It is typically overexpressed at a relatively low level, upto 50,000 receptors/cell,6 compared withHER2 (2 million receptors/cell).7 As oftoday, there are no HER3-targeting drugs approved for clinical use.HER3-targeting therapy has been evaluated in a clinical phase II trialwith the monoclonal antibody (mAb) seribantumab in combination withpaclitaxel for the treatment of ovarian cancer. Here, ERBB3 is linked to ovarian cancer.