Discovery of the first histone deacetylase 6/8 dual inhibitors

Article abstract of DOI:10.1021/jm400390r

We disclose the first small molecule histone deacetylase (HDAC) inhibitor (3, BRD73954) capable of potently and selectively inhibiting both HDAC6 and HDAC8 despite the fact that these isoforms belong to distinct phylogenetic classes within the HDAC family of enzymes. Our data demonstrate that meta substituents of phenyl hydroxamic acids are readily accommodated upon binding to HDAC6 and, furthermore, are necessary for the potent inhibition of HDAC8.

Full text of DOI:10.1021/jm400390r

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Brief Article
Discovery of the First Histone Deacetylase 6/8 Dual Inhibitor
David E. Olson, Florence F. Wagner, Taner Kaya, Jennifer P. Gale, Nadia Aidoud, Emeline
L. Davoine, Fanny Lazzaro, Michel Weiwer, Yan-Ling Zhang, and Edward B. Holson
J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/jm400390r • Publication Date (Web): 14 May 2013
Downloaded from http://pubs.acs.org on May 17, 2013
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Discovery of the First Histone Deacetylase 6/8 Dual Inhibitors
David E. Olson, Florence F. Wagner, Taner Kaya, Jennifer P. Gale, Nadia Aidoud, Emeline L. Davoine,
Fanny Lazzaro, Michel Weïwer, YanꢀLing Zhang, Edward B. Holson*
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Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, 7 Cambridge Center, Cambridge, MA 02142,
USA
KEYWORDS: Histone Deacetylase, isoform selectivity, HDAC6, HDAC8, dual inhibitor
Supporting Information Placeholder
ABSTRACT: We disclose the first small molecule histone deacetylase (HDAC) inhibitor (3, BRD73954) capable of potently and
selectively inhibiting both HDAC6 and HDAC8 despite the fact that these isoforms belong to distinct phylogenetic classes within
the HDAC family of enzymes. Our data demonstrate that meta substituents of phenyl hydroxamic acids are readily accommodated
upon binding to HDAC6, and furthermore, are necessary for the potent inhibition of HDAC8.
Histone deacetylases (HDACs) are enzymes that catalyze the
removal of acetyl groups from the εꢀnitrogen of lysine resiꢀ
dues on histone as well as nonꢀhistone proteins.1 Such postꢀ
translational modifications can regulate numerous cellular
processes, including gene expression,2 making these enzymes
attractive targets for the treatment of cancer3 as well as psyꢀ
chiatric,4 metabolic,5 and infectious diseases.6 These enzymes
can be divided into the NAD+ꢀdependent Sirtuins (Class III)
and the Znꢀdependent HDACs. The latter can be divided into
three classes, one of which (Class II) is further subdivided into
two subclasses (Figure 1): class I (HDACs 1, 2, 3, and 8),
class IIa (HDACs 4, 5, 7, and 9), class IIb (HDACs 6 and 10),
and class IV (HDAC11).7
al isoforms and, 3) potentially provide better tolerated theraꢀ
peutic agents.
Currently, many of the clinically relevant HDAC inhibitors
(e.g., LBHꢀ589 (Panobinostat), SAHA (Vorinostat)) are neiꢀ
ther class nor isoform selective. LBHꢀ589 (a hydroxamic acꢀ
id) is a prototypical example of a multiꢀisoform inhibitor
demonstrating potent inhibition across HDAC classes I, IIa
and IIb (Figure 1). In contrast, MSꢀ275 (Entinostat, an orthoꢀ
aminoanilide) is an example of a subꢀclass I selective inhibitor
with potent activity towards HDACs 1, 2, and 3 only. While
these agents demonstrate clinical efficacy towards select neoꢀ
plasms, all exhibit doseꢀdependent toxicity such as nausea,
fatigue, and thrombocytopenia.8 Furthermore, it has been
demonstrated that the concurrent inhibition of HDACs 1 and 2
contributes to myelosupression via a mechanism based toxiciꢀ
ty.9 Selective inhibition of only the desired HDAC isoforms
has been hypothesized to yield drugs that elicit fewer side
effects and are better tolerated.10 Until now, medicinal chemꢀ
ists have focused on developing compounds selective for eiꢀ
ther a few isoforms within the same class (e.g., HDACs 1, 2,
and 3) or a single isoform (e.g., HDAC6 or HDAC8).11 A repꢀ
resentative set of inhibitors selective for different combinaꢀ
tions of HDAC isoforms is shown in Figure 1. Ideally, the
development of a “toolkit” of inhibitors encompassing the
various permutations of selectivities within and across the
HDAC classes would, 1) refine our structural understanding of
the similarities and differences between these enzymes, 2)
further biological investigations into the functions of individuꢀ
Figure 1. Binding profiles and chemical structures of HDAC inꢀ
hibitors. Colored blocks denote IC50 values <300 nM. Evolutionꢀ
ary relationships between the various Znꢀdependent HDACs are
shown. The lengths of the branches are not proportional to evoluꢀ
tionary distance (adapted from ref 2b).
