Glomerulonephritis is one of the major disease manifestations of systemic lupus erythematosus (SLE). Around one-third of the patients, however, do not respond to conventional immunosuppressive therapy, and they have a high risk of progressing to dialysis-dependent renal failure. Recent studies suggest that immunosuppressive therapy targeted against the calcineurin pathway of T-helper cell, for example, tacrolimus, may be effective in the treatment of primary glomerulonephritis. The investigators plan to an open-label single-arm study the efficacy and safety of long-acting tacrolimus in the treatment of treatment-resistant lupus nephritis. Twenty-five patients with biopsy-proven lupus nephritis will be recruited. They will be treated with oral prednisolone and long-acting tacrolimus for 6 months, followed by 6 months of maintenance steroid and azathioprine. Proteinuria, renal function, clinical and serologic lupus activity will be monitored. This study will explore the potential role of long-acting tacrolimus in resistant lupus nephritis, which has a poor prognosis and no effective treatment at the moment.