Fully closed and automated enrichment of primary blood dendritic cells for cancer immunotherapy.

Dendritic cell (DC) vaccination is a promising approach to induce tumor-specific immune responses in cancer patients. Until recently, most DC vaccines were based on in vitro-differentiated monocyte-derived DCs. However, through development of efficient isolation techniques, the use of primary blood dendritic cell subsets has come within reach. Manufacturing of blood-derived DCs has multiple advances over monocytes-derived DCs, including more standardized isolation and culture protocols and shorter production processes. In peripheral blood, multiple DC subsets can be distinguished based on their phenotype and function. Plasmacytoid DC (pDC) and myeloid/conventional DCs (cDC) are the two main DC populations, moreover cDC can be further subdivided into CD141/BDCA3+ DC (cDC1) and CD1c/BDCA1+ DC (cDC2). In three separate clinical DC vaccination studies in melanoma and prostate cancer patients, we manufactured DC vaccines consisting of pDCs only, cDC2s only, or a combination of pDC and cDC2s, which we called natural DCs (nDC). Here, we describe a fully closed and automated GMP-compliant method to enrich naturally circulating DCs and present the results of enrichment of primary blood DCs from aphaeresis products of 8 healthy donors, 21 castrate-resistant prostate cancer patients, and 112 stage III melanoma patients. Although primary blood DCs are relatively scarce in aphaeresis material, our results show that it is feasible to isolate highly pure pDC, cDC2, or nDC with sufficient yield to manufacture DC vaccines for natural DC-based immunotherapy.

Adjuvant dendritic cell therapy in stage IIIB/C melanoma: the MIND-DC randomized phase III trial.

Autologous natural dendritic cells (nDCs) treatment can induce tumor-specific immune responses and clinical responses in cancer patients. In this phase III clinical trial (NCT02993315), 148 patients with resected stage IIIB/C melanoma were randomized to adjuvant treatment with nDCs (n = 99) or placebo (n = 49). Active treatment consisted of intranodally injected autologous CD1c+ conventional and plasmacytoid DCs loaded with tumor antigens. The primary endpoint was the 2-year recurrence-free survival (RFS) rate, whereas the secondary endpoints included median RFS, 2-year and median overall survival, adverse event profile, and immunological response The 2-year RFS rate was 36.8% in the nDC treatment group and 46.9% in the control group (p = 0.31). Median RFS was 12.7 months vs 19.9 months, respectively (hazard ratio 1.25; 90% CI: 0.88-1.79; p = 0.29). Median overall survival was not reached in both treatment groups (hazard ratio 1.32; 90% CI: 0.73-2.38; p = 0.44). Grade 3-4 study-related adverse events occurred in 5% and 6% of patients. Functional antigen-specific T cell responses could be detected in 67.1% of patients tested in the nDC treatment group vs 3.8% of patients tested in the control group (p < 0.001). In conclusion, while adjuvant nDC treatment in stage IIIB/C melanoma patients generated specific immune responses and was well tolerated, no benefit in RFS was observed.

Adjuvant dendritic cell vaccination induces tumor-specific immune responses in the majority of stage III melanoma patients.

