Clinical Significance of Mycophenolate Mofetil Withdrawal in Kidney Transplant Recipients

Tacrolimus After rATG and Infliximab Induction Immunosuppression-RIMINI Trial

BACKGROUND

Infliximab selectively targets recently activated effector cells and, as an induction agent, might enable the safe elimination of mycophenolate from maintenance immunosuppression in kidney transplantation.

METHODS

This is a phase II international multicenter open-label single-arm confidence interval (CI)-based clinical trial of the BIO-DrIM EU consortium aimed at assessing the efficacy and safety of rabbit antithymocyte globulin and infliximab induction in kidney transplantation. Sixty-seven primary kidney transplant recipients at low risk (panel-reactive antibodies <20%, no donor-specific antibodies [DSA]) received rabbit antithymocyte globulin (2 × 1.5 mg/kg, postoperative days 0 and 1) and infliximab (5 mg/kg, postoperative day 2), followed by mycophenolate-free tacrolimus-based immunosuppression for 12 mo. The primary endpoint was efficacy failure, defined as a composite of acute rejection, graft loss, or poor graft function (estimated glomerular filtration rate <40 mL/min) at 12 mo and was based on the endpoint of the comparator study. Additionally, a historical propensity-matched control cohort was established.

RESULTS

Primary endpoint occurred in 22 of 67 patients (32.84%), with upper bound of an exact 1-sided 95% CI of 43.47%, which met the predefined criteria (efficacy failure of <40% and upper-bound 95% CI of <50%) and was similar in the historical matched cohort. By 12 mo, 79.1% of patients remained on the study protocol. Lower rates of BK replication (6% versus 22.4%; P  = 0.013) but higher rates of de novo DSAs (11.9% versus 1.5%; P  = 0.039) were observed in the study cohort.

CONCLUSIONS

A similar efficacy of the study immunosuppression regimen to the comparator study and the historical matched cohort was found. However, a higher de novo DSA emergence points to an increased risk of antibody-mediated rejection (NCT04114188).

Continuation of immunosuppression vs. immunosuppression weaning in potential repeat kidney transplant candidates: a care management perspective

Management of immunosuppression in patients with a failing or failed kidney transplant requires a complete assessment of their clinical condition. One of the major considerations in determining immunosuppression is whether or not such an individual is considered a candidate for re-transplantation. Withdrawal of immunosuppression in a re-transplant candidate can result in allosensitization and markedly reduce the chances of a repeat transplant. In this review, we summarize the effects of immunosuppression reduction on HLA sensitization, discuss the impacts of allosensitization in these patients, and explore reduction protocols and future directions. Risks of chronic immunosuppression, medical management of the failing allograft, and the effect of nephrectomy are covered elsewhere in this issue.

Immune Response to COVID-19 mRNA Vaccination in Previous Nonresponder Kidney Transplant Recipients After Short-term Withdrawal of Mycophenolic Acid 1 and 3 Months After an Additional Vaccine Dose

BACKGROUND

The impaired immune response to coronavirus disease 2019 (COVID-19) vaccination in kidney transplant recipients (KTRs) leads to an urgent need for adapted immunization strategies.

METHODS

Sixty-nine KTRs without seroconversion after ≥3 COVID-19 vaccinations were enrolled, and humoral response was determined after an additional full-dose mRNA-1273 vaccination by measuring severe acute respiratory syndrome coronavirus 2-specific antibodies and neutralizing antibody activity against the Delta and Omicron variants 1 and 3 mo postvaccination. T-cell response was analyzed 3 mo postvaccination by assessing interferon-γ release. Mycophenolic acid (MPA) was withdrawn in 41 KTRs 1 wk before until 4 wk after vaccination to evaluate effects on immunogenicity. Graft function, changes in donor-specific anti-HLA antibodies, and donor-derived cell-free DNA were monitored in KTRs undergoing MPA withdrawal.

RESULTS

Humoral response to vaccination was significantly stronger in KTRs undergoing MPA withdrawal 1 mo postvaccination; however, overall waning humoral immunity was noted in all KTRs 3 mo after vaccination. Higher anti-S1 immunoglobulin G levels correlated with better neutralizing antibody activity against the Delta and Omicron variants, whereas no significant association was detected between T-cell response and neutralizing antibody activity. No rejection occurred during study, and graft function remained stable in KTRs undergoing MPA withdrawal. In 22 KTRs with Omicron variant breakthrough infections, neutralizing antibody activity was better against severe acute respiratory syndrome coronavirus 2 wild-type and the Delta variants than against the Omicron variant.

