Omeros halts a Phase II Huntington's trial over alarming rat results

Following the FDA's advice, Omeros ($OMER) has hit the brakes on a mid-stage human trial of its Huntington's disease treatment in light of data from a separate animal study, news that tanked the biotech's share value.

The drug, OMS824, works by blocking an enzyme called phosphodiesterase 10, thereby relieving symptoms of cognitive and psychomotor disorders. Earlier this year, Omeros kicked off a Phase II, dose-escalating trial of the treatment in Huntington's patients, concurrently conducting a nonclinical study on rats to evaluate how the drug might perform in longer trials.

Looking at 13-week data from the rat study, Omeros noted that the animals receiving the highest doses had blood concentrations of OMS824 considerably higher than anything seen in any human trial, the company said. Omeros informed the FDA of its discovery, and, in light of the agency's response, the biotech has suspended its Phase II study while it further evaluates the rat data.

The setback sent Omeros' shares down as much as 17% on Tuesday morning, stirring fears about OMS824's long-term safety prospects.

But Omeros is preaching patience, pointing out that the maximum dose given to rats is higher than any amount of OMS824 ever administered to a human, and the drug has been well-tolerated among the more than 120 people who have received it, the company said. Furthermore, in a separate preclinical study, primates received the same high dose as the rats in question and didn't experience the same alarming concentrations, Omeros said.

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

Meanwhile, the biotech is still riding high off of its first FDA approval, as Omidria, a treatment used during cataract surgery, picked up the agency's blessing in June. Earlier this month, Omeros struck a deal with Hospira ($HSP) to supply the drug for its U.S. rollout and eventual European launch.

- read the release

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