The aim of this phase I/II nonrandomized trial was to assess feasibility, safety as well as immunological and clinical responses of a mRNA-based vaccination in patients with stage IV renal cell cancer using granulocyte-macrophage colony stimulating factor (GM-CSF) as adjuvant. Intradermal injections of in vitro transcribed naked mRNA, which was generated using plasmids coding for the tumor-associated antigens mucin 1(MUC1), carcinoembryonic (CEA), human epidermal growth factor receptor 2 (Her-2/neu), telomerase, survivin, and melanoma-associated antigen 1 (MAGE-A1) were performed in 30 enrolled patients. In the first 14 patients (cohort A) vaccinations were administered on days 0, 14, 28, and 42 (20 µg/antigen) while in the consecutive 16 patients (cohort B) an intensified protocol consisting of injections at days 0-3, 7-10, 28, and 42 (50 µg/antigen) was used. In both cohorts, after this induction period, vaccinations were repeated monthly until tumor progression analyzed by Response Evaluation Criteria In Solid Tumors criteria (RECIST). Vaccinations were well tolerated with no severe side effects and induced clinical responses [six stable diseases (SD) and one partial response in cohort A and nine SD in cohort B]. In cohort A, 35.7% survived 4 years (median survival 24 months) compared to 31.25% in cohort B (median survival 29 months). Induction of CD4(+) and CD8(+) T cell responses was shown for several tumor-associated antigens (TAA) using interferon-γ (IFN-γ) enzyme-linked immunosorbent spot (ELISpot) and Cr-release assays.

Renal cell carcinoma (RCC) is an immunogenic tumor for which immunotherapeutic approaches could be associated with clinically relevant responses. It was recently shown, that induction of T-cell responses against multiple tumor-associated antigen (TAA) epitopes results in prolonged overall survival in RCC patients. In 2003–2005, we performed a phase I/II trial testing an mRNA-based vaccine formulation consisting of a mixture of in vitro transcribed RNA coding for six different TAAs (MUC1, CEA, Her2/neu, telomerase, survivin, MAGE-A1) in 30 metastatic RCC (mRCC) patients. In the first 14 patients, vaccinations were applied i.d. on days 0, 14, 28, and 42. In the consecutive 16 patients, an intensified protocol consisting of i.d. injections (daily on days 0–3, 7–10, 28, and 42) was used. After the respective induction periods, patients in both cohorts were vaccinated monthly until tumor progression. At survival update performed in July 2015, one of the 30 patients was still alive. One patient was lost to follow-up. Median survival of 24.5 mo (all patients) and 89 mo (favorable risk patients) exceeded predicted survival according to Memorial Sloan Kettering Cancer Center (MSKCC) risk score. Impressively, long-term survivors displayed immunological responses to the applied antigens while vice versa no patient without detectable immune response had survived more than 33 mo. The current survival update shows a clear correlation between survival and immunological responses to TAAs encoded by the naked mRNA vaccine. This is one of the first vaccination studies and the only RNA trial that reports on safety and efficacy after a follow-up of more than 10 y.

Introduction Recently Walter et al. (Nature med 2012) demonstrated that induction of T cell responses to tumor-associated antigens (TAA) after peptide vaccination (IMA901) is associated with significantly prolonged overall survival in patients with advanced renal cell carcinoma (RCC). Between August 2003 and November 2005 we performed a phase I/II non-randomized study to analyze the feasibility and safety of an mRNA-based vaccination as well as immunological and clinical responses in patients with stage IV RCC (Rittig et al., Mol Ther. 2011). Here we provide an update on survival and correlative analyses of immunological responses and survival. Methods: In vitro transcribed naked mRNA coding for the TAAs mucin 1, carcinoembryonic antigen (CEA), human epidermal growth factor receptor (EGFR) 2, telomerase, survivin, and melanoma-associated antigen 1 was administered to a total of 30 patients. In the first 14 patients (cohort A), vaccinations were applied on days 0, 14, 28, and 42 (20 µg of each antigen). In the consecutive 16 patients (cohort B), an intensified protocol consisting of injections at days 0-3, 7-10, 28, and 42 with 50 µg/antigen was used. After the respective induction periods, patients in both cohorts received monthly vaccinations until tumor progression according to RECIST. Results: In October 2010 monitoring had revealed a survival in cohort A ranging from 3 to 85 months with 4/14 patients (29%) being alive, while survival in cohort B ranged from 2 to 71 months with 4/16 (25%) patients being alive. Follow up was re-assessed in March 2013. In cohort A, 3 patients were still alive (21%) with survival ranging from 105 to 115 months. Two of these surviving patients had intermediate and one had favourable risk according to Motzer score at enrolment. These respective patients had received between 13 and 32 doses of RNA. In cohort B, three patients (19%) were found to be alive, of which two had favourable and one had intermediate risk according to Motzer score at enrolment. Survival in cohort B ranged from 95 to 97 months, and between 10 and 22 doses of the vaccine had been applied to the patients. Impressively and similar to the findings of Walter et al. with the IMA901 peptide vaccine, all six patients that currently are alive displayed immunological responses to the applied antigens in cytotoxic T cell or ELISpot assays, while vice versa no patient without detectable immune response had survived more than 33 months. Conclusion: The current survival update revealed long term survival (>8 years) in about 20% of patients in this small cohort suffering from stage IV RCC. Notably, in line with data obtained after peptide vaccination, prolonged survival after treatment with our RNA vaccine also showed a clear correlation with in vitro detectable immunological responses to the applied TAA. Disclosures: No relevant conflicts of interest to declare.