Identification of a series of substituted 2-piperazinyl-5-pyrimidylhydroxamic acids as potent histone deacetylase inhibitors

Article abstract of DOI:10.1016/j.bmcl.2009.10.118

Pursuing our efforts in designing 5-pyrimidylhydroxamic acid anti-cancer agents, we have identified a new series of potent histone deacetylase (HDAC) inhibitors. These compounds exhibit enzymatic HDAC inhibiting properties with IC₅₀ values in t

Full text of DOI:10.1016/j.bmcl.2009.10.118

Bioorganic & Medicinal Chemistry Letters 20 (2010) 294–298
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Identification of a series of substituted 2-piperazinyl-5-pyrimidylhydroxamic
acids as potent histone deacetylase inhibitors
b
a
b
b
Patrick Angibaud a, , Kristof Van Emelen , Laurence Decrane , Sven van Brandt , Peter ten Holte ,
Isabelle Pilatte a, Bruno Roux a, Virginie Poncelet a, David Speybrouck a, Laurence Queguiner a,
Sandrine Gaurrand a, Ann Mariën c, Wim Floren c, Lut Janssen c, Marc Verdonck b, Jacky van Dun c,
Jacky van Gompel d, Ron Gilissen d, Claire Mackie d, Marc Du Jardin d, Jozef Peeters d, Marc Noppe d,
Luc Van Hijfte a, Eddy Freyne c, Martin Page c, Michel Janicot c, Janine Arts c
*
a Ortho-Biotech Oncology Research & Development, Department of Medicinal Chemistry, campus de Maigremont BP615, 27106, Val de Reuil, France
b Johnson & Johnson Pharmaceutical Research & Development (J&JPRD), Turnhoutseweg, 30, 2340 Beerse, Belgium
c Ortho-Biotech Oncology R&D, Turnhoutseweg, 30, 2340 Beerse, Belgium
d J&JPRD, ADME-Tox department, Turnhoutseweg, 30, 2340 Beerse, Belgium
a r t i c l e i n f o
a b s t r a c t
Article history:
Pursuing our efforts in designing 5-pyrimidylhydroxamic acid anti-cancer agents, we have identified a
new series of potent histone deacetylase (HDAC) inhibitors. These compounds exhibit enzymatic HDAC
inhibiting properties with IC50 values in the nanomolar range and inhibit tumor cell proliferation at sim-
ilar levels. Good solubility, moderate bioavailability, and promising in vivo activity in xenograft model
made this series of compounds interesting starting points to design new potent HDAC inhibitors.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 17 July 2009
Revised 25 October 2009
Accepted 27 October 2009
Available online 30 October 2009
Keywords:
HDAC inhibitors
Histone deacetylase
Anti-cancer agents
Petasis
Pyrimidylhydroxamic acid
Two enzyme families play a crucial role in controlling the acet-
ylation status of histones, thereby altering chromatin structure and
impacting transcription processes: histones acetyl transferases
(HATs) which catalyze the transfer of an acetyl group to lysine res-
idues of chromatin and histone deacetylases (HDACs) which re-
move an acetyl group from those residues, thus leading to a
changed chromatin structure impacting transcriptional activity.1,2
Inhibiting the HDAC enzymes results in increasing the acetylation
status of chromatin which has been linked to cell cycle arrest and
apoptosis as well as down regulation of genes involved in tumor
progression, invasion, and angiogenesis.3–6 In the past decade,
HDAC inhibition has emerged as an attractive target for the devel-
opment of new anti-cancer agents,7 resulting in the approval of the
HDAC inhibitor (HDACi) vorinostat for Cutaneous T-Cell Lym-
phoma (CTCL),8,9 and in the development of several other hydroxa-
mic acids such as, for example, belinostat10 or panobinostat.11
In recent years, a number of additional nonhistone HDAC sub-
strates have also been identified adding growing evidence that
HDACi exert their pleiotropic effect not only through epigenetic
control.12 Recent data have also demonstrated that HDACi could
target novel therapeutic applications such as neurodegenerative
diseases and inflammation.13–15
We have previously identified R306465 (Fig. 1) as a highly po-
tent class I selective HDACi, showing oral anti-tumor activity in hu-
man xenograft-bearing athymic nude mice.16
In order to expand and optimize this first generation HDACi, we
have explored a series of analogues on the basis that replacing the
O
O
O
HO
HO
HO
N
H
N
N
H
N
N
H
N
N
N
N
N
N
N
O
N
R1
N
N
S
O
1
2
R306465
3
R
* Corresponding author.
