The compound CMB-401 is an immunoconjugate consisting of the monoclonal antibody (MAb) hCTM01 directed against polymorphic epithelial mucin covalently bound to the cytotoxic antibiotic calicheamicin by an amide linker. We evaluated CMB-401 as monotherapy for the treatment of recurrent platinum-sensitive epithelial ovarian carcinoma (EOC). Twenty-one 21 women aged 38 to 80 years with recurrent EOC (recurrence >6 months after initial platinum-containing chemotherapy) were enrolled. Tumor response and serum cancer antigen 125 (CA125) levels were assessed before and after active treatment. After an initial intravenous (i.v.) dose of hCTM01 (without calicheamicin), the calicheamicin-linked CMB-401 (16 mg/m(2 ) i.v.) was administered over 60 min for up to 7 cycles, with 4 weeks between cycles. Nineteen patients were evaluable. Measurable changes observed following administration of CMB-401 did not meet the criteria for partial remission (PR). CMB-401 was not effective as monotherapy for this type of EOC. Adverse events experienced by patients in the study included nausea (95%), asthenia (90%), abdominal pain (62%), headache (57%), anorexia (57%), and diarrhea (57%), mostly at a toxicity grade level of 1 or 2. Based on published efficacy of conjugates that deliver calicheamicin via hybrid (bifunctional) linkers [e.g. gemtuzumab ozogamicin (Mylotarg) in acute myeloid leukemia], we hypothesize that the amide linker used in CMB-401 may have contributed to its failure to induce PR in patients in this study. Use of hybrid linkers to target hCTM01 or other antibodies to EOC may warrant further investigation.