Abstract 4501: First reported PIM kinase degraders: Design, profiling & optimization

Abstract The PIM serine/threonine kinases (PIM1/PIM2/PIM3) are downstream effectors of ABL, JAK2 and Flt-3 oncogenes and are required for tumorigenesis. Overexpression has been reported in hematological and solid tumors, myeloma, lymphoma, leukemia and adenocarcinoma. The first generation of PIM inhibitors to make it to the clinic, including SGI-1776, AZD1208 and PIM447, are known to be pan-PIM inhibitors, while the aim of this project was to identify novel & selective PIM3 inhibitors. To this end, several Hit-finding approaches were employed to rapidly generate novel chemical matter, which were then assessed for their activity against PIM3 using a robust ADP-Glo™ assay. In parallel to this Hit-findings activity, we used AZD1208 scaffold as a starting point to generate PIM3 bifunctional protein degraders and designed a specific screening cascade in order to profile such modalities. The PIM degrader library, synthetized using Automated Robotics Lab, was characterized using ADP-Glo assays. It was then screened on our binding and activity kinase platforms, KINOMEscan® and KinaseProfiler™, and then fully profiled including ternary complex formation with biophysics and in vitro Safety Pharmacology Profiling Panels. One example is the AZD1208 derivate degrader, i.e. EC108154-1, which showed nanomolar range affinity for PIM3 and the E3-ligase CRBN-DDB1, and its affinity range was also confirmed with the ternary complex in SPR and MST-TRIC. This comprehensive screening cascade ensures an in-depth characterization and optimization of protein degraders, with the possibility of monitoring the ternary complex formation with biophysics methods. It is a good illustration of how this combination of tests can be instrumental in selecting the best degraders to progress to the next step of drug discovery. Citation Format: Celine Legros, Paul Ratcliffe, Vanessa Porkolab, Michele Modugno, Olivier Mirguet. First reported PIM kinase degraders: Design, profiling & optimization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4501.