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      Alpha-1 proteinase inhibitors for the treatment of alpha-1 antitrypsin deficiency: safety, tolerability, and patient outcomes

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          Abstract

          Alpha-1 antitrypsin (AAT) deficiency remains an underrecognized genetic disease with predominantly pulmonary and hepatic manifestations. AAT is derived primarily from hepatocytes; however, macrophages and neutrophils are secondary sources. As the natural physiological inhibitor of several proteases, most importantly neutrophil elastase (NE), it plays a key role in maintaining pulmonary protease–antiprotease balance. In deficient states, unrestrained NE activity promotes damage to the lung matrix, causing structural defects and impairing host defenses. The commonest form of AAT deficiency results in a mutated Z AAT that is abnormally folded, polymerized, and aggregated in the liver. Consequently, systemic levels are lower, resulting in diminished pulmonary concentrations. Hepatic disease occurs due to liver aggregation of the protein, while lung destruction ensues from unopposed protease-mediated damage. In this review, we will discuss AAT deficiency, its clinical manifestations, and augmentation therapy. We will address the safety and tolerability profiles of AAT replacement in the context of patient outcomes and cost-effectiveness and outline future directions for work in this field.

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          Most cited references 80

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          Alpha1-antitrypsin deficiency.

          Alpha1-antitrypsin deficiency is a genetic disorder that affects about one in 2000-5000 individuals. It is clinically characterised by liver disease and early-onset emphysema. Although alpha1 antitrypsin is mainly produced in the liver, its main function is to protect the lung against proteolytic damage from neutrophil elastase. The most frequent mutation that causes severe alpha1-antitrypsin deficiency arises in the SERPINA 1 gene and gives rise to the Z allele. This mutation reduces concentrations in serum of alpha1 antitrypsin by retaining polymerised molecules within hepatocytes: an amount below the serum protective threshold of 11 micromol/L increases risk for emphysema. In addition to the usual treatments for emphysema, infusion of purified alpha1 antitrypsin from pooled human plasma represents a specific treatment and raises the concentrations in serum and epithelial-lining fluid above the protective threshold. Evidence suggests that this approach is safe, slows the decline of lung function, could reduce infection rates, and might enhance survival. However, uncertainty about the cost-effectiveness of this expensive treatment remains.
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            Replacement therapy for alpha 1-antitrypsin deficiency associated with emphysema.

            In patients with alpha 1-antitrypsin deficiency, the development of emphysema is believed to be caused by the unchecked action of proteases on lung tissue. We evaluated the feasibility, safety, and biochemical efficacy of intermittent infusions of alpha 1-antitrypsin in the treatment of patients with alpha 1-antitrypsin deficiency. Twenty-one patients were given 60 mg of active plasma-derived alpha 1-antitrypsin per kilogram of body weight, once a week for up to six months. After a steady state had been reached, the group had trough serum levels of alpha 1-antitrypsin of 126 +/- 1 mg per deciliter as compared with 30 +/- 1 mg per deciliter before treatment, and serum anti-neutrophil elastase capacities of 13.3 +/- 0.1 microM as compared with 5.4 +/- 0.1 microM. The alpha 1-antitrypsin level in the epithelial-lining fluid of the lungs was 0.46 +/- 0.16 microM before treatment, and the anti-neutrophil elastase capacity was 0.81 +/- 0.13 microM. Six days after infusion, alpha 1-antitrypsin levels (1.89 +/- 0.17 microM) and anti-neutrophil elastase capacities (1.65 +/- 0.13 microM) in the lining fluid were significantly increased (P less than 0.0001). Because of the chronicity of the disorder and the lack of sensitive measures of lung destruction, the clinical efficacy of this therapy could not be studied rigorously. No changes in lung function were observed in our patients over six months of treatment. The only important adverse reactions to the 507 infusions were four episodes of self-limited fever. This study demonstrates that infusions of alpha 1-antitrypsin derived from plasma are safe and can reverse the biochemical abnormalities in serum and lung fluid that characterize this disorder. Together with lifetime avoidance of cigarette smoking, replacement therapy with alpha 1-antitrypsin may be a logical approach to long-term medical treatment.
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              Liver disease in alpha1-antitrypsin deficiency detected by screening of 200,000 infants.

               T Sveger (1976)
              We prosepctively studied 200,000 newborns to determine the frequency and clinical characteristics of alpha1-antitrypsin deficiency. One hundred and twenty Pi Z, 48 Pi SZ, two PI Z-and one Pi S-infants were identified and followed to the age of six months. Fourteen of 120 Pi Z infants had prolonged obstructive jaundice, nine with severe clinical and laboratory evidence of liver disease. Five had only laboratory evidence of liver disease. Eight other Pi Z infants had minimal abnormalities in serum bilirubin and hepatic enzyme activity and variable hepatosplenomegaly. All 22 Pi Z infants with hepatic abnormalities, two thirds of whom were made, appeared healthy at six months of age. Ninety-eight Pi Z infants did not have clinical liver disease, but liver-function tests gave abnormal results in 44 of 84 at three months, and in 36 of 60 at six months of age. The number of small-for-gestational-age infants was greater (P less than 0.001) among those with clinical liver disease. None of the 48 Pi SZ infants had clinical liver disease, but 10 of 42 at three months and one of 22 at six months of age had abnormal liver function. The Pi Z and Pi SZ phenotypes are associated with covert or readily apparent hepatic dysfunction in the first three months of life.
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                Author and article information

                Journal
                Ther Clin Risk Manag
                Ther Clin Risk Manag
                Therapeutics and Clinical Risk Management
                Therapeutics and Clinical Risk Management
                Dove Medical Press
                1176-6336
                1178-203X
                2015
                29 January 2015
                : 11
                : 143-151
                Affiliations
                [1 ]Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
                [2 ]Department of Respiratory Medicine, Beaumont Hospital, Dublin, Republic of Ireland
                Author notes
                Correspondence: Sanjay H Chotirmall, Lee Kong Chian School of Medicine, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Email schotirmall@ 123456ntu.edu.sg
                Article
                tcrm-11-143
                10.2147/TCRM.S51474
                4321641
                © Chotirmall et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

                The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

                Categories
                Review

                Medicine

                emphysema, replacement, deficiency, augmentation, alpha-1

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