SAR of benzoylpyridines and benzophenones as p38α MAP kinase inhibitors with oral activity

Article abstract of DOI:10.1016/j.bmcl.2004.03.111

Benzoylpyridines and benzophenones were synthesized and evaluated in vitro as p38α inhibitors and in vivo in several models of rheumatoid arthritis. Oral activity was found to depend upon substitution: 1,1-dimethylpropynylamine substituted benzophenone 10b (IC₅₀: 14nM) and pyridinoyl substituted benzimidazole 17b (IC₅₀: 21nM) showed highest efficacy and selectivity with ED₅₀s of 9.5 and 8.6mg/kg po in CIA.

Full text of DOI:10.1016/j.bmcl.2004.03.111

Bioorganic & Medicinal Chemistry Letters 14 (2004) 3601–3605
SAR of benzoylpyridines and benzophenones as p38a MAP
kinase inhibitors with oral activity
Laszlo Revesz,* Ernst Blum, Franco E. Di Padova, Thomas Buhl, Roland Feifel,
Hermann Gram, Peter Hiestand, Ute Manning and Gerard Rucklin
Novartis Institutes for BioMedical Research, Arthritis and Bone Metabolism, CH-4002 Basel, Switzerland
Received 21 January 2004; revised 22 March 2004; accepted 29 March 2004
Abstract—Benzoylpyridines and benzophenones were synthesized and evaluated in vitro as p38a inhibitors and in vivo in several
models of rheumatoid arthritis. Oral activity was found to depend upon substitution: 1,1-dimethylpropynylamine substituted
benzophenone 10b (IC50: 14 nM) and pyridinoyl substituted benzimidazole 17b (IC50: 21 nM) showed highest efficacy and selectivity
with ED50s of 9.5 and 8.6 mg/kg po in CIA.
Ó 2004 Elsevier Ltd. All rights reserved.
TNFa inhibitors (Etanercept, Infliximab) and IL-1
inhibitors (Anakinra) have demonstrated clinical effi-
cacy in the treatment of rheumatoid arthritis and have
raised the desire to develop small molecules as inhibitors
of TNFa and IL-1. Blockade of p38a1 is a very attrac-
tive option for this purpose, since p38a inhibitors
downregulate production and signalling of TNFa,
IL-1 and in addition inhibit COX-2 induction. The
value of COX-2 inhibitors (Celebrex, Vioxx) has
been proved by their successful use in arthritic
diseases.
imidazoles, we discovered that pyrido[2,3-d]pyrimidine
A was a weak inhibitor, while the ring-opened benz-
oylpyridines and benzophenones4 B were much more
potent. We now wish to report on the in vivo and
in vitro SAR of B.
Benzoylpyridines 6a–c and 7a,b (Scheme 1) were pre-
pared from 2,5-dibromopyridine 1,5 which was reacted
with 2,4-difluoroaniline to render 2,6 employing the
Buchwald7 coupling conditions.
Combining the dilithium anion of 26 and aldehydes 3a–c
yielded alcohols 4a–c. Jones8 oxidation generated the
benzoylpyridines 5a–c. Sonogashira9 coupling of bro-
mides 5b,c with 1,1-dimethylpropynylamine or 1,1-
dimethylpropynol gave rise to 6a–c. Hydrogenation of
6a and 6c over Pd/C gave 1,1-dimethylpropylamine 7a
and 1,1-dimethylpropanol 7b.
