Shares of Kindred Biosciences Inc. — a darling of the Bay Area biotech IPO class of 2013 — fell more than 28 percent Thursday after the company revealed that its experimental osteoarthritis drug for dogs failed a key clinical trial. Dogs that received a placebo instead of the pain and inflammation drug CereKin had a better response rate than expected, the Burlingame company (NASDAQ: KIN) said. CereKin, known generically as diacerein, inhibits interleukin-1, a protein that becomes inflamed and…