For the second question, preclinical models established 20 μg/mL as the minimum TRA concentration (Cmin) that achieved maximum tumor growth inhibition.6 Although no studies exist on the PK of the intravenous fixed-dose regimen, one study of interest7 investigated the PK of a subcutaneous fixed dose of 600 mg in 19 patients with nonmetastatic human epidermal growth factor receptor 2–positive breast cancer. The gene discussed is ERBB2; the disease is breast cancer.