CLINICAL PHARMACOLOGY
Mechanism Of Action
C1 esterase inhibitor is a normal constituent of human
plasma and belongs to the group of serine protease inhibitors (serpins) that
includes antithrombin III, alpha1-protease inhibitor, alpha2-antiplasmin, and
heparin cofactor II. As with the other inhibitors in this group, C1 esterase
inhibitor has an important inhibiting potential on several of the major cascade
systems of the human body, including the complement system, the intrinsic coagulation
(contact) system, the fibrinolytic system, and the coagulation cascade. Regulation
of these systems is performed through the formation of complexes between the
proteinase and the inhibitor, resulting in inactivation of both and consumption
of the C1 esterase inhibitor.
C1 esterase inhibitor, which is usually activated during
the inflammatory process, inactivates its substrate by covalently binding to
the reactive site. C1 esterase inhibitor is the only known inhibitor for the
subcomponent of the complement component 1 (C1r), C1s, coagulation factor XIIa,
and kallikrein. Additionally, C1 esterase inhibitor is the main inhibitor for
coagulation factor XIa of the intrinsic coagulation cascade.
HAE patients have low levels of endogenous or functional
C1 esterase inhibitor. Although the events that induce attacks of angioedema in
HAE patients are not well defined, it has been postulated that increased
vascular permeability and the clinical manifestation of HAE attacks may be
primarily mediated through contact system activation. Suppression of contact
system activation by C1 esterase inhibitor through the inactivation of plasma
kallikrein and factor XIIa is thought to modulate this vascular permeability by
preventing the generation of bradykinin.5
Administration of Berinert to patients with C1 esterase
inhibitor deficiency replaces the missing or malfunctioning protein in patients.
The plasma concentration of C1 esterase inhibitor in healthy volunteers is
approximately 270 mg/L.6
Pharmacokinetics
The pharmacokinetics of Berinert were evaluated in an
open-label, uncontrolled, singlecenter study in 40 subjects (35 adults and 5
children under 16 years of age) with either mild or severe HAE. All subjects
received a single intravenous injection of Berinert ranging from 500 IU to 1500
IU. Blood samples were taken during an attack-free period at baseline and for
up to 72 hours after drug administration. Pharmacokinetic parameters were
estimated using non-compartmental analysis (with or without baseline adjustment).
Table 6 summarizes the pharmacokinetic parameters in 35 adult subjects with
HAE.
Table 6: Pharmacokinetic Parameters of Berinert in
Adult Subjects with HAE by Non-compartmental Analysis (n=35)
Parameters |
Unadjusted for baseline |
Adjusted for baseline |
AUC(0-t) (hr x IU/mL)* |
27.5 ± 8.5 (15.7-44.7) |
12.8 ± 6.7 (3.9-34.7) |
CL (mL/hr/kg) |
0.60 ± 0.17 (0.34-0.96) |
1.44 ± 0.67 (0.43-3.85) |
Vss (mL/kg) |
18.6 ± 4.9 (11.1-27.6) |
35.4 ± 10.5 (14.1-56.1) |
Half-life (hrs) |
21.9 ± 1.7 (16.5-24.4) |
18.4 ± 3.5 (7.4-22.8) |
MRT (hrs) |
31.5 ± 2.4 (23.7-35.2) |
26.4 ± 5.0 (10.7-33.0) |
AUC: Area under the curve
CL: Clearance
Vss: Volume steady state
MRT: Mean residence time
*Based on a 15 IU/kg dose. Numbers in parenthesis are the range. |
Table 7 summarizes the pharmacokinetic parameters in 5
pediatric subjects (ages 6 through 13) with HAE. When adjusted for baseline,
compared to adults, the half-life of Berinert was shorter and clearance (on per
kg basis) was faster in this limited cohort of children. However, the clinical
implication of this difference is not known.
