Due to delays in enrollment

This is a Phase II, multicenter, open-label, randomized, standard of care (SOC) controlled, multiple ascending dose study to assess the safety and tolerability of IV Brincidofovir (BCV) in subjects with BKV infection after kidney transplantation. The study will be conducted at multiple study sites in several countries including Australia and Japan. Subjects who meet eligibility criteria will be enrolled in the study and will be randomized and assigned to BCV or SOC (defined as use of the same immunosuppressant administered during prescreening) before receipt of the first dose of study drug in both the Dose Escalation Phase and the Expansion Phase.

Inclusion Criteria:

• Male or female, at least 18 years of age at the time of signing the informed consent at screening.
• Kidney transplant recipient. "BK viral load increase and ≥ 3.6 log IU/mL" at 2 weeks post immunosuppression reduction or "BK viral load does not decrease by ≥ 0.3 log IU/mL" at 4 weeks post immunosuppression reduction during prescreening.

(Note: Immunosuppressant reduction needs to be continued during the screening period).

• eGFR ≥ 30 mL/min.
• Subjects under immunosuppression with tacrolimus, MMF/Myfortic, and/or corticosteroid.

Exclusion Criteria:

• Subjects who weigh ≥ 120 kg.
• National Institutes of Health/NCI CTCAE Grade 2 or higher diarrhea (ie, increase of ≥ 4 stools per day over usual pretransplant stool output) within 7 days before Day 1.
• Poor clinical prognosis, including active malignancy or use of vasopressors other than low dose (eg, ≤ 5 μg/kg/min) dopamine for renal perfusion within 7 days before Day 1.
• Use of renal replacement therapy within 7 days before Day 1.
• History of intolerance to cidofovir or related compounds (ie, other nucleotide derivatives [adefovir or tenofovir])