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Published on: June 19, 2014
The characterization of variable new antigen receptors targeting FAP isolated from a novel immunized library
Gihan S Gunaratne1, Joseph P Gallant1, Kendahl L Ott1,2
1Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
Abstract:
Cancer-associated fibroblasts (CAFs) in the stroma of solid tumors promote an immunosuppressive tumor microenvironment (TME) that drives resistance to therapies. The expression of the protease fibroblast activation protein (FAP) on the surface of CAFs has made FAP a target for the development of therapies to mitigate immunosuppression. Relatively few biologics have been developed for FAP and none have been developed that exploit the unique properties of Variable New Antigen Receptors (VNARs) from shark immunoglobulins. Through the direct immunization of a nurse shark with FAP, we created a large anti-FAP VNAR phage display library. This library allowed us to identify a suite of anti-FAP VNARs through traditional biopanning and by an in silico approach that did not require any affinity maturation. We investigated four VNAR-Fc fusion proteins for theranostic properties and found that all four recognized FAP with high affinity and were rapidly internalized by FAP-positive cells. As a result, the VNAR-Fc constructs were effective antibody-drug conjugates in vitro when attached to an anti-mitotic payload and were able to localize to FAP-positive xenografts in vivo by positron emission tomography. Our findings establish VNAR-Fc constructs as a versatile platform for theranostic development that could yield innovative cancer therapies targeting the TME.
Insights
Shark-derived Variable New Antigen Receptors (VNARs) targeting fibroblast activation protein (FAP) show promise for cancer therapy. These VNAR-Fc constructs effectively target FAP-positive tumors for drug delivery and imaging.
Area of Science:
- Biotechnology
- Immunology
- Oncology
Background:
- Cancer-associated fibroblasts (CAFs) create an immunosuppressive tumor microenvironment (TME) hindering cancer therapies.
- Fibroblast activation protein (FAP) expressed by CAFs is a therapeutic target to overcome treatment resistance.
- Variable New Antigen Receptors (VNARs) from sharks offer unique therapeutic potential.
Purpose of the Study:
- To develop novel anti-FAP VNAR-Fc fusion proteins for cancer theranostics.
- To evaluate the efficacy of VNAR-Fc constructs as antibody-drug conjugates and imaging agents.
Main Methods:
- Generation of an anti-FAP VNAR phage display library via shark immunization.
- Identification of anti-FAP VNARs using biopanning and in silico methods.
- Characterization of VNAR-Fc fusion proteins for FAP binding, internalization, and theranostic applications.
Main Results:
- Four anti-FAP VNAR-Fc constructs demonstrated high-affinity FAP recognition and rapid internalization by FAP-positive cells.
- VNAR-Fc constructs served as effective antibody-drug conjugates in vitro when conjugated to an anti-mitotic payload.
- VNAR-Fc constructs successfully localized to FAP-positive xenografts in vivo, enabling positron emission tomography imaging.
Conclusions:
- VNAR-Fc constructs represent a versatile platform for developing innovative cancer therapies targeting the TME.
- These constructs hold potential for dual therapeutic and diagnostic applications in oncology.
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