* Says receives FDA "refusal to file" letter for Rhucin
* Partner companies say plan to meet FDA as soon as possible
* $5 mln payment delayed but no acute funding issue
* Pharming shares plunge 22 pct at opening
(Recasts, adds comment on funding)
By Sara Webb
AMSTERDAM, Feb 28 (Reuters) - Dutch biotech firm Pharming (PHAR.AS) faced a setback in obtaining approval for its first product, a drug derived from rabbit milk, in the United States, which will result in funding delays.
Pharming shares plunged 22 percent at the start of trading after the biotech firm and its partner Santarus SNTS.O said they had received a "refusal to file" letter from the U.S. Food and Drug Administration (FDA) for Rhucin.
Without the FDA approval, Pharming faces a delay of a year or more in receiving a milestone payment of $5 million from Santarus, which Pharming had expected to receive in the first quarter of 2011.
"That is a setback but not a disaster," Rienk Pijpstra, chief medical officer of Pharming, told Reuters.
"There is no acute issue with regards to funding. Other milestone (payments) may not be affected."
Pijpstra said that he expects a new application to the FDA in early or mid-2012, and approval in 2013.
Pharming's first product is marketed as Ruconest in Europe and as Rhucin in the United States where it has been waiting for regulatory approval. The drug treats a rare and dangerous inflammation illness called hereditary angioedema (HAE). [ID:nLDE6BJ1OA]
Pharming and Santarus, which has licenced certain exclusive rights from Pharming to commercialise Rhucin in North America, said on Monday that the FDA had indicated that Pharming's biologics licence application, or BLA, was "not sufficiently complete to enable a critical medical review".
The two companies said in a joint statement that they "intend to meet with the FDA at the earliest opportunity to discuss the issues raised in the FDA letter and to reach a more comprehensive understanding of what would be required for the BLA to be accepted for review."
Pharming has struggled financially in recent years in the face of regulatory setbacks.
In a recent interview with Reuters, Pharming said it had enough cash to fund operations until 2012. [ID:nLDE6BJ1N4] (Reporting by Sara Webb; Editing by Jon Loades-Carter)