Primary results from IMpassion131, a double-blind, placebo-controlled, randomised phase III trial of first-line paclitaxel with or without atezolizumab for unresectable locally advanced/metastatic triple-negative breast cancer

•The phase III IMpassion131 trial evaluated atezolizumab combined with paclitaxel as first-line therapy for aTNBC.•The primary endpoint was investigator-assessed PFS, tested hierarchically in the PD-L1+ and then ITT populations.•Neither PFS nor OS improved combination of plus either population.•These findings may result from imbalances prognostic features or chance a relatively small trial.•IMpassion131 results highlight need further research into immunotherapy TNBC. BackgroundIn IMpassion130 trial, combining nanoparticle albumin-bound-paclitaxel advanced triple-negative breast cancer (aTNBC) showed statistically significant progression-free survival (PFS) benefit intention-to-treat (ITT) programmed death-ligand 1 (PD-L1)-positive populations, clinically meaningful overall (OS) effect PD-L1-positive aTNBC. The KEYNOTE-355 adding pembrolizumab to chemotherapy aTNBC similar effects. atezolizumab–paclitaxel aTNBC.Patients methodsEligible patients [no prior systemic ≥12 months since (neo)adjuvant chemotherapy] were randomised 2:1 840 mg placebo (days 1, 15), both 90 mg/m2 8, every 28 days until disease progression unacceptable toxicity. Stratification factors tumour PD-L1 status, taxane, liver metastases geographical region. first [immune cell expression ≥1%, VENTANA (SP142) assay] population, population. secondary endpoint.ResultsOf 651 patients, 45% had At analysis, did not improve population [hazard ratio (HR) 0.82, 95% confidence interval (CI) 0.60-1.12; P = 0.20; median 6.0 versus 5.7 placebo–paclitaxel]. In associated more favourable unconfirmed best response rate (63% 55% placebo–paclitaxel) duration (7.2 5.5 months, respectively). Final no difference between arms (HR 1.11, CI 0.76-1.64; 22.1 28.3 placebo–paclitaxel population). Results consistent safety profile known effects each study drug.ConclusionCombining alone.ClinicalTrials.govNCT03125902. Eligible endpoint. Of drug. Combining alone.