Specific humoral and cellular immune responses in cancer patients undergoing chronic immunization with a VEGF-based therapeutic vaccine.

CIGB-247 is a cancer therapeutic vaccine, based on recombinant modified human vascular endothelial growth factor (VEGF) as antigen, in combination with the adjuvant VSSP, a bacterially-derived adjuvant. The vaccine have demonstrated efficacy in several murine malignancy models. These studies supported the rationale for a phase I clinical trial where safety, tolerance, and immunogenicity of CIGB-247 was studied in patients with advanced solid tumors at three antigen dose level. Surviving individuals of this clinical trial were eligible to receive off-trial voluntary re-immunizations. The present work is focus in the immunological follow up of these patients after approximately three years of immunizations, without additional oncological treatments. Long term vaccination was feasible and safe. Our results indicated that after sustained vaccination most of the patients conserved their seroconversion status. The specific anti-VEGF IgG titer diminished, but in all the cases keeps values up from the pre-vaccination levels. Continued vaccination was also important to produce a gradual shift in the anti-VEGF IgG response from IgG1 to Ig4. Outstanding, our results indicated that long-term off-trial vaccination could be associated with the maintaining of one reserve of antibodies able to interfere with the VEGF/Receptor interaction and the production of IFNγ secretion in CD8+ cells. The results derived from the study of this series of patients suggest that long term therapeutic vaccination is a feasible strategy, and highlight the importance of continuing the clinical development program of this novel cancer therapeutic vaccine candidate. We also highlight the future clinical applications of CIGB-247 in cancer and explain knowledge gaps that future studies may address. Registration number and name of trial registry: RPCEC00000102. Cuban Public Clinical Trial Registry (WHO accepted Primary Registry). Available from: http://registroclinico.sld.cu/.