Comprehensive Assessment of the Transition to Efanesoctocog Alfa Prophylaxis in a Paediatric Haemophilia A Cohort

ABSTRACT

Background

Efanesoctocog alfa is a novel recombinant factor VIII (FVIII) with an ultra‐extended half‐life and stable pharmacokinetics, approved for prophylaxis in children with haemophilia A (HA).

Objective

To describe the experience of transitioning paediatric patients with HA to efanesoctocog alfa using a comprehensive assessment.

Methods

Prospective observational study in a paediatric haemophilia unit. Patients <18 years without inhibitors were transitioned from prior prophylaxis to efanesoctocog alfa. Treatment regimen, adherence, annual bleeding rate (ABR), pharmacokinetics, joint health, sports, quality‐of‐life, treatment burden, treatment satisfaction/preference were compared at baseline and during follow‐up between efanesoctocog alfa and previous treatment.

Results

Eighteen patients (mean age 9.42 years) were included. After 365 ± 84.08 days, adherence improved and no inhibitors were detected. A significant increase in half‐life was observed (from 13.57 ± 3.6 to 57.13 ± 6.1 h) which led to a lower ABR score in the series (0.39–0.05) and an improvement of joint health after 6 months (n = 15 patients), due to a relevant synovitis reduction (20% reduction in elbows; 13.3% in ankles) despite patients were moderately‐highly physically active. Quality‐of‐life perception improved after 3 months (EQ‐VAS increased: 90.72 ± 10.31 to 95.25 ± 5.3; p = 0.03) as well as treatment burden (HEMO‐TEM global score in 12–18 year‐old patients: 16.08 ± 11.43 to 11.72 ± 14.8). Patients/caregivers expressed a strong preference for efanesoctocog alfa.

Conclusion

Transitioning to efanesoctocog alfa was safe and effective in this paediatric cohort. Despite limited follow‐up, data suggest this therapy offers meaningful clinical and psychosocial benefits.

1. Introduction

Patients with haemophilia are characterized by a bleeding tendency that usually correlates with the residual factor VIII (FVIII) plasma activity levels [1]. To avoid spontaneous and/or traumatic haemorrhages and long‐term sequelae, regular prophylaxis is recommended as the standard of care in people with haemophilia and a severe bleeding phenotype [2]. Early prophylaxis has demonstrated its utility in avoiding bleeds and preserving joint health [3]. However, regular intravenous administration two or three times per week is burdensome, especially during infancy, when venous access is usually the main challenge [4]. New therapeutic strategies for haemophilia A (HA) aimed at reducing patient burden such as extended half‐life FVIII products and emicizumab, a non‐substitutive subcutaneous drug that mimics FVIII, have changed this landscape [5, 6, 7, 8].

Efanesoctocog alfa (Altuvoct) is a novel recombinant modified FVIII with an ‘ultra‐extended half‐life’ and stable pharmacokinetics (PK), approved for weekly dosing in paediatric patients [9, 10, 11]. XTEND‐Kids was a phase 3 study evaluating the use of a weekly dose of efanesoctocog alfa (50 IU/kg) over one year in 74 previously treated paediatric patients younger than 12 years of age with severe HA and no personal history of inhibitors. Treatment was safe and no inhibitors were detected. PK showed a sustained FVIII level above 40% for three days after first treatment infusion, and above 10 IU per deciliter for 6.7 days. Prophylaxis provided highly effective bleed protection. More than 80% of the patients had no joint bleeds, total mean annual bleeding rate (ABR) was 0.89 and those who experienced a bleed had an excellent response to treatment with a single dose in 95% of the episodes. Real‐world data are still scarce [9]. A recent publication included a large cohort of 28 paediatric patients, but children younger than 6 years were not represented. They reported PK data, excellent bleeding outcomes, some information about the reasons for switching to efanesoctocog alfa, and patients and caregivers impressions after 6 months of starting treatment [12].

