The purpose of this study is to examine the safety of a single dose of RG2077 in patients with systemic lupus erythematosus (SLE) who are currently receiving cyclophosphamide. This study will also determine if RG2077 is effective in decreasing disease activity in these patients.

Study hypothesis: CTLA4-Ig mediates a T cell costimulatory blockade that effectively induces an antigen-specific nonresponsiveness in T cells.

SLE is a chronic, inflammatory autoimmune disorder that may affect many organ systems, including the skin, joints, and internal organs. RG2077 has been studied for use in multiple sclerosis, another autoimmune disorder. This study will evaluate the safety and efficacy of RG2077 in SLE patients who are currently receiving cyclophosphamide.

This trial is composed of two parts. The first part is a dose-escalation study in which participants will receive one of two doses of RG2077 (0.2 mg/kg or 2 mg/kg); this part of the study will last 60 days. At screening, patients will have an IV catheter inserted into their arms for administration of cyclophosphamide and RG2077. Patients will also have medical and medication history assessments, a comprehensive physical exam, and blood and urine tests. There are 5 study visits for the first part of the trial; these will occur at screening, at study entry, and Days 1, 14, and 28. Selected visits will include physical exam, vital signs measurement, blood and urine tests, and disease activity assessment. At Days 7 and 60, patients will be contacted by phone to report their medication history and any adverse effects they have experienced.

The second part of the study will evaluate a single 10 mg/kg dose of RG2077; this part of the study will last 90 days. In the study, participants will be randomly assigned to one of two groups. At the start of the study, Group 1 participants will receive RG2077 and cyclophosphamide and Group 2 participants will receive cyclophosphamide only. There will be 9 study visits; these will occur at study screening, study entry, and Days 1, 4, 7, 14, 28, and 60. At selected visits, patients will undergo physical exam, vital signs measurement, blood tests and urine tests, and disease activity assessment.

Inclusion Criteria:

• Diagnosis of SLE by American College of Rheumatology (ACR) criteria
• Concurrent treatment with intravenous cyclophosphamide (500 to 1000 mg/m2) for at least one of the following manifestations of lupus: World Health Organization (WHO) class III, IV, or V lupus nephritis; British Isles Lupus Assessment Group (BILAG) score of A for vasculitis; BILAG score of A for cytopenia; BILAG score of A for nervous system
• Stable medication regimen for at least 4 weeks prior to study entry
• Weight between 40 kg (88.2 lbs) and 125 kg (275.6 lb)
• Willing to use acceptable forms of contraception

Exclusion Criteria:

• Moderately severe anemia (hemoglobin less than 8 mg/dL)
• Neutropenia (absolute neutrophil count less than 1,500/mm3)
• Thrombocytopenia (platelets less than 50,000/mm3)
• Positive tuberculin (PPD) test without evidence of prior treatment or administration of bacille Calmette-Guérin (BCG) vaccine
• Active infections, including HIV and hepatitis B or C
• Receipt of a live vaccine within 3 months of study entry
• End-stage renal disease with creatinine clearance less than 20 ml/min/1.73 m2
• History of cancer. Patients with a history of carcinoma in situ and treated basal and squamous cell carcinomas are not excluded.
• Pregnant or breastfeeding

Participant level data and additional relevant materials are available to the public in 1.) the Immunology Database and Analysis Portal (ImmPort), a long-term archive of clinical and mechanistic data from DAIT-funded grants and contracts that also provides data analysis tools available to researchers; and 2.) TrialShare, the Immune Tolerance Network (ITN) Clinical Trials Research Portal that makes data from the consortium's clinical trials publicly available.