Safety of C1-inhibitor for clinical use

The Lectin Pathway of Complement in Myocardial Ischemia/Reperfusion Injury-Review of Its Significance and the Potential Impact of Therapeutic Interference by C1 Esterase Inhibitor

Acute myocardial infarction (AMI) remains a leading cause of morbidity and mortality in modern medicine. Early reperfusion accomplished by primary percutaneous coronary intervention is pivotal for reducing myocardial damage in ST elevation AMI. However, restoration of coronary blood flow may paradoxically trigger cardiomyocyte death secondary to a reperfusion-induced inflammatory process, which may account for a significant proportion of the final infarct size. Unfortunately, recent human trials targeting myocardial ischemia/reperfusion (I/R) injury have yielded disappointing results. In experimental models of myocardial I/R injury, the complement system, and in particular the lectin pathway, have been identified as major contributors. In line with this, C1 esterase inhibitor (C1INH), the natural inhibitor of the lectin pathway, was shown to significantly ameliorate myocardial I/R injury. However, the hypothesis of a considerable augmentation of myocardial I/R injury by activation of the lectin pathway has not yet been confirmed in humans, which questions the efficacy of a therapeutic strategy solely aimed at the inhibition of the lectin pathway after human AMI. Thus, as C1INH is a multiple-action inhibitor targeting several pathways and mediators simultaneously in addition to the lectin pathway, such as the contact and coagulation system and tissue leukocyte infiltration, this may be considered as being advantageous over exclusive inhibition of the lectin pathway. In this review, we summarize current concepts and evidence addressing the role of the lectin pathway as a potent mediator/modulator of myocardial I/R injury in animal models and in patients. In addition, we focus on the evidence and the potential advantages of using the natural inhibitor of the lectin pathway, C1INH, as a future therapeutic approach in AMI given its ability to interfere with several plasmatic cascades. Ameliorating myocardial I/R injury by targeting the complement system and other plasmatic cascades remains a valid option for future therapeutic interventions.

On the value of therapeutic interventions targeting the complement system in acute myocardial infarction

The complement system plays an important role in the inflammatory response subsequent to acute myocardial infarction (AMI). The aim of this study is to create a systematic overview of studies that have investigated therapeutic administration of complement inhibitors in both AMI animal models and human clinical trials. To enable extrapolation of observations from included animal studies toward post-AMI clinical trials, ex vivo studies on isolated hearts and proof-of-principle studies on inhibitor administration before experimental AMI induction were excluded. Positive therapeutic effects in AMI animal models have been described for cobra venom factor, soluble complement receptor 1, C1-esterase inhibitor (C1-inh), FUT-175, C1s-inhibitor, anti-C5, ADC-1004, clusterin, and glycosaminoglycans. Two types of complement inhibitors have been tested in clinical trials, being C1-inh and anti-C5. Pexelizumab (anti-C5) did not result in reproducible beneficial effects for AMI patients. Beneficial effects were reported in AMI patients for C1-inhibitor, albeit in small patient groups. In general, despite the absence of consistent positive effects in clinical trials thus far, the complement system remains a potentially interesting target for therapy in AMI patients. Based on the study designs of previous animal studies and clinical trials, we discuss several issues which require attention in the design of future studies: adjustment of clinical trial design to precise mechanism of action of administered inhibitor, optimizing the duration of therapy, and optimization of time point(s) on which therapeutic effects will be evaluated.

Hereditary angioedema caused by c1-esterase inhibitor deficiency: a literature-based analysis and clinical commentary on prophylaxis treatment strategies