E-mail address: pangibau@prdfr.jnj.com (P. Angibaud).
Figure 1. Johnson & Johnson first generation of HDACi: R306465 1, alkyl analogue
2, and targeted compounds 3.
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.10.118

P. Angibaud et al. / Bioorg. Med. Chem. Lett. 20 (2010) 294–298
295
sulfonamide moiety would remove one key element hampering
O
O
O
OH
+
solubility. We first postulated that substituting the SO2 moiety
by a carbon atom would restore the basicity of the nitrogen atom
and re-introduce the possibility of making salts, thus impacting
compound solubility. Indeed replacement of the sulfonyl moiety
by a CH2 in 2 provided an HDACi of similar in vitro potency (see
Table 1) and improved solubility (0.3 mg/mL at pH 4)17 as com-
pared to R306465 (<0.1 mg/mL at pH 4.8).
EtO
EtO
N
a
+
(HO)2B
HO
N
N
NH
R
6a-f
5
4
O
N
R
In addition, the piperazine secondary amine gave us the oppor-
tunity to use the Petasis multicomponent reaction18 as an option to
further introduce chemical diversity on the cap-part of this pyrim-
idyl-based hydroxamic acid series. First attempts were conducted
using 2-phenyl-ethenylboronic acid 6a in order to test the chemis-
try route as 6a is known for its good reactivity in the Petasis reac-
tion. Furthermore we postulate that the resulting double bond in 3
(Fig. 1) would mimic the first phenyl group of the naphtyl moiety
in 2. Finally, it enabled us to introduce a hydroxyl group to allow
for further chemical modifications.
b, c
N
N
N
7a-f
OH
O
O
O
N
H
N
R
d
N
N
N
8a-f
O
OH
Reacting the 2-(piperazin-1-yl)pyrimidylethyl ester 4,19 with
the glycolaldehyde dimer 5 and various boronic acids 6a–f in eth-
anol at room temperature provided us with esters 7a–f. Introduc-
tion of the hydroxamic acid moiety was then realized in three steps
using O-(tetrahydro-2H-pyran-2yl)-hydroxylamine as hydroxyl-
amine source. The first step encompasses the cleavage of the ester
into acids or carboxylates, then a classical coupling reaction en-
abled us to introduce the protected hydroxyl amine. This allowed
purification of the amides 8a–f by chromatography on silica gel.
This synthetic scheme was preferred from direct reaction of the
hydroxylamine with the ester as reported previously for other
HDACi,20 as, in our hands, hydroxamic acids where difficult to sep-
arate from the corresponding acids in case of incomplete reaction.
Tetrahydropyranyl (THP) protection was smoothly removed in
acidic media using trifluoroacetic acid which allowed easy isola-
tion, upon crystallization, of compounds 3a–f as trifluoroacetates.
Enantiomeric separation of 3a by liquid chromatography on chi-
ral phase proved to be difficult. We therefore chose to separate the
two enantiomers of the corresponding esters 7a1, 7a2 and to intro-
duce the hydroxamic acid moiety exactly as described above.
Alternatively, THP-protected hydroxamate 11 (Scheme 2) was
prepared as a key intermediate to rapidly test piperazine substitu-
tion. In one pot, the 2-(piperazin-1-yl)pyrimidylethyl ester 4 was
first saponified into its acid which was reacted with 9 to provide
HO
N
N
3a: R=H
H
R
3b: R=-4-Ph
3c: R=-4-OCH3
3d: R=-4-Cl
3e: R=-3-F
N
N
N
3f: R=-2-F
3a-f
OH
Scheme 1. Reagents and conditions: (a) EtOH, rt, 42–64%; (b) LiOH or NaOH, THF,
H2O, rt, 89–96%; (c) H2N–O–THP, 1-ethyl-3-(30-dimethylaminopropyl)carbodiimide
(EDC), 1-hydroxy-1,2,3-benzo-triazole (HOBT), NEt3, THF, CH2Cl2, rt, 36–90%; (d)
CF3CO2H, MeOH, rt, 72–84%.
