Greater survival despite increased complication rates following lung transplant for alpha-1-antitrypsin deficiency compared to chronic obstructive pulmonary disease

Lung transplantation for COPD/pulmonary emphysema

COPD and α-1 antitrypsin deficiency emphysema remain one of the major indications for lung transplantation. If all other treatment possibilities are exhausted or not possible (including rehabilitation, oxygen therapy, noninvasive ventilation, lung volume reduction), patients may qualify for lung transplantation. Strict selection criteria are implemented with a lot of relative and absolute contraindications. Because of an ongoing donor shortage, only a minority of endstage COPD patients will finally get transplanted. The procedure may involve a single or a double lung transplantation, dependent on the experience of the centre, the waiting list, the availability of donor lungs and the patient's risk-benefit ratio. In general, the life expectancy as well as the health-related quality of life after lung transplantation for COPD are usually increased, and may be somewhat better after double compared with single lung transplantation. Several specific complications can be encountered, such as the development of solid organ cancer and chronic lung allograft dysfunction, which develops in up to 50% of patients within 5 years of their transplant and has a major impact on long-term survival, because of the current inefficient treatment modalities.

Alpha-1 antitrypsin deficiency: current therapy and emerging targets

INTRODUCTION

Alpha1 antitrypsin deficiency (AATD), a common hereditary disorder affecting mainly lungs, liver and skin has been the focus of some of the most exciting therapeutic approaches in medicine in the past 5 years. In this review, we discuss the therapies presently available for the different manifestations of AATD and new therapies in the pipeline.

AREAS COVERED

We review therapeutic options for the individual lung, liver and skin manifestations of AATD along with approaches which aim to treat all three. Along with this renewed interest in treating AATD come challenges. How is AAT best delivered to the lung? What is the desired level of AAT in the circulation and lungs which therapeutics should aim to provide? Will treating the liver disease increase the potential for lung disease? Are there treatments to target the underlying genetic defect with the potential to prevent all aspects of AATDrelated disease?

EXPERT OPINION

With a relatively small population able to participate in clinical studies, increased awareness and diagnosis of AATD is urgently needed. Better, more sensitive clinical parameters will assist in the generation of acceptable and robust evidence of therapeutic effect for current and emerging treatments.

Prevalence of Clinical COPD Phenotypes in Patients Who Are Candidates for Lung Transplantation, Complications and Post-Transplant Survival

Introduction

The prevalence of COPD phenotypes that are referred for assessment for lung transplantation is unknown, as well as whether specific phenotype influences post-transplant evolution in those patients who receive it.

Material and methods

Ambispective observational study without intervention. The main objective was to know the prevalence of the different COPD phenotypes of the patients referred for the evaluation of a lung transplant. Secondary objective were to compare their clinical characteristics, to perform an analysis of post-transplant survival or complications according to their phenotype.

Results

502 patients were evaluated for lung transplantation, of which 173 met the study criteria. 31.21% of the patients were discarded for transplantation on a first visit. The final cohort of potential transplant candidates who completed the pre-transplant study was 119 (69%) and 47 finally received a lung transplant (39.5%). The most frequent COPD phenotype evaluated for lung transplantation was the exacerbator (59%), followed by the non-exacerbator (38%) and the Asthma COPD Overlap [ACO] (3%). 59.8% of the exacerbator-phenotype patients assessed did not complete the pre-transplant study. Exacerbator-phenotype patients have a lower post-transplant survival (1115.1 days [standard deviation-DE-587]) vs. ACO: 1432 days [DE 507.5] and Non-exacerbators: 1317.8 days [DE 544.7] p = 0.16), although this difference has not been statistically significant.

Conclusions

The most frequent COPD phenotype assessed for lung transplantation is the exacerbator, although more than half of these patients fail to complete the pre-transplant study.

