CLINICAL PHARMACOLOGY
Mechanism Of Action
Protein C is the precursor of a vitamin K-dependent anticoagulant glycoprotein (serine protease) that is
synthesized in the liver. see DOSAGE AND ADMINISTRATION: Initiation Of Vitamin K Antagonists. It is converted by the thrombin/thrombomodulin-complex on the endothelial cell surface to
activated Protein C (APC). APC is a serine protease with potent anticoagulant effects, especially in the
presence of its cofactor protein S. APC exerts its effect by the inactivation of the activated forms of
factors V and VIII, which leads to a decrease in thrombin formation. APC has also been shown to have
profibrinolytic effects.
The Protein C pathway provides a natural mechanism for control of the coagulation system and
prevention of excessive procoagulant responses to activating stimuli. A complete absence of protein C
is not compatible with life. A severe deficiency of this anticoagulant protein causes a defect in the
control mechanism and leads to unchecked coagulation activation, resulting in thrombin generation and
intravascular clot formation with thrombosis.
Pharmacodynamics
In clinical studies, the intravenous administration of CEPROTIN demonstrated a temporary increase,
within approximately half an hour of administration, in plasma levels of APC. Replacement of protein C
in protein C-deficient patients is expected to control or, if given prophylactically, to prevent thrombotic
complications.
Pharmacokinetics
Table 3 provides pharmacokinetic results for asymptomatic and symptomatic subjects with protein C
deficiency.
Table 3: Pharmacokinetics of CEPROTIN in Subjects with Severe
Congenital Protein C Deficiency
PK parameter |
N |
Median |
95% CI for
median |
Min |
Max |
Cmax[IU/dL] |
21 |
110 |
106 to 127 |
40 |
141 |
Tmax[h] |
21 |
0.50 |
0.50 to 1.05 |
0.17 |
1.33 |
Incremental recovery
[(IU/dL)/(IU/kg)] |
21 |
1.42 |
1.32 to 1.59 |
0.50 |
1.76 |
Initial half-life [h] |
21 |
7.8 |
5.4 to 9.3 |
3.0 |
36.1 |
Terminal half-life [h] |
21 |
9.9 |
7.0 to 12.4 |
4.4 |
15.8 |
Half-life by the noncompartmental
approach [h] |
21 |
9.8 |
7.1 to 11.6 |
4.9 |
14.7 |
AUC0-Infinity[IU*h/dL] |
21 |
1500 |
1289 to 1897 |
344 |
2437 |
MRT [h] |
21 |
14.1 |
10.3 to 16.7 |
7.1 |
21.3 |
Clearance [dL/kg/h] |
21 |
0.0533 |
0.0428 to
0.0792 |
0.0328 |
0.2324 |
Volume of distribution
at steady state [dL/kg] |
21 |
0.74 |
0.70 to 0.89 |
0.44 |
1.65 |
Cmax= Maximum concentration after infusion; Tmax= Time at maximum
concentration; AUC0-Infinity= Area under the curve from 0 to infinity; MRT
= Mean residence time; and Incremental recovery = Maximum increase in
Protein C concentration following infusion divided by dose |
The protein C plasma activity was measured by chromogenic and/or clotting assay. The maximum
plasma concentrations (Cmax ) and area under the plasma concentration-time curve (AUC) appeared to
increase dose-linearly between 40 and 80 IU/kg. The median incremental recovery was 1.42
[(IU/dL)/(IU/kg)] after intravenous administration of CEPROTIN. The median half-lives, based on noncompartmental
method, ranged from 4.9 to 14.7 hours, with a median of 9.8 hours. In patients with acute
thrombosis, both the increase in protein C plasma levels as well as half-life may be considerably
reduced. No formal study or analysis has been performed to evaluate the effect of covariates such as
race and gender on the pharmacokinetics of CEPROTIN.
The pharmacokinetic profile in pediatric patients has not been formally assessed. Limited data suggest
that the pharmacokinetics of CEPROTIN may be different between very young children and adults. The
systemic exposure (Cmax and AUC) may be considerably reduced due to a faster clearance, a larger
volume of distribution, and/or a shorter half-life of protein C in very young children than in older
subjects. Consider this fact when a dosing regimen for children is determined. Doses should be
individualized based upon protein C activity levels. see DOSAGE AND ADMINISTRATION: Protein C
Activity Monitoring.
Animal Toxicology And/Or Pharmacology
Safety Pharmacology
Cardio-respiratory studies performed in dogs evaluating mean arterial pressure, cardiac output,
systemic vascular resistance, heart rate, QT interval changes, pulmonary artery pressure, respiratory
rate and respiratory minute volume demonstrated no adverse effects at a maximum dose of 500 IU/kg.
