Toripalimab in advanced biliary tract cancer

Gemcitabine combined with platinum/fluorouracil drugs is the standard first-line treatment for advanced biliary tract cancers (BTCs). We explored the safety and efficacy of toripalimab plus gemcitabine and S-1 (GS) as the first-line treatment for advanced BTCs. At a one-sided significance level of 0.025, a total of 50 patients could provide 80% power to show the efficacy at targeted progression-free survival (PFS) rate at 6 months of 70% versus 40% for the combined treatment. This single-arm, phase II study enrolled 50 patients with advanced BTCs who previously received no systemic treatment. The regimen was as follows: toripalimab (240 mg, i.v., d1), gemcitabine (1,000 mg/m(2), i.v., d1 and d8), and S-1 (40–60 mg bid p.o., d1–14, Q21d). The primary endpoint was progression-free survival. The secondary endpoints included overall survival (OS), objective response rate (ORR), duration of response (DOR), and safety. The associations between response with PD-L1 expression, tumor mutational burden (TMB), and genetic variations were explored. Patients were enrolled from January 2019 to August 2020, with a median follow-up time of 24.0 months (IQR: 4.3–31.0 months). The 6-month PFS rate was 62%. The median PFS was 7.0 months (95% CI: 5.0–8.9 months), and median OS was 15.0 months (95% CI: 11.6–18.4 months). Forty-nine patients completed the evaluation for tumor response. The ORR was 30.6% (95% CI: 17.2%–44.0%), and the disease control rate was 87.8% (95% CI: 78.2%–97.3%). The most common treatment-related adverse events (TRAEs) were leukopenia (98.0%), neutropenia (92%), and anemia (86.0%). Grade III/IV TRAEs included leukopenia (38.0%), neutropenia (32%), skin rash (6%), anemia (2.0%), mucositis (2%), and immune-related colitis (2%). Among them, the grade III/IV immune-related adverse events (irAEs) were skin rash and colitis. In addition, biomarker analysis showed that negative PD-L1 expression and SMARCA4 mutation were significantly associated with worse survival outcomes, while no significant associations were observed for TP53, KRAS, or CDKN2A mutation as well as TMB. In conclusion, our data suggest that a regimen of toripalimab plus GS could improve PFS and OS with a good safety profile as a first-line treatment option for advanced BTC and warrants further verification.