The chief executive of Genmab, Lisa Drakeman, has left the company with immediate effect, which some observers believe will put an end to rumours that partner GlaxoSmithKline will take the Danish company over.

Ms Drakeman, born in 1954, is retiring after 12 years in the top job, to be replaced by Jan van de Winkel, the company's chief scientific officer. Her parting seems amicable enough and the firm’s chairman, Michael Widmer, issued a statement saying Ms Drakeman’s “vision and leadership built Genmab into a leading biotechnology company”. He spoke of her “many accomplishments” and “many years of hard work and dedicated service”, saying that “we wish her a happy and relaxing retirement”.

The company noted that under her tenure, Genmab raised over $1 billion in capital, completed the largest initial public offering of any biotech company in Europe, received a host of awards and recently received regulatory approvals for Arzerra (ofatumumab), which is partnered with GSK, for refractory chronic lymphocytic leukaemia.

However, once the darling of analysts, and despite the Arzerra launch, Genmab stock has taken a bashing over the last few years. Most recently, in March, shares slumped after the company said that a late-stage trial of zalutumumab in head and neck cancer failed to meet its main goal. In December, Roche decided to end development on a mid-stage investigational monoclonal antibody the companies were working on and a month earlier Genmab said it was cutting 300 jobs and selling off its US manufacturing facility at appreciably less than it paid in February 2008.

Genmab stock was at its lowest level for some seven years last week but then soared at the beginning of this week amid rumours that GSK was preparing to swoop, given the company’s low valuation. Last night, however, shares were down again 1.3% at 57.40 Danish kroner, giving Genmab a market capitalisation of around 2.58 billion kroner, or about $428 million.

The rumours have subsided and Rune Dahl, an analyst at Denamrk’s Sydbank, told Reuters that “to me, Drakeman's exit shows a GSK takeover of Genmab is not imminent. If it had been just around the corner she would have seen it through. It would have left her with a better reputation”.