In general, response to prophylaxis in real life has been historically evaluated using mainly objective data that are able to measure treatment effectiveness such as ABR or joint health [13]. Although there is no standard for performing a global assessment, different expert consensus agrees on the need of using different available tools to better evaluate the patient status, especially when offering a new prophylactic treatment option [14].

The aim of this study is to present a prospective comprehensive assessment of paediatric patients, including adolescents, infants and very young children, switching from a previous prophylactic treatment to efanesoctocog alfa. The comparison between efanesoctoocg alfa and the previous regimen included several domains: clinical data, treatment adherence, FVIII measurements, PK parameters, joint health evaluation, sport participation, and patient‐reported outcomes and experience measures, assessed at different time points after switching.

2. Material and Methods

2.1. Study Description

Prospective observational study in a single paediatric Haemophilia Reference Unit. All patients with HA under 18 years of age who switched from a previous prophylactic treatment to efanesoctocog alfa were eligible for the study from October 2024 to March 2026. Exclusion criteria included previous on‐demand treatment, participation in a clinical trial with efanesoctocog alfa, or caregiver refusal to participate. Pharmacokinetic data from patients excluded from the comprehensive assessment were evaluated when possible (Figure 1).

FIGURE 1.

Flow chart of the patients included in the comprehensive evaluation, reason for excluding the rest of the patients receiving efanesoctocog alfa in the center and those who were included some part of the pharmacokinetic evaluation. ABR: annual bleeding rate. PK: pharmacokinetic evaluation. † FVIII level 7 days post‐infusion and two hours after administration; ‡ FVIII activity level measured at days 3–7 between months 6 and 12 was performed. § HEMO‐TEM was only performed in children older than 12 years of age.

2.2. Patients and Data Obtained

Main clinical characteristics regarding the patient, the disease and the prophylactic regimen, including dose (IU/kg) and treatment adherence, were collected. A prospective global assessment in those patients who switched to efanesoctocog alfa was performed. Data obtained during prophylaxis with efanesoctocog alfa were compared to evaluations. Figure 1 summarizes the comprehensive assessment that consisted of:

• ‐ Bleed assessment: bleeds were reported by patients/caregivers. ABR was calculated based on the documented events treated with factor concentrate. Bleed location, severity and response to treatment were evaluated according to published criteria [1].
• ‐ Adherence to treatment: evaluated by medication possession ratio, expressed as the percentage of time for which medication was available, based on indirect pharmacy measures (dispensing records).
• ‐ Pharmacokinetics (PK): FVIII maximum activity level measured two hours after administration ('peak') and minimum concentrations (Cmin) of efanesoctocog alfa ('trough') measured seven days post‐infusion were assessed at months 1, 3 and 6. An additional FVIII activity level measured between days 3–7 post‐infusion was obtained between months 6 and 12. FVIII activity levels were measured by one‐stage assay (Werfen; SynthaFAX). PK curves were estimated individually using a Web‐Accessible Population Pharmacokinetic Service‐Haemophilia for Europe [15]. PK data from patients excluded from the comprehensive assessment for any reason were analyzed separately (Figure 1).
• ‐ Joint Health: evaluated every six months in patients older than 5 years using the Haemophilia Joint Health Score 2.1 (HJHS; range,0–124, with lower scores indicating better joint health) [16] and the Haemophilia Early Arthropathy Detection with Ultrasound (HEAD‐US) [17]. A target joint was defined as a joint with ≥ 3 spontaneous bleeds within a six‐month period [1].
• ‐ Assessment Physical Activity Levels Questionnaire (APALQ): [18] in children older than 8 years (baseline and after 6 months).
• ‐ Patient reported outcomes and patient reported experience measures were evaluated at baseline, months 3, and 6. Questionnaires were administered face‐to‐face during on‐site visits. EQ‐5D‐Y‐3L and EQ‐VAS were used for quality‐of‐life perception evaluation (also evaluated at month 1). EQ‐5D‐Y‐3L is a generic child friendly health‐related quality‐of‐life instrument that measures five dimensions (mobility, self‐care, usual activities, pain/discomfort, and anxiety/depression) with three possible answers (no problems = 1; some problems = 2; many problems = 3). EQ‐VAS is a quantitative measure of a patient's perceived health status, expressed as a score from 0 to 100 (higher score relates to better health status) [13, 19]. Treatment burden was evaluated by HEMO‐TEM in older than 12 years of age, a haemophilia‑specific tool designed to assess treatment burden by evaluating injection difficulties, physical impact, emotional burden, and interference with daily life. Score range between 0–100; higher score relates to higher burden [20]. Finally, an ad‐hoc questionnaire was used to assess treatment and regimen satisfaction (scale 1–5) at baseline, month 3 and month 6; and preference to treatment (three possible responses: strong, intermediate, mild or not preference) after switching. EQ‐5D‐3L‐Y, EQ‐VAS and the ad‐hoc questionnaire were given to children older than 8 years or to caregivers in younger than 8 years‐old patients.

