CLINICAL PHARMACOLOGY
Mechanism Of Action
ESPEROCT, a glycopegylated form of recombinant anti-hemophilic factor, temporarily replaces the missing coagulation Factor VIII needed for effective hemostasis in congenital hemophilia A patients. The Factor VIII in ESPEROCT is conjugated to a 40-kDa polyethylene glycol molecule which increases the half-life and decreases the clearance compared to the non-pegylated molecule.
Pharmacodynamics
The administration of ESPEROCT increases plasma levels of Factor VIII and can temporarily correct the coagulation defect in hemophilia A patients, as reflected by a decrease in activated partial thromboplastin time (aPTT).
Pharmacokinetics
All pharmacokinetic studies with ESPEROCT were conducted in previously treated subjects with severe hemophilia A (Factor VIII<1%). In total, 129 single-dose pharmacokinetic profiles of ESPEROCT were evaluated in 86 subjects (including 24 pediatric subjects, 1-<12 years).
Table 3 shows data for subjects who each received a single dose of 50 IU/kg. The plasma samples were analyzed using the one-stage clotting assay. There was a trend of increasing incremental recovery and AUC, and decreasing clearance, with age.
Table 3: Single-dose PK parameters of ESPEROCT 50 IU/kg, by age, using one-stage clotting assay (geometric mean (CV%))
PK Parameter
No. of subjects |
1 to <6 years
N=12 |
6 to <12 years
N=10 |
12 to <18 years
N=3 |
>18 years
N=42 |
No. of profiles |
12 |
10 |
5 |
78 |
IR (IU/dL) per IU/kg)a |
1.82 (32) |
1.67 (22) |
2.45 (16) |
2.53 (24) |
FVIII recovery (IU/dL)a |
103.2 (27) |
98.7 (18) |
117.7 (14) |
130.4 (26) |
t1/2 (hours) |
14.7 (27) |
13.8 (32) |
17.4 (39) |
21.7 (33) |
AUCinf (IU*hour/dL) |
2305 (42) |
2197 (38) |
3063 (40) |
4110 (38) |
CL (mL/hour/kg) |
2.4 (42) |
2.7 (42) |
1.6 (39) |
1.2 (34) |
Vss (mL/kg) |
44.2 (25) |
47.3 (28) |
36.4 (12) |
37.3 (26) |
MRT (hours) |
18.1 (27) |
17.8 (35) |
23.4 (43) |
27.4 (28)b |
PK parameters are presented in geometric mean.
Abbreviations: IR = Incremental recovery; t1/2 = terminal half-life; AUC = area under the FVIII activity time profile; CL = clearance; Vss = volume of distribution at steady-state; MRT = mean residence time; CV% = coefficient of variation
a IR and FVIII recovery were assessed 30 minutes post-dosing 50 IU/kg for patients ≥12 years and 60 minutes post-dosing 50 IU/kg (first sample) for children <12 years.
b Calculation based on 64 profiles |
In the single-dose PK assessment in adult subjects, whose body mass index (BMI) ranged from 17-35 kg/m2, differences were noted for individuals who were overweight (BMI 25 - <30 kg/m2) and obese (BMI 30 - <35 kg/m2). Incremental recovery was increased by approximately 17% and 41%, AUC was increased by approximately 10% and 27%, and clearance was decreased by approximately 8% and 23% respectively, all in comparison to those subjects with BMI <25 kg/m2. There is insufficient data to recommend specific dose adjustments for overweight and obese patients. The dose may be adjusted as necessary per prescriber’s discretion.
Observed pre-dose (trough) and post-dose (peak) plasma Factor VIII activity levels at steady-state during prophylactic treatment with ESPEROCT are presented in Table 4 by dose regimen and age range.