Table 7: Pharmacokinetic Parameters of Berinert in
Pediatric Subjects with HAE by Non-compartmental Analysis (n=5)
Parameters |
Unadjusted for baseline |
Adjusted for baseline |
AUC(0-t) (hr x IU/mL)* |
25.45 ± 5.8 (16.8-31.7) |
9.78 ± 4.37 (4.1-15.2) |
CL (mL/hr/kg) |
0.62 ± 0.17 (0.47-0.89) |
1.9 ± 1.1 (0.98-3.69) |
Vss (mL/kg) |
19.8 ± 4.0 (16.7-26.1) |
38.8 ± 8.9 (31.9-54.0) |
Half-life (hrs) |
22.4 ± 1.6 (20.3-24.4) |
16.7 ± 5.8 (7.4-22.5) |
MRT (hrs) |
32.3 ± 2.3 (29.3-35.2) |
24.0 ± 8.3 (10.7-32.4) |
AUC: Area under the curve
CL: Clearance
Vss: Volume steady state
MRT: Mean residence time
*Based on a 15 IU/kg dose. Numbers in parenthesis are the range. |
Studies have not been conducted to evaluate the
pharmacokinetics of Berinert in special patient populations identified by
gender, race, geriatric age, or the presence of renal or hepatic impairment.
Animal Toxicology And/Or Pharmacology
Acute intravenous toxicity of Berinert was performed in
mice at 1500, 3000, and 6000 IU/kg and in rats at 1000, 2000, and 3000 IU/kg.
Berinert was well tolerated and no signs of toxicity were observed up to the
highest dose administered.
Repeat intravenous dose toxicity was studied in a 14-day
repeat dose study in rats at doses of 20, 60, and 200 IU/kg/day. Berinert was
well tolerated and no toxicity was observed up to the highest dose
administered. No antibody response against C1 esterase inhibitor could be
demonstrated in this study after multiple dosing with Berinert.
In a safety pharmacology study, Berinert was administered
to beagle dogs intravenously at a cumulative dose of 3500 IU/kg. No adverse
effects were seen on the cardiovascular and respiratory system. There was a
drop in body temperature, reduced coagulation time, and a decrease in
thrombocyte aggregation.
Local intravenous tolerance of Berinert was evaluated in
rabbits at 1500 IU. No pathological changes were noted at the time of injection
or during the following 24 hours. No pathological signs were noted during
necropsy.
A study in pigs investigating cardioprotective effects of
C1 esterase inhibitor suggests a risk of thrombosis from intravenous
administration of C1 esterase inhibitor products at doses of 200 IU/kg;
however, in this model, cardioprotective effects were observed at a dose of 40
IU/kg.2
Clinical Studies
The safety and efficacy of Berinert in the treatment of
acute abdominal or facial attacksin subjects with hereditary angioedema were
demonstrated in a placebo-controlled, double-blind, prospective, multinational,
randomized, parallel-group, dose-finding, three-arm, clinical study, referred
to as the randomized clinical trial (RCT). The RCT assessed the efficacy and
safety of Berinert in 124 adult and pediatric subjects with C1 esterase
inhibitor deficiency who were experiencing an acute moderate to severe attack of
abdominal or facial HAE. Subjects ranged in age from six to 72 years of age;
67.7% were female and 32.3% were male; and approximately 90% were Caucasian.
The study objectives were to evaluate whether Berinert
shortens the time to onset of relief of symptoms of an abdominal or facial
attack compared to placebo and to compare the efficacy of two different doses
of Berinert. The time to onset of relief of symptoms was determined by the
subject's response to a standard question posed at appropriate time intervals
for as long as 24 hours after start of treatment, taking into account all
single HAE symptoms. In addition the severity of individual HAE symptoms was
assessed over time.
Subjects were randomized to receive a single 10 IU/kg
body weight dose of Berinert (39 subjects), a single 20 IU/kg dose of Berinert
(43 subjects), or a single dose of placebo (42 subjects) by slow intravenous
infusion (recommended to be given at a rate of approximately 4 mL per minute)
within 5 hours of an HAE attack. At least 70% of the subjects in each treatment
group were required to be experiencing an abdominal attack. If a subject experienced
no relief or insufficient relief of symptoms by 4 hours after infusion,
investigators had the option to administer a second infusion of Berinert (20
IU/ kg for the placebo group, 10 IU/kg for the 10 IU/kg group), or placebo (for
the 20 IU/kg group). This masked (blinded) “rescue study medication” was
administered to subjects and they were then followed until complete resolution
of symptoms was achieved. Adverse events were collected for up to 7 to 9 days
following the initial administration of Berinert or placebo.