CONCLUSIONS

MPA withdrawal to improve vaccine responsiveness should be critically evaluated because withdrawing MPA may be associated with enhanced alloimmune response, and the initial effect of enhanced seroconversion rates in KTRs with MPA withdrawal disappears 3 mo after vaccination.

Temporary reduction of immunosuppression enhances production of anti-S antibody against severe acute respiratory syndrome coronavirus 2 after vaccination in kidney transplant recipients

OBJECTIVES

The study identified factors affecting anti-S immunoglobulin G production after vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in kidney transplant recipients.

METHODS

Serum samples were prospectively collected from kidney transplant recipients, live kidney donors, and healthy volunteers 1 month after receiving the second dose of SARS-CoV-2 vaccine, and anti-S immunoglobulin G titers were measured. The mycophenolate mofetil dose was reduced before vaccination in some immunologically low-risk recipients.

RESULTS

A total of 151 kidney transplant recipients, 74 live kidney donors, and 50 healthy volunteers were included. Kidney transplant recipients had significantly lower titers of anti-S immunoglobulin G than donors and healthy volunteers (1377 ± 246, 8310 ± 932, and 9908 ± 1040 AU/ml, respectively). Only 67.3% of kidney transplant recipients, compared to 100% of donors and healthy volunteers, were positive for anti-S immunoglobulin G. Among the kidney transplant recipients, the anti-S titer was higher in younger recipients, those with higher peripheral blood lymphocyte counts and glomerular filtration rates, those without a history of antithymocyte globulin use, and those who had discontinued or received a reduced dose of mycophenolate mofetil. Younger age, higher lymphocyte count, glomerular filtration rate, and mycophenolate reduction were significantly associated with anti-S immunoglobulin G > 1000 AU/ml in nominal logistic regression analysis. There were no rejection episodes after mycophenolate modification in kidney transplant recipients.

CONCLUSIONS

Anti-S immunoglobulin G production after vaccination was attenuated in kidney transplant recipients. Mycophenolate mofetil cessation or reduction is a modifiable means to enhance anti-S immunoglobulin G production in immunosuppressed kidney transplant recipients.

Polyoma BK Virus in Kidney Transplant Recipients: Screening, Monitoring, and Management

Polyomavirus BK virus (BKPyV) infection is an important complication of kidney transplantation and allograft failure. The prevalence of viremia is 10%-15%, compared with BK-associated nephropathy (BKPyVAN) at 3%-5%. Given that there are no effective antiviral prophylaxis or treatment strategies for BKPyVAN, active screening to detect BKPyV viremia is recommended, particularly during the early posttransplant period. Immunosuppression reduction to allow viral clearance may avoid progression to severe and irreversible allograft damage. The frequency and duration of screening are highly variable between transplant centers because the evidence is reliant largely on observational data. While the primary treatment goals center on achieving viral clearance through immunosuppression reduction, prevention of subsequent acute rejection, premature graft loss, and return to dialysis remain as major challenges. Treatment strategies for BKPyV infection should be individualized to the recipient's underlying immunological risk and severity of the allograft infection. Efficacy data for adjuvant therapies including intravenous immunoglobulin and cidofovir are sparse. Future well-powered and high-quality randomized controlled trials are needed to inform evidence-based clinical practice for the management of BKPy infection.

Myeloid and Mesenchymal Stem Cell Therapies for Solid Organ Transplant Tolerance

Transplantation is now performed globally as a routine procedure. However, the increased demand for donor organs and consequent expansion of donor criteria has created an imperative to maximize the quality of these gains. The goal is to balance preservation of allograft function against patient quality-of-life, despite exposure to long-term immunosuppression. Elimination of immunosuppressive therapy to avoid drug toxicity, with concurrent acceptance of the allograft-so-called operational tolerance-has proven elusive. The lack of recent advances in immunomodulatory drug development, together with advances in immunotherapy in oncology, has prompted interest in cell-based therapies to control the alloimmune response. Extensive experimental work in animals has characterized regulatory immune cell populations that can induce and maintain tolerance, demonstrating that their adoptive transfer can promote donor-specific tolerance. An extension of this large body of work has resulted in protocols for manufacture, as well as early-phase safety and feasibility trials for many regulatory cell types. Despite the excitement generated by early clinical trials in autoimmune diseases and organ transplantation, there is as yet no clinically validated, approved regulatory cell therapy for transplantation. In this review, we summarize recent advances in this field, with a focus on myeloid and mesenchymal cell therapies, including current understanding of the mechanisms of action of regulatory immune cells, and clinical trials in organ transplantation using these cells as therapeutics.