Abstract 5208: The use of human small intestinal organoids as a preclinical screening tool to assess gastrointestinal toxicity induced by CDK inhibition

Dysregulated cell division is one of the most important hallmarks of cancer. Cyclindependent kinases (CDKs), involved in cell cycle regulation, have been identified to be overexpressed in many cancers. The development of CDK inhibitors has emerged as a promising and novel approach for cancer treatment in both solid and hematological malignancies. However, first generation pan-CDKIs, which initially showed reliable results in vitro and in Phase I trials, lacked selectivity. Many were discontinued due to adverse effects, including Gastrointestinal (GI) toxicity, and reduced efficacy in vivo. The development of specific CDKIs, which can provide optimum therapeutic outcomes with good efficacy and reduced off-target effects are therefore needed. In this study, we have used a human small intestinal organoid model (adapted from Sato et al. 2009), as a screening tool to predict GI toxicity and subsequent mucosal regeneration. The culture conditions have been designed to mimic the stem cell niche and allow cell differentiation and proliferation to occur. All intestinal lineages were present in the organoids and resembled the frequency of linage observed in vivo. The effect of several clinically available CDKIs, such as Dinaciclib, Palbociclib and Abemaciclib, some of them known to induce GI toxicity were assessed. Treatment was applied on Day 3 after plating of fragments, when the organoid structures had formed. On Day 5, the number of dead, viable unbranched and branched organoids were counted and IC50 values were calculated. Furthermore, morphometric analysis of acquired images were performed. To compare the toxicity profiles on a molecular level, organoids were harvested for RNA-seq. The second generation pan-CDK inhibitor Dinaciclib was the most toxic. Whereas Palbociclib was the least toxic compound within the human organoid assay, reflecting clinical data that shows the lowest incidence of severe diarrhea. We conclude that organoids are a predictive preclinical model that can be used to identify potential on-target, off-tissue GI toxicities induced by novel therapeutics such as CDKIs. Toxicity and mechanism of action (MOA) can all be addressed in vitro to potentially reduce in vivo experimentation. Citation Format: Frida Ponthan, Thomas Kedward, Valentina Ubertini, Gary Beale, Cath Booth. The use of human small intestinal organoids as a preclinical screening tool to assess gastrointestinal toxicity induced by CDK inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5208.