Viral-mimicking protein nanoparticle vaccine for eliciting anti-tumor responses.

The immune system is a powerful resource for the eradication of cancer, but to overcome the low immunogenicity of tumor cells, a sufficiently strong CD8(+) T cell-mediated adaptive immune response is required. Nanoparticulate biomaterials represent a potentially effective delivery system for cancer vaccines, as they can be designed to mimic viruses, which are potent inducers of cellular immunity. We have been exploring the non-viral pyruvate dehydrogenase E2 protein nanoparticle as a biomimetic platform for cancer vaccine delivery. Simultaneous conjugation of a melanoma-associated gp100 epitope and CpG to the E2 nanoparticle (CpG-gp-E2) yielded an antigen-specific increase in the CD8(+) T cell proliferation index and IFN-γ secretion by 1.5-fold and 5-fold, respectively, compared to an unbound peptide and CpG formulation. Remarkably, a single nanoparticle immunization resulted in a 120-fold increase in the frequency of melanoma epitope-specific CD8(+) T cells in draining lymph nodes and a 30-fold increase in the spleen, relative to free peptide with free CpG. Furthermore, in the very aggressive B16 melanoma murine tumor model, prophylactic immunization with CpG-gp-E2 delayed the onset of tumor growth by approximately 5.5 days and increased animal survival time by approximately 40%, compared to PBS-treated animals. These results show that by combining optimal particle size and simultaneous co-delivery of molecular vaccine components, antigen-specific anti-tumor immune responses can be significantly increased.

Administration of sulfosuccinimidyl-4-[N-maleimidomethyl] cyclohexane-1-carboxylate conjugated GP100(25-33) peptide-coupled spleen cells effectively mounts antigen-specific immune response against mouse melanoma.

It remains a top research priority to develop immunotherapeutic approaches to induce potent antigen-specific immune responses against tumors. However, in spite of some promising results, most strategies are ineffective because they generate low numbers of tumor-reactive cytotoxic T lymphocytes (CTLs). Here we designed a strategy to enhance antigen-specific immune response via administering sulfosuccinimidyl-4-[N-maleimidomethyl] cyclohexane-1-carboxylate (sulfo-SMCC)-conjugated melanoma tumor antigen GP10025-33 peptide-coupled syngeneic spleen cells in a mouse model of melanoma. We found that infusion of GP10025-33 peptide-coupled spleen cells significantly attenuated the growth of melanoma in prophylactic and therapeutic immunizations. Consistent with these findings, the adoptive transfer of spleen cells from immunized mice to naïve syngeneic mice was able to transfer anti-tumor effect, suggesting that GP10025-33 peptide-specific immune response was induced. Further studies showed that, CD8+ T cell proliferation and the frequency of interferon (IFN)-γ-producing CD8+ T cells upon ex vivo stimulation by GP10025-33 were significantly increased compared to control groups. Tumor antigen, GP10025-23 specific immune response was also confirmed by ELISpot and GP100-tetramer assays. This approach is simple, easy-handled, and efficiently delivering antigens to lymphoid tissues. Our study offers an opportunity for clinically translating this approach into tumor immunotherapy.

Efficacy and safety of ipilimumab in metastatic melanoma patients surviving more than 2 years following treatment in a phase III trial (MDX010-20).

BACKGROUND: In a phase III trial (ClinicalTrials.gov registration ID: NCT00094653), ipilimumab significantly improved survival versus a vaccine control in pretreated patients with metastatic melanoma. Here, we characterize outcomes of those patients who survived ≥ 2 years. METHODS: Patients were randomized (3 : 1 : 1) to receive ipilimumab 3 mg/kg + gp100 vaccine, ipilimumab 3 mg/kg + placebo, or gp100 vaccine alone. Baseline demographic data, duration of survival, responses, and safety among patients with ≥ 2 years' survival were analyzed. RESULTS: Among 676 randomized patients, 474 and 259 patients had at least 2 or 3 years of potential follow-up, respectively, and were eligible for analysis. Among these, 94 (20%) and 42 (16%) survived ≥ 2 and ≥ 3 years, respectively. Survival rates at 2 and 3 years were 25% (24 of 95) and 25% (13 of 53) with ipilimumab alone and 19% (54 of 284) and 15% (24 of 156) with ipilimumab plus gp100. Safety among patients with ≥ 2 years' survival was comparable with the overall study population, with the onset of new ipilimumab-related toxic effect (all grades) reported in 6 of 78 (8%) patients. CONCLUSIONS: Ipilimumab results in survival of ≥ 2 years in one-fifth of pretreated patients with 2 years potential follow-up in a phase III trial. New onset, low-grade events starting after administration of the last dose were infrequent. TRIAL REGISTRATION ID: NCT00094653.

