Antifibrotic drugs in lung transplantation and chronic lung allograft dysfunction: a review

Chronic Lung Allograft Dysfunction: Clinical Manifestations and Immunologic Mechanisms

The term "chronic lung allograft dysfunction" has emerged to describe the clinical syndrome of progressive, largely irreversible dysfunction of pulmonary allografts. This umbrella term comprises 2 major clinical phenotypes: bronchiolitis obliterans syndrome and restrictive allograft syndrome. Here, we discuss the clinical manifestations, diagnostic challenges, and potential therapeutic avenues to address this major barrier to improved long-term outcomes. In addition, we review the immunologic mechanisms thought to propagate each phenotype of chronic lung allograft dysfunction, discuss the various models used to study this process, describe potential therapeutic targets, and identify key unknowns that must be evaluated by future research strategies.

Pharmacokinetics and safety of pirfenidone in individuals with chronic kidney disease stage G2 and G3a: A single-dose, Phase I, bridging study

BACKGROUND AND OBJECTIVE

Pirfenidone is an inhibitor of transforming growth factor-beta 1 (TGF-β1) and is being developed for the treatment of diabetic kidney disease (DKD). We assessed the pharmacokinetics (PK) and safety of a single dose of pirfenidone in individuals with CKD stages G2/G3a.

METHODS

In this phase I bridging study, patients with CKD stages G2 or G3a, aged 18-70 years, with a body mass index of 18-26 kg/m2, and glomerular filtration rate (eGFR) ranging from 45 to 89 ml/min/1.73 m2, received a single oral dose of 400 mg pirfenidone capsules 30 min after a standard breakfast. The pharmacokinetic parameters of the two groups were measured and compared after blood and urine collection. The co-primary endpoints were the area under the plasma concentration-time curve from time zero to 36 h (AUC0-36) and the maximum observed plasma concentration (Cmax) of pirfenidone. Safety was a secondary endpoint. The trial has been registered on ClinicalTrials.gov (ChiCTR2300077297).

RESULTS

A total of 20 subjects participated in this study. There were no significant differences between the control group and the patient group (CKD stages G2/G3a) in terms of plasma Cmax, the time to reach the maximum observed concentration (Tmax), and elimination half-life(t1/2). However, the Vz/F of the patient group (CKD G2 stage) was significantly higher than that of the control group. Renal accumulation rate, renal clearance rate (CLr), and urine drug concentration also showed no significant differences. No severe adverse events occurred during the trial.

CONCLUSIONS

These results indicate that the PK and safety of pirfenidone are not influenced by renal function. Individuals with renal impairment may not require dose adjustments.

Time to Rethink Bronchiolitis Obliterans Syndrome Following Lung or Hematopoietic Cell Transplantation in Pediatric Patients

Background: Similar in histological characteristics and clinical manifestations, bronchiolitis obliterans syndrome (BOS) can develop following lung transplantation (LTx) or hematopoietic cell transplantation (HCT). In contrast to lung transplantation, where BOS is restricted to the lung allograft, HCT-related systemic graft-versus-host disease (GVHD) is the root cause of BOS. Because lung function declines following HCT, diagnosis becomes more difficult. Given the lack of proven effective medicines, treatment is based on empirical evidence. Methods: Cross-disciplinary learning is crucial, and novel therapies are under investigation to improve survival and avoid LTx. Recent advances have focused on updating the understanding of the etiology, clinical features, and pathobiology of BOS. It emphasizes the significance of learning from experts in other transplant modalities, promoting cross-disciplinary knowledge. Results: Our treatment algorithms are derived from extensive research and expert clinical input. It is important to ensure that immunosuppression is optimized and that any other conditions or contributing factors are addressed, if possible. Clear treatment algorithms are provided for each condition, drawing from the published literature and consensus clinical opinion. There are several novel therapies currently being investigated, such as aerosolized liposomal cyclosporine, Janus kinase inhibitors, antifibrotic therapies, and B-cell-directed therapies. Conclusions: We urgently need innovative treatments that can greatly increase survival rates and eliminate the need for LTx or re-transplantation.

Identification and validation of potential biomarkers related to oxidative stress in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrotic interstitial pneumonia with a poor prognosis and a pathogenesis that has not been fully elucidated. Oxidative stress is closely associated with IPF. In this research, we aimed to identify reliable diagnostic biomarkers associated with the oxidative stress through bioinformatics techniques. The gene expression profile data from the GSE70866 dataset was retrieved from the gene expression omnibus (GEO) database. We extracted 437 oxidative stress-related genes (ORGs) from gene set enrichment analysis (GSEA). The GSE141939 dataset was used for single-cell RNA-seq analysis to identify the expression of diagnostic genes in different cell clusters. A total of 10 differentially expressed oxidative stress-related genes (DE-ORGs) were screened. Subsequently, SOD3, CD36, ACOX2, RBM11, CYP1B1, SNCA, and MPO from the 10 DE-ORGs were identified as diagnostic genes based on random forest algorithm with randomized least absolute shrinkage and selection operator (LASSO) regression. A nomogram was constructed to evaluate the risk of disease. The decision curve analysis (DCA) and clinical impact curves indicated that the nomogram based on these seven biomarkers had extraordinary predictive power. Immune cell infiltration analysis results revealed that DE-ORGs were closely related to various immune cells, especially CYP1B1 was in positive correlation with monocytes and negative correlation with macrophages M1. Single-cell RNA-seq analysis showed that CYP1B1 was mainly associated with macrophages, and SNCA was mainly associated with basal cells. CYP1B1 and SNCA were diagnostic genes associated with oxidative stress in IPF.

