Discovery of trans-3,4′-bispyridinylethylenes as potent and novel inhibitors of protein kinase B (PKB/Akt) for the treatment of cancer: Synthesis and biological evaluation

Article abstract of DOI:10.1016/j.bmcl.2005.12.017

A novel series of Akt/PKB inhibitors derived from a screening lead (1) has been prepared. The novel trans-3,4′-bispyridinylethylenes described herein are potent inhibitors of Akt/PKB with IC₅₀ values in the low double-digit nanomolar range against Akt1. Compound 2q shows excellent selectivity against distinct families of kinases such as tyrosine kinases and CAMK, and displays poor to modest selectivity against closely related kinases in the AGC and CMGC families. The cellular activities including inhibition of cell growth and phosphorylation of downstream target GSK3 are also described. The X-ray structure of compound 2q complexed with PKA in the ATP binding site was determined.

Full text of DOI:10.1016/j.bmcl.2005.12.017

Bioorganic & Medicinal Chemistry Letters 16 (2006) 1679–1685
Discovery of trans-3,40-bispyridinylethylenes as potent and
novel inhibitors of protein kinase B (PKB/Akt) for the treatment
of cancer: Synthesis and biological evaluation
Qun Li,a,* Tongmei Li,a Gui-Dong Zhu,a Jianchun Gong,a Akiyo Claibone,a
Chris Dalton,a Yan Luo,a Eric F. Johnson,a Yan Shi,a Xuesong Liu,a Vered Klinghofer,a
Joy L. Bauch,a Kennan C. Marsh,a Jennifer J. Bouska,a Shannon Arries,a Ron De Jong,b
Tilman Oltersdorf,b Vincent S. Stoll,a Clarissa G. Jakob,a Saul H. Rosenberga and
Vincent L. Girandaa
aCancer Research, GPRD, Abbott Laboratories, Abbott Park, IL 60064-6101, USA
bIdun Pharmaceuticals, 9380 Judicial Dr., San Diego, CA 92121, USA
Received 10 November 2005; revised 1 December 2005; accepted 2 December 2005
Available online 5 January 2006
Abstract—A novel series of Akt/PKB inhibitors derived from a screening lead (1) has been prepared. The novel trans-3,40-bispyrid-
inylethylenes described herein are potent inhibitors of Akt/PKB with IC50 values in the low double-digit nanomolar range against
Akt1. Compound 2q shows excellent selectivity against distinct families of kinases such as tyrosine kinases and CAMK, and displays
poor to modest selectivity against closely related kinases in the AGC and CMGC families. The cellular activities including inhibition
of cell growth and phosphorylation of downstream target GSK3 are also described. The X-ray structure of compound 2q complexed
with PKA in the ATP binding site was determined.
Ó 2005 Elsevier Ltd. All rights reserved.
Akt inhibitors1 have recently generated much attention
as anticancer agents because of their role of intervention
in a signal transduction pathway crucial for prolifera-
tion and survival of cancer cells.2 Akt, also known as
protein kinase B (PKB), is a serine/threonine kinase that
belongs to the AGC family of kinases.3 There exist three
human isoforms of Akt: Akt1, Akt2, and Akt3. These
isoforms have a high degree of overall homology being
about 80% identical. They share similar downstream
targets, but differ in levels of expression and activation
in response to stimuli in various tumors.2e
recruits Akt from the cytoplasm to the membrane by
binding to the PH domain of Akt. This binding induces
conformational changes in Akt, exposing its main phos-
phorylation sites and bringing it in proximity with
PDK1 thereby enabling phosphorylation at Thr308 by
PDK1. The additional phosphorylation at Ser473 of
the C-terminus is carried out by putative PDK2. This
is thought to stabilize the active conformation of the
kinase domain, leading to fully activated Akt that
dissociates from the membrane. It then enters the
cytoplasm and nucleus where its substrates are located.
