Macrocyclic BACE-1 inhibitors acutely reduce Aβ in brain after po application

Article abstract of DOI:10.1016/j.bmcl.2009.11.092

A series of macrocyclic peptidic BACE-1 inhibitors was designed. While potency on BACE-1 was rather high, the first set of compounds showed poor brain permeation and high efflux in the MDRI-MDCK assay. The replacement of the secondary benzylamino group wi

Full text of DOI:10.1016/j.bmcl.2009.11.092

Bioorganic & Medicinal Chemistry Letters 20 (2010) 603–607
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Macrocyclic BACE-1 inhibitors acutely reduce Ab in brain after po application
*
Andreas Lerchner , Rainer Machauer, Claudia Betschart, Siem Veenstra, Heinrich Rueeger, Clive McCarthy,
Marina Tintelnot-Blomley, Anne-Lise Jaton, Sabine Rabe, Sandrine Desrayaud, Albert Enz,
Matthias Staufenbiel, Paolo Paganetti, Jean-Michel Rondeau, Ulf Neumann
Novartis Institutes for BioMedicalResearch, Novartis Pharma AG, PO Box, CH 4002, Basel, Switzerland
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of macrocyclic peptidic BACE-1 inhibitors was designed. While potency on BACE-1 was rather
high, the first set of compounds showed poor brain permeation and high efflux in the MDRI–MDCK assay.
The replacement of the secondary benzylamino group with a phenylcyclopropylamino group maintained
potency on BACE-1, while P-glycoprotein-mediated efflux was significantly reduced and brain perme-
ation improved. Several compounds from this series demonstrated acute reduction of Ab in human
APP-wildtype transgenic (APP51/16) mice after oral administration.
Received 8 October 2009
Revised 13 November 2009
Accepted 17 November 2009
Available online 22 November 2009
Keywords:
Ó 2009 Elsevier Ltd. All rights reserved.
Alzheimer’s disease
BACE-1 inhibitors
MDR1–MDCK
P-Glycoprotein
Reduction of Abeta in transgenic APP51/16
mice
Deposition of amyloid plaques, mainly consisting of 40/42 ami-
no acid b-amyloid peptides, is a pathological hallmark of Alzhei-
mer’s Disease (AD). The consecutive action of Beta-site APP
tidic character was expected to have better permeability properties
than 1. Previous in vivo studies with macrocyclic BACE-1 inhibitors
have shown that the transporter P-glycoprotein (P-gP) in the blood
brain barrier considerably limits brain exposure, significant brain
levels were achieved either by co-administration of the P-gP-inhib-
itor PSC833 (Valspodar™), or in P-gP knock-out mice.8 Similar re-
sults were reported by others.9,10 We aimed to identify potent
BACE-1 inhibitors with improved BBB permeability, including lim-
ited P-gP mediated efflux. To assess the extent of P-gP efflux on
BBB permeability, the well-established in vitro model of Madin
Darby canine kidney cells over-expressing the human form of P-
gP (MDR1–MDCK) was used.11 The efflux ratio in this assay is de-
fined as the ratio between the basolateral-to-apical (BL–AP) trans-
fer rate of the molecule across the monolayer relative to its apical-
to-basolateral (AP–BL) rate of transfer. In general, compounds with
good passive membrane permeability (AP–BL transfer rate) and
low efflux ratio tend to exhibit good brain exposure.12 Compound
3 (NB-216) was then identified as our first lead compound.
Cleaving Enzyme (BACE-1) and c-secretase generates Ab peptides
from the Amyloid Precursor Protein (APP).1 They subsequently
form oligomers, fibrils and plaques, which are believed to induce
neurodegeneration.2 Mice lacking the gene for BACE-1 are viable
and fertile, and do not produce Ab-peptides. Inhibition of BACE-1
is therefore expected to provide a disease-modifying therapy for
AD.3 BACE-1 is a membrane-bound aspartyl protease that cleaves
APP primarily within the acidic endosomes in neurons. BACE-1
binds APP-derived oligo-peptide inhibitors in an extended cleft
via multiple hydrogen bond interactions.4 Nanomolar inhibition
of BACE-1 was shown with the peptide inhibitor OM99-2
(MW = 893 Da),5 but such large and polar compounds do not pen-
etrate the blood–brain barrier (BBB) and therefore lack in vivo
activity. In the past decade, synthetic inhibitors of BACE-1 have
been reported by a large variety of research groups.6,7
Starting from BACE-1 inhibitor 1 (NB-544),8 we aimed to syn-
thesize BACE-1 inhibitors with reduced lipophilicity and better
brain penetration (Fig. 1). The core of 1 (ethanolamine and P1–P2
amide group) was retained in series 2, but the P2–P3 amide group
was removed and aromatic rings were inserted into the P1 and P2
positions of the macrocycle. This new scaffold with reduced pep-
We prepared a series of macrocyclic ethanolamines as depicted
in Scheme 1 (according to reaction procedures described in earlier
publications).13,14 3-Benzylhydroxy-benzaldehyde underwent
a
Wittig–Horner reaction to provide 4 as a pure trans-stereoisomer.