Pulmonary epithelial markers in phenotypes of chronic lung allograft dysfunction

BACKGROUND

Airway epithelial injury is thought to be a key event in the pathogenesis of chronic lung allograft dysfunction (CLAD). We investigated whether markers of epithelial activity and injury in bronchoalveolar lavage fluid (BAL) correlate with CLAD diagnosis and major CLAD phenotypes: bronchiolitis obliterans syndrome (BOS) vs restrictive allograft syndrome (RAS)-related phenotypes (including RAS, mixed phenotype, and all other patients with RAS-like opacities).

METHODS

CLAD status and phenotypes were retrospectively determined in a cohort of all consecutive adult, first, bilateral lung transplants performed 2010-2015, with available BAL samples. All patients with RAS-related phenotypes were included and 1:1 matched with BOS patients based on the time from transplant to CLAD-onset. Subjects who were CLAD-free for a minimum of 3 years post-transplant were 1:1 matched to CLAD patients and included as controls. Proteins that maintain the barrier function of the airway epithelial mucosa (club cell secretory protein, surfactant protein-D and epithelial mucins: MUC1, MUC5AC, MUC5B, MUC16), as well as epithelial cell death markers (M30&M65 representing epithelial cell apoptosis and overall death, respectively), were measured in BAL obtained within 6-months post CLAD onset using a double-sandwich ELISA or a multiplex bead assay. Protein levels were compared using Mann-Whitney-U-test. Association between protein levels and graft survival was assessed using Cox proportional hazards models, adjusted for CMV serology mismatch status and CLAD phenotype.

RESULTS

Fifty-four CLAD (27 BOS, 11 RAS, 7 mixed, 9 others with RAS-like opacities) patients and 23 CLAD-free controls were included. Median BAL levels were significantly higher in patients with CLAD compared to CLAD-free controls for M30 (124.5 vs 88.7 U/L), MUC1 (6.8 vs 3.2 pg/mL), and MUC16 (121.0 vs 30.1 pg/mL). When comparing CLAD phenotypes, M30 was significantly higher in patients with RAS-related phenotypes than BOS (160.9 vs 114.6 U/L). In multivariable models, higher M30 and MUC5B levels were associated with decreased allograft survival after CLAD onset independent of phenotype (p < 0.05 for all).

CONCLUSIONS

Airway epithelial mucins and cell death markers are enhanced in the BAL of patients with CLAD and can assist in differentiating between CLAD phenotypes and post-CLAD outcomes. Abnormal airway mucin expression and epithelial cell death may be involved in the pathogenesis of CLAD, and therefore their detection may aid in future selection of targeted therapies.

Impact of ILD-Specific Therapies on Perioperative Course in Patients with Progressive Interstitial Lung Disease Undergoing Lung Transplantation

Immunosuppressants and antifibrotics are currently used to treat patients with various interstitial lung diseases, which may undergo lung transplantation (LTx). The retrospective study aimed to evaluate the potential effects of therapeutic regimen on the perioperative course in patients with idiopathic pulmonary fibrosis (IPF) or progressive pulmonary fibrosis (PPF) undergoing LTx. All patients with IPF and PPF undergoing LTx between January 2014 and December 2021 were included. We retrospectively screened for previous use of immunosuppressants and antifibrotic therapy. We analyzed perioperative courses, short-term outcomes, and safety retrospectively. In total, 286 patients with diagnosis of IPF or PPF were analyzed. According to the treatment regimen before LTx, the study cohort was divided into four groups and compared. No differences between antifibrotic monotherapy, combined antifibrotic and immunosuppressive therapy with regard to postoperative complications were observed. Length of mechanical ventilation was shorter in patients with antifibrotics prior to LTx. Pretreatment with antifibrotic monotherapy and a combination of antifibrotic drugs with immunosuppressive therapy, lower body mass index (BMI) and lower blood loss, were independently associated with primary graft dysfunction grades 0-3 72 hours after LTx (p < 0.001). Finally, patients with antifibrotic monotherapy developed significantly less de novo donor-specific antibodies (DSA) (p = 0.009). Higher intraoperative blood loss, etiology of interstitial lung disease (ILD) and older age were independently associated with shorter survival after LTx. Use of antifibrotic monotherapy and a combination of antifibrotic drugs with immunosuppressive therapy in IPF/PPF patients undergoing LTx, proved to be safe and might lead to beneficial effects after LTx.

