Vivus, the Silicon Valley biotech firm marketing the anti-obesity drug Qsymia, is working with outside PR and IR counsel as a large shareholder says it will mount a proxy fight at the company's annual meeting.

QsymiaQsymia, one of the first prescription obesity drugs on the market since the 1990s, is limited by the FDA per its 2012 approval to certified mail-order pharmacy sales, but Vivus has pushed for its inclusion in the retail pharmacy market.

First Manhattan Company, a New York hedge fund that owns more than 9% of Vivus, said April 10 that an expected announcement allowing expanded sales would be a "step forward" but not enough for the drug's success. FMC, which has engaged Abernathy MacGregor Group, said it will nominate six directors for the Vivus board who are independent of management. The shareholder wants the company to find a partnership for a new commercial strategy for Qsymia.

Vivus, working with Joele Frank, Wilkinson Brimmer Katcher and IR firm The Trout Group, back in March acknowledged FMC's planned slate and said it hired proxy solicitor Morrow & Co. among other advisors.

GolinHarris handles PR for Qsymia.

Vivus shares are trading around $11.21, toward the lower end of its $9.86-$31.21 52-week range.