Abstract 1816: In silico design of novel multitarget small molecule inhibitor LCI139 for the treatment of PTEN-mutant endometrial carcinoma

Abstract Background: Previously we described multitarget CDK4/6-CDK9 inhibitor, LCI133 for the treatment of endometrial carcinoma (EC). We have optimized LCI133’s chemical properties to increase PI3K p110α potency to better target epithelial-derived cancers, resulting in nanomolar potent LCI139. We characterized LCI139’s in vitro potency, target specificity, activity in in vitro EC models, safety against normal cell lines. Methods: LCI139’s chemical structure was determined using nuclear magnetic resonance and high-resolution mass spectrometry. Specific target inhibition was assessed by cell-free kinase hotspot/lipid kinase assay and selectivity profile. LCI139 (0. 001-10μM) was screened against EC cell lines AN3CA, RL95-2, Ishikawa, KLE, HEC-1-A and -B for 48 hours; IC50 values determined by CellTiter-Glo Assay. EC cells were treated with LCI139 or single agent control for 24 hours and stained with Annexin V/7-AAD to assess apoptosis by cytometer. Representative PTEN wildtype (HEC-1) and mutant (AN3CA) EC cell lines were chosen for mechanistic studies and treated 6 to 24 hours with multitarget or single agent inhibitor. RNA was isolated to determine gene expression by qRT-PCR, cells were stained with Vybrant DyeCycle Violet to determine cell cycle arrest by cytometer, or cellular lysates were prepared for Western blot (WB). Results: LCI139’s has a molecular weight of 502. 57Da and is a highly potent PI3Kα-CDK4/6-CDK9 inhibitor by cell-free kinase assays: 0. 070µM (PI3Kα), 0. 461µM (PI3Kγ), 0. 214µM (PI3Kδ), 0. 0015µM (CDK4), 0. 0036µM (CDK6), 0. 000039µM (CDK9). KINOMEscan revealed a favorable S (35) selectivity score of 0. 221 screened against 403 non-mutant kinases. PTEN mutant AN3CA (IC50 243. 6nM), RL95-2 (IC50 22. 8nM), Ishikawa (IC50 9. 8nM) had nanomolar LCI139 IC50 values, while PTEN-wild type cell lines were insensitive up to 10μM; confirmed by dose-dependent apoptosis and colony-forming assays. WB revealed LCI139 treatment ablated MCL-1 expression, decreased phosphorylation of AKT, Rb, Rpb1 (Ser2), induced significant amounts of cPARP. MCL-1 ablation correlated to decreased Mcl1 expression (p0. 0010) assessed 6 hours post treatment. LCI139 generated heterogenous cell line specific effects on cell cycle progression and arrest. LCI139 displayed a favorable toxicity profile against normal human kidney cells (HEK-293) compared to single agent controls. Conclusions: Triple PI3K-CDK4/6-CDK9 inhibitor, LCI139, is nanomolar potent against PTEN mutant EC cell lines and displays decreased toxicity compared with CDK9 inhibitor reference compounds, AZD4573 and flavopiridol. Our results merit further mechanistic dissection of PTEN interaction with PI3K pathway signaling, cell cycle machinery, CDK9-mediated transcriptional control. These data support extensive in vivo potency, toxicity, PK/PD studies to assess LCI139’s clinical utility in treating EC. Citation Format: Vaidehi Mujumdar, Ritchie Delara, Hailey Dryden, Dhananjaya Pal, Krishnaiah Maddeboina, Page Mangum Arditti, Bharath Yada, Robert Wendel Naumann, Yovanni Casablanca, Erin Crane, Jubilee Brown, Donald Durden, Cody McHale. In silico design of novel multitarget small molecule inhibitor LCI139 for the treatment of PTEN-mutant endometrial carcinoma 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 (6Suppl): Abstract nr 1816.