Background: NIVO ± IPI is approved in previously treated pts with MSI-H/dMMR mCRC in the US, EU, and Japan, based on findings from the phase 2 CheckMate 142 study (NCT02060188). NCCN guidelines include NIVO + IPI as an initial therapy option for pts with MSI-H/dMMR mCRC. Results from a ~5-year follow-up from CheckMate 142 cohorts 1–3 (C1–3) are reported here. Methods: In this non-randomized, multicohort study, pts with MSI-H/dMMR mCRC were treated as follows: C1 (2L+; NIVO 3 mg/kg Q2W), C2 (2L+; NIVO 3 mg/kg + IPI 1 mg/kg Q3W [4 doses], followed by NIVO 3 mg/kg Q2W) and C3 (1L; NIVO 3 mg/kg Q2W + IPI 1 mg/kg Q6W), until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) by investigator assessment (INV) per RECIST v1.1. Other key endpoints were disease control rate (DCR), duration of response (DOR), progression-free survival (PFS), all by INV and blinded independent central review; overall survival (OS), and safety. Results: In C1 (N = 74), C2 (N = 119), and C3 (N = 45), median (range) follow-up (time from first dose to data cutoff) was 70.0 (66.2–88.7), 64.0 (60.0–75.8), and 52.4 (47.6–57.1) months (mo), respectively. ORR (95% CI) by INV was 39% (28–51), 65% (55–73), and 71% (56–84; Table) and progressive disease (PD) rates were 26%, 12%, and 16% in C1, C2, and C3, respectively. Median DOR was not reached in the 3 cohorts. The 48-mo PFS rates were 36%, 54%, and 51% and 48-mo OS rates were 49%, 71%, and 72% in C1, C2, and C3, respectively (Table). PFS and OS rates with up to 60 mo of follow-up will be presented. Safety data are shown in the table. Conclusions: With extended follow-up of ~5 years, NIVO ± IPI continued to demonstrate durable OS and PFS benefit, with no new safety signals. These updated data further support current treatment recommendations for 2L+ NIVO ± IPI and 1L NIVO + IPI for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT02060188.

^aStudy cohorts were neither randomized nor designed for a formal comparison; ^bINV; ^cPts with CR or PR divided by the number of treated pts; ^dPts with CR, PR, or SD (for ≥ 12 weeks) divided by the number of treated pts; ^eOne grade 5 event (sudden death). CR, complete response; NE, not estimable; PR, partial response; SD, stable disease.