Since the discovery of the pyridinylimidazoles,2 several
novel structural classes of p38 inhibitors have been
reported.3 During our own efforts directed towards the
synthesis of p38 inhibitors distinct from the pyridinyl-
R1
Benzophenones 10a, 10b, 11–13 (Scheme 2) were pre-
pared from aldehydes 3a–d, which were first reacted at
)78 °C with 1-bromo-4-lithiobenzene to provide the
corresponding alcohols. Jones8 oxidation of the latter
provided the bromobenzophenones 8a–d. The dibro-
mides 8c,d reacted regioselectively under Buchwald7
coupling conditions with 2,4-difluoroaniline to provide
the bromides 9c,d. Sonogashira9 coupling of 9c,d with
1,1-dimethylpropynylamine yielded propargyl amines
10a and 10b. Hydrogenation of 10b over Pd/C gave
R
F
O
N
R2
X
N
N
N
N
H
H
F
A
B (X = C, N)
* Corresponding author. Tel.: +41-61-324-3273; fax: +41-61-324-3273;
e-mail: laszlo.revesz@pharma.novartis.com
0960-894X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.03.111

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L. Revesz et al. / Bioorg. Med. Chem. Lett. 14 (2004) 3601–3605
R2
increases potency by interacting with the acidic Asp168
F
of p38a.13 The 1,1-dimethylpropynol derivative 6c was
seven times weaker than its NH2-analogue 6b. Satura-
tion of the triple bonds in 6a and 6c led to the 1,1-
dimethylpropylamine 7a and 1,1-dimethylpropanol 7b
with three freely rotatable C–C bonds. The effect of
increased flexibility in the side chain resulted in an 8-fold
loss in potency, with the amine 7a still being three times
more potent than the alcohol 7b. Benzophenones and
benzoylpyridines showed similar SAR; benzophenones
were slightly more potent, when comparing 5a and 6a
with 9a and 10a. 1,1-Dimethylpropynylamine substi-
tuted benzophenones 10a and 10b showed IC50s of 6 and
14 nM, close to the benzoylpyridine analogues 6a,b.
Saturation of the triple bond of 10b to 11 resulted in an
8-fold loss in activity. Introduction of the 1-methyl-4-
hydroxy-4-vinylpiperidine group yielded the highly po-
tent p38a inhibitor 12 (IC50 ¼ 1 nM). Reduction of the
double bond in 12 produced 13 with increased flexibility
of the side chain and an expected (50-fold) loss in
affinity.
Br
Br
a)
b)
R1
+
N
N
H
N
Br
O
F
1
2
3a-c
R2
R2
R1
R1
c)
F
F
O
HO
N
N
H
N
N
H
F
F
5a: R1=Cl, R2=H
5b: R1=Cl, R2=Br
5c: R1=OMe, R2=Br
4a: R1=Cl, R2=H
4b: R1=Cl, R2=Br
4c: R1=OMe, R2=Br
R3
R3
R1
e)
d)
R1
F
F
O
O
N
N
H
N
N
H
F
F
6a: R1=Cl, R3=NH2
6b: R1=OMe, R3=NH2
6c: R1=OMe, R3=OH
7a: R1=Cl, R3=NH2
7b: R1=OMe, R3=OH
Pyridinoyl substituted benzimidazoles 17a and 17b as
well as the benzoyl substituted benzimidazoles 19a and
19b were strong p38a inhibitors, 19a being the most
potent of the series with IC50 ¼ 0.7 nM. As above,
the benzoyl analogues 19a and 19b were 4–10 times
more potent than their pyridinoyl analogues 17a and
17b.
Scheme 1. (a) Pd(OAc)2, NaOtBu, R-(+)-BINAP, 2,4-difluoroaniline,
1,4-dioxane, reflux 1 h, 57%; (b) )78 °C, nBuLi, (2.2 equiv), 2,6 then
add aldehyde 3a–c; 50–60%; (c) CrO3, H2SO4, acetone, room tem-
perature, 10 min, 48–85%; (d) 6a: PdCl2(PPh3)2, CuI, 1,1-dimethyl-
propynylamine, reflux in Et3N 1 h, 63%. 6b: PdCl2(PPh3)2, CuI,
Cs2CO3, 1,1-dimethylpropynylamine, reflux in DIPEA, 30 min, 84%.
6c: PdCl2(PPh3)2, CuI, 1,1-dimethylpropynol, Et3N, DMF, 100 °C,
1.5 h, 70%. (e) Pd/C, H2, EtOH, 15 min, room temperature, 7a: 45%,
7b: 85%.
