(Adds detail, analyst comment.) By Gustav Sandstrom Of DOW JONES NEWSWIRES Genmab AS (GEN.KO) said Tuesday its Chief Executive Lisa Drakeman is retiring from her position and will be replaced by Jan G.J. van de Winkel effective Tuesday, denting market speculation that partner GlaxoSmithKline PLC (GSK) might be about to take over the Danish biotech firm. Lisa Drakeman is also retiring from her position as member of Genmab's board, the company said. Van de Winkel is a former Chief Scientific Officer at Genmab, and has more than 20 years' experience in the therapeutic antibody field, the company said. Genmab press spokeswoman Helle Husted declined to give any further comments about the CEO shift ahead of the company's press conference on the issue Wednesday afternoon. Lisa Drakeman wasn't immediately available to comment, Husted added. At 0915 GMT, shares in Genmab were up 4.9% at DKK60.85 againt a 0.2% drop in the wider Copenhagen market. The shares are down some 26% since the start of the year, but Monday soared almost 30% amid speculation that GlaxoSmithKline might place a bid for the company. Glaxo and Genmab declined to comment on market speculation about the bid Monday. Genmab, which develops antibodies for treatment of cancer, has worked with the U.K.-based pharmaceutical company on the development and commercialization of leukemia drug Arzerra. Still, analyst Rune Majlund Dahl at Sydbank said Tuesday that an upcoming bid offer now looks rather unlikely as Genmab probably wouldn't change its chief executive if the company was about to be sold. The CEO shift increases investor uncertainty to some extent, said Dahl, adding that van de Winkel might choose to change the company's current strategy. -By Gustav Sandstrom, Dow Jones Newswires; +46-8-5451-3099; [email protected] (END) Dow Jones Newswires June 15, 2010 05:25 ET (09:25 GMT)