In the rare case that a subject developed
life-threatening laryngeal edema after inclusion into the study, immediate
start of open-label treatment with a 20 IU/kg body weight dose of Berinert was
allowed.
All subjects who received confounding medication (rescue
medication) before symptom relief were regarded as “nonresponders.” Therefore,
time to onset of symptom relief was set at 24 hours if a subject received any
rescue medication (ie, rescue study medication, narcotic analgesics, non-narcotic
analgesics, anti-emetics, open-label C1 inhibitor, androgens at increased dose,
or fresh frozen plasma) between 5 hours before administration of blinded study
medication until time to onset of relief.
For the trial to be considered successful, the study
protocol specified the following criteria for the differences between the
Berinert 20 IU/kg and the placebo group:
- The time to onset of relief of symptoms of the HAE attack
had to achieve a one-sided p-value of less than 0.0249 for the final analysis,
and at least one of the following criteria had to demonstrate a trend in favor
of Berinert with a one-sided p-value of less than 0.1:
- The proportion of subjects with increased intensity of
clinical HAE symptoms between 2 and 4 hours after start of treatment with study
medication compared to baseline, or
- The number of vomiting episodes within 4 hours after
start of study treatment.
Subjects treated with 20 IU/kg body weight of Berinert
experienced a significant reduction (p=0.0016; “Wilcoxon Rank Sum test”) in
time to onset of relief from symptoms of an HAE attack as compared to placebo
(median of 48 minutes for Berinert 20 IU/kg body weight, as compared to a
median of > 4 hours for placebo). The time to onset of relief from symptoms
of an HAE attack for subjects in the 10 IU/kg dose of Berinert was not statistically
significantly different from that of subjects in the placebo group.
Figure 9 is a Kaplan-Meier curve showing the percentage
of subjects reporting onset of relief of HAE attack symptoms as a function of
time. Individual time points beyond 4 hours are not presented on the graph,
because the protocol permitted blinded rescue medication, analgesics, and/or
anti-emetics to be administered starting 4 hours after randomized blinded study
medication had been administered.
Figure 9: Time to Onset of Symptom Relief With
Imputation to > 4 Hours for Subjects Who Received any Rescue Medication* or
Non-narcotic Analgesics Before Start of Relief
* Included rescue study medication (as blinded C1
inhibitor or placebo given as rescue medication), open-label C1 inhibitor,
narcotic and non-narcotic analgesics, anti-emetics, androgens at increased
dose, or fresh frozen plasma.
In addition, the efficacy of Berinert 20 IU/kg body
weight could be confirmed by observing a reduction in the intensity of single
HAE symptoms at an earlier time compared to placebo. For abdominal attacks
Figure 10 shows the time to start of relief of the last symptom to improve that
was already present at baseline. Pre-defined abdominal HAE symptoms included
pain, nausea, vomiting, cramps and diarrhea. Figure 11 shows the respective
time to start of relief of the first symptom to improve that was already
present at baseline.
Figure 10: Time to Start of Relief of the Last Symptom
to Improve (Abdominal Attacks) with Imputation to > 4 Hours for Subjects Who
Received any Rescue Medication* Before Start of Relief
* Included rescue study medication (as blinded C1
inhibitor or placebo given as rescue medication), open-label C1 inhibitor,
narcotic and non-narcotic analgesics, anti-emetics, androgens at increased
dose, or fresh frozen plasma.
Figure 11: Time to Start of Relief of the First Symptom
to Improve (Abdominal Attacks) With Imputation to > 4 Hours for Subjects Who
Received Any Rescue Medication* Before Start of Relief
* Included rescue study medication (as blinded C1
inhibitor or placebo given as rescue medication), open-label C1 inhibitor,
narcotic and non-narcotic analgesics, anti-emetics, androgens at increased
dose, or fresh frozen plasma.
