J . Med. Chem. 2000, 43, 2297-2299
2297
Ta ble 1. Fenchylamine Sulfonamide γ-Secretase Inhibitorsa
F en ch yla m in e Su lfon a m id e In h ibitor s of
Am yloid â P ep tid e P r od u ction by th e
γ-Secr eta se P r oteolytic P a th w a y:
P oten tia l Sm a ll-Molecu le Th er a p eu tic
Agen ts for th e Tr ea tm en t of Alzh eim er ’s
Disea se
Gilbert M. Rishton,*,† Daniel M. Retz,†
Paul A. Tempest,† J ames Novotny,† Steve Kahn,‡
J ames J . S. Treanor,‡ J ack D. Lile,‡ and
Martin Citron‡
Amgen, One Amgen Center Drive,
Thousand Oaks, California 91320-1789
Received December 21, 1999
In tr od u ction . The brain plaques associated with
Alzheimer’s disease (AD) are composed primarily of the
amyloid â peptides (Aâ40,42) which are produced from
the proteolytic processing of the â-amyloid precursor
protein (APP).1 The production of Aâ from APP proceeds
via two cleavages which are catalyzed by distinct pro-
tease activities known as the secretases.2 The cleavage
of APP at the Aâ N-terminal residue is catalyzed by the
recently cloned and characterized aspartic acid protease
named â-secretase.3 The Aâ C-terminal cleavage which
occurs at the transmembrane region of APP is attrib-
uted to the action of the yet unknown protease(s)
designated γ-secretase(s). In the brain of the AD patient,
aggregates of Aâ peptides are deposited resulting in
formation of the insoluble plaques and vascular deposits
characteristic of AD pathology.4 The overproduction of
the relatively hydrophobic Aâ42 component has been
particularly associated with plaque formation.5 Genetic
evidence suggests elevated brain levels of Aâ42 to be
the cause of early-onset familial AD.6
Inhibition of the â- and γ-secretase proteolytic path-
ways would be expected to decrease the production of
Aâ and potentially to slow the progression of AD. Cellu-
lar assays to measure inhibition of the overproduction
of Aâ42 have recently been developed.7 These assays
have allowed the initiation of investigations toward the
discovery of small-molecule inhibitors of Aâ production
in cell culture. Among the reports of Aâ production in-
hibitors in the patent literature, the cyclohexylalanine-
based statine 18 and the lipophilic dimethylaminoethyl
tetralin 29 serve as examples of chemically stable small-
molecule inhibitors of Aâ production in cell culture.
a
Elemental analyses obtained were within 0.4% of calculated
values. Compound 4: Anal. (C16H22FNO2S) C, H, N, F, S.
Compound 5: Anal. (C16H22ClNO2S) C, H, N, Cl, S. Compound
6: Anal. (C16H22BrNO2S) C, H, N, Br, S. Compound 7: Anal.
b
(C14H21NO2S2) C, H, N, S. Compound 4: a white solid; mp 128-
20
129 °C; [R]D ) +33.7 (c ) 0.05, MeOH). c Compound 7: a white
solid; mp 138-139 °C; [R]D20 ) -43.6 (c ) 0.05, MeOH). Selective
d
inhibition of the production of Aâ42 by inhibition of the γ-secretase
proteolytic pathway in HEK293 cells stably transfected with a
double mutant form of human APP(K595N/M596L) at an inhibitor
concentration of 2.5 µM (ref 7). Aâ40 was inhibited to a similar
extent. Percent (%) inhibition values are the average of four
experiments and IC50 values are the average of 4 experiments (
standard deviation. e The observed stimulation of the production
of soluble â-amyloid precursor protein (APPs) is consistent with
the inhibition of the production of Aâ via the secretase pathways.
We report here the discovery of low-molecular-weight,
chemically stable fenchylamine sulfonamide inhibitors
of the production of Aâ in cell culture which operate via
inhibition of the γ-secretase proteolytic pathway.
Resu lts a n d Discu ssion . The stereochemically un-
defined fenchylamine sulfonamide sample (3) (Table 1)
exhibited inhibition of Aâ42 production to the extent of
31% (@2.5 µM) with IC50 ) 5 µM, and Aâ40 production
was inhibited to a similar extent. Inhibition of Aâ pro-
duction was accompanied by reduction of p3, a concomi-
tant increase in â-secretase-cleaved APP C-terminal
fragments, and no change in secreted APPsâ (data not
shown), but with an increase in secreted APPsR. These
data indicate that the observed inhibition of Aâ produc-
tion was not due to nonspecific toxicity effects, a general
block in secretion, or inhibition of â-secretase cleavage
but rather due to specific inhibition of the γ-secretase
cleavage pathway.
Our subsequent analytical studies determined the
inhibitor sample 3 to be a 3:1 mixture of stereoisomeric
4-fluorophenyl fenchylamine sulfonamides. We set out
to identify the potent stereoisomer component of the
* To whom correspondence should be addressed. Phone: 805-447-
1064. Fax: 805-480-1337. E-mail: grishton@amgen.com.
† Department of Small Molecule Drug Discovery, MS 29-2-B.
‡ Department of Neurobiology, MS 29-2-B.
10.1021/jm990622z CCC: $19.00 © 2000 American Chemical Society
Published on Web 05/23/2000