Abstract 2135: Targeting N-Myc in neuroblastoma cells with selective Aurora kinase A degraders

Abstract Overexpression of the MYCN proto-oncogene is one of the strongest biomarkers for poor prognosis in neuroblastoma patients. N-Myc, encoded by MYCN, is a highly attractive yet “undruggable” target in neuroblastoma drug discovery. N-Myc is a short-lived protein in normal neuronal progenitor cells; however, in MYCN-amplified neuroblastoma cells, overexpressed N-Myc is stabilized by high levels of Aurora kinase A (Aurora-A). Several Aurora-A allosteric modulators have been developed to disassociate N-Myc binding and promote its degradation. These compounds function through a competitive mechanism against N-Myc, and clinical trial results suggest limited efficacy in high-risk neuroblastoma patients where N-Myc is highly expressed. To develop Aurora-A modulators with greater effects in destabilizing N-Myc, targeted degradation of Aurora-A was investigated in this study. First, we developed a highly selective Aurora-A-binding ligand by chemically modifying ribociclib, which targets CDK4/6. Next, a series of potent Aurora-A/N-Myc degraders were developed using proteolysis targeting chimaera (PROTAC) technology. Our lead compound, HLB-0532259, was found to substantially decrease N-Myc levels in neuroblastoma cells following the degradation of Aurora-A with nanomolar potency. Mechanistic studies suggest that HLB-0532259 binds to Aurora-A in an uncompetitive manner with respect to N-Myc, which contributes to its high potency for degrading the Aurora-A/N-Myc pool. Mass spectrometry analysis demonstrates that HLB-0532259 possesses remarkable proteome-wide selectivity for Aurora-A and N-Myc degradation. Further studies have revealed that HLB-0532259 exhibits nanomolar cytotoxicities against a panel of MYCN-amplified neuroblastoma cells, good pharmacokinetic properties, and favorable therapeutic outcomes in a xenograft neuroblastoma mouse model. Taken together, our data strongly support HLB-0532259 as a promising lead compound for neuroblastoma therapy. Citation Format: Jian Tang, Ramkumar Moorthy, Ozlem Demir, Zachary D. Baker, Jordan A. Naumann, Katherine F. Jones, Michael J. Grillo, Ella Haefner, Ke Shi, Michaella J. Levy, Hideki Aihara, Reuben S. Harris, Rommie E. Amaro, Nicholas M. Levinson, Daniel A. Harki. Targeting N-Myc in neuroblastoma cells with selective Aurora kinase A degraders [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2135.