CLINICAL PHARMACOLOGY
Mechanism Of Action
ALPHANATE contains antihemophilic factor (FVIII) and von
Willebrand factor (VWF), constituents of normal plasma. FVIII is an essential
cofactor in activation of factor X leading to formation of thrombin and fibrin.
VWF promotes platelet aggregation and platelet adhesion on damaged vascular
endothelium; it also serves as a stabilizing carrier protein for the procoagulant
protein FVIII.12, 13
After administration, ALPHANATE temporarily replaces the
missing coagulation factor VIII and von Willebrand factor needed for effective
hemostasis.
Pharmacokinetics
Pharmacokinetics In Hemophilia A
Following the administration of ALPHANATE during clinical
trials, the mean in vivo half-life of FVIII observed in 12 adult subjects with
severe hemophilia A was 17.9 ± 9.6 hours. In this same study, the in vivo recovery
was 96.7 ± 14.5% at 10 minutes postinfusion. Recovery at 10 minutes post-infusion
was also determined as 2.4 ± 0.4 IU FVIII rise/dL plasma per IU FVIII
infused/kg body weight.
Pharmacokinetics In Von Willebrand Disease (VWD)
A pharmacokinetic crossover study was conducted in 14
non-bleeding subjects with VWD (1 type 1, 2 type 2A, and 11 type 3) comparing
the pharmacokinetics of ALPHANATE (A-SD/HT) and an earlier formulation,
ALPHANATE (A-SD). Subjects received, in random order at least seven days apart,
a single intravenous dose of each product, 60 IU VWF:RCo/kg (75 IU VWF:RCo/kg in
subjects younger than 18 years of age). Pharmacokinetic parameters were similar
for the two products and indicated that they were biochemically equivalent.
Pharmacokinetic analysis of ALPHANATE (A-SD/HT) in the 14 subjects revealed the
following results: the median plasma levels (% normal) of VWF:RCo rose from 10
IU/dL (range: 10 to 27 IU/dL) at baseline to 206 IU/ dL (range: 87 to 440
IU/dL) 15 minutes post-infusion; median plasma levels of FVIII:C rose from 5
IU/dL (range: 2 to 114 IU/dL) to 206 IU/dL (range: 110 to 421 IU/dL). The
median bleeding time (BT) prior to infusion was 30 minutes (mean, 28.8 ± 4.41
minutes; range: 13.5 to 30 minutes), which shortened to 10.38 minutes (mean,
10.4 ± 3.2 minutes; range: 6 to 16 minutes) 1 hour post-infusion.
Following infusion of ALPHANATE (A-SD/HT), the median
half-lives for VWF:RCo, FVIII:C and VWF:Ag were 6.91 hours (range: 3.8 to 16.22
hours), 20.92 hours (range: 7.19 to 32.2 hours), and 12.8 hours (range: 10.34
to 17.45 hours), respectively. The median incremental in vivo recoveries of
VWF:RCo and FVIII:C were 3.12 (IU/dL)/(IU/kg) [range: 1.28 to 5.73
(IU/dL)/(IU/kg)] for VWF:RCo and 1.95 (IU/dL)/(IU/kg) [range: 1.33 to 3.32
(IU/dL)/(IU/kg)] for FVIII:C. The pharmacokinetic data in VWD are summarized in
Table 4.