Table 4: Steady-state trough and peak plasma FVIII activity by age and dose regimen, chromogenic assay (geometric mean [95% CI])
Dose Regimen |
60 IU/kg twice weekly**
(50-75 IU/kg) |
50 IU/kg Q4D* |
75 IU/kg Q7D* |
Age range
No. patients |
<6 years
N=31 |
6-<12 years
N=34 |
12-<18 years
N=23 |
≥18 years
N=143 |
12-<18 years
N=6 |
≥18 years
N=29 |
Trough, IU/dL |
1.2
(0.8; 1.6) |
2.0
(1.5; 2.7) |
2.7
(1.8; 4.0) |
3.0
(2.6; 3.5) |
0.6
(0.2; 1.6) |
1.3
(0.9; 2.0) |
Peak,
IU/dL |
125.0
(118.7; 131.6) |
143.3
(136.8; 150.2) |
125.1
(116.0; 135.0) |
137.9
(133.9; 142.2) |
198.0
(166.8; 235.2) |
197.9
(184.9; 212.7) |
*Data included in analysis: adolescents/adults Main Phase until Visit 8 (end of the Main Phase) 50 IU/kg Q4D, and extension 1 for 75 IU/kg Q7D. Only measurements collected at steady-state for the given prophylaxis treatment are included in the analyses.
**Data included in analysis: pediatric Main Phase 60 IU/kg (50-75 IU/kg) twice weekly. Only measurements collected at steady-state for the given prophylaxis treatment are included in the analyses. |
Time Of Factor VIII Activity Above 5%
Steady-state Factor VIII activity profiles were estimated using a one-compartment model with first-order elimination with PK parameters of clearance (CL) and volume of distribution (Table 5). Pharmacokinetic predictions showed that in all age groups, patients dosed twice weekly (dosing interval alternating between 3 and 4 days) or Q4D will be above 5% Factor VIII activity (i.e., in the range of mild hemophilia) for the majority of time (72-95% of time). Patients dosed with 50 IU/kg every 4 days will be above 1% Factor VIII activity 100% of the dosing interval. Patients dosed with 75 IU/kg every 7 days are predicted to be above 5% for 57% of time and above 1% for 83% of time.
Table 5:Estimation of steady-state peak and trough FVIII activity and time to 5% FVIII activity for ESPEROCT
Dose regimen
|
60 IU/kg
(50-75 IU/kg) twice weekly
|
50 IU/kg twice weekly |
50 IU/kg Q4D |
75 IU/kg Q7D |
Age range |
<12 years |
≥12 years |
≥12 years |
≥12 years |
Peak FVIII activity (%) |
110/112* |
133/138* |
132 |
194 |
Trough FVIII activity (%) |
2.8/0.8* |
8.6/3.6* |
3.5 |
0.3 |
Time to 5% FVIII activity (days) |
2.5/2.5* |
3.6/3.6* |
3.6 |
4.0 |
% of time in dosing interval above 5% FVIII activity |
72 |
95 |
90 |
57 |
*Twice weekly values are shown as 3 day/4 day. Only 50 IU/kg data are used for the analysis. |
Animal Toxicology And/Or Pharmacology
No adverse effects were observed in immune-deficient rats intravenously injected with ESPEROCT (50-1200 IU/kg/ injection), once every 4th day for 52 weeks. No evidence of polyethylene glycol accumulation was detected by immunohistochemical staining of brain tissue, including the choroid plexus.
Clinical Studies
The safety and efficacy of ESPEROCT have been evaluated in five multinational, open-label trials in male subjects with severe hemophilia A (<1% endogenous Factor VIII activity). One trial was subsequently partially randomized to evaluate two different prophylaxis regimens. All subjects were previously treated, which was defined as having received other Factor VIII products for ≥150 exposure days for adolescents and adults, and ≥50 exposure days for pediatric subjects. The key exclusion criteria across trials included known or suspected hypersensitivity to trial or related products and known history of Factor VIII inhibitors or current inhibitor ≥0.6 Bethesda units (BU).
The efficacy evaluation included 254 subjects, who received at least one dose of ESPEROCT, in the following trials:
- Adolescent/adult trial: This trial included 186 subjects, 161 adults (18 to 65 years old) and 25 adolescents (12 to <18 years old); it consisted of a Main Phase and optional Extension Phase. During the Main Phase, 175 subjects received the prophylaxis regimen which consisted of 50 IU/kg every 4 days (Q4D), while 12 adults chose to be treated on-demand. (One subject changed from on-demand to prophylaxis and is counted in both groups.) Thirteen (7%) of 175 adults in the prophylaxis arm modified their dosing regimen to Q3-4D dosing for ease of use. All subjects received at least one dose of ESPEROCT and are evaluable for safety and efficacy. A total of 165 subjects (91%) completed the Main Phase of this trial.
- Extension: This extension compared two dose regimens: 75 IU/kg every 7 days (Q7D) and 50 IU/kg Q4D. The randomization was open to subjects who experienced 2 or fewer bleeds during the last 6 months in the Main Phase.
