0 °C to rt/overnight; (c) LiAlH4/Et2O/CH2Cl2/0 °C then AlCl3/
reflux/3 h; (d) TsCl/Et3N/DMAP/CH2Cl2/rt/24 h; (e) NaI/2-butanone/80 °C/overnight;
(f) CsCO3/DMF/80 °C/25 h; (g) O3/CH2Cl2/À78 °C then Me2S; (h) CH2CHMgBr/THF/
À78 °C/2 h; (i) CH2CHCH2OH/4 Å sieves/montmorillonite K-10 clay/0.5 h; (j)
(PCy3)2(PhCH)RuCl2/CHCl3/rt/0.75 h; (k) Pd/10% HCO2H in MeOH/rt/overnight.
Figure 2. Rat 24 h UGE versus exposure, correcting for SGLT2 potency (BW = body
weight). Male Sprague–Dawley rats (n = 6/group) were randomized to receive one
of five doses of compound 22 (1, 3, 10, 30, 60 mg/kg) or dapagliflozin (2; 10 mg/kg).
Following compound administration, urine was collected over 24 h for measure-
ment of glucose excretion. Simultaneously, drug exposure was assessed in satellite
animals. Compounds 22 and 2 achieved a maximal UGE of 2000–2500 mg/200 g
BW, respectively.
Z
Y
O
a-c
d
3, 4
17, 18
HO
OH
OH
this shorter half-life, maintaining high percent inhibition of the
target over the dosing interval is much more difficult. Indeed, our
modeling of the pharmacokinetic–pharmacodynamic (PK/PD) rela-
tionship for SGLT2 indicates that the dose required to achieve the
maximal rate of UGE increases exponentially in relation to decreas-
ing half-life, in line with the in vivo results for 22. From in vitro
studies using human liver microsomes and hepatocytes (turnover
rates and metabolite identification), it appears that 22 undergoes
glucuronidation on the sugar moiety at an increased rate relative
to 2, leading to a comparatively short in vivo half-life.
In conclusion, based on these studies, we conclude that struc-
tural changes at the C-5 position in the C-aryl glycoside SGLT2
inhibitor series can be well tolerated.20 The C-5 position is the only
position whereby OH deletion does not lead to appreciable loss of
SGLT2 inhibition. This information allowed the design of a series of
novel C-5 spiro analogues, some of which exhibit low nanomolar
potency versus SGLT2 and promote urinary glucose excretion
(UGE) in rats. However, due to sub-optimal pharmacokinetics
(half-life), predicted human doses did not meet criteria for further
advancement.
Scheme 4. Reagents and conditions: (a) TsCl (1.5 equiv)/py/0 °C/overnight; (b) NaI
(1.5 equiv)/2-butanone/80 °C/overnight; (c) NaOMe (9 equiv)/MeOH/0–45 °C; (d)
CH2I2 (9 equiv)/Et2Zn (1 M in hexane; 6 equiv)/CH2Cl2/À10 °C to rt/overnight.
18 ꢀ47-fold; 2: ꢀ860-fold). In PK studies (Table 3), 17 and 18
showed moderate to very high plasma clearance in rats, a species
thatpredicts thehumanclearanceof 2 inhumans quitewell.18 Unex-
pectedly, despite poor oral bioavailability, 17 (administered orally at
10 mg/kg) promoted 24 h UGE similar to the maximal UGE achieved
with 2 in rats (10 mg/kg). We attribute the pharmacodynamic activ-
ity of 17 in rats to formation of a long-lived active metabolite, possi-
bly ketone 25 (Table 2), which was unambiguously identified as a
major metabolite in rats, as well as in rat, dog and human microsome
preparations.
Concomitant with characterization of 17 and 18, synthesis of
additional C-5 spiro analogues continued. This effort provided azeti-
dine 19 (SGLT2 IC50 = 5100 nM), dioxothietane 20 (SGLT2
IC50 = 14 nM), and oxetanes 21–24. Based on the similar potencies
of compounds 2, 3, and 4, the range of activity within the oxetane
series (SGLT2 IC50 ꢀ3–30 nM) was surprising as was the compara-
tively weak activity of 24, bearing the same aryl side chain as that
in 2. Compound 22, having no potential for metabolism to a methyl
References and notes
ketone and being quite potent and selective for SGLT2 (IC50
6.6 nM), was selected for additional profiling.
=
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In rat PK studies, 22 displayed high bioavailability (100%), and
improved clearance (22.3 mL/min/kg) relative to cyclopropyl ana-
logues 17 and 18. However, in rat acute UGE studies, this com-
pound gave disappointing results (Fig. 2). Despite increasing
exposure with dose, 22 was unable to elicit 24 h UGE equal to 2,
even when dosed as high as 60 mg/kg. We attribute this result to
a half-life that is short (1.2 h) compared to that of 2 (4.4 h).19 With
6. Lam, J. T.; Martín, M. G.; Turk, E.; Hirayama, B. A.; Bosshard, N. U.; Steinmann,
B.; Wright, E. M. Biochim. Biophys. Acta 1999, 1453, 297.
Table 3
Rat pharmacokinetic parameters for key compounds
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D. L.; Obermeier, M. T.; Humphreys, W. G.; Robertson, J. G.; Wang, A.; Han, S.;
Waldron, T. L.; Morgan, N. N.; Whaley, J. M.; Washburn, W. N. Bioorg. Med.
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Compd Dose (mg/kg; iv) Cl (mL/min/kg) Vdss (L/kg) t1/2 (h) Fa (%)
219
17
18
22
2
1
1
2
10.0
112
48.9
22.3
3.8
5.7
2.6
2.3
4.4
100
0.59
0.61
1.2
9. Eckhardt, M.; Himmelsbach, F.; Eickelmann, P.; Thomas, L.; Barsoumian, E. L.
U.S. Patent Appl. 2006/0074031 A1.
100
10. Eckhardt, M.; Himmelsbach, F.; Eickelmann, P.; Thomas, L.; Barsoumian, E. L.
U.S. Patent Appl. 2006/0009400 A1.
a
5 mg/kg po.