Phase 2 Study of the g209-2M Melanoma Peptide Vaccine and Low-Dose Interleukin-2 in Advanced Melanoma

Immunotherapy of melanoma: an update

The incidence of melanoma has been increasing worldwide. A relationship between melanoma and the immune system was established years ago. Modulating the immune system in the management of different stages of melanoma has been the focus of numerous large randomized trials worldwide. This article reviews the current status of immunotherapy for melanoma, with a focus on the recent promising results from using vaccines, cytotoxic T-lymphocyte antigen-4 (CTLA-4) antibodies, and adoptive cell therapy.

Phase I clinical trial of the vaccination for the patients with metastatic melanoma using gp100-derived epitope peptide restricted to HLA-A*2402

BACKGROUND

The tumor associated antigen (TAA) gp100 was one of the first identified and has been used in clinical trials to treat melanoma patients. However, the gp100 epitope peptide restricted to HLA-A*2402 has not been extensively examined clinically due to the ethnic variations. Since it is the most common HLA Class I allele in the Japanese population, we performed a phase I clinical trial of cancer vaccination using the HLA-A*2402 gp100 peptide to treat patients with metastatic melanoma.

METHODS

The phase I clinical protocol to test a HLA-A*2402 gp100 peptide-based cancer vaccine was designed to evaluate safety as the primary endpoint and was approved by The University of Tokyo Institutional Review Board. Information related to the immunologic and antitumor responses were also collected as secondary endpoints. Patients that were HLA-A*2402 positive with stage IV melanoma were enrolled according to the criteria set by the protocol and immunized with a vaccine consisting of epitope peptide (VYFFLPDHL, gp100-in4) emulsified with incomplete Freund's adjuvant (IFA) for the total of 4 times with two week intervals. Prior to each vaccination, peripheral blood mononuclear cells (PBMCs) were separated from the blood and stored at -80°C. The stored PBMCs were thawed and examined for the frequency of the peptide specific T lymphocytes by IFN-γ- ELISPOT and MHC-Dextramer assays.

RESULTS

No related adverse events greater than grade I were observed in the six patients enrolled in this study. No clinical responses were observed in the enrolled patients although vitiligo was observed after the vaccination in two patients. Promotion of peptide specific immune responses was observed in four patients with ELISPOT assay. Furthermore, a significant increase of CD8+ gp100-in4+ CTLs was observed in all patients using the MHC-Dextramer assay. Cytotoxic T lymphocytes (CTLs) clones specific to gp100-in4 were successfully established from the PBMC of some patients and these CTL clones were capable of lysing the melanoma cell line, 888 mel, which endogenously expresses HLA-restricted gp100-in4.

CONCLUSION

Our results suggest this HLA-restricted gp100-in4 peptide vaccination protocol was well-tolerated and can induce antigen-specific T-cell responses in multiple patients. Although no objective anti-tumor effects were observed, the effectiveness of this approach can be enhanced with the appropriate modifications.

Immunotherapy for melanoma: current status and perspectives

Immunotherapy is an important modality in the therapy of patients with malignant melanoma. As our knowledge about this disease continues to expand, so does the immunotherapeutic armamentarium. Nevertheless, successful preclinical models do not always translate into clinically meaningful results. The authors give a comprehensive analysis of most recent advances in the immune anti-melanoma therapy, including interleukins, interferons, other cytokines, adoptive immunotherapy, biochemotherapy, as well as the use of different vaccines. We also present the fundamental concepts behind various immune enhancement strategies, passive immunotherapy, as well as the use of immune adjuvants. This review brings into discussion the results of newer and older clinical trials, as well as potential limitations and drawbacks seen with the utilization of various immune therapies in malignant melanoma. Development of novel therapeutic approaches, along with optimization of existing therapies, continues to hold a great promise in the field of melanoma therapy research. Use of anti-CTLA4 and anti-PD1 antibodies, realization of the importance of co-stimulatory signals, which translated into the use of agonist CD40 monoclonal antibodies, as well as activation of innate immunity through enhanced expression of co-stimulatory molecules on the surface of dendritic cells by TLR agonists are only a few items on the list of recent advances in the treatment of melanoma. The need to engineer better immune interactions and to boost positive feedback loops appear crucial for the future of melanoma therapy, which ultimately resides in our understanding of the complexity of immune responses in this disease.

Novel therapeutics for the treatment of metastatic melanoma

Metastatic malignant melanoma is an incurable disease with a median survival of 8.5 months and a probability of surviving 5 years after the diagnosis of less than 5%. To date, no systemic therapy has meaningfully changed these survival end points. Currently, in the USA the FDA has approved three agents for the treatment of metastatic melanoma: hydroxyurea, dacarbazine and interleukin-2. None of these have demonstrated a meaningfully prolonged survival of patients with metastatic melanoma. Therefore, a number of innovative therapeutic strategies have been pursued to improve outcomes, including immune therapy, tyrosine kinase inhibitors and angiogenesis inhibitors. Herein, we review some of the recent advances in novel therapeutic developments for the treatment of metastatic melanoma.

