Two decades ago, Itaru Tanimura ended a 12-year run at McKinsey & Co. to lead M3 Inc., an online provider of medical information and services backed by entertainment giant Sony Corp.

What followed was a flurry of acquisitions that turned the Tokyo-based company into a $39 billion global behemoth. M3 now has about 40 subsidiaries and affiliates, including MDLinx Inc. in the U.S. and Britain’s Ltd.

M3 helps pharmaceutical companies, doctors and their patients access information online over its platforms, removing the need for in-person visits — something that proved important in the time of COVID-19. Its shares have almost doubled this year, surging the most of any company in the 225-issue Nikkei average and taking the fortune of Tanimura to $1.2 billion, according to the Bloomberg Billionaires Index.