CORE Metadata, citation and similar papers at core.ac.uk Provided by PubMed Central Clinical Medicine Insights: Cardiology OPEN ACCESS Full open access to this and thousands of other papers at REVIEW http://www.la-press.com. Ecallantide for the Treatment of Hereditary Angiodema in Adults Michael Lunn and Erin Banta Penn State Hershey Section of Allergy and Immunology, Hershey, PA 17033, USA. Corresponding author email: [email protected] Abstract: Hereditary angioedema (HAE) is a clinical disorder characterized by a deficiency of C1 esterase inhibitor (C1-INH). HAE has traditionally been divided into two subtypes. Unique among the inherited deficiencies of the complement system, HAE Types I and II are inherited as an autosomal dominant disorder. The generation of an HAE attack is caused by the depletion and/or consumption of C1-inhibitor manifested as subcutaneous or submucosal edema of the upper airway, face, extremities, or gastrointestinal tract mediated by bradykinin. Attacks can be severe and potentially life-threatening, particularly with laryngeal involvement and treatment of acute attacks in the United States has been severely limited. In December 2009 the FDA approved ecallantide for the treatment of acute HAE attacks. Ecallantide is a small recombinant protein acting as a potent, specific and reversible inhibitor of plasma kallikrein which binds to plasma kallikrein blocking its binding site, directly inhibiting the conversion of high molecular weight kininogen to bradykinin. Administered subcutaneously, ecallantide was demonstrated in two clinical trials, EDEMA3 and EDEMA4, to decrease the length and severity of acute HAE attacks. Although there is a small risk for anaphylaxis, which limits home administration, ecallantide is a novel, safe, effective and alternative treatment for acute HAE attacks. Keywords: hereditary angioedema, ecallantide, Kalbitor®, acute, angioedema Clinical Medicine Insights: Cardiology 2011:5 49–54 doi: 10.4137/CMC.S4434 This article is available from http://www.la-press.com. © the author(s), publisher and licensee Libertas Academica Ltd. This is an open access article. Unrestricted non-commercial use is permitted provided the original work is properly cited. Clinical Medicine Insights: Cardiology 2011:5 49 Lunn and Banta Introduction Clinically, HAE is characterized by episodic Hereditary angioedema (HAE) is a clinical disorder recurrent episodes of subcutaneous and sub-mucosal characterized by a deficiency of C1 esterase inhibi- angioedema. Swelling affects the hands and feet but tor (C1-INH) that results from mutations of the also involves the genitalia, trunk, face, upper airways, C1-INH gene located on chromosome 11.1,2 It was larynx, and gastrointestinal tract.16 The disease is char- first recognized in 1963 that C1-INH was deficient acterized by swelling, which is not associated with in the plasma of patients with HAE.3 Inherited as an urticaria, that does not respond to antihistamines, cor- autosomal dominant disorder, it is unique among the ticosteroids or epinephrine. Swelling during attacks inherited deficiencies of the complement system as usually subsides spontaneously in 72 hours.17 In HAE Types I and II are occur with equal frequency one study, abdominal attacks were reported in more among both men and women. Low levels of both than 93% of patients and composed almost 50% of C1-INH proteins distinguish Type I HAE, which all angioedema attacks.18 However, skin swellings accounts for approximately 80% to 85% of all HAE appear to be the most frequent symptoms of HAE.19 cases. Type II HAE, which occurs in 15% to 20% of A positive family history of angioedema is present patients, results from decreased functional activity of in most patients, although up to 25% of patients have the C1-INH gene, but with normal C1- INH levels.4,5 negative family histories with a de novo C1 inhibi- Recently, a new subtype of HAE, Type III, has tor mutations.18 Thus, the absence of a family history been described in the literature. Type III is charac- in the presence of typical symptoms should not be terized by an X-linked dominant inheritance and a deterrent from making the diagnosis. Even within initially observed exclusively in women and is asso- families with the same genetic aberration symptoms ciated with normal levels and function of C1-INH.6 vary considerably and it is not unusual for one family Most cases appear to be estrogen induced;7 however, member to have severe recurrent attacks and another more recently males have been identified that appear to be relatively free of symptoms. to have type III HAE, but with normal levels of C4, C1-INH-A and C1-INH-F. History of Treatment for Acute Generation of HAE attacks are caused by the deple- HAE Attacks tion and/or consumption of C1 inhibitor. The role of HAE attacks can be variable in both frequency and C1-INH in regulation of the contact system activation, severity. In the United States, the treatment for acute via inactivation of plasma kallikrein and factor