An ultra-high-affinity small organic ligand of fibroblast activation protein for tumor-targeting applications

Abstract

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.

Cancer-Associated Fibroblast Heterogeneity: A Factor That Cannot Be Ignored in Immune Microenvironment Remodeling

“…The modified synthetic consensus FAP DNA vaccine synergized with other tumor antigen-specific vaccine therapies in tumor-bearing mice ( 92 ). Moreover, adoptive transfer of FAP-specific chimeric antigen receptor to T cells proved to be effective in restraining tumor growth in preclinical models ( 93 ). In addition, FAP-targeting oncolytic adenovirus in tumor-bearing mice enhanced anti-tumor immunity by activating endogenous T cells to attack FAP + stromal cells.…”

Fibroblast Activation Protein-α as a Target in the Bench-to-Bedside Diagnosis and Treatment of Tumors: A Narrative Review

“…Results from a phase I clinical study and pharmacokinetic analysis of the humanized anti-FAP antibody (sibrotuzumab) further revealed that it is well tolerated in humans and is specifically concentrated in the tumor stroma, with limited absorption in normal tissues (107). Moreover, Millul et al (106). described a ligand with ultrahigh affinity for FAP (OncoFAP) that is used for precise diagnosis and treatment of FAP + tumors.…”

New Frontiers in Cancer Imaging and Therapy Based on Radiolabeled Fibroblast Activation Protein Inhibitors: A Rational Review and Current Progress

“…The multifunctional RPS-309 could be a useful tool for the study of the relationship between FAPI structure and substrate activity in the future. In addition, an ultra-high-affinity small organic ligand (OncoFAP), a carboxylic acid moiety, for FAP targeting was very recently reported [ 120 ]. The OncoFAP was chemically modified at position 8 on quinoline moiety of the FAPI molecule and further functionalization with the chelator DOTAGA, leading to a FAP-based ligand with a high dissociation constant ( K d ) ranging from 0.68 nM for human FAP to 11.6 nM for murine FAP.…”