U.K. pharma giant GlaxoSmithKline highlighted the effects of the falling value of sterling on its second-quarter results with the company's chief executive, Andrew Witty, forecast a "huge tailwind" for the company on the back of the weaker pound.

Speaking to CNBC, Witty said he expected a "19 percent tailwind" on the company's earnings if sterling remains on or around the same level it was at June 30.