Cytokines as Adjuvants for Vaccine and Cellular Therapies for Cancer

PROBLEM STATEMENT: The development of a potent vaccine that can help treat tumors resistant to conventional cytotoxic therapies remains elusive. While part of the problem may be that trials have focused on patients with bulky residual disease, the desire to maximize responses to the vaccine remains. APPROACH: The gamma(c) family of cytokines offer a unique opportunity to support the expansion and effector potential of vaccine-responding T-cells, as well as stimulate other effectors, such as natural killer (NK) cells, to become activated. RESULTS: Combining vaccines with cytokines seems logical but can bring unwanted toxicity, as has been observed with interleukin (IL)-2. In addition, the nonspecific activation or expansion of unwanted cell subsets, such as regulatory T-cells, can contribute to global immunosuppression and limit vaccine responses. The development of IL-7 and IL-21 for the clinic offers the promise of enhancing anti-tumor responses but with far less systemic toxicity and no expansion of regulatory T cells. Preclinical studies demonstrate that IL-15 could also improve T-cell, and especially NK-cell, responses as well. CONCLUSIONS/RECOMMENDATIONS: Future work should expand the use of vaccines with IL-7, IL-21 and hopefully IL-15 in high-risk patients, and consider treatment while in a state of minimal residual disease to maximize benefit. Identifying tumors that can signal through gamma(c) cytokines will also be essential so that induction of relapse will be avoided.

HLA typing demands for peptide-based anti-cancer vaccine

Immunological treatment of cancer has made some very promising advances during the last years. Anti-cancer vaccination using peptides or peptide-pulsed dendritic cells and adoptive transfer of in vitro generated, epitope-specific T cells depend on a well-fitting interaction of HLA molecule and epitope. Accurate HLA-typing is a key factor for successful anti-cancer vaccination. No comprehensive data and no suggestion exist on the HLA-typing in this setting. We performed a systematic review of PubMed analyzing HLA-typing data in cancer vaccination trials over the last 4 years (2004-2007). Then, using the SYFPEITHI database, we calculated the peptide binding prediction of the eight most often used HLA-A*0201 binding epitopes. Finally, high-resolution typing [by sequence-specific primers (SSP)] data of a HLA-A*02 or HLA-A*24 positive population in Berlin, Germany, were analyzed. Forty-five cancer vaccination trials with 764 patients were included. Eighteen studies were performed in the USA, 13 in Europe, 12 in Asia (mainly Japan), and two in Australia. Most common diseases targeted were melanoma, prostate cancer, colorectal cancer, renal cell cancer, and breast cancer. The trials tested protocols using peptide plus adjuvants without DC or protocols using peptide-pulsed DC. In 38 trials (84%) HLA-A2 positive patients were vaccinated, in 11 studies (24%) HLA-A24 positive patients were vaccinated. Nineteen studies with 291 patients (38%) presented the HLA type as four-digit code (high-resolution), 26 studies with 473 patients (62%) presented the HLA-type in a low-resolution code. The method of HLA determination was given in six out of 45 trials (13%). Using the SYFPEITHI database we calculated the peptide binding prediction of the eight most often used HLA-A*0201 binding tumor antigen-derived epitopes for binding to HLA-A*0203. While the epitopes had a binding score of 17-28 for HLA-A*0201, the score for binding to HLA-A*0203 was zero in seven out of eight tested peptides. Only for one peptide the score was eight. Finally, we analyzed high-resolution data of HLA-A*02 and HLA-A*24 positive patients in Berlin, Germany. We found the HLA-A*0201 allele and HLA-A*2402 allele in 95%, respectively. HLA-A*0201 and HLA-A*2402 are most commonly used for peptide based vaccine in cancer. Data on HLA-typing given in the included cancer vaccine manuscripts are fractional. Only 13% report the method of HLA typing and most HLA types are given as low-resolution code. Looking at the binding of specific peptides to both the alleles, it is important to perform high-resolution typing. Further suggestions for immunogenetic laboratories and clinical tumor immunologists regarding HLA-typing for cancer vaccine trials and adoptive T cell transfer approaches are discussed.

