Pyrimidone-based series of glucokinase activators with alternative donor-acceptor motif

Article abstract of DOI:10.1016/j.bmcl.2013.06.036

Glucokinase activators are a class of experimental agents under investigation as a therapy for Type 2 diabetes mellitus. An X-ray crystal structure of a modestly potent agent revealed the potential to substitute the common heterocyclic amide donor-acceptor motif for a pyridone moiety. We have successfully demonstrated that both pyridone and pyrimidone heterocycles can be used as a potent donor-acceptor substituent. Several sub-micromolar analogs that possess the desired partial activator profile were synthesized and characterized. Unfortunately, the most potent activators suffered from sub-optimal pharmacokinetic properties. Nonetheless, these donor-acceptor motifs may find utility in other glucokinase activator series or beyond.

Full text of DOI:10.1016/j.bmcl.2013.06.036

Bioorganic & Medicinal Chemistry Letters 23 (2013) 4571–4578
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Pyrimidone-based series of glucokinase activators with alternative
donor–acceptor motif
b
b
b
b
Kevin J. Filipski a, , Angel Guzman-Perez , Jianwei Bian , Christian Perreault , Gary E. Aspnes ,
Mary T. Didiuk b, Robert L. Dow a, Richard F. Hank b, Christopher S. Jones b, Robert J. Maguire b,
Meihua Tu a, Dongxiang Zeng b, Shenping Liu b, John D. Knafels b, John Litchfield b, Karen Atkinson b,
David R. Derksen b, Francis Bourbonais b, Ketan S. Gajiwala c, Michael Hickey c, Theodore O. Johnson c,
Paul S. Humphries c, Jeffrey A. Pfefferkorn a
⇑
a Cardiovascular, Metabolic, and Endocrine Diseases Chemistry, Pfizer Worldwide Research and Development, 620 Memorial Dr, Cambridge, MA 02139, United States
b Pfizer Worldwide Research and Development, Eastern Point Rd, Groton, CT 06340, United States
c Pfizer Worldwide Research and Development, 10770 Science Center Dr, Building CB2, 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:
Glucokinase activators are a class of experimental agents under investigation as a therapy for Type 2 dia-
betes mellitus. An X-ray crystal structure of a modestly potent agent revealed the potential to substitute
the common heterocyclic amide donor–acceptor motif for a pyridone moiety. We have successfully dem-
onstrated that both pyridone and pyrimidone heterocycles can be used as a potent donor–acceptor sub-
stituent. Several sub-micromolar analogs that possess the desired partial activator profile were
synthesized and characterized. Unfortunately, the most potent activators suffered from sub-optimal
pharmacokinetic properties. Nonetheless, these donor–acceptor motifs may find utility in other glucoki-
nase activator series or beyond.
Received 6 May 2013
Revised 7 June 2013
Accepted 11 June 2013
Available online 20 June 2013
Keywords:
Glucokinase activator
Type 2 diabetes mellitus
Pyrimidone
Ó 2013 Elsevier Ltd. All rights reserved.
