Growth in achondroplasia, from birth to adulthood, analysed by the JPA-2 model

Physical Activity and Psychosocial Outcomes in Adults with Achondroplasia: An Exploratory Study

BACKGROUND

Adults with achondroplasia face physical and psychosocial challenges that may impact their health-related quality of life and mental health. This exploratory cross-sectional study aimed to investigate relationships between health-related quality of life, mental health, and physical activity levels in adults with achondroplasia, focusing on potential gender differences.

METHODS

Sixteen adults with achondroplasia (10 women, 6 men; age 37.2 ± 13.5 years) completed the Short Form Health survey, the Brief Symptom Inventory, and the International Physical Activity questionnaire. Descriptive statistics, non-parametric group comparisons, correlational analyses, and linear regressions were conducted.

RESULTS

Moderate physical activity showed strong positive correlations with general health (rs = 0.79, 95% CI [0.50, 0.92]), vitality (rs = 0.60, 95% CI [0.15, 0.85]), and physical functioning (rs = 0.62, 95% CI [0.18, 0.86]), on SF-36. Women reported lower quality of life scores than men across most SF-36 dimensions. Significant gender difference was observed in vitality (r = 0.61) and pain (r = 0.55). Physically active participants presented better outcomes in general health (r = 0.63) and vitality (r = 0.55) compared to inactive participants.

CONCLUSIONS

This study provides preliminary evidence suggesting potential benefits of moderate-intensity physical activity on health-related quality of life and mental health among adults with achondroplasia, with notable gender differences. While limited by sample size and study design, the findings highlight the need for larger, longitudinal studies to further explore the role of physical activity in enhancing well-being in this population.

Exploring the family experience of children aged 2-4 years receiving daily vosoritide injections: A qualitative study

PURPOSE

Vosoritide is administered as a daily subcutaneous injection in children with achondroplasia. In clinical trials, families of children aged 2-4 years reported difficulty with drug administration due to child fear, pain, and distress. Study aims were to gain a better understanding of the current vosoritide administration experience in this cohort and to investigate whether topical anaesthesia and ice application prior to injections improved the child and family experience.

DESIGN AND METHODS

A qualitative descriptive study design ensured in-depth understanding of family experience. Parents were interviewed to explore experience of vosoritide administration for their child at two time points, before (Phase 1) and after (Phase 2) the introduction of topical anaesthesia and ice application prior to injections. Interviews were analysed using thematic analysis.

RESULTS

Seven families participated. Children's ages ranged from 2 years 2 months to 3 years 11 months. Five themes emerged from data analysis: (1) The reality of the burden of care; (2) Child experience as the greatest obstacle; (3) Parents juggle multiple emotional considerations; (4) Many factors may impact experience; and (5) Short-term and long-term impacts.

CONCLUSIONS

Administration of vosoritide in this cohort presents multiple challenges for families. Factors which influenced experience differed between families. Responses to topical anaesthesia and ice application also varied between children, improving administration experience for some children and worsening experience for others.

PRACTICE IMPLICATIONS

This study highlights the need for individualised care for young children receiving daily injections. Support should be provided to families to identify factors that improve experience.

Once-weekly TransCon CNP (navepegritide) in children with achondroplasia (ACcomplisH): a phase 2, multicentre, randomised, double-blind, placebo-controlled, dose-escalation trial

Background

TransCon CNP (navepegritide) is an investigational prodrug of C-type natriuretic peptide (CNP) designed to allow for continuous CNP exposure with once-weekly dosing. This 52-week phase 2 (ACcomplisH) trial assessed the safety and efficacy of TransCon CNP in children with achondroplasia.

Methods

ACcomplisH is a global, randomised, double-blind, placebo-controlled, dose-escalation trial. Study participants were recruited between June 10, 2020, and September 24, 2021. Eligible participants were prepubertal, aged 2-10 years, with genetically confirmed achondroplasia, and randomised 3:1 to once-weekly subcutaneous injections of TransCon CNP (6, 20, 50, or 100 μg CNP/kg/week) or placebo for 52 weeks. Primary objectives were safety and annualised growth velocity (AGV). ACcomplisH is registered with ClinicalTrials.gov (NCT04085523) and Eudra (CT 2019-002754-22).

