ORIENT-32: Updated characterization of response to sintilimab plus bevacizumab biosimilar (IBI305) vs sorafenib for unresectable hepatocellular carcinoma.

570 Background: ORIENT-32 trial (NCT03794440) assessed sintilimab (anti-PD-1 antibody) plus a bevacizumab biosimilar (anti-VEGF antibody) versus sorafenib (Sor) as first-line treatment for unresectable HCC and demonstrated a significant improvement in both overall survival and progression-free survival. Here we report the updated results of objective response rate (ORR), time to response (TTR), duration of response (DoR) and depth of response (DpR). Methods: 571 eligible patients (pts) with unresectable HCC were enrolled and randomized (2:1) to receive sintilimab (200 mg IV Q3W) plus IBI305 (15 mg/kg IV Q3W) or Sor (400 mg orally, BID) until disease progression or unacceptable toxicity. Tumors were evaluated using Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1)and HCC-modified RECIST (mRECIST). ORR, TTR, DoR, and DpR were analyzed. The DpR was defined as the minimum percentage of (1) sum of longest diameter (SLD) change and (2) longest diameter (LD) change described as mean (standard deviation, SD). Results: At the data cutoff on Dec 30th, 2021, the median follow-up time was 26.7 months. The ORR in sintilimab plus IBI305 and Sor group was 21.0% (77/367) vs 4.7 (8/169) per RECIST 1.1 and 25.1% (92/367) vs 7.7% (13/169) per mRECIST. The median TTR in sintilimab plus IBI305 group was 2.8 (2.4–3.3) months per RECIST 1.1 and 2.6 (1.6–2.9) months per mRECIST. The median DoR in sintilimab plus IBI305gourp was 20.3 (12.3-NE) months per RECIST 1.1. The minimum percentage of SLD change was larger in the sintilimab plus IBI305 arm than in the Sor arm: (−13.4% (35.8) vs 3.2%(26.5) per RECIST 1.1). Similarly, the LD change in the largest liver lesion also favored sintilimab plus IBI305 arm (−27.6% (31.6) vs −11.5% (20.9)), including larger tumors (≥7 cm; −21.2% (30.4) vs −9.9% (23.7)) all per RECIST 1.1. Conclusions: Sintilimab plus IBI305 showed a significant improvement in ORR, TTR, DOR and DpR vs Sor in unresectable HCC. Clinical trial information: NCT03794440 .