SAC Capital Advisors, one of the nation's most successful hedge funds, is a focus of a Securities and Exchange Commission investigation into whether traders used inside information to profit from the $15bn takeover of biotechnology firm MedImmune in 2007, people familiar with the matter say.

It was not previously known that SAC, run by star manager Steven Cohen, was a focus of the SEC insider-trading probe. The probe is part of a broad SEC inquiry into trading by various hedge funds, including SAC and its affiliated funds, in stocks connected to some of the biggest health-care deals of the past decade, these people say.