O
O
EtO
HO
N
a,b
+
O
N
O
N
N
O
NH
O
4
9
O
O
O
O
N
N
N
c,d
H
N
N
N
N
N
N
H
Fmoc
11
10
O
HO
N
N
e,f
Table 1
H
R
3g: R=-4-CH3
3h: R=-4-CF3
3i: R=-4-F
Enzymatic and antiproliferative potency of compounds 3a–i
N
N
N
Compounds
R
HDAC
Cell proliferation A2780
IC50, nMa SD
3
IC50, nMa SD
OH
1
NA
6
2
39 17
2
NA
H
1.5 0.2
2.0 0.1
0.9 0.1
0.95 0.1
1.2 0.2
1.2 0.3
2b
1.0 0.1
2.1 0.3
1.2 0.3
1.0 0.1
1.8 0.3
1.05 0.1
1.2 0.1
66
25
29b
18
17
8
8
Scheme 2. Reagents and conditions: (a) (i) NaOH 1 N, THF, rt, 16 h then (ii), Na2CO3,
H2O, rt, 5 h, crystallized in CH3CN, 40%; (c) H2N–O–THP, EDC, HOBT, NEt3, THF,
CH2Cl2, rt, 68%; (d) Piperidine, CH2Cl2, rt, 59%. (e) EtOH, rt, 15–29%; (f) CF3CO2H,
MeOH, rt, 64–81%.
3a
3b
3c
3d
3e
3f
3g
3h
3i
3a1
3a2
3i1
3i2
–4–Ph
–4–OCH3
–4–Cl
–3–F
–2–F
–4–CH3
–4–CF3
–4–F
Hc
1
6
36 14
<30b
the Fmoc-protected piperazine acid 10 with a moderate yield of
40%. THP-hydroxylamine was then introduced as in Scheme 1
and the Fmoc protection removed by reaction with piperazine in
CH2Cl2 at room temperature to provide 11. Petasis multicompo-
nent reaction could then be performed on 11, however with low
yields, and removal of the THP by trifluoroacetic acid then gave
compounds 3g–i.
All compounds were tested for their ability to inhibit histone
deacetylase activity of a mixture of HDAC enzyme obtained from
a nuclear HeLa cell extract and to inhibit ovarian carcinoma
(A2780) cell proliferation.21,22
18
65 18
32 12
40
30
27 13
31 12
2
5
7
Hd
–4–Fc
–4–Fd
NA = not applicable.
a
Mean results from experiments performed in triplicate.
Single experiment.
(+) enantiomer.
(ꢀ) enantiomer.
b
c
d

296
P. Angibaud et al. / Bioorg. Med. Chem. Lett. 20 (2010) 294–298
EtO2C
Results from Table 1 above clearly show that replacement of the
EtO2C
N
N
a
naphtalene-2-sulfonyl moiety by phenylbutenol group provided
compounds of similar in vitro potency. Substitution of the phenyl
ring does not seem to have significant impact on enzymatic or
anti-proliferative potency despite introduction of electron-with-
drawing or electron-donating substituent. Since hydroxamic acids
are very efficient Zn2+ chelators, this preliminary results may indi-
cates that additional interactions generated by the phenyl ring,
probably orientated towards the solvent region of the tube-shaped
catalytic site described for a bacterial histone deacetylase by Finnin
et al.,23 are not key drivers of potency. It is also interesting to note
that stereochemistry of the carbon linked to the piperazinyl moiety
has virtually no influence on in vitro potency. Thermodynamic sol-
ubility of compound 3a (>10 mg/mL at pH 4.6 and 1.1 mg/mL at pH
7.4) was greatly increased as compared to R306465 (<0.1 mg/mL at
pH 4.8 and 7.7), thus indicating achievement of our first goal. This
property was also confirmed with compounds 3i1, 3i2, and 21, all
showing a solubility >5 mg/mL at pH 4. As introduction of the hy-
droxyl group was not disturbing interaction with the catalytic site
we were interested in further investigation structure–activity rela-
tionships (SAR) at that position and especially in testing introduc-
tion of solubility enhancing substituents. For the sake of
comparison we replaced the hydroxyl by an hydrogen (compound
3j) using reductive amination of 4 with commercially available
butanone 12, followed by introduction of the hydroxamic acid
moiety in three steps as described before (Scheme 3). Compound
3j showed a similar potency as 3a (Table 2) confirming that the hy-
droxyl moiety is not making key interactions with the catalytic
site.
