The Efficacy and Safety of Calcitriol for the Treatment of Lupus Nephritis and Persistent Proteinuria

Inclusion Criteria: * aged 18-65 years * clinical quiescent SLE for at least 12 weeks * baseline SLEDAI score \<= 4 * history of biopsy-proven lupus nephritis * estimated glomerular filtration rate 15 to 60 ml/min/1.73m2 * proteinuria \> 1 g/day (or proteinuria \> 1 g/g-Cr) in 2 consecutive samples within 12 weeks despite ACE inhibitor or angiotensin receptor blocker for at least 3 months * on maintenance dose of prednisolone \< 10 mg/day, with or without other immunosuppressive medications * corrected serum calcium level \< 2.45 mmol/l * willingness to give written consent and comply with the study protocol Exclusion Criteria: * Pregnancy, lactating or childbearing potential without effective method of birth control * Severe gastrointestinal disorders that interfere with their ability to receive or absorb oral medication * History of malignancy, including leukemia and lymphoma within the past 2 years * Systemic infection requiring therapy at study entry * Any other severe coexisting disease such as, but not limited to, chronic liver disease, myocardial infarction, cerebrovascular accident, malignant hypertension * History of drug or alcohol abuse within past 2 years * Participation in any previous trial on vitamin D analogue * Patients receiving treatment of vitamin D and/or its analogue for other medical reasons within the past 4 weeks. Patients who are taking multivitamin supplement that contains vitamin D could be enrolled after 4 weeks of wash out period by changing to a preparation that has no vitamin D. * On other investigational drugs within last 30 days * History of a psychological illness or condition such as to interfere with the patient's ability to understand the requirement of the study * History of non-compliance * Known history of sensitivity or allergy to vitamin D analogs