Spero Therapeutics (NASDAQ:SPRO – Get Rating) was downgraded by Zacks Investment Research from a “buy” rating to a “hold” rating in a research note issued on Tuesday, Zacks.com reports. According to Zacks, “Spero Therapeutics Inc. is a multi-asset, clinical-stage biopharmaceutical company. It focused on identifying, developing and commercializing novel treatments for multi-drug resistant bacterial infections. […]