BACKGROUND AND AIMS: We compared the safety and efficacy of bintrafusp alfa (BA) in combination with gemcitabine+cisplatin (GemCis), to those of GemCis alone, in patients with biliary tract cancer. APPROACH AND RESULTS: This randomized, double-blind, placebo-controlled, adaptive design phase 2/3 trial (NCT04066491) included adults who are treatment-naive with locally advanced/metastatic biliary tract cancer. Patients (N = 297) were randomized to receive an IV infusion of BA (2400 mg once/3 wk) plus GemCis (gemcitabine 1000 mg/m 2 +cisplatin 25 mg/m 2 on days 1 and 8/3 wk
8 cycles) (BA group, n = 148) or placebo+GemCis (placebo group, n = 149). The primary end point was overall survival (OS). For adaptation analysis (phase 2-phase 3
data cutoff: May 20, 2021), efficacy was assessed in the first 150 patients who were antibiotic-naive when 80 progression-free survival events had occurred and ≥ 19 weeks of follow-up had been completed (BA, n = 73
placebo, n = 77). Median OS (95% CI) for the BA (11.5 mo [9.3-not estimable]) and placebo (11.5 mo [10.0-not estimable]) groups was comparable (hazard ration 1.23 [95% CI 0.66-2.28]
p = 0.7394)
OS data maturity was 27.2% (41 events/151 patients). The most common grade ≥3 treatment-related adverse event was anemia (BA, 26.0%
placebo, 22.8%). Bleeding adverse events were reported more frequently in the BA group (28.8%) versus the placebo group (7.4%). Deaths within 60 days of the first dose were reported in 7.5% and 1.3% of patients in the BA and placebo groups, respectively. CONCLUSIONS: BA+GemCis did not provide a clinically meaningful benefit compared with GemCis alone as first-line treatment for biliary tract cancer, and the study was discontinued early (terminated: August 20, 2021).