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Dendritic cells (DCs) have received considerable attention as potential targets for the development of novel cancer immunotherapies. However, the clinical efficacy of DC-based vaccines remains suboptimal, largely reflecting local and systemic immunosuppression at baseline. An autologous DC-based vaccine (DCVAC) has recently been shown to improve progression-free survival and overall survival in randomized clinical trials enrolling patients with lung cancer (SLU01, NCT02470468) or ovarian carcinoma (SOV01, NCT02107937), but not metastatic castration-resistant prostate cancer (SP005, NCT02111577), despite a good safety profile across all cohorts. We performed biomolecular and cytofluorometric analyses on peripheral blood samples collected prior to immunotherapy from 1000 patients enrolled in these trials, with the objective of identifying immunological biomarkers that may improve the clinical management of DCVAC-treated patients. Gene signatures reflecting adaptive immunity and T cell activation were associated with favorable disease outcomes and responses to DCVAC in patients with prostate and lung cancer, but not ovarian carcinoma. By contrast, the clinical benefits of DCVAC were more pronounced among patients with ovarian carcinoma exhibiting reduced expression of T cell-associated genes, especially those linked to T H2 -like signature and immunosuppressive regulatory T (T REG ) cells. Clinical responses to DCVAC were accompanied by signs of antitumor immunity in the peripheral blood. Our findings suggest that circulating signatures of antitumor immunity may provide a useful tool for monitoring the potency of autologous DC-based immunotherapy., Competing Interests: IV declares consulting for AstraZeneca, Clovis Oncology Inc., Carrick Therapeutics, Deciphera Pharmaceuticals, Elevar Therapeutics, F. Hoffmann-La Roche Ltd, Genmab, GSK, Immunogen Inc., Jazzpharma, Mersana, Millennium Pharmaceuticals, MSD, Novocure, Octimet Oncology NV, Oncoinvent AS, Sotio a.s., Verastem Oncology, Zentalis; contracted research for: Oncoinvent AS, Genmab; and research funding from Amgen and Roche. RS and JB are minority shareholders of Sotio. ADG received fees for consultancy, lectures or services from Boehringer Ingelheim (Germany), Miltenyi Biotec (Germany), Isoplexis (USA) and Novigenix (Switzerland). AR declares advisory services and invited lectures for Amgen, AstraZeneca, BMS, Eli-Lilly, Janssen-Cilag, MSD, and Roche. AC is a contracted researcher for Oncoinvent AS and Novocure and a consultant for Sotio Biotech a.s. MH, JR, LK, TL, JF, PH, MH, TH, PK, KS, DR, LS, JB, RS, and JF are employees of Sotio a.s. The other authors declare no conflicts of interest., (© 2022 Sotio Biotech. Published with license by Taylor & Francis Group, LLC.)

Purpose: The successful implementation of immune checkpoint inhibitors (ICI) in the clinical management of various solid tumors has raised considerable expectations for patients with epithelial ovarian carcinoma (EOC). However, EOC is poorly responsive to ICIs due to immunologic features including limited tumor mutational burden (TMB) and poor lymphocytic infiltration. An autologous dendritic cell (DC)-based vaccine (DCVAC) has recently been shown to be safe and to significantly improve progression-free survival (PFS) in a randomized phase II clinical trial enrolling patients with EOC (SOV01, NCT02107937)., Patients and Methods: We harnessed sequencing, flow cytometry, multispectral immunofluorescence microscopy, and IHC to analyze (pretreatment) tumor and (pretreatment and posttreatment) peripheral blood samples from 82 patients enrolled in SOV01, with the aim of identifying immunologic biomarkers that would improve the clinical management of patients with EOC treated with DCVAC., Results: Although higher-than-median TMB and abundant CD8+ T-cell infiltration were associated with superior clinical benefits in patients with EOC receiving standard-of-care chemotherapy, the same did not hold true in women receiving DCVAC. Conversely, superior clinical responses to DCVAC were observed in patients with lower-than-median TMB and scarce CD8+ T-cell infiltration. Such responses were accompanied by signs of improved effector functions and tumor-specific cytotoxicity in the peripheral blood., Conclusions: Our findings suggest that while patients with highly infiltrated, "hot" EOCs benefit from chemotherapy, women with "cold" EOCs may instead require DC-based vaccination to jumpstart clinically relevant anticancer immune responses., (©2022 American Association for Cancer Research.)