SEATTLE, May 31, 2013 /PRNewswire/ -- Omeros Corporation (NASDAQ: OMER) today announced positive results from its Phase 1 clinical program evaluating OMS824, the lead compound from its phosphodiesterase 10 (PDE10) program. This study measured the extent to which OMS824 binds to PDE10 in the basal ganglia, a region of the brain that has been linked to a wide range of diseases that affect cognition. The results show that the selected dose of OMS824 achieved approximately 50 percent occupancy of PDE10 without triggering the extrapyramidal symptoms (loss of muscle control, e.g., muscle rigidity, tremors, or involuntary muscle movements) reported as side effects with other PDE10 inhibitors that achieved similar or significantly lower occupancy levels. OMS824 is Omeros' proprietary compound that selectively inhibits PDE10, and the Company plans to advance into Phase 2 clinical trials in Huntington's disease and schizophrenia later this year. The OMS824 Phase 1 clinical program previously evaluated the tolerability and pharmacokinetics of single and multiple doses of OMS824 in healthy subjects. OMS824 was well tolerated by all subjects, and the only apparent drug-related adverse event was mild somnolence at the highest dose evaluated. In the clinical trial reported today, positron emission tomography (PET) scans were used to measure the binding activity of OMS824 to PDE10 in the brains of healthy subjects who received once daily dosing of OMS824 for seven days. Quantitation of PET images showed that approximately 50 percent occupancy of PDE10 in the basal ganglia was achieved by this dosing regimen. OMS824 was well tolerated and, consistent with earlier studies, mild somnolence was the only apparent adverse effect. Other PDE10 inhibitors under development have been associated with extrapyramidal symptoms in humans at similar or substantially lower PDE10 occupancy levels than that observed with OMS824. In contrast, these adverse side effects have not been seen at any of the OMS824 dose levels studied to date. This difference suggests that OMS824 has a better clinical therapeutic index or "safety factor" than other PDE10 inhibitors in development. Omeros plans to measure OMS824's binding to PDE10 in additional dose cohorts.