Omeros Corporation, a clinical-stage biopharmaceutical company, has reported additional positive data from its phase I programme for OMS824, the lead compound in its phosphodiesterase 10 (PDE10) programme. This clinical trial evaluated the extent to which OMS824 binds to PDE10, an enzyme expressed in the region of the brain that has been linked to a wide range of diseases that affect cognition.

In the latest cohort enrolled in this trial, OMS824 achieved a high of approximately 70 per cent engagement at PDE10 without evidence of extrapyramidal symptoms (EPS). These data further support the potential of OMS824 to have a high therapeutic index in the treatment of patients with schizophrenia, Huntington's disease and other cognitive disorders. Omeros is completing a phase IIa trial evaluating the drug in patients with schizophrenia and will start enrollment in a phase II trial for Huntington's disease this quarter.

The results reported were in healthy male subjects receiving OMS824 once daily for 10 days. Positron emission tomography (PET) scans were used to measure the binding activity of OMS824 to PDE10 in the brain on the last day of dosing. An average of 66 per cent occupancy at PDE10 was seen in the striatum, the region of the brain that plays a critical role in cognition. The drug was well tolerated in all subjects with mild somnolence as the main side effect. Since the maximally tolerated dose has not been reached, Omeros is now planning to evaluate a higher dose of OMS824 in the trial to determine whether an even higher level of PDE10 occupancy can be achieved.

Effective inhibition of PDE10 is considered a novel and promising mechanism to treat central nervous system disorders. Intolerable side effects, particularly EPS, are an important limitation to PDE10 inhibitors currently in development, narrowing the therapeutic index (the ratio of the toxic dose to the effective dose) and likely prohibiting the evaluation of these compounds at higher levels of target engagement. The results in the current cohort along with previously reported data from this clinical trial indicate that OMS824 may not be similarly constrained by such side effects.

"OMS824 continues to allow increased dosing that is well tolerated and delivers a significantly higher level of interaction at the target enzyme than has been reported for any other PDE10 inhibitor," stated Gregory A Demopulos, MD, chairman and chief executive officer of Omeros. "Given the absence to date of limiting side effects in any of the healthy subjects or schizophrenia patients administered OMS824, we plan to evaluate a higher dose in both the phase IIa schizophrenia and the phase I PET trials. In parallel, we will soon initiate enrollment in our OMS824 phase II clinical trial in Huntington's disease."

Omeros was recently awarded Orphan Drug and Fast Track Designations for the OMS824 programme in Huntington's disease by the US Food and Drug Administration.

PDE10 is an enzyme that is expressed in areas of the brain linked to diseases that affect cognition and psychomotor functions, including Huntington's disease and schizophrenia.

Omeros is committed to discovering, developing and commercializing small-molecule and protein therapeutics targeting inflammation, coagulopathies and disorders of the central nervous system.