By Peter Loftus 
 

Shares of Vivus Inc. (VVUS) fell 11% Thursday after a stock-research website raised questions about prospects for the drug maker's newly approved weight-loss drug Qsymia.

Citron Research, which holds positions in some of the stocks it covers, including short positions, published an article saying Vivus may not have sufficient patent protection for Qsymia. Citron predicted the drug will have zero revenue a year from now.

Vivus didn't immediately respond to the bearish note. On Wednesday, an executive told analysts on a conference call that the company has "very strong patents" for the drug in the U.S. and Europe that run through 2020.

The U.S. Food and Drug Administration approved Qsymia on Tuesday, the second approval of a new weight-loss drug in less than a month, after FDA's clearance of Arena Pharmaceuticals Inc.'s (ARNA) Belviq.

Following the regulatory victory, Vivus shares surged 10% Wednesday on hopes that the drug will live up to some analysts' estimates that annual sales will exceed $1 billion. But the stock gave back those gains Thursday as Citron's article raised questions about whether the drug would generate any meaningful revenue.

Qsymia is a single-pill combination of two older drugs: phentermine and topiramate extended release, each of which is available separately as low-priced generic drug. Topiramate has been sold by Johnson & Johnson (JNJ) as Topamax to treat seizures in people with epilepsy. Topamax lost its primary patent protection in 2009 and is now available in generic form.

Citron's article said J&J also has a patent covering topiramate's use to treat obesity, which runs through 2017. Vivus has previously acknowledged in a regulatory filing that it was aware of issued patents for the use of topiramate alone or in combination with other agents to treat obesity. But Vivus said it has worked with patent attorneys to build a "strong patent portfolio" in an attempt to gain exclusivity over the life of the patents.

A J&J spokesman declined immediate comment.

Citron also raised questions about the validity of one of the patents Vivus licensed from a researcher to cover Qsymia.

Citron said in its report that because Qsymia is a combination of two separately available drugs, it's possible that doctors would choose to prescribe those older drugs to patients, rather than prescribe Qsymia.

The Citron note also questions why Vivus hasn't formed a partnership or transaction with a large drug maker to help market Qsymia.

Vivus executives said Wednesday they plan to launch the drug in the fourth quarter.

Some analysts have been more bullish on Vivus and Qsymia than Citron. In a note Thursday, Credit Suisse estimated peak annual sales for Qsymia would hit $1.3 billion in the U.S. and $1.9 billion worldwide.

Vivus shares closed down $3.23 at $25.77 Thursday.

Write to Peter Loftus at peter.loftus@dowjones.com

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