Herein, we report our efforts towards this endeavor and disꢀ
close that it is possible to achieve simultaneous inhibition of
HDACs 6 and 8, two isoforms with disparate sequence hoꢀ
mology belonging to distinct classes. Dual inhibition of these
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ꢀM). However, the simple meta methyl substituted compound
8 displayed increased potency and selectivity for HDAC6
(IC50 = 0.65 ꢀM) resembling the overall binding profile of the
phenyl hydroxamic acid 1.14
two enzymes might prove beneficial in a number of indicaꢀ
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tions. For instance, both HDAC6 and HDAC8 have been imꢀ
plicated in breast cancer metastasis,3a and we speculate that
inhibition of both isoforms could potentially abrogate any
functional redundancy exhibited by these enzymes. Furtherꢀ
more, inhibition of HDAC8 has shown promise as an effective
strategy for treating neuroblastoma,12 while inhibition of
HDAC6 has proven useful for treating a variety of cancers due
to its effects on the ubiquitin pathway as a single agent and in
combination therapies.13 Dual inhibition of these two isoforms
could provide a larger therapeutic window and have beneficial
additive or synergistic effects in neuroblastoma and/or related
neoplastic disorders.
Table 1. IC50 values for HDACs 2, 4, 6, and 8
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Recently, we reported our efforts towards developing ligandꢀ
efficient selective inhibitors of HDAC6 such as 1.14 We disꢀ
covered that small capless phenyl hydroxamic acids were poꢀ
tent and selective inhibitors of HDAC6. Furthermore, we obꢀ
served that a variety of extended para substituents such as the
phenethyl carboxamide of compound 2, were not only toleratꢀ
ed, but also did not reduce the selectivity of these inhibitors
for HDAC6 (>100ꢀfold versus HDACs 2, 4, and 8). While
exploring positional and structural modifications to these pheꢀ
nyl hydroxamic acids, we discovered that transposing the
phenethyl carboxamide substituent from the para (2) to the
meta (3) position not only retained HDAC6 inhibitory activity
(IC50 = 0.036 ꢀM), but resulted in a 10ꢀfold increase in potenꢀ
cy for HDAC8 (IC50 = 0.12 ꢀM) with a concomitant reduction
in potency for HDAC2 (Table 1). To the best of our
knowledge, compound 3 (BRD73954) represents the first
HDAC inhibitor capable of selectively and potently inhibiting
HDAC6 (Class IIb) and HDAC8 (Class I) simultaneously.15
Next, in order to understand this unique inter-class structure
activity relationship, we probed the effect of different meta
substitutions on potency and selectivity. We synthesized a
series of compounds varying the linking motifs at this position
as well as the physicochemical and steric properties of these
molecules (Table 1).16 A comparison between the phenethyl
carboxamide 3 and the 3ꢀpyridylethyl carboxamide 4 suggests
the importance of the substitutent’s hydrophobicity for achievꢀ
ing potent inhibition of HDAC8, as the less hydrophobic comꢀ
pound 4 exhibited reduced potency for HDAC8 (IC50 = 0.42
ꢀM), but not for HDAC6 (IC50 = 0.059 ꢀM).
aValues are the average of at least two experiments. Data are
shown as IC50 values in ꢁM ± standard deviation. Compounds
were tested using a 12ꢀpoint dose curve with 3ꢀfold serial dilution
starting from 33 ꢁM.17 bData were taken from ref 14. Data for
additional compounds are shown in the supporting information.
