Optimization of allosteric MEK inhibitors. Part 1: Venturing into underexplored SAR territories

Article abstract of DOI:10.1016/j.bmcl.2013.02.028

Using PD325901 as a starting point for identifying novel allosteric MEK inhibitors with high cell potency and long-lasting target inhibition in vivo, truncation of its hydroxamic ester headgroup was combined with incorporation of alkyl and aryl ethers at the neighboring ring position. Whereas alkoxy side chains did not yield sufficient levels of cell potency, specifically substituted aryloxy groups allowed for high enzymatic and cellular potencies. Sulfamide 28 was identified as a highly potent MEK inhibitor with nanomolar cell potency against B-RAF (V600E) as well as Ras-mutated cell lines, high metabolic stability and resulting long half-lives. It was efficacious against B-RAF as well as K-Ras driven xenograft models and showed - despite being orally bioavailable and not a P-glycoprotein substrate - much lower brain/plasma exposure ratios than PD325901.

Full text of DOI:10.1016/j.bmcl.2013.02.028

Bioorganic & Medicinal Chemistry Letters 23 (2013) 2384–2390
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Optimization of allosteric MEK inhibitors. Part 1: Venturing
into underexplored SAR territories
a
b
c
b
Ingo V. Hartung a, , Marion Hitchcock , Florian Pühler , Roland Neuhaus , Arne Scholz ,
⇑
Stefanie Hammer b, Kirstin Petersen b, Gerhard Siemeister b, Dominic Brittain a, , Roman C. Hillig d
a Medicinal Chemistry, Bayer HealthCare AG, 13353 Berlin, Germany
b Therapeutic Research Group Oncology, Bayer HealthCare AG, 13353 Berlin, Germany
c Research Pharmacokinetics, Bayer HealthCare AG, 13353 Berlin, Germany
d Structural Biology, Bayer HealthCare AG, 13353 Berlin, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Using PD325901 as a starting point for identifying novel allosteric MEK inhibitors with high cell potency
and long-lasting target inhibition in vivo, truncation of its hydroxamic ester headgroup was combined
with incorporation of alkyl and aryl ethers at the neighboring ring position. Whereas alkoxy side chains
did not yield sufficient levels of cell potency, specifically substituted aryloxy groups allowed for high
enzymatic and cellular potencies. Sulfamide 28 was identified as a highly potent MEK inhibitor with
nanomolar cell potency against B-RAF (V600E) as well as Ras-mutated cell lines, high metabolic stability
and resulting long half-lives. It was efficacious against B-RAF as well as K-Ras driven xenograft models
and showed—despite being orally bioavailable and not a P-glycoprotein substrate—much lower brain/
plasma exposure ratios than PD325901.
Received 11 December 2012
Revised 1 February 2013
Accepted 7 February 2013
Available online 14 February 2013
Keywords:
Allosteric MEK inhibitor
Oncology
Structure-based drug design
Blood–brain barrier
Ó 2013 Elsevier Ltd. All rights reserved.
Co-targeting multiple nodes within one signaling axis (vertical
combinations) or co-targeting parallel (possibly interconnected)
signaling pathways (horizontal combinations) is becoming more
and more the mainstay for clinical research on improving antitu-
mor efficacy and on addressing acquired resistance to highly spe-
cific (‘targeted’) cancer therapeutics. The Ras–Raf–MEK–ERK
pathway is one of the most often deregulated pathways in human
cancers, with mutated oncogenic forms of Ras having being identi-
fied in up to 30% of human cancers and B-Raf mutations being
omnipresent in malignant melanomas.1 Inhibitors of the key sig-
naling node within this pathway, the mitogen activated protein
(MAP) kinase kinases MEK1/2 have been shown to be prime exper-
imental combination partners for other targeted cancer therapeu-
tics such as inhibitors of the PI3K-Akt-mTOR pathway (horizontal
combination) or inhibitors of Raf or ERK (vertical combination).2
Based on pioneering work by researchers at Pfizer, inhibition of
MEK1/2 by highly selective allosteric inhibitors has been pursued
by many pharmaceutical companies.3,4 However, the first
generation of advanced clinical MEK1/2 inhibitors, namely
PD325901 and AZD6244, did not yield convincing clinical efficacy.
