The present invention provides a method for the prophylaxis or treatment of systemic lupus erythematosus and/or lupus nephritis in a patient in need thereof, which comprises administering an effective amount of [(1R)-1-({[(2, 5-dichlorobenzoyl)amino]acetyl}amino)-3-methylbutyl] boronic acid or a citric acid ester thereof, or a pharmaceutically acceptable salt thereof to the patient.
