Recent Advances in the Research and Development of Alpha-1 Proteinase Inhibitor for Therapeutic Use

characterization of human  1 -PI; epidemiology of  1 -PI deficiency and currently licensed treatment; summary of the manufacturing and recent quality improvements of the  1 -PI plasma-derived products; safety and efficacy of  1 -PI intravenous augmentation and alternative routes; development of recombinant versions of human  1 -PI; conditions other than emphysema that are associated with  1 -PI; and some other aspects related to the research and development of  1 -PI for therapeutic use. The developments in molecular medicine are transforming respiratory medicine. Leading clinicians and scientists in the world have brought their knowledge and experience in their contributions to this book. Clinicians and researchers will learn about the most recent advances in a variety of lung diseases that will better enable them to understand respiratory disorders. This treatise presents state of the art essays on airways disease, neoplastic diseases, and pediatric respiratory conditions. Additionally, aspects of immune regulation, respiratory infections, acute lung injury/ARDS, pulmonary edema, functional evaluation in respiratory disorders, and a variety of other conditions are also discussed. The book will be invaluable to clinicians who keep up with the current concepts, improve their diagnostic skills, and understand potential new therapeutic applications in lung diseases, while scientists can contemplate a plethora of new research avenues for exploration.

1 -PI is encoded by a single 12.2 kb gene (Pi) located on the long arm of chromosome 14 (Long et al., 1984;Rabin et al., 1986). Over 120 alleles of 1 −PI have been identified with approximately 35 of them being associated with 1 −PI deficiency, including Z-allele, which is the most common cause of the deficiency when inherited in a homozygous fashion. Due to a single mutation in the mobile domain (Glu342Lys), the 1 −PI Z-mutant undergoes aberrant conformational transitions that prompts the protein to aggregate. This results in retention of polymerized 1 −PI Z mutant within hepatocytes, thus inducing disease conditions in the liver and causing 1 −PI deficiency in the circulation (Ekeowa et al., 2011;Lomas, 2005;Volpert et al., 2000). The prevalence of three major 1 −PI variants (PiM, PiS, and PiZ) defines the number of carriers (PiMZ and PiMS) and individuals with deficiency phenotypes ( PiZZ, PiSZ, and PiSS). The epidemiology of 1 −PI deficiency and its clinical manifestations, including lung diseases and liver diseases, has been described in detail (Ekeowa et al., 2011;Luisetti & Seersholm, 2004;Needham & Stockley, 2004;Gooptu & Lomas, 2009). Based on the 1 −PI serum concentration, a common classification to define 1 −PI deficiency includes the four major categories: (1) normal (with 1 −PI serum levels not lower than 20 M); (2) deficient (with 1 −PI concentrations in serum lower than 20 M); (3) dysfunctional (with normal 1 −PI level, but lost or lower inhibitory activity); and (4) null (with 1 −PI serum concentrations below the detectable level). 1 −PI is a 52 kDa glycoprotein belonging to the serine protease inhibitor (serpin) superfamily, which in addition to 1 -PI also includes  1 -antichymotrypsin, antithrombin, plasminogen activator inhibitor, C1 esterase inhibitor, and many others (Stein & Carrell, 1995;Silverman et al., 2001). A single polypeptide chain of 1 -PI is comprised of 394 amino acid residues, including one cysteine, 2 tryptophanes, and 9 methionine residues (Carp et al., 1982;Johnson & Travis, 1979). Three N-linked glycans attached to asparagine residues 46, 83, and 247 represent ~12% of 1 −PI by molecular weight (Mega et al., 1980a,b;Carrell et al., 1981Carrell et al., , 1982. The carbohydrate moiety is comprised of biantennary N-glycans, but also triantennary and traces of tetraantennary structures grounded on the mannose fork core and containing N-acetyl glucosamine, galactose, and terminal negatively-charged sialic www.intechopen.com (N-acetylneuraminic) acid (Mega et al., 1980b;Travis & Salvesen, 1983;Kolarich et al., 2006a). The glycosylation pattern is a major cause of the iso-electric focusing (IEF) pattern typical for 1 −PI with major isoforms M2, M4, M6, and also M7 and M8 due to the Nterminal truncation (Jeppsson et al., 1985;Kolarich et al., 2006a,b). Some characteristics of human 1 −PI are listed in Table 1. Like the majority of other native glycoproteins, 1 -PI is intrinsically a highly heterogeneous moiety, mainly due to variably trimmed glycosylation and an N-terminal pentapeptide that can be absent (Hercz, 1985;Krasnewich et al., 1995;Vaughan et al., 1982).

