Amarin shares slide as investors fret over fate of AMR101 patent

Shares of Amarin ($AMRN) got roughed up yesterday after investors caught wind of the news that patent officials had issued a "final rejection" notice for a key filing on the biotech's experimental heart drug AMR101. The patent buzz was quickly picked up by analysts who speculated on the possible impact of the rejection, zeroing in on the potential for a shortened existence as a branded drug and potentially slicing billions of dollars from expected Amarin revenue.

Amarin is widely expected to file for an approval on AMR101--prescription strength fish oil--in the fall, which would raise the possibility of a 2012 launch for the blockbuster hopeful, provided regulators don't upset the apple cart along the way. But with peak sales estimated at $2 billion, the analysts have been paying close attention to the fate of the developer's method of treatment patent, which could extend the life of the brand by protecting the use of the active ingredient in the drug for high levels of triglycerides.

Amarin's shares slid as much as 10% as investors fretted over the patent prospects. But not all the analysts were biting. In a note sent out this morning Avik Roy expressed his own opinion that these method-of-use patents aren't much help at holding generic competition at bay in any case. Roy also noted that in a meeting with Amarin's Joe Zakrzewski, the CEO "said that the company had about a year to decide whether or not to sign a partnership for AMR101, suggesting that no deal was imminent. We continue to believe that partners will need to gain more confidence in AMR101's IP situation before paying up for the drug."

On a not-so-final note, a final rejection notice from the patent office isn't final. They can be appealed, leaving analysts and investors plenty more to chew on in the future.

- here's the Dow Jones report

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