Abstract 1860: NP-ALT, a liposomal:peptide drug, blocks p27Kip1 phosphorylation to cause cell death in CDK4i-resistant breast cancer

Abstract

Abstract Resistance to cyclin D-cdk4/6 inhibitors (CDK4/6i) is frequently caused by compensatory CDK2 activity. We have developed a novel strategy to kill CDK4i resistant tumor cells using a therapeutic liposomal:peptide formulation, NP-ALT, to inhibit the tyrosine phosphorylation of p27Kip1(CDKN1B), which in turn inhibits both CDK4/6 and CDK2. IpY is specific for p27, and this reduces toxicity relative to that seen with the small molecule ATP-competitive CDK4/6i or CDK2i. NP-ALT blocks DNA replication in HR+ breast cancer (BC) cells and mouse models, but unlike CDK4/6i or CDK2i treatment, it induces ROS-dependent necroptosis to kill the tumor cells. This RIPK1/RIPK3-dependent cell death is more specific for HR+ lineages, but the combination of NP-ALT and palbociclib in TNBC cells causes synergy to induce necroptosis. We found that NP-ALT was still able to induce necroptosis in cell lines resistant to palbociclib, including those harboring genetic perturbations detected clinically in patients resistant to palbociclib. HR+ cell lines engineered to overexpress CDK6, FGFR, cyclin E, or cyclin D or ones that have loss of FAT1 or RB were still sensitive to NP-ALT. We tested other CDK2i, including CYC065, a CDK2/9 inhibitor and PF-06873600, a CDK4/6/2 inhibitor, and and found that while they were able to block DNA replication, only NP-ALT was able to induce ROS-dependent death in the resistant lines. We have shown that IpY reduces tumor volumes in resistant in vivo models as well, without causing adverse effects. Thus, NP-ALT and p27 targeting has several differentiators, which might provide clinical advantages: a) its low toxicity due to the tight specificity of the peptide for the p27 target and b) its ability to kill tumor cells as opposed to just causing cytostasis. Concarlo is currently developing NP-ALT into a therapeutic lead for the treatment of drug-resistant breast cancer. Citation Format: Stacy Wister Blain, Arianna Chand, Lina Pedraza-Ortiz, Allison VanInwegen, Lingyu Yan, Yun Wu, Grace Chen, Irina Jilishitz. NP-ALT, a liposomal:peptide drug, blocks p27Kip1 phosphorylation to cause cell death in CDK4i-resistant breast cancer [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 1860.