Nivolumab (NIVO) + low-dose ipilimumab (IPI) as first-line (1L) therapy in microsatellite instability-high/DNA mismatch repair deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC): Clinical update.

3521 Background: In the phase 2 CheckMate 142 trial, NIVO + low-dose IPI provided robust and durable clinical benefit and was well tolerated as 1L therapy for MSI-H/dMMR mCRC (Lenz et al. Ann Oncol 2018;29:LBA18). Longer follow-up data will be presented. Methods: Patients with MSI-H/dMMR mCRC and no prior treatment for metastatic disease received NIVO 3 mg/kg every 2 weeks + low-dose IPI 1 mg/kg every 6 weeks until disease progression or discontinuation. The primary endpoint was investigator-assessed objective response rate (ORR). Results: For all 45 patients (median follow-up was 13.8 months), ORR was 60% (95% CI 44.3–74.3). Responses were consistent with the overall population across subgroups including age, Eastern Cooperative Oncology Group (ECOG) performance status, prior adjuvant/neoadjuvant therapy, and mutation status (Table). Seven patients (16%) had grade 3–4 treatment-related adverse events (TRAEs); 3 (7%) had any grade TRAEs leading to discontinuation. Updated response, survival, and safety data after a longer follow-up (median 19.9 months) will be presented. Conclusions: NIVO + low-dose IPI demonstrated robust and durable clinical benefit and was well tolerated. Evaluated subgroups had responses consistent with the overall population. NIVO + low-dose IPI may represent a new 1L treatment option for patients with MSI-H/dMMR mCRC. Clinical trial information: NCT02060188. [Table: see text]