Repligen Corporation announced that The United States Patent and Trademark Office (USPTO) has issued patent # 6,444,792 entitled "CTLA4-Cg4 Fusion Proteins". The patent, which will remain in force until 2016, covers the specific composition of the Company's CTLA4 product form, currently in development for autoimmune disease. This form of CTLA4 is structurally and functionally distinct from any previously patented form of CTLA4.

A CTLA4-Cg4 fusion protein is a genetically engineered form of CTLA4, which is comprised of a portion of natural sequence CTLA4, fused to a modified portion of an immunoglobulin (Ig) to eliminate its natural biological activity. The molecule covered by the patent has been engineered to eliminate those portions of the Ig molecule that have the potential to induce certain natural biological mechanisms, including cell lysis or cellular toxicity which may cause side effects in a patient.

"This patent recognizes the unique properties of our CTLA4 product form," said Walter C. Herlihy, President and CEO of Repligen. "We intend to pursue additional CTLA4 intellectual property rights licensed from the University of Michigan as well as continue to aggressively prosecute our rights to patents covering CTLA4 that are issued to Bristol-Myers Squibb."

CTLA4 is a T cell regulatory protein, which is one of the immune system's natural "off switches". We have developed a soluble form of CTLA4 (CTLA-Ig), which has immunosuppressive activity for use in organ transplantation and autoimmune diseases. CTLA4-Ig has the potential to inactivate only those cells that are initializing an unwanted immune response without compromising the body's ability to fight off infections. Bristol-Myers Squibb's form of CTLA4-Ig has been shown to be active in several clinical and non-clinical studies and was recently reported to have activity in a placebo-controlled Phase 2 trial in 214 patients with refractory rheumatoid arthritis.