Determination of guinea-pig cortical gamma-secretase activity ex vivo following the systemic administration of a gamma-secretase inhibitor.
(2S)-2-{[(3,5-Diflurophenyl)acetyl]amino}-N-[(3S)-1-methyl-2-oxo-5-phenyl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]propanamide (compound E) is a gamma-secretase inhibitor capable of reducing amyloid beta-peptide (1-40) and amyloid beta-peptide (1-42) levels. In this study we investigated the effect of in vivo administration of compound E on guinea-pig plasma, CSF and cortical amyloid beta-peptide (1-40) concentration. Using repeated sampling of CSF, compound E (30 mg/kg p.o.) was shown to cause a time-dependent decrease in CSF amyloid beta-peptide (1-40) levels, which was maximal at 3 h (70% inhibition), compared to baseline controls. After 3 h administration, compound E (3, 10 and 30 mg/kg p.o.), reduced plasma, CSF and DEA-extracted cortical amyloid beta-peptide (1-40) levels by 95, 97 and 99%; 26, 48 and 78%; 32, 33, and 47%, respectively, compared to vehicle control values. In the same animals, compound E (3, 10 and 30 mg/kg p.o.) inhibited cortical gamma-secretase activity, determined ex vivo using the recombinant substrate C100Flag, by 40, 71 and 79% of controls, respectively. These data demonstrate the value of determining not only the extent by which systemic administration of a gamma-secretase inhibitor reduces amyloid beta-peptide, but also the inhibition of brain gamma-secretase activity, as a more direct estimate of enzyme occupancy.
Grimwood
S
S
Merck, Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Terlings Park, Eastwick Road, Harlow, Essex CM20 2QR, UK.
Hogg
J
J
Jay
M T
MT
Lad
A M
AM
Lee
V
V
Murray
F
F
Peachey
J
J
Townend
T
T
Vithlani
M
M
Beher
D
D
Shearman
M S
MS
Hutson
P H
PH
D000284:Administration, Oral; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000378:metabolism; D000818:Animals; D001152:Arsenicals / Q000008:administration & dosage; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D006690:Bisbenzimidazole / Q000008:administration & dosage / Q000031:analogs & derivatives; D002540:Cerebral Cortex / Q000187:drug effects* / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D010450:Endopeptidases; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism; D011480:Protease Inhibitors / Q000008:administration & dosage*
D016229:Amyloid beta-Peptides; D001152:Arsenicals; D010446:Peptide Fragments; D011480:Protease Inhibitors; C078592:amyloid beta-protein (1-40); C018022:compound E (Friedheim); D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; D006690:Bisbenzimidazole