Efficacy and safety of cancer vaccine with 4-fold gene-modified allogeneic tumor cells: Results of the phase I/II ASET study in patients with advanced renal cell carcinoma.

Abstract

4636 Background: MGN1601 was tested in the first-in-man phase I-II clinical study in patients with advanced renal cell carcinoma (RCC) who failed several previous therapy lines and had no further standard therapy available. MGN1601 consists of two active pharmaceutical ingredients in fixed combination: fourfold gene-modified allogeneic tumor cells expressing IL-7, GM-CSF, CD80 and CD154 through MIDGE vectors and a TLR-9 agonist, the immunomodulator dSLIM. Methods: The ASET study is a multicentric, single-arm phase I-II clinical trial. Clinical response was evaluated using CT scans (RECIST 1.1 or immune related Response Criteria, irRC). Efficacy data were evaluated in terms of PFS and OS for the intended to treat and the treated per protocol (TPP) populations, clinical parameters and quality of life. Immune response was determined using DTH to MGN1601, LTT assay, frequency and activation of blood cells, and mRNA, chemokine and cytotoxic T cells analysis as well as tumor tissue evaluation. Results: Nine of 19 included patients completed the TPP, the others discontinued the study earlier due to PD. Median PFS in the TPP group was 12 wks (3 months) and OS (not reached yet) 46 wks (11 months). Three patients achieved disease control (1 PR, 2 SD) after 12 wks. Two patients are continuing treatment in the extension phase and are progression free since 37 and 46 wks, respectively. Re-evaluation of tumor response data using irRC revealed 1 additional patient with a delayed tumor response 4 wks after treatment stop. Herewith, 4 out of 9 TPP patients (45%) achieved disease control. Of 7 patients receiving targeted therapy upon stop of study treatment, 4 had substantial objective responses, providing evidence that the study drug is able to render their tumors more vulnerable to subsequent therapies. Immune analysis showed trends towards increases of T-, NKT-cell and pDC frequencies and other immune parameters in those patients with clinical responses, indicating anti-tumor immunity of study treatment. Conclusions: The therapeutic cancer vaccine MGN1601 shows promising efficacy in late stage mRCC patients. Results warrant further clinical studies with MGN1601.