Experimental prostate cancer combo shows promise in case studies

Dr. Matthias Eder

Dr. Matthias Eder of the German Cancer Research Center has been working on a new molecule that targets prostate-specific membrane antigen (PSMA), a protein that clusters on the surface of prostate cancer cells.

Eder and his colleagues report that when you combine PSMA-617 with a weak radioactive diagnostic radionuclide it's possible to spot even small numbers of prostate cancer cells with positron emission tomography scans. And moving beyond the diagnostic approach, they're working on combining their drug with therapeutic radionuclide called lutetium-177, which can destroy targeted prostate cancer cells. That approach may be particularly effective for cases of hormone-resistant prostate carcinoma.

"PSMA is an ideal target for diagnostic purposes as well as targeted therapies against prostate cancer," says Eder.

Dr. Uwe Haberkorn at Heidelberg University has already tested this approach in individuals, noting that the lutetium-177 combo cut PSA levels in 70% of the cases studied. Combined with actinium-225, the drug had a 100% response rate. And now that they have laid the groundwork, the plan is to follow up with clinical studies to test its safety and efficacy for the disease.

"Other agents that target PSMA and can be coupled with strong or weak radiation emitters are already being developed," explains Prof. Dr. Klaus Kopka, a chemist and departmental head at the DKFZ. "However, only a few of these agents have turned out to be ideal. Most of them are too unstable, accumulate insufficiently in cancer cells and wash out too slowly from healthy organs. By contrast, PSMA-617 accumulates in large quantities in tumors and metastases and is stored well in cancer cells. As a result, prostate cancer can be irradiated from the inside, so to speak."

Eder, radiochemist Martina Benešová, Klaus Kopka, Uwe Haberkorn and their co-workers have now received the Image of the Year Award and the Berson-Yalow Award at the 2015 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging for their work on PSMA-617.

- here's the release