Background: Tislelizumab, an anti-PD-1 monoclonal antibody, demonstrated clinical activity and was well tolerated in pts with previously treated advanced HCC in the phase 2 RATIONALE-208 study (NCT03419897). At the time of this study, SOR and LEN were recommended first-line treatments for pts with advanced HCC and continue to have an important role in the first-line treatment of HCC despite the recent approval of new immuno-oncology-based combinations (atezolizumab and bevacizumab) in some regions. We report the clinical outcomes of pts with advanced HCC who were previously treated with SOR/LEN. Methods: Pts who had received ≥1 prior line of systemic therapy for advanced HCC received tislelizumab 200 mg intravenously once every three weeks. Objective response rate (ORR) by independent review committee (IRC) (ORR_IRC), duration of response by IRC (DOR_IRC), progression-free survival by IRC (PFS_IRC), overall survival (OS), and safety were evaluated in pts who had been previously treated with SOR/LEN. Results: As of February 2020, 249 pts were enrolled and 235 pts had received prior treatment with SOR/LEN, of whom 126 and 109 pts had received 1 or ≥ 2 prior lines of systemic therapy, respectively. At study entry, 211 (89.8%) pts had BCLC stage C and 187 (79.6%) pts had extrahepatic spread. Median follow-up duration for pts previously treated with SOR/LEN was 12.5 months and ORR_IRC was 13.6% (95% CI: 9.5, 18.7), including 2 complete responses and 30 partial responses. Median DOR_IRCwas not reached. Median PFS_IRC and OS of pts previously treated with SOR/LEN was 2.7 months (95% CI: 1.6, 2.8) and 13.5 months (95% CI: 10.9, 15.8), respectively. Tislelizumab was generally well tolerated in pts previously treated with SOR/LEN (Table), and the most common treatment-emergent adverse events were increased aspartate aminotransferase (n=70; 28.1%) and alanine aminotransferase (n=52; 20.9%). Conclusions: Tislelizumab was investigated beyond the first-line setting, as effective second- and third-line treatment options are limited for pts with advanced HCC and there is an unmet medical need. This analysis indicates that tislelizumab is clinically active and well tolerated in pts with advanced HCC who have received prior systemic treatment with SOR/LEN. Clinical trial information: NCT03419897.

AE, adverse event; TEAE, treatment-emergent AE; TRAE, treatment-related treatment-emergent AE