Design, synthesis and antitumor activity of non-camptothecin topoisomerase i inhibitors

Article abstract of DOI:10.1016/j.bmcl.2015.06.042

Three groups of non-camptothecin compounds with four to five fused rings have been designed and synthesized. Their in vitro anti-proliferative activity has been evaluated with five different cancer cell lines (HCT116, PC3, U87MG, HepG2, SK-OV-3). Compound

Full text of DOI:10.1016/j.bmcl.2015.06.042

Accepted Manuscript
Design, synthesis and antitumor activity of non-camptothecin topoisomerase I
inhibitors
Chao Zhang, Shasha Li, Liyan Ji, Shan Liu, Zhongjun Li, Shuchun Li, Xiangbao
Meng
PII:
S0960-894X(15)00635-6
DOI:
http://dx.doi.org/10.1016/j.bmcl.2015.06.042
BMCL 22832
Reference:
Bioorganic & Medicinal Chemistry Letters
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Revised Date:
Accepted Date:
26 February 2015
27 May 2015
10 June 2015
Please cite this article as: Zhang, C., Li, S., Ji, L., Liu, S., Li, Z., Li, S., Meng, X., Design, synthesis and antitumor
activity of non-camptothecin topoisomerase I inhibitors, Bioorganic & Medicinal Chemistry Letters (2015), doi:
http://dx.doi.org/10.1016/j.bmcl.2015.06.042
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Design, Synthesis and antitumor activity of
non-camptothecin topoisomerase I inhibitors
Leave this area blank for abstract info.
Chao Zhang, Shasha Li, LiyanJi, Shan Liu, Zhongjun Li,
Shuchun Li, Xiangbao Meng
N
O
n
OH
N
Cmpd.
IC50
(
M)
µ
HepG2 SK-OV-3
HCT116 PC3 U87MG
B-2
B-3
0.1694
0.3249
1.010
0.7829
0.7064 0.3889
0.9956 0.6119
0.8443
1.974
O
B-2,3
n= 2,3
Compounds B-2 and B-3 exhibit the most potent activity against U87MG cell growth with IC50 of 169 nM and 325 nM, respectively.
1

Bioorganic & Medicinal Chemistry Letters
journal homepage: www.els evier.com
Design, synthesis and antitumor activity of non-camptothecin topoisomerase I
inhibitors
Chao Zhang, Shasha Li, Liyan Ji, Shan Liu, Zhongjun Li, Shuchun Li*, and Xiangbao Meng*
State Key Laboratory of Natural and Biomimetic Drugs; Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing
100191, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Three groups of non-camptothecin compounds with four to five fused rings have been
designed and synthesized. Their in vitro anti-proliferative activity has been evaluated with
five different cancer cell lines (HCT116, PC3, U87MG, HepG2, SK-OV-3). Compound B-
2 and B-3 showed the most potent cell growth inhibition with IC50 of 169 nM and 325 nM
against U87MG cell line correspondingly.
Revised
Accepted
Available online
2015 Elsevier Ltd. All rights reserved
.
Keywords:
anti-cancer
Topo I
synthesis
inhibitor
DNA topoisomerases (Top) are well documented targets for anti-
cancer drug development. 1 There are two sub family of Top: type I
(Top1) and type II (Top2) depending on whether they cleave single
or double strands of DNA.2 Top1 can relax supercoiled DNA by
breaking and re-connecting single-strand to control DNA
replication.2 These agents reversibly block Top1-mediated cleavage
of DNA complex, leading to DNA strand breaks, which eventually
lead to the cell cycle arrest and activation of apoptosis2 Top1
inhibitors are broadly used in clinic as chemotherapeutic agents.
expected to show Top I inhibitory activities.
Camptothecin(CPT)3 was the first small molecule identified as a
Top1 inhibitor. Efforts to lower its toxicity and pharmacokinetic
profiles led to the development of two CPT derivatives, topotecan
and irinotecan with improved water solubility.45 Both compounds are
current chemotherapeutic agents in clinic for ovarian cancer and
colorectal cancer treatment. However, CPTs derivatives have several
limitations including chemical instability6 and subsequent
resistance.7 To overcome the main drawbacks of CPTs, several
classes of non-CPT scaffold Top1 inhibitors were developed as new
anti-cancer drug candidates.5,8,9
As our ongoing investigations in the development of Top inhibitors,
we have recently studied the in vitro and in vivo anti-cancer activity
of novel triazolonaphthalimide derivatives.10 In this study, we fused
the structure characteristics of triazolonaphthalimideand CPT to
design and synthesize three series of CPT mimics(Fig.1), which were
Figure 1. Structures of camptothecin, topotecan, irinotecan and
designed CPT mimics
These compounds share the [6,6,5,6] fused aromatic structures that
have been reported to be critical for the anti-cancer activities5,8,9. In
addition, several parental core scaffolds including ninhydrin, 10 1,4-
*Corresponding Author: Tel.: 86-10-82801714;
E-mail addresses: xbmeng@bjmu.edu.cn