- Pediatric trial: This trial included 68 subjects who were evenly divided with 34 in each age group, 0-<6 and 6-<12 years of age. All subjects received the same prophylaxis regimen of approximately 65 IU/kg (50-75 IU/kg) twice weekly. A total of 63 subjects (93%) completed the Main Phase.
- Surgery trial: In the surgery trial, 33 previously treated adolescents/adults underwent 45 major surgeries. The dose level of ESPEROCT was chosen so that FVIII activity at least as recommended by World Federation of Hemophilia (WFH) guidelines was targeted. All subjects returned to the adolescent/adult trial after the surgery trial assessments were completed.
On-Demand Treatment And Control Of Bleeding Episodes
There were 1506 bleeds reported in 171 of 254 subjects across the completed clinical trials, and the most common bleed types were joint (65.2%), muscle (14.5%), and subcutaneous (8.9%). Table 6 summarizes the efficacy in control of bleeding episodes by age.
Doses used for treatment of bleeding episodes depended on age, treatment regimen and the severity of the bleed.
Of the 1407 mild and moderate bleeding episodes in all subjects in the adolescent/adult study, the median dose used was 42 IU/kg. For subjects who were on the on-demand arm the median initial dose was 28 IU/kg and 88.4% of the bleeds were treated successfully with a single dose. In subjects receiving routine prophylaxis, the median initial dose was 52 IU/kg, and 76.4% of the bleeds were successfully treated with a single dose. Of the 15 severe bleeds, 12 (80%) required more than one dose with a total median dose of 111 IU/kg.
In the pediatric study, 70 mild/moderate bleeds in children < 12 years old receiving routine prophylaxis were treated with a median initial dose of 64 IU/kg per injection, with 63% treated with a single injection. When needed, additional median doses of 62 IU/kg were used at approximately 24 hour intervals. The median total dose was 70 IU/kg per bleed.
Table 6: Summary of efficacy in control of bleeding episodes by age
Age range
# of subjects |
|
<6 years
N=34 |
6 - <12 years
N=34 |
12 - <18years
N=25 |
≥ 18 years
N=161 |
Total
N= 254 |
# of bleeds |
|
30 |
40 |
112 |
1324 |
1506 |
# of injections |
1-2 |
76.7% |
82.5% |
88.4% |
95.5% |
94.3% |
> 2 |
23.3% |
17.5% |
11.6% |
4.5% |
5.7% |
Response to first treatment |
Excellent/ Good |
80.0% |
77.5% |
75.0% |
88.7% |
87.3% |
Moderate |
13.3% |
17.5% |
17.9% |
10.3% |
11.1 % |
Definition of Hemostatic Response:
Excellent: Abrupt pain relief and/or unequivocal improvement in objective signs of bleeding within approximately 8 hours after a single injection.
Good: Definite pain relief and/or improvement in signs of bleeding within approximately 8 hours after one injection, but possibly requiring more than one injection for complete resolution.
Moderate: Probable or slight beneficial effect within approximately 8 hours after the first injection; usually requiring more than one injection. |
Perioperative Management
The efficacy analysis of ESPEROCT in perioperative management included 45 major surgical procedures performed in 33 adolescent and adult subjects. The procedures included 15 joint replacements, 9 arthroscopic orthopedic interventions, 17 other orthopedic interventions, and 4 non-orthopedic surgeries.
The clinical evaluation of hemostatic response during major surgery was assessed using a 4-point scale of excellent, good, moderate, or none. The hemostatic effect of ESPEROCT was rated as “excellent” or “good” in 43 of 45 surgeries (95.6%), while the effect was rated as “moderate” in 2 surgeries (4.4%). No surgery had an outcome rated as “none” or “missing.”
The median pre-operative dose for adults and adolescents undergoing major surgeries was 52 IU/kg, and the median total dose was 702 IU/kg. During post-operative days 1-6, the median dose was 32 IU/kg at approximately 24 hour intervals. During post-operative days 7-14, the median dose was 36 IU/kg at approximately 28 hour intervals. The number of doses and duration of treatment varied by procedure.