Next we varied the linker length to examine the effects on
HDAC6 and 8 inhibition as well as to define the minimal
pharmacophoric elements necessary for dual inhibition of theꢀ
se isoforms. Utilizing an amide linkage, we shortened the
meta substituent of compound 3 by one (benzyl carboxamide,
5) or two carbons (phenyl carboxamide, 6) and observed little
effect on potency for HDAC6 (IC50 = 0.034 and 0.057 ꢀM,
respectively) or HDAC8 (IC50 = 0.21 and 0.11 ꢀM, respectiveꢀ
ly). Moreover, both compound 5 and 6 remained highly selecꢀ
tive with a >50ꢀfold preference for HDAC6 and 8 as compared
to HDACs 2 and 4. Further truncation of this series to the
simple methyl carboxamide 7 resulted in a significant loss in
potency for HDAC6 (IC50 = 2.5 ꢀM) and HDAC8 (IC50 = 14
Finally, after observing the surprisingly poor inhibition disꢀ
played by the methyl carboxamide 7 towards HDACs 6 and 8,
we turned our attention to alternate meta linking motifs. Reꢀ
moval of the carbonyl group in 6 provided the methylene
linked aniline 9, which displayed a significant loss in potency
and selectivity. Ultimately, we replaced the fourꢀatom spacer
in 3 with the highly rigid meta cinnamide linkage to provide
compound 10. Compound 10 displayed excellent potency for
HDAC6 (IC50 = 0.021 ꢀM) and HDAC 8 (IC50 = 0.037 ꢀM) as
well as greater than 130ꢀfold selectivity versus HDACs 2 and
4.
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Table 2: IC50 values for HDACs 1ꢀ9
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aValues are the average of at least two experiments. Data are shown as IC50 values in ꢁM ± standard deviation. Compounds were
tested using a 12ꢀpoint dose curve with 3ꢀfold serial dilution starting from 33.3 ꢁM.17
To ascertain the selectivities of 3 and 10 across the broader
family of HDAC isoforms, we profiled these compounds
against HDACs 1ꢀ916 (Table 2). Compounds 3 and 10 mainꢀ
tained excellent selectivity towards HDAC6 and HDAC8 as
compared to the other class I and class II HDACs tested, as
these compounds were 75ꢀ and 130ꢀfold less potent for the
next closest isoforms, respectively. These selectivities are
comparable to those exhibited by Tubastatin A11e and 11 (PCIꢀ
34051),11f state of the art HDAC6ꢀ and HDAC8ꢀselective inꢀ
hibitors, respectively. Although structurally simple, comꢀ
pounds 3 and 10 exhibit remarkable selectivity within this
family of closely related zinc hydrolases, and this selectivity
may translate to more distantly related metalloenzymes.
Compound 10 represents the most potent and selective dual
inhibitor of HDACs 6 and 8 reported to date.
in HDAC6 is reminiscent of other computational reports on
this isoform.20,11e
Following the same docking procedures in HDAC8, comꢀ
pound 3 achieves optimal chelation geometry and forms key
Hꢀbonds with His129 and His130 (Figure 2B). In contrast to
the binding mode observed in HDAC6, the metaꢀphenethyl
carboxamide in 3 resides in a deep secondary pocket whose
boundaries are defined by Tyr293, Phe139, and Lys20 (Figure
2D). This secondary hydrophobic pocket (formed via a conꢀ
formational change in Phe139) has been previously described
to accommodate similar “Lꢀshaped” ligands, such as 11,11f
a
potent and selective inhibitor of HDAC8, as well as other meꢀ
taꢀsubstituted hydroxamic acids.21 The role of this secondary
binding pocket in HDAC8 affinity is evident when comparing
the binding affinity of compound 1 (HDAC8, IC50 = 1.9 ꢀM)
versus compound 3 (HDAC8, IC50 = 0.12 ꢀM) which extends
into this space (Figure 2, B and D). In HDAC8, the metaꢀ
substituent forms key hydrophobic interactions and extends
into a well defined secondary pocket leading to increased poꢀ
tency (cf. compound 1 vs 3 ), whereas in HDAC6, this substitꢀ
uent is exposed to solvent, a finding that is consistent with the
observed SAR.
Intrigued by the ability of a small molecule ligand to preferenꢀ
tially bind phylogenetically dissimilar isoforms, we performed
molecular docking simulations of compound 3 into model
structures of HDAC6 and HDAC8. We chose compound 3
with the meta amide linkage to rationalize the observed strucꢀ
ture activity relationships of a larger subset of compounds (see
compounds 3-6). For HDAC6, we generated a homology
model using a multiple mapping method with multiple temꢀ
plates (HDACs 4 and 7) as described by the Fiser group
through an automated web server (M4T Server ver 3.0).17 For
HDAC8 we used the crystal structure reported by Somoza and
colleagues in 2004 (see supporting information for details,
PDB code 1VKG.A).18 For both enzymes, docking runs using
inducedꢀfit models were performed with Glide XP19 followed
by ligand minimization in MOE (Chemical Computing Group,
Inc.).
