CIGB-247 is a novel cancer therapeutic vaccine that uses a mutated form of human vascular endothelial growth factor (VEGF) as antigen in combination with the oil-free adjuvant VSSP (very small sized proteoliposomes of Neis- seria meningitidis outer membrane). The vaccine was designed to affect tumor neo-vascularization and tumor cell viability by eliciting antibodies that block the interaction of VEGF and its receptors in activated endothelial cells, as well as specific cytotoxic T cells that can directly destroy tumor and tumor stroma cells producing VEGF. Our previ- ous experimental studies with CIGB-247 in mice, in which VEGF shares an 87% homology to the human molecule, have shown that the vaccine has anti-tumoral and anti-metastatic activity, and produces anti-VEGF antibodies and a specific T cell cytotoxic response against tumor cells. Herein we extend the immunogenicity and safety studies of CIGB-247 in mice, rats, rabbits and non-human primates. All the species develop antigen-specific IgG antibodies able to block the interaction of VEGF and VEGF receptor 2 in an ELISA assay. Purified IgG from CIGB-247 immunized monkey sera effectively impair human microvascular endothelial cells' proliferation and capillary-like structures for- mation in Matrigel TM . In monkeys and mice, DTH and direct cell cytotoxicity experiments suggest that specific T cell responses are elicited after vaccination. Immunization with CIGB-247 does not affect animal behavior, hematology counts, blood biochemistry or histology of critical organs. Skin deep wound healing was not affected in vaccinated rats and monkeys. Altogether, these results support further clinical development of CIGB-247 therapeutic cancer vaccine, and shed light on the potential mechanisms underlying its effects.
The phase II neo-adjuvant clinical trial ICORG10-05 (NCT01485926) compared chemotherapy in combination with trastuzumab, lapatinib or both in patients with HER2+ breast cancer. We studied circulating immune cells looking for alterations in phenotype, genotype and cytotoxic capacity (direct and antibody-dependent cell-mediated cytotoxicity (ADCC)) in the context of treatment response.Peripheral blood mononuclear cells (PBMCs) were isolated from pre- (n = 41) and post- (n = 25) neo-adjuvant treatment blood samples. Direct/trastuzumab-ADCC cytotoxicity of patient-derived PBMCs against K562/SKBR3 cell lines was determined ex vivo. Pembrolizumab was interrogated in 21 pre-treatment PBMC ADCC assays. Thirty-nine pre-treatment and 21 post-treatment PBMC samples were immunophenotyped. Fc receptor genotype, tumour infiltrating lymphocyte (TIL) levels and oestrogen receptor (ER) status were quantified.Treatment attenuated the cytotoxicity/ADCC of PBMCs. CD3+/CD4+/CD8+ T cells increased following therapy, while CD56+ NK cells/CD14+ monocytes/CD19+ B cells decreased with significant post-treatment immune cell changes confined to patients with residual disease. Pembrolizumab-augmented ex vivo PBMC ADCC activity was associated with residual disease, but not pathological complete response. Pembrolizumab-responsive PBMCs were associated with lower baseline TIL levels and ER+ tumours.PBMCs display altered phenotype and function following completion of neo-adjuvant treatment. Anti-PD-1-responsive PBMCs in ex vivo ADCC assays may be a biomarker of treatment response.
Two phase I clinical trials were conducted to evaluate, among other parameters, the humoral response elicited by a vascular endothelial growth factor (VEGF)-based therapeutic vaccine in cancer patients with advanced solid tumors. VEGF reduction was studied using an indirect methodology named as “Platelet VEGF”. This methodology is based on the estimation of VEGF within platelets by subtracting the plasma VEGF level from the serum level and dividing this by the platelet count, and then this latter expression is additionally corrected by the hematocrit. However, there is broad debate, whether serum or plasma VEGF or platelet-derived VEGF measurements is the most appropriate strategy to study the changes that occur on ligand bioavailability when patients are submitted to a VEGF-based immunotherapy.The current research is a retrospective study evaluating the changes on VEGF levels in serum and plasma as well as platelet-derived measurements. Changes in VEGF levels were related with the humoral response seen in cancer patients after an active immunotherapy with a VEGF-based vaccine. The present study indicates that “Platelet VEGF” is the most reliable methodology to investigate the effect of VEGF-based immunotherapies on ligand bioavailability. “Platelet VEGF” was associated with those groups of individuals that exhibited the best specific humoral response and the variation of “Platelet VEGF” showed the strongest negative correlation with VEGF-specific IgG antibody levels. This methodology will be very useful for the investigation of this VEGF-based vaccine in phase II clinical trials and could be applied to immunotherapies directed to other growth factors that are actively sequestered by platelets.
CIGB-247, a VEGF-based vaccine, was studied in a clinical trial. This advance demands the refinement of the methodologies for assessment of vaccine immune responses. This study aimed to improve the performance of ELISAs for detecting IgG antibodies against human VEGF and the blocking activity of the serum to inhibit the VEGF/VEGFR2 interaction. The best experimental conditions were established through the evaluation of several blocking buffers, immobilization surfaces, and plate suppliers using human sera as test samples. As a result, two controlled ELISAs were used in testing of elicited immune response against VEGF in patients immunized with CIGB-247.