So far about 20 Akt substrates have been identified.2e
Akt is one of the major direct downstream targets of
class I PI3K. When activated in response to extracellu-
lar stimulation, PI3K phosphorylates glycerophospho-
lipid PtdIns(4,5)P2, leading to rapid production of
PtdIns(3,4,5)P3 in the cell membrane, which in turn
Compelling evidence supports the importance of Akt in
inducing tumorigenicity both in vitro and in vivo.2 Akt
is overexpressed and constitutively active in a large
number of human tumors. Akt antisense oligonucleo-
tides were found to inhibit proliferation and induce
apoptosis in several cancer cell lines. A recent study
has shown that inhibition of Akt via antisense RNA
reduced Akt expression in pancreatic tumorigenicity
and invasiveness in nude mice.4
Keywords: Akt inhibitors; Akt; PKB; Protein kinase B; GSK3; FL5.12-
Akt1; Anticancer; Apoptosis; X-ray.
*
Corresponding author. Tel.: +1 847 937 7125; fax: +1 847 936
1550; e-mail: qun.li@abbott.com
0960-894X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.12.017

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Q. Li et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1679–1685
Compound 1 was identified as a promising Akt inhibitor
lead from our compound library. It is an ATP compet-
itive inhibitor with an IC50 of 5.29 lM against Akt1. We
report herein the structure refinements of 1 that pro-
duced a novel and potent series of trans-3,40-bispyridi-
nylethylenes as Akt inhibitors represented by 2q (Fig. 1).
Cl
N
OHC
BOCNH
NH
13
N
NH2
15
NH
d, e
c
Cl
N
Synthesis of the trans-ethylene analogs of our lead (2, 5,
6, 7, and 10) is illustrated in Scheme 1. Mitsunobu reac-
tion of hydroxybromide 3 with the corresponding alco-
hol provided ether 4, which in turn was converted to
alkenes 2, 5, or 6 by the Heck reaction followed by
deprotection of the Boc group with TFA. Acetyloxy-
de-diazonization of 2q followed by hydrolysis produced
hydroxyl analog 7a. The 2-substituted pyridine analogs
(10) were prepared from 2-fluoro-4-vinylpyridine 9 using
the Heck reaction–alkylation sequence followed by Boc
deprotection.
I
12
BOCNH
NH
14
N
X
N
a, b
X=Cl
NH
X
N
a, f or g, e
W
R
Br
NH2
N
NH2
16, W=2H; 17, W=O
11
Scheme 2. Reagents and conditions: (a) 4-vinylpyridine, Pd2(dba)3,
P(o-Tol)3, Et3N, DMF, 100 °C, 15 h, 36–84%; (b) NaNO2, 30%
H2SO4, 0 °C, 5 h, then NaI, 2 h, 70%; (c) Ph3PCH3Br, n-BuLi, THF,
0 °C, 30 min, then 13, 2 h, 18%; (d) 14, 9-BBN, 0 °C to rt, overnight,
then 12, PdCl2(dppf), Cs2CO3, DMF, 50 °C, 8 h, 40%; (e) TFA,
CH2Cl2, rt, 2 h, 74–100%; (f) 9, AcOH, MeOH, reflux, 3 h, then
NaBH3CN, 1 h, 35–70%; (g) a-Boc-amino acid, EDC/HOBt/DMAP,
THF, overnight, 41–55%.
Preparation of analogs with the side chains attached to
the central pyridine through carbon (15) or nitrogen
(16 and 17) is shown in Scheme 2. 3-Amino-5-bromo-
pyridine 11 underwent the Heck reaction with 4-vinyl-
pyridine, followed by the iodo-de-diazonization
Cl
N
N
resulting in iodopyridine 12. The latter was reacted with
ethylene 14 in the presence of 9-BBN and PdCl2(dppf) to
give compound 15. Reductive amination of 11 with
N-Boc-tryptophanal by NaBH3CN in the presence of
Ti(i-PrO)4 and subsequent acidic deprotection of the
Boc group provided benzylamine 16. Aminopyridine
11 was converted to amides 17 through EDC coupling
reactions with Boc-protected amino acids followed by
deprotection with TFA.