Type 2 diabetes mellitus is an expanding worldwide health
problem with current estimates indicating there are >340 million
people with the disease.1 The disease is characterized by elevated
fasting glucose levels, reduced insulin sensitivity, increased hepatic
glucose output, and reduced glucose-stimulated insulin secretion.2
Although several classes of therapies are used as treatment, there
is still significant unmet medical need since patients often do not
meet treatment goals due to modestly efficacious therapies or
undesired side effects such as weight gain.3
One strategy that we have pursued is the development of ‘par-
tial activators’ of the enzyme to increase the dependence of activa-
tion on glucose levels and potentially reduce the hypoglycemia
risk, thereby increasing the therapeutic index. Glucokinase is a
monomeric enzyme with positive cooperativity towards its sub-
strate and its glucose dependency can be justified by several possi-
ble conformations that the complex can adapt.9 One desired profile
for an activator with increased glucose-dependency is where the
Km for glucose is not reduced to the extent observed with previous
Glucokinase is an enzyme that catalyzes the rate-limiting step
in glucose metabolism, namely the conversion of glucose to glu-
cose-6-phosphate.4 Its most characterized functions occur in the
pancreatic beta cells, where it serves as a ‘glucostat’ to effectively
set the threshold for glucose-stimulated insulin secretion; and in
the liver, where it is involved in the regulation of hepatic glucose
utilization and output. Since the initial discovery of small molecule
allosteric activators of glucokinase, there has been a significant
investment to develop these agents as a new class of diabetes ther-
apy.5,6 In fact, several groups have advanced candidates into clini-
cal development;7 however, in these clinical studies, hypoglycemia
risk and uncertainty regarding durability have emerged as
potential challenges.8
activators, namely a (defined as fold-change in Km) P0.1 with min-
imal change in b (ꢀ1; defined as fold-change in Vmax). Previously
communicated work towards these efforts resulted in 1 (Fig. 1)
as a clinical candidate currently in Phase 2 development.10
We subsequently sought to explore whether alternative chem-
otypes might offer additional enzyme activation profiles with
promising therapeutic potential. Of particular interest, an explor-
atory effort identified 2 as a weak glucokinase activator. This com-
pound was noteworthy in that it did not possess the common
heteraromatic amide that was known to provide a key donor–
acceptor interaction within the binding site.6 In comparing the
X-ray crystal structures of 1 (PDB code: 4DHY) and 2 (PDB code:
4L3Q) bound in the allosteric pocket of glucokinase (Fig. 2) it be-
came apparent that the pyridone motif of 2 was mimicking the
heteroaromatic amide of 1. Namely, the carbonyl oxygen was
forming a H-bond with the backbone NH of Arg63, while the
⇑
Corresponding author. Tel.: +1 617 551 3267; fax: +1 617 551 3082.
E-mail address: kevin.filipski@pfizer.com (K.J. Filipski).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.06.036

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K. J. Filipski et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4571–4578
N
N
O
O
N
O
O
N
N
N
H
O
O
N
H
N
H
O
H
?
O
O
O
S
N
N
N
S
S
N
O
O
O
O
3
4
O
1
2
Figure 3. Design hypothesis, incorporating pyridone motif into aryloxy series.
GK EC50 = 0.19 μM
GK EC50 = 2.0 μM
α
α
= 0.10
= 0.20
β = 0.87
β = 0.50
MeO
Br
HO
Figure 1. Glucokinase activators 1 and 2.
a, b
N
OMe
pyridone NH was forming a H-bond with the backbone carbonyl of
the same residue. From this observation we hypothesized that we
may be able to replace the heterocyclic amide with a pyridone in
other chemical series. We sought to evaluate this idea in the
aryloxy series exemplified by 3 (Fig. 3).
OH
6
5
c
O
N
O
d
N
O
8
OH
(A)
S
O
7
O
e
O
O
N+
O-
N
O
H
f
O
O
S
O
S
O
O
O
9
4
Scheme 1. Synthesis of 4. Reagents and conditions: (a) (i) 2-bromopyridine, n-BuLi
(1.6 M in hexanes), THF, –78 °C, 30 min; (ii) ZnCl2, 23 °C, 2 h; (iii) 1-bromo-3,5-
dimethoxybenzene, Pd(PPh3)4, reflux, 20 h, 68%; (b) BBr3, CH2Cl2, –40 to 23 °C, 1 h,
46%; (c) iPrI, K2CO3, DMF, 80 °C, 4 h, 10%; (d) 4-chlorophenyl methylsulfone, KOtBu,
DMSO, 100 °C, 6 h, 30%; (e) mCPBA, CH2Cl2, 23 °C, 3 h, 69%; (f) (i) Ac2O, reflux, 20 h;
(ii) NaOMe, MeOH, 23 °C, 20 min, 25%.
