Phase I open study of the effects of ascending doses of the cytotoxic immunoconjugate CMB-401 (hCTMO1-calicheamicin) in patients with epithelial ovarian cancer

Abstract

We have performed a phase I study of the cytotoxic immunoconjugate CMB-401 in women with epithelial ovarian cancer (EOC). CMB-401 is a directed chemotherapy that comprises a genetically engineered human antibody against polymorphic epithelial mucin, to which is attached covalently two to three molecules, on average, of the cytotoxic antibiotic calicheamicin. The primary objectives of this two-centre study were to identify end-organ toxicities and to establish the maximum tolerated dose (MTD). Thirty-four patients aged 37-75 years with progressive EOC not amenable to platinum/standard therapy, and with satisfactory WHO performance status (0-2) were recruited. Patients had received a mean of 3.2 previous chemotherapeutic regimens with a median interval since last chemotherapy of 182 days (range 34-1217). Patients received up to four cycles of a dual infusion of 35 mg/m2 hCTMO1 'predose' followed by doses of CMB-401 which were increased for each cohort--a regimen which minimises drug uptake in normal tissues whilst enhancing delivery to the ovarian tumour. CMB-401 dosing commenced at 2 mg/m2 and progressed via seven cohorts to 16 mg/m2. CMB-401 was generally well tolerated. However, transient fever and emesis occurred, necessitating routine prophylaxis, and increasingly significant malaise was reported as the dose increased. WHO grade 3-4 toxicities, irrespective of causality, included: anaemia 21%, granulocytopenia 9%, thrombocytopenia 9%, liver transaminases 3%, sepsis 3%, haemorrhage 6%, nausea/vomiting 76%; pulmonary 6%, and conscious state/somnolence 6%. The MTD was reached at 16 mg/m2. During the study four patients had a greater than 50% reduction in CA125, and three patients had radiological evidence of reduction in tumour bulk. CMB-401 appears to have an acceptable toxicity profile with demonstrable activity against EOC.