NEW YORK (Reuters) - Roche Holding AG <ROG.VX> is not raising financing to acquire BioMarin Pharmaceuticals <BMRN.O>, a Roche spokesman told Reuters Thursday, contradicting a report that had lifted BioMarin shares almost 10 percent in pre-market trading.

Shares of BioMarin gave back most of those gains and was up 1.2 percent after Roche knocked down the report from DealReporter that said the big drugmaker was lining up $15 billion in debt financing for an acquisition of the Novato, California-based company.

After the shares surged on that report, Bloomberg reported that Roche Chief Executive Officer Severin Schwan said the drugmaker was not raising financing in preparation for a bid for BioMarin. A Roche spokesman confirmed to Reuters that the Swiss group was not lining up financing for a deal.

Its shares gave up most of those gains and were up 1.6 percent in late morning trading and was trading at $78.75.

In July, Roche Holding AG was seeking financing for a potential bid for Alexion Pharmaceuticals Inc <ALXN.O>, another drugmaker that treats rare diseases, sources told Reuters at the time.

But Roche's head of pharmaceuticals told Reuters in an interview last week that treating ultra-rare diseases was a distinct business from Roche's current area of expertise, comments that may cast doubts on its interest in the field.

(Reporting by Jessica Toonkel; Editing by Marguerita Choy and David Gregorio)