Findings

Forty-two participants received TransCon CNP at doses of 6 μg (n = 10; 7 female), 20 μg (n = 11; 3 female), 50 μg (n = 10; 3 female), or 100 μg (n = 11; 6 female) CNP/kg/week, with 15 receiving placebo (5 female). Treatment-emergent adverse events (TEAEs) were mild or moderate with no grade 3/4 events reported. There were 2 serious TEAEs that were assessed as not related to TransCon CNP. Eleven injection site reactions occurred in 8 participants receiving TransCon CNP and no symptomatic hypotension occurred. TransCon CNP demonstrated a dose-dependent improvement in AGV. At 52 weeks, TransCon CNP 100 μg CNP/kg/week significantly improved AGV vs placebo (least squares mean [95% CI] 5.42 [4.74-6.11] vs 4.35 [3.75-4.94] cm/year; p = 0.0218), and improved achondroplasia-specific height SDS from baseline (least squares mean [95% CI] 0.22 [0.02-0·41] vs -0·08 [-0.25 to 0.10]; p = 0.0283). All participants completed the randomised period and continued in the ongoing open-label extension period receiving TransCon CNP 100 μg CNP/kg/week.

Interpretation

This phase 2 trial suggests that TransCon CNP is effective, safe, with low injection site reaction frequency, and may provide a novel, once-weekly treatment option for children with achondroplasia. These results support TransCon CNP at 100 μg CNP/kg/week in the ongoing pivotal trial.

Funding

Ascendis Pharma, A/S.

Growth patterns of young achondroplasia patients in Korea and predictability of neurosurgical procedures

BACKGROUND

Achondroplasia is an autosomal dominant disorder mainly affecting bony growth, typically resulting in markedly short stature. From a neurosurgical viewpoint, patients sometimes develop spinal cord compression at the narrowed foramen magnum and hydrocephalus. This study aims to construct growth references for height, weight, and head circumference (HC) of young achondroplasia patients in Korea and to evaluate the predictability of the necessity and timing of neurosurgical procedures through growth patterns.

METHODS

Growth data were collected from achondroplasia patients who visited our institution between January 2002 and August 2022. First, we constructed percentile growth curves of height, weight, and HC for the patients under 3 years of age with the generalized additive model for location, scale, and shape (GAMLSS). Second, the growth patterns of the patients with hydrocephalus who underwent neurosurgical procedures such as foramen magnum decompression (FMD) and ventriculoperitoneal (VP) shunt were analyzed.

RESULTS

There were 125 achondroplasia patients, including 67 males and 58 females. Among 125 patients, 46 underwent FMD, and 5 underwent VP shunt. As short stature and macrocephaly were typical characteristics of achondroplasia, the height of achondroplasia was lower than that of the general population, and HC in achondroplasia showed accelerated growth postnatally. There were no significant changes in HC in hydrocephalus patients before they underwent neurosurgical procedures. The influence of hydrocephalus on the growth patterns of HC in achondroplasia seemed insignificant.

CONCLUSION

Growth references for height, weight, and HC in young achondroplasia patients were constructed. It is the first report of growth patterns of achondroplasia in Korea. Unlike other pediatric patients, the diagnosis of hydrocephalus and the necessity of neurosurgical procedures are hard to be predicted with HC in achondroplasia. Neuroimaging should be considered for achondroplasia patients with neurological symptoms.

