Azithromycin Reverses Airflow Obstruction in Established Bronchiolitis Obliterans Syndrome

    William Leech Centre for Lung Research, The Freeman Hospital, High Heaton, Newcastle upon Tyne, United Kingdom

    ABSTRACT

    Introduction: A recent pilot study noted clinical benefit of macrolide therapy in the management of six lung transplant recipients with bronchiolitis obliterans syndrome (BOS), a condition previously regarded as irreversible. Objective: To examine the effect of low-dose macrolides on lung function in lung allograft recipients with established BOS and to assess whether this benefit is sustained. Methods: We retrospectively evaluated the effect of azithromycin (250 mg alternate days) on clinical status and lung function in 20 allograft recipients with established BOS, confirmed by decline in FEV1 or FEF25eC75; consistent high-resolution computed tomography findings; and exclusion of acute rejection, infection, or anastomatic complications. Azithromycin was introduced at mean 82 months after transplantation. BOS staging at initiation of treatment was BOS 3 (10), BOS 2 (2), BOS 1 (6), and BOS0-p (2). All patients were on maintenance immunosuppression comprising cell-cycle inhibitor, oral corticosteroids, and calcineurin inhibitor. Results: There was a significant increase in FEV1 of median 110 ml (range, eC70 to 730 ml) between baseline and 3 months of azithromycin therapy (p = 0.002). This improvement was sustained beyond 3 months in the majority of patients, who had initially benefited from azithromycin (up to 11 months follow up). Conclusions: This case series confirms the benefit of azithromycin in not only halting, but reversing the declining lung function seen in patients with BOS. This benefit appears to be maintained over time. Low-dose macrolides offer a new and exciting therapeutic strategy for the treatment of progressive BOS, and further clinical and translational mechanistic studies are required.

    Key Words: lung  macrolide  transplantation

    Lung transplantation has evolved to become an accepted strategy in the management of advanced disease in selected patients (1). Unfortunately, although there has been considerable improvement in early outcomes after lung transplantation as a result of advances in surgical techniques and better perioperative management, long-term survival remains limited by the development of bronchiolitis obliterans syndrome (BOS).

    The histologic lesion of BOS is obliterative bronchiolitis (OB). This is characterized by epithelial cell activation as a result of alloimmune and nonalloimmune mechanisms. An early feature is peribronchiolar leukocyte infiltration leading to an abnormal, exaggerated repair response, fibroproliferation, and eventual obliteration of the small airways (2eC9). This leads to deteriorating graft function that is characterized by the development of progressive, irreversible small airway narrowing, fixed airflow limitation, progressive dyspnea, and ultimately, premature death (1, 10, 11). International Registry data shows a 50% prevalence of BOS at 5 years after transplant. This is associated with a reduction in quality of life and increased morbidity and mortality, limiting 7-year mean survival to only 31% (12).

    The current classification of BOS is based on changes in FEV1, with the maximum post-transplant FEV1 being assigned a 100% predicted value (the mean of the two best postoperative FEV1 values with at least 3 weeks between the measurements). Patients experiencing a persistent decline in FEV1 (i.e., two consecutive measurements within 3eC6 weeks) in the absence of acute rejection, infection, or bronchial anastomosis complications are grouped into stages. Additionally, a reduction in FEF25eC75 is used as an early marker for BOS (13).

    Current strategies in the management of BOS have ranged from switching immunosuppressive regimens, augmenting with corticosteroids, and initiating cytolytic therapy. These have had little or no impact on the progression of the condition. Although we have recently demonstrated that total lymphoid irradiation (TLI) significantly reduces the rate of decline in graft function associated with BOS, it fails to halt its progression and may have significant morbidity (14). Significantly, data from ex vivo experiments indicate that many of the traditional agents used may upregulate proinflammatory cytokines and growth factors, with a potentially detrimental effect on allografts (15eC19).

    There has been recent interest in the potential role of macrolide antibiotics in the management of BOS. Macrolides have demonstrated antiinflammatory properties in other respiratory conditions such as asthma, cystic fibrosis, and diffuse panbronchiolitis (15eC26). Notably, in a recent pilot study, Gerhardt and coworkers described a significant, short-term improvement (mean follow-up of 14 weeks) in lung function in six lung transplant recipients with BOS who were treated with azithromycin (27). These promising data have been confirmed by Verleden and colleagues in eight further subjects with short-term follow-up (28). In this article we examine the effect of low-dose maintenance azithromycin therapy in 20 patients with BOS, followed for up to 48 weeks. This study has previously been partially presented at The International Society for Heart and Lung Transplantation and The American Thoracic Society annual meetings, with publication in abstract form (29, 30).

    METHODS

    Study Subjects

    Twenty lung transplant recipients with a diagnosis of BOS (n = 18) or BOS0-p (n = 2) were placed on maintenance azithromycin. A diagnosis of BOS was assigned on the basis of the International Society for Heart and Lung Transplantation criteria (13). Patients displayed no clinical evidence of infection, acute rejection, or other cause for their deterioration in lung function. All patients meeting these criteria for BOS were consecutively treated with azithromycin. The data presented in this paper were retrospectively collected and are presented in a case series format.

