Repurposing human Aurora kinase inhibitors as leads for anti-protozoan drug discovery

Article abstract of DOI:10.1039/c4md00045e

Hesperadin, an established human Aurora B inhibitor, was tested against cultures of Trypanosoma brucei, Leishmania major, and Plasmodium falciparum, and was identified to be a potent proliferation inhibitor. A series of analogs was designed and tested to

Full text of DOI:10.1039/c4md00045e

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Repurposing human Aurora kinase inhibitors as
leads for anti-protozoan drug discovery†
Cite this: DOI: 10.1039/c4md00045e
Gautam Patel,a Norma E. Roncal,b Patricia J. Lee,b Susan E. Leed,b Jessey Erath,d
b
a
Ana Rodriguez,cd Richard J. Sciotti and Michael P. Pollastri
*
Hesperadin, an established human Aurora B inhibitor, was tested against cultures of Trypanosoma brucei,
Leishmania major, and Plasmodium falciparum, and was identified to be a potent proliferation inhibitor. A
series of analogs was designed and tested to establish the initial structure–activity relationships for each
parasite. In this study, we identified multiple non-toxic compounds with high potency against T. brucei
and P. falciparum with good selectivity. These compounds may represent an opportunity for continued
optimization.
Received 5th February 2014
Accepted 17th Mar 2014
DOI: 10.1039/c4md00045e
www.rsc.org/medchemcomm
accelerated by considering the previous SAR developed for the
chemotype.
Introduction
Aurora kinases are central enzymes in cellular division, and
have been the focus of drug discovery efforts in oncology,
resulting in multiple inhibitors advanced into clinical trials.
Both L. major11 (which causes cutaneous leishmaniasis) and P.
falciparum12 express Aurora kinases, and established inhibitors
of Aurora have been shown to be effective cell proliferation
inhibitors for Trypanosoma brucei including hesperadin (1),13
VX-680 (2)14 and danusertib (3).4
Encouraged by the preliminary results for T. brucei described
above, we assessed these three human Aurora kinase inhibitors
against other pathogens: L. major (promastigote and intracel-
lular amastigote forms), and the D6 strain of P. falciparum
(Table 1). We also tested 1 against the intracellular amastigote
form of T. cruzi, the causative agent of Chagas disease. We
counter-screened against the hepatic cancer cell line (HepG2) as
a general surrogate for host cell toxicity. We observed a range of
potencies, and note that 1 displayed a potent growth inhibitory
phenotype against P. falciparum and L. major parasites, though
host cell toxicity was apparent. In light of these results, we opted
to focus on further exploration of the SAR of this chemotype as a
potential antiparasitic agent.
Neglected tropical diseases (NTDs) are a collection of debili-
tating infectious diseases that typically affect the poorest pop-
ulations in the world, such as human African trypanosomiasis
(caused by Trypanosoma brucei), leishmaniasis (caused by
Leishmania sp.), and Chagas disease (T. cruzi). When taken
together with malaria (caused by Plasmodium sp.), these
diseases have a signicant and adverse effect on length of
quality of life, estimated in 2011 to be over 60 million disability-
adjusted life-years.1 Drug discovery for these diseases is cost
limited, given that the vast majority of patients cannot pay for
treatment. Therefore, pragmatic and cost effective methods for
drug discovery are needed.
