MEI Pharma, a San Diego-based oncology company focused on the clinical development of novel therapies for cancer, has announced that the FDA has granted orphan drug designation to the company's investigational drug Pracinostat for the treatment of acute myeloid leukemia (AML).

The FDA's Orphan Drug Designation program provides orphan status to drugs defined as those intended for the safe and effective treatment, diagnosis or prevention of rare diseases that affect fewer than 200,000 people in the U.S. Orphan designation qualifies the sponsor of the drug for certain development incentives, including tax credits for qualified clinical testing, prescription drug user fee exemptions and seven-year marketing exclusivity upon FDA approval.

Pracinostat is an orally available histone deacetylase (HDAC) inhibitor that has been tested in a number of phase I and phase II clinical trials in advanced hematologic disorders and solid tumor indications in both adult and pediatric patients. Pracinostat has been generally well-tolerated in more than 200 patients to date, with readily manageable side effects that are often associated with drugs of this class, such as fatigue. In a phase I dose-escalation trial, Pracinostat demonstrated evidence of single-agent activity in elderly AML patients, including two out of 14 (14%) who achieved a complete remission (CR), with durable responses persisting 206+ and 362 days, respectively. MEI Pharma currently is conducting a phase II clinical trial of Pracinostat in combination with Vidaza in elderly patients with newly diagnosed AML. Preliminary data from the open-label trial is anticipated by Dec. 2014.

MEI Pharma owns exclusive worldwide rights to Pracinostat.