The anti-idiotypic antibody abagovomab in patients with recurrent ovarian cancer. A phase I trial of the AGO-OVAR

Background: Abagovomab is a murine anti-idiotypic antibody against the antigen CA-125 which has been shown to elicit humoral and cellular immune responses against ovarian cancer (oc). Patients and methods: This phase I trial included 36 patients with recurrent oc comparing two subcutaneous (s.c.) vaccination schedules: nine (group L) versus six injections (group S), 18 patients in each group. Four injections of 2.0 mg abagovomab were administered every 2 weeks and then two or five additional doses monthly. Primary endpoint was drop-out rate due to toxicity, and the secondary endpoint was analysis of immunological response. Results: Treatment was completed in eight (44%) and 16 (89%) patients in groups L and S, respectively. Premature termination occurred due to patient withdrawal or disease progression. No treatment-limiting toxicities occurred in either group. The most common toxicity related to the vaccine was grade 1/2 local injection site reaction. Induction of Ab3 was observed in all evaluable patients. There were no differences between the groups with regard to induction of human anti-mouse antibody (P = 0.1006). IFN gamma-expressing CA125-specific CD8+ T-cells were significantly more frequent in group L, while there was no significant difference between CD4+ T-cells in the two groups. Conclusions: Abagovomab s.c. vaccination is safe and well tolerated. The long vaccination schedule tended to be more effective with regard to AB3-induction and cellular cytotoxicity.