Entwicklung Metallorganischer Inhibitoren Für Nukleotid-Bindende Enzyme

Die Arbeitsgruppe MEGGERS befasst sich unter anderem mit der Untersuchung inerter Metallkomplexe als potente und selektive Enzyminhibitoren. Im Fokus der Forschung lag zunächst die Familie der Protein- und Lipidkinasen, der größten Enzymklasse im menschlichen Körper. Hier konnte eindrucksvoll gezeig...

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Bibliographic Details
Main Author: Streib, Manuel
Contributors: Meggers, Eric (Dr.) (Thesis advisor)
Format: Doctoral Thesis
Published: Philipps-Universität Marburg 2013
Online Access:PDF Full Text
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The synthesis of selective inhibitors represents a fundamental field of medicinal chemistry. In contrast to many other groups who prepare purely organic compounds with biological activity, MEGGERS et al. have been focusing on organometallic compounds as enzyme inhibitors. These compounds comprise a pharmacophore ligand, a metal center and various ligands to fulfill the remaining coordination sites. The resulting inert and rigid metal complexes show some interesting features: the pharmacophore ligand plays a major role for the inhibitor recognition, the metal center allows the design of a sophisticated architecture through its ability to act as an octahedral center overcoming the limitations of the usual tetrahedral geometry of purely organic molecules. The vast number of potential ligands around the metal center gives rise to a highly diverse library of compounds which can be tailored in a rather easy fashion. Up to now this concept has been proven successful for protein kinases and hence a series of highly potent and selective, competitive inhibitors were published by our group. In order to prove the generality of this successful strategy, its transfer to new target enzymes was envisioned. The kinome constitutes a fraction of a larger ensemble of proteins, the so-called purinome. These enzymes share a common feature, their ability to bind purine-based nucleotides within their active sites. This thesis describes the approach to obtain competitive, organometallic inhibitors of nucleotide-binding proteins by mimicking the overall-structure of purine nucleotides. At the beginning a bidentate pharmacophore ligand, 8-(2-pyridyl)adenine was synthesized and its coordination chemistry with different metal centers was investigated. One of these metal complexes, a Ruthenium half-sandwich complex with a cyclopentadienyl and a carbonyl ligand, was chosen as nucleotide probe for further examination. It was screened against a panel of kinases and ATPases and showed a good selectivity profile. One of the screening hits of the ATPase panel was chosen as target enzyme: MTH1 is a pyrophosphatase, which is involved in the DNA repair machinery related to oxidative damage. The purine based Ruthenium half-sandwich complex exhibited an IC50 of 151 µM against MTH1. A crystal structure of the inhibitor bound within the active site of MTH1 was obtained. A second pharmacophore scaffold was developed, 6-(2-pyridyl)quinazolin-4-amin, and with its respective Ruthenium half-sandwich complex the IC50 could be improved by two orders of magnitude. Therefore this quinazoline based complex was chosen as a new lead structure. SAR investigations were performed by modifying both the cyclopentadienyl and the pharmacophore ligand separately. The affinity towards MTH1 was steadily improved and the combination of the best modifications led to a single-digit nanomolar MTH1 inhibitor with an excellent selectivity profile in an extended kinase and ATPase panel. To understand the high affinity of this inhibitor, it was co-crystallized with MTH1. The resulting co-crystal structure gave an insight of the inhibitor binding within the active site and allowed the discussion of important inhibitor enzyme interactions.