The first matrix metalloproteinase inhibitor (MMPI) drug to be approved by the US Food and Drug Administration is also the first drug to be approved for gum disease. CollaGenex Pharmaceuticals' (Newtown, PA) Periostat, which received FDA approval at the beginning of October, is based on doxycycline hyclate, an MMPI found to inhibit the production of two out of three types of collagenase. According to Robert Ashley, vice president of corporate development at CollaGenex, overproduction of the three collagenases—MMP1, MMP8, and MMP13—leads to the breakdown of collagen and bone around the teeth, causing periodontitis. Periostat was found to suppress MMP8 and MMP13, the two collagenases with elevated levels in diseased patients. Periostat, which has showed no more side effects than placebo in phase III trials, is taken in pill form and will be available in the US from mid-November.