Pharmacotherapeutic group: antihemorrhagics, blood coagulation factor VIII, ATC code: B02BD02.
Mechanism of action
Turoctocog alfa pegol is a purified recombinant human factor VIII (rFVIII) product with a 40 kDa polyethylene-glycol (PEG) conjugated to the protein. The PEG is attached to the O-linked glycan in the truncated B-domain of rFVIII (turoctocog alfa). The mechanism of action of turoctocog alfa pegol is based on the replacement of the deficient or absent factor VIII in patients with haemophilia A.
When turoctocog alfa pegol is activated by thrombin at the site of injury, the B-domain containing the PEG moiety and the a3-region are cleaved off, thus generating activated recombinant factor VIII (rFVIIIa) which is similar in structure to native factor VIIIa.
The factor VIII/von Willebrand factor complex consists of two molecules (factor VIII and von Willebrand factor) with different physiological functions. When injected into a haemophiliac patient, factor VIII binds to von Willebrand factor in the patient's circulation. Activated factor VIII acts as a cofactor for activated factor IX, accelerating the conversion of factor X to activated factor X. Activated factor X converts prothrombin into thrombin. Thrombin then converts fibrinogen into fibrin and a clot can be formed. Haemophilia A is a X-linked hereditary disorder of blood coagulation due to decreased levels of factor VIII:C and results in profuse bleeding into joints, muscles or internal organs, either spontaneously or as results of accidental or surgical trauma. By factor VIII replacement therapy the plasma levels of factor VIII are increased, thereby enabling a temporary correction of the factor deficiency and correction of the bleeding tendencies.
Clinical efficacy during prophylaxis and treatment of bleeding episodes
The clinical efficacy of Esperoct for prophylaxis and treatment of bleeds was investigated in seven prospective, multi-centre clinical studies. All patients had severe haemophilia A.
Of note, annualised bleeding rate (ABR) is not comparable between different factor concentrates and between different clinical studies.
Prophylaxis in adults/adolescents
The efficacy of Esperoct for prophylaxis and treatment of bleeds was evaluated in an open-label, non-controlled study in adolescents and adult patients with severe haemophilia A ages 12 years and above. The prophylactic effect of Esperoct was demonstrated with a dosing at 50 IU per kg body weight every 4 days or every 3–4 days (twice weekly) in 175 patients. The median annualized bleeding rate (ABR) in adults and adolescents receiving Esperoct was 1.18 (Interquartile range IQR: 0.00;4.25), whereas the spontaneous ABR was 0.00 (IQR: 0.00;1.82), traumatic ABR was 0.00 (IQR: 0.00;1.74) and joint ABR was 0.85 (IQR: 0.00;2.84). When including imputations, (replacing missing data for withdrawn patients with a substituted value) the estimated mean ABR for all bleeds was 3.70 (95% CI: 2.94;4.66). Of the 175 adults/adolescents on prophylaxis, 70 (40%) did not have any bleeds. The mean annual consumption for prophylaxis was 4641 IU/kg.
Adults/adolescents who had a low bleeding rate of 0-2 bleeding episodes during the last 6 months and had obtained at least 50 doses of Esperoct had the option of being randomised to prophylaxis treatment every 7 days (75 IU/kg every 7 days) or every 4 days (50 IU/kg every 4 days). A total of 55 of the 120 eligible patients chose to be randomised (17 to the every 4 days dosing and 38 to the 75 IU every 7 days). The ABR for randomised patients was 1.77 (0.59; 5.32) for treatment every 4 days and 3.57 (2.13; 6.00) for once weekly prophylaxis. Nine of these patients reverted back to prophylaxis every 4 days during the randomised study phase. Overall, including all extensions parts, 31 of 61 patients on every 7 days prophylaxis switched back to every 4 days treatment.
Prophylaxis in previously treated patients (PTPs) (below 12 years)
The efficacy and safety of Esperoct for prophylaxis and on-demand treatment of bleeding episodes were evaluated in an open-label, single-arm, non-controlled study in 68 children below 12 years with severe haemophilia A. The prophylactic effect of Esperoct was demonstrated with a mean prophylactic dose of 64.7 IU per kg body weight twice weekly. The median and estimated mean annualized bleeding rate in children below 12 years receiving Esperoct twice weekly was 1.95 and 2.13 (95% CI: 1.48;3.06), whereas the spontaneous ABR was 0.00 and 0.58 (95% CI: 0.24;1.40), traumatic ABR was 0.00 and 1.52 (95% CI: 1.07;2.17) and joint ABR was 0.00 and 1.03 (95% CI: 0.59;1.81), respectively. Of the 68 children below 12 years on prophylaxis, 29 (42.6%) did not have any bleeds.
The mean annual consumption for prophylaxis was 6,475 IU/kg.
Due to the long duration of the study, several patients crossed the age-group to which they were initially enrolled: some < 6 years also contributed to the age category of 6-11 years and some 6-11 years age group had progressed to the adolescent age category. Main efficacy results in patients < 12 years separated by main and extension phase are summarised in table 4.