Characteristics Description
Synonyms alpha-1-proteinase inhibitor, alpha-1-antitrypsin Common abbreviations 1 −PI, alpha-1-PI, 1 −AT, alpha-1-AT, A1AT, ATT, AT Classification Serine proteinase inhibitor ( Normal (NLT a 20 M); Deficient (lower than 20 M; Dysfunctional (NLT 20 M, inactive); Null (n.d. b level) Diseases related to 1 −PI deficiency and aggregation Pulmonary and liver diseases Other rare diseases (putative) c a NLT, not lower than; b n.d., non-detectable; c See Table 3 Table 1. Characteristics of human 1 -PI Figure 1 shows a crystal structure of 1 -PI, typical for serpins, which features 9 -helices, 3 -sheets (A, B, and C), and a mobile 15-residue reactive center loop (RCL) exposed for interaction with the target serine protease (Johnson & Travis, 1979;Lomas, 2005). Protease attack of the RCL results in cleavage at Met358-Ser359, formation of a covalent 1 -PIprotease complex with the amino-terminal polypeptide inserted into the A -sheet, and an overall dramatic conformational change (Huntington et al., 2000;Ludeman et al., 2001;Stratikos & Gettins, 1999;Wilczynska et al., 1997). Unlike the majority of proteins, 1 −PI is naturally folded in a metastable structure which is essential for its function. This is not the most thermodynamically stable form, and thus, 1 -PI is prone to a variety of conformational transitions and modifications (Lomas, 2005;Lomas www.intechopen.com et al., 1995). Much like other serpins, 1 -PI can intramolecularly convert into a more stable latent form, which is inactive, but the biological activity can be restored via denaturation and refolding (Lomas et al., 1995;Silverman et al., 2001). In addition to its inhibitory antiprotease function, 1 −PI exhibits a broad spectrum of noninhibitory activities (Brantly, 2002;Janciauskiene et al., 2011;Nita et al., 2005). Because of the nine methionine residues in 1 −PI molecule, its plausible role as a putative antioxidant has been suggested (e.g., Levine et al., 1999Levine et al., , 2000. Due to the abundance of 1 −PI in human plasma and its conservative tertiary structure with hydrophobic cavities (Elliott et al., 2000;Lee et al., 2001;Parfrey et al., 2003), 1 −PI has the capacity to bind small hydrophobic molecules. This property has been explored mainly with respect to the peptides and small molecules that may prevent the aggregation of the 1 −PI Z mutant (Mahadeva et al. 2002;Mallya et al., 2007;Chang et al. 2009).

