A phase Ib/II trial of atezolizumab with cobimetinib or idasanutlin in metastatic estrogen receptor positive breast cancer.

ABSTRACT: Despite the availability of numerous treatment options for metastatic estrogen receptor positive breast cancer, additional strategies are needed, particularly when tumors become endocrine resistant. This phase Ib/II study examined the clinical activity and safety of the novel combination of atezolizumab with molecularly targeted therapy inhibiting 1) the Ras/Raf/MEK signaling pathway with cobimetinib in TP53-mutant tumors (arm COBI) or 2) the TP53 regulator MDM2 with idasanutlin in TP53-wild-type tumors (arm IDA). Twelve patients were enrolled before the study closed early due to slow accrual. 2/7 patients in arm IDA had durable responses to treatment. 1/5 patients in arm COBI had stable disease. Interestingly, conservation of tumor-specific HLA-ABC expression was observed in nearly all pa

SUBMITTER: Mezzanotte-Sharpe J 

PROVIDER: S-EPMC12182567 | biostudies-literature | 2025 Jun

REPOSITORIES: biostudies-literature