The development of new triazole based inhibitors of tumor necrosis factor-α (TNF-α) production

Article abstract of DOI:10.1016/S0960-894X(03)00238-5

4-Aryl-5-pyridyl and 4-aryl-5-pyrimidyl based inhibitors of TNF-α production, which contain a novel triazole 5-member heterocyclic core, are described. Many pyridyl triazoles containing either an alkyl ether or a substituted aryl side chain on the triazole core showed sub-micromolar activity against LPS-induced TNF-α, while pyrimidyl triazoles containing an ethoxymethyl side chain exhibited even better inhibitory activity. Secondary screening data are presented for the pyrimidyl triazoles. Triazole 14e combined excellent potency with good oral bioavailability in the rat.

Full text of DOI:10.1016/S0960-894X(03)00238-5

Bioorganic & Medicinal ChemistryLetters 13 (2003) 1665–1668
The Development of New Triazole Based Inhibitors of Tumor
Necrosis Factor-ꢀ (TNF-ꢀ) Production
Joshua S. Tullis,a John C. VanRens, Michael G. Natchus,b Michael P. Clark,c,*
Biswanath De, LilyC. Hsieh and Michael J. Janusz
aArray Biopharma, 3200 Walnut Street, Boulder, CO 80301, USA
bXemplar BioSciences, 1201 West Peachtree Street, Suite 800, Atlanta, GA 30309, USA
cProcter and Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Rd, Mason, OH 45040, USA
Received 14 January2003; revised 10 March 2003; accepted 11 March 2003
Abstract—4-Aryl-5-pyridyl and 4-aryl-5-pyrimidyl based inhibitors of TNF-a production, which contain a novel triazole 5-member
heterocyclic core, are described. Many pyridyl triazoles containing either an alkyl ether or a substituted aryl side chain on the tri-
azole core showed sub-micromolar activityagainst LPS-induced TNF- a, while pyrimidyl triazoles containing an ethoxymethyl side
chain exhibited even better inhibitory activity. Secondary screening data are presented for the pyrimidyl triazoles. Triazole 14e
combined excellent potencywith good oral bioavailabilityin the rat.
# 2003 Elsevier Science Ltd. All rights reserved.
In our continuing efforts toward the development of
disease modifying treatments for osteoarthritis, we are
targeting the development of novel cytokine synthesis
inhibitors. The overexpression of cytokines, such as
TNF-a and IL-1b, has been implicated in a number of
serious inflammatorydisorders. Consequentl,y agents
that inhibit the production of TNF-a can decrease levels
of these proinflammatorycytokines, and therebyreduce
inflammation and prevent further tissue destruction in
diseases such as rheumatoid arthritis (RA),1 osteo-
arthritis (OA)2 and Crohn’s disease.
from readilyavailable starting materials. In addition,
both syntheses are amenable to large scale preparation
and have been performed on 100+ g scale. Coupling of
4-fluorophenyl acetylene (1) (Scheme 1) with 4-bromo-
pyridine (2) as described byMangalagiu and co-work-
ers5 gives alkyne 3, which is converted to triazole 4 via
3+2 cycloaddition with sodium azide. While the
unsubstituted parent triazole 4 itself possessed only
modest activity(TNF- a IC50=12.5 mM), numerous
possibilities existed for further functionalization of
compound 4: alkylation with alkyl halides; acylation
with acid chlorides, carbamoyl chlorides and iso-
cyanates; sulfonylation with sulfonyl chlorides; and
arylation with aryl boronic acids. In practice, alkyl chlor-
ides, acyl chlorides and isocyanates reacted with 4 in the
presence of Et3N and 1,2-dichloroethane at either ambient
temperature or 80ꢀC. Arylation was accomplished using
the corresponding aryl boronic acid, Cu(OAc)2 and pyri-
dine.6 Structural assignments were made on the basis of
X-ray crystallography, and in all cases the predominate
isomer proved to have N2 substitution. Table 2 sum-
marizes a broad preliminarysurveyof different appen-
dages to the triazole. We have made amides, carbamates,
sulfonamides, alkylamines, and ureas.
SB2035803 represents a prototypical pyridyl imidazole-
based inhibitor, although numerous structural classes
(e.g., imidazoles (Fig. 1), pyrroles, pyrimidines, pyr-
idines, pyrimidones, indoles, heteroindoles, ureas, and
various fused bicyclic heterocycles) containing a variety
of functionalityhave been reported to inhibit TNF- a
production.4 Herein we wish to report a new structural
class of 4-aryl-5-heteroaryl based TNF-a inhibitors
which contain a novel triazole core.
Syntheses of the described pyridyl and pyrimidyl tri-
azoles were accomplished in 3 and 4 steps, respectively,
The related pyrimidyl triazole series, which was made
analogously to the pyridyl triazoles, provided an added
benefit of a second site of diversity. Coupling of
*Corresponding author. Tel.: +1-513-622-0012; fax: +1-513-622-
3681; e-mail: clark.mp@pg.com
0960-894X/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0960-894X(03)00238-5

