An NTCP-mediated liver-targeting chimeras (NTLiverTac) design strategy and its application to hepatoblastoma models

Hepatoblastoma (HB) has attracted much attention due to its high recurrence rate, and its first- and second-line chemotherapeutic agents have severe neurotoxicity, cardiotoxicity, and hepatorenal dysfunction. To enhance the liver-targeting efficiency, we proposed an NTCP-mediated liver-targeting chimeras (NTLiverTac) design strategy, which utilized the PROTAC molecule to couple with the Na⁺-taurocholate co-transporting polypeptide (NTCP) ligand to enhance cell selectivity through NTCP-mediated endocytosis. As a proof-of-concept, we selected cholic acid as its ligand, conjugated it with sorafenib and E3 ligase ligand, and synthesized 25 NTLiverTacs through two generations of optimization. We evaluated the anti-proliferation activity and PDE6D degradation efficiency of NTLiverTacs in HuH-6 cells, a human HB cell line that was characterized by NTCP high expression. Among them, S2C2M2 showed an obvious anti-proliferative effect with the IC₅₀ value of 7.46 ± 0.70 μM in HuH-6 cells and could effectively induce phosphodiesterase 6D (PDE6D) degradation in proteasome-dependent and NTCP-dependent manner. Mechanism research revealed that S2C2M2 effectively inhibited the PDE6D-dependent KRAS trafficking, modulated KRAS distribution and activity, and inhibited the oncogenic signaling cascade associated with KRAS. Our work demonstrated the practicality and efficiency of the NTLiverTac strategy and offered a promising avenue for degraders targeting other pathogenic proteins relevant to HB.