Pharmacotherapeutic group: Other haematological agents, Drugs used in hereditary angioedema: C1-inhibitor, plasma derived
ATC code: B06AC01
C1-esterase inhibitor is a plasma glycoprotein with a molecular weight of 105 kD and a carbohydrate moiety of 40 %. Its concentration in human plasma ranges around 240 mg/l. Besides its occurrence in human plasma, also the placenta, the liver cells, monocytes and platelets contain C1-esterase inhibitor.
C1-esterase inhibitor belongs to the serine-protease-inhibitor-(serpin)-system of human plasma as do also other proteins like antithrombin III, alpha-2-antiplasmin, alpha-1-antitrypsin and others.
Mechanism of action
Under physiological conditions C1-esterase inhibitor blocks the classical pathway of the complement system by inactivating the enzymatic active components C1s and C1r. The active enzyme forms a complex with the inhibitor in a stoichiometry of 1:1.
Furthermore, C1-esterase inhibitor represents the most important inhibitor of the contact activation of coagulation by inhibiting factor XIIa and its fragments. In addition, it serves, besides alpha-2-macroglobulin, as the main inhibitor of plasma kallikrein.
The therapeutic effect of Berinert in hereditary angioedema is induced by the substitution of the deficient C1-esterase inhibitor activity.
Clinical efficacy and safety
The efficacy and safety of Berinert for routine prophylaxis to prevent HAE attacks were demonstrated in a multicentre, randomised, double-blind, placebo-controlled, crossover study (Study 3001).
The study assessed 90 adult and adolescent subjects with symptomatic HAE type I or II. The median (range) age of subjects was 40 (12 to 72) years; 60 subjects were female and 30 subjects were male.
Subjects were randomised to receive either 60 IU/kg or 40 IU/kg Berinert in one 16-week treatment period and placebo in the other 16-week treatment period.
Patients self-administered Berinert or placebo subcutaneously 2 times per week. Efficacy was evaluated for the last 14 weeks of each treatment period. Eligible patients were also able to participate in an open-label extension study for up to 140 weeks (Study 3002).
Approximately half of the subjects enrolled in the extension study participated in Study 3001 (64/126, 50.8%), which contributed to the similarities between study populations.
Study 3001:
Twice per week S.C. doses of 60 IU/kg or 40 IU/kg Berinert resulted in a significant difference in the time-normalised number of HAE attacks (the rate of attacks) relative to placebo (Table 1). The time-normalised number of HAE attacks in subjects dosed with 60 IU/kg was 0.52 attacks per month compared to 4.03 attacks per month while receiving placebo (p <0.001). The time-normalised number of HAE attacks in subjects dosed with 40 IU/kg was 1.19 attacks per month compared to 3.61 attacks per month while receiving placebo (p <0.001).
Table 1. Time-normalised Number of HAE Attacks (Number/Month)
| | 60 IU/kg Treatment Sequences (N = 45) | 40 IU/kg Treatment Sequences (N = 45) |
| PRODUCT | Placebo | PRODUCT | Placebo |
| n | 43 | 42 | 43 | 44 |
| Mean (SD) | 0.5 (0.8) | 4.0 (2.3) | 1.2 (2.3) | 3.6 (2.1) |
| Min, Max | 0.0, 3.1 | 0.6, 11.3 | 0.0, 12.5 | 0.0, 8.9 |
| Median | 0.3 | 3.8 | 0.3 | 3.8 |
| LS Mean (SE)* | 0.5 (0.3) | 4.0 (0.3) | 1.2 (0.3) | 3.6 (0.3) |
| 95% CI for LS Mean* | (0.0, 1.0) | (3.5, 4.6) | (0.5, 1.9) | (3, 4.3) |
| Treatment difference(within-subjects) | 60 IU/kg – Placebo | 40 IU/kg – Placebo |
| LS Mean* (95% CI) | -3.5 (-4.2, -2.8) | -2.4 (-3.4, -1.5) |
| p-value* | < 0.001 | < 0.001 |
CI = confidence interval; HAE = hereditary angioedema; N = number of randomised subjects; n = number of subjects with data; LS = Least squares.
