Complex sentence: The current Director of the Bureau is Chaesub Lee, whose 4-year term commenced on 1 January 2015, who replaced Malcolm Johnson of the United Kingdom, who was director from 1 January 2007 to 2014.
Split into simpler sentences: The current Director of the Bureau is Chaesub Lee, whose four-year term began on 1 January 2015. His predecesdor was Malcolm Johnson of the United Kingdom, who was director from 1 January 2007 to 2014.