Kidney Week

Abstract: FR-PO1219

Fast Tacrolimus Metabolism Is Associated with BK Virus Infection in Kidney Transplant Recipients

Session Information

• Transplantation: Clinical - Rejection, Biomarkers, and Pharmacology
  October 23, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Transplantation

• 2002 Transplantation: Clinical

Authors

• González Maldonado, Marilyn, Instituto Mexicano del Seguro Social Delegacion Jalisco, Guadalajara, Jal., Mexico

Marilyn González Maldonado, MD

• Hernández Rea, Yair Alejandro, Instituto Mexicano del Seguro Social Delegacion Jalisco, Guadalajara, Jal., Mexico

Yair Alejandro Hernández Rea, MD

• Rojas-Campos, Enrique, Instituto Mexicano del Seguro Social Delegacion Jalisco, Guadalajara, Jal., Mexico

Enrique Rojas-Campos, MD

• Padilla-Peralta, Benigno Daniel, Instituto Mexicano del Seguro Social Delegacion Jalisco, Guadalajara, Jal., Mexico

Benigno Daniel Padilla-Peralta, MD

• Banda Lopez, Adriana, Instituto Mexicano del Seguro Social Delegacion Jalisco, Guadalajara, Jal., Mexico

Adriana Banda Lopez, MD

• Cruz Landino, Moises, Instituto Mexicano del Seguro Social Delegacion Jalisco, Guadalajara, Jal., Mexico

Moises Cruz Landino, MD

Group or Team Name

• Centro Médico Nacional de Occidente, IMSS

Background

Tacrolimus (TAC) remains the cornerstone of maintenance immunosuppression after kidney transplantation; however, its marked pharmacokinetic variability may influence post-transplant outcomes. A TAC concentration-to-dose (C/D) ratio <1.05 ng/mL/mg identifies fast metabolizers, a phenotype previously associated with nephrotoxicity, impaired graft function, and graft loss. However, its association with BK virus (BKV) viremia has not been fully characterized.

Methods

We evaluated the association between TAC metabolic phenotype, assessed by the TAC C/D ratio, and BKV viremia during the first year after kidney transplantation.

We performed a retrospective single-center cohort study including 310 adult kidney transplant recipients transplanted in 2023. TAC C/D ratios were assessed at months 1, 3, and 6 post-transplantation. Patients were classified as fast metabolizers (C/D <1.05) or slow metabolizers (C/D ≥1.05). BKV viremia events during the first year after transplantation were analyzed according to post-transplant period. Associations were evaluated using chi-square tests and multivariate logistic regression adjusted for recipient sex, body mass index, and TAC C/D ratios at months 1 and 3. For BKV viremia analysis, the month 6 TAC C/D ratio was used as the primary predictor, considering TAC metabolism as a dynamic phenotype over time.

Results

Using the 1.05 cutoff, 23.9% of recipients were fast metabolizers at month 1, 15.0% at month 3, and 22.0% at month 6. A total of 47 BKV viremia events occurred during the first post-transplant year (months 1–3: 3; months 3–6: 15; months 6–12: 29). In multivariate analysis, a month 6 TAC C/D ratio <1.05 was independently associated with BKV viremia (OR 3.64, 95% CI 1.84–7.17). High CMV-risk status and thymoglobulin induction therapy were also independently associated with BKV viremia (OR 2.38, 95% CI 1.10–5.13).

Conclusion

The TAC C/D ratio is a simple, inexpensive, and clinically accessible biomarker that may help identify kidney transplant recipients at increased risk for BKV viremia. Early recognition of fast metabolizers could support individualized immunosuppressive management, including intensified virological surveillance and proactive TAC dose adjustment strategies.