title: Protein Degradation by In-Cell Self-Assembly of Proteolysis Targeting Chimeras.
abstract: Selective degradation of proteins by proteolysis targeting chimeras (PROTACs) offers a promising potential alternative to protein inhibition for therapeutic intervention. Current PROTAC molecules incorporate a ligand for the target protein, a linker, and an E3 ubiquitin ligase recruiting group, which bring together target protein and ubiquitinating machinery. Such hetero-bifunctional molecules require significant linker optimization and possess high molecular weight, which can limit cellular permeation, solubility, and other drug-like properties. We show here that the hetero-bifunctional molecule can be formed intracellularly by bio-orthogonal click combination of two smaller precursors. We designed a tetrazine tagged thalidomide derivative which reacts rapidly with atrans-cyclo-octene tagged ligand of the target protein in cells to form a cereblon E3 ligase recruiting PROTAC molecule. The in-cell click-formed proteolysis targeting chimeras (CLIPTACs) were successfully used to degrade two key oncology targets, BRD4 and ERK1/2. ERK1/2 degradation was achieved using a CLIPTAC based on a covalent inhibitor. We expect this approach to be readily extendable to other inhibitor-protein systems because the tagged E3 ligase recruiter is capable of undergoing the click reaction with a suitably tagged ligand of any protein of interest to elicit its degradation.
authors.affiliation: Astex Pharmaceuticals , 436 Cambridge Science Park, Cambridge, CB4 0QA, U.K.
authors.forename: Honorine
authors.initials: H
authors.lastname: Lebraud
authors.affiliation: Astex Pharmaceuticals , 436 Cambridge Science Park, Cambridge, CB4 0QA, U.K.
authors.forename: David J
authors.initials: DJ
authors.lastname: Wright
authors.affiliation: Astex Pharmaceuticals , 436 Cambridge Science Park, Cambridge, CB4 0QA, U.K.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Johnson
authors.affiliation: Astex Pharmaceuticals , 436 Cambridge Science Park, Cambridge, CB4 0QA, U.K.
authors.forename: Tom D
authors.initials: TD
authors.lastname: Heightman