Anaphylactoid reactions as determined by measurement of bronchospastic activity in guinea pigs
demonstrated no adverse effects at the maximum dose of 300 IU/kg. Thrombogenic potential was
evaluated in rabbits using the Wessler stasis model and demonstrated no adverse effects at 200 IU/kg.
Overall, safety pharmacology studies evaluating cardio-respiratory function, acute dose anaphylactoid
potential and thrombogenicity demonstrated no adverse effects in a range of doses from 1.6 to 4.2 times
the maximum single human dosage per kilogram body weight.
Acute Dose Toxicity
Toxicity testing in rats and mice following single dosing of 2000 IU/kg or 1500 IU/kg, respectively,
demonstrated no adverse clinical effects or gross pathology at 14 days post dosing.
Repeated Dose Toxicity
Studies were not conducted to evaluate repeated-dose toxicity in animals. Prior experience with
CEPROTIN has suggested immunogenic response in heterologous species following repeated dosing
of this human derived protein. Thus, the long-term toxicity potential of CEPROTIN following repeated
dosing in animals is unknown.
Local Tolerance Testing
Investigation of route of injection tolerance demonstrated that CEPROTIN did not result in any local
reactions after intravenous, intra-arterial injections of 500 IU/kg (5 mL) and paravenous injections of
100 IU/kg (1 mL) in rabbits.
Citrate Toxicity
CEPROTIN contains 4.4 mg of Trisodium Citrate Dihydrate (TCD) per mL of reconstituted product.
Studies in mice evaluating 1000 IU vials reconstituted with 10 mL vehicle followed by dosing at 30
mL/kg (132 mg/kg TCD) and 60 mL/kg (264 mg/kg TCD) resulted in signs of citrate toxicity (dyspnea,
slowed movement, hemoperitoneum, lung and thymus hemorrhage and renal pelvis dilation).
Clinical Studies
Pivotal Study
This was a multi-center, open-label, non-randomized, phase 2/3 study in 3 parts which evaluated the
safety and efficacy of CEPROTIN in subjects with severe congenital protein C deficiency for the (ondemand)
treatment of acute thrombotic episodes, such as purpura fulminans (PF), warfarin-induced skin
necrosis (WISN) and other thromboembolic events, and for short-term or long-term prophylaxis.
Eighteen subjects (9 male and 9 female), ages ranging from 0 (newborn) to 25.7 years participated in this
study.
The clinical endpoint of the study was to assess whether episodes of PF and/or other thromboembolic
events were treated effectively, effectively with complications, or not treated effectively. Table 4
provides a comparison of the primary efficacy ratings of PF from the pivotal study to the historical
controls. Inadequate data is available for treatment of WISN.
Table 4: Comparison of Primary Efficacy Rating of Episodes of Purpura
Fulminans in the Protein C Concentrate (Human) Pivotal Study of
Historical Controls
|
Protein C Concentrate
(Human) |
Historical Controls |
Episode
Type |
Primary Efficacy
Rating |
N |
% |
N |
% |
Purpura
Fulminans |
Effective |
17 |
94.4 |
11 |
52.4 |
Effective with
Complication |
1 |
5.6 |
7 |
33.3 |
Not Effective |
0 |
0.0 |
3 |
14.3 |
Total |
18 |
100 |
21 |
100 |
Of 18 episodes of PF (6 severe, 11 moderate, 1 mild) treated with CEPROTIN for the primary efficacy
rating, 17 (94.4%) were rated as effective, and 1 (5.6%) was rated as effective with complications; none
(0%) were rated not effective. When compared with the efficacy ratings for 21 episodes of PF
(historical control group), subjects with severe congenital protein C deficiency were more effectively
treated with CEPROTIN than those treated with modalities such as fresh frozen plasma or conventional
anticoagulants.
Table 5 provides a summary of the secondary treatment ratings for treatment of skin lesions and other
thrombotic episodes from part one of the study.
Table 5: Summary of Secondary Treatment Ratings for Treatment of
Skin Lesions and Other Thrombotic Episodes - Protein C Concentrate
(Human) Pivotal Study Part 1
|
Purpura Fulminans
Skin Necrosis |
Other
Thrombotic
Events |
Total |
Mild |
Moderate |
Severe |
Total |
Total |
|
Rating
Category |
N |
% |
N |
% |
N |
% |
N |
% |
N |
% |
N |
% |
Excellent |
1 |
5.6 |
7 |
38.9 |
5 |
27.8 |
13 |
72.2 |
4 |
80.0 |
17 |
73.9 |
Good |
0 |
0.0 |
4 |
22.2 |
0 |
0.0 |
4 |
22.2 |
1 |
20.0 |
5 |
21.7 |
Fair |
0 |
0.0 |
0 |
0.0 |
1 |
5.6 |
1 |
5.6 |
0 |
0 |
1 |
4.3 |
Total |
1 |
5.6 |
11 |
61.1 |
6 |
33.3 |
18 |
100.0 |
5 |
100.0 |
23 |
100.0 |
N = Number of episodes |
In a secondary efficacy rating, 13 (72.2%) of the 18 episodes of PF treated with CEPROTIN were rated
as excellent, 4 (22.2%) were rated as good, and 1 (5.6%) episode of severe PF was rated as fair; all
were rated as effective. Four (80%) of the 5 episodes of venous thrombosis had treatment ratings of
excellent, while 1 (20%) was rated as good.