PURPOSE: To determine the effectiveness of adjuvant dendritic cell (DC) vaccination to induce tumor-specific immunological responses in stage III melanoma patients. EXPERIMENTAL DESIGN: Retrospective analysis of stage III melanoma patients, vaccinated with autologous monocyte-derived DC loaded with tumor-associated antigens (TAA) gp100 and tyrosinase after radical lymph node dissection. Skin-test infiltrating lymphocytes (SKILs) obtained from delayed-type hypersensitivity skin-test biopsies were analyzed for the presence of TAA-specific CD8(+) T cells by tetrameric MHC-peptide complexes and by functional TAA-specific T cell assays, defined by peptide-recognition (T2 cells) and/or tumor-recognition (BLM and/or MEL624) with specific production of Th1 cytokines and no Th2 cytokines. RESULTS: Ninety-seven patients were analyzed: 21 with stage IIIA, 34 with stage IIIB, and 42 had stage IIIC disease. Tetramer-positive CD8(+) T cells were present in 68 patients (70%), and 24 of them showed a response against all 3 epitopes tested (gp100:154-162, gp100:280-288, and tyrosinase:369-377) at any point during vaccinations. A functional T cell response was found in 62 patients (64%). Rates of peptide-recognition of gp100:154-162, gp100:280-288, and tyrosinase:369-377 were 40%, 29%, and 45%, respectively. Median recurrence-free survival and distant metastasis-free survival of the whole study population were 23.0 mo and 36.8 mo, respectively. CONCLUSIONS: DC vaccination induces a functional TAA-specific T cell response in the majority of stage III melanoma patients, indicating it is more effective in stage III than in stage IV melanoma patients. Furthermore, performing multiple cycles of vaccinations enhances the chance of a broader immune response.

Prophylactic vaccines are potent activators of monocyte-derived dendritic cells and drive effective anti-tumor responses in melanoma patients at the cost of toxicity.

Dendritic cell (DC)-based immunotherapy is explored worldwide in cancer patients, predominantly with DC matured with pro-inflammatory cytokines and prostaglandin E2. We studied the safety and efficacy of vaccination with monocyte-derived DC matured with a cocktail of prophylactic vaccines that contain clinical-grade Toll-like receptor ligands (BCG, Typhim, Act-HIB) and prostaglandin E2 (VAC-DC). Stage III and IV melanoma patients were vaccinated via intranodal injection (12 patients) or combined intradermal/intravenous injection (16 patients) with VAC-DC loaded with keyhole limpet hemocyanin (KLH) and mRNA encoding tumor antigens gp100 and tyrosinase. Tumor antigen-specific T cell responses were monitored in blood and skin-test infiltrating-lymphocyte cultures. Almost all patients mounted prophylactic vaccine- or KLH-specific immune responses. Both after intranodal injection and after intradermal/intravenous injection, tumor antigen-specific immune responses were detected, which coincide with longer overall survival in stage IV melanoma patients. VAC-DC induce local and systemic CTC grade 2 and 3 toxicity, which is most likely caused by BCG in the maturation cocktail. The side effects were self-limiting or resolved upon a short period of systemic steroid therapy. We conclude that VAC-DC can induce functional tumor-specific responses. Unfortunately, toxicity observed after vaccination precludes the general application of VAC-DC, since in DC maturated with prophylactic vaccines BCG appears to be essential in the maturation cocktail.

Effective Clinical Responses in Metastatic Melanoma Patients after Vaccination with Primary Myeloid Dendritic Cells.

PURPOSE: Thus far, dendritic cell (DC)-based immunotherapy of cancer was primarily based on in vitro-generated monocyte-derived DCs, which require extensive in vitro manipulation. Here, we report on a clinical study exploiting primary CD1c(+) myeloid DCs, naturally circulating in the blood. EXPERIMENTAL DESIGN: Fourteen stage IV melanoma patients, without previous systemic treatment for metastatic disease, received autologous CD1c(+) myeloid DCs, activated by only brief (16 hours) ex vivo culture and loaded with tumor-associated antigens of tyrosinase and gp100. RESULTS: Our results show that therapeutic vaccination against melanoma with small amounts (3-10 × 10(6)) of myeloid DCs is feasible and without substantial toxicity. Four of 14 patients showed long-term progression-free survival (12-35 months), which directly correlated with the development of multifunctional CD8(+) T-cell responses in three of these patients. In particular, high CD107a expression, indicative for cytolytic activity, and IFNγ as well as TNFα and CCL4 production was observed. Apparently, these T-cell responses are essential to induce tumor regression and promote long-term survival by stalling tumor growth. CONCLUSIONS: We show that vaccination of metastatic melanoma patients with primary myeloid DCs is feasible and safe and results in induction of effective antitumor immune responses that coincide with improved progression-free survival. Clin Cancer Res; 22(9); 2155-66. ©2015 AACR.