Identification, lead optimization and validation of necroptosis and ferroptosis inhibitors
6 November 2017
Campus Drie Eiken - Building Q - promotiezaal - Universiteitsplein 1 - 2610 Antwerp (Wilrijk) (route: UAntwerpen, Campus Drie Eiken
4:00 PM - 6:00 PM
Koen Augustyns - Pieter Van der Veken
PhD defence Sam Hofmans - Department of Pharmaceutical Sciences
For many years cell death processes were divided in those that are regulated and those that are accidental. Apoptosis is the most extensively studied form of programmed cell death during development and aging whereas necrosis was considered as an accidental and unregulated form of cell death. Cell death research was revitalized by the finding that necrosis can occur in a regulated and controlled fashion. The main goal of this PhD was to synthesize inhibitors that intervene in the pathways of necroptosis and ferroptosis, two recently discovered forms of regulated necrosis. This allows further elucidation of their underlying molecular mechanisms and will demonstrate where therapeutic targeting is possible.
The finding of necroptosis as an alternative form of non-apoptotic regulated cell death became generally established with the identification of receptor-interacting protein kinase 1 (RIPK1) and RIPK3 as crucial protein kinases in this pathway and their targetability by chemical inhibitors. The most widely used inhibitors of necroptosis were dubbed ‘necrostatins’. Despite their excellent kinase selectivity, all of the reported necrostatins struggle with multiple drawbacks such as a narrow structure-activity relationship profile and non-ideal pharmacokinetic properties. Also, almost all published and commonly used inhibitors of RIPK1 are classified as either type II or type III kinase inhibitors. This opens up some interesting perspectives for the discovery of novel inhibitors that target the active site of RIPK1. In a comprehensive analysis of kinase inhibitor selectivity we discovered that tozasertib, originally developed as an anti-tumoral agent, showed a high affinity for RIPK1. In addition tozasertib presents typical structural elements of a type I kinase inhibitor. Structural analogues of tozasertib were synthesized during this PhD research since the use of these compounds may lead to new insights in the design of novel RIPK1 inhibitors.
Ferroptosis on the other hand is an iron-catalysed form of regulated necrosis and is critically dependent on glutathione peroxidase 4. A chemical inhibitor discovered by high-throughput screening displayed inhibition of ferroptosis and was dubbed ferrostatin-1. Ferrostatins inhibit oxidative lipid damage, but suffer from stability problems due to the presence of an ester moiety. This limits the application of these molecules in vivo, due to hydrolysis of the ester into the inactive carboxylic acid. During this PhD research novel ferroptosis inhibitors were synthesized containing amide and sulfonamide moieties. These compounds possessed improved stability, single digit nanomolar anti-ferroptotic activity and good ADME properties suitable for application in in vivo disease models.