Jeff Kindler of Pfizer, who resigned abruptly at the end of 2010.
Richard Clark of Merck, who handed over the reins to Ken Frazier in 2011.
Bill Weldon of J&J, who retired this month.
Kevin Sharer of Amgen, who retires in May.
Brennan, who is stepping down in June after a disappointing start for AZ in 2012.
And Miles White of Abbott, the only one of the six who remains as CEO—but of a company that is spinning out its brand name Rx business under a different CEO.