Objective: 776.1 is a monoclonal antibody prepared against the human ovarian cancer antigen CA 125 that demonstrates preferential binding to the cell-associated form of the antigen and has shown promising results as an yttrium-90-labeled antibody in pre-clinical studies examining the effects on tumor growth in a murine xenograft model of human ovarian cancer. The purpose of the present study was to examine the effects of combined therapy with [90Y-DOTA]776.1 and paclitaxel compared with monotherapy with either agent on the growth of OVCAR-3 xenografts in nude mice.
Methods: Mice bearing OVCAR-3 xenografts were treated with paclitaxel alone, 50 microCi or 150 microCi [90Y-DOTA]776.1 alone, or a combination of both treatments. Control groups were included which consisted of a nonspecific antibody, MOPC-21, labeled to a similar degree, administered as monotherapy or in combination with paclitaxel. The effects of administration of radioimmunotherapy prior to or following chemotherapy were also examined.
Results: Treatment with paclitaxel and [90Y-DOTA]776.1 had a synergistic anti-tumor effect on the growth of OVCAR-3 xenografts. Synergy was only observed when a tumor-specific antibody was used in radioimmunotherapy. While no difference in tumor growth was observed with order of dosing, reduced toxicity was seen when paclitaxel was administered prior to radioimmunotherapy.
Conclusion: The combination of radioimmunotherapy using an anti-CA 125 monoclonal antibody and chemotherapy with paclitaxel was shown to be effective in an in vivo model of ovarian cancer and may hold promise as a treatment regimen for patients with ovarian cancer.