Phase II study of interferon-enhanced I-131-labeled high affinity CC49 monoclonal antibody therapy in patients with metastatic prostate cancer

Adjuvant Interferon (IFN) was given to increase tumor antigen expression an d enhance localization with I-131-labeled CC49 radioimmunotherapy in a Phas e II trial for hormone resistant metastatic prostate cancer. Patients recei ved four doses of alpha-IFN (3 x 10(6) IU) s.c. on alternate days, from day -5 to day +1 of 75 mCi/m(2) I-131-CC49 treatment. Toxicity was well tolera ted, with the majority of patients experiencing transient grade 3 or 4 neut ropenia and/or thrombocytopenia (maximal at 4-6 weeks). The absorbed dose w as >25 Gy in four of eight tumors visualized, which represents an increase of > 20 fold over whole body radiation dose. Two patients had radiographic minor responses by 6 weeks post-therapy, whereas five of six patients exper iencing pain had symptom relief without radiographic changes. The protocol provided modest antitumor effects (pain relief in five of six patients and two minor radiographic responses). This study suggests that the addition of IFN enhanced tumor uptake and antitumor effects as compared to a prior Pha se II trial of I-131-CC49 alone.