2.3. Statistical Analysis

Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS Statistics, version 27.0). Descriptive statistics included frequencies and percentages for categorical variables and means, standard deviations, confidence intervals, medians, and interquartile ranges for continuous variables. Categorical variables were assessed by Chi²‐test and continuous variables by t‐test or Mann‐Whitney test. p values were considered statistically significant when <0.05.

2.4. Ethics

The study was approved by the Ethics Committee of our institution (Hospital Sant Joan de Déu) and it was performed according to the declaration of Helsinki ethical principles, Fortaleza version, Brazil October 2013 (PIC‐205‐25). An information sheet was given before informed consent was obtained from patient's legal guardians. Patients older than 12 years provided written assent.

3. Results

A total of 18 paediatric patients were included in the comprehensive evaluation (Figure 1). All of them were phenotypically severe HA patients (FVIII activity levels <1%: 16 patients; 1%–5%: two teenagers); mean age was 9.42 years (standard deviation (SD) ±3.57); median age was 9.74 years (range 1.1–13.8 years). Patients were grouped into <6 years (n = 4), 6–12 years (n = 8) and >12 years (n = 6). There were 17 boys and a 12‐year‐old girl with a severe HA secondary to a skewed X‐chromosome inactivation. Four patients had a personal history of inhibitor, but they had successfully responded to a previous immune tolerance induction. They continued FVIII prophylaxis thereafter and showed a half‐life comparable to other patients.

3.1. Treatment Regimen and Bleeds

Patients in the comprehensive assessment switched from a previous individualized FVIII regimen to efanesoctocog alfa (Table 1). After 356.11 days ± 84.08 under prophylaxis with efanesoctocog alfa, no inhibitors were diagnosed. Mean ABR decreased from 0.39 ± 0.59 bleeds during the immediate previous year to 0.05 ± 0.22: only one patient presented a traumatic nose bleed on day 6 after prophylaxis administration that required an efanesoctocog alfa dose based on caregiver decision. The same patient underwent a minor procedure (deciduous tooth extraction) performed the same day of prophylaxis administration with no relevant bleeding problems. Adherence to treatment at baseline was good, but improved with the new treatment.

TABLE 1.

Comparison between previous treatment regimen and efanesoctocog alfa administration in the series.

	Previous substitutive treatment	Efanesoctocog alfa
Previous administered FVIII	Standard half‐life FVIII: 5 patients Extended half‐life FVIII: 13 patients	18 patients
FVIII Dose (UI/kg ± SD)	31.64 ± 9.47	46.99 ± 7.1
Weekly dose (UI/kg ± SD)	89.56 ± 32.1	46.99 ± 7.1
Weight (mean ± SD) Weight (median; range)	33.6 ± 12.9 33.5 (range 9.0–60.8)
Injections per week	3 times per week (n = 16) 2 times per week (n = 2) a	1 per week (n = 18)
Adherence	99.5% [87%–100%]	100% [95.6%–100%]
Annual bleeding rate	0.39 ± 0.59	0.05 ± 0.22

^a One was a moderate HA patient, the other a severe HA patient whose FVIII half‐life was around 22 h.

