Delays at GlaxoSmithKline’s (GSK) contract manufacturer have caused a shortage in the US of restless legs syndrome treatment Horizant, according to the FDA.
In its notice, the US regulator said GSK is “experiencing a backorder situation”, leaving an expected shortage of Horizant (gabapentin enacarbil) until June 2013 – one month after XenoPort assumes responsibility for manufacturing and commercialization of the medicine as part of an agreement with GSK.
It is the latest in a long line of problems for Horizant, which was developed by GSK and XenoPort and approved by the FDA for neurological disorder restless legs syndrome in April 2011 after a two year struggle to gain approval.
This saw a Complete Response Letter, declining to grant the drug marketing approval, issued in February 2010.
But even after its approval, sales did not match expectations, and XenoPort attempted to terminate its agreement with GSK on the grounds of a breach of contract, causing GSK to launch a lawsuit in response.
Then in November 2012, GSK and XenoPort agreed to end their collaboration, with all rights returned to Horizant’s inventors XenoPort.
In its response to the latest problems in manufacturing, XenoPort’s CEO Dr Ronald Barrett said that company was “obviously disappointed by this news, particularly since we have received inquiries from patients who have been unable to get their Horizant prescriptions filled”.
“We are working with GSK and its contract manufacturer to expedite the next Horizant manufacturing campaign, and we are also advancing our plans to work directly with the contract manufacturer as soon as possible,” he added.
There is the possibility that the current shortage for GSK will have a knock-on effect for XenoPort, as GSK is due to continue to supply Horizant until October 30, 2013, as part of the agreement.
According to XenoPort, it is completing preparations to assume all other responsibilities for marketing the drug, including deploying a contract sales force, although it anticipates that full commercial introduction of Horizant will not happen until there is a sufficient supply.