Enantioselective hydrogenation with (S,S)-(COD)Et-DuPhos
Rh(I)BF4 in EtOAc/MeOH provided the enantiomerically pure ami-
no acid 5 (ee >99%).15 The choice of the solvents was crucial to pro-
vide a good turnover for this reaction. Traces of CH2Cl2 or
impurities in the starting material were detrimental. Debenzyla-
* Corresponding author. Tel.: +41 616962237; fax: +41 616962455.
E-mail address: andreas.lerchner@novartis.com (A. Lerchner).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.11.092

604
A. Lerchner et al. / Bioorg. Med. Chem. Lett. 20 (2010) 603–607
The chlorohydrin 7 was then converted in situ to the epoxide
P1
P3
using NaOH in EtOH, and subsequently opened by a series of
amines yielding Boc-protected aminoalcohols, which underwent
Cbz-protection of the secondary amino group and Boc-deprotec-
tion to provide amines 8. Amide formation of 8 with a series of
acids yielded 9. Ring forming metathesis using the Grubbs II cata-
lyst,17 followed by Cbz-deprotection and hydrogenation of the
formed double bond then provided the desired macrocyclic etha-
nolamines 2.
At first, we investigated the SAR of the macrocyclic BACE-1
inhibitors in order to optimize potency (Table 1, compounds 10
to 15); low nanomolar potency was achieved with compound 15,
where substituent R1 is propane-1-sulfonic acid methyl-amide.
However, testing compounds 10–15 in the MDR1–MDCK assay re-
vealed that they generally had significant efflux (ratio >10) and low
passive permeability. It has also been found by others that BACE-1
inhibitors with highly polar P2 substituents are subject of P-gP-
mediated efflux.10
P2'
O
N
N
H
N
H
O
OH
1
BACE-1 IC50 = 22 nM
P2
O
O
X
R2
N
H
N
H
Y
OH
2
R1
X = O or NH; Y = N or C;
R1 = H, Me, MOM, oxazol, N(Me)SO2Pr
O
O
We then focused on less polar P2 substituents and systemati-
cally investigated the environment of the ethanolamino group.
Methoxymethyl or methyl groups as substituents R3 (compounds
16-17) could not significantly improve the permeability properties,
whereas fluorinated alkyl groups (compounds 18-19) improved
the passive permeability and reduced the efflux ratio. Unfortu-
nately, fluorination of the alkyl groups was linked to major reduc-
tion of potency on BACE-1. While the mono-fluorinated compound
18 maintained most of the potency in the BACE-1 binding assay, its
potency in the cellular assay was weak (IC50 in APP over-express-
HN
N
N
H
H
OH
3
O
Figure 1. Development of peptidic BACE-1 inhibitor
inhibitor 3.
1 to macrocyclic BACE-1
ing CHO cells = 2.2 l
M).18 Efforts to further shield the ethanolami-
tion of 5 and subsequent allylation under standard conditions pro-
vided amino acid 6. Conversion of 6 to 7 was achieved by addition
of ICH2Cl and LDA in THF at ꢀ74 °C, followed by reduction with
NaBH4 in EtOH at ꢀ78 °C; the pure stereoisomer was isolated after
purification by column chromatography.16
no group with sterically more demanding groups led to the
investigation of bulkier groups at the benzylic position. Therefore,
we investigated dimethylation as well as introduction of cycloal-
kanes of different ring sizes (Table 2).
