Witty, who stepped down as head of Britain's biggest drugmaker in March, is joining U.S.-based Hatteras Venture Partners, while Slaoui has signed up with European venture firm Medicxi, the companies said in separate statements.

At Hatteras, Witty will be working with general partner Bob Ingram, another former CEO of Glaxo.

(Reporting by Ben Hirschler, editing by Louise Heavens)