Developing oral drugs targeting the insulin receptor using 'Beyond Rule of 5' DEL libraries - Insulin is a life-saving therapy for the more than 8 million Americans who use insulin injections to manage diseases, including diabetes. However, management requires multiple, daily insulin injections and poses risks like hypoglycemia due to poor compliance. Oral insulin would transform treatment for these patients, yet intense efforts to develop oral insulin have failed clinically due to low oral bioavailability, rendering candidates ineffective at preventing hypoglycemia. With no new chemical entity (NCE) insulin receptor (IR) agonists available for oral administration, the IR is considered orally undruggable. IR is a complex extracellular drug target with flat, hydrophobic surfaces that are difficult to selectively engage. Standard high-throughput screening (HTS) approaches for oral insulin agonists screen relatively small libraries that meet Lipinsky’s “Rule of Five” for identifying bioavailable compounds, limiting the discovery of novel, potent agonists. Additionally, standard peptide screens include only peptides with canonical amino acids, which are easily cleaved by native biological enzymes in vivo. Thus, novel screening approaches that expand the pool of potential compounds and integrate peptides and macrocyclic peptides with non-natural amino acids will illuminate promising oral IR agonists. To overcome the limitations associated with identifying hits for undruggable targets such as IR, a custom, unique DNA-encoded library (DEL) was built with ~180 billion compounds. These compounds include “beyond Rule of Five” compounds such as large compounds (500–800 Da) and macrocyclic and linear peptides (7–16 amino acids) designed to maximize binding surface, while lowering polar surface area and conformational restriction. Importantly, the peptides include non-natural amino acids, non-natural backbones, and reversed stereochemistry, making them more plasma stable than peptides with canonical amino acids. As screening this DEL library has generated actionable hits for other undruggable targets, it is hypothesized that hits from this completed DEL screen will yield unique and selective IR agonists that mimic insulin’s therapeutic effects while minimizing mitogenic signaling to allow broader exploration of oral potential beyond insulin analogs. Leveraging multiple hits with IR agonism from this DEL screen, Aim 1 will characterize and validate DEL hits targeting IR using surface plasmon resonance, ELISA, and western blot. Aim 2 will optimize peptide and small molecule hits using structure-activity relationship studies, stability profiling, and functional assays to generate preliminary lead candidates. Aim 3 will evaluate bioavailability, IR activation, glucose regulation, pharmacokinetics/pharmacodynamics, and safety to determine the best candidates for further development. This work is expected to identify multiple peptide and small molecule IR agonist NCEs with potential for optimization without losing potency. If successful, this work will revolutionize treatment of diseases that require burdensome insulin injections. Additionally, this work will establish a new paradigm for using this unique DEL platform to quickly identify and translate novel drugs for other “undruggable” targets.