    Treatment Regimen

    All patients were treated with oral azithromycin at a dose of 250 mg alternate days from the time of BOS diagnosis to preparation of this manuscript. Patients were regularly evaluated at clinic with pulmonary function testing to assess response. Liver function was monitored at regular intervals without any adverse effect of therapy. All patients remained on immunosuppressive therapy comprising a calcineurin inhibitor (cyclosporin or tacrolimus), oral corticosteroids, and a purine antagonist (azathioprine or mycophenolate mofetil). The standard immunosuppression regimen used at our facility is a triple therapy approach of cyclosporin, prednisolone, and azathioprine. In this study two patients were on tacrolimus and one on mycophenolate. Azithromycin was commenced at varying time points. Immunosuppressant levels were not affected by azithromycin therapy in our patient cohort. During the treatment phase, one patient required antibiotic treatment for infection (Patient 15, Table 1) and one patient was switched to mycophenolate (Patient 17, Table 1). Mean follow-up is 6.25 months (range, 3eC11 months).

    Statistical Analysis

    Patients had variable times of follow-up, and spirometry was performed at various time points. Analysis was performed using nonparametric methods (Minitab, release 14 for Windows; State College, PA) and post-treatment data grouped into 3-month blocks and compared with baseline values. Baseline refers to spirometry measurements performed at the initiation of treatment. Spirometry measurements were performed at 3 (2eC4 months), 6 (5eC7 months), and 9 (8eC10) months.

    RESULTS

    Patient characteristics and responses are shown in Table 1 and Figure 1. Our study population consisted of 10 males and 10 females. The underlying diagnoses were cystic fibrosis (n = 6), emphysema (n = 5), 1-antitrypsin deficiency (n = 1), bronchiectesis (n = 2), sarcoidosis (n = 2), pulmonary hypertension (n = 2), and retransplantation for obliterative bronchiolitis (n = 2). There were nine bilateral lung transplants, eight single lung transplants, and three heart-lung transplants. The mean age at transplantation was 38 (range, 17eC59 years), with an average postoperative FEV1 = 2.86 L (range, 1.16eC5.01). The average number of acute rejection episodes (Grade A2 or greater) was 1.55, before BOS.

    BOS stages at initiation of treatment were BOS 3 (n = 10), BOS 2 (n = 2), BOS 1 (n = 6), and BOS0-p (n = 2). Mean follow-up at time of manuscript preparation has been 6.25 months (range, 3eC11 months). There was a significant but variable improvement in FEV1 of mean 110 ml (range, eC70 to 730 ml) between baseline and after 3 months of azithromycin therapy (Figure 1, p = 0.002). This improvement was sustained beyond 3 months in 12 of 17 patients (up to 11 months follow-up). Figure 1 shows percentage change in FEV1 from baseline.

    DISCUSSION

    We have confirmed the recent studies of Gerhardt and coworkers (27) and Verleden and colleagues (28), and have shown that azithromycin therapy can successfully treat BOS, a condition refractory to previous clinical management. We have extended the current literature by performing our study in a bigger patient group, with longer-term follow-up.

    These findings are remarkable in that they offer hope in arresting the progression of BOS. There was median gain in lung function of 110 ml for the group, and in one patient a 730-ml increase was observed. There were no side effects of therapy reported by our patients, and no patient has discontinued therapy to date. This benefit profile is unprecedented in our program.

    The mechanism of action of macrolides in BOS is not known, but is not likely to be due to a direct microbicidal action, because of the low doses used. Similar dosing regimens demonstrate clinical improvement, efficacy, improved lung function, and antiinflammatory properties in patients with asthma, cystic fibrosis, and panbronchiolitis (20eC26). Several mechanisms have been proposed to explain these effects, including suppression of inflammatory mediators and neutrophilic infiltration (31, 32), inhibition of airway remodeling through suppression of matrix metalloproteinases (33), and modulation of the effects of low-grade Pseudomonas infection (34, 35).

    Long-term low-dose azithromycin therapy offers a novel, safe, and exciting therapy for the treatment of progressive BOS, and our data confirm the beneficial effects in not only preventing a further decline in lung function, but leading to a variable level of improvement in lung function in a majority of patients with established BOS. The fact that airflow limitation regarded as "fixed" has been reversed implies that structural changes have occurred. In preliminary findings from the heterotopic tracheal allograft animal model of lung transplantation, macrolide premedication has been shown to inhibit pathologic airway fibrosis (36).

    Our study is limited by the small patient cohort and is a descriptive case series rather than a randomized, placebo-controlled study. Hence, our findings, although extremely promising, need to be interpreted with caution. The magnitude of the treatment effect we observed suggests that a formal randomized placebo-controlled trial may be feasible. Further clinical and translational mechanistic studies of the effects of macrolide therapy in BOS are now required.

    This research was funded by the Newcastle upon Tyne Hospitals Special Trustees, European Respiratory Society Fellowships (D.M.M., C.W.), Medical Research Council Fellowship (I.A.F.), and the McPhail Trust (J.L.L.).

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