Routine Prophylaxis In Adolescents/Adults
The efficacy of ESPEROCT in routine prophylaxis with Q4D dosing was demonstrated for the adult/adolescent population (see Table 7). In the extension part of the study, treatment success of the Q7D arm was not established. During the Main Phase of the adolescent/adult trial, 186 subjects had a total of 159 exposure years. The median annualized bleeding rate (ABR) for treated bleeds in adults and adolescents treated every 4 days was 1.2 (IQR: 0.0:4.3), and mean ABR was 3.0 (SD:
4.7). When including all bleeds (treated and non-treated), the median ABR was 1.2 (IQR: 0.0; 4.7) and the mean ABR was 3.3 (SD: 4.9).
Table 7: Efficacy in adolescent/adult prophylaxis, median and mean ABRs by age, treatment regimen, and bleed type
|
Prophylaxis |
On-demand |
Age Range |
12-17 years |
18-70 years |
12-70 years |
18-70 years |
# of subjects |
25 |
150 |
175 |
12 |
Mean treatment duration (years) |
0.85 |
0.81 |
0.82 |
1.33 |
Treated bleeds |
# of subjects with bleeds (%) |
19 (76) |
86 (57) |
105 (60) |
12 (100) |
# of subjects without bleeds (%) |
6 (24) |
64 (43) |
70 (40) |
0 |
# of bleeds |
67 |
369 |
436 |
532 |
Median ABR (IQR) |
2.2 (0.9;4.7) |
1.2 (0.0;3.7) |
1.2 (0.0;4.3) |
30.9 (18.6;38.5) |
Mean ABR (SD) |
3.5 (3.9) |
2.9 (4.8) |
3.0 (4.7) |
31.9 (19.1) |
All bleeds (treated and untreated) |
# of subjects with bleeds (%) |
19 (76) |
88 (59) |
107 (61) |
12 (100) |
# of subjects without bleeds (%) |
6 (24) |
62 (41) |
68 (39) |
0 |
# of bleeds* |
72 |
386 |
458 |
536 |
Median ABR (IQR) |
2.2 (0.9;6.0) |
1.2 (0.0;4.3) |
1.2 (0.0;4.7) |
31.3 (18.6;38.9) |
Mean ABR (SD) |
3.7 (4.1) |
3.2 (5.1) |
3.3 (4.9) |
32.2 (19.1) |
Treated spontaneous bleeds |
# of subjects with bleeds (%) |
11 (44) |
65 (43) |
76 (43) |
12 (100) |
# of subjects without bleeds (%) |
14 (56) |
85 (57) |
99 (57) |
0 |
# of bleeds |
30 |
221 |
251 |
415 |
Median AsBR (IQR) |
0.0 (0.0;1.5) |
0.0 (0.0;1.9) |
0.0 (0.0;1.8) |
19.4 (12.1;31.0) |
Mean AsBR (SD) |
1.4 (2.4) |
1.8 (3.7) |
1.7 (3.5) |
24.5 (17.3) |
Treated traumatic bleeds |
# of subjects with bleeds (%) |
16 (64) |
57 (38) |
73 (42) |
10 (83) |
# of subjects without bleeds (%) |
9 (36) |
93 (62) |
102 (58) |
2 (17) |
# of bleeds |
37 |
146 |
183 |
110 |
Median AtBR (IQR) |
1.3 (0.0;2.6) |
0.0 (0.0;1.4) |
0.0 (0.0;1.7) |
4.3 (0.8;9.9) |
Mean AtBR (SD) |
2.1 (2.9) |
1.1 (2.2) |
1.2 (2.3) |
6.1 (6.2) |
Treated joint bleeds |
# of subjects with bleeds (%) |
16 (64) |
74 (49) |
90 (51) |
12 (100) |
# of subjects without bleeds (%) |
9 (36) |
76 (51) |
85 (49) |
0 |
# of bleeds |
37 |
288 |
325 |
309 |
Median AjBR (IQR) |
1.2 (0.0;2.8) |
0.0(0.0;2.8) |
0.9 (0.0;2.8) |
19.4 (4.5;28.8) |
Mean AjBR (SD) |
1.8 (2.2) |
2.3 (4.3) |
2.2 (4.1) |
19.7 (15.1) |
ABR = annualized bleed rate; IQR = interquartile range, 25th percentile to 75th percentile; SD = standard deviation; AsBR = annualized spontaneous bleed rate; AtBR = annualized traumatic bleed rate; AjBR = annualized joint bleed rate.
