Updated project metadata. Complement inhibition has been successfully used to treat periodontitis in animal models. However, proteome studies that investigated the role of complement C3 were missing. The objective of this study was to characterize local tissue exudate (“gingival crevicular fluid”; GCF) changes after administration of a potent C3 inhibitor (Cp40, also known as AMY-101) to cynomolgus monkeys (Macaca fascicularis) with established periodontitis. Cp40 was administered locally in the maxillary gingival tissue either once per week (n=5 animals) or three times per week (n=10 animals), for six weeks followed by another six weeks of observation in the absence of treatment. The GCF were collected for liquid chromatography–mass spectrometry analysis (LC-MS/MS).