3
O
O
4'
N
NH2
1
2q
N
NH2
NH
Figure 1. Modifications of a high throughput lead (1) resulted in
potent Akt inhibitor 2.
N
Compounds 22a and b, in which an aryl side chain is
attached to the b-position of the primary amine, were
synthesized as shown in Scheme 3. Nucleophilic substi-
tution of 3,5-dibromopyridine with the acetonitrile
anions yielded 19, which after reduction to amine 20
with borane followed by Boc protection afforded 21.
Heck reaction and subsequent acidic deprotection as
described previously provided 22.
O
N
X
NH
7a: X=OH; 7b: X=H
g
X=H
X1
(from 2q)
a
X=H
A1
X1
Br
A1
X1
Br
A1
A2
A2
b, c
a
A2
O
A3
O
OH
A3
A3
R
Our initial optimization efforts focused on modifications
of the amino acid-derived side chain of lead compound 1
R
Ar
4
2, 5, 6
3
NH2
NHBoc
N
N
N
N
e, f, c
a
b
R
F
F
O
R
d
Br
Br
Br
Br
R1
N
CN
N
N
R
18
19
NH2
20
c
NH2
10
9
8
N
N
Scheme 1. Reagents and conditions: (a) Substituted 2-Boc-aminoeth-
anol, DEAD/PPh3, THF, rt, 50–90%; (b) ArCH@CH2, P(o-Tol)3,
Pd(OAc)2, CH3CN, 80 °C, 8 h, 40–73%; (c) TFA, CH2Cl2, rt, 2 h; (d)
i—LDA, THF, ꢀ78 °C, 30 min, I2, 30 min, 88%; ii—LDA, THF,
ꢀ78 °C, 30 min, 81%;5 iii—SnBu3@CH2, Pd2Cl2(PPh3)2, dioxane,
80 °C, overnight, 38%; (e) P(o-Tol)3, Pd(Ac)2, CH3CN, 80 °C, 8 h,
84%; (f) NaOMe, MeOH, reflux, 8 h, 75%, or PhOH or RSH, KOH,
140 °C, 5–60%, or RNH2, DMF, 125 °C, 1.5–36 h, 3–60%; (g) i—
NaNO2, AcOH, rt, 18 h, 12%; ii—LiOH, water/THF, 55 °C, overnight,
57%.
R
d, e
R
Br
NH2
22
N
21
NHBOC
Scheme 3. Reagents and conditions: (a) RCH2CN, NaH, DMF, rt,
2 h, 33–99%; (b) BH3ÆTHF, THF, rt, overnight, 73–84%; (c) (BOC)2O,
CH3CN, rt, overnight, 78–98%; (d) 4-vinylpyridine, P(o-Tol)3,
Pd(Ac)2, CH3CN, 80 °C, 8 h; (e) TFA, CH2Cl2, rt, 2 h, 23–27% for
two steps.

Q. Li et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1679–1685
1681
Table 1. Activity of Akt inhibitorsa
Table 1 (continued)
a
Akt1 IC50 (nM)
R1
N
R2
O
Compound
R1
R2
H
R3
2s
Cl
23
N
R3
NH2
NH
Compound R1 R2 R3
a
Akt1 IC50 (nM)
2t
H
H
H
H
H
Cl
H
H
H
H
273
500
NH2
NH2
NH
N
1 (lead)
2a
Cl
H
H
H
H
H
5290
5080
NH2
NH2
2u
2v
7a
7b
Me
2b
14,710
1100
NH2
Me2N
NH
NH
NH
2c
H
H
19,320
24,010
>50,000
NH2
OH
CO2H
NH2
2d
2e
2f
H
H
H
H
H
H
H
H
11%b
10,870
23,910
690
a Against Akt1 with ATP concentration of 10 lM.
b Inhibition at 5.33 lM.