For facial attacks, single HAE symptoms were recorded. In
addition, photos were taken at pre-determined time points and assessed by the
members of an independent Data Safety Monitoring Board (DSMB), who were blinded
as to treatment, center and other outcome measures. The change in the severity
of the edema when compared to baseline was assessed on a scale with outcomes
“no change”, “better”, “worse” and “resolved”.
Figure 12 shows the time to start of relief from serial facial photographs by
DSMB assessment.
Figure 12: Time to Start of Relief From Serial Facial
Photographs*
* Includes facial attacks in subjects with concomitant
abdominal attacks.
Table 8 compares additional endpoints, including changes
in HAE symptoms and use of rescue medication in subjects receiving Berinert at
20 IU/kg body weight and placebo.
Table 8: Changes in HAE Symptoms and Use of Rescue
Medication in Subjects Receiving Berinert 20 IU/kg Body Weight vs. Placebo
Additional Endpoints |
Number (%) of Subjects Berinert 20 IU/kg Body Weight Group
(n=43) |
Number (%) of Subjects Placebo Group
(n=42) |
Onset of symptom relief within 60 minutes after administration of study medication (post-hoc) |
27 (62.8%) |
11 (26.2%) |
Onset of symptom relief within 4 hours after administration of study medication |
30 (69.8%) |
18 (42.9%) |
Number of vomiting episodes within 4 hours after start of study treatment* |
6 episodes |
35 episodes |
Worsened intensity of clinical HAE symptoms between 2 and 4 hours after administration of study medication compared to baseline† |
0 (0%) |
12 (28.6%) |
Number (percent) of combined abdominal and facial attack subjects receiving rescue study medication, analgesics, or antiemetics at any time prior to initial relief of symptoms |
13 (30.2%) |
23 (54.8%) |
At least one new HAE symptom not present at baseline and starting within 4 hours after administration of study medication |
2 (4.6%) |
6 (14.3%) |
* p-value = 0.033
† p-value = 0.00008 |
Both the proportion of subjects with increased intensity
of clinical HAE symptoms between 2 and 4 hours after start of treatment
compared to baseline, and the number of vomiting episodes within 4 hours after
start of study treatment demonstrated trends in favor of Berinert in comparison
to placebo (p-values < 0.1). Tables 9 through 12 present additional
information regarding responses to treatment.
Table 9: Proportion of Subjects Experiencing Start of
Self-Reported Relief of Symptoms by 4 Hours by Attack Type
Attack Type |
Berinert 20 IU/kg Body Weight (Abdominal Subjects = 34) (Facial Subjects = 9) (Other subjects = 0) |
Placebo Group (Abdominal Subjects = 33) (Facial Subjects = 8) (Other subjects = 1)* |
Abdominal |
24 (70.6%) |
15 (45.5%) |
Facial |
6 (66.7%) |
3 (37.5%) |
* Laryngeal edema initially classified as facial edema. |
Table 10: Proportion of Subjects Experiencing
Reduction in Severity of at Least One Individual HAE Attack Symptom by 4 Hours
Attack Type |
Berinert 20 IU/kg Body Weight (Abdominal Subjects = 34) (Facial Subjects = 9) |
Placebo Group (Abdominal Subjects = 33) (Facial Subjects = 8) |
Abdominal |
33 (97.1%) |
29 (87.9%) |
Facial |
6 (66.7%) |
4 (50%) |
Table 11: Proportion of Subjects with Facial Attacks
Demonstrating Improvement in Serial Facial Photographs by 4 hours*
Attack Type |
Berinert 20 IU/kg Body Weight (Subjects = 9) |
Placebo Group (Subjects = 8) |
Facial |
7 (77.8%) |
2 (25%) |
* Based on masked (blinded) evaluation by data safety
monitoring board. |
Table 12: Proportion of Subjects with Abdominal and
Facial Attacks Receiving Rescue Study Medication at any Time Prior to Complete
Relief of Symptoms
Attack Type |
Berinert 20 IU/kg Body Weight (Abdominal Subjects = 34) (Facial Subjects = 9) |
Placebo Group (Abdominal Subjects = 33) (Facial Subjects = 8) |
Abdominal |
7 (20.6%) |
17 (51.5%) |
Facial |
1 (11.1%) |
6 (75%) |
No subjects treated with Berinert at 20 IU/kg body weight
reported worsening of symptoms at 4 hours after administration of study
medication compared to baseline. The study demonstrated that the Berinert 20
IU/kg body weight dose was significantly more efficacious than the Berinert 10
IU/kg body weight dose or placebo.