Achondroplasia in Latin America: practical recommendations for the multidisciplinary care of pediatric patients

Background

Achondroplasia is the most common bone dysplasia associated with disproportionate short stature, and other comorbidities, such as foramen magnum stenosis, thoracolumbar kyphosis, lumbar hyperlordosis, genu varum and spinal compression. Additionally, patients affected with this condition have higher frequency of sleep disorders, ear infections, hearing loss and slowed development milestones. Considering these clinical features, we aimed to summarize the regional experts’ recommendations for the multidisciplinary management of patients with achondroplasia in Latin America, a vast geographic territory with multicultural characteristics and with socio-economical differences of developing countries.

Methods

Latin American experts (from Argentina, Brazil, Chile and Colombia) particiáted of an Advisory Board meeting (October 2019), and had a structured discussion how patients with achondroplasia are followed in their healthcare centers and punctuated gaps and opportunities for regional improvement in the management of achondroplasia.

Results

Practical recommendations have been established for genetic counselling, prenatal diagnosis and planning of delivery in patients with achondroplasia. An outline of strategies was added as follow-up guidelines to specialists according to patient developmental phases, amongst them neurologic, orthopedic, otorhinolaryngologic, nutritional and anthropometric aspects, and related to development milestones. Additionally, the role of physical therapy, physical activity, phonoaudiology and other care related to the quality of life of patients and their families were discussed. Preoperative recommendations to patients with achondroplasia were also included.

Conclusions

This study summarized the main expert recommendations for the health care professionals management of achondroplasia in Latin America, reinforcing that achondroplasia-associated comorbidities are not limited to orthopedic concerns.

Pharmacokinetics and Exposure-Response of Vosoritide in Children with Achondroplasia

BACKGROUND AND OBJECTIVE

Vosoritide, an analog of C-type natriuretic peptide, has been developed for the treatment of children with achondroplasia. The pharmacokinetics of vosoritide and relationships between plasma exposure and efficacy, biomarkers, and safety endpoints were evaluated in a phase II, open-label, dose-escalation study (N = 35 patients aged 5-14 years who received daily subcutaneous injections for 24 months) and a phase III, double-blind, placebo-controlled study (N = 60 patients aged 5-18 years randomized to receive daily subcutaneous injections for 52 weeks).

METHODS

Pharmacokinetic parameters for both studies were obtained from non-compartmental analysis. Potential correlations between vosoritide exposure and changes in annualized growth velocity, collagen type X marker (CXM; a biomarker of endochondral ossification), cyclic guanosine monophosphate (cGMP; a biomarker of pharmacological activity), heart rate, and systolic and diastolic blood pressures were then evaluated.

RESULTS

The exposure-response relationships for changes in both annualized growth velocity and the CXM biomarker saturated at 15 μg/kg, while systemic pharmacological activity, as measured by urinary cGMP, was near maximal or saturated at exposures obtained at the highest dose studied (i.e. 30 μg/kg). This suggested that the additional bioactivity was likely in tissues not related to endochondral bone formation. In the phase III study, following subcutaneous administration at the recommended dose of 15 μg/kg to patients with achondroplasia aged 5-18 years, vosoritide was rapidly absorbed with a median time to maximal plasma concentration (C_max) of 15 minutes, and cleared with a mean half-life of 27.9 minutes after 52 weeks of treatment. Vosoritide exposure (C_max and area under the concentration-time curve [AUC]) was consistent across visits. No evidence of accumulation with once-daily dosing was observed. Total anti-vosoritide antibody (TAb) responses were detected in the serum of 25 of 60 (42%) treated patients in the phase III study, with no apparent impact of TAb development noted on annualized growth velocity or vosoritide exposure. Across the exposure range obtained with 15 µg/kg in the phase III study, no meaningful correlations between vosoritide plasma exposure and changes in annualized growth velocity or CXM, or changes from predose heart rate, and systolic or diastolic blood pressures were observed.

CONCLUSIONS

The results support the recommended dose of vosoritide 15 µg/kg for once-daily subcutaneous administration in patients with achondroplasia aged ≥ 5 years whose epiphyses are not closed.

CLINICAL TRIALS REGISTRATION

NCT02055157, NCT03197766, and NCT01603095.