(B)
The synthesis of prototype glucokinase activators are detailed in
Schemes 1–6. Scheme 1 shows the synthesis of pyridone 4. The
zincate of 2-bromopyridine was first formed and then coupled to
1-bromo-3,5-dimethoxybenzene (5). Demethylation of the meth-
oxy groups yielded bis-phenol 6, which was mono-alkylated with
isopropyliodide to give 7. Base-mediated nucleophilic displace-
ment of 4-chlorophenyl methylsulfone provided 8, and finally the
pyridine was converted to the pyridone through the two-step pro-
cedure of pyridine N-oxide formation to give 9, followed by acyla-
tion and rearrangement to result in 4.
Scheme 2 shows the synthesis of pyrimidin-2(1H)-one 17.
p-Methoxybenzyl alcohol non-specifically displaced the chlorides
of 2,4-dichloropyrimidine 10 to provide a major amount of the more
reactive 4-displaced product, 11, and a minor amount of the
2-displaced product, 12, as well as some of the bis-ether.
Separately, resorcinol, 13, was mono-alkylated with isopropyl
iodide and the remaining phenol protected with a tert-butyldimeth-
ylsilyl group to provide 14. This was then regioselectively borylat-
ed11 to yield 15. Boronate 15 was subsequently coupled to 12,
under which conditions partial removal of the silyl group occurred.
TBAF was added to the reaction mixture to fully deprotect the
phenol to produce biaryl 16. Finally, nucleophilic displacement with
4-fluorophenyl methylsulfone, followed by trifluoroacetic acid-
mediated deprotection yielded pyrimidone 17.
N
(C)
O
O
N
H
N
N
H
O
O
S
Ar
Ar
1
O
H
N
O
H
N
2
N
H
N
H
R
R
Arg63
Arg63
Figure 2. Co-crystal structures of human glucokinase allosteric binding site bound
to activators (A) 1 and (B) 2 showing H-bonds to Arg63; and (C) Schematic of
donor–acceptor motif for the heterocyclic amide and pyridone motifs.

K. J. Filipski et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4571–4578
4573
a
Scheme 4 provides a method for the synthesis of several
included pyrimidin-4(3H)-ones. Similar to above, 3,5-
dihydroxybenzonitrile was sequentially mono-alkylated with
isopropyliodide and 4-fluorophenyl methylsulfone, respectively,
to provide nitrile 23. The benzonitrile was then converted to the
benzamidine under ammonium chloride, trimethylaluminum con-
ditions to yield common intermediate 24. This amidine was useful
in synthesizing several analogs based on the condensation partner
used. Ethyl propiolate provided the unsubstituted pyrimidone 25,
ethyl 2-formylpropionate formed the 5-methylated analog 26,
while ethyl acetoacetate yielded the 6-methyl version, 27.
The method shown in Scheme 5 for the synthesis of 30 was used
in the preparation of multiple analogs using the appropriate sub-
stituents to access a variety of compounds. Boronic ester 15 was
first coupled to chloro pyrimidine 11 to provide 28. This biaryl spe-
cies was then copper-coupled12 to bromide 29, whose synthesis
has been detailed previously,10 followed by p-methoxybenzyl
deprotection with trifluoroacetic acid to access final compound 30.
Scheme 6 shows an alternative method that was used in the
synthesis of multiple compounds including 36. 5-Bromobenzene-
1,3-diol, 18 was first bis-silyl protected under standard conditions
to give 31 and then the boronate was formed and coupled to chlo-
ride 11 to provide biaryl 32 after deprotection. Separately, chiral
diol 33 was mono-protected to form 34 and then 32 was alkylated
with 34 under Mitsunobu conditions to give 35. Finally, phenol 35
displaced 4-fluorophenyl methylsulfone and the p-methoxybenzyl
group removed with acid to arrive at analog 36.