3.2. Pharmacokinetic Evaluation

FVIII activity peak and trough levels were measured in all patients at 1, 3 and 6 months after efanesoctocog alfa initiation. Trough FVIII activity levels slightly increased over time, from 11.31 ± 3.4 IU/dL at month 1 to 13.89 ± 7.05 IU/dL at month 6. Estimated half‐life improved from 13.57 ± 3.6 h with previous prophylactic treatment to 53.11 ± 5.4 h at month 1 and to 57.13 ± 6.1 h at month 6, despite a decrease in the mean efanesoctocog alfa dose from 46.99 ± 7.1 IU/kg at baseline to 44.62 ± 5.39 IU/kg at month 6. Differences in trough levels and estimated half‐life according to the age group are shown in Figure 2. Patients with a personal history of inhibitors did not show any relevant differences in half‐life.

FIGURE 2.

Global result of pharmacokinetics studies (peak, trough FVIII activity levels, generated half‐life) and dose after 1, 3 and 6 months of starting prophylaxis with efanesoctocog alfa, and according to age group.

FVIII activity levels measured between days 3 and 7 post‐infusion were available in 12 patients. These values were comparable to the FVIII activity previously estimated by a population pharmacokinetic‐based dosing tool in all but two patients, whose FVIII activity were 8 to 13 IU/dL higher than expected.

PK data from eight patients excluded from the comprehensive evaluation were also analyzed (Figure 1). Mean estimated half‐life was 50.40 ± 3.25 h (mean trough levels 10.76 ± 2.28 IU/dL) at a mean dose of 46.47 ± 3.95 IU/kg. Notably, in the youngest patient, a previously untreated patient aged 13 months when efanesoctocog alfa was initiatied, the estimated half‐life was 41.4 h after 25 efanesoctocog alfa administrations.

Estimated half‐life was also used to calculate the time required to reach FVIII activity bellow 40, 30 and 20 IU/dL in a total of 27 patients. No statistically significant differences between age groups were observed (Table 2).

TABLE 2.

Mean time to reach 40, 30 and 20 IU/dL since treatment administration according to generated PK data for each age group.

	Time to 40 IU/dL (hours)	Time to 30 IU/dL (hours)	Time to 20 IU/dL (hours)
1‐6 years (n = 5)	59.75 ± 12.79	82.75 ± 13.6	115.0 ± 15.71
6‐12 years (n = 9)	69.33 ± 13.27	94.89 ± 15.58	129.89 ± 17.65
Comparison between 1–6 years and 6–12 years	p = 0.25	p = 0.207	p = 0.176
12–18 years (n = 12)	72.91 ± 13.52	94.91 ± 14.36	126.0 ± 16.26
Comparison between 1–6 years and >12 years	p = 0.105	p = 0.157	p = 0.264

3.3. Joint Health

HJHS and HEAD‐US were available for 15 patients. No target joints were identified at baseline. Both scores improved after receiving efanesoctocog alfa for 6 months. Mean HJHS 1.13 ± 0.44 at baseline decreased to 0.50 ± 0.2, and HEAD‐US decreased from 1.0 ± 0.31 to 0.56 ± 0.24 due to a reduction of synovitis (Figure 3). HEAD‐US detected grade 1 synovitis, but no grade 2 synovitis or relevant cartilage/bone abnormalities. Ten patients were assessed after 12 months of efanesoctocog alfa initiation, showing synovitis improvements in two patients.

FIGURE 3.

Change in HJHS domain scores and synovitis improvement according to each evaluated joint from baseline to month.

3.4. Physical Activity

APALQ showed that almost all evaluated patients (n = 14) were moderately to highly physically active (8–17 points). All patients remained stable on this scale but one who shifted from moderate to highly active.

3.5. Quality‐of‐Life

It was evaluated at baseline and at different points during the follow‐up. EQ‐VAS showed a prompt tendency for improving through time, achieving a statistically significant difference after 3 months that persisted later on time (Table 3).

