S.-J. Lin et al. / Bioorg. Med. Chem. Lett. 14 (2004) 1173–1176
Table 1. Effects of 1–5 on fibril formation and neurotoxicitya
1175
b
c
TI (IC50/EC50)d
Compd
R
EC50 (mM)
IC50 (mM)
1
4-NH(CH
4-NMe
2
2-SMe, 4-NH
2
4-NHCH SO
4-NH
2
)
2
NEt
2
15.11Æ5.15
12.89Æ0.83
56.79Æ7.79
77.23Æ9.35
>100
22.14Æ3.01
>100
>100
1.47
>7.75
>1.76
2
3
4
5
(LB-152)
2
3
Na
>100
>100
>1.29
no suppression
2
a
b
c
All data are presented as average values from three separate experiments.
Effect on fibril formation; concentration which inhibits wild type aggregation by 50%.
Neurotoxicity; concentration which inhibits viability of neurons by 50%.
d
Therapeutic index, TI=IC50/EC50
.
ꢀ
with MTT at 37 C for 1 h, the medium was removed
and the formazan particles were dissolved with DMSO.
OD600 nm was measured by ELISA reader. The ther-
apeutic index of these compounds was determined as
follows. (1) Ab40 aggregation inhibitory activity was
determined using ThT binding assay at various con-
centrations of compounds and the EC50 values were
calculated. (2) Neurotoxicity was determined using the
MTT reduction assay at various concentrations of
compounds and the IC50 values were calculated. (3) The
therapeutic activity was determined as therapeutic index
p-N,N-dimethylamino substituted LB-152 possessed the
highest Ab40 aggregation inhibitory activity without
inducing neurotoxicity.
Inhibition of Ab40 aggregation and reduction in neuro-
toxicity are expected to slow down or to arrest the pro-
gress of AD, as well as to prevent the earliest form of Ab
deposition. As mentioned earlier, one of the challenges in
developing new inhibitors is to find nontoxic, non-peptide
small-molecule lead compounds that can cross the BBB.
Our studies have identified LB-152 as a useful lead
compound for future design of promising clinical trials
candidates for prevention and/or retardation of amylo-
idogenesis involved in the development of AD. A more
detailed analysis of the profile of LB-152 as a potent
b-amyloid aggregation inhibitor for treatment of AD
will be presented in due course.
(
TI, IC /EC ). The reference compound 1 was included
50 50
during each bioassay for comparison. Data are pre-
sented in Table 1.
1
1
As shown in Table 1, we successfully identified novel
small-molecule inhibitors for inhibition of Ab40 aggre-
gates. The present structure–activity relationships (SAR)
demonstrate that modification on the end of the phenyl-
azo moiety at the para-position with different amino
substituents results in significant effects on the Ab40
aggregation inhibitory activity and neurotoxicity.
Results of these SAR conclusions are discussed below.
Acknowledgements
We gratefully thank the National Science Council of
Republic of China grants NSC-89-2314-B-077-013
(L.-M.Y.) and NSC-92-2320-B-038-040 (S.-J.L.) and the
(
i) A simple phenylazo-like structure afforded good
National Research Institute of Chinese Medicine for
providing financial support.
activity. (ii) None of the trans-stilbene benzenesulfon-
amide derivatives displayed Ab40 aggregation inhibitory
activity (data not shown). (iii) Replacing the 4-(2-N,N-
diethylamino-ethylamino)-naphthylamino moiety in 1
with a p-N,N-dimethylamino-phenylazo group in 2 (LB-
References and notes
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0
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0
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