The  1 -PI deficiency and  1 -PI replacement therapy
There are approximately 60,000-100,000 severely deficient individuals in the United States which define 1 -PI deficiency as a rare disease. However, according to several publications, 1 -PI deficiency is widely under-and mis-diagnosed (e.g., de Serres, 2003;Bals et al., 2007). As reported by the World Health Organization (WHO, 1997), only 4% of the individuals with 1 -PI deficiency cases are identified, and only a portion of them are receiving treatment. Currently licensed treatment of the patients with 1 -PI deficiency and manifestation of pulmonary emphysema involves intravenous infusion of plasma-derived 1 -PI preparations with the recommended dose of 60 mg of active 1 -PI per kg of body weight administered once weekly. To maintain a threshold level of 1 -PI (11µM), 1 −PIdeficient patients should receive augmentation therapy for the duration of their lives, to slow the progression of emphysema. This nadir level has been determined based on 1 -PI www.intechopen.com 1 -PI concentrate -Aralast NP ® -that has the same formulation as its predecessor, but differs from the earlier approved product by having a significantly lower content of C-terminal lysine-truncated 1 -PI (approximately 2% vs. 67%). In 2009, the US FDA approved Prolastin C ® , the updated version of the earlier Talecris product that had been on the market for more than two decades. Due to more sophisticated purification and pathogen reduction steps, including two dedicated viral inactivation steps instead of heat treatment, the specific activity of Prolastin C ® (above 0.7 mg of functional 1 -PI per mg of total protein) is twice higher than that of Prolastin ® , which means that lower volumes and shorter transfusion time are needed. Most recently, in July 2010, the FDA approved Glassia TM (formerly Respira), a product manufactured by Kamada (Weizmann Science Park, Ness Ziona, Israel; www.kamada.com) and commercially launched by Baxter in the United States and some other countries. Glassia TM is another highly purified 1 -PI (with specific activity above 0.7 mg of active 1 -PI per mg of total protein) and the only 1 -PI product that is available in a ready-to-use liquid form with a shelf-life stability of two years under refrigerated conditions. 1 −PI products are manufactured as part of a complex plasma fractionation scheme which was originally developed for large-scale production of albumin, but now also yields many other plasma therapeutics  . Since products are made from pooled human plasma, they may  The US FDA product approval information is available at  Table 2. The plasma-derived 1 -PI therapeutic products approved by the US FDA for chronic augmentation and maintenance therapy in adults with congenital 1 -PI deficiency and clinically evident emphysema a carry the risk of transmitting human infectious agents, e.g., some viruses, and theoretically, the Creutzfeldt-Jakob disease (CJD) agent or disease variant agents, as well as emerging or unknown infectious agents. To reduce the potential risk of transmitting infectious agents, the 1 -PI preparations are manufactured using a number of viral inactivation and removal steps. Currently approved 1 −PI products differ in the procedures used for pathogen reduction. For instance, the heat treatment procedure used in manufacturing of Prolastin was one of the reasons for higher content of inactive and aggregated 1 −PI in the product. The manufacturing procedures of the later products (Table 2) include two dedicated steps that are specifically designed for inactivation and removal of viruses (Hotta et al., 2010). Thus, solvent/detergent treatment and nanofiltration are used as the dedicated pathogen reduction steps in the manufacturing of recently approved Prolastin C ® , Glassia TM and both Aralast products. Overall, the manufacturing history of plasma-derived 1 -PI therapeutic products reflects a trend of continous improvement of product quality.

Heterogeneity of α 1 -PI products
Heterogeneity of 1 -PI therapeutic preparations is a complex phenomenon. First of all, heterogeneous nature of plasma 1 -PI is an intrinsic property of the native glycoproten (see 2.1). Second, the presence of variously processed 1 -PI forms including latent, cleaved, complexed or aggregated 1 -PI species, is barely avoidable. However, it must be kept minimal as the inactive protein species have a direct influence on the product's specific activity. Third, 1 -PI products purified from pooled human plasma contain certain impurities of other plasma proteins, including albumin, haptoglobin, 1 -antichymotrypsin, impurities ensures their tolerability, however, the level of these plasma proteins in 1 -PI concentrate may significantly increase the non-therapeutic protein load in the 1 -PI preparation intended for transfusion. In addition to all that, multistep manufacturing procedures are known to induce various protein alterations, such as aggregation and chemical modifications (e.g., deamidation, cysteinylation, and C-terminal truncation). Some modifications can be observed by IEF and other techniques (Cowden et al., 2005;Kolarich et al., 2006aKolarich et al., , 2006b) and reflected in the product specifications. Currently there are no data that would demonstrate whether these alterations affect the in vivo activity, safety, efficacy or immunogenicity of 1 -PI therapeutic preparations. In general, commercial plasma-derived 1 -PI products differ in terms of their purity, specific activity, modifications, and excipients (Lomas et al., 1997;Cowden et al., 2005;Stockley, 2010;Tonelli & Brantly, 2010).

