Randomized, Open-label, Multi-Center Study Comparing Tacrolimus With Cyclosporin, Both Arms in Combination With Mycophenolate Mofetil and Corticosteroids for Prevention of Bronchiolitis Obliterans Syndrome in Lung Transplant Patients

Lung transplantation has become a viable treatment option for selected patients with end stage lung disease and leads to prolonged survival and improved quality of life. However, despite improvements in surgical techniques, immunosuppressive therapies and long-term care, survival rates reported by the Registry of the International Society for Heart and Lung Transplantation (ISHLT) (79% 1-year and 52% 5-year) are lower than those reported for other solid organ transplants. The leading cause of death in long-term follow-up after lung transplantation is chronic allograft dysfunction due to obliterative bronchiolitis (OB) manifested by its physiological correlate the bronchiolitis obliterans syndrome (BOS). OB is thought to result from chronic rejection leading to obliteration and scarring of the terminal bronchioles which causes a significant reduction in pulmonary function parameters, most specifically the forced expiratory volume in 1 second (FEV1). In the absence of confounding variables, lung transplant recipients are considered to suffer from BOS grade ≥1 if they experience a sustained (>3 weeks) ≥ 20% decline in FEV1 from a baseline of the average of the two best FEV1 measurements obtained at least 3 weeks apart.

Most immunosuppressive regimens after lung transplantation are based on calcineurin inhibitors. The introduction of cyclosporine was responsible for the initial success of lung transplantation in the early 1980s as it allowed the use of a lower dose of corticosteroids and hence afforded superior wound healing. Its chief mechanism of action is the blockade of T-lymphocyte activation by inhibiting interleukin-2 (IL 2) synthesis. Tacrolimus is a macrolide lactone that was introduced in the 1990s and is now widely accepted as an alternative to cyclosporine. Mechanisms of action and toxicities of tacrolimus and cyclosporine are similar, and tacrolimus has proven to be at least as effective as cyclosporine in solid organ transplantation including lung transplantation. Tacrolimus is approximately 50 times more potent than cyclosporine and has proven to be an effective rescue agent for patients with either recurrent or refractory acute allograft rejection. Whether denovo tacrolimus use can reduce the incidence of BOS when compared with cyclosporine after lung transplantation remains unclear. To date there are no published adequately powered randomized controlled trials in lung transplantation which compare the efficacy and safety of the calcineurin inhibitors cyclosporine and tacrolimus for primary immunosuppression.

The investigators therefore conducted a randomized, open-label, multi-center, investigator driven trial comparing tacrolimus with cyclosporine - both arms in combination with mycophenolate mofetil (MMF) and prednisolone for the prevention of BOS in lung and heart-lung transplant recipients.

The investigators chose to partner the calcineurin inhibitor with MMF instead of azathioprine. MMF is an ester prodrug of mycophenolic acid (MPA), a potent and specific inhibitor of de novo purine synthesis which blocks the proliferation of both T and B lymphocytes. The potential superiority of MMF over its comparator azathioprine after lung transplantation has been suggested in small and nonrandomized studies. However, large randomized trials in renal and heart transplantation have demonstrated the greater efficacy of MMF for preventing acute allograft rejection when compared with azathioprine.

The study protocol was accepted by each local hospital research ethics committee. All patients provided written informed consent and were free to withdraw from the study at any time point. The trial was proposed and designed by a steering committee consisting of members of the study group, The European and Australian Investigators in Lung Transplantation (EAILTx), representing experienced lung transplant centers from Australia, Austria, Belgium, Germany, Spain and Switzerland.