Table 4 Annualised Bleeding Rate (ABR) in the paediatric PTPs study by actual age-groups (main and extension phase) - full analysis set
| | Main Phase | Extension Phase |
| Age of patient* | 0-5 years (N=34) | 6-11 years (N=34) | 0-5 years (N=27) | 6-11 years (N=53) |
| Number of bleeds | 30 | 32 | 41 | 134 |
| Mean treatment period (years) | 0.46 | 0.51 | 4.79 | 4.86 |
| Total ABR |
| Poisson-estimated mean (95% CI) | 1.94 (1.12; 3.36) | 1.84 (1.08; 3.13) | 0.32 (0.15; 0.66) | 0.52 (0.35; 0.78) |
| Median (IQR) | 1.94 (0.00; 2.08) | 1.94 (0.00; 2.08) | 0.22 (0.00; 0.44) | 0.21 (0.00; 0.64) |
*some patients contributed to both age groups
Prophylaxis in previously untreated patients (PUPs) (below 6 years)
The efficacy and safety of Esperoct were evaluated in a multi-national, non-randomised, open label phase 3 study. Pre-prophylaxis (optional on-demand treatment for bleeding episodes and/or dosing of 60 IU/kg at intervals longer than a week until the subject reached 20 exposure days (EDs) or turned 24 months of age) and prophylaxis treatment of bleeds were evaluated in 81 PUPs below 6 years with severe haemophilia A. Of the total 81 patients, 55 patients started on pre-prophylaxis and 42 of those patients then switched to prophylaxis. In total 69 patients received prophylaxis with a mean prophylactic dose of 68.9 IU per kg body weight twice weekly.
The prophylactic effect of Esperoct in PUPs below 6 years with severe haemophilia A was demonstrated with a median and estimated mean annualized bleeding rate of 1.35 and 1.76 (95% CI: 1.26;2.46).
The mean annual consumption for the 69 PUPs on prophylaxis was 5,395 IU/kg.
Main efficacy results in PUPs on prophylaxis separated by main and extension phase are summarised in table 5.
Table 5 Annualised Bleeding Rate (ABR) in the paediatric PUPs study (main and extension phase) – full analysis set
| | Main Phase (N=69) | Extension Phase (N=55) |
| Number of bleeds | 124 | 223 |
| Mean treatment period (years) | 0.60 | 2.83 |
| Total ABR |
| Poisson-estimated mean (95% CI) | 2.98(2.16; 4.10) | 1.43 (0.98; 2.10) |
| Median (IQR) | 2.49(0.00; 5.22) | 0.73 (0.00; 2.57) |
In the study, a total of 56 adverse reactions in 43 of 81 patients and a total of 80 serious adverse events in 48 patients were reported after exposure to Esperoct.
In 31 out of 59 PUPs without inhibitors, temporary decreased factor VIII IR has been observed after exposure to Esperoct. There were 17 PUPs with consecutive measurements of decreased IR, all of these subjects had anti-PEG IgG antibodies. An association between anti-PEG antibodies and low IR cannot be excluded.
Clinical efficacy of Esperoct in treatment of bleeding episodes and during on-demand treatment
The efficacy of Esperoct in the treatment of bleeding episodes was demonstrated for all PTP age groups. The vast majority of bleeds treated with Esperoct were of mild/moderate severity.
The overall haemostatic success rate for the treatment of bleeds in PTPs was 84.4%.
The haemostatic success rates per age groups in PTPs were 89.4% (0−5 years), 82.6% (6−11 years), 78.9% (12−17 years) and 84.9% (≥ 18 years), respectively; and 94.2% of all bleeds were resolved with 1−2 injections.
The efficacy of Esperoct in the treatment of bleeding episodes was demonstrated in PUPs < 6 years of age. The overall haemostatic success rate was 91.9%; and 93.3% of the successfully treated bleeds were resolved with 1−2 injections.
In the pivotal study, 12 patients above 18 years of age, chose to stay on on-demand treatment. In these patients, 1 270 bleeds were treated with an average treatment dose of 37.5 IU/kg (20−75 IU/kg). 97% of the total bleeds were effectively treated with 1-2 injections of Esperoct.
Clinical efficacy of Esperoct during surgery
Haemostatic effect of Esperoct in surgical procedures was assessed in four studies, of which one was a dedicated surgery study.
In the dedicated surgery study, 49 major surgeries were performed in 35 previously treated adolescent and adult patients. On the day of surgery, patients received a pre-surgery mean dose of 55.7 IU/kg (range: 27.2−86.2 IU/kg) and post-surgery mean dose was 30.7 IU/kg (range: 10.1−58.8 IU/kg). The overall haemostatic success rate of Esperoct during major surgery was 95.9%, with the haemostatic efficacy rated as excellent or good in 47 of 49 major surgeries performed.
In two studies with previously treated children (aged < 12 years), 24 patients underwent 46 surgeries, of which only 1 surgery was categorized as major, with a successful haemostatic response. The minor surgeries in these patients were without any complications though haemostatic efficacy and FVIII levels were not monitored during these surgeries. In 26 previously untreated children (aged < 6 years) in the PUP study, a successful haemostatic effect was reported for all 4 major surgeries, and 25 of the 30 minor surgeries. Esperoct was administered at the investigators' discretion in accordance with the dosing recommendations.