Complex sentence: Emma Natasha Walmsley (born June 1969) is a British businesswoman, the CEO-designate of GlaxoSmithKline, who will assume the role when Sir Andrew Witty retires in March 2017.
Split into simpler sentences: Emma Natasha Walmsley (born June 1969) is a British businesswoman and CEO of GlaxoSmithKline. She assumed the role when Sir Andrew Witty retired in March 2017.