Biomarker correlation to clinical response in phase I/II trials of the adjuvant breast cancer vaccine neuvax (nelipepimut-S or E75).

TPS3126 Background: We completed phase I/II clinical trials with NeuVax (nelipepimut-S), a HLA-A2/A3-restricted, HER2-derived peptide vaccine. The vaccine was administered in the adjuvant setting to prevent recurrence in breast cancer patients rendered disease-free with standard-of-care therapy. Here, we examine the relationship between in vitro immunologic response (IR) and clinical recurrence (CR) after 5-year follow-up. Methods: The phase I/II trials were performed as dose-escalation/schedule-optimization trials enrolling node positive and high-risk, node-negative patients (pts) with tumors expressing any level of HER2 (IHC 1+,2+,or 3+). HLA-A2/A3+ pts were enrolled in the vaccine group (VG) while HLA-A2/A3- pts were followed prospectively as an untreated control group (CG). The VG was given 4-6 monthly intradermal inoculations of nelipepimut-S+GMCSF (immunoadjuvant) during the primary vaccine series (PVS). In vitro IR was assessed for E75-specific, cytotoxic T lymphocyte clonal expansion by HLA-A2:IgG...