Seattle Genetics, Inc. announced that the US Food and Drug Administration (FDA) has granted orphan drug designation to SGN-33 for the treatment of acute myeloid leukaemia (AML) and to SGN-35 for the treatment of Hodgkin's disease.

"SGN-33 and SGN-35 both target diseases with significant unmet medical needs and represent opportunities for well-tolerated biologics that provide improved treatment options for patients," said Clay B. Siegall, Ph.D., president and chief executive officer of Seattle Genetics. "We are aggressively pursuing the development of SGN-33, and expect to advance into two combination clinical trials during 2007, including a phase II study in combination with low dose chemotherapy for older patients with AML. With SGN-35, we are conducting an ongoing phase I dose-escalation study with plans to report data at the ASH annual meeting in December 2007. Orphan drug designation provides several benefits to the company, including market exclusivity for seven years, and is an important part of our overall development strategy for these novel drugs."

SGN-33, or lintuzumab, is a humanized monoclonal antibody that targets the CD33 antigen that is currently in a phase I clinical trial for the treatment of AML and myelodysplastic syndromes (MDS). Preliminary data from the ongoing phase I study have shown that SGN-33 is well-tolerated and has antitumour activity, including improved blood counts, decreased transfusion requirements and decreased myeloblasts in multiple patients with AML or MDS. AML is the most common type of adult leukaemia, with an estimated 13,000 new cases diagnosed each year in the United States according to the National Cancer Institute. More than 80 percent of elderly AML patients die within a year of diagnosis.

SGN-35 is an antibody-drug conjugate (ADC) that links an anti-CD30 monoclonal antibody to a potent, synthetic drug payload, monomethyl auristatin E (MMAE). SGN-35 is currently being evaluated in a phase I clinical trial for Hodgkin's disease and other CD30-positive haematologic malignancies. In preclinical studies, SGN-35 has demonstrated potent antitumour activity at well-tolerated doses. Of the more than 500,000 people in the United States with lymphoma, approximately 134,000 have Hodgkin's disease. The National Cancer Institute estimates that there will be more than 8,000 new cases of Hodgkin's disease diagnosed in the United States during 2007.

Orphan drug designation provides Seattle Genetics with seven years of marketing exclusivity upon market approval, as well as the opportunity to obtain grant funding from the U.S. government to defray costs of clinical trial expenses, tax credits for clinical research expenses and potential waiver of the FDA's application user fee. The Orphan Drug Act is intended to encourage companies to develop therapies for the treatment of diseases that affect fewer than 200,000 individuals in the United States.