By Zeba Siddiqui
April 10 (Reuters) - An expected revision of Vivus Inc's risk management plan for its obesity drug Qsymia is unlikely to guarantee the drug's success, the company's top shareholder said.
Vivus shares rose 3 percent to $11.17 on Wednesday, adding to Tuesday's gains on speculation that U.S. health regulators would revise the drug's risk plan.
The company has blamed the slow uptake of the diet drug on its current Risk Evaluation and Mitigation Strategy (REMS) that allows the drug to be sold only through mail-order pharmacies due to its potential for causing birth defects.
The proposed revision would also allow sale of the drug, the first diet pill to hit the U.S. market in more than a decade, through retail pharmacies.
"(The REMS modification) is necessary but not sufficient for Qsymia's success," said Vivus shareholder First Manhattan Company (FMC), which last month said it planned to nominate six directors to Vivus' board at the company's 2013 annual meeting.
A Vivus spokesman declined to comment on FMC's statement.
FMC, which owns about 9.1 percent Vivus stock, has argued that the Vivus board needs to be more independent and have greater experience in guiding a company with a potential blockbuster drug.
Dan Szemis of Chilton Investment Co, another top Vivus shareholder, said FMC's push for a change appeared hasty as the drug's potential was yet to be demonstrated, given that it has been on the market for only about six months.
Vivus's measured marketing approach has been backed by some industry analysts, since safety issues seen in previous obesity pills have made physicians and consumers wary of such drugs.
On Wednesday, FMC agreed that an expected REMS modification would be "a step forward", but said achieving the drug's full potential would require a new commercial strategy, including finding a partner to help market Qsymia.
However, Szemis said he "did not see why investors would want the company to negotiate from a position of weakness."
"Six to nine months from now we should be in a better position to gauge the potential for the drug and management's execution. I'm willing to give management more time to execute their plan."
By then, Vivus should have broader pharmacy distribution, better reimbursement, a more knowledgeable prescriber base and higher patient demand, Szemis added.
Chilton held about 2.6 percent of Vivus stock at the end of 2012, making it the company's ninth biggest shareholder, according to the investor's most recent regulatory filing.