The present disclosure relates to methods for treating lupus nephritis with compositions comprising an effective amount of certain (2S)-N-[(1S)-1-cyano-2-phenylethyl]-1,4-oxazepane-2-carboxamide compounds of Formula (I), including pharmaceutically acceptable salts thereof, that inhibit dipeptidyl peptidase 1 (DPP1) activity. In one embodiment, the compound of Formula (I) is (2S)-N-{(1S)-1-cyano-2-[4-(3-methyl-2-oxo-2,3-dihydro-1,3-benzoxazol-5-yl)phenyl]ethyl}-1,4-oxazepane-2-carboxamide (INS1007).