Preliminary single agent activity of IMGN853, a folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC), in platinum-resistant epithelial ovarian cancer (EOC) patients (pts): Phase I trial.

5518 Background: IMGN853 (mirvetuximab soravtansine) is a FRα-targeting ADC that comprises a FRα-binding antibody conjugated with the potent maytansinoid, DM4. Methods: This phase I trial evaluates the safety, pharmacokinetics, pharmacodynamics and anti-tumor activity of IMGN853 in pts with FRα-positive solid tumors. A recommended phase II dose (RP2D) of 6.0 mg/kg, administered once every three weeks using adjusted ideal body weight was established in the dose-finding phase. Preliminary evidence of antitumor activity is being investigated at the RP2D in disease-specific cohorts of pts with platinum-resistant EOC and relapsed/refractory endometrial carcinoma. Here we report preliminary clinical activity (partial PR or complete CR response, CA125 response, SD ≥ 6 cycles) at the RP2D in pts with platinum-resistant EOC. Results: To date, 14 platinum-resistant EOC pts have been treated at the RP2D: 2 in dose escalation; 12 in the expansion cohort. All pts were heavily pretreated (mean: 4.5; range 2-12 prior tr...