11
12
Scheme 1. Synthesis of naphthoquinone-based compounds. (a)
toluene, Zn(OTf)2, rt. (b) Pd(TFA)2, CH3COOH, reflux (c) EtOH, rt.
naphthoquinone,
indazolo[1,2- b]phthalazine
2-hydroxy-1,4- naphthoquinone
13
as well as
structures were all proved to be
important for the anti-cancer activity.
Series C compounds were prepared via a three-component reaction.
Compound C-1 was synthesized from chemical blocks including 2,
3-dihydrophthalazine-1,4-dione, cyclohexane-1,3-dione, and ethyl 2-
oxoacetate via a previous reported reaction.22 To further improve the
conjugation of these compounds, we further oxidized compound C-1
to afford C-2 with bromide substitution on the benzene ring.23 The
bromide atom could be easily removed by catalytic hydrogenation in
the presence of 2eq AcOH to afford C-3. Ester C-2 or C-3 could
react with primary amine to afford the corresponding amide C-4 and
C-5 (Scheme 2).24
Herein, we designed and synthesized three series of coplanar
tetracyclic or pentacylic aromatic compounds which mimic the
molecular shape of CPTs as shown in red(Fig. 1).
To synthesize target compounds, various synthetic routes have been
proposed and carried out. The procedure to synthesize series A
compounds was based on the reaction of ninhydrin and substituted
ortho-phenylenediamine in methanol under reflux,15 which was
described in Table 1. Due to the unsymmetrical substituent groups of
ortho-phenylenediamine derivatives, the reaction produces two
regioisomers. Some structures of them, including A-2 to A-4, and A-
9, have been reported in the literature.16, 17, 18 While other compounds
likeA-5 to A-8 have not been reported. Therefore, we isolated each
regioisomer via silica gel chromatography. Compounds A-10 and A-
11 showed similar melting point to previous report.19 Michael
addition of anisidine to naphthoquinone catalyzed by zinc triflate
was carried out in refluxing toluene, then the product was cyclized to
form tetracyclic aromatic compound B-2,20 The third type reaction
was adopted from previously published literature, which went on a
series of tandem reactions to get compound B-3 and B-4.21
Table 1. Synthesis of Series A compounds:Indanones derivatives
O
O
N
R1
R2
NH2
NH2
OH
OH
MeOH
reflux
+
B
N
R1
A
A
B
O
R2
Scheme 2. Synthesis of indazolo[1,2-b]phthalazine derivatives. (a)
H2SO4, EtOH/H2O, 80oC. (b) Br2, CH3CN, 80 oC. (c) a,b: EtOH,
80oC; c,d: n-butanol,120oC.
NO.
yeild(%)
note
A
R1
R2
B
C
C
C
C
92
80
A-1
A-2
H
H
H
CH3
C
C
C
C
CH3
F
A-3
A-4
CH3
CH3
61
60
The cytotoxicity of these compounds against five cancer cell lines
including HCT-116 (colorectal carcinoma), PC-3 (prostate
carcinoma), U87MG (brain tumor), HepG2 (liver cancer), SK-OV-3
(ovarian cancer) were determined with the in vitro cell proliferation
assay (Table 2). For series A and C compounds, most of them
shows moderate inhibitory activity except for A-11 that significantly
inhibited HCT-116, PC3 and HepG2 cell proliferation at 10µM. In
addition, compound B-1 with similar scaffold also show better
activity against these cell lines. But to our surprise, compounds B-2
and B-3 display potent inhibitory activity to almost all these cancer
cell lines. Later literature search revealed that compounds with
similar structures have been reported. 25, 26
C
C
C
C
C
C
C
C
C
C
H or CF3
CF3 or H
H or OMe
OMe or H
CF3 or H
H or CF3
A-5
A-6
A-7
A-8
A-9
a
17
25
11
11
73
b
a
OMe or H
H or OMe
b
N or C
C or N
C or N
N or C
H
H
A-10
A-11
a
b
H
H
36
21
Table 2. Cytotoxicity of compounds series A, B, and C (10 µM)a
a：the upper substance in TLC(MeOH: CH2Cl2=10:1)
b: the lower substance in TLC(MeOH: CH2Cl2=10:1)
3