Research and development of the recombinant versions of human  1 -PI 3.2.1 Advances in the development of recombinant α 1 -PI
The plasma supply per se is a limited source and appears to be insufficient to meet anticipated clinical demand. Moreover, despite effective viral inactivation/removal steps in the manufacturing of plasma proteins (Cai et al., 2005;Hotta et al., 2010), the risk of contamination with new and unknown pathogens may still exist. Therefore, recombinant technology has been widely explored as an alternative approach for the production of human 1 -PI since the pioneering works of the early 1980s (Bollen et al., 1983;Cabezon et al., 1984;Rosenberg et al., 1984). As evident from numerous reports, both from academic research and industry, the human gene for 1 -PI has been expressed in virtually all available hosts (E. coli, various yeasts, fungi, insect cells, CHO cells, human neuronal cells, and produced in transgenic plants and animals). For more details on research and development of recombinant 1 -PI (r-1 -PI) in different systems and advances and limitations of the recombinant approach for production of stable and biologically active 1 -PI, see our comprehensive 2006 review (Karnaukhova et al., 2006). More recently, the human gene for 1 -PI is available as a licensed therapeutic treatment. In general, the essential criteria for the development of therapeutics for human use are safety, optimal clinical efficacy, and maximum cost-effectiveness. Among many efforts to develop r-1 -PI of therapeutic quality (see Karnaukhova et al., 2006), there appear to be only two examples of the r-1 -PIs for which development went far enough to get to clinical trials. The first was r-1 -PI produced in the yeasts Saccromyces cerevisiae and manufactured by Arriva Pharmaceuticals Inc. (Arriva) for several indications. A nebulized formulation of this non-glycosylated r-1 -PI preparation has been intended for the treatment of respiratory disorders including emphysema and COPD (phase II clinical trials), and asthma (pre-clinical studies) (Brown, 2006a). Although animal studies have been considered to be successful (Pemberton et al., 2006), human trials have not been recommended (see review by Stokley, 2010). A topical gel formulation of r-1 -PI has been intended for the treatment of dermatitis and other severe dermatological disorders in phase II clinical trials (see Brown, 2006b). The second example of the advanced development of recombinant human 1 -PI is large scale production performed in transgenic dairy animals (t-1 -PI): sheep [by PPL Therapeutics (UK) in partnership with Bayer Biologicals (USA), (Dalrymple & Garner, 1998;Wright et al., 1991)], and goats [by Genzyme Transgenics Corporation (USA), (Ziomek, 1998)]. The transgenic 1 -PI recovered from sheep milk was purified to 99.9% purity. Even so, sheep native 1 -PI and sheep 1 -antichymotrypsin were major impurities, at 6.7-18.7 mg/L and 60.3-75.8 parts per million, respectively. Two sequential clinical studies were performed to evaluate the safety and immunogenicity of aerosolized transgenic human 1 -PI. None of the subjects had an antibody response to human t-1 -PI (Tebbutt, 2000;Spencer et al., 2005); however, antibody responses were observed to sheep 1 -PI and to sheep 1antichymotrypsin (Spencer et al., 2005). Four patients withdrew from the study due to the development of dyspnea and a decline in lung function, and the later product development was terminated.

