Progenics’ PSMA ADC Therapeutic Drug Candidate
Targeted cancer therapies are medicines that selectively attack tumor cells while sparing healthy cells and tissues in the body. Unlike many conventional medicines that may damage cancer and healthy cells alike, targeted therapies are designed to selectively focus their activity at the site of the cancer. Such medicines typically exploit molecules or “targets” that are produced by cancer cells and may be important for tumor growth and progression.
The success of targeted therapies critically depends on finding targets that distinguish cancer from healthy cells. Targeted therapies can attack cancer in many different ways, such as intercepting signals that promote the growth of tumors, restricting their blood supply, helping the immune system to destroy the tumor, or delivering toxic drugs selectively to cancer cells. Targeted therapies are increasingly used for treating specific cancers, and many newer agents are in clinical testing.
PSMA ADC is Progenics’ targeted therapy that is in clinical testing for prostate cancer. PSMA ADC combines the molecular targeting of a monoclonal antibody with the tumor-killing activity of a potent toxin. Antibodies are Y-shaped proteins that tightly bind other molecules with exquisite specificity. The body normally produces large amounts of different antibodies to fight off infections. For a monoclonal antibody, many replicate copies of the same antibody are made outside the body. The monoclonal antibody portion of PSMA ADC binds a cancer marker known as prostate-specific membrane antigen, or PSMA. PSMA is present on the surface of nearly all prostate cancers but few healthy tissues in the body. PSMA is also found on the new blood vessels that supply nutrients to many other types of cancers. Targeted therapies may also offer the potential for doctors to tailor treatment based on the presence of the target in the tumor of a given patient. In such cases, doctors may perform tests to determine the presence, absence or relative abundance of a target prior to prescribing a particular course to treatment. When used properly, such tests can increase the chances that a patient will benefit from the selected treatment strategy.
PSMA flags cancer cells for destruction by PSMA ADC. In laboratory studies, PSMA ADC selectively binds PSMA on the surface of tumor cells and is then actively carried inside the cell by natural processes. Once inside the tumor cell, PSMA ADC releases a cell-killing dose of MMAE. In this way, PSMA ADC works like a Trojan horse to fight prostate cancer. In addition to the antibody, PSMA ADC contains a chemical toxin called monomethyl auristatin E, or MMAE. MMAE disrupts the microtubule filaments that give cells their shape, structure and ability to make new cells. MMAE is linked to the PSMA antibody through a chemical bond that is designed to be stable in the blood but efficiently released inside tumor cells.