HN
HN
with other available amino acids (Table 1).6 Although
compounds with side chains derivatized from b-alanine
(2b), valine (2c), R-serine (2d), azetidine-2-carboxylic
acid (2e), and proline (2f) are much less active, phenylal-
anine analog 2g has an IC50 of 690 nM, which is approx-
imately 8-fold more potent than lead compound 1. This
result prompted us to further investigate this region of
the molecule. Addition of a second phenyl group to 2g
(2h) or moving the phenyl ring away from the amino
group (2i and k) is detrimental to the activity. On the other
hand, substitution on the phenyl ring (2l and m) has little
effect on the Akt1 activity, suggesting bicyclic aromatic
rings might be tolerable. Indeed, the naphthyl analogs
(2n and o) are 2- to 5-fold more potent than 2g, with the
2-naphthyl compound (2o) being 2-fold more active than
the 1-naphthyl analog (2n). Throughout our studies, we
have found that an aromatic group in the side chain is nec-
essary for potent Akt1 activity, with the 3-indolyl group
being optimal in the current series. With an IC50 of
14 nM, indole compound 2q is nearly 380-fold more ac-
tive than the initial lead. Note that the activities of N-
methylindole (2u) and benzothiophene (2p) are sharply
lower than that of indole 2q. The chloro (1) and deschloro
compounds (2a) have similar IC50 values against Akt1,
suggesting that the 2-chloro is not required for potency.
Chloro analog 2t is only slightly less active than 2q.
2g
NH2
2h
H
H
6760
NH2
NH2
2i
2j
2k
2l
H
H
H
H
H
H
H
H
8020
4040
4%b
875
O
NH2
O
N
H
NH2
NH2
OH
CN
2m
2n
2o
2p
2q
2r
H
H
H
H
H
H
H
H
H
H
H
H
320
324
146
142
14
NH2
NH2
NH2
Other side-chain modifications are summarized in Table
2. Replacing the oxygen linker with a carbon atom (15)
resulted in a nearly 9-fold drop in activity, perhaps
caused by a conformational change of the side chain.
However, the nitrogen analogs (16a and 6c) demonstrate
a slightly better activity than the corresponding oxygen
analogs 2q and t. Note that reduction of the indole ring
decreased activity by 4-fold (16b). Activity of the amides
(17a–d) is markedly reduced, with tryptophan amide 17a
being the best (278 nM). Incorporation of a structure
motif of HT-89, a known Akt inhibitor with an IC50
of 2.5 lM,1d resulted in almost complete loss of Akt1
NH2
NH2
NH2
S
NH
NH
360

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Q. Li et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1679–1685
Table 2. Activity of Akt inhibitorsa
Ar1
A
X
R4
b
Akt1 IC50 (nM)
Compound
X
N
Ar1
A
R4
Cl
N
N
15
CH2
H2N
198
19
N
H
Cl
Cl
16a
N
NH
H2N
H2N
N
H
H
N
16b
16c
17a
N
N
N
NH
NH
NH
79
9.7
N
H
N
N
H2N
O
N
H
278
H2N
O
N
H
N
N
N
17b
17c
17d
N
N
N
NH
NH
NH
73%c
3200
668
NH
H2N
O
N
H2N
O
H2N
H
N
N
N
Br
2w
N
N
O
32,250
284
22a
Bond
NH2
N
N
22b
N
Bond
760
N
Me
NH2
H2N
5
CH
N
O
O
O
O
O
O
17%d
35%d
N
H
6a
6b
6c
6d
6e
H2N
H2N
H2N
N
H
N
N
16%d
N
H
N
23,270
29%e
N
N
N
H
N
N
H2N
H2N
N
43,010
a Unless otherwise specified, all compounds are S-enantiomers.
b Against Akt1 with ATP concentration of 10 lM.
c Inhibition at 0.99 lM.
d Inhibition at 5.33 lM.
e Inhibition at 50 lM.

Q. Li et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1679–1685
1683
activity (2w). Compounds in which the oxygen linker is
deleted (22a and b) display an unexpectedly good activ-
ity with IC50 values slightly better than those of the cor-
responding oxygen analogs (2g and u).
dine and the side chain is critical as the ortho- and para-
substituted pyridines (6b–e) are much less potent than
the corresponding meta-substituted pyridines (2g and q).
