Safety of Tofacitinib, an Oral Janus Kinase Inhibitor, in Systemic Lupus Erythematosus

Background: Systemic lupus erythematosus (lupus) is an autoimmune disease that often involves many systems and organs of the body. Symptoms can include fever, joint pains, and rashes. Serious lupus can also damage organs like the kidneys, lungs, or brain. Drugs used for lupus can have serious side effects. Also, the drugs don t help some people. Researchers want to find new, more effective and safe treatments. Objective: To evaluate the safety and tolerability of the drug tofacitinib (study drug) in people with lupus. Eligibility: People ages 18 and older who have mild to moderate lupus and are not currently or haven t recently had certain lupus treatments. Design: Participants will be screened in another protocol. Participants will have 7 five-hour visits over about 3 months. They will fill out multiple questionnaires. They will have tests, including: * Physical exam * Blood and urine tests * ECG/EKG: Soft electrodes are stuck to the skin to monitor the heart. * Optional SphygmoCor: Cuffs are attached to the arm and thigh to measure blood pressure and flow speed. * Optional Endopat: A thimble-shaped cup is placed on the finger to measure blood flow. A cuff is put on the arm to measure blood pressure and flow. * Optional CAVI: ECG electrodes are placed on both wrists, a microphone placed on the chest, and a blood pressure cuff placed on each arm and leg to measure blood pressure and velocity. Participants will receive either the study drug or a placebo. They will take this twice a day by mouth for 56 days. Participants will be contacted by phone 4 times....