Rapamycin in lung transplantation

Chronic Lung Allograft Dysfunction: Evolving Concepts and Therapies

The primary factor that limits long-term survival after lung transplantation is chronic lung allograft dysfunction (CLAD). CLAD also impairs quality of life and increases the costs of medical care. Our understanding of CLAD continues to evolve. Consensus definitions of CLAD and the major CLAD phenotypes were recently updated and clarified, but it remains to be seen whether the current definitions will lead to advances in management or impact care. Understanding the potential differences in pathogenesis for each CLAD phenotype may lead to novel therapeutic strategies, including precision medicine. Recognition of CLAD risk factors may lead to earlier interventions to mitigate risk, or to avoid risk factors all together, to prevent the development of CLAD. Unfortunately, currently available therapies for CLAD are usually not effective. However, novel therapeutics aimed at both prevention and treatment are currently under investigation. We provide an overview of the updates to CLAD-related terminology, clinical phenotypes and their diagnosis, natural history, pathogenesis, and potential strategies to treat and prevent CLAD.

Immunosuppressive strategies in lung transplantation

Lung transplantation is a viable option for those with end-stage lung disease which is evidenced by the continued increase in the number of lung transplantations worldwide. However, patients and clinicians are constantly faced with acute and chronic rejection, infectious complications, drug toxicities, and malignancies throughout the lifetime of the lung transplant recipient. Conventional maintenance immunosuppression therapy consisting of a calcineurin inhibitor (CNI), anti-metabolite, and corticosteroids have become the standard regimen but newer agents and modalities continue to be developed. Here we will review induction agents, maintenance immunosuppressives, adjunctive therapies and other strategies to improve long-term outcomes.

Survival Associated With Sirolimus Plus Tacrolimus Maintenance Without Induction Therapy Compared With Standard Immunosuppression After Lung Transplant

Importance

Median survival after lung transplant is less than 6 years. Standard maintenance therapy typically includes tacrolimus and an antimetabolite (mycophenolate mofetil or azathioprine). Replacing the antimetabolite with sirolimus after postoperative wound healing may improve long-term survival due to antifibrotic, antiproliferative, and antiaging effects of sirolimus.

Objectives

To compare survival between patients receiving sirolimus plus tacrolimus vs mycophenolate mofetil plus tacrolimus (the most common maintenance therapy) and to identify the combination of induction and maintenance therapy associated with the highest survival.

Design, Setting, and Participants

This cohort study of US recipients of lung transplants from January 1, 2003, through August 31, 2016, analyzed United Network for Organ Sharing (UNOS) data from January 1 through September 13, 2018. Because initiation of sirolimus therapy is usually delayed 3 to 12 months after lung transplant, primary analyses were based on patients alive and free of chronic rejection and malignant disease at 1 year in all groups, whereas sensitivity analyses used appropriate methods to include all patients from transplant time. Regression models adjusted for available potential confounders, including transplant center performance.

Exposures

Cell cycle inhibitor maintenance therapies, including sirolimus (n = 219), mycophenolate mofetil (n = 5782), mycophenolate sodium (n = 408), azathioprine (n = 2556), and concurrent sirolimus plus mycophenolate mofetil (n = 54), were compared within a tacrolimus-based regimen. Combinations of each induction (basiliximab, daclizumab, antithymocyte globulin, alemtuzumab, or none) and maintenance (tacrolimus plus sirolimus, mycophenolate mofetil, or azathioprine) therapy were also compared.

Main Outcomes and Measures

Survival was the primary outcome; chronic rejection incidence and subsequent mortality were secondary outcomes.

Results

Among this population of 9019 patients (median age, 57 years [interquartile range {IQR}, 46-63 years]; 5194 men [57.6%]), sirolimus plus tacrolimus was associated with better survival than mycophenolate mofetil plus tacrolimus (median, 8.9 years [IQR, 4.4-12.7 years] vs 7.1 years [IQR, 3.6-12.1 years]; adjusted hazard ratio [aHR], 0.71; 95% CI, 0.56-0.89; P = .003). Chronic rejection incidence (aHR, 0.75; 95% CI, 0.61-0.92) and mortality after chronic rejection (aHR, 0.52; 95% CI, 0.31-0.81) were lower with sirolimus plus tacrolimus. Compared with mycophenolate mofetil plus tacrolimus, survival differences for sirolimus plus mycophenolate mofetil plus tacrolimus (aHR, 1.14; 95% CI, 0.79-1.65), mycophenolate sodium plus tacrolimus (aHR, 0.95; 95% CI, 0.77-1.17), and azathioprine plus tacrolimus (aHR, 0.93; 95% CI, 0.84-1.02) were not significant. The induction-maintenance combination with the highest survival was sirolimus plus tacrolimus without induction therapy (median survival, 10.7 years [IQR, 7.3-12.7 years]; aHR, 0.48; 95% CI, 0.31-0.76; P = .002) compared with mycophenolate mofetil plus tacrolimus with induction therapy (median survival, 7.4 years [IQR, 3.9-12.6 years]).

