SEATTLE, March 6, 2014 /PRNewswire/ -- Omeros Corporation (NASDAQ: OMER) today announced additional positive results from a Phase 2a clinical trial of OMS824, the company's phosphodiesterase 10 (PDE10) inhibitor. Patients with schizophrenia were administered a higher dose than had been evaluated in any OMS824 trial, which resulted in approximately 50 percent higher plasma concentrations than did the previously reported highest dose and had a similar side-effect profile to those of the lower doses. OMS824 selectively inhibits PDE10, an enzyme expressed in areas of the brain linked to a wide range of diseases that affect cognition, including schizophrenia and Huntington's disease. The results reported today were in psychiatrically stable patients who continued their usual antipsychotic regimen and received OMS824 or placebo for 14 days. Despite achieving approximately 50 percent higher plasma concentrations of OMS824 than previously reached at the next-highest dose in the Phase 2a trial, OMS824 was tolerated with mild or moderate adverse events that were consistent with those seen in previous cohorts, were self-limited and did not result in any discontinuation of the drug. The drug concentrations in these schizophrenia patients were also approximately 50 percent higher than levels that corresponded to an average of 66 percent target interaction (a high of approximately 70 percent) at PDE10 in a Phase 1 positron emission tomography (PET) trial in healthy subjects. To date, the OMS824 PET trial has demonstrated significantly higher target interaction at PDE10 without extrapyramidal symptoms (loss of muscle control, e.g., muscle rigidity, tremors, or involuntary muscle movements) than has been reported for any other PDE10 inhibitor in development. An additional PET trial cohort is planned in the coming weeks. The positive results across all doses tested in this Phase 2a trial indicate that OMS824 can be administered in combination with standard antipsychotic medications and that, at tolerated doses, yields plasma concentrations that are predicted to achieve a high degree of PDE10 target interaction in the striatum. Future Phase 2 and Phase 3 clinical trials in Omeros' schizophrenia program may evaluate OMS824 both as a single agent and as adjunctive treatment for cognitive impairment, acute exacerbation of symptoms, and/or inadequate response to antipsychotic medications.