TABLE 3.

EQ‐5D‐3L and EQ‐VAS results through time.

	Baseline n = 18	Month 1 n = 18	Month 3 n = 18	Month 6 n = 18
EQ‐5D‐3L
Mobility (walking); n (%) • No problems • Some problems • Many problems	17 (94.4) 1 (5.6) 0	18 (100) 0 0	18 (100) 0 0	18 (100) 0 0
Self‐care; n (%) • No problems • Some problems† • Many problems	17 (94.4) 1 (5.6) 0	17 (94.4) 1 (5.6) 0	17 (94.4) 1 (5.6) 0	17 (94.4) 1 (5.6) 0
Usual activities; n (%) • No problems • Some problems a • Many problems	17 (94.4) 1 (5.6) 0	17 (94.4) 1 (5.6) 0	17 (94.4) 1 (5.6) 0	17 (94.4) 1 (5.6) 0
Pain/discomfort; n (%) • No pain • Some pain • Much pain	15 (83.3) 2 (11.1) 1 (5.6)	17 (94.4) 1 (5.6) 0	18 (100) 0 0	17 (94.4) 1 (5.6) 0
Worried/sad; n (%) • No worried • A little bit worried • Very worried	16 (88.8) 1 (5.6) 1 (5.6)	17 (94.4) 1 (5.6) 0	18 (100) 0 0	18 (100) 0 0
EQ‐VAS
Score	90.72 ± 10.31	93.75 ± 6.7 p = 0.172	95.25 ± 5.3 p = 0.03	95.11 ± 6.8 p = 0.015

Note: Bold values indicate statistically significant differences (p < 0.05).

^a The patient who had some problems for self‐care and doing usual activities is a 4 year‐old boy with history of a cerebral hemorrhage at diagnosis.

3.6. Treatment Burden

Global score in HEMO‐TEM improved over time, although statistically significant difference was not seen after 6 months. Treatment bother domain showed a significant difference after 6 months (Table 4).

TABLE 4.

Results of Hemo‐TEM questionnaire at baseline, month 3 and 6 comparing the results by each domain and total score. Total score is calculated by summing the number of items and converting onto a 0–100 scale using: Injection difficulties: (Sum/12) × 100; Physical impact: (Sum/24) × 100; Treatment bother: (Sum/28) × 100; interference: (Sum/16) × 100; emotional impact: (Sum/24) × 100.

	Baseline	Month 3	Baseline to month 3	Month 6	Baseline to month 6
Injection difficulties	2.12 ± 2.59	1.71 ± 2.06	0.671	1.63 ± 1.92	0.206
Physical impact	1.62 ± 1.30	1.14 ± 0.69	0.336	2.75 ± 3.92	0.863
Treatment bother	3.62 ± 5.26	1.43 ± 1.62	0.450	0.88 ± 1.46	0.042
Interference	2.88 ± 4.55	3.14 ± 2.79	0.292	2.38 ± 2.13	0.686
Emotional impact	6.00 ± 11.06	1.29 ± 1.38	0.461	3.75 ± 7.05	0.126
Total score	16.08 ± 22.43	9.83 ± 4.70	0.938	11.72 ± 14.8	0.195

Note: Bold values indicate statistically significant differences (p < 0.05).

3.7. Treatment Satisfaction and Treatment Preference

An ad‐hoc questionnaire showed that 15 patients/caregivers reported highly satisfaction with the previous treatment at baseline. Two teenagers were moderately satisfied and the caregiver of the youngest patient reported being neither satisfied/nor dissatisfied with the treatment regimen. After switching, all patients/caregivers were highly satisfied with the new regimen and expressed a strong preference for the new treatment.

4. Discussion

A comprehensive assessment (including clinical, analytical, patient reported outcomes and patient‐reported experience measures) evaluating the switch from a previous FVIII treatment regimen to efanesoctocog alfa in a real‐life paediatric HA cohort showed that treatment was safe, effective and comparable to previously published data [9, 12]. This series included four children <6 years of age. As expected, trough FVIII activity levels were lower in younger patients. However, not relevant clinical differences were observed, and trough levels increased over time. Sustained FVIII levels across all age groups resulted in a rapid improvement of joint health, quality‐of‐life perception and treatment burden. All patients and their caregivers reported a strong preference for the new treatment.

