Early onset of azithromycin to prevent CLAD in lung transplantation: Promising results of a retrospective single centre experience

Azithromycin (AZI) may be an effective immune modulator in lung transplant (LT) recipients, and can decrease chronic lung allograft dysfunction (CLAD) rates, the leading cause of mortality after the 1st year post‐LT. The aim of the study is to assess the effect of AZI initiation and its timing on the incidence and severity of CLAD in LT recipients.


INTRODUCTION
Lung transplantation (LT) is a well-established treatment option for patients with advanced respiratory diseases in whom all available treatment options have been optimized. 1  phenotype. 3 This classification has significant prognostic implications, as BOS, which is the most frequent phenotype, has a better prognosis than RAS. 4 There are multiple known risk factors for the onset of CLAD, both immune-mediated and non-immune-mediated. Although some of the common pathophysiological pathways that lead to the changes in pulmonary architecture are known, the mechanisms explaining why BOS predominates in some patients and RAS in others remain undetermined. 5 To date, no fully effective treatment for CLAD is known. However, several therapies have shown promise to slow the loss of lung function, including methotrexate, total lymphoid irradiation, extracorporeal photopheresis, thymoglobulin, montelukast, and more recently, antifibrotics, such as nintedanib or pirfenidone. [6][7][8][9][10][11][12][13][14][15] Azithromycin, a macrolide antibiotic that inhibits bacterial protein synthesis and reduces biofilm formation, is the most widely used and studied treatment for CLAD. In addition to its antibiotic properties in different infections, it has proven to be helpful as an anti-inflammatory and immunomodulator in different chronic inflammatory respiratory, dermatological, and genitourinary disorders with a predominantly neutrophilic inflammatory response. 16,17 Because neutrophilic airway inflammation is an essential non-alloimmune mediator in the onset of CLAD, azithromycin was introduced as a potential treatment of this condition in 2003. 18   There were two independent evaluators to determine the diagnosis of CLAD, and these evaluators were blinded of each patient's azithromycin group. Disagreements in CLAD onset were resolved by consensus between the two investigators who made the CLAD diagnoses with a third investigator keeping the blind.
According to our center's protocol, a bronchoscopy with transbronchial biopsy is performed in all patients approximately 2-3 weeks after LT. As per protocol, a transbronchial biopsy is not performed during the subsequent follow-up, and the conduct of this procedure is limited to those cases in which there is a clinical, radiological, or functional suspicion of acute rejection.
In case of an acute cellular rejection ≥A2 according to ISHLT Working Formulation, high-dose methylprednisolone treatment is administered at a dosage of 10-15 mg/kg/day for 3 days, followed by a subsequent tapered corticosteroid regimen, and a new follow-up transbronchial biopsy is repeated around 3-6 weeks later.

Statistical analysis
Software IBM SPSS Statistics 20 was used to perform the statistical analyses. Continuous quantitative variables were expressed as a mean ± standard deviation in the case of those following a normal distribution, and as a median and interquartile range in the case of those not following this type of distribution. On the other hand, categorical variables were expressed as frequencies and percentages.
The Smirnov-Kolmogrov test was used to determine whether or not the continuous quantitative variables followed a normal distribution.
Student's t-test for independent samples was used to analyze differences between a quantitative variable following a normal distribution and a qualitative one. In contrast, Mann-Whitney U test was used to compare quantitative variables not following a normal distribution with qualitative variables. The chi-squared test was used to explore the association between two qualitative variables. A log-rank test was carried out to study the event-free period (onset of CLAD), and the cause-specific Cox proportional hazards model with graft loss/death events right censored was used for both univariable and multivariable analysis by using forward stepwise regression with a threshold of p < .20. In all cases, a p-value ≤.05 was considered to be statistically significant.

RESULTS
From an initial cohort of 393 patients, 358 patients who had been followed for at least six months to establish the diagnosis of CLAD were included in the study. Of these, 64.2% were men and most of them (68.7%) had undergone double lung transplantation. A summary of the population characteristics is included in Table 1. The incidence of CLAD among the patients who started treatment with azithromycin without having a decline in their FEV1 (groups A and B) was significantly lower than among those who did not take azithromycin (group C) (21.5% vs. 33.0%; p = .023).
Patients in group A experienced the fewest episodes of CLAD at the first, third, and fifth-year post-transplant compared with the other groups, followed by groups B, C, and D, respectively (Table 2).
In addition to having a lower incidence of CLAD, patients in group A experienced lower severity of CLAD (only CLAD stages 1 and 2), while those who did not receive azithromycin or those who received it due to a decline in their FEV1 (groups C and D) experienced higher severity of CLAD (stages 3 and 4) ( Table 3; Figure 1).   Figure 2).

DISCUSSION
The sample). 25 The findings of different studies demonstrate how treatment with azithromycin can slow the loss of pulmonary function in LT patients who have already developed CLAD and that early initiation of this drug contributes to preserving pulmonary function compared to those who start the treatment at a later date or who take a placebo. [26][27][28] The use of azithromycin as prophylaxis for CLAD was studied by Vos et al. in a clinical trial whose findings demonstrated a beneficial effect in preventing the onset of CLAD in LT patients. However, no effect on overall survival was found, probably due to the short follow-up period and small sample size. 20 A follow-up of this study was published by Ruttens et al., who demonstrated that the prophylactic use of azithromycin was beneficial in preventing the onset of CLAD without significant associated adverse effects. 21 The use of azithromycin could also be beneficial in preventing the onset of CLAD associated Regarding the treatment's safety, one of the main concerns are the adverse effects associated with the long-term use of azithromycin, as it has been linked to hearing loss, bacterial resistance, arrhythmias, and even deaths of cardiovascular cause. 31,32 However, numerous studies that have already been cited in this paper, in which azithromycin was used in LT patients, did not report significant cardiovascular adverse effects.
Group B patients, who had a preserved FEV1 but started later than the third week post-LT, experienced the second lowest rates of CLAD and lower severity during follow-up.
Regarding acute cellular rejection, acute cellular rejection was the only independent risk factor for CLAD development in multivariate analysis. Patients on azithromycin experienced significantly fewer acute rejections than those who did not receive azithromycin, although this is not a currently known beneficial effect of prophylaxis with this drug. One potential explanation for this effect are the known benefits of azithromycin as an anti-inflammatory and immunomodulator in the airways. 16,33 A recent experience showed that microbiome dysbiosis in LT patients increased the risk of acute cellular rejection episodes, although chronic treatment with azithromycin was not responsible for changes in the composition of this microbiome. 34 Finally, it must be considered that patients in group