In addition, PD325901 was burdened by ocular toxicity and likely
CNS-mediated adverse effects leading to its discontinuation.5
CNS-mediated adverse effects have not been reported for
AZD6244.6 Taking these clinical findings into account, a new gen-
eration of allosteric MEK inhibitors would have to maintain the
exquisite target selectivity of its predecessors while improving
their PK profile, more specifically by reducing brain penetration
and at the same time securing continuous target inhibition upon
once-daily oral dosing.7
Inhibitors from Pfizer’s PD series of 2-anilino-benzoic acids are
binding to an allosteric site not overlapping with the ATP binding
site which is more commonly targeted by kinase inhibitors. Based
on crystallization of MEK1/2 with a close analog of PD325901 key
enzyme–ligand interactions have been deduced8 and later-on con-
firmed by SAR findings (highlighted in Fig. 1).9 Subsequent medic-
inal chemistry efforts were largely focused on retaining, mimicking
or strengthening these interactions. However, up to 2008 literally
no efforts had been invested into introducing functionalized sub-
stituents to the 6-position of the benzoic acid core.10 To the con-
trary, it had been stated that substituents at the C6 position
would be detrimental for target potency.11
Taking the history of kinase inhibitor design into account, espe-
cially Gleevec with its DFG-out binding mode, one can hypothesize
that growing kinase inhibitors into previously unexplored binding
regions may lead to induced fit binding pocket adaptions which
may result in strikingly different pharmacological profiles. As the
hydroxamic acid linkage was one known metabolic liability of
PD-like MEK inhibitors, truncating this functionality while at the
same time introducing a functionalized alkoxy ether side chain at
⇑
Corresponding author. Address: Bayer HealthCare AG, Global Drug Discovery,
Müllerstraße 178, 13353 Berlin, Germany.
E-mail address: ingo.hartung@bayer.com (I.V. Hartung).
Pharma Strategy, Novartis Pharma AG, Bottmingen CH-4103, Switzerland.
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.02.028

I. V. Hartung et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2384–2390
2385
OH
OH
Lys97
H2N
O
F
O
N
H
N
6
R
O
F
H
N
Phe209
1
6
I
2
F
I
R
F
Val127
HO
O
F
*
1 R =
Ser212
HO
R = H
PD325901
R = Br PD318088
Figure 1. Key ligand–protein interactions for PD325901 (highlighted in green)—Rationale for introduction of side chains at C6 position.
the C6 position appeared to be a promising starting point for iden-
tifying novel allosteric MEK inhibitors.12
productive hydrogen bonding interaction aside from a tentatively
assigned interaction between the terminal hydroxyl group with
the side chain of Asp190 (3.5 Å).
Encouragingly, from a focused number of analogs initially syn-
thesized, hydroxyl-alkoxy ether 1 proved this rationale to be a via-
ble path forward. In this Letter we describe the characterization of
this new allosteric C6-alkoxy benzoic amide MEK inhibitor and our
subsequent optimization program leading to C6-aryloxy deriva-
tives with high enzymatic and cellular potency, exceptionally long
half-lives and convincing efficacy at low oral doses in mice xeno-
graft models driven by either B-Raf or K-Ras mutations.
Newly synthesized compounds were profiled in an enzymatic
COT-MEK-ERK1 cascade assay and optionally in cell proliferation
assays employing A375 cells, harboring a B-Raf (V600E) mutation,
and HCT116 cells, harboring a K-Ras G13D mutation.13,14 In line
with previous publications, A375 cells were found to be signifi-
cantly more sensitive to MEK inhibition than HCT116 cells.15
Our lead MEK inhibitor 1 was found to be a moderately potent
MEK inhibitor (Table 1). An enzymatic IC50 of 63 nM compared
well to AZD6244 (80 nM), whereas both compounds were signifi-
cantly less potent than PD325901 (7 nM) in this assay. In cell as-
Our initial goal for the first round of SAR work was to convert
the C6 ether side chain from a bystander group as in 1 (with a
potentially beneficial impact on physicochemical and PK proper-
ties) to a group driving target potency. Therefore refraining from
re-introducing the hydroxamic ester moiety, we focused instead
on optimizing the C6 ether side chain. Selected and most instruc-
tive analogs from this endeavor are compiled in Table 1. Simplify-
ing the C6 ether side chain to a methoxy group (2) further reduced
cell potency, whereas inverting the stereocenter (3) or moving it to
a different position (4) was of only minor impact. Increasing lipo-
philicity by methylation gave rise to tertiary alcohol 6 with an
IC50 of 40 nM in the A375 proliferation assay. However, in the less
sensitive K-Ras driven HCT116 proliferation assay still lM concen-
trations were required. Replacing the terminal hydroxyl group by
various amines (e.g., –NH2, –NH-Et, morpholine, N-Me-piperazine)
was accepted on the enzymatic level but less favorable with re-
spect to cellular potency (data not shown). Introduction of small
heterocycles as capping moieties (e.g., pyrazole 7 and imidazole
8) similarly improved enzymatic potency but did not translate well
into cell potency.
