Multicenter phase 1-2 trial of patritumab deruxtecan for previously treated HER3 expressing metastatic breast cancer

High expression of HER3 in breast cancer is associated with an adverse prognosis. Patritumab derextecan (HER3-DXd) is an HER3-targeted antibody-drug conjugate. A phase 1-2 trial at centers in Japan and the USA evaluated HER3-DXd for heavily pretreated (median five previous lines of therapy) patients with HER3-expressing metastatic breast cancer (mBC). The safety profile was manageable. HER3-DXd demonstrated durable efficacy across clinical subtypes. The authors conclude that these data warrant further evaluation of HER3-DXd in patients with HER3-expressing mBC.