N
N
N
Cl
N
OPMB
PMBO
N
Cl
Cl
N
Cl
12
11
10
+
O
B
HO
O
b, c
d
O
O
OH
OTBDMS
14
OTBDMS
13
15
e
N
S
O
N
N
H
O
f
O
N
OPMB
O
OH
O
O
17
16
Scheme 2. Synthesis of 17. Reagents and conditions: (a) (i) PMB-OH, NaOtBu, THF,
reflux, 1 h; (ii) 10, DMF, –70 to 23 °C, 2 h, 62% 11 and 10% 12; (b) iPrI, K2CO3, DMF,
23 °C, 14 h, 42%; (c) TBDMS-Cl, imidazole, CH2Cl2, 23 °C, 1 h, 90%; (d) bis(pinaco-
lato)diboron, (1,5-cyclooctadiene)(methoxy)iridium(I) dimer, 4,40-di-tert-butyl-
2,20-dipyridyl, mtbe, 100 °C, microwave, 10 h; (e) (i) 12, Pd(dppf)Cl2, Na2CO3, 3:1
DME:H2O, 70 °C, 13 h; (ii) TBAF, THF, 23 °C, 1 h, 70%; (f) (i) 4-fluorophenyl-
methylsulfone, K2CO3, DMF, 120 °C, 13 h; (ii) TFA, 23 °C, 30 min, 34%.
Biochemical evaluation of all analogs utilized a matrix assay
that has been previously described.10 Briefly, the human recombi-
nant glucokinase-containing assay was run at 22 different activator
O
Br
O
CN
HO
Br
HO
CN
a
a, b
O
O
OH
18
OH
S
O
S
23
22
19
O
O
O
c
b
NH
N
N
N
O
N
O
NH2
N
H
O
O
O
OtBu
N
H
O
d
e
O
c
O
O
O
S
O
24
S
25
O
O
O
S
S
f
O
O
O
O
21
20
N
O
N
Scheme 3. Synthesis of 21. Reagents and conditions: (a) (i) (4-fluorophenyl)-
methylsulfone, NaH (60%), DMF, 23–70 °C, 16 h; (ii) iPrI, K2CO3, 65 °C, 24 h, 14%; (b)
2-(tert-butoxy)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyrazine,
Pd(dppf)Cl2, K3PO4, DMF, H2O, 80 °C, 16 h, 60%; (c) TFA, CH2Cl2, reflux, 1 h, 56%.
N
H
O
O
N
O
H
O
O
S
The synthesis of pyrazinone 21 is depicted in Scheme 3. Here,
5-bromobenzene-1,3-diol, 18, was first mono-arylated with the
fluorophenyl sulfone under base-mediated displacement condi-
tions followed by similar alkylation to install the isopropyl moiety
to provide 19. Palladium coupling with 2-(tert-butoxy)-6-(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)pyrazine provided 20 and
finally the tert-butyl group was removed with trifluoroacetic acid
to give pyrazinone 21.
O
O
26
S
O O
27
Scheme 4. Synthesis of 25, 26, and 27. Reagents and conditions: (a) iPrI, K2CO3,
DMF, 65 °C, 16 h, 37%; (b) 4-fluorophenyl-methylsulfone, NaH (60%), DMF, 0–85 °C,
16 h, 78%; (c) NH4Cl, Me3Al (2 M in toluene), toluene, 0–110 °C, 36 h; (d) ethyl
propiolate, NaOEt (21% in EtOH), EtOH, 0–80 °C, 16 h, sealed tube, 25%; (e) ethyl 2-
formylpropionate, NaOEt (21% in EtOH), EtOH, 85 °C, 16 h, 59%; (f) ethyl acetoac-
etate, NaOEt (21% in EtOH), EtOH, 85 °C, 16 h.

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K. J. Filipski et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4571–4578
Glucokinase at 20 mg/mL was crystallized in the presence of
N
40 mM glucose and 1 mM 1 or 2. Crystallization drops in a 1:1 ratio
were set up over wells containing 0.1 M TrisHCl pH 7.0,
80–200 mM glucose, and 19–26% PEG-4000. Structures were
solved using molecular replacement method. Human liver micro-
somal clearance (HLM),14 rat liver microsomal clearance (RLM),
kinetic aqueous solubility, passive permeability flux performed in
a low transporter-expressive cell line, MDCKII-LE,15 and logD
performed by the shake flask method, were also used to further
characterize final compounds. The kinetic solubility assay was
performed as follows: 50 mM sodium phosphate buffer, at pH
6.5, was freshly prepared from NaH2PO4 and Na2HPO4 and filtered.