Contemporary definition of prophylaxis in haemophilia consists of the regular, long‐term administration of haemostatic agents to prevent bleeding episodes, especially hemarthrosis, with the aim of achieving a QoL comparable to that of individuals without haemophilia [21]. Keeping this in mind, we prospectively compared efanesoctocog alfa prophylaxis with the previous FVIII regimen by evaluating relevant outcomes trough a global assessment that included patient and caregiver's perspectives regarding quality‐of‐life and treatment burden based on the recommendations of a Spanish consensus [14].

The high adherence rate at baseline was likely related to the low ABR and the good overall health status described before switching. Nevertheless, although follow‐up is still short, efanesoctocog alfa demonstrated a favorable prophylactic profile in our series, including the management of minor surgery. To date, only one patient experienced a mild traumatic nosebleed, despite most participants reported moderate to high levels of physical activity, which could have been related to a higher bleeding risk. As bleeds were reported by patients and their caregivers, it could be possible that mild bleeding symptoms could have been underestimated. However, joint health improvement makes us think that the possibility of non‐reported or non‐recognized bleed is quite unlikely.

During the XTEND‐Kids study, joint health was evaluated using HJHS, which improved from baseline to week 52 [9]. We observed similar results in our series. Global HJHS was good at baseline, but decreased ‐0.53 points as a result of swelling, muscle atrophy and crepitus on motion improvements. Moreover, we documented a relevant reduction in synovitis in ankles and elbows only 6 months after starting efanesoctocog alfa. This trend persisted among those patients who were evaluated after receiving efanesoctocog alfa for 12 months. It is well known that, despite prophylaxis, long‐term joint damage may still occur due to symptomatic or asymptomatic minimal joint bleeds. Therefore, periodic monitorization and early synovitis detection are crucial, as joint damage is potentially reversible at this point, before cartilage and bone damage development [22, 23, 24]. Overall, these findings support the idea that sustained FVIII levels achieved with efanesoctocog alfa prophylaxis may potentially improve short and long‐term articular damage even in highly sporty children and teenagers.

Efanesoctocog alfa activity levels assessment has some peculiarities. Only Actin‐FSL seems to target FVIII levels at all concentrations, but we evaluated efanesoctocog alfa using both SynthaFAX as they have been described to be suitable for evaluating efanesoctocog alfa concentrations [25]. Based on our own experience, we rely on SynthaFAX measurements.

We performed a PK study after 4 weeks receiving treatment as data from the XTEND‐Kids study indicated that trough levels after the first injection may be lower than those observed at steady state. In fact, we did additional PK evaluations (3 and 6 months) to assess the increment of trough FVIII activity levels over time. Notably, none of our patients with personal history of inhibitor and previous successful immune tolerant induction treatment had a shorten half‐life.

Our data suggest that multiple routine monitoring may be unnecessary. Estimated PK parameters remained consistent over time, despite slightly dosage variations caused by changes in body weight. However, monitoring is still warranted at least once in order to obtain PK data that allow for Bayesian estimations and FVIII activity predictions such as time to reach FVIII activity less than 40, 30 or 20 IU/dL, a useful information for daily life. These data can be shared with the patient helping them to understand PK and anticipated activity levels over time. It will be also helpful for guiding surgery or for self‐monitoring and self‐management of treatment in some scenarios such as breakthrough bleeds or severe trauma [26, 27]. Given the PK differences between age groups, particularly in children younger than 6 years of age, it would be advisable to compare real‐life and expected FVIII activity levels to decide if a new complete PK study is needed.

