First-in-man application of a novel therapeutic cancer vaccine formulation with the capacity to induce multi-functional T cell responses in ovarian, breast and prostate cancer patients

Abstract

Background: DepoVax is a novel non-emulsion depot-forming vaccine platform with the capacity to significantly enhance the immunogenicity of peptide cancer antigens. Naturally processed HLA-A2 restricted peptides presented by breast, ovarian and prostate cancer cells were used as antigens to create a therapeutic cancer vaccine, DPX-0907.

Methods: A phase I clinical study was designed to examine the safety and immune activating potential of DPX-0907 in advanced stage breast, ovarian and prostate cancer patients. A total of 23 late stage cancer patients were recruited and were divided into two dose/volume cohorts in a three immunization protocol.

Results: DPX-0907 was shown to be safe with injection site reactions being the most commonly reported adverse event. All breast cancer patients (3/3), most of ovarian (5/6) and one third of prostate (3/9) cancer patients exhibited detectable immune responses, resulting in a 61% immunological response rate. Immune responses were generally observed in patients with better disease control after their last prior treatment. Antigen-specific responses were detected in 73% of immune responders (44% of evaluable patients) after the first vaccination. In 83% of immune responders (50% of evaluable patients), peptide-specific T cell responses were detected at ≥2 time points post vaccination with 64% of the responders (39% of evaluable patients) showing evidence of immune persistence. Immune monitoring also demonstrated the generation of antigen-specific T cell memory with the ability to secrete multiple Type 1 cytokines.

Conclusions: The novel DepoVax formulation promotes multifunctional effector memory responses to peptide-based tumor associated antigens. The data supports the capacity of DPX-0907 to elicit Type-1 biased immune responses, warranting further clinical development of the vaccine. This study underscores the importance of applying vaccines in clinical settings in which patients are more likely to be immune competent.

Trial registration: ClinicalTrials.gov NCT01095848.

Figures

Figure 1

The generation of antigen-specific CD8.+T cells in DPX-0907 vaccinated ovarian, prostate and breast cancer patients. Patient PBMC were stimulated with indicated peptides in vitro as described in Materials and Methods. Cells were stained with corresponding MHC-peptide pentamer reagents to detect CD8+ T cells with peptide-specific TCR repertoire. HIV-pentamer served as a negative control (patients pre-screened for being HIV negative) and CMV-specific pentamer was used on a known CMV-positive donor PBMC as internal positive control for the assay (data not shown). Samples from all study time points were run simultaneously in the assay for each patient. Data represented as percentage of live gated CD3+CD8+ cells that were positive for pentamer staining. The background staining on CD8 negative cells (0.02-0.06%) has been subtracted from the values shown and the values for control HIV-pentamer staining were in the range of 0.00 to 0.03% for all patients.