Table 4: Pharmacokinetic data in VWD
Parameter |
Plasma VWF:RCo (Mean ± SD) |
Plasma FVIII:C (Mean ± SD) |
Plasma VWF:Ag (Mean ± SD) |
Number of subjects |
14 |
14 |
14 |
Mean plasma levels (IU/dL) |
Baseline |
11.86 ± 4.97 |
21.00 ± 33.83 |
- |
15 minutes post infusion |
215.50 ± 101.70 |
215.29 ± 94.26 |
- |
T½ (Half-life in hours) |
7.67 ± 3.32 |
21.58 ± 7.79 |
13.06 ± 2.20 |
Incremental in vivo recovery in (IU/dL)/(IU/kg) |
3.29 ± 1.46 |
2.13 ± 0.58 |
- |
Following infusion of both ALPHANATE (A-SD) and ALPHANATE
(A-SD/HT), an increase in the size of VWF multimers was seen and persisted for
at least 24 hours. The shortening of the BT was transient, lasting less than 6
hours following treatment and did not correlate with the presence of large and
intermediate size VWF multimers.14
Clinical Studies
In a prospective, multi-center clinical study, 37
subjects with VWD (6 Type 1, 19 Type 2, 12 Type 3) underwent 59 surgical
procedures for which ALPHANATE (A-SD) or ALPHANATE (A-SD/HT) was administered
[21 subjects received ALPHANATE (A-SD), 18 received ALPHANATE (A-SD/HT), and 2 received
both products] for bleeding prophylaxis (see Table 5). An initial pre-operative
infusion of 60 IU VWF:RCo/kg (75 IU VWF:RCo/kg for subjects less than 18 years
of age), was administered one hour before surgery. A blood sample was obtained
15 minutes after the initial infusion for the determination of the plasma
FVIII:C level. The level had to equal or exceed 100% of normal for an operation
to proceed. No cryoprecipitate or alternative FVIII product was administered
during these surgical procedures. Platelets were required in two subjects. The
protocol permitted intraoperative infusions of ALPHANATE (A-SD) and ALPHANATE
(A-SD/HT) at 60 IU VWF:RCo/kg (75 IU VWF:RCo/kg for subjects less than 18 years
of age) to be administered as required according to the judgment of the
investigator.
Table 5: Number of and Types of Surgical Procedures
Parameter |
Treatment with ALPHANATE |
Total |
Type of Surgical Procedure |
A-SD |
A-SD/HT |
Number of Subjects |
21 |
18 |
37^ |
Dental |
14 |
6 |
20 |
Dermatologic |
1 |
1 |
2 |
Gastrointestinal |
4 |
4 |
8 |
Gastrointestinal (diagnostic) |
6 |
0 |
6 |
Genitourinary |
0 |
2 |
2 |
Gynecologic |
2 |
1 |
3 |
Head and neck |
1 |
1 |
2 |
Orthopedic |
4 |
3 |
7 |
Vascular |
3 |
6 |
9 |
Total number of procedures |
35 |
24 |
59 |
^ Two subjects received both preparations; the total
number of subjects is therefore less than the sum of the columns. |
Post-operative infusions at doses of 40 to 60 IU
VWF:RCo/kg (50 to 75 IU VWF:RCo/kg for pediatric subjects) were administered at
8 to 12-hour intervals until healing had occurred. For maintenance of secondary
hemostasis (after primary hemostasis was achieved), the dose was reduced after
the third post-operative day. [see DOSAGE AND ADMINISTRATION].
Overall, in the surgical procedures using either product,
the BT at 30 minutes post-infusion was fully corrected in 18 (32.7%) cases,
partially corrected in 24 (43.6%) cases, not corrected in 12 (21.8%) cases, and
was not done in one case (1.8%). Overall, the mean blood loss was lower than
predicted prospectively. Surgical infusion summary data are included in Table 6.
Table 6: Prophylaxis with ALPHANATE (A-SD) and/or
ALPHANATE (A-SD/HT) in Surgery
Parameter |
A-SD |
A-SD/HT |
Total |
Number of subjects |
21 |
18 |
37* |
Number of surgical procedures |
35 |
24 |
59 |
Median number of infusions per surgical procedure (range) |
3
(1-13) |
4
(1-18) |
4
(1-18) |
Median dosage IU VWF:RCo/kg |
Infusion #1 (range) |
59.8
(19.8-75.1) |
59.9
(40.6-75.0) |
59.9
(19.8-75.1) |
Infusion ≥ #2 combined (range) |
40.0
(4.5-75.1) |
40.0
(10.0-63.1) |
40.0
(4.5-75.1) |
* Two subjects received both products. |
Additionally, surgical procedures using ALPHANATE SD/HT
only were categorized as major, minor or invasive procedures according to
definitions used in the study. The outcome of each surgery was evaluated
according to a clinical rating scale (excellent, good, poor or none) and was considered
successful if the outcome was excellent or good.
