Inclusion Criteria:

• Patients must be ≥18 years of age at the time of signing the informed consent.
• Patients who had a kidney transplant performed ≥ 28 days prior to enrollment.
• BKV, based on the following criteria (both must be met):
  • Any positive whole blood or plasma BK viral load at a local laboratory obtained ≤ 90 days before the start of screening;
  • Confirmation of BK viremia of 350 copies/mL – 10,000,000 copies/mL as determined by the central laboratory at screening.
• At least 1 identified, suitably matched PSL cell line for infusion is available.
• Male and/or female.
• Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.
• Male patients:
  • Male patients are eligible to participate if they agree to the following during the study treatment period and for at least 90 days after the last dose of study treatment;
  • Refrain from donating sperm; PLUS, either:
  • Be abstinent from heterosexual intercourse as their preferred and usual lifestyle (abstinent on a long term and persistent basis) and agree to remain abstinent; OR
  • Must agree to use contraception /barrier as detailed below:
  • Agree to use a male condom and should also be advised of the benefit for a female partner to use a highly effective method of contraception as a condom may break or leak when having sexual intercourse with a woman of childbearing potential (WOCBP) who is not currently pregnant;
• Female patients:
  • A female patient is eligible to participate if she is not pregnant or breastfeeding, and 1 of the following conditions applies:
  • She is a woman of non-childbearing potential (WONCBP); OR
  • She is a WOCBP and using an acceptable contraceptive method during the study treatment period and for at least 90 days after the last dose of study treatment. The Investigator should evaluate the potential for contraceptive method failure (e.g., noncompliance, recently initiated) in relationship to the first dose of study treatment;
  • A WOCBP must have a negative highly sensitive serum pregnancy test within 21 days before the first dose of study treatment.
• The Investigator is responsible for review of medical history, menstrual history, and recent sexual activity to decrease the risk for inclusion of a woman with an early undetected pregnancy.

Exclusion Criteria:

• Undergone allogeneic hematopoietic cell transplantation.
• Evidence or history of GVHD or CRS.
• Uncontrolled or progressive bacterial or fungal infections (ie, evidence of bacteremia, fungemia, dissemination, and/or organ-specific infection not well controlled by present therapies).
• Uncontrolled or progressive viral infections (ie, evidence of viremia, dissemination, and/or organ-specific infection not well controlled by present therapies) not targeted by PSL.
• Uncontrolled or progressive EBV-associated post-transplant lymphoproliferative disorder.
• Known or presumed pneumonia.
• Hemodynamic or respiratory instability defined as either of the following:
  • Requirement for continuous infusions of inotropes or vasopressors for blood pressure support;
  • Requirement for endotracheal intubation or mechanical ventilation.
• Evidence of any medical condition that in the opinion of the Investigator might interfere with the patient’s ability to participate in the trial.
• Ongoing therapy with high-dose systemic corticosteroids (i.e, prednisone dose > 0.5 mg/kg/day or equivalent).
• Patients who received, or are planned to receive, abatacept or belatacept, within 3 months of screening, or who received equine anti-thymocyte globulin ([ATG] Atgam®) or rabbit ATG (Thymoglobulin ®) in doses of > 4.5 mg/kg or alemtuzumab (Campath-1H) or other immunosuppressive T cell-targeted monoclonal antibodies < 28 days prior to randomization.
• Receipt of other investigational antiviral treatments (e.g., anti-BK monoclonal antibodies) within 28 days or 5 half-lives (whichever is longer) prior to randomization.
• Liver dysfunction, defined as liver transaminases (i.e., aspartate aminotransferase or alanine aminotransferase) >5 times the upper limit of normal (ULN) or direct bilirubin >2 times the ULN reference per local laboratory.
• Renal dysfunction, defined as estimated glomerular filtration rate (eGFR) (estimated by Modified Dose in Renal Disease [MDRD] formula) < 20 mL/min/1.73 m^2.
• Pregnant or nursing or planning to become pregnant.
• ABO incompatible or complement-dependent lymphocytotoxic crossmatch positive transplant (isolated positive B cell crossmatches are not an exclusion criterion).
• Weight < 40 kg.
• History of hypersensitivity to an y of the components of the Investigational Product.

Eligibility last updated 12/9/21. Questions regarding updates should be directed to the study team contact.