Safety, Tolerability and Efficacy of AntiBKV as Treatment of BKV Infection in Kidney Transplant Recipients

Inclusion Criteria: 1. Male or female aged 18 years or older 2. Kidney transplantation within 24 months prior to enrollment 3. Kidney transplant recipient with first-time BKV DNAemia (evaluated during routine clinical monitoring by the local laboratory and acknowledged by a physician within four months prior to Day 1). BKV DNAemia is either defined by BKV-DNAemia of one time \>10,000 copies/mL, or \>1,000 copies/mL sustained for at least one week (confirmed by two consecutive measurements. Note: The second, most recent laboratory value must be acknowledged by a physician within four months prior to Day 1) 4. Kidney transplant recipients with adequate and/or stable allograft function as indicated by estimated glomerular filtration rate ((e)GFR) ≥ 30 mL/min 5. Female subjects (if of childbearing potential) must agree to use adequate and reliable contraceptive measures throughout their participation in the trial. Contraceptive use by women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies 6. Ability to provide written informed consent Exclusion Criteria: 1. Patients with previous diagnosis of BKV DNAemia (defined as one time \> 10,000 copies/mL, or \> 1,000 copies/mL sustained for at least one week (confirmed by two consecutive measurements) since last kidney transplantation 2. Known hypersensitivity to any component of the IMP 3. Transplanted kidney disease with an estimated glomerular filtration rate ((e)GFR) \< 30 mL/minute at screening 4. Uncontrolled acute or chronic infection other than BKV infection at screening which might interfere with study participation at the discretion of the investigator 5. Recipients who are treated or planned to be treated with a mTOR inhibitor or belatacept as part of their immunosuppression regimen post-transplantation at the time of enrollment and during the study period 6. Recipients who are treated or planned to be treated during study participation with leflunomide at the time of enrollment and during the study period 7. Recipients who in the opinion of the investigator are likely to require antibody-depletion therapy during trial participation. Antibody-depletion therapies include but are not necessarily limited to plasmapheresis, immunoadsorption, and intravenous immunoglobulins (IVIg) 8. Recipients with active kidney transplant rejection or FSGS 9. Recipients who have medical conditions or receive concomitant medications that prevent the recipient from undergoing allograft biopsy 10. Recipients with known DSA (de novo or pre-transplantation). Kidney transplant recipients with low-level pretransplant DSAs (\< 1000 mean fluorescence intensity (MFI)) can be included if no impact on the study assessments is expected by the discretion of the investigator. 11. (exclusion criterium deleted) 12. Recipients with extremely high BKV DNAemia (\> 10,000,000 copies/ml) or hemorrhagic cystitis 13. Recipients who in the opinion of the investigator are likely to develop recurrent native kidney disease (e.g. IgA nephritis, FSGS, C3 glomerulonephritis) 14. Recipients with a functionally significant ureteral stricture 15. Pregnant or nursing (lactating) women 16. Known current active or latent TB or any history, in the opinion of the investigator, that confers a risk of reactivation of latent TB and precludes the use of conventional immunosuppression 17. History of splenectomy or asplenia 18. Any condition, that in the opinion of the investigator, would interfere with the evaluation of the investigational product or interpretation of the participant safety data or study results 19. History of malignancy within the past five years, except completely excised basal cell or squamous cell carcinoma of the skin, or cervical carcinoma in situ at least two years prior to screening 20. Participation in another interventional clinical trial during trial participation or within 30 days prior to the IMP dosing or planned dosing 21. History of alcoholism or drug addiction within one year of screening. Substance use disorder will be an exclusion criterion, at investigator's discretion.