N
N
N
N
N
Ph
N
Ph
7a
13
b,c or
b,d
OH
e,f,g
OMe
O
EtO2C
N
e,f,g
Ph
HOHN
N
N
N
N
N
N
N
Ph
N
14: X= O
15: X= N-CH3
3k:Y=OCH3
Y
X
3l: Y=
N
O
3m: Y=
N
NCH3
Scheme 4. Reagents and conditions: (a) NaH, CH3I, THF, 0 °C rt, 34%; (b) MsCl, NEt3,
CH3CN, 5 °C rt; (c) morpholine, K2CO3, CH3CN, 80 °C, 84%; (d) N-methylpiperazine,
K2CO3, CH3CN, 80 °C, 33%; (e) LiOH, THF, H2O, rt, 83%-quantitative; (f) H2N–O–THP,
EDC, HOBT, NEt3, THF, CH2Cl2, rt, 35–89%; (g) CF3CO2H, MeOH, rt, 44–57%.
onic acid ester obtained by reaction of methanesulfonylchloride
onto 7a, followed by introduction of the hydroxamic acid moiety
on the resulting esters 14 and 15 (Scheme 4). Compounds 3l and
3m showed ꢁ10-fold drop in antiproliferative IC50 as compared
with 3a (Table 2).
Petasis multicomponent reaction is also a powerful tool to pre-
pare alpha-amino acids using glyoxalic acid and boronic acids. We
could therefore rapidly access amides 3n and 3o using the pathway
depicted in Scheme 5. However for these two compounds we also
noticed a ꢁ5-fold drop in antiproliferative activity. For compounds
3l–o, enzymatic potency in inhibiting a mixture of HDAC enzyme,
obtained from a nuclear HeLa cell extract, stayed comparable to 3a
with the exception of 3l being slightly weaker (Table 2) but still in
the nanomolar range.
As cyclic amines such as 3l and 3m or amides were not suitable,
we thought to replace the hydroxyl group of 3a by a small, proton-
able amino moiety. We therefore prepared the phtalimide precur-
sor 17 by Mitsunobu reaction on ester 7a (Scheme 6). However
reaction of 17 with hydrazine in the classical conditions did not
give us the awaited 4-phenyl-2-piperazinyl-but-3-enylamine 18
but rather the 3-phenyl-1-(piperazinylmethyl)-allylamine deriva-
tive 19. Formation of 19 might be the result of the rearrangement
of a transient aziridinium similarly as already proposed on piperi-
dines bearing beta-amino alcohol chain by Frizzle et al.24 We took
Alkylation of ester 7a with methyliodide provided methoxy
intermediate 13 and further methoxy analogue 3k showing a
similar potency as 3a (Scheme 4). Bulkier aminogroups were intro-
duced (compounds 3l and 3m) by substitution of the methanesulf-
O
O
O
HOHN
a,b,c,d
N
EtO
N
+
N
N
N
N
N
Ph
Ph
NH
3j
4
12
Scheme 3. Reagents and conditions: (a) 4-phenylbut-3-ene-2-one, Ti(OEt)4, 1,2-
dichloroethane, rt, 8%; (b) NaOH, EtOH, H2O, 80 °C; (c) H2N–O–THP, EDC, HOBT,
NEt3, THF, CH2Cl2, rt, 70%; (d) CF3CO2H, MeOH, rt, 44%.
Table 2
Evaluation of the importance of the hydroxyl moiety (R = H)
O
O
O
N
N
R1
OH
+
EtO
N
N
a
H
N
N
(HO)2B
O
+
Ph
O
HO NH
N
N
N
N
4
Ph
NH
R1
HDAC
Cell proliferation
A2780
EtO2C
Compounds
HOHN
N
b or c
d,e,f
IC50
,
IC50, nMa
N
N
nMa SD
N
O
Ph
N
Ph
3j
–CH3
1.7 0.2
20b
16
NR1R2
NH
OH
3a
3k
3l
3m
3n
3o
21
–CH2OH
–CH2OCH3
–CH2–1-morpholino
–CH2–4-methylpiperazin–1yl
–C(O)-morpholine
–C(O)NHMe
2
0.1
1.5 0.2
11
6.9 0.4
25
8
O
45 11
R1
2
315 154
392 189
124 26
159 11
281 137
3o:
3n
N
O
N
R2
:
7
1
3.3 0.1
3.8 0.7
Scheme 5. Reagents and conditions: (a) glyoxalic acid, 2-phenyl-ethenylboronic
acid, EtOH, 60 °C, 87%; (b) morpholine, EDC, HOBT, NEt3, THF, CH2Cl2, rt, 38%; (c)
CH3NH2ꢂHCl, EDC, HOBT, NEt3, THF, CH2Cl2, rt, 57%; (d) LiOH or NaOH, THF, H2O, rt,
71–73%; (f) H2N–O–THP, EDC, HOBT, NEt3, THF, CH2Cl2, rt, 71–74%; (g) CF3CO2H,
MeOH, rt, 75–87% .