CEPROTIN was also demonstrated to be effective in reducing the size and number of skin lesions. Nonnecrotic
skin lesions healed over a maximum 12-day (median 4-day) period and necrotic skin lesions
healed over a maximum 52-day (median 11-day) period of CEPROTIN treatment, as shown in Table 6.
Table 6: Number of Days to Complete Healing of Skin Lesions in the
Protein C Concentrate (Human) Pivotal Study
Lesion
Type |
Number of
Episodes
(Number of
Subjects ) |
Mean |
Median |
Minimum |
Maximum |
Nonnecrotic |
16 (9 subjects) |
4.6 |
4.0 |
1 |
12 |
Necrotic |
7 (5 subjects) |
21.1 |
11.0 |
5 |
52 |
Changes in the extent of venous thrombus were also measured for the 5 thromboembolic episodes.
CEPROTIN prevented an increase in the extent of thrombus during 4 (80%) of the thromboembolic
episodes by Day 3 of treatment, and 1 (20%) episode by Day 5 of treatment.
All seven of the short-term prophylaxis treatments with CEPROTIN were free of complications of PF
or thromboembolic events, as shown in Table 7.
Table 7: Summary of Complications During Short Term Prophylaxis in
the Protein C Concentrate (Human) Pivotal Study
Reason for
Treatment |
Number of
Treatments |
Presentation
of Purpura Fulminans
During
Treatment
Episodes |
Thromboembolic Complications
During
Treatment
Episode |
Number of Treatments
Free of
Complications |
N |
% |
N |
% |
N |
% |
Anticoagulation
Therapy |
3 |
0 |
0.0 |
0 |
0.0 |
3 |
100.0 |
Surgical
Procedure |
4 |
0 |
0.0 |
0 |
0.0 |
4 |
100.0 |
Total |
7 |
0 |
0.0 |
0 |
0.0 |
7 |
100.0 |
No episodes of PF occurred in four subjects ranging from 42 to 338 days of long-term prophylactic
treatment with CEPROTIN, as shown in Table 8. When not on prophylactic treatment and receiving
CEPROTIN on-demand, the same four subjects experienced a total of 13 (median of 3) episodes of PF
over a range of 19 to 323 days. The time to first episode of PF after exiting from long-term prophylaxis
treatment ranged from 12 to 32 days for these four subjects.
Table 8: Number and Rate of Episodes of Skin Lesions or Thrombosis for Four
Subjects Who Received Long-Term Prophylactic Treatment and Were Treated
On-Demand in the Protein C Concentrate (Human) Pivotal Study
Summary
Statistic |
Long-Term Prophylactic
Treatment |
While On-Demand* |
Time to
First
Episode
After
Existing
Long Term
Prophylaxis |
Number
of
Episodes
per
Subject |
Number of
Days
Receiving
Prophylactic
Treatment |
Monthly
Rate of
Episodes |
Number
of
Episodes
per
Subject |
Number
of Days
Not
Receiving
Study
Drug |
Monthly
Rate of
Episodes |
Mean |
0 |
229 |
0.0 |
3.3 |
165 |
1.91 |
23.3 |
Median |
0 |
268 |
0.0 |
3.0 |
159 |
0.49 |
24.5 |
Minimum |
0 |
42 |
0.0 |
1.0 |
19 |
0.25 |
12.0 |
Maximum |
0 |
338 |
0.0 |
6.0 |
323 |
6.40 |
32.0 |
* Total number of episodes while subjects were On-Demand was 13 |
Retrospective Analysis
A retrospective study to capture dosing information and treatment outcome data in subjects with severe
congenital protein C deficiency who were treated with CEPROTIN under an emergency use IND was
also conducted. Eleven subjects (6 male and 5 female), ages ranging from 2.1 to 23.8 years participated
in this study.
There were 28 acute episodes of PF/WISN and vascular thrombus reported in which time to resolution
ranged from 0 to 46 days. The treatment outcome for these episodes was rated effective in all cases
except one.