Synthetic Antibody Targets Prostate Cancer

Most prostate cancers at first are driven by male hormones — androgens — but they then become androgen independent, often spreading to other areas of the body. At this stage, treatment is difficult, but a new “smart drug” holds promise.

Researchers have developed an antibody, J591, that homes in on a specific molecule on prostate cancer cells. With a radioactive isotope attached, the antibody produced an anti-tumor effect in an early-stage (phase I) trial involving men with androgen-independent prostate cancer. Senior investigator Dr. Neil H. Bander told Reuters Health that the agent “can target prostate cancer metastases wherever they are in the body.” Accumulation of the isotope-tagged antibody at tumor sites, he added, “led to the delivery of therapeutic radiation only to tumor sites but not to normal tissues. As a result, patients tolerated the treatment very well.” Bander, of Cornell University Medical Center, and colleagues tested increasing doses of J591 in 29 patients with androgen-independent prostate cancer. None of the participants mounted an immune response to the compound, which might have limited its effectiveness, the researchers report in the Journal of Clinical Oncology One patient showed an 85 percent drop in prostate specific antigen (PSA) levels — an indicator of tumor suppression — which lasted for 8 months. Another had a decline of 70 percent for 8.6 months. Moreover, PSA levels stabilized in an additional six patients. Thus, Bander continued, “the potential benefit of this treatment approach was further supported by the finding of several significant anti-tumor responses.” “A phase II trial is approved, ” he added, “and expected to begin in the near future.” (SOURCE: Journal of Clinical Oncology: Reuters Health News: David Douglas: July 2004.