FOLR1 and ovarian cancer: During the expansion phase of the trial, 46 FRα-positive platinum resistant ovarian cancer (PROC) patients who had undergone up to five prior lines of therapy, when treated with IMGN853 at 6.0 mg/kg once every three weeks achieved an overall response rate (ORR) of 26%, median duration of response (DOR) of 19.1 weeks, and median progression-free survival (PFS) of 4.8 months.