GlaxoSmithKline (GSK) has ended its collaboration with XenoPort to commercialise the restless legs syndrome drug Horizant in the US.
The two companies reached an agreement that will see GSK return US rights to Horizant (gabapentin enacarbil) back to its developer XenoPort five years after the two companies signed a $640m deal for the drug.
Since then, Horizant has experienced a tricky time gaining approval in the US, with GSK and XenoPort receiving a complete response letter from the Food and Drug Administration (FDA) in 2010 following preclinical findings of pancreatic acinar cell tumours in rats that had been given the drug.
Horizant was eventually approved for the treatment of moderate-to-severe restless legs syndrome in April, 2011, after these concerns were resolved.
There have been continued problems since, however, with friction between XenoPort and GSK after uptake of the drug proved to be disappointing – the biotech reported that Horizant’s US sales in the first quarter of 2012 were just $1.3m.
XenoPort laid much of the blame on GSK, and sought to terminate the agreement in June, 2012, on the grounds of a breach of contract, although GSK responded with a lawsuit insisting it was meeting its commitments.
It now seems the two have found common ground regarding the termination of the collaboration and all outstanding litigation has been resolved.
“XenoPort acknowledges that GSK fulfilled its contractual obligations on the development, manufacturing and commercialisation of Horizant,” said GSK in a statement.
There will be a transition period up to April 30, 2013, during which GSK will continue to exclusively commercialise, promote, manufacture and distribute Horizant in the US. XenoPort will not receive any revenue or incur any losses from these sales.
GSK has written off £103m for the third quarter of 2012 due to the cancellation of the deal, although no further one-off charges related to Horizant are expected.