Drug candidates with a covalent binding mode have gained interest since the approval of multiple covalent anticancer drugs, but were long avoided due to concerns regarding promiscuous reactivity... Show moreDrug candidates with a covalent binding mode have gained interest since the approval of multiple covalent anticancer drugs, but were long avoided due to concerns regarding promiscuous reactivity with off-target proteins. In this dissertation, the scope and versatility of the newly discovered in situ thiol–alkyne reaction is evaluated: the nonactivated alkynes exhibit an unprecedented target reactivity with excellent thiol selectivity, thus potentially outperforming currently used cysteine-reactive warheads. Chapter 1 starts with the history of (ir)reversible covalent inhibition, the reactivity of (non)activated alkynes, and the serendipitous discovery of the thiol–alkyne reaction. Established technologies for direct detection of covalent protein–drug adducts are reviewed in Chapter 2, and in Chapter 3 a detailed guide for the evaluation of (ir)reversible covalent inhibitors to obtain relevant kinetic parameters is provided, accompanied by kinetic simulations and step-wise protocols for enzymatic activity assays. In Chapter 4, the nitrile warhead in reversible CatK inhibitor odanacatib (ODN) is replaced with alkyne warheads to investigate whether it an irreversible covalent adduct is formed with cysteine protease cathepsin K (CatK) despite having a small recognition element. In Chapter 5, we evaluate if nonactivated alkynes can target noncatalytic cysteine residues by replacing the irreversible covalent acrylamide warhead in EGFR/HER2 inhibitor neratinib by an alkyne warhead. In Chapter 6, the impact of substituents on the alkyne warhead is explored using a panel of ubiquitin-based ABPs bearing substituents on the propargylamide warhead. Finally, the most important findings are summarized in Chapter 7, and placed in the context of covalent drug discovery. Show less
Proteins play an essential role in almost all the processes of a living organism, and post-translational modifications (PTM) can regulate their structure, location, function, and fate. Ubiquitin... Show moreProteins play an essential role in almost all the processes of a living organism, and post-translational modifications (PTM) can regulate their structure, location, function, and fate. Ubiquitin and ISG15 are two of the most versatile and common PTM modifiers in mammalian cells. Aberrant modification of Ubiquitin and ISG15 in cells results in various diseases, such as cancers and microbial infections. This dissertation introduces the development of small-molecule inhibitors against ISG15 deconjugating enzyme USP18 and ubiquitin deconjugating enzyme OTUB2 separately, and the identification of USP16 as a dual deconjugating enzyme that cleaves Ubiquitin and ISG15 from substrates. These research achievements are supposed to deepen the understanding of biology, regulation, and biochemical mechanisms of Ubiquitin and ISG15 deconjugating enzymes, thus paving the way for deconjugating enzymes-targeted therapeutics development in the future. Show less