* From a mixed model.
The median (25th, 75th percentile) percentage reduction in the time-normalised number of HAE attacks relative to placebo was 95% (79, 100) on 60 IU/kg and 89% (70, 100) on 40 IU/kg Berinert among subjects with evaluable data in both treatment periods.
The percentage of responders (95% CI) with a ≥50% reduction in the time‑normalised number of HAE attacks on Berinert relative to placebo was 83% (73%, 90%). Ninety percent (90%) of subjects on 60 IU/kg responded to treatment and 76% of subjects on 40 IU/kg responded to treatment.
Seventy-one percent (71%) of subjects on 60 IU/kg and 53% of subjects on 40 IU/kg had ≥1 HAE attack per 4-week period on placebo and <1 HAE attack per 4-week period on Berinert.
A total of 40% of subjects on 60 IU/kg and 38% of subjects on 40 IU/kg were attack-free, and the median rate of HAE attacks per month was 0.3 on both doses.
Berinert resulted in a significant difference in the time-normalised number of uses of rescue medication (the rate of rescue medication use) relative to placebo. A dose of 60 IU/kg resulted in a mean rate of rescue medication of 0.3 uses per month, compared to 3.9 uses per month with placebo. A dose of 40 IU/kg resulted in a mean rate of rescue medication use of 1.1 uses per month, compared to 5.6 uses per month with placebo.
Study 3002:
The long-term safety and efficacy of Berinert for routine prophylaxis to prevent HAE attacks were demonstrated in an open-label, randomised, parallel-arm study.
The study assessed 126 adult and paediatric subjects with symptomatic HAE type I or II, consisting of 64 roll-over patients from study 3001 and 62 non-rollover patients.
The median (range) age of subjects was 41.0 (8-72) years. Patients with a monthly attack rate of 4.3 in 3 months before entry in the study were enrolled and treated for a mean of 1.5 years; 44 patients (34.9%) had more than 2 years of exposure.
Mean steady-state C1-INH functional activity increased to 52.0% with 40 IU/kg and 66.6% with 60 IU/kg. Incidence of adverse events was low and similar in both dose groups (11.3 and 8.5 events per patient-year for 40 IU/kg and 60 IU/kg, respectively).
The mean (SD) time-normalised number of HAE attacks was 0.45 (0.737) attacks per month for 40 IU and 0.45 (0.858) attacks per month for 60 IU.
The percentage of responders (95 % CI) with a ≥50 % reduction in the time-normalised number of HAE attacks on Berinert relative to the time-normalised number of HAE attacks used to qualify for participation in Study 3002 was 93.5 % (84.6 %, 97.5 %) in the 40 IU/kg treatment arm and 91.7 % (81.9 %, 96.4 %) in the 60 IU/kg treatment arm.
The percentage of subjects with a time-normalised HAE attack frequency of <1 HAE attack per 4-week period was 79.4 % for 40 IU/kg and 85.7 % for 60 IU/kg.
The percentage of HAE attack-free subjects was 34.9 % for 40 IU/kg and 44.4 % for 60 IU/kg (throughout the study duration with the maximum duration of exposure of >2.5 years). Of 23 patients receiving 60 IU/kg for more than 2 years, 19 (83 %) were attack-free during months 25 to 30 of treatment.
The mean time-normalised number of uses of rescue medication was 0.26 (0.572) use per month for 40 IU/kg and 0.31 (0.804) uses per month for 60 IU/kg.
Paediatric population
The safety and effectiveness of Berinert were evaluated in a subgroup of 11 patients 8 to <17 years of age, in the randomised, double-blind, placebo-controlled, crossover, routine prophylaxis trial (Study 3001) and the randomised, open-label, active treatment-controlled study (Study 3002). Results of subgroup analysis by age were consistent with overall study results.