Lee-Chang joined the agency last month from Frank PR, where she had been a director since 2013. Before that she had worked at Publicasity and in-house at LG Electronics, having started her career at Cake.
She will lead the agency's brand comms team with a brief to drive growth and lead certain key clients.
The new recruit's previous experience includes work with clients Nintendo, Orange and Danone, while Lexis works with companies including Coca-Cola, Harley-Davidson, Pizza Hut and Pernod Ricard – the latter won at the end of last year.
Lee-Chang said she wanted to "further our creative insight-led thinking across even more exciting brands beyond an already impressive client roster".