a
O
N
OPMB
15
OH
28
Br
N
N
N
N
b
N
O
N
H
O
N
O
29
Buffer (294 lL) was combined with 6 lL of 30 mM DMSO stock
O
N
solution in a Millipore polycarbonate filter solubility plate (part#
MSSLBPC10) for a final DMSO concentration of 2%. The plates were
heat sealed with a polypropylene seal. After 24 h of 200 rpm
shaking at room temperature (23–25 °C), the plates were vacuum
filtered into deep well receiver plates. Filtrates were injected into
a chemiluminescent nitrogen detector (Antek 8060) for quantifica-
tion. Apparent concentration was divided by the number of nitro-
gens in the sample (from the molecular formula) to determine the
concentration.
O
30
Scheme 5. Synthesis of representative analog 30. Reagents and conditions: (a) (i)
11, Pd(dppf)Cl2, Na2CO3, 3:1 DME:H2O, 70 °C, 19 h; (ii) TBAF (1 M in THF), THF,
23 °C, 90 min, 37%; (b) (i) 29, CuCl, 2,2,6,6-tetramethylheptane-3,5-dione, Cs2CO3,
DMF, 120 °C, 15 h, sealed tube; (ii) TFA, CH2Cl2, 23 °C, 10 min, 65%.
Our design hypothesis of replacing the heterocyclic amide with
a pyridone was confirmed with 4 (Table 1) having sub-micromolar
potency, while reducing molecular weight and increasing polarity
as compared to amide 3, leading to a modestly higher lipophilic
efficiency (LipE).16 Several other properties also were improved,
namely passive permeability, kinetic solubility, and human micro-
N
TBDMSO
Br
b
HO
a
N
OPMB
18
OTBDMS
OH
OH
somal clearance. Gratifyingly, this compound also had a higher
a
32
31
(i.e., less substantial reduction in the enzyme’s Km for glucose),
indicating the potential for increased glucose dependency relative
benchmark candidate 3, as discussed above.
(R)
(R)
c
OH
d
A nitrogen-walk around the pyridine of 4 was first performed.
The pyrimidin-2(1H)-one, 17, and pyrazinone, 21, were much less
active, while the pyrimidin-4(3H)-one, 25, was equipotent with
still desirable activation profile. Since the logD was reduced from
the pyridone lead, this compound had improved LipE, as well as
improved permeability and solubility, and so was deemed to be a
superior motif and was used in subsequent optimization. Based
on the crystal structure and the overlap with the heterocyclic
amide motif it was envisioned that building off the 5-position
would be sterically tolerated while the 6-position appeared less
promising. This hypothesis played out with the 5-methyl analog,
26, having improved potency and ligand efficiency (LE = 0.33 for
26 vs 0.31 for 25),17 and maintained LipE; while the 6-methyl
homolog, 27, lost significant activity. Therefore additional substitu-
tions were examined in the 5-position as shown in Table 2.
An SAR trend with small alkyl substituents, 26, 37, and 38,
shows that ethyl, 37, is optimal for potency. Replacing the ethyl
with the isosteric methoxy group, 39, shows a loss in potency.
Noteworthy, is that electron-donating substituents, as in 26 and
37–39, are significantly more potent than electron-withdrawing
substituents 40 and 41, even for the similarly sized and lipophilic
chloro compared to methyl or ethyl. This suggested the importance
of the strength of the H-bonding between the pyrimidone carbonyl
and NH with the binding site residue. Specifically, the anticipated
pKa of the pyrimidone NH with an electron-withdrawing group
present is low enough where at physiological pH a significant per-
centage of the deprotonated compound will be present; eliminat-
ing the H-bond interaction and creating an electronic repulsion.18
Exploration of SAR around the O-aryl ring is shown in Table 3.