says, 1 showed inhibition of A375 proliferation with a sub-
IC50, but M concentrations were required to effect inhibition of
proliferation of the K-Ras mutated cell line HCT116.
lM
l
Our lead 1 showed low-to-moderate clearance in rats, a half-life
of 2.4 h and 70% bioavailability (Table 4). Of concern to us, 1 signif-
icantly crossed the blood–brain barrier in mice, even exceeding the
brain/plasma exposure ratio obtained with PD325901 under simi-
lar conditions. Hence, though being a valuable starting point, the
profile of 1 required significant further optimization with the need
to increase enzymatic and cell potency and to reduce brain
penetration.
A co-crystal structure of 1 with MEK1 was solved in order to
guide our potency optimization efforts (Protein Data Bank acces-
sion code 4ark). As can be deduced from Figure 2, almost all the
canonical core interactions with the MEK enzyme were preserved:
Compound 1 binds in a deep hydrophobic pocket and forms
numerous van der Waals contacts with Met143, Leu118, Ile141
and a T stacking interaction with Phe209. However, Lys97 which
binds to the hydroxyl and carbonyl group of the hydroxamic ester
in PD-type compounds is not engaged in any interactions with
compound 1. These missing interactions may explain the drop in
potency between 1 and PD325901 (in addition to an unknown im-
pact of the second fluorine atom at the PD325901 core). At the
same time, the newly introduced C6 side chain did not show
Imidazole 8—with in vitro and cell potency comparable to
AZD6244 but inferior to PD325901—showed an interesting PK pro-
file (Table 4). Clearance was low in rats, and volume of distribution
high (reflecting the basicity of the imidazole ring) resulting in a
long terminal half-life. Bioavailability in rats was low (29%), signif-
icantly below what would be expected based on the observed low
in vivo clearance. Since we measured significant efflux in the Caco2
permeability assay (ꢀ10-fold efflux for 8 compared to ꢀthreefold
influx for 1), absorption into the circulation is likely limited by ac-
tive efflux. Compound 8 was shown to be a P-glycoprotein (Pgp)
substrate in vitro. Accordingly, brain penetration of 8 in mice
was also significantly attenuated compared to 1. In conclusion,
by replacing the terminal hydroxyl group in 1 by an imidazole
group our goal of significantly reducing brain exposure was
reached. However, we felt the potency of imidazole 8 to be insuf-
ficient and the overall PK profile to be unfavorable for an oral drug.
Reducing the degree of side-chain flexibility in order to improve
potency was subsequently pursued by introducing various hetero-
cycloalkyl groups into the C6 side-chain. One exemplary series (out
of a structurally diverse set of cyclic side-chains pursued) is shown
in Table 2. Unsubstituted prolinol (9) gave similar enzymatic and

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I. V. Hartung et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2384–2390
Table 1
SAR of C6-alkoxy substituents (according to Fig. 1)
H2N
O
F
H
N
*
I
F
a
Compound
Side chain
In vitro IC50 (nM)
MEK1b
A375 (B-Raf)
HCT116 (K-Ras)
PD325901
AZD6244
7
80
13
31
194
3100
HO
HO
O
*
1
2
3
63
74
96
148
354
240
3400
O
–
–
*
HO
HO
O
O
*
*
OH
4
63
350
–
HO
HO
O
O
*
*
5
6
69
43
240
40
–
HO
HO
2450
HO
HO
N
O
*
*
7
8
13
16
151
98
2070
1250
N
HO
O
N
N
See text and footnote 13 for assay details.
