New FDA Orphan Drugs: CellCept, Prochymal, Shiga Toxin Antibodies

Yael Waknine

January 09, 2006

Jan. 9, 2006 — The FDA has approved orphan drug status for mycophenolate mofetil for the treatment of myasthenia gravis; an adult stem cell product for the treatment of acute graft vs host disease; and 2 therapeutic monoclonal antibodies for the treatment of Shiga toxin-producing Escherichia coli infections.


Orphan Drug Mycophenolate Mofetil (CellCept) for Myasthenia Gravis

On January 3, the FDA approved orphan drug status for the immunosuppressant drug mycophenolate mofetil (CellCept, made by Aspreva Pharmaceuticals Corporation and Roche) in the treatment of myasthenia gravis (MG).

MG is a debilitating, chronic autoimmune neuromuscular disease that can affect any voluntary muscle but most frequently involves those controlling eye movements, chewing, swallowing, coughing, and facial expressions.

Current treatments include cholinesterase inhibitors, steroids, and other immunosuppressants such as azathioprine; complete remission is infrequent and long-term immunosuppression is usually required.

According to a company news release, a randomized, double-blind, placebo-controlled global phase 3 study is currently being conducted to evaluate the efficacy and safety of mycophenolate for maintaining or improving symptom control with reduced doses of corticosteroids in patients with MG for 36 weeks.

Primary end points of the trial include both minimal disease activity and low steroid dose. Results are anticipated for late 2006.

Mycophenolate is approved by the FDA and other regulatory authorities worldwide for use in conjunction with cyclosporine and corticosteroids for the prophylaxis of organ rejection in adult patients receiving allogenic renal, cardiac, or hepatic transplant. In some countries, it is also approved for use in pediatric kidney transplantation.


Orphan Drug Adult Stem Cell Product (Prochymal) for GVHD

On December 20, 2005, the FDA approved orphan drug status for an adult stem cell product (Prochymal, made by Osiris Therapeutics, Inc) in the treatment of acute graft-versus-host disease (GVHD). The product was previously granted fast-track status in January 2005.

GVHD is a potentially fatal form of immune rejection that affects approximately 50% of patients who receive an allogenic hematopoietic stem cell transplant for the treatment of cancers such as leukemia and lymphoma. In many cases, acute GVHD is refractory to steroids and immunosuppressive agents that are the current standard of care.

According to a company news release, the product is a formulation of human mesenchymal stem cells that modulates the inflammatory response via 2 mechanisms: decreasing the production of pro-inflammatory cytokines while increasing levels of anti-inflammatory cytokines; and reducing T-cell proliferation rates.

In addition, the stem cells have demonstrated an ability to migrate to sites of inflammation and tissue damage, where they facilitate the repair process. In patients with GVHD, use of the product has reduced diarrhea, improved ulcerations in the intestinal lining, and healed skin lesions.

The company is currently enrolling patients in 2 ongoing phase 2, placebo-controlled clinical trials designed to evaluate product efficacy at 2 dose levels in patients with acute and severe acute GVHD receiving standard steroid therapy.

The product is also being studied for use in other immunologic disease applications such as Crohn's disease.


Orphan Drugs Shiga Toxin Antibodies for STEC Infections

The FDA approved in December 2005 orphan drug status for 2 chimeric anti-Shiga toxin antibodies (caStx1 and caStx2, made by Caprion Pharmaceuticals, Inc) in the treatment of Shiga toxin-producing Escherichia coli (STEC) infections.

According to a company news release, there is no known treatment for the disease, which is transmitted via contaminated food or water and affects more than 100,000 individuals annually in the United States.

The antibodies are intended to neutralize circulating Shiga toxins (Stx1 and Stx2), thereby treating the disease and preventing serious complications such as gastrointestinal disease, bloody diarrhea, destruction of red blood cells and platelets, and hemolytic uremic syndrome (HUS).

The product is currently being evaluated for preventing HUS in a dose-escalating, phase 1 US clinical trial of STEC-infected pediatric patients. It was also recently designated as an orphan drug for this indication by the European Medicines Evaluation Agency.

Reviewed by Gary D. Vogin, MD

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