[177Lu]Lu-FS-86

[177Lu]Lu-FS-86 is a stroma-targeted radiopharmaceutical composed of the beta-emitting radioisotope Lutetium-177 conjugated to the ligand FS-86, which targets fibroblast activation protein (FAP). FAP is highly expressed on cancer-associated fibroblasts (CAFs) within the tumor microenvironment. Developed by researchers at the Chinese Academy of Medical Sciences and Peking Union Medical College, [177Lu]Lu-FS-86 is intended for stroma-targeted radionuclide therapy (STRT). Preclinical studies, including those presented at AACR 2026, demonstrate that the therapeutic efficacy of this agent is significantly influenced by the spatial distribution of CAFs and tumor cells. Specifically, "infiltrative" spatial patterns allow for more homogeneous dose deposition and increased cell death compared to "surrounding" patterns, where CAFs form a protective barrier. The drug has been evaluated in models of medullary thyroid carcinoma, as well as lung, liver, and breast cancers.