Pitfalls in the development of r-α 1 -PI for therapeutic use
The general regulatory requirements for biologicals intended for therapeutic use, including r-1 -PI, are purity, safety, and efficacy. In order to be effective, therapeutic proteins have to be stable in vivo and in vitro (Karnaukhova et al., 2006). Reviewing the work performed over the last two decades to produce stable and biologically active r-1 -PI of therapeutic quality, one can see basically two major factors that were impeding the progress: (1) impurities that could induce antibody responses and cause adverse reactions in patients, and (2) lower stability than that of plasma counterpart, mainly caused by the lack of glycosylation or nonhuman type of glycosylation (the latter may also induce immune responses). Although presently the first reason can be technically better solved, removal of trace amounts of nonhuman native proteins derived from the host, e.g., sheep 1 -PI, from the human r-1 -PI to exclude further adverse reactions, requires a much higher level of purification than was possible at the time of that development. As for the second reason, indeed, glycosylation is considered to be a cause of rapid clearance of r-1 -PI from the circulation (Casolaro et al., 1987;Cantin et al., 2002a). Aberrant glycosylation (or lack of glycans) does not neccessarily affect biological activity of the recombinant protein, but it is important for its stability. According to recently published data, glycosylation of 1 -PI does not interfere with the serpin native state flexibility (or instability) essential for its efficient function, though it may confer resistance to degradation by proteases and thus extend its half-life in the circulation (Sarkar & Wintrode, 2011). Extensive work performed over decades for the development of viable r-1 -PI of therapeutic quality and lessons learned from these experiences truly paved the way for other protein therapeutics. It is worthwhile to mention two serpins produced in transgenic animals that were recently approved. In 2009, the US FDA approved recombinant antithrombin (ATryn ® ) produced in the milk of transgenic goats (Fyfe & Tait, 2009). In 2010, another serpin, recombinant human C1-esterase inhibitor (Ruconest ® ) produced in the milk of transgenic rabbits was granted European marketing authorization (Varga & Farkas, 2011). Both pharmaceutical proteins show a faster clearance, yet it may not be an issue depending on the intended use. For instance, Ruconest ® was approved for the treatment of acute attacks of hereditary angioedema, and therefore there is no need to maintain its higher level in blood longer than its action is required. Given a shorter in vivo half-life of recombinant 1 -PI, it has been considered for other administration routes and applications, such as inhalation for the treatment of emphysematous condition, and topical application for various skin diseases. However, a convincing proof of the recombinant product efficacy and safety in appropriate clinical trials is as problematic as it is for plasma-derived 1 -PI; large clinical trials in the cases of rare diseases are difficult to perform because of small geographically dispersed patient populations. In addition, a limited population means a limited market, which is less attractive for large investments. No doubt, these reasons markedly slow down the development of r-1 -PI.

3.3 1 -PI -based therapies 3.3.1 Safety and efficacy of intravenous  1 -PI augmentation
The intravenous augmentation of 1 -PI was shown to be safe and well tolerated over a long history of the replacement therapy. However, its impact on disease progression and mortality still remains to be convincingly proven. 1 -PI augmentation is assumed to slow down the rate of emphysema development and progression and, thus, to improve the life quality and duration of 1 -PI deficient patients, yet the essential proof of efficacy is missing. According to Hubbard & Crystal (1990), only approximately 2-3% of infused 1 −PI actually reaches the lungs; and the effictiveness of 1 -PI replacement therapy has been evaluated mainly on the bases of biochemical (not clinical) criteria (Tonelli & Brantly, 2010). For recently approved 1 -PI products, their pharmacokinetic equivalence and comparable safety profile to Prolastin were demonstrated (e.g., Stocks et al., 2010). 1 -PI therapy is a life-long and very expensive treatment that may cost up to $150,000 (Silverman, 2009) in the United States. Whether this therapy decreases mortality also remains unknown, as there are no reliable data on mortality, as well as morbidity and survival (Gøtzsche & Johansen, 2010a). Some observational studies support the idea that augmentation therapy may help to slow the decline in lung function (Seersholm et al., 1997;Wencker et al., 2001;Kueppers, 2011). But there are also more critical evaluations including the opinion that 1 -PI augmentation therapy cannot be recommended due to lack of evidence of clinical benefit and the cost of treatment (Gøtzsche & Johansen, 2010a, 2010b. It is currently widely admitted that the efficacy of 1 -PI augmentation therapy has never been persuasively demonstrated and must be proven in a proper clinical trial. Due to the widespread and small clusters of patients all over the country, conducting a prospective, randomized, placebo-controlled clinical trial is challenging. In addition, the development of emphysema proceeds slowly, creating the additional difficulties of monitoring lung function decline and mortality data (Hutchinson & Hughes, 1997;Schluchter et al., 2000).

