Vivus has made a surprise announcement that its only-just elected chief executive Tony Zook is resigning due to health concerns.

Mr. Zook, former head of commercial operations at AstraZeneca, only took over as head of Vivus at the end of July after being appointed by dissident shareholder First Manhattan Co which ousted CEO Leland Wilson and much of the board.

The firm says he is leaving “due to recurring issues associated with a previously-diagnosed medical condition”. Mr Zook added that “this has been a difficult decision. Unfortunately, I cannot devote the necessary time and focus to the company, but instead must concentrate on personal health issues”.

Seth Fischer, a former senior executive at Johnson & Johnson, has been appointed as his replacement.  Now his job is to find a suitable big pharma partner for the obesity drug Qsymia (phentermine/topiramate) which has suffered disappointing sales after a weak launch.

Commenting on the news, Simos Simeonidis, an analyst with Cowen & Co, said “we expect the company to continue to face significant operational hurdles near to medium term, regardless of who is at the helm”. He added that “there should now exist a change in the overall strategic direction of the company and that there should now exist more accountability in the company, which, in our view, starts at the board level”.

 Despite its disappointing launch, “we continue to view Qsymia as a very efficacious weight loss agent and expect an eventual pickup in Qsymia scripts” in the second half of 2013.