H
O
O
O
O
O
O
a
O
b
P
+
O
O
O
N
H
O
O
O
O
O
N
H
O
N
H
O
O
O
4
5
c,d
O
O
O
g-i
e,f
O
O
R2
H2N
N
O
O
N
H
Cl
O
N
Cbz
OH
H
OH
O
8
7
6
O
X
OH
j
X = NH or O, Y = CH or N,
for R1 respectively R2 see tables 1 and 2
Y
R1
O
O
k,l
O
O
R2
R2
X
X
N
N
H
N
H
N
H
Y
OH
Y
Cbz
OH
R1
R1
9
2
Scheme 1. Reagents and conditions: (a) DBU, CH2Cl2, 88%; (b) 1% (S,S)-(COD)Et-DuPhos Rh(I)BF4, EtOAc–MeOH, H2 quant.; (c) Pd/C, H2, EtOH; (d) K2CO3, acetone, allyl
bromide, reflux, 95% over two steps; (e) ICH2Cl, LDA, THF, ꢀ74 °C, crude; (f) NaBH4, EtOH, ꢀ78 °C, 57% over two steps; (g) H2NR2, NaOH, EtOH, 50 °C, 40–60%; (h) CbzCl,
CH2Cl2, aq Na2CO3, quantitative; (i) 4 N HCl in dioxane, quantitative; (j) EDCl, HOBt, NEt3, CH2Cl2, 80–99%; (k) 5% Grubbs II, CH2Cl2, 50 °C, 1 h, 30–88%; (l) Pd/C, H2, THF/EtOH,
60–80%.

A. Lerchner et al. / Bioorg. Med. Chem. Lett. 20 (2010) 603–607
605
Table 1
SAR for MDR1–MDCK permeation data of macrocyclic BACE-1 inhibitors. BACE-1 activity was measured as described18
O
R3
O
R2
X
N
H
N
H
Y
OH
R1
Compound
X
Y
R1
R2
R3
BACE-1 IC50 (nM)
MDR1–MDCK
Efflux ratio PBL–AP/PAP–BL
PAP–BL (10ꢀ6 cm/s)
10
11
12
13
14
15
16
17
18
19
NH
O
C
N
N
C
C
C
C
N
C
C
H
Me
Me
H
H
H
H
H
H
Me
H
Me
Me
H
H
H
H
H
H
292
42
27
60
19
1
668
83
177
>10,000
2.0
1.3
17
23
147
174
144
16
26
24
9.6
3.2
NH
NH
NH
NH
NH
O
0.17
0.16
0.11
0.95
1.3
1.3
3.8
5.6
CH2OCH3
1-ox-4-azol-yl
N(Me)SO2Pr
CH2OCH3
Me
CH2OCH3
Me
CH2F
CF3
NH
NH
CH2OCH3
CH2OCH3
P
AP–BL is the permeability trough MDR1-MDCK cell monolayer in the apical-to-basolateral direction, and PBL–AP is the permeability from the basolateral to the apical site of the
monolayer, the direction of P-gP-mediated transport.
Table 2
SAR and MDR1–MDCK permeation data of macrocyclic BACE-1 inhibitors; disubstitution in alpha position to amino group
O
O
R2
X
W
N
H
N
H
Y
OH
R1
Entry
X
Y
R1
R2
W
BACE-1 IC50 (nM)
MDR1–MDCK
Efflux ratio PBL–AP/PAP–BL
PAP–BL (10ꢀ6 cm/s)
3 (NB-216)
NH
O
O
C
N
N
C
C
C
C
C
C
CH2OCH3
Me
H
H
H
H
H
H
H
Cyclopropyl
Cyclopropyl
Cyclopropyl
Cyclopropyl
Cyclopropyl
–CH2–
–CMe2–
Cyclobutyl
Cyclopentyl
17
17
9
1
2
60
50
67
50
3.1
4.0
4.9
0.4
0.28
0.16
1.8
1.2
1.4
4.1
3.5
3.7
33
54
174
16
20
21
22
23
24
25
26
27
CH2OCH3
N-Butyrolactam
N(Me)SO2Pr
CH2OCH3
CH2OCH3
CH2OCH3
CH2OCH3
O
NH
NH
NH
NH
NH
Me
Me
10
4.4
P
AP–BL is the permeability through MDR1–MDCK cell monolayer in the apical-to-basolateral direction, and PBL–AP is the permeability from the basolateral to the apical site of
the monolayer, the direction of P-gP-mediated transport.
These substitutions did not generally change inhibitory activity,
with cyclopropanes (3 and 20–23) showing slightly superior po-
tency. Cyclopropanes were also found to be the best in this series
with respect to passive permeability and P-gP efflux. Optimization
of potency within the group of cyclopropanes was again possible
with more polar substituents R1 extending into the P2-site, but
only at the cost of high efflux and reduced passive permeability
(22 and 23).
