The purpose of this study is to explore the impact of vitamin D3 on the expression of alpha interferon (IFN alpha) expression in systemic lupus erythematosus (SLE) patients with vitamin D deficiency.
Inclusion Criteria: * Diagnosis of SLE by American College of Rheumatology (ACR) criteria * Serum 25-OH vitamin D level of 20 ng/mL or less * Stable disease at screening, defined as a modified Safety of Estrogens in Lupus Erythematosus National Assessment SLE Disease Activity Index (SELENA-SLEDAI) of 4 or less * Interferon (IFN) signature present. More information about this criterion can be found in the protocol * Positive anti-double-stranded (anti-ds) DNA antibody blood test at screening * If on corticosteroids, the dose must be less than 20 mg per day and stable for 4 weeks prior to screening and at study entry * If on immunosuppressive or immunomodulatory medication such as azathioprine, methotrexate, leflunomide, mycophenolate, or hydroxychloroquine, the dose must be stable for 3 months prior to screening and at study entry * If receiving a multivitamin or a vitamin D supplement, the dose of vitamin D must be 800 IU daily or less and stable for the 3 months prior to screening and at study entry * Agree to use effective contraceptive methods for the duration of the study Exclusion Criteria: * Unwilling to stop using drugs or substances that may interfere with fat absorption * Hypercalcemia * Hypercalciuria * History of hyperparathyroidism * History of kidney stones * History of cancer, except cervical carcinoma in situ and resected basal and squamous cell carcinomas of the skin * Known history of chronic viral infections, including human immunodeficiency virus (HIV), Hepatitis B, and Hepatitis C * Known active tuberculosis * Any British Isles Lupus Assessment Group (BILAG) A or B manifestation with the exception of a BILAG B mucocutaneous manifestation * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) liver function tests greater than or equal to two times the upper limit of normal * Dialysis or serum creatinine greater than 1.5 mg/dL * Expectation by the investigator to increase corticosteroid or immunosuppressive or immunomodulatory medication dose at screening, study entry, or over the course of the study * Treatment with cyclophosphamide within 3 months of screening * Treatment with rituximab within 12 months of screening * Other investigational drug and or treatment during the 4 weeks or seven half lives of the other investigational drug prior to study entry * Drug or alcohol abuse within 6 months prior to study entry * Treatment with digoxin * Treatment with teriparatide * Any condition that, in the opinion of the investigator, would jeopardize the subject's safety following exposure to the study drug * Pregnant or breastfeeding