This study is the first large, randomized, multi-institutional trial of multi-epitope peptide vaccination for patients who have failed prior therapy for metastatic unresectable melanoma. The study addresses laboratory as well as traditional clinical endpoints that were considered critical to future vaccine development. Previous large randomized multicenter melanoma vaccine trials either could not evaluate therapeutic impact because they were conducted in the adjuvant setting (31
) or they have not generally employed current immunological monitoring against defined immunogenic peptides (34
). We tested the immune response to lineage antigen-derived peptides administered either alone or in combination with two immunomodulatory agents whose efficacy has been or is being tested in the adjuvant clinical arena. We have demonstrated the feasibility and safety of multicenter vaccine studies in conjunction with laboratory immunologic analyses for patients with metastatic melanoma.
The primary endpoints of this study were to define the immune response rate to the multi-epitope peptide vaccination, and to determine the influence of immunomodulatory agents upon peptide-specific immune response. The OIRR was lower compared with prior multi-epitope peptide vaccination studies in patients with unresectable metastatic melanoma (15
). This inferior immune response rate may be a laboratory artifact and could be attributable to the in vitro
sensitization of lymphocytes to enhance detection of low-frequency melanoma antigen specific precursor T-cells.
This study was large enough to have adequate statistical power to confirm observations from smaller vaccine studies previously reported in metastatic melanoma. First
, the objective response rate (CR plus PR) observed in this study was similar to reported results (20
) suggesting limited epitope spreading, with insufficient duration and/or magnitude of immune responses induced to achieve tumor regression. Second
induced higher rates of vaccination response than the other two lineage-specific peptides, and this high immunogenicity has previously been reported in other studies (35
). There are two possible explanations for this observation: a higher immunogenicity of the gp100209–217
peptide analog has been noted and an increased abundance of gp100+ melanoma cells lines has been described (37
). However, no enhancement of immunogenicity was observed with the modified tyrosinase peptide analog used in this study. Third
, the survival of HLA-A2 positive patients enrolled into this trial was longer than historically anticipated (38
). HLA-A2 positive patients have been noted to have improved outcome in the setting of operable high-risk disease (40
). The prolonged OS observed in this series of patients, all of whom were HLA-A2 positive, will be of interest to compare with patients other series of patients with metastatic melanoma according to MHC type (41
This is the first study large enough to have adequate power to assess the immunomodulatory effects of cytokines on antigen-specific immune responses and antitumor responses of patients with refractory advanced metastatic melanoma. In this study neither IFNα nor GM-CSF significantly augmented the immunologic response to peptide vaccination of patients with active measurable metastatic melanoma. This may be explained by counter-regulatory mechanisms that may be triggered by the systemic administration of immunomodulatory cytokines. Alternatively, and given the effect of IFNα and GM-CSF upon tumor infiltrating immune cells (5
), it may be that the most relevant assessment of tumor immunity and vaccination would have focused upon tumor-infiltrating rather than peripheral blood antigen-specific lymphocyte responses.
The most promising finding that emerges from this study is that patients with immune response to at least one of the vaccine peptides lived longer than patients without immune response, as has previously been noted in smaller vaccine studies (38
) and is remarkable for a number of reasons. First, it suggests that therapies that augment host immune response may improve the outcome of metastatic melanoma. Second, this finding suggests that immune response to vaccination may be used as a marker of improved prognosis in patients with metastatic melanoma. Our results concord well with the recent results of a separate adjuvant study upon the prognostic significance of autoimmunity in patients with resected high-risk melanoma who receive high-dose interferon—and suggest that autoimmunity is an intermediate marker of benefit from HDI through the induction of a more specific immunity to lineage and other antigens of melanoma (9
). Third, understanding the molecular mechanisms regulating the development of antigen-specific immune response to vaccination may lead to further improvement of treatment for metastatic melanoma.
In summary, this large multicenter randomized phase II study of vaccination with lineage peptide antigens of melanoma administered in conjunction with two different immunomodulatory cytokines has shown that large studies with complex intermediate immunologic endpoints are feasible in the cooperative groups, using a central reference immunological monitoring laboratory. Neither of the cytokines, tested in this study was capable of significantly augmenting the immunologic or therapeutic response to vaccination. However, immune response to vaccination was associated with improved OS. This provides support for the pursuit of these same peptide vaccines in the adjuvant setting, which has been accomplished in the E4697 intergroup trial that enrolled 815 patients to rigorously test the benefit of vaccination vs. placebo using the exact same peptides and schedule tested in E1696. A better understanding of the mechanisms that regulate immune responses to melanoma vaccines is necessary before larger phase III randomized vaccine trials are conducted.
Statement of Clinical Relevance
The results of the Eastern Cooperative Oncology Group multi-epitope peptide vaccine trial E1696 trial reported in this manuscript have translational implications for the future therapy of melanoma in several respects: the results demonstrate the feasibility and immunological efficacy of multi-epitope peptide vaccination, providing the foundation for adjuvant studies of this multi-epitope peptide vaccine that are ongoing in the intergroup. In summary, the results (1
) demonstrate the feasibility of vaccination with rigorous immunological assessments in the national cooperative groups, coupled with either GM-CSF or interferon alfa-2b systemic therapy tested in a factorial 2 × 2 design. This study of 120 subjects who had failed prior therapy demonstrates (2
) that multi-epitope peptide vaccination induces immune response in a significant fraction of patients determined using complex ELISPOT immunological assays performed in a central reference laboratory. The modulation of immune responses assessed by ELISPOT assays of T cell IFN gamma production is correlated with improved overall survival. Finally this study (3
) provides the foundation in advanced metastatic melanoma for multi-epitope peptide vaccination that has now been evaluated using a placebo-controlled design testing GM-CSF and/or peptide vaccination in 825 patients with operable stage III–IV melanoma (Intergroup E4697).