Compounds with IC50 < 120 nM against p38a were fur-
ther tested in vivo in the acute LPS induced TNFa
release model in the mouse.14 Unsubstituted
benzophenones (R2 ¼ H) 9a and 9b were orally inactive
(Table 1), possibly due to their high lipophilicity. The
hydrophilicity increasing groups 1,1-dimethylpropynyl-
amine, 1,1-dimethylpropynol and 1-methyl-4-hydroxy-
4-vinylpiperidine conferred potent oral activity in 6a–c,
10a,b and 12, which inhibited TNFa by 50–95% at
20 mg/kg po. Benzimidazoles 17a,b and 19a,b were
equally potent, inhibiting TNFa release by 57–93% at
20 mg/kg po. The saturated analogues 11 and 13 were
devoid of oral efficacy.
propylamine 11. The 4-hydroxy-4-vinylpiperidine
substituted benzophenone 12 was obtained by coupling
bromide 9d with vinylstannane 146 under Stille10 con-
ditions. Hydrogenation of 12 gave 13.
Pyridinoylbenzimidazoles 17a,b (Scheme 3) were pre-
pared from aldehydes 15a,b.6 Combining the latter with
the dilithium anion of 26 provided alcohols 16a,b, which
upon Jones8 or MnO2 oxidation rendered the desired
11
benzimidazoles 17a,b.
From the 10 compounds with oral activity in the acute
LPS/TNFa model,14 nine also showed good efficacy in
the subchronic adjuvant induced arthritis (AIA)15 model
in the rat at a dose of 25 mg/kg b.i.d. po; swelling was
inhibited by 36–70% (Table 2). At this stage, compounds
demonstrating low body weight increase in the AIA
model or inhibition of cytochrome P450 isoenzymes16 or
COX-1 inhibition17 or genotoxicity18 were dropped from
further profiling, leaving three structures for further
investigation in the collagen induced arthritis (CIA)19
model in the rat: 10b, 17a and 17b. While 17a proved
ineffective in CIA, 10b and 17b had ED50s of 9.5 mg/kg
qd and 8.6 mg/kg po qd. The ED50 values compared
favourably with two non-pyridinylimidazoles currently
in clinical trials.20;21
Benzoylbenzimidazoles 19a,b (Scheme 4) were prepared
from aldehydes 15a,b,6 which reacted at )78 °C with
1-bromo-4-lithiobenzene to the expected alcohols. The
11
latter were oxidized with MnO2 to the corresponding
ketones. As Buchwald7 reactions failed using the
unprotected imidazoles, a SEM protecting group was
introduced first. Buchwald reaction of 18a,b with 2,4-
difluoroaniline followed by SEM-deprotection yielded
19a and 19b.
Table 1 summarizes the p38a12 IC50 values and the
% inhibition of LPS induced TNFa release in mice upon
oral administration. Bulky R2 substituents such as
bromine in 5b were not favoured, whereas the rigid 1,1-
dimethylpropynylamino group in 6a and 6b increased
p38a inhibitory potency 5–10 fold to IC50 ¼ 19 and
8 nM. One may speculate that the NH2 group in R2
Pharmacokinetic profiles of 10b and 17b in the rat
showed marked differences in their volumes of distri-
bution (Vss) and the maximal plasma concentrations

L. Revesz et al. / Bioorg. Med. Chem. Lett. 14 (2004) 3601–3605
3603
R2
R2
R2
a)
b)
R1
R1
R1
F
O
O
O
N
Br
H
F
3a-d
9a: R1=Cl, R2=H
8a: R1=Cl, R2=H
9b: R1=OMe, R2=H
9c: R1=Cl, R2=Br
9d: R1=OMe, R2=Br
8b: R1=OMe, R2=H
8c: R1=Cl, R2=Br
8d: R1=OMe, R2=Br
NH2
e)
NH2
N
R1
R1
d)
F
c)
F
O
O
OH
N
H
N
H
SnBu3
F
F
10a: R1=Cl
10b: R1=OMe
14
11: R1=OMe
N
N
OH
OH
d)
O
O
F
F
O
O
N
H
N
H
F
F
12
13
Scheme 2. (a) 1. nBuLi, 1,4-dibromobenzene, THF, )78 °C, 5 min, then add aldehyde 3a–d; 70–85%; 2. CrO3, H2SO4, acetone, water, room tem-
perature, 10 min, 50–83%. (b) 9a–c: Pd(OAc)2, NaOtBu, R-(+)-BINAP, 2,4-difluoroaniline, 1,4-dioxane, reflux 20 min; 10–40%. 9d: Pd(OAc)2,
Cs2CO3, R-(+)-BINAP, 2,4-difluoroaniline, 1,4-dioxane, reflux 2.5 h, 65%. (c) 10a: PdCl2(PPh3)2, CuI, 1,1-dimethylpropynylamine, reflux in Et3N,
1 h, 86%. 10b: PdCl2(PPh3)2, CuI, Cs2CO3, 1,1-dimethylpropynylamine, reflux in DIPEA/diglyme (2:1) 3.5 h, 76%. (d) Pd/C, H2, EtOH, 1 h, room
temperature, 72%. (e) Pd(PPh3)4, toluene, 9d, 14,6 100 °C, 12 h, 33%.