Alternative routes of administration of  1 -PI products
Due to the inconvenience of life-time intravenous augmentation therapy and low levels of with adverse reactions due to impurities derived from the host (Spenser et al., 2005). Thus, higher levels of purification and more clinical studies are required.

Other  1 -PI applications
Currently, 1 -PI therapeutic preparations are licensed exclusively for one indication, i.e., chronic augmentation and maintenance therapy in individuals with emphysema due to congenital 1 -PI deficiency. Previously unrecognized inherited disorder, 1 -PI deficiency was first described in 1963 (Laurell & Eriksson, 1963) based on the serum electrophoretic analysis that revealed five individuals deficient of 1 -fraction; three of those patients had developed emphysematous conditions. Six years later, in 1969, cirrosis associated with 1 -PI deficiency was described (Sharp et al., 1969). These findings initiated a concept of linkage between 1 -PI deficiency and pulmonary and liver diseases. As evident from the available literature, due to the multiple biological activities of 1 -PI, it has been associated with other lung diseases (first of all, cystic fibrosis) and many non-pulmonary diseases ( Table 3). Some of these conditions may possibly benefit from 1 -PI augmentation therapy (see recent reviewes by Blanco et al., 2011 andJanciauskiene et al., 2011). According to Blanco et al. (2011), 1 -PI therapy has proven remarkable efficacy in small cohorts of 1 -PI-deficient patients who also suffer from fibromyalgia, systemic vasculitis, relapsing panniculitis and bronchial asthma. Although the putative benefits of 1 -PI therapy for treatment of additional rare diseases (some are listed in Table 3) requires much more clinical data than are currently available to support clinical efficacy and safety of 1 -PI treatment, in general it indicates a clear potential for additional 1 -PI supply to satisfy the anticipated clinical demand in near future. Because of controversy related to the additional clinical implications of  1 -PI deficiency, more clinical data are needed to verify whether the reported links between  1 -PI deficiency and other rare diseases are real or accidental. As a potent anti-inflammatory agent,  1 -PI has been investigated in clinical studies for treatment of cystic fibrosis (Jones & Helm, 2009). Whereas patients with emphysematous conditions suffer from the hereditary  1 -PI deficiency and, thus, insufficient levels of the protease inhibitor in the lungs due to impaired  1 -PI synthesis in hepatocytes, patients with cystic fibrosis may have normal synthesis of  1 -PI and suffer from severe pulmonary inflammation due to high excess of NE in the lungs, leading to a progressive loss of lung function (Allen, 1996;Siekmeier, 2010). Therefore, it has been proposed that both groups of patients may benefit from  1 -PI augmentation therapy to prevent the deleterious effect of free protease (Allen, 1996;Birrer, 1995;Birrer et al, 1996) However, intravenous administration of  1 -PI did not result in a suppression of the respiratory neutrophil elastase burden (McElvaney et al, 1991). Several studies have been conducted using inhalation of an aerosolized  1 -PI in cystic fibrosis and  1 -PI deficiency (Hubbard et al., 1989;Griese et al, 2001Griese et al, , 2007Martin et al, 2006;Brand et al, 2009). Whereas several studies that investigated the efficacy of treatment with an aerosolized  1 -PI both in patients with cystic fibrosis and in those with  1 -PI deficiency came to positive conclusions regarding deposition of inhaled  1 -PI in the lungs and its anti-elastase activity (see review by Siekmeier, 2010), the conclusion from other studies was that treatment with  1 -PI did not demonstrate any clinical improvements (Martin, 2006). If further clinical studies support the safety and efficacy of an aerosolized 1 -PI, and it is approved for treatment of cystic fibrosis, the demand for therapeutic  1 -PI preparations could be significantly increased.

