The present invention provides compounds of formula (I): compositions comprising such compounds; the use of such compounds in therapy (for example in the treatment or prevention of a disease or condition in which plasma kallikrein activity is implicated); and methods of treating patients with such compounds; wherein R1 to R9 are as defined herein.本發明提供式(I)化合物:包括此等化合物之組合物;此等化合物於治療上之用途(例如,治療或預防其中與血漿激肽釋放酶活性有關之疾病或病狀);及使用此等化合物治療患者之方法;其中R1至R9如本文所定義。