Abstract

e16158 Background: PD-1 or PD-L1 inhibitors plus chemotherapy as the first-line treatment has been proven to be effective in improving the prognosis of advanced biliary tract cancer (BTC) patients. However, there is still considerable demand for further improvement of BTC patients’ prognosis. This trial aims to evaluate the efficacy and safety of Cadonilimab (PD-1/CTLA-4, a bi-specific antibody) plus gemcitabine and cisplatin for patients with advanced BTC in first -line treatment. Methods: In this phase II, single-arm trial, we will enroll 65 patients with previously untreated, unresectable, locally advanced or metastatic BTC, including intrahepatic or extrahepatic cholangiocarcinoma (ICC/ECC) and gallbladder carcinoma (GBC). Participants received Cadonilimab (10 mg/kg, days 1, every three weeks) plus gemcitabine (1000 mg/m 2 , days 1, 8, Q3W), and cisplatin (25 mg/m 2 , days 1, 8, Q3W) for up to eight cycles, followed by Cadonilimab (10 mg/kg, days 1, Q3W) until disease progression or unacceptable toxicity. Treatment response was evaluated with image-based assessment according to response evaluation criteria insolid tumors (RECIST) version 1.1. by two experienced experts and further explored multiple methods, such as 3D visualisation and Spectral computed tomography Scan. The primary endpoint was the objective response rate (ORR); the secondary endpoints are disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety. Exploratory endpoints included associations between response, molecular characteristics, and the immune microenvironment. Results: Between June 30, and January 31, 2024, a total of 30 patients have undergone at least one imaging evaluation. 66.7% of these patients were diagnosed with ICC, 23.3% with GBC, and 10% with ECC. The mean age was 58.4 years, and 60% of the patients were male. 24 (80%) patients had metastasis. Among them, 1 (3.3%) patient acheived complete response (CR), 15 (50%) patients had partial response (PR) and 8 (26.7%) patients presented with stable disease (SD). The ORR was 53.3% and the DCR was 80%. The most common treatment-related adverse events (TRAEs) of any grade were rash (80%) and anaemia (76.7%). Grade 3 TRAEs were observed in 66.7% of the patients. The most frequent grade 3 TRAEs were anaemia (33.3%), and leukocytopenia (33.3%). No grade 4 or 5 events were observed. All patients were microsatellite stable (MSS), and the median TMB was 2.88 (0-109.44) Muts/Mb. Conclusions: Cadonilimab plus gemcitabine and cisplatin shown a promising efficacy and acceptable safety profile as first-line treatment for advanced BTC patients. Clinical trial information: NCT05978609 .