Abstract 3016: Therapeutic efficacy of a novel combination of ck2 inhibitor cx-4945 with cytotoxic therapy in neuroblastoma preclinical models

Abstract Introduction: Neuroblastoma is a pediatric cancer of the sympathetic nervous system, which is often diagnosed at a clinically advanced stage with primary or acquired resistance to conventional chemotherapy. Protein Kinase CSNK2A1 (CK2) is an intrinsically active, ubiquitously present serine-threonine kinase overactive in various solid cancers, including neuroblastoma (NBL). Recurrent genetic alteration in CK2 is not detected in NBL. CX-4945 (Silmitasertib) is an ATP-competitive CK2 selective small-molecule irreversible inhibitor of CK2 with inhibition constant (Ki) values in the low nanomolar range and high selectivity (49 of 250 kinases) versus other kinases. CX-4945 has shown in vivo anti-tumor activity in solid tumors and leukemia has favorable pharmacokinetic properties and is well-tolerated in human subject studies. Here, we report the therapeutic efficacy of CX-4945 in combination with temozolomide and irinotecan NBL preclinical models. Methods: The susceptibility of NBL cell lines with and without MYCN amplification was tested against CX-4945. We measured CK2 mRNA expression, protein level, and CK2 kinase activity in NBL cell lines and NBL PDX samples (n=18). CK2 knockdown was achieved in SMS-KCNR and SK-N-BE2 cell line using shRNA against CK2α and phenotype was assessed using cell viability assay, apoptosis, spheroid formation, migration, invasion assay. Cells were also injected into the flank of athymic mice to assess engraftment potential. We performed gene expression analysis using RNA sequencing of CX-4945 treated and gene knockdown NBL cells. MYCN-NBL cell line-derived subcutaneous model was developed in athymic mice. Mice were treated with a combination of Irinotecan (IRN) and temozolomide (TMZ) with and without CX-4945 for up to 28 days. Cohorts were followed for tumor growth and survival. Results: CK2α shRNA silencing in NBL cell lines resulted in significantly reduced proliferation, increased apoptosis, reduced spheroid formation, and reduced migratory potential. The IC50 of CX-4945 (3-6uM) in NBL cell lines also showed synergy with the other standard chemo drugs, Temozolomide and Irinotecan. Gene expression analysis showed a decrease in the expression of several known MYC target proteins. The cohort receiving IRN + TMZ with CX-4945 showed significant tumor inhibition (50-60%) and prolonged survival time compared to the TMZ+IRN group. Conclusion: Protein kinase CK2 is intrinsically active and negatively impacts survival in HR-NBL patients. In MYCN-NBL xenograft models, CX-4945 is well tolerated and shows superior therapeutic efficacy when combined with cytotoxic drugs Irinotecan and temozolomide. The ongoing Phase 1/II study is evaluating the safety, tolerability, and efficacy of combining CX-4945 with TMZ+IRN in relapsed refractory NBL patients ((NCT06541262). Citation Format: Marudhu Pandiyan Shanmugam, Muhammed Danial, Rajesh Rajaiah, Koby Duke, Katie Mercer, Yasin Uzun, Sinisa Dovat, Giselle Saulnier Sholler, Chandrika Gowda Behura. Therapeutic efficacy of a novel combination of ck2 inhibitor cx-4945 with cytotoxic therapy in neuroblastoma preclinical models [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 3016.