Phase I/II clinical trial of a helper peptide vaccine plus PD-1 blockade in PD-1 antibody-naïve and PD-1 antibody-experienced patients with melanoma (MEL64). Issue 9 (13th September 2022)

• Record Type: Journal Article
• Authors: Vavolizza, Rick Daniel; Petroni, Gina R; Mauldin, Ileana S; Chianese-Bullock, Kimberly A; Olson, Walter C; Smith, Kelly T; Dengel, Lynn T; Haden, Kathleen; Grosh, William W; Kaur, Varinder; Varhegyi, Nikole; Gaughan, Elizabeth M; Slingluff, Craig L
• Is Part Of: Journal for immunotherapy of cancer. Volume 10:Issue 9(2022)
• Publication Date: 2022-09-13
• Subjects: immunogenicity, vaccine -- programmed cell death 1 receptor -- combined modality therapy -- immunotherapy -- CD4-positive T-lymphocytes; Cancer -- Immunotherapy -- Periodicals; Cancer -- Immunological aspects -- Periodicals; Tumors -- Immunological aspects -- Periodicals; Immunotherapy -- Periodicals; 616.99406105
• DOI: 10.1136/jitc-2022-005424
• Languages: English
• ISSNs: 2051-1426

Abstract

Abstract : Background: A vaccine containing 6 melanoma-associated peptides to stimulate helper T cells (6MHP) is safe, immunogenic, and clinically active. A phase I/II trial was designed to evaluate safety and immunogenicity of 6MHP vaccines plus programmed death 1 (PD-1) blockade. Participants and methods: Participants with advanced melanoma received 6MHP vaccines in an incomplete Freund's adjuvant (6 vaccines over 12 weeks). Pembrolizumab was administered intravenously every 3 weeks. Tumor biopsies at baseline and day 22 were analyzed by multiplex immunohistochemistry. Primary end points were safety (Common Terminology Criteria for Adverse Events V.4.03) and immunogenicity (ex vivo interferon-γ ELISpot assay). Additional end points included changes in the tumor microenvironment (TME) and clinical outcomes. Results: Twenty-two eligible participants were treated: 6 naïve to PD-1 antibody (Ab) and 16 PD-1 Ab-experienced. Median follow-up was 24.4 months. Most common treatment-related adverse events (any grade) included injection site reactions, fatigue, anemia, lymphopenia, fever, elevated aspartate aminotransferase, pruritus, and rash. Treatment-related dose-limiting toxicities were observed in 3 (14%) participants, which did not cross the study safety bound. A high durable T cell response (Rsp) to 6MHP was detected in only one participant, but twofold T cell Rsps to 6MHP were detected in 7/22 (32%; 90% CI (16% to 52%)) by week 13. Objective clinical responses were observed in 23% (1 complete response, 4 partial responses), including 4/6 PD-1 Ab-naïve (67%) and 1/16 PD-1 Ab-experienced (6%). Overall survival (OS) was longer for PD-1 Ab-naïve than Ab-experienced participants (HR 6.3 (90% CI (2.1 to 28.7)). In landmark analyses at 13 weeks, OS was also longer for those with T cell Rsps (HR 6.5 (90% CI (2.1 to 29.2)) and for those with objective clinical responses. TME evaluation revealed increased densities of CD8 + T cells, CD20 + B cells, and Tbet + cells by day 22. Conclusions: Treatment with the 6MHP vaccine plus pembrolizumab was safe, increased intratumoral lymphocytes, and induced T cell Rsps associated with prolonged OS. The low T cell Rsp rate in PD-1 Ab-experienced participants corroborates prior murine studies that caution against delaying cancer vaccines until after PD-1 blockade. The promising objective response rate and OS in PD-1 Ab-naïve participants support consideration of a larger study in that setting.