John C. Lechleiter will step down as president and CEO of Eli Lilly & Co. at the end of the year. Replacing him will be longtime Lilly executive David A. Ricks, who currently heads Lilly Bio-Medicines. Lechleiter, an organic chemist, joined Lilly in 1979 in its process research labs and moved up the ranks. He became CEO in 2008, when patent expirations on nearly all of Lilly’s key products loomed. Although Lechleiter helped the company mitigate some of the revenue loss by expanding in areas such as animal health, his tenure as CEO was marred by a string of drug pipeline setbacks.