An epilepsy tablet made by Marlborough-based Sunovion Pharmaceuticals Inc. won US approval Friday to be sold as a primary therapy for hundreds of thousands of Americans suffering from partial-onset seizures.
The drug, called Aptiom, has been on the market since 2013, but its approved use has been restricted to patients who have not responded to one or two previous anticonvulsive treatments. The Sunovion drug is now taken in addition to one or more other medicines.
Food and Drug Administration officials Friday gave their blessing for Aptiom to be used as a so-called monotherapy, meaning it can be prescribed by itself to be taken once a day for new patients or those whose medications have failed to reduce the frequency of their seizures.
“This will make Aptiom a reasonable first choice, particularly for those patients who are already taking Aptiom as an adjunct therapy where it has demonstrated improved seizure control,” Antony Loebel, executive vice president and chief medical officer at Sunovion, said in an interview. “We expect this approval to have a significant impact on the overall use of Aptiom.”
That will open a much larger market for Sunovion, which is owned by Japan’s giant Sumitomo Dainippon Pharma Group. Sunovion has about 1,500 employees worldwide, about a third of them in Marlborough. It was formerly called Sepracor, which was acquired by Sumitomo Dainippon for $2.6 billion in 2009.
Sunovion declined to disclose how much it would charge for Aptiom. A spokeswoman said the price would depend on the dosage, which will vary widely and be prescribed for individual epilepsy patients by their doctors.
In two clinical trials, Sunovion said Aptiom has been well tolerated by patients and proved effective in reducing the frequency of seizures. About 8 percent of patients in the trials showed an absence of seizures while taking Aptiom, the company said.
About three-quarters of the more than 500,000 patients in the United States who suffer partial-onset seizures — where the seizure starts in one part of the brain and spreads to others — take one of more than a dozen therapies. But more than a third don’t respond to the first or second drug they take.
Two of the largest antiseizure monotherapies now on the market are Keppra and Vimpat, both made by Belgium’s UCB Pharma.
“The medications are getting safer and better tolerated, but some 30 percent of epilepsy patients don’t have seizure control,” said Dr. John Stern, a neurologist at the University of California in Los Angeles Medical Center who specializes in epilepsy and seizures and who has consulted for Sunovion on educational programs.
Stern said, “There’s no one medication that’s the superior choice in terms of seizures. It all depends on the patient’s needs.”
Aptiom, which Sunovion originally licensed from Portuguese drug maker Bial, is one of several drugs in a class of antiseizure agents called sodium channel blockers. They work by stabilizing neurons in the brain, causing a reduction in seizures.
Epilepsy is a brain disorder caused by abnormal activity in the brain’s nerve cells. About 200,000 new cases occur in the United States every year, according to the FDA. More than half are partial-onset seizures while the rest are general seizures that affect the entirety of the brain all at once.
The market for drugs that treat epilepsy has been estimated at about $2.5 billion annually. Drugs treating partial seizures represent about 60 percent of that market.
Sunovion has nine drugs on the market, treating respiratory conditions and central nervous system disorders.