LAUSR

The E3 ligase MDM2 controls the tumor suppressor function of p53, which is encoded by the TP53gene. Compounds designed to bind to MDM2 preventing its interaction with p53 restore the ability of p53 to combat the pathogenic processes that underly cancer development. It has become clear from early clinical experience that thrombocytopenia represents an on-target, dose-limiting toxicity that may restrict the therapeutic utility of first-generation MDM2 inhibitors. Dosing less frequently, while maintaining efficacious exposure levels, has been proposed as an approach to mitigate side effects and improve the therapeutic window. In this -Late Breaking- session we present the discovery and preclinical evaluation of BI 907828, a highly potent, orally bioavailable and selective molecule binding to MDM2 and preventing its interaction with p53. The compound was designed to have a long half-life to enable intermittent dosing schedules in the clinic where it showed a manageable safety profile in a Phase Ia/Ib, dose-escalation/expansion study and encouraging signs of antitumor activity in patients with advanced DDLPS and WDLPS. BI 907828 is actively investigated in several clinical trials including the Phase II/III Brightline-1 study that aims to evaluate whether it is superior to doxorubicin in the first-line treatment of advanced/metastatic DDLPS. BI 907828 belongs to the class of spiro-oxindole MDM2-p53 antagonists and was discovered starting from an optimized core structure with improved chemical stability. Structure-based medicinal chemistry optimization including rigidification of the scaffold were key to accomplish the desired profile which was tested preclinically in several in vivo MDM2-amplified xenograft models where treatment with BI 907828 showed efficient tumor growth inhibition and regression. Citation Format: Andreas Gollner, Patrizia Sini, Dorothea Rudolph, Harald Weinstabl, Juergen Ramharter, Ulrike Weyer-Czernilofsky, Bojana Golubovic, Rolf Grempler, Alejandro Pérez Pitarch, Reinhard Sailer, Darryl B. McConnell, Norbert Kraut. BI 907828: A highly potent MDM2-p53 antagonist suitable for intermittent dose schedules [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB003.