Clinical experience with rhenium-186-labeled monoclonal antibodies for radioimmunotherapy: results of phase I trials.

Rhenium is a radionuclide with physical and chemical properties suitable for radioimmunotherapy. Two Phase I trials were carried out using 186Re-labeled murine monoclonal antibodies. Patients with refractory metastatic epithelial carcinoma received single doses of either 186Re-labeled intact NR-LU-10, a pancarcinoma antibody, 25-120 mCi/m2 (n = 15) or 186Re-labeled F(ab')2 fragment of NR-CO-02, an anti-CEA variant antibody, 25-200 mCi/m2 (n = 31). Prior to radioimmunotherapy, tumor localization of antibody was confirmed by 99mTc-labeled NR-LU-10 Fab or 99mTc-labeled NR-CO-02 F(ab')2 imaging. Dose-limiting myelosuppression was observed at 120 mCi/m2 following 186Re-NR-LU-10 intact antibody and at 150 mCi/m2 following NR-CO-02 F(ab')2 fragment in heavily pretreated patients. In patients with minimal prior therapy, a maximum tolerated dose for NR-CO-02 F(ab')2 was not reached by 200 mCi/m2. Non-marrow toxicity was minimal. Human anti-mouse antibody developed in all patients receiving intact NR-LU-10, and in 86% patients receiving F(ab')2 NR-CO-02. One patient treated with 186Re NR-CO-02 achieved a partial response. We conclude that 186Re-labeled antibody can be safely administered with significant toxicity limited to marrow.

Human anti-mouse antibody suppression with cyclosporin A.

BACKGROUND: Cyclosporin was used in an attempt to suppress the formation of human antimouse antibody (HAMA) after administration of murine monoclonal antibodies. METHODS: Thirteen patients were given oral cyclosporin (8.6-15 mg/kg/day) starting 2 days before administration of technetium-99m (99mTc) labeled F(ab')2 (3 patients) or Fab (10 patients) murine antibody fragment. Six to nine days later, patients received either rhenium-186 (186Re)-labeled F(ab')2 or an intact antibody. Cyclosporin was continued for 14 days after the second antibody administration. RESULTS: Five patients (38%) did not develop elevated HAMA titers for up to 8 weeks after antibody administration. These five patients had a median cyclosporin concentration of 726 ng/ml, while the eight patients who developed HAMA had a median cyclosporin level of 364 ng/ml. In contrast, when not given cyclosporin, 86% (24/28) of patients developed HAMA after receiving two doses of F(ab')2, and 100% (15/15) developed HAMA after receiving Fab followed by intact antibody. Toxicity from cyclosporin included elevation concentrations of bilirubin and creatinine, and increased blood pressure, which rapidly resolved after the cyclosporin was discontinued. CONCLUSIONS: This study demonstrates that cyclosporin given from 2 days before until 2 weeks after administration of either a F(ab')2 or intact murine antibody can suppress HAMA formation. This strategy may permit administration of repeated doses of murine-antibody-based radioimmunotherapy.