XIIa, HAE attacks has been severely limited until recently. was discovered during the 1970s and 1980s.8 Via inac- Therapies have included fresh frozen plasma (FFP), tivation of C1r and C1s, C1-INH is the primary regu- 17α-alkylated androgens, and antifibrinolytic agents. lator of the classic complement pathway activation.9 All of which have their inherent safety and side effect The low plasma concentration of functionally active profiles.20–22 (Table 1) In October of 2009, the FDA C1-INH permits overactivation of the kallikrein-kinin approval of C1-INH replacement (Berinert®; CSL system, the classical complement pathway, the fibrin- Behring, Melbourne, Australia) greatly improved the olytic system and the coagulation system, with release treatment options available for the treatment of acute of vasoactive peptides among which bradykinin is attacks. More recently, in December, 2009 the United considered to be most important.10–12 Bradykinin is States Food and Drug Association (FDA) approval released by cleavage of kininogen by kallikrein and it of ecallantide (Kalbitor® [previously, DX-88]; Dyax, is capable of inducing edema as a result of its effects Cambridge, MA) for acute attacks in patients 16 years on vasodilation and microvessel permeability.13,14 of age has allowed for even greater treatment options The exact prevalence of HAE is not known, but it of this rare, but potentially life threatening disorder.23 has been estimated to range from 1:10,000 to 1:150,000 Ecallantide has not been studied for prevention of in the general population. This suggests that there are HAE attacks as prophylactic therapy. 2000 to 30,000 affected patients in the United States (US).14 Patients with HAE typically begin to swell in Pharmacology and Pharmacokinetics childhood and often experience increase symptoms Ecallantide is a small recombinant protein (7054 Da) beginning about the time of puberty.15 synthesized in the yeast Pichia pastoris and acts as 50 Clinical Medicine Insights: Cardiology 2011:5 Ecallantide for treatment of HAE Table 1. A comparison of both approved and frequently used treatments for acute HAE attacks in the USA. Method of Mechanism of Half-life Route of FDA status production action treatment FFP (fresh frozen Blood product Replaces C1 Long IV Used, but not approved for plasma) esterase inhibitor the treatment of acute HAE attacks Berinert® Plasma concentrate C1 inhibitor 24–46.5 h IV FDA approved for the treatment of acute attacks Ecallantide Recombinant protein Kallikrein inhibitor 1–4 h SC FDA approved for the treatment of acute HAE attacks Abbreviations: HAE, hereditary angioedema; IV, intravenous; SC, subcutaneous. a potent, specific, and reversible inhibitor of plasma Additionally, it is unknown whether ecallantide is kallikrein. Ecallantide binds to plasma kallikrein and excreted in human milk and caution should be also blocks its binding site, directly inhibiting the conver- exercised when administered to nursing women. sion of high molecular weight kininogen (HMWK) to Clinical trials did not include sufficient numbers bradykinin.24–27 of subjects aged 65 and over to determine response Ecallantide is eliminated in the urine and after in elderly patients. Currently approved for patients administration of a single 30 mg subcutaneous dose, 16 years of age and older, the safety and effectiveness a mean (±standard deviation) maximum plasma con- in pediatric patients has yet to be established. centration of 586 ± 106 ng/mL was observed approx- imately 2 to 3 hours post-dose in healthy subjects. Safety and Tolerability The mean area under the concentration-time curve In 255 patients between the ages of 10 and 78 years was 3017 ± 402 ng*hr/mL with a mean elimination with HAE treated with either intravenous or sub- half-life of 2.0 ± 0.5 hours. Plasma clearance was cutaneous ecallantide, the most adverse effect was 153 ± 20 mL/min and the volume of distribution was headache (16.1%). Additional side effects included 26.4 ± 7.8 L. Body weight, age, and gender were not nausea (12.9%), fatigue (11.8%), diarrhea (10.6%), found to affect ecallantide exposure significantly. upper respiratory tract infection (8.2%), injection There is no pharmacokinetic data available in patients site reactions (7.4%), nasopharyngitis (5.9%), vom- with hepatic or renal impairment.27 iting (5.5%), pruritus (5.1%), upper abdominal pain (5.1%), and pyrexia (4.7%).27 As noted, the above Dosing Strategy data is combined from all patients treated with ecal- Each single use vial contains ecallantide at a concen- lantide either intravenously in the EDEMA1® trial28 tration of 10 mg/mL with a recommended dose of or via subcutaneous administration documented in 30 mg, administered subcutaneously in three 10 mg the EDEMA3® and EDEMA4® trials.29,30 As ecallan- (1 mL) injections. A repeat dose (30 mg) can be given tide is a recombinant product, it is free of potential if the attack persists and may be administered within human or animal contaminants.31 a 24 hour period.