*Reflects all bleeds reported by patients including those where no ESPEROCT was administered |
Routine Prophylaxis In Children <12 Years Of Age
Overall, 68 children below 12 years received prophylactic treatment with ESPEROCT at an average dose of approximately 65 IU/kg twice weekly. The prophylactic effect of ESPEROCT was demonstrated with a median ABR rate of 2.0 (IQR: 0.0; 2.8) and 2.0 (IQR: 0.0; 4.2) for treated bleeds and all bleeds respectively (see Table 8). The mean ABR (SD) for treated bleeds and all bleeds were 3.1 (7.1) and 4.4 (8.7), respectively. Of the 68 children, 22 (32%) did not experience any bleeding episodes and 29 (43%) did not experience any bleeding episodes that required treatment during the Main Phase of the trial. Of the 13 subjects with 17 documented target joints at baseline, 10 subjects (77%) and 14 target joints (82%) did not have any bleeds during the Main Phase of the trial.
Table 8: Efficacy in pediatric prophylaxis, medianand mean ABR by age and bleed type
|
Prophylaxis Regimen |
Age range |
< 6 years** |
6 to < 12 years |
0 to < 12 years |
# of subjects |
N=34 |
N=34 |
N=68 |
Mean treatment duration (years) |
0.46 |
0.51 |
0.48 |
Treated bleeds |
# of subjects with bleeds (%) |
19 (56) |
20 (59) |
39 (57) |
# of subjects without bleeds (%) |
15 (44) |
14 (41) |
29 (43) |
# of bleeds |
30 |
40 |
70 |
Median ABR (IQR) |
1.9 (0.0;2.1) |
2.0 (0.0;3.9) |
2.0 (0.0;2.8) |
Mean ABR (SD) |
3.9 (9.7) |
2.3 (2.9) |
3.1 (7.1) |
All Bleeds (treated and untreated) |
# of subjects with bleeds (%) |
20 (59) |
26 (77) |
46 (68) |
# of subjects without bleeds (%) |
14 (41) |
8 (24) |
22 (32) |
# of bleeds* |
41 |
65 |
106 |
Median ABR (IQR) |
2.0 (0.0;4.0) |
2.0 (1.9;6.0) |
2.0 (0.0;4.2) |
Mean ABR (SD) |
5.0 (11.9) |
3.8 (3.6) |
4.4 (8.7) |
Treated spontaneous bleeds |
# of subjects with bleeds (%) |
6 (18) |
7 (21) |
13 (19) |
# of subjects without bleeds (%) |
28 (82) |
27 (79) |
55 (81) |
# of bleeds |
9 |
10 |
19 |
Median AsBR (IQR) |
0.0 (0.0;0.0) |
0.0 (0.0; 0.0) |
0.0 (0.0; 0.0) |
Mean AsBR (SD) |
2.1 (7.3) |
0.6 (1.5) |
1.3 (5.3) |
Treated traumatic bleeds |
# of subjects with bleeds (%) |
15 (44) |
17 (50) |
32 (47) |
# of subjects without bleeds (%) |
19 (56) |
17 (50) |
36 (53) |
# of bleeds |
20 |
30 |
50 |
Median AtBR (IQR) |
0.0 (0.0; 2.0) |
0.9 (0.0;2.0) |
0.0 (0.0;2.0) |
Mean AtBR (SD) |
1.7 (4.0) |
1.7 (2.5) |
1.7 (3.3) |
Treated joint bleeds |
# of subjects with bleeds (%) |
7 (21) |
12 (35) |
19 (28) |
# of subjects without bleeds (%) |
27 (79) |
22 (65) |
49 (72) |
# of bleeds |
10 |
24 |
34 |
Median AjBR (IQR) |
0.0 (0.0;0.0) |
0.0 (0.0;2.0) |
0.0 (0.0;2.0) |
Mean AjBR (SD) |
1.5 (6.3) |
1.4 (2.4) |
1.5 (4.7) |
ABR = annualized bleed rate; IQR = interquartile range, 25th percentile to 75th percentile; SD = standard deviation; AsBR = annualized spontaneous bleed rate; AtBR = annualized traumatic bleed rate; AjBR = annualized joint bleed rate
*Reflects all bleeds reported by patients including those where no ESPEROCT was administered
**Elevated mean ABRs are due to subjects who withdrew from the study, whose bleeding rates were extrapolated to one year |