Classical molecular glue degraders have been identified serendipitously, but rational screening strategies are emerging rapidly. Different discovery strategies for molecular glues will be discussed, including focused E3 ligase libraries and how to leverage ligase-protein interactions to identify novel molecular glues. The talk will highlight, rational screen for molecular glues, characterization of degron-ligase interaction and identifying novel chemical matter for neomorphic interactions.

Monovalent degraders enable the benefits of protein degradation while avoiding the development challenges associated with large PROTAC molecules. Unlike imids, which modify the substrate recognition of cereblon to degrade a neo-substrate, our work has focussed on modification of inhibitors to generate a combined protein-ligand surface that is recognised for degradation.  Progress and challenges in making this a general approach are highlighted through identification of novel BCL6 and Cyclin K degraders.

The promise of new medicines that operate through induced degradation has been stunted by a scarcity of systematic tools that can uncover the relevant design principles. Here we introduce GlueSEEKER®: an intramolecular editing-based screening system to remodel the surface landscapes of E3 ligases. We show that effector proteins can be re-engineered to produce neomorphic activity and that this expanded substrate repertoire presents ideal induced pharmacophores for small molecule glue design.

While the PROTAC approach to targeted protein degradation greatly benefits from rational design, the discovery of molecular glue degraders currently relies on screening approaches. This talk will discuss the design of a large cereblon-directing molecular glue library—and a multimodal screening strategy that resulted in discovery of potent and selective degraders of canonical neosubstrates such as GSPT1 and CK1a, as well as novel neosubstrates. Specific focus will be given to the development and application of a high-throughput deep proteomics screening platform that uncovered multiple potent and selective degraders of previously unreported cereblon neosubstrates.

Zinc finger transcription factors (TF) are an important target class in cancer and inflammation yet poorly explored due to lack of direct binding pockets. We will discuss the structure-based molecular glue exploration of T-reg regulator IKZF2 and expand the degradation approach with functional genomics to the family of 1656 zinc finger TF, revealing complexity of target and small molecule degradation selectivity.

Induced proximity between a target protein of interest (POI) and an enzyme that can modify proteins post-translationally can alter POI post-translational state that might then alter POI behaviour. We have created induced-proximity platforms to interrogate several POI post-translational modifications in cells. In this talk, I will provide proof of concept for targeted dephosphorylation of multiple target proteins, including transcription factors, and how this alters target protein function.

Residing beyond the rule-of-five space, proteolysis-targeting chimeras (PROTACs) pose challenges in terms of physicochemical properties. This makes an adjustment of in vitro ADME assays for PROTACs necessary and suggests a tailored DMPK cascade to optimize PROTACs towards oral bioavailability. Surrogate methods for permeability assessment, optimization strategies for absorption and adjustments taken for clearance prediction are discussed.

NMR spectroscopy and MD simulations revealed that the propensity of CRBN and VHL PROTACs to adopt folded and semi-folded conformations with reduced polar surface area correlates to higher cell permeability. Permeable PROTACs behaved as molecular chameleons that adopted their conformations and thereby their properties to the surrounding environment. Chameleonicity depended on the length and nature of the linker and may be particularly important for the discovery of oral VHL PROTACs.

To minimise the synthetic workload required for developing new oral PROTAC drugs, it is essential to incorporate ADME considerations from the outset of the discovery program to address limitations associated with PROTAC complex chemical structure. Designing chameleonic PROTACs capable of adapting their conformation and properties to the environment presents a viable opportunity. This presentation outlines our strategy for predicting chameleonicity using an innovative set of computational methods, experimentally validated with the in-house developed Chamelogk descriptor.

PROTACs are a rapidly evolving modality, currently sparking great excitement within the pharmaceutical industry. At GSK, we have worked on multiple PROTAC projects where we have found synthesis and optimisation of PROTACs via traditional iterative synthesis to be resource intensive and time-consuming. This talk will highlight the use of high-throughput chemistry and direct-to-biology approaches to expedite the optimisation of PROTACs whilst also assessing novel E3 Ligases for broad PROTAC utility.

Today, only a handful of E3 ligases have been targeted with small molecules. Considering that there are more than 600 E3 ligases, there is a clear mismatch between the number of members of the family and the number of E3 that have been successfully engaged and harnessed by degraders or pharmacologically modulated. This reflects the immaturity of the field, rather than intrinsic ‘undruggability’ of the protein family. Here, I will present a novel approach that combines computational and biophysical techniques to target unexplored E3 ligases.

Disulfide constrained peptides (DCPs) show great potential as templates for drug discovery. We designed DCP phage libraries to discover ligands against proteins of interest. Using the libraries, we developed DCPs binding to Zinc and RING finger 3 (ZNRF3), a membrane-bound E3 ubiquitin ligase that controls Wnt signaling activity. The functional ZNRF-DCPs are potent Wnt signaling pathway agonists and the non-functional ZNRF-DCPs can be used for targeted protein degradation.