Lower detection limit of this assay: IC50 of ꢀ5–15 nM.
a
b
cell potency as our initial side-chain lead 1. Capping of the side-
chain nitrogen did not improve but, to the contrary, in most cases
deteriorated potency with the exception of sulfamide 13.
systematically assessing substituents on the phenoxy side-chain
(exemplary analogs 18–21) several inhibitors with low nanomolar
enzymatic and A375 cell potency were identified, but the
lM
Having so far not been able to reach sub-
l
M IC50 values in the
threshold in the HCT116 assay was still not conquered. A break-
through was accomplished with the striking finding that—despite
the methyl sulfonamide analog 22 being not more potent than
comparable amide analogs—its higher homolog 23 did show a
HCT116 proliferation assay we switched our focus to even less flex-
ible (hetero)-aromatic C6 side-chains (Table 3). Researchers from
Japan Tobacco had described their MEK inhibitor JTP-70902 in late
2007 which featured an additional aromatic side-chain (albeit in
combination with a significantly different scaffold and a less flexi-
ble anchor point; see Figure 3).16 Interestingly, JTP-70902 resulted
from a screen searching for inducers of p15INK4b, a downstream
effector of the Ras–Raf–MEK–ERK pathway. JTP-70902 is thereby
the only allosteric MEK inhibitor not resulting from a structure-
based program employing PD-like inhibitors as starting point.
Phenoxy-substituted analog 14 was found to be less potent than
our initial lead 1, whereas a meta-pyridoxy side-chain restored po-
tency to the previously reached level. Introducing a meta-acetam-
ido phenyl side-chain did not lead to the needed potency boost. By
sub-lM IC50 in the HCT116 proliferation assay. Surrounding SAR
exploration gave rise to sulfamide 25 which was our most potent
analog so far (IC50 of 155 nM in the HCT116 proliferation assay)
and was therefore profiled in more detail.
Sulfamide 25 showed a moderate blood clearance in rats of
2.1 L/h/kg (1 mg/kg iv dose) with a half-life of 2.2 h and a moderate
bioavailability of 55%. Compound 25 was found to be highly effica-
cious in vivo in a LOX carcinoma mice model employing doses of 1
and 2.5 mg/kg po once-daily (data not shown). In incubations with
liver microsomes and hepatocytes, demethylation of the sulfamide
moiety was identified as the only metabolic pathway of 25.

I. V. Hartung et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2384–2390
2387
Analogous synthetic routes were used for all derivatives con-
taining aromatic ether side chains. In the earlier part of the pro-
ject—especially for the synthesis of compounds with alkyl ether
side chains (Table 1)—2,4,6-trifluorobenzonitrile was used as start-
ing material necessitating an additional step for a final H2O2-pro-
moted nitrile-to-amide transformation. In contrast to 2,4,6-
trifluorobenzamide, base-promoted SNAr to 2,4,6-tri-fluorobenzo-
nitrile were less regioselective and required tedious separation of
ortho- and para-regioisomers. Hydroxyl groups in alkyl side chains
were suitably protected, for example as an acetonide in case of vic-
inal diols.
Gratifyingly, demethylated analogs 27 and 28 were found to be
at least as potent as the dimethylated parent compound 25. The
unsubstituted sulfamide 28 inhibited A375 proliferation with a
low nanomolar IC50 and was as potent as PD325901 in the
HCT116 proliferation assay. Sulfamide 28 was found to be up to
10-fold more potent than AZD6244 in the latter assay as well as
in other proliferation assays with non-B-Raf driven cell lines. For
example, compound 28 inhibited proliferation of A549 cells with
an IC50 value of 132 nM (PD325901 166 nM, AZD6244 1750 nM),
LOVO cells with an IC50 value of 175 nM (PD325901 128 nM,
AZD6244 2830 nM) and MIA PaCa-2 cells with an IC50 value of
23 nM (PD325901 17 nM, AZD6244 142 nM), respectively.
MEK inhibitor 28 showed low clearance in all investigated spe-
cies (rat, mouse, dog; see Table 4 for rat data) with long half-lives
(32 h in rat, 34 h in mice and 110 h in dogs) and moderate-to-high
bioavailabilities. In summary, metabolism-inspired removal of two
methyl groups—a strategy which may be coined pre-metaboliza-
tion—improved metabolic stability while target potency was re-
tained. Although not a focus of our optimization strategy at that
time, switching to the unsubstituted sulfamide motif also in-
creased the lipophilicity efficiency (decrease of clogP by 0.8 units).
