This is a 12-month phase 2, prospective, open label study to evaluate the effect of rituximab with mycophenolate mofetil (MMF)on the PRA of 14 highly sensitized patients who just completed an 8 month trial of MMF treatment alone. PRA values obtained at study enrollment and at 6 and 12 months on combined therapy as well as the rates of transplant will be compared and evaluated using descriptive analysis.

BACKGROUND: Patients who have been exposed to human tissue by prior transplants, blood transfusion or pregnancy may develop and maintain anti-bodies against these foreign human cells (SENSITIZATION). As a result of sensitization these patients are more likely to reject an organ donated from an individual who possesses a similar human cell marker (ANTIGENIC)profile. These sensitized patients will remain on the kidney transplant waiting list up to twice as long as those who are not pre-sensitized.

The Panel of Reactive Antibodies (PRA) is a test panel used to measure the patient reactivity to human leukocyte cell antigens (HLA). A PRA of 75% means the patient reacted to 75% of the antigens on the panel. A high PRA indicates that the subject already has antibodies and is highly SENSITIZED. Spontaneous decreases in PRA titers rarely occur. Thus the probability of transplantation in sensitized patients is significantly decreased.

RATIONALE for use of Rituximab:

By reducing specific B-cell populations Rituximab is currently used as a treatment in auto-immune diseases such as lupus erythematosus and rheumatoid arthritis and some cancers such as B-cell non-Hodgkin's lymphoma. It has been reported to have a potential roll in decreasing anti-human lymphocyte (HLA) antibodies post transplant. More studies are needed to assess its possible benefit among pre-transplant patients. Vierira et al. ["Rituxan for reduction of anti-HLA antibodies in patients awaiting renal transplantation", Am J Transplantation 2002;2:A870] reported on the use of rituximab in sensitized patients. Nine patients on dialysis with a PRA > 50% were treated with rituximab (n=3 per group) at 50, 150, or 375mg/m2. No significant change was seen in WBC, hemoglobin, platelet count, chemistry, liver enzymes or CMV IgG titers. At three days and 6 months after infusion there was a decline in the B cell count compared to pre-infusion levels. In 44%, a decline in PRA was seen. The patients receiving the higher doses had a larger decrement in antibody titers.

GENENTECH, INC. will provide Rituximab, labeled for investigational use. Rituximab is formulated for IV administration as a sterile product as a sterile, preservative-free liquid concentrate for intravenous (IV) administration.

STUDY DESIGN: This is a 12-month phase 2, prospective, open label study to evaluate the effect of rituximab with mycophenolate mofetil (MMF)on the PRA of 14 highly sensitized patients who just completed an 8 month trial of MMF treatment alone. PRA values obtained at study enrollment and at 6 and 12 months on combined therapy as well as the rates of transplant will be compared and evaluated using descriptive analysis.

Primary Endpoints: The number of subjects who experience a decrement from baseline in their Panel of Reactive Antibody values (PRA I, PRA II) or cPRA (calculated PRA when available) at: baseline, 6 and 12 months of study initiation.

Secondary Endpoints: The number of subjects who received a transplant The number of subjects with a negative crossmatch if transplanted.

STUDY POPULATION: Patients on the kidney transplant waiting list who are currently receiving hemodialysis and who have a Panel of Reactive Antibodies (PRA) titer levels over 50% after completing 8 months of mycophenolate mofetil (MMF) treatment alone.

SCREENING: Subjects will be consented, then screened clinically for occurrence of infection, Tuberculosis exposure and for protective antibodies in response to prior vaccination.

RITUXIMAB DOSAGE AND ADMINISTRATION: The Rituximab dose is 1000mg (1gm) given as a single I.V. infusion for 2 doses (days 1 and 15). No extra dosing will be given. Rituximab may be administered in an outpatient setting. Hypersensitivity reactions may occur. Premedication, consisting of acetaminophen (1gm) and diphenhydramine (50mg or equivalent dose) by mouth 30 to 60 minutes prior to the start of an infusion will be considered before each infusion of Rituximab. Rituximab will not be re-administered after initial dose regimen.

(MMF) Mycophenolate mofetil DOSAGE AND ADMINISTRATION: Dosing of MMF will continue at the highest tolerated dose the subject was taking at the completion of the parent study: "Highly Sensitized Patients: effects of mycophenolate mofetil (MMF) on anti- human lymphocyte antibody (HLA) levels in patients awaiting renal transplant". The dose will be adjusted according to standard practices, gastrointestinal tolerance and WBC count.