Several heterocycles and substituents were incorporated as was
done in related series.10,19 Sulfone (25), sulfonamide (42), and
amide substituents (30, 43, and 44) all showed good to moderate
activity, while large improvements in LipE and kinetic solubility
were demonstrated with pyridyl (43), pyrimidyl (30), and
TiPSO
HO
33
34
N
(S)
O
N
(S)
HO
N
H
O
O
e
HO
N
OPMB
O
OH
S
O
35
O
36
Scheme 6. Synthesis of representative analog 36. Reagents and conditions: (a)
TBDMS-Cl, imidazole, DMF, 23 °C, 3d, 89%; (b) (i) tBuLi (1.7 M in pentane), B(OMe)3
THF, ꢁ78 to 23 °C, 16 h; (ii) 11, Pd(dppf)Cl2, Na2CO3, DME, H2O, 65 °C, 16 h; (iii)
TBAF, THF, 23 °C, 1 h, 59%; (c) TiPS-Cl, DIEA, imidazole, CH2Cl2, DMF 23 °C, 2d, 84%;
(d) PPh3, DIAD, THF, 23 °C, 24 h, 33%; (e) (i) 1-(ethylsulfonyl)-4-fluorobenzene,
K2CO3, DMF, 80 °C, 3 h; (ii) TFA, 23 °C, 1 h.
concentrations (0–100 lM) and 16 different glucose concentra-
tions (0–100 mM). A nonessential activator model was utilized to
determine an activator’s maximum fold effect on reducing the glu-
cokinase Km for glucose, defined as
on altering the Vmax, defined as b.13 The
glucokinase Km at maximum activator concentration divided by
the enzyme’s Km in the absence of activator. Values of range from
0 to 1 with lower values representing more substantial reductions
in the enzyme’s glucose Km. The b value is defined as the ratio of
the enzyme’s velocity at maximum activator concentration divided
by the enzyme’s velocity in the absence of activator. Values >1
indicate increases in the Vmax with activator present, b = 1 indicates
no effect on Vmax, and values <1 indicate suppression of the Vmax
with activator present. The EC50 was formally defined as the con-
centration of activator affording a half-maximal reduction in Km.
a
, and the maximum fold effect
a
value is the ratio of the
a

K. J. Filipski et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4571–4578
4575
Table 1
Properties of glucokinase activators 3, 4, 17, 21, 25–27a
O
R
O
S
O
O
M) ab
bb
MW
logD
LipE
Permeability
(10ꢁ6 cm/s)
Solubility
M)
HLM Clint
(mL/min/kg)
RLM Clint
(mL/min/kg)
b
d
R
EC50
(l
(
l
O
3
0.11c
0.07c
1.09c
440
399
400
4.05
2.82
ND
3.22
3.62
—
4.4
18
1.4
11
17
97
N
H
N
O
O
4
0.74 0.33
>100c
0.14 0.01
0.75 0.03
<8.0
ND
349
ND
N
H
N
17
—
—
ND
ND
N
H
N
21
23.0 4.3
<0.37 0.05
0.83 0.08
400
2.27
2.66
94
118
11
61
N
H
O
O
O
N
N
25
26
0.83 0.33
0.20 0.05
0.10 0.01
0.14 0.03
1.12 0.02
0.83 0.07
400
414
2.14
2.68
4.25
4.33
24
17
25
<9.8
<8.0
105
189
N
H
1.9
N
H
N
27
10.3c
0.49c
0.40c
414
2.43
2.86
4.8
15
<8.0
96
N
H
O
a
b
c
ND = Not Determined.
Biochemical data reported as the geometric mean SD of P2 determinations except where indicated.
Data from n = 1 determination.