This very promising in vitro pharmacological and in vivo PK
profile translated well into high in vivo efficacy in various xeno-
graft models. For example, a daily dose of 1 mg/kg po was suffi-
cient for complete tumor growth inhibition in an A549 (K-Ras
mutated NSCLC) xenograft study in nude mice (Fig. 4). 1 mg/kg
of sulfamide 28 (dosed once-daily) was statistically significantly
more efficacious than 3 mg/kg PD325901 (once-daily). Due to its
long half-life, intermittent dosing schemes (for example 1 mg/kg
dosed every second day) were as efficacious in the A549 xenograft
setting as daily dosing schemes.
Figure 2. Co-crystal-structure of compound 1 (carbon atoms in yellow) and ADP
(cyan) bound to MEK1. For comparison, MEK1 in complex with PD318088 (PDB
1s9j) was superimposed (ligand carbon atoms in green). Figure generated using the
Pymol software.
Table 2
SAR of prolinol-containing C6-ether side-chains
H2N
O
F
H
N
O
*
I
N
F
Compound
Side chain
In vitro IC50 (nM)
MEK1
26
A375 (B-Raf)
HCT116 (K-Ras)
H
*
H3C
*
9
124
3030
–
10
182
973
O
S
11
96
323
–
Most notably, sulfamide 28 showed an exceptionally low brain/
plasma exposure ratio after iv dosing to mice (Table 4). Low brain
penetration potential was confirmed by comparing pERK inhibition
by Western blotting of A549 tumor tissue with brain lysates at the
highly efficacious dose of 2 mg/kg po (data not shown). Whereas
ERK phosphorylation in tumor tissue was almost completely
blocked 6 h after dosing, no change in pERK1/2 was observed in
brain lysates.
*
O
N
O
12
13
1000
73
1120
172
–
S
*
O
NH2
O
S
3040
*
O
Having constantly profiled analogs from our series for its brain
penetration behavior in mice, we tried to rationalize our findings
by correlating brain/plasma exposure ratios qualitatively to TPSA
values (as a measure for polarity-driven permeability limitations)
and Pgp recognition (as one well known mechanism for preventing
brain penetration by active efflux).17 We did not find any hint for
Pgp-mediated efflux for sulfamide 28 or for close analogs with sim-
ilarly limited brain/plasma exposure ratios. For example, sulfamide
28 retained its high pERK inhibitory potency in the Pgp-expressing
cancer cell line HeLa-MaTu-ADR whereas AZD6244 experienced a
dramatic decrease of pERK inhibitory potency in this cell line. Of
note, we found that analogs from our series with a TPSA of 130–
140 Å2 possess low brain penetration potential in mice while
retaining sufficient bioavailability after oral dosing.
Inspired by this metabolic profiling result and being aware that
metabolites in certain cases possess superior PK and physicochem-
ical properties than their parent compounds, we synthesized the
mono-methylated sulfamide 27 and its unsubstituted congener
28. The synthesis of sulfamide 28 is summarized in Scheme 1.
Sulfamide 28 is easily accessible in only three steps from 2,4,6-
trifluorobenzamide by base-mediated (amide directed) introduc-
tion of both ortho substituents. It is noteworthy that the C6-
meta-aminophenoxy side-chain was introduced without necessi-
tating an amino protection group thereby allowing for direct intro-
duction of the sulfamide capping group in the subsequent and final
step. Beneficially, this synthetic route is also easily applicable for
screening diverse capping groups.