Adding substituents at C-2 of the terminal pyridine in an
attempt to pick up additional interactions with hinge re-
gion amino acid residues was unsuccessful (Table 3). In
general, activities of the alkoxy and thioalkoxy analogs
(10a–d) are sharply reduced. Based on X-ray crystallogra-
phy, introduction of an amino group at C-2 (10e) was
anticipated to generate an additional H-bond interaction
with the hinge carbonyl group of Glu121. However, an
unexpected 10-fold reduction of potency was observed.
Similarly, benzyl analog 10i, designed to interact with
the nearby Phe438 of Akt1 (Phe327 in PKA),7 displays
a similar potency loss relative to parent compound 10e.
Another salient feature of the current series is the pri-
mary amino group in the side chain. Any modification
of the primary amino group, including deletion (7b),
replacement with a hydroxy group (7a), and substitution
with methyl groups (2v), resulted in a significant loss of
activity. The chirality of the amino group also affects the
potency, with the S-isomer (2q) exhibiting 25-fold more
potency than the corresponding R-isomer (2r).
One of the most important requirements for ATP site
inhibitors of Akt is having a functional group that can
form hydrogen bonds with the ‘hinge’ region of the
ATP binding pocket. The terminal pyridine in 2q has
been confirmed by X-ray structural data as the hinge-
binding group.7,8 Replacing this pyridine moiety with
a phenyl group (5) abolishes activity (Table 2). Attempts
to replace the central pyridine have not been successful.
Significant loss in activity is seen for the compound with
the central pyridine substituted by a phenyl group (6a).
Additionally, the 1,3-relationship between the vinylpyri-
The X-ray structure of 2q in complex with PKA (a ki-
nase closely related to Akt9) in the active site was deter-
mined (Fig. 2).7,8 In the active site, the nitrogen of the
terminal pyridine binds to the hinge via a hydrogen
bond with the backbone NH of Val123. The pyridine
ring is sandwiched between the isopropyl group of
Leu173 underneath and the methyl group of Ala70
above, forming strong van der Waals interactions. The
Table 3. Activity of Akt inhibitorsa
N
X
N
O
NH2
NH
a
IC50 (nM)
a
Akt1 IC50 (nM)
Compound
X
Compound
X
10a
MeO–
2670
10f
MeNH–
176
163
69
O
10b
10c
10d
10e
6450
6350
3110
121
10g
10h
10i
10j
EtNH–
S
H
N
H
147
3340
S
N
N
H2N–
a Against Akt1 with ATP concentration of 10 lM.
Figure 2. Stereoview of X-ray structure of compound 2q in complex with PKA in the ATP binding site.

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Q. Li et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1679–1685
Table 4. Selectivity profile and cellular activity of Akt inhibitor 2q
(IC50a, nM)
Test
Name
2q
Staurosporine
Kinases
Akt1
Akt2
Akt3
PKA
ERK2
CK2
14
257
1.5
6.5
354
38
10
3.6
12,850
>50,000
16,000
>50,000b
>50,000b
>50,000b
>50,000b
370
3400
9.5
88b
58b
23b
1920b
Chk1
KDR
FLT4
C-KIT
SRC
Cellular activity
GSK3-Pc,11
FL5.12-Akt110
(MTT)d
10,000
3000
460
290
Figure 3. X-ray crystal structure7 of 2q in complex with PKA in the
active site with key interactions highlighted. The amino acids
highlighted in black are from PKA and red are from Akt1.
MiaPaCa-2
(MTT)d
12,000
370
a Unless otherwise specified, all compounds are S-enantiomers, ATP
concentration at 10 lM.
nitrogen of the central pyridine hydrogen bonds to the
amino group of Lys72, which in turn forms a salt bridge
with Glu91. The charged primary amine of the side
chain sits tightly in the Mg-binding loop, binding to
Asn171 and Asp184 via hydrogen bonds and ionic inter-
actions. The indole ring is packed underneath the gly-
b ATP concentration at 1.0 mM.
c EC50 against GSK3 phosphorylation in the Akt1 overexpressing cell
FL5.12-Akt1.
d IC50 against cell proliferation in MTT assays.
