GlaxoSmithKline Plc and Valeant Pharmaceuticals International may have to wait an extra three months for a review of their experimental epilepsy medicine after U.S. regulators sought more time to study data.
The Food and Drug Administration pushed back the targeted date under the Prescription Drug User Fee Act to review ezogabine to Nov. 30 from Aug. 30, the companies said in a statement. Under that law, drug companies pay certain fees to help speed up the agency’s review process.
The decision may stall the availability of a treatment for the one-third of epilepsy patients who aren’t helped by current therapies. More than 2 million people in the U.S. have been diagnosed with epilepsy or have suffered from an unprovoked seizure, according to the National Institute of Neurological Disorders and Stroke.
A proposal to evaluate and mitigate risks of the drug, requested by the FDA, was submitted Aug. 26, Glaxo and Valeant said in the statement dated yesterday.
London-based Glaxo and Valeant, of Aliso Viejo, California, estimate that 30 percent of patients have trouble controlling their seizures with epilepsy medicines, leading to disability and an unsatisfactory quality of life.
Glaxo, the U.K.’s biggest drugmaker, bought global marketing rights to the medicine from Valeant in 2008 and plans to sell it under the name Potiga. Valeant will share as much as half of U.S. revenue. Meda AB, of Solna, Sweden, discovered the drug and is entitled to royalties.
Ezogabine may bring in more than $600 million in annual sales, according to analysts surveyed by Bloomberg. Glaxo’s sales of the drug, called retigabine outside the U.S., may be 340.5 million pounds ($526 million) in 2014, according to the average estimate of two analysts surveyed by Bloomberg. Two analysts projected the product will bring in $117.9 million in revenue for Valeant that same year.
The treatment acts on the brain’s potassium channel, controlling nerve cells so they don’t become over-stimulated and cause a seizure. Most current drugs regulate sodium or calcium channels.
An FDA advisory panel concluded at an Aug. 11 meeting that ezogabine worked as an add-on treatment and that bladder blockage, a side effect seen in studies, can be controlled by monitoring patients.
The treatment was linked in studies to cases of urinary retention, an inability to empty the bladder, which may cause infections or permanent bladder and kidney damage. While most cases were reversible, FDA staff called it a “significant safety issue” in a report released before the panel meeting.
Glaxo shares fell 4.5 pence, or less than 1 percent, to close at 1,221 pence as of 4:35 p.m. in London trading.