Japanese advertising giant Dentsu has agreed to buy US digital marketer Leapfrog. The Tokyo-based company said it would acquire a 100 per cent stake in Leapfrog, whose proprietary LFX Conversion Platform aims to optimise the consumer experience via channels ranging from social media to physical stores. Leapfrog, which is headquartered in Illinois, generated revenue of $32m in the 12 months ended December 2016 and employs 150 people, most of who are software engineers and data scientists