Reversible Assembly of Proteolysis Targeting Chimeras

Abstract

PROteolysis TArgeting Chimeras (PROTACs) are of significant current interest for the development of probe molecules and drug leads. However, they suffer from certain limitations. PROTACs are rule-breaking molecules with sub-optimal cellular permeability, solubility, and other drug-like properties. In particular, they exhibit an unusual dose−response curve where high concentrations of the bivalent molecule inhibit degradation activity, a phenomenon known as the hook effect. This will likely complicate their use in vivo. In this study, we explore a novel approach to create PROTACs that do not exhibit a hook effect. This is achieved by equipping the target protein and E3 ubiquitin ligase ligands with functionalities that undergo rapid and reversible covalent assembly in cellulo. We report the development of Self-Assembled Proteolysis Targeting Chimeras that mediate the degradation of the Von Hippel−Lindau E3 ubiquitin ligase and do not evince a hook effect.

Combinatorial Ubiquitination REal-time PROteolysis (CURE-PROs): A Modular Platform for Generating Reversible, Self-Assembling Bifunctional Targeted Degraders

“…din-3-yl)-1,3-dioxoisoindolin-4-yl)methyl)-2,3-dihydroxy-4-methoxybenzamide (46) was synthesized by following the general method of HATU-mediated coupling of 2,3-dihydroxy-4-methoxybenzoic acid (44,141…”

“…40−42 We recently reported the development of Self-Assembled Proteolysis-TArgeting Chimeras (SAPTACs), pseudohomodimeric molecules that demonstrated self-degradation of VHL using ligands that also assemble in cells via reversible, bio-orthogonal linkers, i.e., phenylboronic acid and catechol or o-acetlyphenylboronic acid and an alkoxyamine. 44 Strategies employing click chemistry have also been used to form active degraders within cells. 45,46 However, these irreversible reactions can form heterodimeric compounds outside cells, which, in turn, dramatically affects cellular permeability.…”

“…We have modified the Coferon platform to generate Combinatorial Ubiquitination REal-time PROteolysis (CURE-PROs) as reversible, self-assembling heterobifunctional degraders (Figure ). CURE-PROs are designed to come together in cells upon binding to their target, where they form reversible, covalent dimers through phenylboronic acid and complementary diol/catechol linkers. − We recently reported the development of Self-Assembled Proteolysis-TArgeting Chimeras (SAPTACs), pseudohomodimeric molecules that demonstrated self-degradation of VHL using ligands that also assemble in cells via reversible, bio-orthogonal linkers, i.e., phenylboronic acid and catechol or o-acetlyphenylboronic acid and an alkoxyamine . Strategies employing click chemistry have also been used to form active degraders within cells. , However, these irreversible reactions can form heterodimeric compounds outside cells, which, in turn, dramatically affects cellular permeability.…”

Innovative, combinatorial and high-throughput approaches to degrader synthesis

“…In a similar vein, Gui et al utilised a reversible reaction to synthesise degraders termed as “SAPTACs” (self-assembled proteolysis targeting chimeras) in cellulo . 27 This method was used to generate homodimeric degraders, previously noted by the Ciulli group, to result in the self-degradation of the protein. 28 The SAPTAC approach was demonstrated using two different methods: the first using a catechol–boronic acid system to generate a boronic ester in situ (Scheme 7(A)), and the second via a hydroxylamine condensation, facilitated by a proximal boronic acid group (Scheme 7(B)).…”

“…Over the last decade, an increasing number of new transformations have been reported in the literature for accessing degraders in a more streamlined fashion, moving away from lengthy linear synthetic routes, and towards parallel, combinatorial, and automated methods. Additionally, the development of CLIPTACs 26 and SAPTACs 27 were impressive examples of exploiting bioorthogonal chemistry to form PROTACs inside cells, bypassing the common issue of poor cellular permeability in beyond rule of 5 molecules. The approaches discussed in section two were strides forward in shortening the make-test-analyse cycle for new degraders, but synthetic throughput remained limited.…”