It is noteworthy that crystals of MEK1 incubated with C6-ary-
loxy-substituted compounds could be grown but never diffracted

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I. V. Hartung et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2384–2390
Table 3
SAR of C6-aryloxy substituents
H2N
O
F
H
N
*
I
F
Compound
Side chain
In vitro IC50 (nM)
A375 (B-Raf)
MEK1
99
HCT116 (K-Ras)
–
O
O
*
14
15
408
141
*
76
54
4180
N
O
*
16
221
–
NH
N
H
N
O
O
17
18
28
50
2290
*
*
O
O
539
808
–
N
H
H
N
O
O
19
20
48
192
8810
*
*
O
O
H
N
106
1310
H
O
N
*
*
21
22
36
21
35
23
4510
3800
O
O
H
N
O
O
S
S
O
O
O
H
N
23
24
25
15
18
21
<30
17
287
459
155
*
O
H
N
O
S
*
*
O
O
H
N
N
O
18
S
O
O
H
N
N
O
26
21
28
412
S
*
O
O

I. V. Hartung et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2384–2390
2389
Table 3 (continued)
Compound
Side chain
In vitro IC50 (nM)
MEK1
22
A375 (B-Raf)
HCT116 (K-Ras)
103
H
N
S
O
H
N
O
27
16
*
O
H
N
H2N
O
O
S
S
28
29
14
4
180
*
*
O
O
H2N
32
37
3490
O
O
to better than 6 Å and were therefore not suitable for structure
determination. The hydroxyl alkoxy side chain of 1 (Fig. 2) contacts
the activation segment of MEK1 which in this crystal form contrib-
utes to a crystal contact with the corresponding activation loop of a
crystal neighbor. Larger substituents in this area may thus have
weakened this crystal contact which may have triggered the ob-
served loss in diffraction power.
In conclusion, we have successfully established a novel series of
allosteric MEK inhibitors by exploring previously unchartered SAR
territories. We have identified sulfamide 28 as a highly potent
O
O
N
O
F
S
HN
O
H
N
N
N
Br
O
Figure 3. Structure of JTP-70902.
H2N
F
O
H2N
F
O
F
F
H
N
F
(b)
H2N
(a)
+
H2N
O
OH
I
I
F
F
O
H2N
O
H2N
H2N
F
S O
HN
F
H
H
H2N
O
N
O
N
(c)
I
I
F
F
Scheme 1. Synthesis of sulfamide 28. Reagents and conditions: (a) LiHMDS, THF, 0 °C to rt, 22%; (b) Cs2CO3, DMF, 50 °C, 73%; (c) (i) ClSO2NCO, DMAc (cat.), CH2Cl2, HCO2H,
40 °C, (ii) aniline intermediate, DIPEA, DMAc, rt, 82%. Abbreviations: DIPEA = diisopropylethylamine; DMAc = dimethylacetamide; LiHMDS = lithium hexamethyldisilazide.
Efficacy in A549 xenografts
120
100
80
60
40
20
0
vehicle
Compound 28, 1.0 mg/kg qd
T/C = 0.28
Compound 28, 1.0 mg/kg q2d
T/C = 0.34
PD 325901, 3 mg/kg qd
T/C = 0.53
0
10
20
30
40
days after implantation
Figure 4. In vivo A549 xenograft study with sulfamide 28 and PD325901 in nude mice.

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I. V. Hartung et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2384–2390
Table 4
PK data of key compounds
Compound
Rat PKa
Mice PK
Clblood (L/kg/h)
Vss (L/kg)
t1/2 (h)
F (%)
Brain/plasma ratiob
PD325901
AZD6244
1
8
0.5
1.7
0.2
4.4
10.3
2.0
5.4
3.8
2.4
8.4
32
104
14–64
70
20–41
62
0.11
<0.02
0.73
0.04
<0.02
0.06
1.49
0.58
0.03
28
a
Dosing for PD325901: 0.5 mg/kg iv/1 mg/kg po; dosing for AZD6244: 0.5 mg/kg iv/5 mg/kg po; dosing for 1: 0.5 mg/kg iv/1 mg/kg po; dosing for 8: 0.3 mg/kg iv/0.6 mg/kg
po; dosing for 28: 1 mg/kg iv/1 mg/kg po.
b
AUC(brain)/AUC(plasma) for 0–3 h after 5 mg/kg iv dosing.
Marlow, A.; Litwiler, K.; Brown, S.; Poch, G.; Kane, K.; Haney, J.; Eckardt, S. G. J.
Clin. Oncol. 2008, 26, 2139.
7. In a recent publication, researchers of GSK described a similar reasoning: (a)
non-ATP competitive MEK inhibitor. With its ease of synthesis, its
state-of-the-art in vivo efficacy in various xenograft models and its
ability to continuously block ERK phosphorylation, sulfamide 28
was a significant milestone for our MEK inhibitor program. Further
data on this compound and a subsequent round of optimization
leading to a second generation of MEK inhibitors will be reported
in due course.