Lung transplantation for interstitial lung disease: evolution over three decades

BACKGROUND

Interstitial lung disease (ILD) has emerged as the most common indication for lung transplantation globally. However, post-transplant survival varies depending on the underlying disease phenotype and comorbidities. This study aimed to describe the demographics, disease classification, outcomes and factors associated with post-transplant survival in a large single-centre cohort.

METHODS

Data were retrospectively assessed for 284 recipients who underwent lung transplantation for ILD in our centre between 1987 and 2020. Patient characteristics and outcomes were stratified by three eras: 1987-2000, 2001-2010 and 2011-2020.

RESULTS

Median patients' age at time of transplantation was significantly higher in the most recent decade (56 (51-61) years, p<0.0001). Recipients aged over 50 years had worse overall survival compared with younger patients (adjusted HR, aHR 2.36, 95% CI 1.55 to 3.72, p=0.0001). Better survival was seen with bilateral versus single lung transplantation in patients younger than 50 years (log-rank p=0.0195). However, this survival benefit was no longer present in patients aged over 50 years. Reduced survival was observed in fibrotic non-specific interstitial pneumonia compared with idiopathic pulmonary fibrosis, which remained the most common indication throughout (aHR 2.61, 95% CI 1.40 to 4.60, p=0.0015).

CONCLUSION

In patients transplanted for end-stage ILD, older age and fibrotic non-specific interstitial pneumonia were associated with poorer post-transplant survival. The benefit of bilateral over single lung transplantation diminished with increasing age, suggesting that single lung transplantation might still be a feasible option in older candidates.

Diagnostic performance of electronic nose technology in chronic lung allograft dysfunction

BACKGROUND

There is a need for reliable biomarkers for the diagnosis of chronic lung allograft dysfunction (CLAD). In this light, we investigated the diagnostic value of exhaled breath analysis using an electronic nose (eNose) for CLAD, CLAD phenotype, and CLAD stage in lung transplant recipients (LTR).

METHODS

We performed eNose measurements in LTR with and without CLAD, visiting the outpatient clinic. Through supervised machine learning, the diagnostic value of eNose for CLAD was assessed in a random training and validation set. Next, we investigated the diagnostic value of the eNose measurements combined with known risk factors for CLAD. Model performance was evaluated using ROC-analysis.

RESULTS

We included 152 LTR (median age 60 years, 49% females), of whom 38 with CLAD. eNose-based classification of patients with and without CLAD provided an AUC of 0.86 in the training set, and 0.82 in the validation set. After adding established risk factors for CLAD (age, gender, type of transplantation, time after transplantation and prior occurrence of acute cellular rejection) to a model with the eNose data, the discriminative ability of the model improved to an AUC of 0.94 (p = 0.02) in the training set and 0.94 (p = 0.04) in the validation set. Discrimination between BOS and RAS was good (AUC 0.95). Discriminative ability for other phenotypes (AUCs ranging 0.50-0.92) or CLAD stages (AUC 0.56) was limited.

CONCLUSION

Exhaled breath analysis using eNose is a promising novel biomarker for enabling diagnosis and phenotyping CLAD. eNose technology could be a valuable addition to the diagnostic armamentarium for suspected graft failure in LTR.

Antifibrotics and lung transplantation: A Spanish multicentre case-controlled study

BACKGROUND AND OBJECTIVE

Antifibrotic drugs are the standard treatments for patients with idiopathic pulmonary fibrosis (IPF). This study aims to assess the safety of antifibrotic treatment in IPF patients undergoing lung transplantation.

METHODS

Patients with a diagnosis of IPF who received a lung transplant between January 2015 and June 2019 at four Spanish hospitals specialized in lung transplantation were retrospectively recruited. Cases were defined as patients receiving antifibrotic treatments at time of transplant. Each case was matched with a control who did not receive antifibrotic treatment.

RESULTS

A total of 164 patients were included in the study cohort (103 cases and 61 controls). There were no statistically significant differences between the cases and controls in any of the items studied related to transplantation except the time until the appearance of chest wall dehiscence: although there were no differences in the incidence of wall dehiscence in either group (12.3% vs. 13.7%; p = 0.318), the patients on antifibrotic drugs experienced it earlier (21 days [IQR = 12.5-41.5] vs. 63 days [IQR = 46.75-152.25]; p = 0.012). There were no differences in overall post-transplant survival between the two groups (p = 0.698) or in conditional survival at 30 days, 90 days, 3 years or 5 years. However, 1 year survival was significantly greater among controls (80.6% vs. 93.3%; p = 0.028).

CONCLUSION

There was evidence that chest wall dehiscences appeared earlier post-transplant in patients using antifibrotics, even though this factor did not significantly impact survival.