We performed molecular docking simulations with compound
3 in HDAC6 and the results are shown in Figure 2 (A and C).
Compound 3 adopts an optimal binding pose in the catalytic
domain and forms key Hꢀbonds with His130, His131 and
Tyr302. These residues are critical as they stabilize the inhibiꢀ
tor in a binding conformation that allows for efficient zinc
atom chelation. This coordination complex is further stabiꢀ
lized by hydrophobic interactions between the phenyl linkage
of compound 3 and residues Phe140, Phe200, and Leu269
(Figure 2C). Additionally, the meta linked phenethyl carboxꢀ
amide of 3 extends from this shallow binding domain into
solvent space devoid of close contacts with the protein surface.
This is consistent with the observed SAR of compounds 3-6
which demonstrate no significant change in HDAC6 potency.
In addition, the shallow and more accessible binding domain
Figure 2. Compound 3 docked into HDACs 6 (A and C) and 8 (B
and D). The enzymes in C and D are aligned, demonstrating that
3 occupies distinct subꢀpockets in HDAC6 and HDAC8.
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Next, we attempted to validate the observed biochemical poꢀ
and concentrated under reduced pressure. The resulting solid
was purified by flash chromatography on silica gel. Next, the
purified material was dissolved in 1:2 mixture of
DCM/MeOH (0.1 M). The resulting solution was cooled to 0
ºC before the addition of 50 wt% aqueous hydroxylamine (30
equiv) followed by 1M NaOH(aq) (10 equiv). The reaction was
monitored by LCMS. After completion, the solvent was reꢀ
moved under reduced pressure and the resulting solid was
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tencies and selectivities of these HDAC6/8ꢀselective inhibitors
in a cellular context by examining their HDAC6 activity.22
HeLa cells were treated with inhibitors for 48 h at 10 ꢀM, and
the resulting acetylation changes in αꢀtubulin (a known subꢀ
strate for HDAC6)23 and histone H3 (a known substrate for
HDACs 1, 2, and 3) were assessed (Figure 3).1b While treatꢀ
ment with compounds 3 and 10 resulted in a robust increase in
αꢀtubulin acetylation, no change in the acetylation state of H3
was observed, which is consistent with the ability of these
compounds to inhibit HDAC6 but not HDACs 1, 2, or 3 in the
biochemical assay. In contrast, increases in the acetylation of
αꢀtubulin as well as H3 were observed when the cells were
treated with the panꢀinhibitor SAHA.
a
dissolved in water. The pH was adjusted to 7 with 1N HCl(aq)
,
and the product precipitated. Typically, no further purification
was necessary; however, preparatory HPLC was used in select
cases.
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ASSOCIATED CONTENT
Supporting Information. Analytical data for all final compounds
as well as procedures for the HDAC inhibition assay, cell culture
experiments, and computational chemistry. This material is availꢀ
able free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
Figure 3. Treatment of HeLa cells for 48h with compounds 3 and
10 increased AcꢀTubulin but not AcꢀH3. Concentrations in ꢀM
are shown in brackets. GAPDH was used as a loading control.
* Phone: 617ꢀ714ꢀ7454
Eꢀmail: edholson@broadinstitute.org
Author Contributions
The manuscript was written through contributions of all authors.
All authors have approved the final version of the manuscript.
CONCLUSIONS
We have discovered a set of small molecules that are selective
for only two HDAC isoforms belonging to distinct phylogeꢀ
netic classes. Our biochemical and computational data proꢀ
vide evidence that evolutionary relationships between HDACs
cannot always predict molecular recognition or ligand binding
similarities. Potency and selectivity for HDAC6 seems to be
driven by close contacts between the linking phenyl motif and
an optimal hydroxamic acid chelating geometry at the zinc
coordination center. The metaꢀsubstituents are primarily oriꢀ
ented towards solvent and play a marginal role in binding.
However, for HDAC8, potency and selectivity seem to be
strongly dependent on the presence of a hydrophobic metaꢀ
substituent binding in a wellꢀdefined secondary pocket. These
dual HDAC6/8ꢀselective inhibitors are active in cells, and the
results reported here will help guide future efforts towards
developing novel HDAC inhibitors with optimized selectivity
profiles.
Funding Sources
Funding was provided by the Stanley Medical Research Institute.