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J. S. Tullis et al. / Bioorg. Med. Chem. Lett. 13 (2003) 1665–1668
Table 1. Comparative activityof selected regioisomers a
TNF-a IC50 (nM)
EntryStructure
N1
N2
N3
1
490
1069
N/A
Figure 1. Vicinal aryl/pyridin (pyrimidin)-4-yl TNF-a inhibitors.
2
611
4023
74
aStandard Deviation for enzyme assays were typically Æ30% of the
mean or less.
Table 2. TNF-a inhibition data for pyridyl triazole derivatives sub-
stituted on N2a
Scheme 1. Reagents and conditions: (a) ref 7; (b) NaN3, DMA,
100 ꢀC; (c) R-Cl, Et3N, DCE; (d) Ar-B(OH)2, ref 8.
Compd
R
TNF-a IC50 (nM)
4-fluorophenyl acetylene
1
(Scheme 2) with
5a
3303
2,4-dichloropyrimidine 6 yielded alkyne 7,5 which
underwent [3+2] cycloaddition to give triazole 8. Based
on the surveyof triazole substituents performed on the
pyridyl series, the ethoxymethyl substituent was chosen
to be held constant while a series of substitutents on the
pyrimidine ring was examined. Reaction of triazole 8
with 2-chloromethyl ethyl ether and Et3N at ambient
temperature gave a 4:5:1 mixture of regioisomers
9:10:11 which were separable byHPLC and identified
5b
5c
5d
5e
5f
4803
1315
744
3832
3716
1924
>10,000
7591
490
5g
5h
5i
5j
5k
3756
Scheme 2. Reagents and conditions: (a) ref 7; (b) NaN3, DMF, 75 ꢀC;
(c) EtOCH2Cl, Et3N, CH2Cl2; (d) R-OH or R-NH2, NaH, THF; (e)
R-NH2 neat, Á.
aStandard Deviation for enzyme assays were typically Æ30% of the
mean or less.

J. S. Tullis et al. / Bioorg. Med. Chem. Lett. 13 (2003) 1665–1668
1667
Table 3. TNF-a inhibition data for N1 and N3-ethoxymethyl-sub-
stituted pyrimidyl triazole derivatives
Table 3 displays a comparison between N1 and N3-
ethoxymethyl-substituted pyrimidyl triazole inhibitors.
The N3-substituted inhibitors showed better inhibi-
tion than the corresponding N1-substituted analogues,
mirroring the trend observed in the pyridyl triazole
series. The benzylamino pyrimidine triazole 14a
showed good potency(100 nM). An improvement in
inhibitoryactivitywas seen with both of the methyl-
benzylaminopyrimidine triazoles (14b and 14c). Phe-
noxypyrimidine 14d showed good activity, while
substitution of the phenoxygroup with electron-with-
drawing substituents, such as an acetamido group, on
the 3-position increased the potencydramaticallyto
provide one of our most potent inhibitors (14e). The
3-acetamido analogue 14e displayed an excellent phar-
macokinetic profile. We achieved good oral bioavai-
lablity(F=56%) in the rat while maintaining moderate
half-life (t1/2=2.2 h) and clearance (36.5 mL/min/kg)
values. Finally, triazole 14e showed positive oral effi-
XR
N3-substituted IC50
(nM)a
N1-substituted IC50
(nM)a
compd
compd
14a
100
15a
557
14b
14c
14d
14e
46
54
74
8
15b
15c
15d
15e
1602
306
164
189
10
cacy(25 mg/kg) in the rat iodoacetate in-vivo model.
Currently, we are continuing to optimize characteristics
of the triazole inhibitors to provide more in-vivo
activity.
aStandard Deviation for enzyme assays were typically Æ30% of the
mean or less.
by X-ray crystallography. Reaction of chloropyr-
imidines 9–11 with alcohols and amines under either
basic conditions (NaH, THF) or neat amine at elevated
temperature yielded the desired substituted derivatives
(e.g., 12 and 13). In practice, derivatives of 10 proved to
be 1-2 orders of magnitude less active than derivatives
of 9, while limited quantities prevented a systematic
surveyof derivatives of 11. Table 3 summarizes several
promising substituents of types 12 and 13 for the more
potent triazole inhibitors.
We have reported a novel series of pyridyl and pyr-
imidyl triazole TNF-a production inhibitors. Several of
the pyridyl triazole inhibitors showed sub-mM activityin
the LPS-induced TNF-a assay, while the N3-substituted
pyrimidyl triazoles highlighted in Table 3 showed excel-
lent potencyat or below 100 nM. The 3-acetamido-
phenoxy-pyrimidinyl triazole 14e also has shown an
excellent pharmacokinetic profile and was orallyeffica-
cious in the rat iodoacetate model.
All compounds were tested for the inhibition of
TNF-a production using lipopolysaccharide (LPS)
stimulated human monocytic cells (THP-1).7 Table 1,
which compares the three possible sites for substitu-
tion, reveals a general trend in TNF-a IC50 values
that holds for the pyridyl and pyrimidyl triazoles:
N2>N1>N3.
Acknowledgements
We are grateful to: Dr. F. C. Wireko and M. R. Mootz
for obtaining X-raycrystal data; Richard L. Bohne for
TNF-a assaydata.
References and Notes
Table 2 summarizes a broad preliminarysurveyof
pyridyl triazole substituents: amides, sulfonamides,
carbamates, ureas, alkyl ethers, and aryl groups. In
general, examples from each substituent class were
found to exhibit modest inhibitoryproperties, even
though the absolute potencies of the inhibitors were
quite sensitive to even minor structural variations.
Methoxyphenyl substituents linked with either a car-
bonyl or sulfonyl group (5a and 5b) showed modest
activity, but removal of the linker altogether resulted in
analogues with activityaround 1 mM (5c and 5d). Far
more pronounced substituent effects were observed for
ureas and alkyl ethers. N-methyl-N-phenyl urea 5g
showed moderate activity, but the closely related analo-
gue 5h lost all TNF-a activity. Similarly, ethoxymethyl
ether 5j showed 500 nM potency, but even min changes
resulted in substantial loss of TNF-a activity(e.g., 5i and
5k). Representing the most active substituent in the pyr-
idyl triazole series, the ethoxymethyl group was then
used for the investigation of the pyrimidyl triazole series.
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