Immunomodulatory switch maintenance therapy in metastatic colorectal carcinoma: The phase III IMPALA study.

TPS785 Background: The Toll-like receptor 9 agonist MGN1703 was compared to placebo in 59 metastatic CRC (mCRC) patients with disease control after standard induction chemotherapy in the double-blind randomized phase 2 IMPACT study. MGN1703 showed a superior effect over placebo, with a hazard ratio (HR) for the primary endpoint “PFS on maintenance” of 0.55 (p = 0.041) by local assessment and 0.56 (p = 0.070) by independent radiological review. Exploratory PFS analyses identified patients with objective RECIST response, normalized CEA and presence of activated NKT cells at the end of induction treatment to benefit the most from MGN1703. The OS evaluation showed a HR of 0.40 (median 24.5 vs. 15.1 months) for patients with RECIST response after induction therapy. Furthermore, at time of IMPACT study closure, 4 MGN1703 patients were still without progressive disease and continued treatment in compassionate use. As of August 2015, 3 patients were still receiving MGN1703 treatment in excess of three years (47-5...