Gelesis has appointed Harry Leider to serve as the Boston company’s chief medical officer and executive vice president. Leider most recently worked at Walgreens Boots Alliance (NASDAQ: WBA), where he was chief medical officer and group vice president. His experience includes executive posts at Ameritox, XLHealth, and HealthNet. Since 2015, Leider has also been a strategic advisor to PureTech Health, the investment firm that founded Gelesis. Gelesis develops drugs to treat obesity and other chronic diseases related to the gastrointestinal tract. The company is preparing to file for FDA approval of lead compound Gelesis100, a weight loss drug.