Omeros Suspends PDE10 Inhibitor Trial Due To High Free-Plasma Concentrations

Omeros Corporation has suspended its trial of OMS824, a phosphodiesterase 10 (PDE10) inhibitor being evaluated for treatment of Huntington's disease. Omeros provided the update in a press release, stating that a nonclinical study in rats showed high free-plasma concentrations — higher than those observed in non-human primates or humans. The company suspended the human clinical trial after submitting the results from the rat study to the Food and Drug Administration (FDA), which requested that Omeros evaluate the rat study and nonclinical studies before restarting the clinical trial.

Gregory A. Demopulos, M.D., chairman and CEO of Omeros, said, "Based on currently available data, we do not believe that the observation in the rats is caused by OMS824. We will work with the FDA and look forward to continuing the Phase 2 Huntington's trial."

OMS824

OMS824 is a selective PDE10 inhibitor. Phosphodiesterase 10 is an enzyme expressed in brain regions associated with cognition. In Huntington’s disease, a hereditary neurodegenerative disorder, cognitive and psychomotor dysfunction leads to movement, cognition, behavioral abnormalities, and premature death. Current medications do not meaningfully improve the disease. Omeros' OMS824 inhibits PDE10, thereby improving motor and psychiatric abnormalities. Omeros is also studying the compound for treatment of schizophrenia symptoms. The FDA has awarded Orphan Drug and Fast Track designation to OMS824 in Huntington's disease.

OMS824 Rat Study

Omeros started a Phase 2 trial of OMS824 in Huntington’s in February 2014. The company also conducted a 13-week study in rats. Investigators noticed that several rats who received the maximum dose showed high drug concentrations in the blood, a finding not noticed in other studies. Omeros reported the findings to the FDA's Division of Neurology Products and its Division of Psychiatry Products, who requested that Omeros characterize the results more fully prior to reinitiating the clinical trial.

About Omeros

While the trial suspension is a setback for the Seattle-based company, it has had some recent success to balance its woes. In June 2014, the FDA approved Omidria (phenylephrine and ketorolac injection), a pupil-dilating agent used in cataract surgery or intraocular lens replacement (ILR). The FDA did not ask for post-marketing studies other than a pediatric study. The company is also working on treatments for complement-related thrombotic microangiopathies, addictive and compulsive disorders, and surgical procedure complications.