Gastrointestinal tumors, colorectal

ABSTRACT Introduction Standard chemotherapy is increasingly discontinued after successful “induction” in patients (pts) undergoing 1st line treatment for mCRC. MGN1703 is a synthetic DNA-based immunomodulator acting as an agonist of TLR-9 that has shown preclinical activity in mCRC. This study has been conducted to assess clinical efficacy, immunogenicity, and safety of MGN1703 as maintenance vs. placebo. Methods The IMPACT study is an international, multicenter, randomized double-blind placebo-controlled phase II/III study. Pts with mCRC showing disease control (CR, PR or SD) after 4.5 to 6 months of 1st-line standard therapy with FOLFOX/XELOX or FOLFIRI +/- bevacizumab (investigatoŕs choice) were included. Results Interim analysis of the unblinded data revealed a strong therapeutic effect compared to anticipated PFS. Therefore, patients were withheld from further randomization, according to a decision of the steering committee. In the ITT population (N = 55 pts), hazard ratio (HR) was 0.53 in favor of MGN1703 (p = 0.062). In the per-protocol population (excluding screening failures; N = 50), HR was 0.43 (p = 0.015). In the pre-defined target population (2 out of 3 factors: CEA Conclusions Maintenance therapy with MGN1703 after standard chemotherapy with or without bevacizumab, is associated with significantly improved progression-free survival compared to placebo and is accompanied by low toxicity. A confirmatory clinical study in patients with metastatic CRC is currently being planned. Disclosure M. Tschaika: Employment, stock ownership. M. Schmidt: Employment. B. Wittig: Stock ownership. All other authors have declared no conflicts of interest.