CLINICAL AND LABORATORY SAFETY EVALUATIONS:

SCREENING:

• Medical history and documentation of the rationale for treatment of the patient's disease with Rituximab.
• Pregnancy test (serum or urine) for women of childbearing potential must be done prior to initial Rituximab treatment date.
• Medical history to include: age, sex, prior transplant history, blood transfusion history, prior pregnancy history, history of autoimmune disease, infection history over the last 5 years, and immunization history.
• Physical examination, including vital signs, and performance status.
• Hematology (within 2 weeks of treatment): complete blood count (CBC) with differential and platelet count.
• Serum Chemistries: glucose, blood urea nitrogen, serum creatinine, uric acid, total bilirubin, alkaline phosphatase, low density lipoprotein, high density lipoprotein, total protein, albumin, aspartate aminotransferase(AST), alanine aminotransferase (ALT), and serum calcium.
• Serology Testing as appropriate: Hepatitis B, Hepatitis C, HIV
• IgG and IgM total antibody counts.
• Drug Monitoring: Baseline = pre-infusion. Serum drug levels for Ritux will also be measured for safety. Human Anti-Rituximab Antibody (HACA)is a test for presence of antibodies against rituximab.
• Lymphocyte Sub Group: A sub-group of type-B lymphocytes called 'CD-19 Cells' are specifically impacted by Rituximab and will be used as a marker of drug efficacy.

ON GOING EVALUATIONS Post -Treatment:

For safety the total IgG and IgM levels will be monitored and IgG supplemented if levels decrease below normal values. Additionally WBC counts that drop below 3.0 will result in changes in the MMF dose. If serious infections occur MMF will be discontinued. Patients will be followed for one year after initial rituximab infusion.

• Hematology: monitor CBC + differential weekly for 1 month then monthly
• Monthly: PRAs will be monitored monthly through the 12th month of the study. The standard PRA value is the sum of anti-bodies produced by 2 main groups of lymphocytes; Class I and Class II. We will have PRA I and PRA II antibody classes reported separately as well as PRA reporting using a calculation (cPRA).
• Quarterly: Serology Testing as appropriate: Hepatitis B, Hepatitis C, HIV, IgG and IgM total antibody counts.
• Monitor Serum Ritux and HACA levels at baseline, 6 months and 9 months.
• Monitor CD19+ B-cells at baseline, weeks 1, 2, 4, months 3, 6, 9 and 12.

Inclusion Criteria:

• Age range 18 - 75, inclusive
• Able and willing to give written informed consent and comply with the requirements of the study protocol
• Outpatient status
• Patients with a Panel of Reactive Antibodies (PRA) over 10% after an 8-month trial of MMF monotherapy
• Patients with updated immunizations for tetanus, influenza, hepatitis B, pneumococcus
• Patients with a negative purified protein derivative(PPD ) screen for tuberculosis (TB)within the last 6 months. If subject has a prior history of TB or positive PPD, documentation of adequate treatment is required.
• Women who are of childbearing potential must have a negative serum pregnancy test prior to being enrolled in the study and agree to use a medically acceptable method of contraception throughout the study and for twelve months (1 year) after completion of treatment.
• Men must agree to use an acceptable method of birth control during treatment and for twelve months (1 year) after completion of treatment.
• Liver enzymes ALT and AST less than 2 times the normal limit.

Exclusion Criteria:

• Active infection
• Receipt of live vaccine within 4 weeks prior to first infusion.
• Previous treatment with rituximab (MabThera® / Rituxan®)
• History of multiple recurrent infections defined as more than 3 urinary tract infections, 2 episodes of pneumonia or 3 episodes of otitis/sinusitis in one year, or more than two dialysis line or peritoneal infections within one year.
• Infection with hepatitis C virus (HCV) or hepatitis B virus(HBV) or human immunodeficiency virus (HIV), lack of documentation of treatment of a positive PPD, pregnant or breast-feeding, baseline leukopenia, white blood cell count (WBC) less than 4.0, thrombocytopenia (platelet count less than 100,000/mm) or difficult to treat anemia, a hematocrit chronically less than 32 on intravenous iron and EPO (erythropoietin) therapy, history of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies.
• Concomitant malignancies or previous malignancies within the last five years, with the exception of adequately treated basal or squamous cell carcinoma of the skin or carcinoma in situ of the cervix.
• History of psychiatric disorder
• Significant cardiac or pulmonary disease (including obstructive pulmonary disease)