NA
NA = not applicable.
a
See Table 1.
Single experiment.
b

P. Angibaud et al. / Bioorg. Med. Chem. Lett. 20 (2010) 294–298
297
O
O
b
O
a
EtO
N
N
NH2
but
Ph
EtO
N
N
+
NH
N
N
N
N
Ph
N
N
N
Ph
O
N
Ph
NH2
19
17
7a
O
OH
N
18
O
O
O
c,d
e,f,g
HO
19
HO
N
N
H
N
Fmoc
N
N
HN
N
N
NH2
N
N
Ph
Ph
21
20
Scheme 6. Reagents and conditions: (a) 1H-isoindole-1,3(2H)-dione, P(nBu)3, DIAD, CH2Cl2, rt, 52%; (b) NH2NH2ꢂHBr, EtOH, rt, 98%; (c) LiOH, THF, H2O, rt; (d) 1[[(9H-fluoren-
9-ylmethoxy)carbonyl]-oxy]-2,5-pyrrolidinedione, THF, rt, 82%; (e) H2N–O–THP, EDC, HOBT, NEt3, THF, CH2Cl2, rt, 76%; (f) piperidine, CH2Cl2, rt, 56%; (g) CF3CO2H, MeOH, rt,
87%.
this opportunity to prepare hydroxamic acid 21, first protecting the
amino moiety by Fmoc and then introducing THP-protected
hydroxylamine after saponification of the ester function. Com-
pound 21 displayed similar HDAC inhibiting potency on enzyme
as 3a showing that variation of linker size could be tolerated. This
observation prompted us to examine the influence of longer dia-
mine linkers (Scheme 7 and Table 3).
Esters 25, 26, and 27 were, respectively, prepared by condensa-
tion of boc-protected 4-aminopiperidine, 4-(aminomethyl)piperi-
dine, and boc-protected-2-amino-methylmorpholine onto 2-meth-
anesulfonylpyrimidine-5-carboxylic acid ethyl ester 22.19 Then
Petasis reaction was performed onto 25–27 and hydroxamic acid
functionality was introduced as described in Scheme 1 (Scheme 7).
All ligands were found to be equipotent with regard to enzy-
matic activity whereas Linker B (4-aminopiperidine) and linker D
(2-methylamino-morpholine) were slightly less potent in the cel-
lular assay.
Table 3
Evaluation of several linker moieties (R = H)
Compounds
Linker
HDAC
Cell proliferation A2780
IC50, nMa
IC50, nMa
3a
28
29
30
A
B
C
D
6
7
2
5
25
8
219b
47b
1.5 0.2
8b
295b
a
See Table 1.
Single experiment.
b
As demonstrated by the results from Tables 1–3, a wide range of
Petasis substitution on the 2-piperazinyl-5-pyrimidyl-hydroxamic
acid moiety gave birth to a novel series of potent in vitro HDAC
inhibitors. Compounds 3a and 3i2 showed an acceptable pharma-
cokinetic profile (see Table 4) with a bioavailability in rat of
19–22%, similar to the bioavailability of 1 (R306465).
Compound 3a, 3i1, and 3i2 were evaluated in an animal model
allowing noninvasive real-time evaluation of the response to HDAC
inhibitors using whole-body imaging.25 Human A2780 ovarian
carcinoma cells were engineered to express ZsGreen fluorescent
protein under control of the p21waf1,cip1 promoter, sub-cutaneously
grafted to athymic nude mice, and induction of fluorescence
in vivo was measured after 3 days of treatment. Results are reported
as increased fluorescence intensity as compared to R306465 tested
in same conditions and normalized to 1 (Fig. 2). This allowed rapid
comparison of compounds 3a, 3i1, and 3i2 with R306465 as regards
to their anti-tumor potency. Preliminary results indicate that the
three compoundsmaypossess an in vivo efficacy in thatmodelsupe-
rior to R306465. Compounds 3i1 and 3i2 showed also similar in-
crease in fluorescence intensity (3–4-fold compared to R305465)
confirming that their stereochemistry had no influence. 21 was cho-
sen as a representative of compounds possessing decreased antipro-
liferative activity as compared to R306465 and showed reduced
fluorescence than R306465.