Open-Label Extension Study
Berinert was evaluated in a prospective, open-label,
uncontrolled, multicenter extension study conducted at 15 centers in the US and
Canada in subjects who had participated in the RCT study for the treatment of
acute abdominal or facial attacks in subjects with hereditary angioedema.
The purpose of this extension study was to provide
Berinert to subjects who had participated in the RCT study and who experienced
any type of subsequent HAE attack (ie, abdominal, facial, peripheral, or
laryngeal).
The safety analysis of the open-label extension study
included a total of 57 subjects (19 males and 38 females, age range: 10 to 53
years) with 1085 HAE attacks treated with 20 IU/kg body weight dose of Berinert
per attack, who were observed at the study site until onset of relief of HAE
symptoms, and were followed up for adverse reactions for 7 to 9 days following
treatment of each HAE attack [see ADVERSE REACTIONS].
During the extension study, 51 subjects experienced 747
abdominal attacks, 21 subjects experienced 51 facial attacks, 30 subjects
experienced 235 peripheral attacks, and 16 subjects experienced 48 laryngeal
attacks. Some study subjects may have experienced HAE attacks in more than one
location.
An analysis of laryngeal HAE attacks showed that the
median time to initial onset of symptom relief and median time to complete
resolution in the per-attack analysis were 0.25 hours and 8.4 hours,
respectively (Table 13), which were the shortest times among the various attack
locations.
Table 13: Time to Initial Onset of Symptom Relief and
Time to Complete Resolution of HAE Symptoms for Laryngeal Attacks
Statistic |
Laryngeal
(n=48) |
Time to initial onset of symptom relief [hours] |
Median (range) |
0.25 (0.10 - 1.25) |
95% CI for median |
[0.23; 0.42] |
Time to complete resolution of HAE symptoms [hours] |
Median (range) |
8.4 (0.6 - 61.8*) |
95% CI for median |
[6.2; 21.5] |
CI = confidence interval
HAE = hereditary angioedema
N = number of attacks
* The maximum time to complete resolution of 61.8 hours was an imputed value.
Subject 29301 had 2 laryngeal attacks with missing times to complete resolution
of HAE symptoms, which were imputed with the maximum time to complete
resolution of HAE symptoms observed for an abdominal attack in this subject. |
There were no clinically relevant or consistent data
suggesting that gender, age group, race/ethnic group, type of HAE, routine use
of androgens, or presence of detectable anti-C1 Esterase Inhibitor antibodies
had an effect on the time to initial or complete relief of symptoms following
Berinert.
The prospective open-label extension study demonstrated
that, in comparison to untreated historical control data retrospectively
collected at a study center in Germany over a 20 year period7, the
Berinert 20 IU/kg body weight dose appeared to be effective in ameliorating
laryngeal HAE attacks by achieving complete resolution of HAE symptoms within
24 hours from attack onset in the majority of subjects. The treatment effects
observed with Berinert in the extension study are consistent with the findings from
the placebo-controlled efficacy trial.
REFERENCES
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Inhibitor During Reperfusion of Ischemic Myocardium: Dose-Related Beneficial
Versus Detrimental Effects. Circulation. 2001;104:3125-3131.
5. Davis AE, The pathophysiology of hereditary
angioedema. Clin Immunol. 2005;114:3-9.
6. Nuijens JH, Eerenberg-Belmer AJM, Huijbregts CCM, et
al. Proteolytic inactivation of plasma C1 inhibitor in sepsis. J Clin Invest.
1989;84:443-450.
7. Bork K, Barnstedt SE. Treatment of 193 Episodes of
Laryngeal Edema with C1 Inhibitor Concentrate in Patients with Hereditary
Angioedema. Arch Intern Med. 2001;161:714-718.