TREATMENT OF HORMONE-REFRACTORY PROSTATE-CANCER WITH Y-90 CYT-356 MONOCLONAL-ANTIBODY

A Phase I dose-escalation study using Y-90-CYT-356 monoclonal antibody was performed in 12 patients with hormone-refractory prostate carcino ma, Biodistribution studies using In-111-CYT-356 were performed 1 week before Y-90-CYT-356 administration, Of the 12 patients, 58% had at le ast one site of disease imaged after administration of In-111-CYT-356, The dose of Y-90 ranged from 1.83-12 mCi/m(2), Both In-111 and Y-90-C YT-356 were tolerated well, without significant nonhematological toxic ity, Myelosuppression was the dose-limiting toxicity and occurred at d ose levels of 4.5-12 mCi/m(2), Of the patients receiving less than or equal to 9 mCi/m(2), 55% had grade 1 or 2 leukopenia and/or thrombocyt openia. Two of three patients treated with 12 mCi/m(2) experienced gra de 3 thrombocytopenia and leukopenia. One patient treated with 12 mCi/ m(2) had grade 4 neutropenia, The maximum tolerated dose of Y-90-CYT-3 56 was 9 mCi/m(2), Only one patient developed a human anti-mouse antib ody 4 weeks after treatment, No patient attained a complete or partial response based on prostate-specific antigen and/or radiological crite ria, Three patients had transient subjective improvement in the sympto matology of their disease, In addition, patients treated with 12 mCi/m (2) of Y-90-CYT-356 had a slightly longer freedom from disease progres sion than patients treated with doses of Y-90-CYT-356 less than or equ al to 9 mCi/m(2).