H
O
N
H
Boc EtO2C
23
HN
N
N
Boc
HN
24
N
c
SO2Me
HN
22
a, b
a, b
NH2
EtO2C
EtO2C
NH2
EtO2C
N
N
N
N
N
N
N
N
N
NH2
O
NH2
26
d,e,f,g
27
25
O
N
OH
Ph
Compound 3i2, has been tested towards a broad panel of re-
combinant HDAC enzymes in vitro and compared to compound 1
(R306465) (see Table 5).
Linker
HO NH
N
NH
With the exception of HDAC4, 10 and 11 where 3i2 showed a
10–50-fold drop in inhibiting potency compared to R306465, the
overall profile of both compounds are very similar, even if 3i2
seems slightly less potent (1–3-fold). Compound 3i2 showed
activity towards all HDAC enzyme tested with some specificity
for class I inhibition, a class of HDACs where activity is key for
uncontrolled proliferation of cancer cells.26 Lowest in vitro potency
was observed towards HDAC4, 6, and 7.
N
N
N
N
NH
N
O
HN
28
29
30
D
A
3a
B
C
Scheme 7. Reagents and conditions: (a) 23 or 24, K2CO3, CH3CN, rt, 53–75%; (b)
CF3CO2H, CH2Cl2, rt, 35–96%; (c) 4-aminomethyl-piperidine, K2CO3, CH3CN, rt, 33%;
(d) 5 + 6a, EtOH, rt, 47–73%; (e) NaOH or LiOH, THF, H2O, rt; (f) H2N–O–THP, EDC,
HOBT, NEt3, THF, CH2Cl2, rt, 4–54%; (g) CF3CO2H, MeOH, rt, 72–85%.

298
P. Angibaud et al. / Bioorg. Med. Chem. Lett. 20 (2010) 294–298
Table 4
Rat DMPK properties of compounds 3a and 3i2
CLa (L/h/kg) (IV)
Vdss (L/kg) (IV)
T1/2 (h) 2 h to 8 ha (IV)
AUC0-inf (ng h/mL) (po)
F (%)
a
a
b
Compounds
AUC0-inf (ng h/mL) (IV)
1
3a
3i2
2654
413
521
0.8
5.9
4.6
0.6
5.8
1.6
1.5
2.6
0.8c
3381
316
466
20
19
22
a
b
c
Study in male Sprague-Dawley rats dosed at 2.5 mg/kg in water at pH 4.4.
Study in male Sprague-Dawley rats dosed at 10 mg/kg in water at pH 4.5.
Half life determined from 1 h till 4 h post dose.
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Figure 2. Folds increase of fluorescence for compounds 3a, 3i1 and 3i2 as compared
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Table 5
Comparison of activity towards all HDAC enzymes21
Class
HDAC
R306465
3i2
IC50, nMa SD
IC50, nMa SD
acetonitrile, 1/1) and submitted for concentration measurement using
generic UPLC method.
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a
I
I
I
I
IIa
IIa
IIa
IIa
IIb
IIb
IV
1
2
3
8
4
5
7
9
6
2.5 0.4
7.1 05
17.9 2.5
9
9
3
3
30
30
3
2
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Biology Corporation (www.reactionbiology.com, Malvern PA) using the
‘Spectrum’ assay platform.
27 13
4.6 0.35
7.1 2.3
207 23
21.8 2.6
102 11.5
40.7 3.2
224 33
42.6 1.5
20.7 1.4
46
28
66
8
1
4
10
11
4.3 1.1
2.1 0.6
a
Mean data from experiments performed in triplicate.
22. Van Brandt, S.F.A.; Van Emelen, K.; Angibaud, P.R.; Marconnet-Decrane, L.F.B.
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modified to adapt to 384 well plates.
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In conclusion, we have identified a series of novel 2-piperazi-
nyl-5-pyrimidyl-hydroxamic acids HDACi that are characterized
by high potency on HDAC HeLa cellular extract and cellular anti-
proliferation assay and have demonstrated improved solubility as
compared to our starting molecule 1. First in vivo evaluation of
leads 3a and 3i2 indicates superior potential as compared to
R306465. These results warrants more in depth evaluation of this
series.