Different questionnaires were required to assess patient reported outcomes and patient reported experience as none of the current available measures is able to globally evaluate clinical, psychological and social aspects [14]. This is a limitation itself, as in order to prevent overburdening patients and caregivers, we avoid using large generic quality‐of‐life questionnaires such as PedsQL that could have been more informative than EQ‐5D‐3L. However, items included in this short questionnaire together with EQ‐VAS scale have been able to previously demonstrate sensitivity to clinical changes in haemophilia management [13, 19]. We think that the statistically significant improvement in the quality‐of‐life perception of our patients after three months of starting efanesoctocog alfa highlights the quick benefits of this new treatment.

Regarding treatment burden, it is reasonable that, comparing to previous twice or trice per week intravenous administration regimen, a weekly dose will be related to less burden. Most of the patients previously received treatment three times per week. These schedules were stablished according to PK data and patient needs, targeting high though FVIII plasmatic levels over 4–5 IU/dL. Efanesoctocog alfa decrease treatment burden achieving higher though FVIII levels with less injections. Trying to demonstrate this, we used a specific tool for evaluate different aspects related to treatment. We could not use the Child version for younger than 12 years, which is a major limitation, but we found a global improvement of the score after 6 months of treatment when compare to baseline results in older children [20]. We found statistically significant differences in treatment bother domains, results that could be related to the 100% adherence seen in our patients to date. Physical and emotional impact apparently worsens at month 6. This finding is driven by an outlier whose responses were influenced by personal stressors and a negative experience during two unsuccessful intravenous injection attempts.

Most of the patients and their caregivers expressed they were satisfied with the previous regimen. A qualitative assessment of the reasons underlying treatment satisfaction was not performed but, importantly, all of them expressed a strong preference for the new regimen. PK profile of efanesoctocog alfa using a weekly dose and the low ABR described in this series despite the high sport participation rate could help patients and their caregivers to achieve a free mind haemophilia, escaping from the uncertainties related to the disease and its treatment [28, 29]. Surprisingly, caregivers in this series did not express to feel disconcerting for the sudden transition to weekly infusions as previously described [12]. We speculate that previous discussions about the different treatment options, and results from XTEND‐Kids could have helped to this fact.

Apart from the small sample size, some of the limitations have been included through the discussion. However, despite the short follow‐up, this prospective study has been able to described improvements in ABR, PK profile as well as in quality‐of‐life perception, patient experience and adherence.

In conclusion, we report one of the first real‐life series of paediatric patients transitioning to efanesoctocog alfa. Prophylaxis was safe and effective, and relevant improvements were observed in PK, adherence, ABR and joint health (despite of sports participation), patient‐reported outcomes and patient‐reported experience. Despite limited follow‐up, our data suggest that this therapy offers meaningful clinical and psychosocial benefits in the comprehensive management of paediatric HA.

Funding

The authors have nothing to report.

Ethics Statement

The study was approved by the Ethical Committee from our institution (Hospital Sant Joan de Déu) and it was performed according to the declaration of Helsinki ethical principles, Fortaleza version, Brazil October 2013 (PIC‐205‐25).

Consent

An informed consent was obtained from patient's legal guardians. Those patients older than 12 years old signed an informed assent.

Conflicts of Interest

Rubén Berrueco has received reimbursement for attending symposia/congresses and/or honoraria for speaking and/or honoraria for consulting, and/or funds for research from Takeda, Roche, Bayer, CSL‐Behring, Novo Nordisk, Sobi, Octapharma, Amgen, Werfen, Stago, Boehringer Ingelheim and Pfizer. Nuria Caballero and Cristina Benedicto have received reimbursement for attending symposia/congresses honoraria for speaking and/or counselling from Sobi, Roche, Bayer, CSL‐Behring, Novo Nordisk and Pfizzer. CGA has received reimbursement for speaking from Sobi. Pablo Estival has received reimbursement for attending symposia/congresses and honoraria for speaking from Sobi an Pfizzer. NRN has received reimbursement for attending symposia/congresses and honoraria for speaking, consulting and funds from Sobi.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author upon reasonable request. The data are not publicly available due to privacy or ethical restrictions.