ACKNOWLEDGMENT
We would like to thank Dr. Stephen Johnston for analytiꢀ
cal/purification support and John McGrath for compound manꢀ
agement support. We also would like to thank Josh Ketterman for
help with cell culture experiments as well as Katherine Foley and
Anna McGlashen for assisting in synthetic chemistry efforts.
ABBREVIATIONS
HDACs, histone deacetylases; SAHA, SuberoylAnilide Hydroxꢀ
amic Acid; H3, Histone H3.
REFERENCES
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EXPERIMENTAL SECTION
Representative procedure for the synthesis of 3ꢀ10:
To a solution of 3ꢀ(methoxycarbonyl)benzoic acid (1.1 equiv)
in DMF (0.1 M) was sequentially added 1ꢀ
[Bis(dimethylamino)methylene]ꢀ1Hꢀ1,2,3ꢀtriazolo[4,5ꢀ
b]pyridinium 3ꢀoxid hexafluorophosphate (HATU) (1.5
equiv), N,Nꢀdiisopropylethylamine (3.0 equiv), and amine (1.0
equiv). The reaction was monitored by LCMS. After compleꢀ
tion, the reaction was quenched with saturated NaHCO3(aq) and
extracted with EtOAc. The organic extracts were washed with
water and then brine, dried over magnesium sulfate, filtered,
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3. (a) Park, S. Y.; Jun, J. A.; Jeong, K. J.; Heo, H. J.; Sohn, J. S.;
13. (a) Lee, J.ꢀY.; Koga, H.; Kawaguchi, Y.; Tang, W.; Wong, E.;
Gao, Y.ꢀS.; Pandey, U. B.; Lu, J.; Taylor, J. P.; Cuervo, A. M.; Yao,
T.ꢀP. HDAC6 Controls Autophagosome Maturation Essential for
Ubiquitinꢀselective Qualityꢀcontrol Autophagy. EMBO J. 2010, 29,
969ꢀ980. (b) Namdar, M.; Perez, G.; Ngo, L.; Marks, P. A. Selective
Inhibition of Histone Deacetylase 6 (HDAC6) Induces DNA Damage
and Sensitizes Transformed Cells to Anticancer Agents. Proc. Natl.
Acad. Sci. 2010, 107, 20003ꢀ20008
14. Wagner, F. F.; Olson, D. E.; Gale, J. P.; Kaya, T.; Weïwer, M.;
Aidoud, N.; Thomas, M.; Davoine, E. L.; Lemercier, B.; Zhang, Y.ꢀ
L.; Holson, E. B. Potent and Selective Inhibition of HDAC6 Does Not
Require a Surfaceꢀbinding Motif. J. Med. Chem. 2013, 56, 1772ꢀ
1776.
15. There have been limited reports of selective HDAC6 or
HDAC8 inhibitors that exhibit modest potency for HDAC8 or
HDAC6, respectively. See ref 11e as well as (a) Galletti, P.; Quintaꢀ
valla, A.; Ventrici, C.; Giannini, G.; Cabri, W.; Penco, S.; Gallo, G.;
Vincenti, S.; Giacomini, D. Azetidinones as Zincꢀbinding Groups to
Design Selective HDAC8 Inhibitors. Chem. Med. Chem. 2009, 4,
1991ꢀ2001. Additionally, HDAC3/6 dual inhibitors have been reportꢀ
ed (b) Kozikowski, A. P.; Tapadar, S.; Luchini, D. N.; Kim, K. H.;
Billadeau, D. D. Use of Nitrile Oxide Cycloaddition (NOC) Reaction
for Molecular Probe Generation: A New Class of Enzyme Selective
Histone Deacetylase Inhibitors (HDACIs) Showing Picomolar Activiꢀ
ty at HDAC6. J. Med. Chem. 2008, 51, 4370ꢀ4373.
16. We chose to measure inhibition of HDAC8 along with HDACs
2, 4, and 6 as representatives for class I, class IIa, and class IIb, reꢀ
spectively. We chose HDACs 2 and 4 due to the availability of crysꢀ
tal structures for these isoforms. Inhibition of HDAC10 and 11 was
not measured due to either low purity of the available recombinant
HDAC enzyme preparations and/or lack of activity of the enzymes
and low substrate conversion. See, Holson, E.; Wagner, F.; Weïwer,
M.; Zhang, Y.L.; Haggarty, S.H.; Tsai, L.H. Inhibitors of histone
deacetylases. WO2012149540 (A1); Nov 1, 2012.