N
N
N
NH
NH
NH
R1
R1
a)
b)
R1
F
F
HO
O
O
N
N
N
N
H
H
F
F
15a: R1=Cl
15b: R1=OMe
16a: R1=Cl
16b: R1=OMe
17a: R1=Cl
17b: R1=OMe
Scheme 3. (a) 2,6 nBuLi (2.2 equiv), )78 °C, THF, 20 min, then add aldehyde (0.5 equiv), 10 min, )70 °C, 46–76%. (b) 17a: MnO2, acetone, 30 min,
35 °C, 36%. 17b: CrO3, H2SO4, acetone, water, room temperature, 10 min, 71%.
N
(Cmax), while oral bioavailabilities with 46% and 54% as
well as terminal half lives with 7 and 4.4 h were similar.
Compound 10b showed a high Vss of 9 L kgꢀ1 and a low
N
NH
N
N
SEM
NH
a) b) c)
d) e)
R1
R1
C
max (@ 1 mg/kg po) of 59 nmol, while 17b had a low Vss
F
R1
O
of 1.1 L kgꢀ1 and a high Cmax (@ 1 mg/kg po) of
607 nmol pointing to high plasma protein binding of
17b. Both compounds had a satisfactory selectivity
profile22 (17b was P1000-fold, 10b P100-fold selective
against a panel of 13 kinases).
O
O
N
Br
H
F
15a: R1=Cl
15b: R1=OMe
19a: R1=Cl
19b: R1=OMe
18a: R1=Cl
18b: R1=OMe
Scheme 4. (a) nBuLi (3.3 equiv), 1,4-dibromobenzene (3.0 equiv),
THF, )78 °C, 15 min, add aldehyde (1 equiv), 10 min, )70 °C, 80–90%
of alcohol. (b) MnO2, acetone, reflux 10 min, 80–90%. (c) KN(TMS)2,
THF, )80 °C, 5 min, add SEM-Cl, 0 °C, 5 min, 18a,b: 75–80% (mixture
of regioisomers). (d) Pd(OAc)2, Cs2CO3, R-(+)-BINAP, 2,4-difluoro-
aniline, 1,4-dioxane, reflux 15 min, 77–87%. (e) EtOH/HCl conc. (1:1)
5 min, 60 °C, 19a,b: 80–90%.
In summary, we discovered a series of novel benzoyl-
pyridines and benzophenones as p38a inhibitors.
Appropriate substitution of these structures leads to
compounds with potent oral efficacy in disease models
of rheumatoid arthritis.

3604
L. Revesz et al. / Bioorg. Med. Chem. Lett. 14 (2004) 3601–3605
Table 1
Benzoylpyridines
Benzophenones
Benzimidazoles
Nr
5a
5b
6a
6b
6c
7a
7b
p38aa
101
300
19
TNFab
n.t.
n.t.
50
Nr
9a
p38aa
11
TNFab
6
0
Nr
p38aa
8
TNFab
91
57
17a
17b
19a
19b
9b
38
21
10a
10b
11
6
14
85
95
0
0.7
5
93
90
8
54
91
88
113
1
160
479
n.t.
n.t.