˚
low (66%), with as many as 13 different amino acids.
However, none of these residues is located in the critical
binding sites.2e These structural similarities make it
difficult to achieve selectivity among these kinases.6
cine-rich loop with an average distance of 3.5 A.
Interestingly, although there is no apparent interaction
between the NH of the indole and the loop, N-methyl
substitution (2u) is detrimental to the binding. The key
interactions with PKA are highlighted in Figure 3.
Compound 2q was evaluated for its antiproliferative
activity against FL5.12-Akt1 murine prolymphocytic
cells10 that overexpress Akt1 and MiaPaCa-2 human
pancreatic cancer cells. Compound 2q displays IC50
values of 3.0 and 12.0 lM against FL5.12-Akt1 and
MiaPaCa-2, respectively. Compound 2q also inhibits
the phosphorylation of the Akt downstream target
GSK311 in FL5.12-Akt1 cells with an EC50 of
10.0 lM. Apparently, staurosporine is more potent than
2q in these tests.
With the available X-ray structure, it becomes easy to
understand why substitutions at C-2 (Table 3) are detri-
mental. Deep inside the binding cavity, the distance be-
tween C-2 of 2q and the carbonyl group of Glu121 is
˚
merely 3.2 A, not enough for groups larger than hydro-
gen. If the C-2 hydrogen were capable of hydrogen
bonding, it might be a perfect fit. Another feature of
PKA and Akt is that the entrance to the ATP binding
pocket near the hinge region is partially blocked by res-
idues 315–327 (PKA) of the C-terminal domain.2e The
nearest distance from the pyridine to Phe327 is about
Pharmacokinetic (PK) properties of selected Akt inhib-
itors are summarized in Table 5. Overall, compounds
with an oxygen linker (2p,q, and s) show favorable oral
bioavailability. Compounds 2q and s, which differ only
by a chlorine atom, share similar PK profiles in four
different species with oral bioavailabilities ranging from
11% to 52%. In rat, 2p displays an oral bioavailability of
43%, which is 2-fold better than that of 2q, suggesting
that the indole in 2q is an unfavorable group for PK.
The compounds with either a carbon (15) or a nitrogen
linker (16a) demonstrate extremely high clearance in
mouse resulting in poor overall PK.
˚
3.6 A, making it just as hard even with the amino group
of 10e facing outside of the cavity by 180° rotation of the
pyridine.
Selectivity and cellular activity profiles of 2q in compar-
ison with those of staurosporine, a non-selective kinase
inhibitor staurosporine serving as a control, are summa-
rized in Table 4. Overall, 2q demonstrates excellent
selectivity against select families of kinases such as
TK3 and CAMK,3 and exhibits IC50 values of over
50 lM against most kinases. However, selectivity
against closely related kinases of the AGC3 and CMGC3
families is marginal at best, presumably due to the high
degree of homology in the ATP binding pocket. The
three Akt isoforms display greater than 80% overall se-
quence homology and nearly 100% homology in the
ATP binding pocket. In the ATP binding pocket, the
non-crucial Val228 in AKT3 is the only one that is dif-
ferent among the three Akt isoforms. The homology be-
tween Akt1 and PKA in the ATP binding domains is
In summary, a novel series of inhibitors of PKB/Akt
derived from a screening lead (1) has been prepared.
The novel series of 3,40-bispyridinylethylenes as repre-
sented by 2q are potent Akt inhibitors with IC50 values
in the low double-digit nanomolar rang against Akt1.
