The potential of P1 site alterations in peptidomimetic protease inhibitors as suggested by virtual screening and explored by the use of C-C-coupling reagents.
A synthetic concept is presented that allows the construction of peptide isostere libraries through polymer-supported C-acylation reactions. A phosphorane linker reagent is used as a carbanion equivalent; by employing MSNT as a coupling reagent, the C-acylation can be conducted without racemization. Diastereoselective reduction was effected with L-selectride. The reagent linker allows the preparation of a norstatine library with full variation of the isosteric positions including the P1 side chain that addresses the protease S1 pocket. Therefore, the concept was employed to investigate the P1 site specificity of peptide isostere inhibitors systematically. The S1 pocket of several aspartic proteases including plasmepsin II and cathepsin D was modeled and docked with approximately 500 amino acid side chains. Inspired by this virtual screen, a P1 site mutation library was designed, synthesized, and screened against three aspartic proteases (plasmepsin II, HIV protease, and cathepsin D). The potency of norstatine inhibitors was found to depend strongly on the P1 substituent. Large, hydrophobic residues such as biphenyl, 4-bromophenyl, and 4-nitrophenyl enhanced the inhibitory activity (IC50) by up to 70-fold against plasmepsin II. In addition, P1 variation introduced significant selectivity, as up to 9-fold greater activity was found against plasmepsin II relative to human cathepsin D. The active P1 site residues did not fit into the crystal structure; however, molecular dynamics simulation suggested a possible alternative binding mode.
Weik
Steffen
S
Leibniz Institute for Molecular Pharmacology (FMP), and Free University Berlin, Takustrasse 3, 14195 Berlin, Germany.
Luksch
Torsten
T
Evers
Andreas
A
Böttcher
Jark
J
Sotriffer
Christoph A
CA
Hasilik
Andrej
A
Löffler
Hans-Gerhard
HG
Klebe
Gerhard
G
Rademann
Jörg
J
D000614:Aminocaproates / Q000737:chemistry; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors; D002402:Cathepsin D / Q000037:antagonists & inhibitors; D016333:HIV Protease / Q000187:drug effects; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D018716:Molecular Mimicry; D011480:Protease Inhibitors / Q000737:chemistry*; D015800:Protozoan Proteins; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism
D000614:Aminocaproates; D007202:Indicators and Reagents; D011480:Protease Inhibitors; D015800:Protozoan Proteins; C034495:3-amino-2-hydroxy-5-methylhexanoic acid; D016282:Aspartic Acid Endopeptidases; D016333:HIV Protease; C100637:plasmepsin II; D002402:Cathepsin D