An Open-Label, Study to Treat Patients With Renal Allograft and Polyoma BK Viruria

This is a multicenter, randomized trial that will evaluate the effect of a combination of
leflunomide and orotic acid for the treatment of Polyoma BK viruria. In this multicenter
trial, renal allograft patients with the diagnosis of Polyoma BK viruria as determined by a
viral level in the urine of 25 million or more copies/mL, and no detectable viremia, will
complete a screening visit (V1) to determine eligibility for the study based on
inclusion/exclusion criteria. Patients that meet the entrance criteria for this study will be
randomly assigned to one of two treatment groups at Visit (2) and enter a 4 month dosing
period.

Inclusion Criteria:

1. Patients, 75 years of age or less, with the diagnosis of renal allograft Polyoma BK
viruria of 10 million or more copies/mL in their urine confirmed by PCR at the central
laboratory.

2. No viremia (viremia is defined as greater than 1,000 copies/ml plasma on two
consecutive tests two weeks or more apart as measured at the designated central
laboratory),

3. Serum creatinine <2.0 mg/dL

4. Hct > 30%

5. WBC > 3,500 x 103/L

6. Platelet count > 150,000 x 103/L

7. Normal values for ALT, AST and bilirubin; Alk Phos < 2 X upper limits of normal

8. No symptomatic cardiac, pulmonary, GI, hepatic or neurologic disease

9. No other active infections

10. Receiving CyA or Tacrolimus, Mycophenolate/Azathioprine + prednisone.

11. Is not pregnant as verified by a pregnancy test

Exclusion Criteria:

1. Is not able to comply with study procedures and dosing.

2. Has psychiatric instability.

3. Has an active systemic infection including Hepatitis B or C, HIV, or on anti-viral
therapy within seven days of entering the study. Note however, that the subjects may
be taking ganciclovir, valaciclovir, acyclovir and valganciclovir and therefore these
are not exclusionary antiviral medications.

4. Has BK viremia (viremia is defined as greater than 1,000 copies/ml plasma on two
consecutive tests two weeks or more apart as measured at the designated central
laboratory), or has had a single episode of BK viremia. (viremia is defined as greater
than 1,000 copies/ml plasma on two consecutive tests two weeks or more apart as
measured at the designated central laboratory or the local laboratory),

5. Has a cancer diagnosis within past five years with potential for recurrence.

6. Has received experimental drug within past 3 months.

7. Is receiving immune suppressive drug other than those listed above calcineurin
inhibitor, mycophenolate/azathioprine and +/- corticosteroid)

8. Is a woman of child bearing potential or is a male with female partner of child
bearing potential who is unwilling to use reliable contraception.

9. Has any neurologic abnormalities including peripheral neuropathy.

10. Is receiving concomitant therapy with drug known to have hepatotoxic risk.

11. Has known or suspected liver disease or current alcohol abuse.