LipE = ꢁlog (EC50) – logD.
d
Table 2
Properties of glucokinase activators 37–41a
R
O
N
O
N
H
O
S
O
O
ab
bb
MW
logD
LipE
Permeability
(10ꢁ6 cm/s)
Solubility
M)
HLM Clint
(mL/min/kg)
RLM Clint
(mL/min/kg)
b
d
R
EC50
(l
M)
(
l
37
38
39
40
41
Et
0.07 0.01
0.59c
0.16 0.01
0.20c
0.66 0.06
0.43c
428
442
430
418
425
3.11
ND
2.21
2.04
ND
4.33
—
4.12
3.39
—
4.0
ND
3.9
8.3
ND
5.7
ND
7.1
24
<8.0
ND
<8.0
<8.0
ND
171
ND
<25.4
<25.4
ND
iPr
OMe
Cl
0.94 0.19
0.26 0.03
0.73 0.01
7.5c
0.14c
1.00c
CN
9.2c
0.37c
0.78c
ND
a
b
c
ND = Not Determined.
Biochemical data reported as the geometric mean SD of P2 determinations except where indicated.
Data from n = 1 determination.
LipE = ꢁlog (EC50) – logD.
d

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K. J. Filipski et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4571–4578
Table 3
Properties of glucokinase activators 30, 42–44
N
O
N
H
O
O
R
a
b
R
EC50
(
lM)
aa
ba
MW
logD
LipE
3.52
Permeability
(10ꢁ6 cm/s)
Solubility
M)
HLM Clint
(mL/min/kg)
RLM Clint
(mL/min/kg)
(
l
H
N
42
43
30
44
1.4 0.5
0.23 0.08
0.85 0.04
0.50 0.11
0.09 0.03
1.12 0.07
415
412
395
395
2.63
1.54
0.97
1.34
15
13
7.1
16
117
558
332
373
<8.0
8.3
112
102
<25.4
47
S
O
O
N
0.12 0.02
0.12 0.01
0.12 0.01
0.79 0.02
0.86 0.01
0.76 0.04
5.40
5.32
5.26
N
F
O
O
O
N
<8.0
<8.0
N
N
N
N
N
a
Biochemical data reported as the geometric mean SD of P2 determinations.
LipE = ꢁlog (EC50) – logD.
b
Table 4
Properties of glucokinase activators 45–50a
N
O
R
N
H
O
N
O
N
N
O
ab
bb
MW
logD
LipE
Permeability
(10ꢁ6 cm/s)
Solubility
HLM Clint
(mL/min/kg)
RLM Clint
(mL/min/kg)
b
d
R
EC50
(lM)
(
lM)
45
46
47
0.23 0.03
0.44 0.16
1.1 0.2
0.13 0.01
0.13 0.02
0.13 0.01
0.84 0.01
0.95 0.07
0.78 0.02
423
421
411
1.91
1.74
5.04
4.92
6.27
17
469
398
339
22.4
<8.0
<8.0
91
14
106
26
HO
ꢁ0.02
0.43
ND
0.81
(S)
O
48
49
1.0 0.1
7.5 0.1
0.14 0.01
0.18 0.01
0.76 0.01
0.88 0.01
425
423
5.85
—
ND
ND
342
ND
<8.0
ND
38
(S)
ND
O
O
50
3.8c
0.19c
1.00c
423
ND
—
ND
ND
ND
ND
N
a
b
c
ND = Not Determined.
Biochemical data reported as the geometric mean SD of P2 determinations except where indicated.
Data from n = 1 determination.
LipE = ꢁlog (EC50) – logD.
d

K. J. Filipski et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4571–4578
4577
Table 5
Properties of glucokinase activators 36, 51–54a
R3
N
O
R1
N
H
O
O
R2
R1
R2
R3
EC50
M)
ab
bb
MW logD LipE
Permeability
(10ꢁ6 cm/s)
Solubility
(lM)
HLM Clint RLM Clint
(mL/min/ (mL/min/
b
c
(
l
kg)
kg)
N
51
Me 0.17 0.01 0.15 0.01 0.59 0.03 409
1.48
5.59
11
218
<8.0
<25.4
N
N
N
N
O
N
N
O
52
53
54
36
H
0.20 0.07 0.15 0.01 0.68 0.01 425
0.81
2.26
2.01
1.42
6.19
5.11
5.26
5.71
2.2
14
728
197
104
390
<8.0
12
<25.4
ND
(S)
O
S
HO
HO
HO
Me 0.09 0.01 0.09 0.01 0.80 0.01 459
Me 0.11 0.05 0.09 0.01 0.88 0.02 445
(S)
(S)
(S)
O
O
H
N
1.6
2.8
<8.0
<8.0
<25.4
<25.4
S
O
O
H
0.15 0.07 0.09 0.01 1.05 0.05 430
S
O
O
a
b
c
ND = Not Determined.
