Efficacy and Safety Study of DX-88 to Treat Acute Attacks of Hereditary Angioedema (HAE)

A Double-blind, Placebo-controlled Study (72 Patients, Randomized 1:1) Followed by a Repeat-dosing Phase to Assess the Efficacy and Safety of DX-88 (Ecallantide; Recombinant Plasma Kallikrein Inhibitor) for the Treatment of Acute Attacks of Hereditary Angioedema

The purpose of this study is to determine if a subcutaneous dose of DX-88 (ecallantide; an investigational product) is safe and relieves symptoms of HAE in patients suffering from moderate to severe acute attacks of HAE.

Treatment Outcome Score (TOS) is a validated, comprehensive measure of symptom response to treatment. At 4 hours , patient assessment of response characterized by their change from baseline in symptom severity and collected by anatomic site of attack involvement, was recorded on a categorical scale (significant improvement [100] to significant worsening [-100]). The response at each anatomic site was weighted by baseline severity and then the weighted scores across all involved sites were averaged to calculate the TOS. Clinically meaningful improvement was indicated by a TOS of 30 or higher.

Mean Symptom Complex Severity (MSCS) score is a validated, comprehensive point-in-time measure of symptom severity. At baseline and 4 hours, patients rated the severity on a categorical scale (0 = normal, 1 = mild, 2 = moderate, 3 = severe) for symptoms at each affected anatomical location. Ratings were averaged to obtain the MSCS score. A decrease in MSCS score reflected an improvement in symptoms; clinically meaningful improvement (minimally important difference) was indicated by a reduction in the score of 0.30 or more.

The overall response assessment is a patient-reported assessment of global response to therapy. Patients are asked to perform an overall response assessment at regular intervals, relative to baseline. Patients were asked "overall how are you feeling" compared to how they felt before study drug. Answer options were "a lot worse", "a little worse", "same", "a little better" or "a lot better or resolved". Significant improvement was the first time that the patient responded to the assessment as "a little better or resolved".

Patient-reported severity of symptom complexes at baseline, by symptom complex and treatment group. Patients were to have at least one symptom complex that was moderate or severe. Patients could present with multiple symptom complexes, some of which could be mild. Mild=noticeable but do not impact daily living activities; Moderate=treatment or intervention is highly desirable and activities of daily living are impacted; Severe=require treatment or intervention due to inability to perform activities of daily living. The results are for number of patients with symptom complexes including mild, moderate and severe, provided the patients have at least one symptom complex that was moderate or severe

Treatment Outcome Score (TOS) is a validated, comprehensive measure of symptom response to treatment. At 4 hours , patient assessment of response characterized by their change from baseline in symptom severity and collected by anatomic site of attack involvement, was recorded on a categorical scale (significant improvement [100] to significant worsening [-100]). The response at each anatomic site was weighted by baseline severity and then the weighted scores across all involved sites were averaged to calculate the TOS. Clinically meaningful improvement was indicated by a TOS of 30 or higher.

Change From Baseline in Mean Symptom Complex Severity (MSCS) Score at 4 Hours Post-dose Over Multiple Treatment Episodes

The Mean Symptom Complex Severity (MSCS) score is a validated, comprehensive point-in-time measure of symptom severity. At baseline and 4 hours, patients rated the severity on a categorical scale (0 = normal, 1 = mild, 2 = moderate, 3 = severe) for symptoms at each affected anatomical location. Ratings were averaged to obtain the MSCS score. A decrease in MSCS score reflected an improvement in symptoms; clinically meaningful improvement was indicated by a reduction in the score of 0.30 or more.

The overall response assessment is a patient-reported assessment of global response to therapy. Patients are asked to perform an overall response assessment at regular intervals, relative to baseline (ie,immediately before treatment) using the following 5-category scale from significant improvement (Score = 100)to significant worsening (Score = -100)

Inclusion Criteria: Age 10 and older Documented diagnosis of HAE, Type I or II Executed informed consent Presentation for treatment within 8 hours of patient recognition of moderate to severe HAE attack Exclusion Criteria: Receipt of investigational drug or device, other than DX-88, within 30 days of treatment Receipt of non-investigational C1-INH (C1 esterase inhibitor) within 7 days of treatment Diagnostic of acquired angioedema, estrogen-dependent angioedema or drug induced angioedema Pregnancy or breastfeeding Patients who have received DX-88 within 7 days of presentation for dosing in the Double-blind Phase

Rubinstein E, Stolz LE, Sheffer AL, Stevens C, Bousvaros A. Abdominal attacks and treatment in hereditary angioedema with C1-inhibitor deficiency. BMC Gastroenterol. 2014 Apr 9;14:71. doi: 10.1186/1471-230X-14-71.

MacGinnitie AJ, Davis-Lorton M, Stolz LE, Tachdjian R. Use of ecallantide in pediatric hereditary angioedema. Pediatrics. 2013 Aug;132(2):e490-7. doi: 10.1542/peds.2013-0646. Epub 2013 Jul 22.

Sheffer AL, MacGinnitie AJ, Campion M, Stolz LE, Pullman WE. Outcomes after ecallantide treatment of laryngeal hereditary angioedema attacks. Ann Allergy Asthma Immunol. 2013 Mar;110(3):184-188.e2. doi: 10.1016/j.anai.2012.12.007. Epub 2013 Jan 5.

Bernstein JA, Shea EP, Koester J, Iarrobino R, Pullman WE. Assessment of rebound and relapse following ecallantide treatment for acute attacks of hereditary angioedema. Allergy. 2012 Sep;67(9):1173-80. doi: 10.1111/j.1398-9995.2012.02864.x. Epub 2012 Jul 5.

Riedl M, Campion M, Horn PT, Pullman WE. Response time for ecallantide treatment of acute hereditary angioedema attacks. Ann Allergy Asthma Immunol. 2010 Dec;105(6):430-436.e2. doi: 10.1016/j.anai.2010.09.005. Epub 2010 Oct 25.

Cicardi M, Levy RJ, McNeil DL, Li HH, Sheffer AL, Campion M, Horn PT, Pullman WE. Ecallantide for the treatment of acute attacks in hereditary angioedema. N Engl J Med. 2010 Aug 5;363(6):523-31. doi: 10.1056/NEJMoa0905079.