Compound 2q shows excellent selectivity against distinct
families of kinases such as TK and CAMK, and displays
poor to marginal selectivity against the AGC and

Q. Li et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1679–1685
Table 5. Pharmacokinetic properties of selected Akt inhibitors12
1685
Compound
Species
Rata
t1/2 (h)
Vb (L/kg)
Clp (L/h kg)
1.0
Cmax (lg/mL)
AUC (oral)
2.13
Oral F (%)
2p
2q
2.5
3.6
0.62
43
Mouseb
Rata
0.8
3.1
3.2
3.7
6.5
5.2
5.7
1.2
2.5
1.6
2.78
0.30
0.10
0.04
5.5
39
21
52
12
0.95
0.50
0.19
Dogc
12.8
9.1
Monkeyc
2s
Mouseb
Rata
0.8
3.1
5.4
3.0
4.8
9.9
4.1
2.2
1.4
0.97
0.94
0.06
0.12
0.06
1.45
0.38
1.01
0.30
11
17
45
12
Dogc
11.1
4.2
Monkeyc
15
Moused
Moused
0.2
0.6
4.9
9.5
17.3
11.4
0.09
<0.1
0
<10
0
16a
<0.02
a A single 5 mg/kg dose.
b A single 30 mg/kg dose.
c A single 2.5 mg/kg dose.
d A single 10 mg/kg dose.
CMGC families of kinases.3 Compound 2q also demon-
strates moderate antiproliferative activity against
FL5.12-Akt1 and MiaPaCa-2 cells. Inhibition of phos-
phorylation of the downstream target GSK3 is observed
for 2q. Moreover, the current series have respectable
oral bioavailabilities across four different animal species.
These encouraging preliminary results warrant further
efforts to optimize the physiochemical and biological
properties of this series.
ilieris, M. Curr. Cancer Drug Targets 2004, 4, 235; (c)
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Acknowledgments
6. Luo, Y.; Shoemaker, A.; Liu, X.; Woods, K.; Thomas, S.;
de Jong, R.; Han, E.; Li, T.; Stoll, S. S.; Powelas, J. A.;
Oleksijew, A.; Mitten, M. J.; Shi, Y.; Guan, R.; McGon-
igal, T. P.; Klinghofer, V.; Johnson, E. F.; Leverson, J. D.;
Bouska, J. J.; Mamo, M.; Smith, R. A.; Gramling-Evans,
E. E.; Zinker, B. A.; Mika, A. K.; Nguyen, P. T.;
Oltersdorf, T.; Rosenberg, S. H.; Li, Q.; Giranda, V. Mol.
Cancer Ther. 2005, 4, 977.
The authors are grateful to Mr. Rick Clark, Dr. Moshe
Weitzberg, Dr. Matt. Hensen, Dr. Robert Keyes, Dr.
Curt Cooper, and Dr. Chris Krueger for proofreading
and suggestions. X-ray crystallographic data were col-
lected at beamline 17-ID in the facilities of the Industri-
al Macromolecular Crystallography Association
Collaborative Access Team (IMCA-CAT) at the Ad-
vanced Photon Source, which are supported by the
companies of the Industrial Macromolecular Crystal-
lography Association.
7. PKA and 2q were co-crystallized in a solution containing
PKA (20 mg/mL) and PKI peptide according to a method
of Engh et al.8 The structure was determined and refined
˚
to
resolutions
of
1.9 A
(Rwork = 30.92%
and
RFree = 33.78%). The crystallographic data have been
deposited with PDB (ID: 2F7X).
8. Engh, R. A.; Girod, A.; Kinzel, V.; Huber, R.; Bosse-
meyer, D. J. Biol. Chem. 1996, 271, 26157.
References and notes
9. Hanada, M.; Feng, J.; Hemmings, B. A. Biochim. Biophys.
Acta 2004, 1697, 3.
1. (a) Zhao, Z.; Leister, W. H.; Robinson, R. G.; Barnett, S.
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2005, 5, 109; (b) Mitsiades, C. S.; Mitsiades, N.; Kouts-
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12. Pharmacokinetic properties were determined by tradi-
tional single-dose methods with plasma concentrations
determined by HPLC–MS as described previously: Li,
Q.; Woods, K. W.; Claiborne, A.; Gwaltney, S. L., II;
McCroskey, R. W.; Barr, K. J.; McCroskey, R. W.;
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