* FDA denies approval of Horizant extended-release tablets
* Concerned about pancreatic tumours in rats
* Glaxo shares flat in early trade
(Adds analyst comment, sales forecast, Glaxo shares)
LONDON/NEW YORK, Feb 18 U.S. regulators have
denied approval for a drug from XenoPort XNPT.O and
GlaxoSmithKline (GSK.L) to treat restless legs syndrome because
of a potential link to cancer found in rats.
The companies said they received a complete response letter
from the Food and Drug Administration (FDA) regarding Horizant
extended-release tablets, stating that the drug could not be
approved at this time.
The agency said a preclinical finding of pancreatic acinar
cell tumours in rats was of sufficient concern to preclude a
XenoPort and Glaxo said in a statement they were assessing
the appropriate next steps and would be communicating with the
FDA. The application was originally submitted to the FDA on Jan.
A verdict on the medicine had been delayed before, while FDA
officials sought information on a risk evaluation programme, and
analysts said the latest decision was a setback for both
"The FDA's response must raise questions over the future for
this product, without further significant work being carried out
to clarify the risk in humans," analysts at Jefferies said in a
The brokerage has been expecting peak sales for the drug of
$500 million a year, making it a relatively minor driver for
Glaxo at less than 1 percent of forecast group revenue in 2014.
Glaxo shares were flat in early trading on Thursday.
The uncertainty over Horizant is more significant for
Glaxo's smaller partner Xenoport, which is to hold a conference
call on the issue later in the day.
Horizant, which was previously known as Solzira, is a
long-lasting version of gabapentin, which is approved for
The FDA acknowledged that similar findings were known for
gabapentin at the time of its approval but said the seriousness
of that condition justified the potential risks.
Restless legs syndrome, however, is a less serious and
non-life threatening condition for which other treatments are
available. It is characterised by an irresistible urge to move
the limbs due to unpleasant sensations.
(Reporting by Ben Hirschler and Michael Erman; Editing by Gary
Hill and Sharon Lindores)