United States Intergroup E1609: A Phase Iii Randomized Study Of Adjuvant Ipilimumab (3 Or 10 Mg/Kg) Versus High-Dose Interferon-Alpha 2b For Resected High-Risk Melanoma.

9504 Background: Phase III adjuvant trials reported significant benefits in relapse-free survival (RFS) for 6 FDA-approved regimens and overall survival (OS) for HDI and ipi10 versus observation or placebo. E1609 evaluated the relative safety and efficacy of ipi at 3 and 10 mg/kg compared to HDI, which was the adjuvant standard until recently. Methods: E1609 had 2 co-primary endpoints: OS and RFS; considered positive if either co-primary endpoint comparison was positive. Activated on 5/25/2011 and completed accrual 8/15/2014. A 2-step hierarchical approach evaluated ipi3 vs HDI followed by ipi10 vs HDI. Patients were stratified by AJCC7 stage (IIIB, IIIC, M1a, M1b). Based on protocol criteria, the primary evaluation was conducted using a data cutoff of 2/15/2019. Results: Final adult patient accrual was 1670; 523 randomized to ipi3, 636 to HDI and 511 to ipi10. Treatment related adverse events (AEs) Grade 3 or higher were experienced by 37% pts with ipi3, 79% with HDI and 58% with ipi10, and those of any grade leading to treatment discontinuation were 35% with ipi3, 20% HDI and 54% ipi10. AEs were mostly immune related and consistent with the known toxicity profiles of these agents. Gr5 AEs considered at least possibly related were 3 with ipi3, 2 with HDI and 8 with ipi10. First step comparison of OS and RFS of ipi3 vs. HDI utilized an ITT analysis of concurrently randomized cases (N = 1051) and showed significant OS difference in favor of ipi3; HR 0.78, 95.6% RCI (.61, 1.00); p = 0.044. The prespecified efficacy boundary was crossed. For RFS, HR 0.85, 99.4% CI (.66, 1.09), p = 0.065. In the 2nd step comparison of ipi10 vs. HDI (N = 989), there were trends towards improvement in OS [HR 0.88, 95.6% CI (.69, 1.12)] and RFS [HR 0.84, 99.4% CI (.65, 1.09)] in favor of ipi10 that were not statistically significant. Conclusions: Adjuvant therapy with ipi3 benefits survival of resected high-risk melanoma pts; for the first time in the history of melanoma adjuvant therapy, E1609 has demonstrated a significant improvement in the primary endpoint of OS against an active control regimen previously shown to have OS and RFS benefits, supporting early systemic adjuvant therapy for high-risk melanoma. Clinical trial information: NCT01274338.