The invention provides a human DPP1 which is associated with the infections, cardiovascular diseases, respiratory diseases, cancer, endocrinological diseases, metabolic diseases, gastroenterological diseases, inflammation, hematological diseases, muscle skeleton diseases, neurological diseases and urological diseases. The invention also provides assays for the identification of compounds useful in the treatment or prevention of infections, cardiovascular diseases, respiratory diseases, cancer, endocrinological diseases, metabolic diseases, gastroenterological diseases, inflammation, hematological diseases, muscle skeleton diseases, neurological diseases and urological diseases. The invention also features compounds which bind to and/or activate or inhibit the activity of DPP1 as well as pharmaceutical compositions comprising such compounds.