Purpose <p>Durvalumab in combination with gemcitabine/cisplatin has shown a favorable benefit-risk profile in the TOPAZ-1 study for advanced biliary tract cancers (BTC). This analysis evaluated the population pharmacokinetics (PopPK) of durvalumab, and exposure-response for efficacy and safety (ERES) of TOPAZ-1.</p> Methods <p>The PopPK model for durvalumab was updated using data from 5 previously analysed studies and TOPAZ-1. Individual exposure metrics were derived from the individual empirical Bayes estimates as drivers for exposure-response (ER) analysis related to efficacy and safety.</p> Results <p>Consistent with previous analyses, the durvalumab pharmacokinetics in BTC followed a 2-compartment model with time-dependent clearance. The final population parameters were: CL, 0.298 L/day; V1, 3.42 L; V2, 1.99 L; Q, 0.452 L/day; and the time dependent clearance suggests that the clearance could decrease up to 39% over the time course of treatment. There were 111 patients (3.53%) with treatment-emergent ADA positive in the pooled group of 6 studies, and the exposure was comparable for ADA positive and negative patients. Covariates had minimal clinical impact on PopPK parameters. No significant associations were found between exposure and overall survival (OS), progression-free survival (PFS), using Cox proportional analysis (CPH). Logistic regression analysis indicated no significant relationship between the exposure and relevant adverse events measures of Grade 3 and higher treatment-related AE, Grade 3 and higher treatment-related AESI (AEs of special interest), or AE leading to treatment discontinuation.</p> Conclusions <p>No dose adjustment for durvalumab is needed based on PopPK and ERES analyses. The analysis supports the TOPAZ-1 regimen for patients with advanced BTC.</p>