Three phase II cytokine working group trials of gp100 (210M) peptide plus high-dose interleukin-2 in patients with HLA-A2-positive advanced melanoma

PURPOSE

High-dose interleukin-2 (IL-2) induces responses in 15% to 20% of patients with advanced melanoma; 5% to 8% are durable complete responses (CRs). The HLA-A2-restricted, modified gp100 peptide (210M) induces T-cell immunity in vivo and has little antitumor activity but, combined with high-dose IL-2, reportedly has a 42% (13 of 31 patients) response rate (RR). We evaluated 210M with one of three different IL-2 schedules to determine whether a basis exists for a phase III trial.

PATIENTS AND METHODS

In three separate phase II trials, patients with melanoma received 210M subcutaneously during weeks 1, 4, 7, and 10 and standard high-dose IL-2 during weeks 1 and 3 (trial 1), weeks 7 and 9 (trial 2), or weeks 1, 4, 7, and 10 (trial 3). Immune assays were performed on peripheral-blood mononuclear cells collected before and after treatment.

RESULTS

From 1998 to 2003, 131 patients with HLA-A2-positive were enrolled. With 60-month median follow-up time, the overall RR for 121 assessable patients was 16.5% (95% CI, 10% to 26%); the RRs were 23.8% in trial 1 (42 patients), 12.5% in trial 2 (40 patients), and 12.8% in trial 3 (39 patients). There were 11 CRs (9%) and nine partial responses (7%), with 11 patients (9%) progression free at >or= 30 months. Immune studies including assays of CD3-zeta expression and numbers of CD4(+)/CD25(+)/FoxP3(+) regulatory T cells, CD15(+)/CD11b(+)/CD14(-) immature myeloid-derived cells, and CD8(+)gp100 tetramer-positive cells in the blood did not correlate with clinical benefit.

CONCLUSION

The results again demonstrate efficacy of high-dose IL-2 in advanced melanoma but did not demonstrate the promising clinical activity reported with vaccine and high-dose IL-2 in any of three phase II trials.

Chemical conjugate TMV-peptide bivalent fusion vaccines improve cellular immunity and tumor protection

Chemical conjugation of CTL peptides to tobacco mosaic virus (TMV) has shown promise as a molecular adjuvant scaffold for augmentation of cellular immune responses to peptide vaccines. This study demonstrates the ease of generating complex multipeptide vaccine formulations using chemical conjugation to TMV for improved vaccine efficacy. We have tested a model foreign antigen target-the chicken ovalbumin-derived CTL peptide (Ova peptide), as well as mouse melanoma-associated CTL epitopes p15e and tyrosinase-related protein 2 (Trp2) peptides that are self-antigen targets. Ova peptide fusions to TMV, as bivalent formulations with peptides encoding additional T-help or cellular uptake via the integrin-receptor binding RGD peptide, showed improved vaccine potency evidenced by significantly enhanced numbers of antigen-reactive T cells measured by in vitro IFNgamma cellular analysis. We measured the biologically relevant outcome of vaccination in protection of mice from EG.7-Ova tumor challenge, which was achieved with only two doses of vaccine ( approximately 600 ng peptide) given without adjuvant. The p15e peptide alone or Trp2 peptide alone, or as a bivalent formulation with T-help or RGD uptake epitopes, was unable to stimulate effective tumor protection. However, a vaccine with both CTL peptides fused together onto TMV generated significantly improved survival. Interestingly, different bivalent vaccine formulations were required to improve vaccine efficacy for Ova or melanoma tumor model systems.

Liposomal vaccines--targeting the delivery of antigen

Vaccines that can prime the adaptive immune system for a quick and effective response against a pathogen or tumor cells, require the generation of antigen (Ag)-specific memory T and B cells. The unique ability of dendritic cells (DCs) to activate naïve T cells, implies a key role for DCs in this process. The generation of tumor-specific CD8(+) cytotoxic T cells (CTLs) is dependent on both T cell stimulation with Ag (peptide-MHC-complexes) and costimulation. Interestingly, tumor cells that lack expression of T cell costimulatory molecules become highly immunogenic when transfected to express such molecules on their surface. Adoptive immunotherapy with Ag-pulsed DCs also is a strategy showing promise as a treatment for cancer. The use of such cell-based vaccines, however, is cumbersome and expensive to use clinically, and/or may carry risks due to genetic manipulations. Liposomes are particulate vesicular lipid structures that can incorporate Ag, immunomodulatory factors and targeting molecules, and hence can serve as potent vaccines. Similarly, Ag-containing plasma membrane vesicles (PMV) derived from tumor cells can be modified to incorporate a T cell costimulatory molecule to provide both TCR stimulation, and costimulation. PMVs also can be modified to contain IFN-gamma and molecules for targeting DCs, permitting delivery of both Ag and a DC maturation signal for initiating an effective immune response. Our results show that use of such agents as vaccines can induce potent anti-tumor immune responses and immunotherapeutic effects in tumor models, and provide a strategy for the development of effective vaccines and immunotherapies for cancer and infectious diseases.