Immunosuppression after lung transplantation: the search for the holy grail continues

mTOR inhibitors after lung transplantation: a real-life experience

Background

The mammalian target of rapamycin (mTOR) inhibitors in combination with calcineurin inhibitors (CNIs), antimetabolites and corticosteroids for immunosuppression after lung transplantation (TPL) have gained importance in patients with chronic kidney disease (CKD). The goal of this study was to characterize lung transplant recipients (LTR) treated with mTOR inhibitors, with a special focus on kidney function.

Methods

LTR transplanted at the University Hospital Zurich between December 1992 and April 2022 were analyzed. Demographics, estimated glomerular filtration rate (eGFR) before and after mTOR initiation, TPL circumstances, immunosuppressive regimens, and allograft function were recorded. We used linear regression to calculate the Mitch curves and a linear mixed-effects model to compare the eGFR.

Results

Of all LTR, 70/593 (12%) received mTOR inhibitors. Intolerance or adverse events of antimetabolites were the most common indications for mTOR inhibitor introduction. Discontinuation in 34/70 (49%) was often related to planned or urgent surgery to prevent impaired wound healing. The majority of patients had a preserved baseline eGFR at mTOR inhibitor introduction with CKD Kidney Disease Improving Global Outcomes (KDIGO) stage G1 or 2. The mean annual eGFR decline changed significantly from -16.19 mL/min/1.73 m2/year [95% confidence interval (CI): -22.27 to -10.11] 12 months before to -6.16 mL/min/1.73 m2/year (95% CI: -13.37 to 1.05) 12 months after mTOR initiation (P=0.009) showing better outcomes with earlier mTOR inhibitor initiation after lung TPL.

Conclusions

This retrospective study suggests stabilization of kidney function after mTOR inhibitor initiation in LTR documented by a slower eGFR decline after mTOR inhibitor introduction with better outcomes early after lung TPL. Intolerance or adverse events of antimetabolites are important indications for the introduction of mTOR inhibitors. A relatively high discontinuation rate (49%) can be explained by planned discontinuation of mTOR inhibitors prior to surgery to avoid impaired wound healing.

Mammalian Target of Rapamycin Inhibitors and Kidney Function After Thoracic Transplantation: A Systematic Review and Recommendations for Management of Lung Transplant Recipients

BACKGROUND

Chronic kidney disease (CKD) after lung transplantation is common and limits the survival of transplant recipients. The calcineurin inhibitors (CNI), cyclosporine A, and tacrolimus being the cornerstone of immunosuppression are key mediators of nephrotoxicity. The mammalian target of rapamycin (mTOR) inhibitors, sirolimus and everolimus, are increasingly used in combination with reduced CNI dosage after lung transplantation.

METHODS

This systematic review examined the efficacy and safety of mTOR inhibitors after lung transplantation and explored their effect on kidney function.

RESULTS

mTOR inhibitors are often introduced to preserve kidney function. Several clinical trials have demonstrated improved kidney function and efficacy of mTOR inhibitors. The potential for kidney function improvement and preservation increases with early initiation of mTOR inhibitors and low target levels for both mTOR inhibitors and CNI. No defined stage of CKD for mTOR inhibitor initiation exists, nor does severe CKD preclude the improvement of kidney function under mTOR inhibitors. Baseline proteinuria may negatively predict the preservation and improvement of kidney function. Discontinuation rates of mTOR inhibitors due to adverse effects increase with higher target levels.

CONCLUSIONS

More evidence is needed to define the optimal immunosuppressive regimen incorporating mTOR inhibitors after lung transplantation. Not only the indication criteria for the introduction of mTOR inhibitors are needed, but also the best timing, target levels, and possibly discontinuation criteria must be defined more clearly. Current evidence supports the notion of nephroprotective potential under certain conditions.

The Impact of New Treatments on Short- and MID-Term Outcomes in Bilateral Lung Transplant: A Propensity Score Study

BACKGROUND

Despite many efforts to improve organ preservation and recipient survival, overall lung transplant (LT) mortality is still high. We aimed to investigate the impact of 'prophylactic' veno-arterial extracorporeal membrane oxygenation (VA ECMO) and tacrolimus on 72-h primary graft dysfunction (PGD) and 30-day acute cellular rejection, respectively.

METHODS

All consecutive LT patients admitted to the Intensive Care Unit of the Padua University Hospital (February, 2016-2022) were screened. Only adult patients undergoing first bilateral LT and not requiring cardio-pulmonary bypass, invasive mechanical ventilation, and/or ECMO before LT, were included. A propensity score weighting analysis was employed to account for the non-random allocation of the subjects to different treatments.

RESULTS

A total of 128 LT recipients were enrolled. Compared to the 'off-pump'-group (n.47, 37%), 'prophylactic' VA ECMO (n.51,40%) recorded similar 72-h PGD values, perioperative blood products and lower acute kidney dysfunction. Compared with cyclosporine (n.86, 67%), tacrolimus (n.42, 33%) recorded a lower risk of 30-day cellular rejection, kidney dysfunction, and bacteria isolation.

CONCLUSIONS

'Prophylactic' VA ECMO recorded 72-h PGD values comparable to the 'off-pump'-group; while tacrolimus showed a lower incidence of 30-day acute cellular rejection.

Immunosuppression for Lung Transplantation: Current and Future

Purpose of the review

The number of lung transplantations performed worldwide continues to increase. There is a growing need in these patients for more effective immunosuppressive medications with less toxicity.

Recent findings

This review article summarizes the recent studies and developments in lung transplant immunosuppression. Novel immunosuppressive medications and strategies used in other solid organ transplantations are being trialed in lung transplantation. This includes the use of co-stimulation blockers like belatacept and mTOR inhibitors like everolimus. Calcineurin sparing regimens have been described in an attempt to minimize nephrotoxicity. Assays to measure the bioactivity of immunosuppressive medications to determine the global immune competence, such as Immuknow assay and Gamma interferon response are gaining traction.

Summary

Immunosuppression in lung transplant is evolving with the development of newer drugs and promising strategies to optimize immunosuppression. Further studies with multicenter randomized trials are required to increase the strength of the evidence.