Biochemical data reported as the geometric mean SD of P2 determinations.
LipE = ꢁlog (EC50) – logD.
Table 6
Pharmacokinetic profiles of glucokinase activators 25, 26, 36, 47a
Clb (mL/min/kg)
Vdss (L/kg)
t1/2 (h)
Cmax (ng/mL)
AUCc (ng h/mL)
F (%)
b
b
c
25
26
45
36
61
13
44
19
6.41
0.746
5.79
1.5
5.3
6.0
1.8
150
31
412
74
703
141
580
253
29
2
32
6
0.746
a
b
c
Wistar-Han rats with n = 3 animals/group.
iv administration dosed at 1 mg/kg.
p.o. administration dosed at 5 mg/kg.
pyrazinyl (44) heterocycles. The pyrimidyl dimethyl-carboxamide
was chosen as an efficient moiety for exploration of alternative
O-alkyl substituents (Table 4). Although some improvement in po-
tency was observed with large alkyl substituents (45 and 46), over-
all lipophilic efficiency went down. LipE was improved, however,
with propanol 47 and propylether 48, albeit at the low lipophilicity
range, where oral absorption could potentially be negatively
impacted.20 Other polar moieties such as ether 49 and lactam 50
lost activity.
Table 5 shows several compounds with good potency that com-
bine some of the results from the above work. These possess calcu-
lated logD values that would suggest favorable physicochemical
properties and contain moieties that had previously demonstrated
good activity. Despite having excellent potency and good perme-
ability, pyrimidine 51 and pyrazine 52 have low b values, indicat-
ing potential inhibition of enzymatic activity under high glucose
conditions; an unfavorable profile. Propanols 36, 53, and 54 in-
creased b closer to desired levels around 1. The dimethyl sulfon-
amide, 53, showed some HLM turnover, while the methyl
sulfonamide, 54, suffered from low permeability. Ethyl sulfone 36
provided an improved yet still modest permeability value.
Several compounds with ideal activation profiles were chosen
for in vivo rat pharmacokinetic (PK) characterization (Table 6). As
a summary, compounds 25 and 45, which were less potent gluco-
kinase activators, had acceptable PK characteristics with higher
plasma exposures and near 30% oral bioavailability, while the more
potent compounds 26 and 36 showed very poor oral bioavailabili-
ties of 2% and 6%, respectively. The poor bioavailability for 36 is
likely a result of its poor permeability due to an additional H-bond
donor, while that for 26 may be due to poor solubility and/or high
rat oxidative clearance. The latter two compounds were also run in
an oral glucose tolerance test (OGTT) in vivo efficacy study in rats

4578
K. J. Filipski et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4571–4578
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and neither demonstrated glucose lowering. Subsequent PK analy-
ses of these samples showed free drug levels below their in vitro
EC50’s, further confirming the insufficient PK profiles for these
more potent analogs. This series showed both an HLM/RLM
in vitro disconnect and rat in vitro/in vivo clearance disconnect,
the origin of which remains unknown. This contributed to the dif-
ficulty of finding a compound with sufficient PK properties to show
an in vivo pharmacodynamic effect.
In summary, a substitution of the common heterocyclic amide
donor–acceptor motif present in many glucokinase activators for
a pyridone or pyrimidone moiety provided a structurally novel ser-
ies of partial activators with favorable activation profiles. This
change resulted in a better lipophilic efficiency compared to the
heterocyclic amides. Although an acceptable balance of potency
and PK was not achieved through optimization of this series to pro-
vide oral efficacy in a rat model, it is envisioned that this structural
change may benefit other glucokinase activator series, or more
broadly in other programs where a similar donor–acceptor motif
is required.
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