One such method is target repurposing,2 where essential
parasitic targets (such as kinases,3–7 phosphodiesterases,8,9 and
histone deacetylases10) are matched with homologous and
druggable targets in humans that have been the subject of
previous drug discovery programs. Assessment of chemical
matter identied in those programs against the infectious
pathogen can oen result in identication of new leads for the
infectious disease. Furthermore, the medicinal chemistry opti-
mization against the pathogen can be facilitated and
aNortheastern University Department of Chemistry
& Chemical Biology, 360 Synthetic strategy
Huntington Avenue, Boston, MA, USA. E-mail: m.pollastri@neu.edu; Tel: +1
We designed a synthetic strategy to access three regions of the
hesperadin molecule, labelled R1–R4 as shown in Table 1,
modelled aer the synthetic route described in a patent.15
617-373-2703
bExperimental Therapeutics, Walter Reed Army Institute for Research, 2460 Linden
Lane, Silver Spring, MD, 20910, USA
cNew York University School of Medicine, Department of Microbiology, Division of Synthesis initiated with indolone 4, which was nitrated15 and
Parasitology, 341 E. 25th St., New York, NY, USA
condensed with methyl orthobenzoate to provide 6. Displace-
dAnti-Infectives Screening Core, New York University School of Medicine, New York, NY
ment of the vinylogous ester, nitro group reduction, and sul-
10010, USA
fonylation with a small set of sulfonyl chlorides afforded the R1
† Electronic supplementary information (ESI) available: Synthetic preparations
analogs 11 following N-deprotection (Table 2). The nitro-
and assay details are described in the ESI. See DOI: 10.1039/c4md00045e.
indolone 5 could be converted to the sulfonamide 12, which was
subjected to a similar sequence as above with varied amine
Compound data is available as
http://collaborativedrug.com
a
searchable shared data set at
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Table 1 Benchmark screening of human Aurora inhibitorsa
TC50 (mM)
EC50 (mM)
L. major
L. major
Compound
T brucei
T. cruzi
promastig
amastig
P. falciparum
HepG2
1
2
3
0.0613
1014
39
nt
nt
0.12
>21
>21
2.37
nt
nt
0.01
0.838
0.857
<0.2
3.3
4
0.64
a
nt ¼ not tested; all EC50 and TC50 values data are averages of three replicate experiments.
Table 2 Potency of analogs of 1 against three protozoan parasites
EC50 (mM)
TC50 (mM)
L. major
promastig
L. major
amastig
Cmpd
R1
R2
R3
R4
T brucei
T. cruzi
P. falciparum
HepG2
1
7a
7b
8
NHSO2Et
H
NO2
NH2
NH2
NHSO2Me
NHSO2Ph
NHAc
NHSO2Et
NHSO2Et
NHSO2Et
NHSO2Et
H
H
Ac
Ac
H
H
H
H
H
H
H
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
H
0.06
0.07
0.13
3.25
1.16
0.02
0.01
0.15
1.32
3.36
1.79
1.67
39
25
3
45
>50
>50
16
>50
>50
>50
>50
>50
0.12
0.77
1.08
>4
0.79
0.39
0.85
1.52
2.77
>4
2.37
>4
2.04
>4
>4
>4
1.91
>4
>4
>4
>4
0.01
<0.2
>6.0
>6.0
1.81
>6.0
0.2
3.29
>6.0
5
0.230
0.275
0.218
0.199
0.052
0.107
0.068
0.241
1.364
0.233
0.167
10
11a
11b
11c
17a
17b
17c
17d
Me
Et
n-Bu
>6.0
>6.0
>6.0
2.8
2.6
>4
15a
NHSO2Et
H
Ph
>50
>50
>4
>4
>15
>10.0
15b
15c
NHSO2Et
NHSO2Et
H
H
Ph
Ph
Ph
p-Tol
1.44
0.37
>50
>50
>4
2.6
>4
>4
0.109
1.607
4.7
3.1
15d
15e
NHSO2Et
NHSO2Et
H
H
Ph
Ph
0.1
>50
>50
0.94
0.62
1.68
>4
0.054
0.595
1.31
>6.0
1.53
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nucleophiles (to vary R4) to obtain access the analogs 15 HepG2 cells, maintaining some selectivity. The results in our
following deprotection. Finally, inclusion of various orthoester data set suggest the requirement for a basic nitrogen, noting
reagents in the sequence afforded R3 variations (compound 17) also that reduction in basicity (e.g. morpholino group) results in
(Scheme 1).
loss of potency. Removal of the methylene spacer (15e) caused a
strongly adverse effect on potency against all pathogens, as does
removal of the piperidinyl moiety altogether (15c). Though the
phenyl analog (15b) shows diminished potency against P. fal-
ciparum, the selectivity over HepG2 cells is in excess of 50-fold.