CIGB-247, a VSSP-adjuvanted VEGF-based vaccine, was evaluated in a phase I clinical trial in patients with advanced solid tumors (CENTAURO). Vaccination with the maximum dose of antigen showed an excellent safety profile, exhibited the highest immunogenicity and was the only one showing a reduction on platelet VEGF bioavailability. However, this antigen dose level did not achieve a complete seroconversion rate in vaccinated patients. These clinical results led us to the question whether a "reserve" of untapped immune response potential against VEGF could exist in cancer patients. To address this matter, CENTAURO-2 clinical trial was conducted where antigen and VSSP dose scale up were studied, and also incorporated the exploration of aluminum phosphate as adjuvant. These changes were made with the aim to increase immune response against VEGF. The present study reports the characterization of the humoral response elicited by CIGB-247 from the combining of different antigen doses and adjuvants. Cancer patients were immunologically monitored for approximately 1 year. Vaccination with different CIGB-247 formulations exhibited a very positive safety profile. Cancer patients developed IgM, IgG or IgA antibodies specific to VEGF. Elicited polyclonal antibodies had the ability to block the interaction between VEGF and its receptors, VEGFR1 and VEGFR2. The highest humoral response was detected in patients immunized with 800 μg of antigen + 200 μg of VSSP. Off-protocol long-term vaccination did not produce negative changes in humoral response. Vaccination with a human VEGF variant molecule as antigen in combination with VSSP or aluminum phosphate is immunogenic. The results of this study could contribute to the investigation of this vaccine therapy in an adequately powered efficacy trial. Trial registration number: RPCEC00000155. Cuban Public Clinical Trial Registry. Date of registration: June 06, 2013. Available from: http://registroclinico.sld.cu/ .
CIGB-247 is a vascular endothelial growth factor (VEGF)-based active immunotherapy and it is currently under investigation for cancer treatment. This specific active immunotherapy encompasses two vaccine candidates that use a human VEGF variant molecule as antigen, in combination with two clinically tested adjuvants: VSSP or aluminum phosphate. CIGB-247 has been evaluated in patients with advanced solid tumors, recruited in two phase I clinical trials, and it has been shown to be safe and immunogenic by activating both cellular and humoral immune responses against human VEGF. The immunization induces specific IgG antibodies, and also shows as effect, the reduction of free-VEGF levels within platelets (platelet-derived free VEGF). The production of systemic IgG antibodies and the presence of VEGF in another compartment, almost exclusively within platelets, have arisen some questions about this effect detected in the vaccinated-cancer patients. Based on some relevant published works about platelet endocytosis and VEGF pharmacodynamics during bevacizumab treatment as well as the phase I clinical data of CIGB-247, this investigation aims to hypothesize and analyze the potential mechanisms involved in the reduction of platelet-derived free VEGF as a result of vaccination with CIGB-247.Abbreviations: FcγR: Fc gamma receptors; IC: immune complexes; VEGF: vascular endothelial growth factor; VEGFR1: vascular endothelial growth factor receptor 1; VEGFR2: vascular endothelial growth factor receptor 2.
Abstract Background: CIGB-247 is a cancer therapeutic vaccine that uses as antigen a variant of human vascular endothelial growth factor (VEGF) mixed with the bacterial-derived adjuvant VSSP. This VEGF vaccine has been evaluated in phase I clinical trials CENTAURO and CENTAURO-2, showing to be safe and immunogenic in advanced cancer patients selected under well-defined and controlled clinical conditions. Surviving patients were submitted to monthly re-immunizations and some of them showed objective clinical benefits. These observations led us to initiate a compassionate use program of CIGB-247 in patients who do not meet entry criteria applied for CENTAURO and CENTAURO-2 clinical trials. Results: This report shows the characterization of the humoral response elicited after vaccination with 400 µg of antigen combined with 200 µg of VSSP in cancer patients representative of the Cuban real clinical practice setting. Polyclonal antibody response was specific to VEGF, and showed no cross reactivity with other VEGF family members like VEGF-C and VEGF-D. Specific IgM, IgA and IgG antibodies detected in the serum of vaccinated patients were able to block the binding of VEGF to its receptors VEGFR1 and VEGFR2. Serum-purified IgG fraction exhibited all these properties. For the first time, there is experimental evidence of the presence of polyclonal antibodies directed to clinically relevant epitopes on VEGF. These elicited antibodies impaired the high affinity interaction between VEGF and monoclonal antibody Bevacizumab, an antiangiogenic drug approved in combination with chemotherapy for the treatment of different tumors. This investigation also shows preliminary evidences of safety and immunogenicity of CIGB-247 in cancer patients under clinical conditions not yet explored. Conclusions: CIGB-247 was immunogenic in a broader patient population, and induced Bevacizumab-like polyclonal antibodies, indicating that the VEGF-specific antibody response could have a potentially relevant clinical activity.
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