Nearly 15 years after Glaxo Wellcome plc and SmithKline Beecham plc merged to form the world's largest drug company, GlaxoSmithKline plc is steadily downsizing to focus on areas like vaccines and respiratory diseases where it thinks it can be a global leader.

CEO Andrew Witty has faced several serious challenges - some unforeseen and others not - during his six-year tenure at the top of GSK, first among them being the steady erosion of drug sales as a result of patent expirations.