Figure 2. Top I inhibitory evaluation of compounds B-2 and B-3 (50µM,
respectively) and CPT (saturated in 0.1% DMSO in water)
Inhibition rate%
U87MG
Compd
SK-
OV-3
HCT116
PC3
HepG2
Docking study was also conducted to help us get a full image of the
interaction between B-2 and Topo I. The docking result shows that
carbonyl group can form hydrogen bond with ASN722, and the
hydroxyl group can form hydrogen bond with ARG364 and TGP11
from up and down simultaneously, thus the planar structure of B3
can be steadily embedded into the topotecan binding pocket of
topoisomerase I.
-1.83%
6.32%
-8.39%
-8.92%
2.65%
-14.46%
-13.91%
-13.22%
-7.67%
-15.57%
-7.74%
-14.45%
-11.50%
-23.26%
20.83%
49.00%
78.78%
86.04%
1.50%
53.19%
6.44%
10.09%
11.20%
9.60%
A-1
A-2
22.68%
12.21%
17.21%
16.94%
8.68%
50.45%
42.85%
43.82%
6.56%
A-4
-1.15%
15.94%
-1.15%
-4.44%
11.75%
36.17%
52.66%
8.56%
-0.82%
14.17%
-7.19%
8.07%
A-5
A-6
A-7
14.70%
2.82%
A-8
7.32%
-8.16%
2.89%
A-9
1.49%
15.18%
55.42%
26.59%
88.15%
87.96%
12.00%
2.54%
A-10
A-11
B-1
13.15%
57.57%
82.42%
77.43%
-4.89%
-3.43%
-3.97%
-6.16%
-4.10%
-4.34%
-4.25%
-1.46%
-4.01%
-7.14%
-5.15%
-2.88%
71.92%
76.15%
92.03%
91.23%
3.50%
B-2
66.46%
59.57%
11.10%
0.80%
B-3
C-1
3.30%
4.10%
C-2
0.40%
4.90%
1.90%
11.25%
3.89%
C-3
-5.80%
-5.70%
3.70%
14.30%
6.40%
0.10%
C-4a
C-4b
C-4c
C-4d
C-5a
C-5b
C-5c
C-5d
C-6
-2.50%
0.40%
-7.99%
15.06%
-8.92%
-2.82%
-8.92%
-0.87%
-3.15%
9.65%
6.50%
5.40%
5.30%
-4.70%
1.10%
-4.20%
-4.50%
-0.60%
-3.80%
7.50%
4.00%
11.10%
5.00%
-4.70%
-0.60%
2.40%
Figure 3. Docking study between compound B-2 and Topo I
7.60%
In conclusion, we have synthesized three series of coplanar aromatic
compounds and evaluated their cytotoxicity against five different
cancer cell lines. We also tested identified compounds for their Top I
inhibitory activity. Both B-2 and B-3 show potent anti-proliferative
effects by inhibiting Top I. B-2 and B-3 would be promising non-
CPT structure anticancer agents which merit further investigation.
5.20%
3.60%
a. Mean inhibitory rate of the triplicate experiment.
Based on the screening results, we further examined the IC50 values
of compound A-11, B-2 and B-3(Table 3). Compounds B-2 and B-3
showed IC50 values in sub-micromolar level. Both of the compounds
share similar side amine chains which are considered to be the key
moiety when interacting with negatively charged DNA double
strands to fully exert their biological effects.
Acknowledgments
This work was financially supported by the National Natural
Science Foundation of China (NSFC No. 81273370).
Table 3.IC50 values of selected compounds over five cancer cell lines.a
IC50 (µM)
Compound
HCT116
44.57
PC3
U87MG HepG2 SK-OV-3
References and notes
A-11
B-2
4.377
/
33.80
0.8443
1.974
/
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5

Table 1. Synthesis of Series A compounds: Indanones derivatives
Yield
NO.
A
B
R1
R2
note
(%)
92
80
61
60
A-1
A-1
A-3
A-4
C
C
C
C
C
C
C
C
H
H
H
CH3
CH3
CH3
CH3
F
CF3 or
H
H or
CF3
A-5
A-6
A-7
A-8
C
C
C
C
C
C
C
C
17
25
11
11
a
b
a
b
H or
CF3
CF3 or
H
OMe
or H
H or
OMe
H or
OMe
OMe
or H
A-9
C
C
73
a
N or C or
A-10
A-11
H
H
H
H
36
21
b
a
C
C or N or
N
N
C
a：the upper substance in TLC (MeOH: CH2Cl2=10:1)
b : the lower substance in TLC (MeOH: CH2Cl2=10:1)
6