Gilmartin, A. G.; Bleam, M. R.; Groy, A.; Moss, K. G.; Minthorn, E. A.; Kulkami, S.
G.; Rominger, C. M.; Erskine, S.; Fisher, K. E.; Yang, J.; Zappacosta, F.; Annan, R.;
Sutton, D.; Laquerre, S. G. Clin. Cancer Res. 2011, 17, 989; See also: (b) Abe, H.;
Kikuchi, S.; Hayakawa, K.; Iida, T.; Nagahashi, N.; Maeda, K.; Sakamoto, J.;
Matsumoto, N.; Miura, T.; Matsumura, K.; Seki, N.; Inaba, T.; Kawasaki, H.;
Yamaguchi, T.; Kakefuda, R.; Nanayama, T.; Kurachi, H.; Hori, Y.; Yoshida, T.;
Kakegawa, J.; Watanabe, Y.; Gilmartin, A. G.; Richter, M. C.; Moss, K. G.;
Laquerre, S. G. ACS Med. Chem. Lett. 2011, 2, 320.
Acknowledgments
8. Ohren, J. F.; Chen, H.; Pavlovsky, A.; Whitehead, C.; Zhang, E.; Kuffa, P.; Yan, C.;
McConnell, P.; Spessard, C.; Banotai, C.; Mueller, W. T.; Delaney, A.; Omer, C.;
Sebolt-Leopold, J.; Dudley, D. T.; Leung, I. K.; Flamme, C.; Warmus, J.; Kaufman,
M.; Barrett, S.; Tecle, H.; Hasemann, C. A. Nat. Struct. Biol. 2004, 11, 1192.
9. Barrett, S. D.; Bridges, A. J.; Dudley, D. T.; Saltiel, A. R.; Fergus, J. H.; Flamme, C.
M.; Delaney, A. M.; Kaufman, M.; LePage, S.; Leopold, W. R.; Przybranowski, S.
A.; Sebolt-Leopold, J.; Van Becelaere, K.; Doherty, A. M.; Kennedy, R. M.;
Marston, D.; Howard, W. A., Jr.; Smith, Y.; Warmus, J. S.; Tecle, H. Bioorg. Med.
Chem. Lett. 2008, 18, 6501.
10. After completion of our investigations, C5-substituted allosteric MEK inhibitors
as well as more sterically demanding bicyclic cores have been reported: (a)
Isshiki, Y.; Kohchi, Y.; Ikura, H.; Matsubara, Y.; Asoh, K.; Murata, T.; Kohchi, M.;
Mizuguchi, E.; Tsujii, S.; Hattori, K.; Miura, T.; Yoshimura, Y.; Aida, S.; Miwa,
M.; Saitoh, R.; Murao, N.; Okabe, H.; Beluni, C.; Janson, C.; Likacs, C.; Schück, V.;
Shimma, N. Bioorg. Med. Chem. Lett. 2011, 21, 1795; (b) Laing, V. E.; Brookings,
D. C.; Carbery, R. J.; Simorte, J. G.; Hutchings, M. C.; Langham, B. J.; Lowe, M. A.;
Allen, R. A.; Fetterman, J. R.; Turner, J.; Meier, C.; Kennedy, J.; Merriman, M.
Bioorg. Med. Chem. Lett. 2012, 22, 472; (c) Adams, M. E.; Wallace, M. B.;
Kanouni, T.; Scorah, N.; O’Connell, S. M.; Miyake, H.; Shi, L.; Halkowycz, P.;
Zhang, L.; Dong, Q. Bioorg. Med. Chem. Lett. 2012, 22, 2411.
We gratefully acknowledge Mario Lobell (Medicinal Chemistry
Wuppertal, Bayer HealthCare AG) and our former colleagues at
Bayer Pharmaceuticals West Haven Yingfu Li, Joachim Rudolph,
Jacques Dumas, and Daniel Auclair for initiating this research pro-
ject. We thank U. Hars, I. Korndoerfer and I. Moarefi at Crelux, Mu-
nich, for excellent service in protein purification, crystallization
and crystal structure determination.
References and notes
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