Finally, removal of the intervening aromatic group (15a) results
in complete loss of activity across parasites.
Screening results and discussion
The analogs were tested in parasite cultures, and the results are
summarized in Table 2. First, variation of the R1 position (Table
2) revealed a preference for the ethyl sulfonamide moiety
present in 1 over the methyl (11a) or phenyl sulfonamide (11b)
or replacement with an acetamide (11c). However, 11c afforded
reduced potency against HepG2 cells, providing improvement
in cellular selectivity over the other analogs. Complete removal
of the R1 functionality (7a) led to a signicant reduction in
antimalarial and anti-leishmanial activity, though 7a was
equipotent to 1 against T. brucei and selective over HepG2 cells.
The free amine (10) showed marked reduction in activity across
pathogens.
Finally, survey of the R3 phenyl of 1 conrms that replace-
ments with H (17a) or small alkyl chains (17b–d) has a detri-
mental effect on activities compared to 1. Interestingly, the
methyl analog (17b) is far less potent than the others, which are
all in a range of ꢀ20 fold less potent than 1, with diminished
HepG2 activity. Notably, none of the compounds tested showed
appreciable activity against T. cruzi.
Drug resistance is a signicant issue for malaria. We therefore
opted to test our analogs across three additional strains of P.
falciparum besides the drug-sensitive D6 strain: W2 (chloroquine
resistant), C235 (chloroquine, meoquine and pyrimethamine
In variation of the R4 substituent, substitution of oxygen for
carbon of the piperidine ring of 1 provides a slight reduction in
antiprotozoan activity (15d), though activity was also reduced in
Scheme 1 Synthesis of analogs of hesperadin (1). Reagents and conditions. (a) HNO3, H2SO4 ꢁ15 ꢂC; (b) PhC(OCH3)3, Ac2O; (c) 4-(piperidin-1-
ylmethyl)aniline, DMF; (d) Zn, NH4Cl, MeOH, H2O; (e) RSO2Cl, Et3N, DMF; (f) NaOH, MeOH; (g) EtSO2Cl, Et3N, DMF; (h) R–NH2, DMF; (i)
RC(OCH3)3, Ac2O.
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Notes and references
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Fig. 1 Plot of EC50 values of P. falciparum C235 versus D6 strains.
R2 ¼ 0.99.
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resistance). The data is tabulated in the ESI,† but is presented in
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Conclusions
In summary, we have identied analogs of 1, an established
human Aurora kinase inhibitor, that display modest-to-excel-
lent potency against the protozoan pathogens that cause African
sleeping sickness, malaria, and leishmaniasis. Importantly,
these compounds are not acting as general cell toxins, as we
have observed varying margins of selectivity. Notably, we have
also found that these compounds show broad utility as equi-
potent inhibitors of a range of drug resistant strains of malaria.
Though these compounds have not yet been tested against
Aurora kinase homologs in the respective parasites, we expect
that this will be a useful place to begin to identify molecular
mechanisms of action.11–13 This, along with our ongoing opti-
mization of this chemotype against these pathogens, will be
reported in due course.
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M. Lenter, M. J. C. A. Van, W. Spevak and U. Weyer-
Czernilofsky, WO2002036564A1, 2002.
Acknowledgements
We thank Professor Larry Ruben (Southern Methodist Univer-
sity) for helpful discussion and comments on this manuscript. 16 G. De Muylder, K. K. H. Ang, S. Chen, M. R. Arkin, J. C. Engel
This work was funded in part by NIH R01AI082577 (MPP). We
and J. H. McKerrow, PLoS Neglected Trop. Dis., 2011, 5, e1253.
Med. Chem. Commun.
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