Vivus Inc.’s biggest shareholder said Tuesday that it plans to replace the company’s CEO if it is successful in gaining control of the obesity drug maker in an ongoing proxy fight.

First Manhattan Co., which holds about a 10-percent stake in Vivus, said it will name Anthony Zook as CEO if it wins control of the board. Zook was president of MedImmune Inc. before MedImmune was acquired by AstraZeneca, and he was head of global commercial operations for AstraZeneca PLC until February.

Leland Wilson, 69, has been CEO and a director of Vivus since 1991. The Mountain View, Calif., company declined to comment on First Manhattan’s proposal.

In March First Manhattan moved to replace Vivus’ entire board of directors by nominating six candidates. It said the launch of Vivus’ weight loss drug Qsymia has been unsuccessful and that the company should change its U.S. business strategy and get Qsymia approved in Europe. The firm, which owns a 9.9-percent stake in Vivus, added that the company needs new leadership.

Vivus has urged shareholders to reject First Manhattan’s nominees and said its board has the experience necessary to make Qsymia a success. The company’s annual shareholder meeting is scheduled for July 15.

The Food and Drug Administration approved Qsymia in July, and Vivus started selling it in September. So far sales have not lived up to Wall Street’s lofty expectations. Insurance coverage for Qsymia remains limited and out-of-pocket costs for patients are high. At first Qsymia was only available through mail order, which also limited sales. On Monday Vivus said the drug is now available at about 8,000 Walgreen Co. and Costco Wholesale Corp. pharmacies.

Vivus shares rose 27 cents, or 2.2 percent, to $12.68 in morning trading.