Immunization of HLA-A*0201 and/or HLA-DPβ1*04 Patients with Metastatic Melanoma Using Epitopes from the NY-ESO-1 Antigen

During the past decade, the identification of tumor-associated antigens has opened new opportunities for the development of cancer immunotherapies.1 Cancer vaccines using immunogenic peptide epitopes from tumor antigens have been used in clinical trials to treat patients with metastatic melanoma, with limited success. Many of these trials used immunization with human leukocyte antigen (HLA) class I-restricted peptides. Even though many of these peptides were efficient in generating high levels of peptide and/or tumor-reactive CD8+ T cells (CTLs) in vivo, positive immunologic response has not correlated with objective clinical responses.2 In the present trial, we administered HLA class I- and class II-restricted peptides derived from the tumor-associated antigen NY-ESO-1 to patients with metastatic melanoma. We hypothesized that providing specific helper CD4+ T cells by immunization with a class II-restricted epitope would lead to enhanced CTL activation and a sustained CTL response against tumor. Helper CD4+ T cells have been shown to play a central role in the initiation and maintenance of an effective CTL anti-tumor response3,4 by a variety of mechanisms, including the elaboration of appropriate cytokines and activation of antigen-presenting cells.5,6 NY-ESO-1 is an immunogenic cancer/testis antigen expressed in a variety of tumors, including melanoma, breast, ovary, lung cancers, and sarcomas.7,8 Its expression in normal tissues is limited to testis. Antibodies and/or CTL reactivity directed against NY-ESO-1 were detected in approximately 50% of patients whose tumors expressed NY-ESO-1. Both humoral and cellular immune responses to ESO-1 have been reported in patients with a variety of cancers.9,10 We recently identified two patients with strong pre-existing immunity to NY-ESO-1, both in peripheral blood and tumor-infiltrating lymphocytes (11 and unpublished data). Both patients had dramatic responses to immunotherapy. Whether NY-ESO-1 immunity played any role in their responses remains to be defined. The NY-ESO-1:157-165 was previously found to be the minimal epitope recognized by specific CD8+ T cells in an HLA-A2-restricted fashion.9 This peptide was modified in an attempt to improve peptide binding and stability in solution. The cysteine residue at P9 was replaced with valine to prevent dimerization of the peptide. The modified peptide was designated NY-ESO-1:157-165(9V) or ESO-1:165V. Stability studies using mass spectrometry revealed that the native peptide rapidly dimerized and lost activity while the modified ESO-1:165V peptide was stable in solution.12 In addition, our group recently identified a naturally processed helper epitope from NY-ESO-1 that was recognized by CD4+ T cells in the context of HLA-DPB1*0401 and *0402.13 DP4 is the most prevalent class II HLA allele in Caucasians (43–70%) and is also found to be associated with the development of antibody against ESO-1.13 Therefore, the modified HLA-A2-restricted epitope ESO-1:165V and the HLA-DP4 restricted epitope (ESO-1:161-180) were used in our ESO-1 vaccine study of patients with metastatic melanoma. In this article we report on the clinical and immunologic responses from patients who received the class I-restricted peptide alone, the class II-restricted peptide alone, or a combination of both class I- and class II-restricted peptides. The primary objective of this study was to determine whether the administration of a class I- and/or class II-restricted NY-ESO-1 peptide in patients with metastatic melanoma could elicit an immunologic response against the vaccinated peptides as measured by an in vitro sensitization (IVS) assay, and tumor regression. The secondary objective of this study was to determine toxicity and to gain information for the possible conduct of future protocols.