Development of PD-L1 Targeting Small-Molecule Immunotheranostic Agents for Personalized Antitumor Immunotherapy

Immune checkpoint blockade targeting PD-1/PD-L1 has transformed cancer treatment but faces challenges such as low response rates and a lack of reliable biomarkers. To address these issues, we developed a novel small-molecule immunotheranostic agent, [¹⁸F]LG-8, and its therapeutic counterpart LG-8, which share identical structures to ensure consistent biodistribution. [¹⁸F]LG-8 PET specifically quantified PD-L1 in murine melanoma (B16-F10) and lung carcinoma (LLC) models. LG-8 exhibited potent antitumor efficacy in B16-F10 tumors with high PD-L1 uptake but not in LLC models with low PD-L1 expression, confirming the predictive value of the diagnostic scan. Furthermore, we implemented an individualized chemo-immunotherapy strategy guided by [¹⁸F]LG-8 PET imaging, where cisplatin pretreatment enhanced PD-L1 expression in a subset of LLC tumors, enabling effective LG-8 treatment only in mice with elevated PD-L1 levels. This theranostic approach integrates precise diagnosis and immunotherapy within a unified molecular platform, significantly improving response prediction and advancing personalized cancer immunotherapy.