An ultra-high-affinity small organic ligand of fibroblast activation protein for tumor-targeting applications
Menée in vitro et à l'aide de modèles murins de tumeur, cette étude met en évidence l'intérêt thérapeutique d'un ligand organique de petite taille présentant une forte affinité pour la protéine d'activation des fibroblastes
Fibroblast activation protein (FAP) has recently emerged as a tumor-associated antigen with abundant and selective expression in the majority of human solid malignancies. To the best of our knowledge, OncoFAP is the highest-affinity small organic FAP ligand reported to date, with a dissociation constant of 680 pM, as measured by fluorescence polarization. Upon intravenous administration, both fluorescent and radiolabeled OncoFAP derivatives exhibited a rapid and selective accumulation in FAP-positive tumors, sparing normal tissues. OncoFAP was also used as a modular component for the generation of therapeutic products, enabling the targeted delivery of a potent beta-emitter (lutetium-177), of fluorescein-specific chimeric antigen receptor (CAR) T cells or of highly cytotoxic auristatin derivatives to FAP-positive tumors in vitro and in vivo.We describe the development of OncoFAP, an ultra-high-affinity ligand of fibroblast activation protein (FAP) for targeting applications with pan-tumoral potential. OncoFAP binds to human FAP with affinity in the subnanomolar concentration range and cross-reacts with the murine isoform of the protein. We generated various fluorescent and radiolabeled derivatives of OncoFAP in order to study biodistribution properties and tumor-targeting performance in preclinical models. Fluorescent derivatives selectively localized in FAP-positive tumors implanted in nude mice with a rapid and homogeneous penetration within the neoplastic tissue. Quantitative in vivo biodistribution studies with a lutetium-177–labeled derivative of OncoFAP revealed a preferential localization in tumors at doses of up to 1,000 nmol/kg. More than 30% of the injected dose had already accumulated in 1 g of tumor 10 min after intravenous injection and persisted for at least 3 h with excellent tumor-to-organ ratios. OncoFAP also served as a modular component for the generation of nonradioactive therapeutic products. A fluorescein conjugate mediated a potent and FAP-dependent tumor cell killing activity in combination with chimeric antigen receptor (CAR) T cells specific to fluorescein. Similarly, a conjugate of OncoFAP with the monomethyl auristatin E-based Vedotin payload was well tolerated and cured tumor-bearing mice in combination with a clinical-stage antibody-interleukin-2 fusion. Collectively, these data support the development of OncoFAP-based products for tumor-targeting applications in patients with cancer.All study data are included in the article and/or SI Appendix.