CYTOGEN LAUNCHES TRIAL OF PSMA ANTIBODY

Cytogen has announced the initiation of the first human clinical study of CYT-500, a radiolabeled monoclonal antibody that targets prostate-specific membrane antigen (PSMA). The Phase I clinical trial will investigate the safety and tolerability of CYT-500 and determine the optimal antibody mass and therapeutic dose for further studies. The trial is expected to enroll up to 36 patients.

CYT-500 employs the same monoclonal antibody as Cytogen's molecular imaging agent Prostascint (capromab pendetide); however, it is linked to lutetium 177, a particle emitting therapeutic radionuclide, as opposed to an imaging radionuclide. This novel product candidate is designed to enable targeted delivery of high doses of radiation to PSMA-expressing cells. PSMA is a protein abundantly expressed on the surface of prostate cancer cells, with an increased expression in high-grade cancers, metastatic disease and hormone-refractory prostate cancer.

Preclinical pharmacokinetic and biodistribution studies of CYT-500 demonstrated that the compound is stable in serum, accumulates at the tumor site and clears from normal organs and tissues. Acute and expanded toxicology studies and safety pharmacology studies with unlabeled doses up to 20 times the anticipated human dose did not reveal significant adverse reactions.

In contrast to other prostate-related antigens such as prostate-specific antigen, prostatic acid phosphatase and prostate secretory protein, PSMA is a membrane glycoprotein that is not secreted. This attribute makes PSMA an excellent target for monoclonal antibody therapeutic options for prostate cancer, according to the company.