Conclusions and Relevance

Sirolimus plus tacrolimus was associated with improved patient survival after lung transplant compared with mycophenolate mofetil plus tacrolimus; no antibody induction therapy with sirolimus plus tacrolimus was associated with maximal survival.

Immunosuppression in lung transplantation

Lung transplantation can be a life-saving procedure for those with end-stage lung diseases. Unfortunately, long term graft and patient survival are limited by both acute and chronic allograft rejection, with a median survival of just over 6 years. Immunosuppressive regimens are employed to reduce the rate of rejection, and while protocols vary from center to center, conventional maintenance therapy consists of triple drug therapy with a calcineurin inhibitor (cyclosporine or tacrolimus), antiproliferative agents [azathioprine (AZA), mycophenolate, sirolimus (srl), everolimus (evl)], and corticosteroids (CS). Roughly 50% of lung transplant centers also utilize induction therapy, with polyclonal antibody preparations [equine or rabbit anti-thymocyte globulin (ATG)], interleukin 2 receptor antagonists (IL2RAs) (daclizumab or basiliximab), or alemtuzumab. This review summarizes these agents and the data surrounding their use in lung transplantation, as well as additional common and novel therapies in lung transplantation. Despite the progression of the management of lung transplant recipients, they continue to be at high risk of treatment-related complications, and poor graft and patient survival. Randomized clinical trials are needed to allow for the development of better agents, regimens and techniques to address above mentioned issues and reduce morbidity and mortality among lung transplant recipients.

Effects of prophylactic use of sirolimus on bronchiolitis obliterans syndrome development in lung transplant recipients

BACKGROUND

Sirolimus (SIR) has been shown to stabilize the lung function in lung transplant recipients with bronchiolitis obliterans syndrome (BOS). However, there is no long-term data on the prophylactic use of SIR in lung transplant recipients. This retrospective study examines the effects of SIR in the prevention of BOS.

METHODS

From 1999 to 2009, 24 lung transplant recipients whose maintenance immunosuppression regimen consisted of tacrolimus (Tac), mycophenolate mofetil (MMF) or azathioprine (AZA), and prednisone (Pred), were switched to Tac, SIR, and Pred at 1 year after transplantation. From these 24 patients, 5 developed side effects that necessitated the cessation of SIR within 1 year, while 19 patients tolerated long-term use of SIR. The clinical outcomes of these 19 patients (SIR group) were compared with 22 lung transplant recipients whose immunosuppression regimen consisted of Tac, MMF or AZA, and Pred from the time of transplant (MMF group). Survival rates and freedom from BOS were calculated by the Kaplan-Meier method.

RESULTS

The SIR group had a lower incidence of BOS and viral infection (p = 0.05), and higher survival rates (p = 0.004). The SIR group had lower levels of Tac and received less Pred. The incidences of acute rejection, carcinoma, hypertension, and diabetes were similar between both groups.

CONCLUSIONS

Results from this study suggest that conversion to SIR 1 year after lung transplantation improves survival and decreases the development of BOS. Randomized studies with higher number of patients are needed to determine the prophylactic efficacy of sirolimus in preventing the development of BOS.

Diagnosis and treatment of pulmonary chronic GVHD: report from the consensus conference on clinical practice in chronic GVHD

This consensus statement established under the auspices of the German working group on BM and blood stem cell transplantation (DAG-KBT), the German Society of Hematology and Oncology (DGHO), the Austrian Stem Cell Transplant Working Group, the Swiss Blood Stem Cell Transplantation Group (SBST) and the German-Austrian Pediatric Working Group on SCT (Päd-Ag-KBT) summarizes current evidence for diagnosis, immunosuppressive and supportive therapy to provide practical guidelines for the care and treatment of patients with pulmonary manifestations of chronic GVHD (cGVHD). Pulmonary cGVHD can present with obstructive and/or restrictive changes. Disease severity ranges from subclinical pulmonary function test (PFT) impairment to respiratory insufficiency with bronchiolitis obliterans being the only pulmonary complication currently considered diagnostic of cGVHD. Early diagnosis may improve clinical outcome, and regular post-transplant follow-up PFTs are recommended. Diagnostic work-up includes high-resolution computed tomography, bronchoalveolar lavage and histology. Topical treatment is based on inhalative steroids plus beta-agonists. Early addition of azithromycin is suggested. Systemic first-line treatment consists of corticosteroids plus, if any, continuation of other immunosuppressive therapy. Second-line therapy and beyond includes extracorporeal photopheresis, mammalian target of rapamycin inhibitors, mycophenolate, etanercept, imatinib and TLI, but efficacy is limited. Clinical trials are urgently needed to improve understanding and treatment of this deleterious complication.