Study results also were evaluated independently by two
referees with clinical experience in this field in the same way (surgery
categorization and outcome of each surgery according to a clinical rating
scale). There was a high level of agreement between the referee evaluations and
the analyzed outcome data, with a decrease of only a single success in
achieving hemostasis (21/24 [referees evaluation] vs. 22/24 [investigators
evaluation]).
A retrospective, multi-center study was performed to
assess the efficacy of ALPHANATE (A-SD/ HT) as replacement therapy in
preventing excessive bleeding in subjects with congenital VWD undergoing
surgical or invasive procedures, for whom DDAVP was ineffective or inadequate.
A total of 61 surgeries/procedures in 39 subjects were evaluated.15
Of the 39 subjects, 18 had Type 1 VWD (46.2%); 12
subjects (30.8%) had Type 2 VWD, and 9 subjects (23.1%) had Type 3 VWD. Median
age was 40 years; approximately one-half of the subjects were male.
The primary efficacy variable was the overall treatment
outcome for each surgical or invasive procedure, as rated by the investigator
using a 4-point verbal rating scale (VRS): “excellent,” “good,” “poor,” or
“none (no indication of efficacy).” The categorization of the replacement treatment
outcome was based upon the investigator's clinical experience and defined in Table
7.
Table 7: Rating Scale and Clinical Efficacy of
ALPHANATE Therapy
Rating |
Clinical Efficacy* |
Hemostasis |
Dosing |
Excellent |
Hemostasis not different from that expected for subjects without known bleeding disorders. |
No upward dosage adjustment for ALPHANATE replacement therapy. |
Good |
Hemostasis slightly inferior from that expected for subjects without known bleeding disorders but judged as not clinically relevant. |
Minor upward dosage adjustment for ALPHANATE replacement therapy. |
Poor |
Less hemostasis than expected for subjects without known bleeding disorders attributed to vWD despite ALPHANATE replacement therapy. |
Relevant upward dosage adjustment for ALPHANATE replacement therapy. No need for alternative therapy. |
None |
Severe bleeding attributed to vWD despite ALPHANATE replacement therapy. |
Relevant upward dosage adjustment for ALPHANATE replacement therapy and/or need for alternative unexpected therapy. |
* The efficacy assessment period included the entire
perioperative period. |
In addition, an independent referee committee was convened
to evaluate the efficacy outcomes. More than 90% of the surgical outcomes
received an investigator and referee's overall and daily rating of “effective”
(“excellent” or “good”) in achieving hemostasis/preventing bleeding. The
majority of ratings were considered “excellent” ( ≥ 81.3% in each VWD
type). Nine Type 3 subjects underwent 1 major and 15 minor procedures. Two
procedures (1 major and 1 minor) in 1 subject with Type 3 VWD received an
overall efficacy rating of “none,” and one minor procedure in a subject with
Type 2 VWD received an overall efficacy rating of “poor.”
REFERENCES
12. Hoyer, L.W. The Factor VIII Complex: Structure and
Function. Blood 1981; 58:1-13.
13. Meyer, D., Girma, J-P. von Willebrand Factor:
Structure and Function. Thrombosis and Haemostasis 1993; 70:99-104.
14. Mannucci, P.M., Chediak, J., Hanna, W. Byrnes, J.J.,
Kessler, C.M., Ledford, M., Retzios, A.D., Kapelan, B.A., Gallagher, P.,
Schwartz, R.S., and the Alphanate Study Group. Treatment of von Willebrand's
Disease (VWD) with a high purity factor VIII concentrate: Dissociation between correction
of the bleeding time (BT), VWF multimer pattern, and treatment efficacy. Blood 1999;
94 (Suppl 1, Part 2 of 2):98b.
15. Rivard, G.E., Aledort, L., et al. Efficacy of factor
VIII/von Willebrand factor concentrate Alphanate in preventing excessive
bleeding during surgery in subjects with von Willebrand disease. Haemophilia 2008;
14, 271-275.