In vivo inhibition of cathepsin B by peptidyl (acyloxy)methyl ketones.
Peptidyl (acyloxy)methyl ketones, previously established as potent irreversible inhibitors of the cysteine proteinase cathepsin B in vitro, were investigated and optimized for their inhibitory activity in vivo. Incorporation of polar or charged functional groups in the inhibitor structure afforded effective cathepsin B inhibition, following dosing to rats. The most effective inhibitor, Z-Phe-Lys-CH2OCO-(2,4,6-Me3)Ph (8), was found to give ED50 values of 18 mg/kg po (orally) and 5.0 mg/kg ip (intraperitoneally) at 4-5 h postdose, and 2.4 mg/kg sc (subcutaneously) at 24 h postdose, for liver cathepsin B inhibition (measured ex vivo). The subcutaneous route of administration of (acyloxy)methyl ketone 8 also provided potent cathepsin B inhibition in certain peripheral tissues (e.g., ED50 1.0 mg/kg for skeletal muscle, 0.1 mg/kg for heart). These investigations demonstrate that peptidyl (acyloxy)methyl ketones such as 8 have promise as tools for the characterization of in vivo biochemical processes and as therapeutic agents.
Department of Lipid and Protease Biochemistry, Syntex Research, Palo Alto, California 94304.
B M
BM
Wagner
R A
RA
Smith
P J
PJ
Coles
L J
LJ
Copp
M J
MJ
Ernest
A
A
Krantz
D000284:Administration, Oral; D000595:Amino Acid Sequence; D000818:Animals; D002401:Cathepsin B / Q000037:antagonists & inhibitors*; D002417:Cattle; D004151:Dipeptides / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D007659:Ketones / Q000737:chemistry / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D051381:Rats; D013154:Spleen / Q000201:enzymology
D004151:Dipeptides; D007659:Ketones; D002401:Cathepsin B