Investigation of compounds 25–27 showed that dimethyl sub-
stitution, cyclobutanes and cyclopentanes also led to an improve-
ment in passive permeability and reduction of efflux in
comparison to the unsubstituted benzylic amine 24. However,
these changes in permeability properties were inferior to the ones
seen with cyclopropane. While it is expected that compounds with
a higher molecular weight and higher PSA have lower permeabil-
ity, as exemplified by modifications of substituent R1, the effect
of the environment of the ethanolamino group on passive perme-
ability and P-gP triggered some more questions.
We observed that the electron-withdrawing substituents fluo-
roalkyl or cyclopropyl in P10 improved passive permeability and re-
duced efflux ratio in the MDR1–MDCK assay (Table 1). Therefore,
we assumed that these data could be explained at least partially
by basicity changes of the ethanolamine nitrogen in the individual
compounds. Measurement of the pKa indeed revealed that the
poorly permeable compound 17 had a pKa of 8.5. Compounds 18
and 3, with moderate permeability had pKa values of 7.2 and 7.3.
Compound 19 with almost no efflux and good permeability had a
pKa of 3.8. Overall, there was a very good correlation between
pKa values of the amino group and permeability properties.
Interestingly, the major impact of the pKa value was on the ef-
flux ratio, while passive permeability was less affected. On the
other hand, significant reduction of basicity decreased the potency
on BACE-1 considerably. Compounds with cyclopropyl moieties
such as compound 3 (NB-216) with an intermediate pKa of 7.3
seemed to be a good compromise between achieving acceptable
brain uptake and maintaining sufficient potency towards BACE-1.

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A. Lerchner et al. / Bioorg. Med. Chem. Lett. 20 (2010) 603–607
Figure 2. Co-crystal structure of the BACE-1 complex with 3 (NB-216). Left panel: Surface representation showing the NB-216 complex (green) with the reference inhibitor
OM99-2 superimposed (magenta). Right panel. Close-up view of the binding interactions with potential hydrogen-bonded contacts (<3.4 Å) highlighted (dashed lines). Note
the polar contact between the R1 substituent and Arg235.
Table 3
To gain detailed insights into the binding of compound 3, the
crystal structure of its complex with BACE-1 was determined to
2.1 Å resolution.19 Close-up views are shown in Figure 2. As illus-
trated by the structural overlay with OM99-24 (Fig. 2, left), NB-216
spans the S3–S2’ enzyme subsites and follows closely the mode of
binding of this peptidomimetic inhibitor. In comparison to the linear
OM99-2, however, the macrocycle of NB-216 affords greater confor-
mational rigidity, while filling the contiguous S1–S2–S3 pockets
much better, with additional van der Waals contacts to Leu30,
Phe108, Ile110, Trp115, Ile118, and residues Gly11, Gln12, and
Gly13 of the 10s loop. The R1 methoxymethylene group is stacked
against the Arg235 guanidinium group (Fig. 2, left). This substituent
has well-defined electron-density only up to the oxygen atom, indi-
cating that its terminal methyl group remains mobile.
The introduction of the cyclopropyl substituent neither alters
the binding of the ethanolamine transition state mimic to the cat-
alytic aspartates, nor the position of the benzyl group in S2’ (by
comparison with the previously reported X-ray analysis of the
BACE-1 complex with 18).
We selected three cyclopropylamines (compounds NB-216, 20,
and 21) for in vivo investigation and compared them with the
unsubstituted benzylamine 11. After oral administration, drug con-
centrations in plasma and brain, as well as brain levels of Ab40 and
C99 were measured 4 hours after dosing (Fig. 3, Table 3).20 The
In vitro potency and selectivity, brain and plasma levels, and in vivo efficacy of
selected compounds
11
NB-216
20
21
IC50 BACE-1
IC50 CHO
IC50 CathD
IC50 CathE
Plasma (
Brain (
Ab40
Significance
C99
32 nM
55 nM
156 nM
8 nM
0.03
0.04
7%
p >0.05
5%
p >0.05
17 nM
20 nM
1 nM
0.4 nM
1.2
0.25
45%
p <0.01
36%
p <0.01
15 nM
70 nM
11 nM
4 nM
3.0
0.32
72%
p <0.01
74%
p <0.01
9 nM
47 nM
3 nM
5 nM
2.2
0.54
66%
p <0.001
67%
p <0.001
l
M)
M)
l
Significance
Enzyme and cell assays were done as described.18 Reductions of Ab40 and C99 are
relative to vehicle control.