[Bronchiolitis obliterans postallogeneic stem cell transplantation: what is new?]

Bronchiolitis obliterans (BO) is a severe complication of hematopoietic stem cell transplantation (HSCT). It is considered as a respiratory manifestation of chronic graft-versus-host disease. It is quite similar to the bronchiolitis obliterans after lung transplantation. Classical therapy associates steroids and immunosuppressive drugs, however theses procedure showed a modest efficacy and have an important morbidity. Recent progresses in the physiopathology of BO post-HSCT allow to use new treatments: mTOR inhibitors, immunotherapy, extra-corporeal photochemotherapy, and bronchial anti-inflammatory effects of azithromycin, statins or antileucotriens. This review will focus on the use of these new therapies in BO post-HSCT.

Initial Single-Center Experience With Sirolimus After Lung Transplantation

BACKGROUND

Standard immunosuppression after lung transplantation includes calcineurin inhibitors, mycophenolate mofetil, and steroids. Long-term survivors of lung transplantation are often confronted with chronic kidney disease, by definition related to the intake of calcineurin inhibitors. Sirolimus has been increasingly proposed as an alternative immunosuppressive agent due to its absence of nephrotoxicity, which could be used in selected patients.

METHODS

We prospectively administered sirolimus as an alternative to calcineurin inhibitors in 10 lung transplantation recipients with persistent drug nephrotoxicity. They were switched from tacrolimus to sirolimus. Four patients also had bronchiolitis obliterans syndrome. The conversion scheme consisted of an immediate stop of tacrolimus and an 6 to 8-mg loading dose of sirolimus, followed by 4 mg/d. After 5 days, the sirolimus dose was adjusted to maintain trough levels between 12 and 18 ng/mL or 6 and 12 ng/mL for combined sirolimus and tacrolimus. Patients were monitored for renal and graft function as well as clinical status.

RESULTS

A significant decrease in creatinine was observed after 1 week of treatment (P = .011). Azotemia decreased after 1 month, remaining stable (P < .01). Pulmonary function tests did not show significant modification from before sirolimus, inception in patients with or without bronchiolitis obliterans syndrome. There were seven infections. One patient died of complications related to bronchiolitis obliterans.

CONCLUSION

Sirolimus was a useful alternative immunosuppressant, allowing significant tacrolimus withdrawal in transplant recipients with renal impairment. Sirolimus administration allowed recovery of renal function with low morbidity; it was useful for rescue of chronic renal impairment after lung transplantation.

Lung Transplantation: Advances in Immunosuppression

Since the advent of various novel immunosuppressants, including tacrolimus, rapamycin, and daclixumab. expanding variations of protocols have been developed. Little evidence exists to substantially support a single agent over another. or a combination regimen protocol over another. Therefore, the principles and the goals of immunosuppression in lung transplantation recipients will remain moving targets and continue to evolve, and the use of large-scale, multi-institutional clinical trials is imperative to develop optimal immunosuppressive strategies.

Toxicidade pulmonar induzida pela rapamicina

Drug induced lung diseases (DILD) are an increasing cause of morbidity. Many drugs have been described, causing several patterns of injury. Sirolimus is an immunosuppressive agent increasingly used in renal and other solid organ transplantation. Pulmonary toxicity has been recognised as a potential complication associated to this medication. Interstitial pneumonitis and more rarely alveolar haemorrhage have been described. The authors describe 4 cases (3 men and 1 woman) between 46-71 years, transplanted three years ago (1 patient) and 7 years ago (3 patients). All of them were medicated with micofenolato mofetil, prednisone and sirolimus. All patients had fever at admission, 3 patients had dyspnoea and 2 productive cough. Diffuse pulmonary infiltrates with basal predominance in HRCT scan were present in the four patients. BAL showed lymphocytic alveolitis in 3 cases, however with a different CD4/CD8 ratio. In addition to lymphocytosis, neutrophilia was observed in 2 patients. One patient showed serious alveolar haemorrhage in BAL. Pulmonary infections were ruled out by specific BAL staining and cultures. After drug suspension, all patients showed a clear improvement. These case studies show some diversity in clinical presentation and in the features of some exams, namely in BAL. This may suggest different underlying pathophysiology entities induced by sirolimus.