EFNA4 and breast cancer: Studies have shown that EFNA4 is involved in the proliferation and metastasis of glioma, ovarian cancer, chronic lymphocytic leukemia, and other tumors.5, 6, 7, 8 Moreover, the ADC drug PF-06647263, a conjugate of an EFNA4 monoclonal antibody and calicheamicins, provides a new therapeutic approach for the targeted therapy of patients with advanced breast cancer and ovarian cancer, offering outstanding pharmacokinetics and safety.9