Lee, H. Y.; Park, C. G.; Kang, J. Histone Deacetylases 1, 6 and 8 are
Critical for Invasion in Breast Cancer. Oncol. Rep. 2011, 25, 1677ꢀ
1681. (b) Acharya, M. R.; Sparreboom, A.; Venitz, J.; Figg, W. D.
Rational Development of Histone Deacetylase Inhibitors as Antiꢀ
cancer Agents: A Review. Mol. Pharmacol. 2005, 68, 917ꢀ932.
4. (a) Gray, S. G. Epigenetic Treatment of Neurological Disease
Epigenomics, 2011, 3, 431ꢀ450. (c) Graff, J.; Tsai, L.ꢀH. The Potential
of HDAC Inhibitors as Cognitive Enhancers. Annu. Rev. Pharmacol.
Toxicol. 2013, 53, 311ꢀ330.
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Beedle, A. S. Epigenetic Mechanisms that Underpin Metabolic and
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Mihaylova, M. M.; Vasquez, D. S.; Ravnskjaer, K.; Denechaud, P.ꢀ
D.; Yu, R. T.; Alvarez, J. G.; Downes, M.; Evans, R. M.; Montminy,
M.; Shaw, R. J. Class IIa Histone Deacetylases are Hormoneꢀ
activated Regulators of FOXO and Mammalian Glucose Homeostasis.
Cell 2011, 145, 607ꢀ621.
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mas. Leukemia 2008, 22, 1026.
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Compound 3 docked into HDACs 6 (A and C) and 8 (B and D). The enzymes in C and D are aligned,
demonstrating that 3 occupies distinct sub-pockets in HDAC6 and HDAC8
139x136mm (300 x 300 DPI)
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O
HDAC Isoform Inhibition
IC50 ( M)a
OH
R
N
H
6
7
8
Compound
2
4
6
8
R Group
1b
2b
3
7.9
± 0.10
>33
0.12
± 0.013 ± 0.36
1.9
9
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33
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H
N
0.61
± 0.035
>33
>33
>33
>33
>33
>33
>33
>33
14
0.004
± 0.0001 ± 0.14
1.2
Ph
Ph
O
O
9.0
± 6.6
0.036
± 0.018 ± 0.064
0.12
N
H
O
N
N
4
20
± 4.3
0.059
± 0.028 ± 0.18
0.42
H
O
Ph
N
5
11
± 1.6
0.034
± 0.014 ± 0.11
0.21
H
O
Ph
N
6
30
± 11
0.057
± 0.021 ± 0.047
0.11
H
O
Me
7
>33
>33
>33
2.5
± 1.6
14
± 10
N
H
Me
8
0.65
± 0.52
3.3
± 1.7
Ph
N
H
9
1.3
± 0.61
1.7
± 0.87
O
Ph
10
4.8
± 1.7
0.021
0.037
N
H
± 0.71 ± 0.002 ± 0.012
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HDAC Isoform Inhibition, IC50 ( M)a
Compound
SAHA
HDAC1
HDAC2
HDAC3
HDAC4
HDAC5
HDAC6
HDAC7
HDAC8
HDAC9
0.005
± 0.002
0.018
± 0.009
0.004
± 0.002
>33
11
0.002
>33
1.0
± 0.70
>33
± 4.6
± 0.001
3
12
± 2.0
9.0
± 6.6
23
± 10
>33
>33
0.036
13
± 1.7
0.12
± 0.064
>33
± 0.018
10
6.1
± 0.33
4.8
± 1.7
18
± 0.35
14
26
0.021
8.4
± 1.0
0.037
± 0.012
12
± 6.7
± 0.71
± 5.2
± 0.002
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Class
IC50 ( M)
9.0
HDAC
O
O
2
8
4
6
I
OH
N
N
I
0.12
H
H
IIa
IIb
>33
3
0.036
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HDAC1
HDAC2
HDAC3
HDAC8
HDAC11
HDAC6
HDAC10
HDAC4
HDAC5
HDAC7
Class I
Class IV
Class IIb
Class IIa
HDAC9
O
O
OH
N
OH
N
H
H
H
N
N
N
Me
LBH-589
Tubastatin A
HN
Me
O
O
H
N
NH
O
N
OH
H
N
O
N
NH2
OH
H
O
SAHA
MS-275
O
O
O
NH
MeO
NH2
Me
N
H
N
N
H
Compound 60
11 (PCI-34051)
S
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