Progenics Pharmaceuticals, Inc., a biopharmaceutical company, has acquired complete ownership and control of PSMA Development Company LLC (PDC), by purchasing Cytogen Corporation's interest in the joint venture which is developing in vivo cancer immunotherapies based on prostate-specific membrane antigen (PSMA).

PSMA is a protein primarily found on the surface of prostate cancer cells and new blood vessels associated with other solid tumours; therefore, targeting PSMA offers the potential for highly specific cancer therapy.

Progenics purchased Cytogen's 50 per cent interest in PDC in exchange for an upfront payment of $13.2 million in cash, plus potential future milestone payments totalling up to $52 million payable upon regulatory approval and commercialization, and an undisclosed royalty on future product sales. The technologies acquired in this purchase include those originating from Memorial Sloan-Kettering Cancer Center, the institution that first discovered PSMA, as well as those developed by PDC. The purchase encompasses the PSMA antibody-drug conjugate (PSMA ADC) and two vaccine products in development by PDC, a Progenics release said.

"We are committed to developing PSMA-based immunotherapies for prostate cancer that are potentially less toxic and more active than existing treatments," said Paul J. Maddon, M.D., Ph.D., Progenics' Founder, Chief Executive Officer and Chief Science Officer. "Having acquired all rights to in vivo PSMA immunotherapies, we now plan to develop them fully. Prostate cancer patients with metastatic disease have the greatest unmet medical need, and we intend to initiate phase 1 clinical studies in this setting in 2007 with our PSMA ADC. Progenics has core research and development, manufacturing, clinical, and regulatory teams in place and plans to leverage them to expedite PSMA-based drug development."

PSMA ADC is a fully human monoclonal antibody that specifically targets PSMA and is chemically linked to a cell-killing payload - auristatin, a highly potent synthetic drug. The linker is designed to be stable in the bloodstream and to release the drug payload under specific conditions once inside the targeted cancer cells, potentially sparing normal cells many of the toxic effects of traditional chemotherapy.

PSMA ADC has been tested in vitro and in animals for the ability to selectively eliminate prostate cancer cells. In laboratory studies, PSMA ADC killed PSMA-expressing prostate cancer cells at picomolar concentrations, whereas approximately 1,000-fold higher concentrations were required to kill cells that lack PSMA. PSMA ADC was similarly active against prostate cancer cells that were either sensitive to or resistant to androgen deprivation. In a recognized animal model, PSMA ADC showed activity against human prostate cancer cells and significantly prolonged overall survival.

To prevent the recurrence of prostate cancer after initial surgery or radiation therapy, PDC is also developing two PSMA-based therapeutic vaccine candidates to stimulate the immune system to recognize prostate cancer cells as foreign and to eliminate them. The Company has begun planning human testing of a viral-vector vaccine. Phase 1 clinical studies of a recombinant-soluble PSMA vaccine have shown that certain prostate cancer patients produced anti-PSMA antibodies in response to the vaccine. Progenics' research department is optimizing the vaccine before advancing this product candidate into phase 2 clinical testing.