Using a human cathepsin K-targeting inhibitor screen, a new leupeptin analogue, leupeptazin (1), containing an unprecedented piperidinotriazine moiety, was isolated from a liquid culture of soil Streptomyces sp. IS2-4 collected in northern Italy. The structure of leupeptazin was established using HRESIMS as well as 1D and 2D NMR data. The inhibitory activity of the compound towards the collagenase cathepsin K was tested in vitro to reveal moderate activity with an inhibition constant, K