Anti-LeY monoclonal antibody (mAb) hu3S193 as consolidation therapy for patients (pts) with relapsing platinum sensitive ovarian cancer (OC) after achieving a second complete response (2CR).

Abstract

e17039 Background: Lewis-Y (LeY) antigen is a blood group related antigen expressed in 75% of OC. hu3S193 is a humanized anti-LeY IgG1 mAb with strong complement and antibody dependent cytotoxicity with clinical benefit shown in a phase II study in pts with platinum-resistant OC and small tumor burden. Improving progression free survival (PFS) in pts who achieve a 2CR is an unmet need. Methods: This phase II study accrued pts with relapsed OC, LeY expression by IHC, and a KPS ≥ 70% who had achieved a 2CR after 5-8 cycles of platinum doublet chemotherapy (chemoRx). Patients received intravenous infusions of hu3S193, 30mg/m2every 2 weeks starting ≤ 8 weeks after the last dose of chemoRx and continuing for 12 doses (24 weeks) or until disease progression or unacceptable toxicity. Primary endpoint was PFS with a sample size calculated to detect a 50% increase in PFS, compared to a historical value of 10.8 months. Secondary objectives were safety and pharmacokinetics (PK). Results: 29 pts were enrolled. Median age: 55 yrs (range 29-67); Median KPS: 90% (range 80-100); LeY expression by IHC (N): strong (20), weak (9); stage at initial diagnosis: I/II (2), III/IV (27); median CA-125 prior to 2CR chemoRx: 104 (range 9-514); chemoRx agents to achieve 2CR: paclitaxel/platin (21), liposomal doxo/carboplatin (8); median cycles of prior chemoRx to achieve a 2CR:6; median doses of hu3S193 delivered: 10 (range 10-12). Evaluable pts: 28 (1 pt did not have 2CR); median PFS: 11.8 months (95% CI: 10.6-13.9) while 3 pts achieved PFS of 25+ months. Grade 4 toxicities observed: none. Most frequent toxicities (any grade/grade 3): Nausea (16/2), Vomiting (15/3), Hypersensitivity (9/0). PK data will be presented. Conclusions: Despite the good tolerance and the longer PFS compared to historical control, this trial did not show a significant improvement with hu3S193 as a consolidative strategy in patients with 2CR in platinum-sensitive OC. Tumor molecular analysis of patients with long PFS may provide insight for future studies. Clinical trial information: NCT01137071.