Prostate-specific membrane antigen (PSMA) is a surface protein that is normally present on healthy prostate cells, but is found at much higher levels on prostate cancer cells. It is barely found in the rest of the body. Therefore, PSMA is an ideal target for diagnostic purposes as well as targeted therapies against prostate cancer. Now, researchers have developed a small molecule (PSMA-617) that is capable of specifically attaching to PSMA and can be labeled with various radioactive substances, called radionuclides. The research was published in the Journal of Nuclear Medicine.
When chemically bound to gallium-68, a weakly radioactive diagnostic radionuclide, PSMA-617 can be used to visualize even the smallest assemblies of prostate cancer cells in PET scans. This way, physicians are able to detect small secondary tumors or closely monitor response to therapy.
Alternatively, the researchers can also bind a therapeutic radionuclide called lutetium-177 to PSMA-617. This radiopharmaceutical is taken up by tumor cells that carry the PSMA target molecule and then destroys these cells from the inside. This might be a promising treatment option, particularly in cases of hormone-resistant prostate carcinoma, which is very difficult to treat.
Researchers have already used radioactively labeled PSMA-617 to treat individual patients with advanced prostate cancer, using the therapeutic nuclides lutetium-177 and actinium-225. After treatment with the lutetium-labeled radiopharmaceutical, levels of the prostate cancer marker PSA fell sharply in 70 percent of cases; after treatment with the actinium-labeled radiopharmaceutical, this effect was observed in all patients.
In addition, PET/CT images confirmed that metastases had shrunk or were no longer detectable. The results were so promising that the researchers plan to go ahead with a clinical trial as soon as possible to examine whether PSMA-617 is superior to other therapy methods.
Based on material originally posted by German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ).(Image source)