three cyclopropanes showed significant concentrations in plasma
and brain, in contrast to the low exposure of the unsubstituted
benzylic amine 11. In perfect agreement with brain levels, 11
showed no reduction in Ab and C99, whereas the tested cyclopro-
panes demonstrated reduction of Ab by 45% to 72% and reduction
of C99 by 36% to 74%. This study demonstrates that po application
of our macrocyclic BACE-1 inhibitors at 60 lmol/kg gave sub-
micromolar brain levels and resulted in acute reduction of Ab in
brain.
It could further be demonstrated that the MDR1–MDCK assay
was useful in identifying a chemotype with favorable permeability
and limited efflux, which in turn predicted a good brain uptake.
The PK/PD data in Table 3 demonstrated a nice correlation of brain
concentrations with acute pharmacological effects. Absolute com-
pound brain concentrations were used here, the free fraction in
the brain and the concentration in CSF were not determined.
The optimal balance between the four key properties: enzy-
matic potency, cellular potency, passive permeability and P-gP
mediated efflux, was found for compounds with a pKa of the etha-
nolamine between 7 and 7.5. Compounds with higher pKa values
usually show high enzymatic and cellular potency, but poor per-
meability. Lower pKa values are favorable in terms of permeability
and efflux, but we observed a dramatic loss of cellular potency. A
similar effect was shown in a recent publication, describing the
influence of pKa modulation on cellular activity, log D values, and
oral absorption of ethanolamine BACE-1 inhibitors.21 Cyclopropyl-
amine type BACE-1 inhibitors have favorable physicochemical
properties for in vivo efficacy and are subject of further pharmaco-
100
80
60
40
20
0
forebrain C99
forebrain Aβ
11
NB-216
20
21
Figure 3. Reduction of Ab and C99 (levels of forebrain C99 (black bars) and Ab40
(red bars) relative to vehicle control. Application of compounds po at 60 mol/kg to
l
APP51/16 tg mice, sacrificed after 4 hours. Vehicle is 2% Cremophor EL in water.
Shown are Mean SEM.20

A. Lerchner et al. / Bioorg. Med. Chem. Lett. 20 (2010) 603–607
607
8. Machauer, R.; Laumen, K.; Veenstra, S.; Rondeau, J. M.; Tintelnot-Blomley, M.;
Betschart, C.; Jaton, A. L.; Desrayaud, S.; Staufenbiel, M.; Rabe, S.; Paganetti, P.;
Neumann, U. Bioorg. Med. Chem. Lett. 2009, 19, 1366.
9. Meredith, J. E., Jr.; Thompson, L. A.; Toyn, J. H.; Marcin, L.; Barten, D. M.;
Marcinkeviciene, J.; Kopcho, L.; Kim, Y.; Lin, A.; Guss, V.; Burton, C.; Iben, L.;
Polson, C.; Cantone, J.; Ford, M.; Drexler, D.; Fiedler, T.; Lentz, K. A.; Grace, J. E.,
Jr.; Kolb, J.; Corsa, J.; Pierdomenico, M.; Jones, K.; Olson, R. E.; Macor, J. E.;
Albright, C. F. J. Pharmacol. Exp. Ther. 2008, 326, 502.
kinetic and pharmacological investigations (manuscript in prepa-
ration). However, the introduction of the cyclopropyl into ethanol-
amine type BACE-1 inhibitors led to loss of selectivity over the
closely related aspartyl proteases cathepsin D and E. Further inves-
tigations are needed to achieve high potency on BACE-1, together
with selectivity over cathepsin D and E, and brain permeability.
10. Hussain, I.; Hawkins, J.; Harrison, D.; Hille, C.; Wayne, G.; Cutler, L.; Buck, T.;
Walter, D.; Demont, E.; Howes, C.; Naylor, A.; Jeffrey, P.; Gonzalez, M. I.;
Dingwall, C.; Michel, A.; Redshaw, S.; Davis, J. B. J. Neurochem. 2007, 100, 802.