Multi-compartmental vaccine delivery system for enhanced immune response to gp100 peptide antigen in melanoma immunotherapy.

PURPOSE: To develop a multi-compartmental vaccine delivery system for safe and efficient delivery of the gp100 peptide antigen in melanoma immunotherapy. METHODS: Water-in-oil-in-water (W/O/W) multiple emulsion-based multi-compartmental vaccine delivery system containing the gp100 peptide was prepared by a two-step emulsification method. In vivo prophylactic and active immunization effectiveness of the novel squalane oil-containing gp100 vaccine was evaluated in the murine B16 melanoma model and compared with that of an incomplete Freund's adjuvant (IFA)-based vaccine. RESULTS: Morphological evaluation of the W/O/W multiple emulsions showed that the oil-droplets were homogenously dispersed with the gp100 peptide encapsulated in an inner aqueous phase. Immunization with the gp100 peptide delivered in the W/O/W multiple emulsions-based vaccine resulted in increased protection against tumor challenge compared to IFA-based vaccine (p < 0.05, n = 8) signifying induction of enhanced anti-tumor immunity. In addition, serum Th1 cytokine levels and immuno-histochemistry of excised tumor tissues indicated activation and local infiltration of antigen specific cytotoxic T-lymphocytes into and/or surrounding the tumor mass. Moreover, the newly developed vaccine formulation did not induce any overt systemic toxicity. CONCLUSION: Novel W/O/W multiple emulsions-based vaccine efficiently delivers the gp100 peptide antigen to induce cell-mediated anti-tumor immunity and offers an alternate, safe vaccine delivery system.

Safety and immunogenicity of vaccination with MART-1 (26-35, 27L), gp100 (209-217, 210M), and tyrosinase (368-376, 370D) in adjuvant with PF-3512676 and GM-CSF in metastatic melanoma.

The effectivenes of cancer vaccines in inducing CD8(+) T-cell responses remains a challenge, resulting in a need for testing more potent adjuvants. Our objective was to determine the safety and immunogenicity of vaccination against melanoma-related antigens employing MART-1, gp100, and tysosinase paptides combined with the TLR9 agonist PF-3512676 and local granulocyte macrophage-colony stimulating factor in oil emulsion. Using continuous monitoring of safety and a 2-stage design for immunologic efficacy, 20 immune response evaluable patients were targetted. Vaccinations were given subcutaneously on days 1 and 15 per cycle (1cycle=28 d) for up to 13 cycles. Interferon-γ enzyme-linked immunosorbent spot was used as the primary assay measuring the frequency of peripheral antigen-specific CD8(+) T cells at days 50 and 90 compared with baseline (target ≥ 9/20 immunologic responses). Clinical responses were measured by Response Evaluation Criteria In Solid Tumors every 8 weeks. Twenty-two (including 20 immune response evaluable) melanoma patients were enrolled. All had American Joint Committe on Cancer stage IV (5M1a, 6M1b, 11M1c) and most had previously received therapy. Eight had previously treated brain metastases. An average of 3.5 cycles of vaccination per patient was administered. Clinical response data were available for 21 patients. There were 2 partial response and 8 stable disease lasting 2-7 months. One patient with ongoing partial response continued on treatment. At a median follow-up of 7.39 months (range, 3.22-20.47 mo), median progression-free survival was 1.9 months (90% confidence interval, 1.84-3.68) and median overall survival was 13.4 months (90% confidence interval,11.3-∞). No regimen-related grade 3/4/5 toxicities were observed. There were 9/20 patients with positive enzyme-linked immunosorbent spot at day 50 and/or day 90. Our adjuvant regimen combining PF-3512676 and granulocyte macrophage-colony stimulating factor was safe and is worthy of further testing with these or alternative peptides, potentially in combination with antibodies that target immunoregulatory checkpoints.