The European Commission has granted marketing authorization for TESARO, Inc.’s  ZEJULA drug. The once-daily oral drug is for the maintenance treatment of adult patients with epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in complete or partial response to platinum-based chemotherapy. The approved starting dose of the drug is 300 milligrams once per day.    This comes after ZEJULA’s FDA approval in March. It is currently the most frequently prescribed PARP inhibi...