Updated efficacy and safety of KEYNOTE-224: A phase II study of pembrolizumab (pembro) in patients with advanced hepatocellular carcinoma (HCC).

518 Background: Pembro received accelerated approval in pts with advanced HCC in the second-line setting based on results of the KEYNOTE-224 trial. Results of a 2 y follow-up analysis of the efficacy and safety in this trial are presented here. Methods: Eligible pts had histologically confirmed HCC, radiographic progression on/intolerance to sorafenib and disease not amenable to curative treatment, Child Pugh A, ECOG PS 0-1 and BCLC stage C or B. Pts received pembro 200 mg IV Q3W for 2 y or until disease progression, unacceptable toxicity, consent withdrawal or investigator decision. Response was assessed every 9 wk. Primary endpoint was ORR (RECIST v1.1, central review). Secondary endpoints were DOR, DCR, PFS, OS and safety. Results: Efficacy and safety were assessed in 104 pts. The median time from randomization to data cutoff (Jun 05, 2019) was 31.2 mo (27.5-35.5 mo). Pt characteristics were: median age 68 y (43-87), 21.2% HBV+, 25% HCV+, 94.2% Child Pugh A, 79.8% had PD on sorafenib, 17.3% had MVI and 64.4% had extrahepatic disease. ORR was 18.3% (95% CI 11.4-27.1) and was similar across subgroups. Median DOR was 21.0 mo (3.1-28+ mo); 77% had responses lasting ≥12 mo (Kaplan Meier). Best overall responses were 4 (3.8%) CRs, 15 (14.4%) PRs, 45 (43.3%) SDs and 34 (32.7%) PDs; DCR was 61.5%. The median PFS (95% CI) was 4.9 mo (3.5-6.7) and OS was 13.2 mo (9.7-15.3). PFS 24 mo rate was 11.3% and OS 24 mo rate was 30.8%. ORR was shown to be a predictor of longer OS by landmark analysis. Treatment-related AEs occurred in 76 (73.1%) pts; the most common AEs were fatigue, increased aspartate aminotransferase, pruritus and diarrhea observed in ≥10% pts. Grade ≥3 treatment related AEs occurred in 27 (26.0%) pts. Immune-mediated hepatitis occurred in 3 (2.9%) pts; no cases of HBV/HCV flare were identified. Conclusions: At 2 y follow-up, pembro continued to provide durable anti-tumor activity and prolonged survival (30.8% OS, 24 mo rate), further supporting its use in previously treated pts with advanced HCC. With longer follow-up, increases in ORR (18.3% vs 17.0%), DOR ≥12 mo (77.0% vs 61.4%) and CR rates (3.8% vs 1%) were seen. The safety profile was similar to the primary analysis. Clinical trial information: NCT02702414.