Lung and liver transplantation in patients with alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin (AAT) augmentation is effective in slowing the progression of emphysema due to AAT deficiency (AATD) but cannot prevent eventual progression to end-stage lung disease and complete respiratory failure, which is the leading cause of death for individuals with severe AATD. When patients develop end-stage lung disease, lung transplantation is the only treatment option available, and this can improve lung physiology and patient health status. The available data suggest that survival rates for lung transplantation are significantly higher for patients with AATD-related chronic obstructive pulmonary disease (COPD) compared with non-AATD-related COPD, but, conversely, there is a higher risk of common post-lung transplant complications in patients with AATD versus non-AATD COPD. Nevertheless, lung transplantation (single and bilateral) is favorable for patients with AATD. After respiratory failure, the second leading cause of death in patients with AATD is liver disease, for example, cirrhosis and hepatocellular carcinoma, caused by the accumulation of mutant forms of AAT retained within the liver. As with lung disease, the only treatment option for end-stage liver disease is liver transplantation. Survival rates for patients with AATD undergoing liver transplantation are also favorable, and patients, particularly pediatric patients, have benefitted from advancements in peri-/post-surgical care. As the majority of AAT is produced by the liver, the AAT phenotype of the recipient becomes that of the donor, meaning that AAT serum levels should be normalized (if the donor is AAT-replete), halting further lung and liver disease progression. However, post-liver transplant respiratory function may continue to decline in line with normal age-related lung function decline. In the most severe cases, where patients have simultaneous end-stage lung and liver disease, combined lung and liver transplantation is a treatment option with favorable outcomes. However, there is very little information available on this procedure in patients with AATD.

Clinical outcomes and survival following lung transplantation in patients with Alpha-1 antitrypsin deficiency

OBJECTIVE

The primary intention of our study is to describe disease-specific outcomes in patients with alpha-1 antitrypsin deficiency (AATD) following lung transplantation (LT).

METHODS

We reviewed the Organ Procurement and Transplant Network database to identify AATD patients who have undergone LT in the United States.

RESULTS

Two thousand two hundred and thirteen patients with AATD underwent LT between March 1992 and September 2019. A total of 1556 patients received LT with a median age at listing was 51 years. The median time spent on the LT waitlist was 263 days. The median ischemic time was 4.75 h. The Kaplan-Meier survival analysis following LT for AATD patients at 1-, 5-, and 10 years was 82%, 56%, and 34%, at 1-, 5-, and 10 years, respectively. The median survival time post-LT is 6.4 years (Interquartile range 5.6-6.8 years). The post-LT survival was significantly better in double LT compared to single LT (Median 7.7 vs 4.4 years, p < 0.001). Increasing age, presence of CMV mismatch, reintubation prior to discharge, and requiring treatment for rejection within one year of transplantation did impact post-LT mortality.

CONCLUSION

The median survival after LT in AATD is 6.4 years and is similar to other lung diseases. When compared to usual COPD LT, AATD patients have increased post-LT mortality due to infections and liver disease. Recipients of a double lung transplant had a favorable outcome compared to single lung transplant.

α1 Antitrypsin therapy modulates the neutrophil membrane proteome and secretome

Obstructive pulmonary disease in patients with α₁ antitrypsin (AAT) deficiency (AATD) occurs earlier in life compared with patients without AATD. To understand this further, the aim of this study was to investigate whether AATD presents with altered neutrophil characteristics, due to the specific lack of plasma AAT, compared with non-AATD COPD.This study focussed on the neutrophil plasma membrane and, by use of label-free tandem mass spectrometry, the proteome of the neutrophil membrane was compared in forced expiratory volume in 1 s (FEV₁)-matched AATD, non-AATD COPD and in AATD patients receiving weekly AAT augmentation therapy (n=6 patients per cohort). Altered protein expression in AATD was confirmed by Western blot, ELISA and fluorescence resonance energy transfer analysis.The neutrophil membrane proteome in AATD differed significantly from that of COPD as demonstrated by increased abundance and activity of primary granule proteins including neutrophil elastase on the cell surface in AATD. The signalling mechanism underlying increased degranulation involved Rac2 activation, subsequently resulting in proteinase-activated receptor 2 activation by serine proteinases and enhanced reactive oxygen species production. In vitro and ex vivo, AAT reduced primary granule release and the described plasma membrane variance was resolved post-AAT augmentation therapy in vivo, the effects of which significantly altered the AATD neutrophil membrane proteome to that of a non-AATD COPD cell.These results provide strong insight into the mechanism of neutrophil driven airways disease associated with AATD. Therapeutic AAT augmentation modified the membrane proteome to that of a typical COPD cell, with implications for clinical practice.