Targeted vaccination against the bevacizumab binding site on VEGF using 3D-structured peptides elicits efficient antitumor activity

Abstract

Therapeutic targeting of the VEGF signaling axis by the VEGFneutralizing monoclonal antibody bevacizumab has clearly demonstrated clinical benefit in cancer patients. To improve this strategy using a polyclonal approach, we developed a vaccine targeting VEGF using 3D-structured peptides that mimic the bevacizumab binding site. An in-depth study on peptide optimization showed that the antigen's 3D structure is essential to achieve neutralizing antibody responses. Peptide 1 adopts a clear secondary, native-like structure, including the typical cysteine-knot fold, as evidenced by CD spectroscopy. Binding and competition studies with bevacizumab in ELISA and surface plasmon resonance analysis revealed that peptide 1 represents the complete bevacizumab binding site, including the hairpin loop (β5-turn-β6) and the structure-supporting β2-α2-β3 loop. Vaccination with peptide 1 elicited high titers of cross-reactive antibodies to VEGF, with potent neutralizing activity. Moreover, vaccination-induced antisera displayed strong angiostatic and tumor-growth-inhibiting properties in a preclinical mouse model for colorectal carcinoma, whereas antibodies raised with peptides exclusively encompassing the β5-turn-β6 loop (peptides 15 and 20) did not. Immunization with peptide 1 or 7 (murine analog of 1) in combination with the potent adjuvant raffinose fatty acid sulfate ester (RFASE) showed significant inhibition of tumor growth in the B16F10 murine melanoma model. Based on these data, we conclude that this vaccination technology, which is currently being investigated in a phase I clinical trial (NCT02237638), can potentially outperform currently applied anti-VEGF therapeutics.VEGF | angiogenesis | immunization | protein mimicry | peptide vaccines

Specific humoral response in cancer patients treated with a VEGF therapeutic vaccine under a compassionate use program

“…Despite this, the polyclonal antibody response elicited after immunization blocks the receptor binding domain on natural VEGF as well as the binding site for antigen and RFASE as adjuvant [16]. This VEGF therapeutic vaccine has shown antiangiogenic and antitumor activity in pre-clinical models [15], but discrete results in terms of immunogenicity have been observed in the first cancer patients treated with the vaccine [17].…”

“…This antigen sequence represents the complete Bevacizumab binding site and using RFASE as adjuvant, the vaccine (hVEGF 26-104 /RFASE) induces an immune response with VEGF neutralizing activity and anti-tumor effect [15]. Elicited polyclonal antibody response in addition to its cross-reactivity with human VEGF, have also demonstrated in rats and monkeys its capacity to impair the binding of Bevacizumab to VEGF [15,16], indicating the presence of antibodies that block binding sites on VEGF which have shown to be clinically relevant. This vaccine is being investigated in a phase I open-label clinical trial (NCT02237638), and preliminary results of the first included patients indicated that hVEGF 26-104 /RFASE has a good safety profile.…”

Specific humoral response in cancer patients treated with a VEGF-specific active immunotherapy procedure within a compassionate use program

“…Using RFASE as adjuvant, the vaccine (hVEGF 26-104 /RFASE) induces an immune response with VEGF neutralizing activity and anti-tumor effect [20]. In rats and monkeys immunized with this vaccine candidate, the VEGFspecific polyclonal antibody response has also demonstrated its capacity to impair the binding of bevacizumab to VEGF, suggesting the presence of antibodies that target the same VEGF epitope as bevacizumab [20,21]. This vaccine is being investigated in a phase I open-label clinical trial (NCT02237638), and preliminary results of the first included patients indicated that hVEGF 26-104 / RFASE has a good safety profile.…”

Specific humoral response in cancer patients treated with a VEGF-specific active immunotherapy procedure within a compassionate use program.

“…This antigen sequence represents the complete bevacizumab binding site. Using RFASE as adjuvant, the vaccine (hVEGF 26-104 /RFASE) induces an immune response with VEGF neutralizing activity and anti-tumor effect [20]. In rats and monkeys immunized with this vaccine candidate, the VEGF-specific polyclonal antibody response has also demonstrated its capacity to impair the binding of bevacizumab to VEGF, suggesting the presence of antibodies that target the same VEGF epitope as bevacizumab [20,21].…”

“…Using RFASE as adjuvant, the vaccine (hVEGF 26-104 /RFASE) induces an immune response with VEGF neutralizing activity and anti-tumor effect [20]. In rats and monkeys immunized with this vaccine candidate, the VEGF-specific polyclonal antibody response has also demonstrated its capacity to impair the binding of bevacizumab to VEGF, suggesting the presence of antibodies that target the same VEGF epitope as bevacizumab [20,21]. This vaccine is being investigated in a phase I openlabel clinical trial (NCT02237638), and preliminary results of the first included patients indicated that hVEGF 26-104 /RFASE has a good safety profile.…”