Abstract PS4-06-15: Safety Run-In Phase of the ATRiBRAVE trial: a Phase II Study Evaluating Ceralasertib Priming Followed by Durvalumab/Nab-Paclitaxel to Restore Immunotherapy Sensitivity in Advanced Triple Negative Breast Cancer (TNBC)

Abstract Background: Preclinical studies have reported that Ataxia telangiectasia and Rad3-related (ATR) inhibition results in increased nuclear envelope fragility and promotion of cGAS-STING activation, thus potentially resulting in an enhanced immune response. The phase II investigator-initiated ATRiBRAVE trial evaluates the efficacy of the ATR inhibitor ceralasertib priming followed by durvalumab-nab-paclitaxel in patients with TNBC relapsing after immune checkpoint inhibitors (ICIs) and chemotherapy (CT) treatment in the curative setting.This report presents results from the safety run-in phase (SRP) of the trial, representing the first assessment of the safety and feasibility of the triple combination of ceralasertib, durvalumab and nab-paclitaxel in human. Methods: This single-arm trial enrolls patients with unresectable/metastatic TNBC (ER