Alphabet (GOOGL) shares slumped more than 4.5% as the company said longtime search chief Amit Singhal is retiring and will be replaced by John Giannandrea, an executive who has worked on machine intelligence efforts, according to a Bloomberg report. Singhal joined Google in 2000 and has led technical development since then, the Bloomberg report said Wednesday. Giannandrea has overseen recent artificial intelligence efforts, including RankBrain and an e-mail service called Smart Reply. Shares at $744.99 are trading in the top half of their 52-week range of $525.03 - $810.35.