Hereditary angioedema (HAE) caused by C1-esterase inhibitor deficiency is an autosomal-dominant disease resulting from a mutation in the C1-inhibitor gene. HAE is characterized by recurrent attacks of intense, massive, localized subcutaneous edema involving the extremities, genitalia, face, or trunk, or submucosal edema of upper airway or bowels. These symptoms may be disabling, have a dramatic impact on quality of life, and can be life-threatening when affecting the upper airways. Because the manifestations and severity of HAE are highly variable and unpredictable, patients need individualized care to reduce the burden of HAE on daily life. Although effective therapy for the treatment of HAE attacks has been available in many countries for more than 30 years, until recently, there were no agents approved in the United States to treat HAE acutely. Therefore, prophylactic therapy is an integral part of HAE treatment in the United States and for selected patients worldwide. Routine long-term prophylaxis with either attenuated androgens or C1-esterase inhibitor has been shown to reduce the frequency and severity of HAE attacks. Therapy with attenuated androgens, a mainstay of treatment in the past, has been marked by concern about potential adverse effects. C1-esterase inhibitor works directly on the complement and contact plasma cascades to reduce bradykinin release, which is the primary pathologic mechanism in HAE. Different approaches to long-term prophylactic therapy can be used to successfully manage HAE when tailored to meet the needs of the individual patient.

Angio-oedema due to hereditary C1 inhibitor deficiency in children

Hereditary angio-oedema due to C1 inhibitor deficiency (HAE-C1-INH) is a rare inherited disorder characterised by recurring and debilitating episodes of cutaneous swelling and abdominal pain and less frequent episodes of laryngeal oedema. Symptom onset is usually in childhood and early adolescence, with earlier disease onset associated with greater disease severity. Although HAE-C1-INH attacks are generally less frequent and less severe in children than in adults, they can cause significant physical and psychological impairment and affect advancement in school. There are often significant delays in the diagnosis of HAE-C1-INH due to its variable clinical presentation and because abdominal symptoms can often mimic other common paediatric gastrointestinal disorders. In recent years, several disease-specific agents have become available for the acute and prophylactic treatment of HAE-C1-INH. Although these treatments have not been evaluated rigorously in controlled clinical trials in children with HAE-C1-INH, paediatric data on efficacy and safety are available for some agents. Early diagnosis and initiation of appropriate therapy in children with HAE-C1-INH can help reduce the burden of this illness in the paediatric population.

c-Jun DNAzymes Inhibit Myocardial Inflammation, ROS Generation, Infarct Size, and Improve Cardiac Function After Ischemia-Reperfusion Injury

Objectives— Coronary reperfusion has been the mainstay therapy for reduced infarct size after a heart attack. However, this intervention also results in myocardial injury by initiating a marked inflammatory reaction, and new treatments are keenly sought.

Methods and Results— The basic-region leucine zipper protein, c-Jun is poorly expressed in the normal myocardium and is induced within 24 hours after myocardial ischemia-reperfusion injury. Synthetic catalytic DNA molecules (DNAzymes) targeting c-Jun (Dz13) reduce infarct size in the area-at-risk (AAR) regardless of whether it is delivered intramyocardially at the initiation of ischemia or at the time of reperfusion. Dz13 attenuates neutrophil infiltration, c-Jun and ICAM-1 expression in vascular endothelium, cardiomyocyte apoptosis, and the generation of reactive oxygen species in the reperfused myocardium. It inhibits infiltration into the AAR of complement 3 (C3), C3a receptor (C3aR), membrane attack complex-1 (Mac-1), or matrix metalloproteinase-2 (MMP-2) positive inflammatory cells. Dz13 also improves cardiac function without influencing myocardial vascularity or fibrosis.

Conclusion— These findings demonstrate the regulatory role of c-Jun in the pathogenesis of myocardial inflammation and infarction following ischemia-reperfusion injury, and inhibition of this process using catalytic DNA.

C1 inhibitor: just a serine protease inhibitor? New and old considerations on therapeutic applications of C1 inhibitor

C1 inhibitor is a potent anti-inflammatory protein as it is the major inhibitor of proteases of the contact and the complement systems. C1-inhibitor administration is an effective therapy in the treatment of patients with hereditary angioedema (HAE) who are genetically deficient in C1 inhibitor. Owing to its ability to modulate the contact and complement systems and the convincing safety profile, plasma-derived C1 inhibitor is an attractive therapeutic protein to treat inflammatory diseases other than HAE. In the present review we give an overview of the biology of C1 inhibitor and its use in HAE. Furthermore, we discuss C1 inhibitor as an experimental therapy in diseases such as sepsis and myocardial infarction.