L. Hu et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7547–7550
7549
Table 2
Anti-tumor efficacy of compounds 7h, 7k, 7r and 7ya against non-small cell lung cancer A549 xenografts in nude mice
Group
Dosage (mg/kg)
Mice (n)
Body weight (g)
Tumor volume (mm3) X SD
Relative TV (X SD)
Inhibition rate (%)
Initial/end
Initial/end
Initial
End
NS
7h
7k
7r
7y
NVB
—
9
9
9
9
9
6/6
6/6
6/6
6/6
6/5
6/6
26.03/27.61
25.10/26.53
25.00/24.60
25.02/25.32
25.13/25.45
25.92/26.22
262.75 15.42
258.04 22.92
259.30 5.63
260.15 5.89
260.46 18.87
262.76 24.79
1341.72 71.26
1057.20 27.33
750.34 96.01
766.08 22.15
797.27 38.56
743.91 48.82
5.17 0.21
4.24 0.34
2.92 0.12
2.91 0.21
3.00 0.31
2.89 0.17
17.99*
43.52*
43.71*
58.02*
55.90
a
The in vivo experiment was carried out in the nude mice bearing A549 xenografts and the compounds were intravenously given. Ditartrate of all compounds was used in
bioassays.
*
P < 0.01 versus control group.
The series of C-22 amide vinorelbine analogues were evaluated
for their antiproliferative activity in human non-small-cell lung
cancer (A549 cell) using the MTT cell viability assay,12 vinorelbine
1d was employed as standard for comparison purposes. The IC50
values for the inhibition of proliferation of the A549 cell line were
shown in Table 1.
Based on the in vitro activity, four C-22 amide vinorelbine ana-
logues (7h, 7k, 7r and 7y) were selected and tested further for their
antitumor efficacy in vivo. These three analogues were adminis-
tered by giving three doses intravenously (iv) once every seven
days (q7d ꢁ 3) at the doses of 9 mg/kg in nude mice bearing
A549 xenografts in comparison with NVB, and the results of the
in vivo study were summarized in Table 2.
Encouragingly, two compounds 7a and 7k, which were initially
synthesized for a preliminary prediction, showed desired potency
against A549 cell (IC50 = 24.5 and 6.0 nM, respectively) compared
to positive control NVB (IC50 = 9.0 nM). This result clearly indicated
that it was possible to improve the cytotoxicity by introducing dif-
ferent alkyl/aryl substituted amide groups. So, we first attempted
to study the alkyl-substituted effects on cytotoxicity, and the
results showed that the propionylamine compound 7b exhibited
an acceptable potency against A549 cell (IC50 = 15.6 nM), while
decreasing and/or increasing length of linear alkyl chains within
2, 4 and 5 carbons length showed decreased cytotoxic activity
(IC50 = 24.5, 17.3 and 22.1 nM, corresponding to 7a, 7c and 7d).
When the acetoxy at C-4 site of 7b was replaced with propionyloxy
to afford compound 7i (IC50 = 12.0 nM), an improved potency
against A549 cell was observed compared to 7b. Moreover, increas-
ing the steric hindrance of the substituent at the C-22 position led
to a gradual decrease in the cytotoxicity of the A549 cell line
(IC50 = 11.4, 22.0 and 37.0 nM, corresponding to 7e–7g). Particu-
larly, the cyclopropane carboxamide compound 7h was found to
be 3 times more potent against the A549 cell line (IC50 = 3.0 nM)
compared to the positive control NVB (IC50 = 9.0 nM), while all
the other alkyl-substituted analogues (7a–7g and 7i) displayed less
inhibitory potency than the positive control NVB.
As shown in Table 2, compounds 7y, 7k, and 7r showed compa-
rable or slightly lower antitumor activities in vivo (Inhibition
rate = 58.02, 43.52 and 43.71%, respectively) compared to the posi-
tive control NVB (Inhibition rate = 55.90%), while the compound 7h
displayed drastically reduced antitumor activity (Inhibition
rate = 17.99%). At the same time, compound 7y showed higher tox-
icity than that of NVB, for example, one mice died when treated
with 7y during the administration period. Generally, the amide
groups substituted at C-22 site have great influence on the antitu-
mor activity in vivo.
In conclusion, a series of C-22 amide vinorelbine analogues
(7a–7z) were designed, synthesized and evaluated for their anti-
proliferative activity in human non-small-cell lung cancer (A549
cell). The SAR information collected so far suggested that differ-
ent alkyl-substitution and aryl-substitution at the 22-position
had important influence on cytotoxic activity. Compounds 7h,
7k, 7r and 7y exhibited enhanced cytotoxic activities against
A549 cell line. The preliminary antitumor studies in vivo
indicated that 7y showed comparable activities compared to
the parent NVB.
Acknowledgments
Building on the result that the benzamide compound 7k
(IC50 = 6.0 nM) exhibited enhanced activity toward A549 cell com-
pared to NVB, we next turned our attention to study the substitu-
ent effects on the phenyl ring by introducing different substituents
at various positions and using benzyl and heteroaryl rings. The re-
sults showed that introduction of electron withdrawing [2/3/4-F,
2,6-(F)2] (IC50 = 6.6, 7.3, 7.1 and 7.9 nM, corresponding to 7n–7q)
or electron donating [2/3-OMe, 3,4-(OMe)2] (IC50 = 6.1, 6.1, 6.3
and 6.5 nM, corresponding to 7r–7u) groups on the phenyl group
showed retained potency against A549 cell compared to benzam-
ide compound 7k, while introduction of electron withdrawing (4-
Cl, 4-CF3, 4-NO2) (IC50 = 25.6, 20.7 and 40.1 nM, corresponding to
7v–7x) or electron donating (3/4-Me) (IC50 = 15.3 and 17.2 nM,
corresponding to 7l and 7k) groups on the phenyl ring showed sig-
nificantly decreased potency. In addition, no distinct effect on cyto-
toxic activity against the A549 cell was observed due to the
positions of F or OMe in the phenyl ring (7n–7u). The electron-rich
heteroaryl amide compounds 7y–7z (IC50 = 3.2 and 8.1 nM) dis-
played better potency against A549 than positive control NVB,
whereas the benzyl-substituted derivative 7j (IC50 = 16.2 nM) had
less potency. These results indicated that aryl substituents were
more suitable than benzyl substituent to maintain the potent cyto-
toxic activities.
This work was supported by the National Natural Science
Foundation of China (grants 30925040, 81102329, 81273430),
the Chinese National Science & Technology Major Project ‘Key
New Drug Creation and Manufacturing Program’ (grants
2012ZX09301001-001, 2011ZX09307-002-03), and the Science
Foundation of Shanghai (grant 12XD14057).
Supplementary data
Supplementary data associated with this article can be found,
References and notes
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