Pilot Study of Neoantigen Peptides for the Treatment of Neoplasms

Rationale: Cancer cells express unique peptide antigens recognized by CD8+ cytotoxic T lymphocytes (CTL), which are typically 8-10 amino acids long and are presented in association with Class I MHC molecules. The peptides recognized by helper (CD4+) T-cells are presented in association with Class II MHC molecules and are usually longer (13-18 amino acids in length), although peptide elution studies have indicated no apparent restriction on peptide length. Selected peptides can induce circulating T cell responses in most patients, and that vaccination with a mixture of peptides is immunogenic in up to 100% of patients. The magnitude of T cell responses sometimes is substantial, with 1-5% of circulating CD8 T cells reactive to single antigens. T cell responses to vaccines may be durable for months or years, but are at least as likely to be transient, sometimes declining even while still receiving vaccines. However, T cells induced by vaccination can recognize and lyse cancerous cells expressing the relevant protein and MHC, and peptide vaccines induce promising immunogenicity.

Though MHC-restriction of individual peptides limits their use to a subset of patients, there are mixtures of a dozen peptides restricted by HLA-A1, A2, A3, or A11 can be prepared as a stable mixture and can induce immune responses in 85% of patients with cancer who express one or more of those MHC molecules, without negative effects from competition among the peptides. Other experience supports the ability to induce T cell responses to multiple peptides when vaccinating with peptide mixtures. Since antigenic peptides are easily degraded by proteases in the body, it is difficult for the receptors expressed on the immune cells to identify antigen epitopes, and they do not generate a strong immune response to pathogens. An epitope-based vaccine with a reasonable design is composed of epitope peptide/s, a delivery system, and an adjuvant. For multi-epitope vaccines, since the traditional carriers and adjuvants are associated with poor efficacy, vaccine designs with built-in adjuvants have been proposed. Therefore, a built-in adjuvant exhibiting both the functions of a transmission system and a traditional adjuvant, is constructed within the vaccine to improve the immunogenicity of epitope peptides by stimulating the innate immune response required for an adaptive immune response. To achieve this goal, the epitopes are regularly fused with adjuvant proteins or displayed on the surface of some particular biomaterials (e.g., liposomes, gold nanoparticles, and poly(lactic-co-glycolic acid) (PLGA)) and the immunogenicity of the epitopes are significantly increased by this immune complex.

Study design: This research is a pilot clinical trial using a personalized neoantigen peptide vaccine. Approximately 100 patients with cancer and whose sequencing studies show the presence of neoantigens will receive the personalized multi-peptide vaccine. Peptide vaccines will be given with an adjuvant (Montanide ISA-51 VG) by intradermal injection (~0.5 mg of each peptide) in the arm every week for a maximum of 8 weeks; the treatment will be discontinued if disease progresses or if there is deterioration of the patient's general condition. All patients will give written informed consent; their data will be coded and fully anonymized. The study was approved by the Ethics Committee of the Regenerative Medicine Institute and conformed to the ethical guidelines of the Declaration of Helsinki.