12
13
68
0
51
a IC50(nM).12
b % Inhibition of LPS induced TNFa release in mice at 20 mg/kg po.14
Table 2
Benzoylpyridines
Benzophenones
Benzimidazoles
Nr
6a
6b
6c
AIAa
36
CIAb
n.t.
Nr
10a
10b
12
AIAa
51
CIAb
n.t.
Nr
AIAa
40
CIAb
c
17a
17b
19a
19b
52
23
n.t.
n.t.
45
47
9.5
n.t.
70
46
8.6
n.t.
n.t.
50
a % Inhibition of swelling in adjuvant induced arthritis rats (AIA)15 at 25 mg/kg po b.i.d.
b CIA: collagen induced arthritis in rats.19 ED50 (mg/kg po).
c 10 mg/kg po: 10% inhibition of swelling.
Lys53
References and notes
H
N
Thr106
HN
OH
F
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O
O
His107
Leu108
NH
O
F
H2N
NH
HN
N
N
O
O
H
Met109
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O
O
O
HO
NH2
HN
Asp168
Proposed binding mode of 6b to p38α
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14. Eight-week old female OF1 mice were dosed orally by
gavage with solutions of the compounds in DMSO/
cornoil. One hour after dosing, LPS (20 mg/kg) was
injected iv for stimulation of TNFa release into plasma.
One hour later blood was collected and TNFa was
determined using a mouse specific ELISA.
15. AIA: Adjuvant induced arthritis. Female Wistar rats were
immunized with Mycobacterium tuberculosis at day 0 and
dosed with the compounds twice (b.i.d.) 25 mg/kg po per
day from day 14–20. Swelling of the joints was measured
on day 20.
11. Papadopoulos, E. P.; Jarrar, A.; Issidorides, C. H. J. Org.
Chem. 1966, 31, 615–616.
16. Profiling continued, if IC50 > 2 lM for human P450
isoenzymes CYP1A2, CYP2C9, CYP2D6, CYP3A4.
17. Profiling continued, if IC50 > 80 lM for COX-1.
18. Profiling continued, if Ames assay and the Comet assay (in
vitro with human lymphocytes) were negative.
19. CIA: Collagen induced arthritis. Female (WAGxBUF/F1)
rats were immunized intradermally with bovine nasal
septum type II collagen emulsified in Freund’s incomplete
adjuvant. Swelling started ꢁ10 days after immunization.
Dosing of compounds started on day 13, when swelling
was nearly maximal. Compounds were dosed once (qd)
daily for 10 days.
12. A phosphorylated form of His-p38a MAP kinase (10 ng/
well) of murine origin was used and immobilized GST-
ATF-2 as substrate in the presence of 120 lM cold ATP.
13. The proposed binding mode of benzoylpyridines and
benzophenones to p38a implies, that the carbonyl oxygen
forms a crucial H-bridge to the NH of Met109 and the
difluorophenyl ring accommodates in the lipophilic bind-
ing pocket near Thr106. Reduction of the ketone to an
alcohol or to a methylene group renders molecules inactive
(data not shown).

L. Revesz et al. / Bioorg. Med. Chem. Lett. 14 (2004) 3601–3605
3605
20. Haddad, J. J. Curr. Opin. Invest. Drugs 2001, 2, 1070–
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10b/19b): JNK2 (>10 lM/>10 lM); CDK1: ()32%/0%);
HER-1 (8.8 lM/)10%); c-Abl ()36%/)15%); c-Src ()10%/
0%); Kdr ()33%/)13%); c-Met (1.5 lM/)34%); FGFR
()16%/0%); c-Kit ()12%/0%); IGF1R (0%/0%); HER-2
(4.4 lM/)24%); Flt-3 ()11%/n.t.); c-Raf (0%/n.t.).
23. Revesz, L.; Di Padova, F. E.; Buhl, T.; Feifel, R.;
Gram, H.; Hiestand, P.; Manning, U.; Wolf, R.;
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A. G.; Hickey, E.; Klaus, B.; Madwed, J.; Moriak, M.;
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22. Selectivity profiles were determined in house as
described.23 Kinase (IC50 or % inhibition at 10 lM for