Fibroblast Activation Protein Inhibitor Theranostics: Preclinical Combination Treatment.

Fibroblast activation protein (FAP)-radioligand therapy might be effective in some patients without being curative. FAP-radioligands deliver ionizing radiation directly to FAP cancer-associated fibroblasts and, in some cancers, to FAP tumor cells; in addition, they indirectly irradiate FAP cells in tumor tissue via cross-fire and bystander effects. Here, we discuss the potential to improve FAP-radioligand therapy through interfering with DNA damage repair, immunotherapy, and co-targeting cancer-associated fibroblasts. As the molecular and cellular effects of FAP-radioligands on the tumor and its microenvironment have not been investigated yet, we call for future research to close this gap in knowledge, which prevents the development of more effective FAP-radioligand therapies.