11. Wang, Q.; Rager, J. D.; Weinstein, K.; Kardos, P. S.; Dobson, G. L.; Li, J.; Hidalgo, I.
J. Int. J. Pharm. 2005, 288, 349.
12. Garberg, P.; Ball, M.; Borg, N.; Cecchelli, R.; Fenart, L.; Hurst, R. D.; Lindmark, T.;
Mabondzo, A.; Nilsson, J. E.; Raub, T. J.; Stanimirovic, D.; Terasaki, T.; Oberg, J.
O.; Osterberg, T. Toxicol. In Vitro 2005, 19, 299.
13. Betschart, C.; Lerchner, A.; Machauer, R.; Rueeger, H.; Tintelnot-Blomley, M.;
Veenstra, S. J. WO Patent 2006074950, 1-13-2006; 20060720, 142.
14. Betschart, C.; Koller, M.; Laumen, K.; Lerchner, A.; Machauer, R.; McCarthy, C.;
Tintelnot-Blomley, M.; Veenstra, S. J. WO Patent 2007077004, 12-28-2006;
20070712, 118.
Acknowledgements
X-ray data collections were performed at the Swiss Light
Source, Paul Scherrer Institute, Villigen, Switzerland. We are grate-
ful to the machine and beamline groups whose outstanding efforts
have made these experiments possible.
Supplementary data
15. Wang, W.; Xiong, C.; Zhang, J.; Hruby, V. J. Tetrahedron 2002, 58, 3101.
16. Miller, J. F.; Brieger, M.; Furfine, E. S.; Hazen, R. J.; Kaldor, I.; Reynolds, D.;
Sherrill, R. G.; Spaltenstein, A. Bioorg. Med. Chem. Lett. 2005, 15, 3496.
17. Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40,
2247.
18. Machauer, R.; Veenstra, S.; Rondeau, J. M.; Tintelnot-Blomley, M.; Betschart, C.;
Neumann, U.; Paganetti, P. Bioorg. Med. Chem. Lett. 2009, 19, 1361.
19. X-ray co-ordinates for the complex of BACE-1 with inhibitor NB-216 have been
deposited in the Protein Data Bank (http://www.rcsb.org) and can be accessed
under code PDB ID: 3K5C.
20. Abramowski, D.; Wiederhold, K. H.; Furrer, U.; Jaton, A. L.; Neuenschwander,
A.; Runser, M. J.; Danner, S.; Reichwald, J.; Ammaturo, D.; Staab, D.; Stoeckli,
M.; Rueeger, H.; Neumann, U.; Staufenbiel, M. J. Pharmacol. Exp. Ther. 2008, 327,
411.
21. Charrier, N.; Clarke, B.; Cutler, L.; Demont, E.; Dingwall, C.; Dunsdon, R.;
Hawkins, J.; Howes, C.; Hubbard, J.; Hussain, I.; Maile, G.; Matico, R.; Mosley, J.;
Naylor, A.; O’Brien, A.; Redshaw, S.; Rowland, P.; Soleil, V.; Smith, K. J.;
Sweitzer, S.; Theobald, P.; Vesey, D.; Walter, D. S.; Wayne, G. Bioorg. Med. Chem.
Lett. 2009, 19, 3674.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2009.11.092.
References and notes
1. Hardy, J.; Selkoe, D. J. Science 2002, 297, 353.
2. Crouch, P. J.; Harding, S. M.; White, A. R.; Camakaris, J.; Bush, A. I.; Masters, C. L.
Int. J. Biochem. Cell Biol. 2008, 40, 181.
3. Stockley, J. H.; O’Neill, C. Cell Mol. Life Sci. 2008, 65, 3265.
4. Hong, L.; Koelsch, G.; Lin, X.; Wu, S.; Terzyan, S.; Ghosh, A. K.; Zhang, X. C.;
Tang, J. Science 2000, 290, 150.
5. Ghosh, A. K.; Bilcer, G.; Harwood, C.; Kawahama, R.; Shin, D.; Hussain, K. A.;
Hong, L.; Loy, J. A.; Nguyen, C.; Koelsch, G.; Ermolieff, J.; Tang, J. J. Med. Chem.
2001, 44, 2865.
6. Ghosh, A. K.; Kumaragurubaran, N.; Hong, L.; Kulkarni, S.; Xu, X.; Miller, H. B.;
Reddy, D. S.; Weerasena, V.; Turner, R.; Chang, W.; Koelsch, G.; Tang, J. Bioorg.
Med. Chem. Lett. 2008, 18, 1031.
7. Silvestri, R. Med. Res. Rev. 2009, 29, 295.