Background: GemCis has long been the standard-of-care for advanced BTC, however the prognosis remains poor. Combinations with immunotherapy and GemCis are being explored in BTC. This study aimed to evaluate the efficacy and safety of TIS (an anti-PD-1 antibody) and OCI (a TIGIT inhibitor) combined with GemCis as the first-line treatment for advanced BTC. Herein, the primary analysis results of this study were reported. Methods: In this open-label, single-arm, multicenter phase 2 study, systematic treatment-naïve pts with unresectable advanced BTC received TIS (200 mg, day1, Q3W), OCI (900 mg, day1, Q3W), and GemCis (Gem 1000 mg/m² and Cis 25 mg/m² on days 1 and 8 Q3W, up to 8 cycles). The primary endpoint was investigator-assessed objective response rate (ORR) per RECIST v1.1. Secondary endpoints included disease control rate (DCR), duration of response (DoR), progression-free survival (PFS), overall survival (OS) and safety. A binomial exact test with a one-sided α of 0.05 was performed in the analysis of the primary endpoint to test the historical ORR of 25% with GemCis. If p≤0.05, the statistical superiority of the study treatment would be claimed. Results: A total of 45 pts were enrolled, with 75.6% having intrahepatic cholangiocarcinoma and 60.0% metastatic disease. As of 24 Aug 2023 (median follow-up, 8.0 months), 24.4% (11/45) pts remained on study treatment. Among the 41 pts in efficacy analysis set, confirmed ORR (cORR) was 48.8% (20/41, 95% CI, 32.9-64.9, p=0.0009), with 1 complete response. The statistical superiority was achieved. The subgroups of TIGIT⁺ pts tended to have numerically higher cORR (Table). Median PFS was 7.7 months, with 6-month PFS rate of 67.6%. Median OS was not reached, and 6-month OS rate was 86.2%. Grade ≥3 treatment-related adverse events rate was 60% (27/45). Immune-mediated adverse events rate was 37.8% (17/45), which were mostly grade 1 and 2. Conclusions: The combination of TIS and OCI plus GemCis showed promising anti-tumor activity with manageable safety as the first-line treatment for advanced BTC. Clinical trial information: NCT05023109.

^*Included pts with measurable disease at baseline per RECIST v1.1 who had ≥1 dose of study treatment and had ≥1 post-treatment tumor assessment unless clinical progressive disease or death occurred before the first assessment. NR, not reached; NE, not estimable.