Research toward the enhancement of  1 -PI-therapies
During last decade various approaches have been considered for the enhancement of  1 -PIbased therapies. For instance, to prolong a short half-life of r- 1 -PI in the circulation, Cantin and co-workers hypothesized that conjugation of r- 1 -PI with polyethylene glycol (PEG) at Cys 232 could extend the in vivo half-life of recombinant protein in blood and lung (Cantin et al., 2002b). According to their data, the site-specific conjugation with either 20 or 40 kD PEG at Cys 232 of nonglycosylated r- 1 -PI (human) results in an active inhibitor with extended in vivo stability. Moreover, 72 h later after airway instillation, the PEG-r- 1 -PI seemed to be significantly better than glycosylated  1 -PI at protecting the lung against elastase-induced lung hemorrhage.
As an example of the in vitro biochemical evaluation of the concept, 1 −PI has been considered for its affinity to various small ligands and drugs for different reasons. Mainly this approach has been explored with respect to the peptides and small molecules in order to prevent the aggregation of Z mutant (e.g., Mallya et al., 2007;Chang et al. 2009). In the meantime, the protein's potential for binding small ligands of pharmaceutical interest has been proposed as a promising approach that is directed at, and may ultimately enhance, currently existing 1 −PI therapies (Karnaukhova et al., 2010). For instance, 1 −PI's affinity to retinoic acid, which is known for a wide range of physiological activities including alveolar repair and regrowth (Roche clinical studies, see Stockley, 2010;Massaro & Massaro, 1996, 1997 and tissue rejuvenation in various dermatologic diseases, has been convincingly demonstrated in biochemical experiments in vitro (Karnaukhova et al., 2010). As 1 −PI augmentation therapy cannot cure, but may only slow down, the progression of emphysema, its complexation with retinoic acid could be more efficient for treatment than 1 −PI alone. It is noteworthy that the interactions of 1 −PI with several other physiologically active ligands (including porphyrins) may reveal additional properties of this multifunctional serpin.

Conclusions
Since  1 -PI deficiency was first described by Carl-Bertil Laurell and Sten Eriksson (Laurell & Eriksson, 1963) as a condition that could lead to the development of severe obstructive www.intechopen.com pulmonary disease, our knowledge about  1 -PI structure-function relationships and clinical manifestations of  1 -PI deficiency has increased tremendously. Moreover, multi-disciplinary research efforts prompted the development of  1 -PI-based augmentation therapy to maintain the inhibitor level above the protective threshold. Since 1987, several  1 -PI products derived from pooled human plasma have been approved and are currently available to slow down the progression of emphysematous conditions in  1 -PI-deficient patients. In addition, due to its multiple physiological activities,  1 -PI has been identified for its putative involvement in several other rare diseases, the treatment of which may possibly benefit from  1 -PI-based therapies. As an alternative to intravenous administration that may improve the efficacy of 1 -PI treatment, the inhalation of aerosolized  1 -PI preparations has been in clinical trials. Recombinant versions of human  1 -PI have been produced in all available hosts and in several transgenic animals. These efforts made a remarkable impact on the research realm of recombinant protein therapeutics, but did not yet bring any viable version of recombinant  1 -PI to the treatment. In regards to therapeutic preparations and their use, there are several questions to be addressed when looking to the future. Keeping in mind the long history of replacement therapy using currently approved plasma-derived  1 -PI products, it is essential that the efficacy of  1 -PI replacement therapy be clearly demonstrated in prospective, randomized, placebo-controlled trials. Will the efficacy of inhalation therapy using aerosolized  1 -PI preparations be proven to be superior to that of the intravenous route? Will the recombinant/transgenic versions of human  1 -PI be optimized to meet the requirements for protein therapeutics? Will other rare diseases currently implicated in association with  1 -PI and  1 -PI deficiency be clearly proven to benefit from  1 -PI treatment? From the standpoint of product quality, safety and efficacy, the current state of research and development of  1 -PI for therapeutic use demonstrates a symbiosis of the recent achievements and controversies, hopefully typical of our progress.