Hydrops fetalis due to loss of function of hNav1.4 channel via compound heterozygous variants.

Hydrops fetalis, characterized by abnormal fluid accumulation in fetuses, presents a significant risk of stillbirth and neonatal mortality. Although the etiology of nonimmune hydrops fetalis (NIHF) is multifaceted, recent studies have highlighted genetic factors as crucial determinants. This study focused on a family with three consecutive stillbirths, each with pronounced hydrops fetalis. Using whole-exome sequencing (WES), we identified compound heterozygous variants of the SCN4A gene encoding the voltage-gated sodium channel of the skeletal muscle (hNav1.4), c.2429T>A p.L810Q and c.4556T>C p.F1519S, in all three deceased infants. A functional analysis conducted using the whole-cell patch-clamp technique revealed loss-of-function defects in both variant channels, with F1519S exhibiting a complete loss of ionic current and L810Q showing a reduced channel opening. These findings support the pathogenicity of SCN4A variants in NIHF and underscore the significance of functional studies in elucidating genotype-phenotype correlations. Furthermore, our study emphasizes the diagnostic value of WES in cases of NIHF in where standard genetic testing fails to identify causative variants.

Burosumab treatment of X-linked hypophosphatemia patients: interim analysis of the SUNFLOWER longitudinal, observational cohort study.

X-linked hypophosphatemia (XLH) is a genetic disease that results in excessive FGF23, chronic hypophosphatemia, and musculoskeletal abnormalities, with affected patients experiencing symptoms such as bone pain, bone deformity, fracture, and pseudofracture. Burosumab is a fully human monoclonal antibody that binds to FGF23, improving lowered serum 1,25(OH)2D and phosphate levels in patients with XLH. There are insufficient data on the use of burosumab, its safety, and the outcomes of treated patients in a real-world setting. The SUNFLOWER (Study of longitUdinal observatioN For patients with X-Linked hypOphosphatemic rickets/osteomalacia in collaboration With Asian partnERs) study is an ongoing longitudinal, observational cohort study of patients with XLH in Japan and South Korea. Enrollment occurred between April 2018 and December 2020. This interim analysis compared the background characteristics of patients who received burosumab with those who did not, and assessed improvements in biomarkers, physical and motor function, health-related quality-of-life (HRQOL) and other patient-reported outcome (PRO) measures, as well as the safety of burosumab treatment in 143 Japanese patients from 15 institutions over 6 mo. The patients had a median [interquartile range] age of 17.5 [11.0, 38.8] yr and 98 (68.5%) were female. Among patients aged <18 and ≥18 yr, 40/73 (54.8%) and 25/70 (35.7%) received burosumab, respectively. More patients aged ≥18 who received burosumab had bone pain at baseline vs those not treated with burosumab (6/25, 24.0% vs 2/45, 4.4%, p=.021). Patients treated with burosumab had improved serum phosphate and 1,25(OH)2D levels; moreover, rickets severity and HRQOL/PRO measures, such as pain, appeared to improve over 6 mo of burosumab treatment, and no new safety concerns were identified. This study identified trends in the background characteristics of patients with XLH who receive burosumab in real-world clinical practice. Furthermore, the results support the use of burosumab therapy in real-world settings.

Growth and respiratory status at 3 years of age after moderate preterm, late preterm and early term births: the Japan Environment and Children's Study.

OBJECTIVE: To assess the association between gestational age at birth and the risk of growth failure and respiratory symptoms at 3 years of age. DESIGN: Cohort study using the Japan Environment and Children's Study database. PATIENTS: A total of 86 158 singleton infants born without physical abnormalities at 32-41 weeks of gestation were enrolled between January 2011 and March 2014. MAIN OUTCOME MEASURES: Growth failure (weight <10th percentile and height <10th percentile) and respiratory symptoms (asthma and wheezing) at 3 years of age. METHODS: Logistic regression analysis was used to evaluate the risk of growth failure and respiratory symptoms in the moderately preterm, late preterm and early term groups compared with the full-term group after adjusting for socioeconomic and perinatal factors. Multiple imputation was used to reduce the attrition bias related to missing data. RESULTS: The respective adjusted ORs (95% CI) of growth failure and respiratory symptoms for the moderate preterm, late preterm and early term groups compared with the full-term group were as follows: weight <10th percentile, 2.29 (1.48-3.54), 1.43 (1.24-1.71) and 1.20 (1.12-1.28); height <10th percentile, 2.34 (1.59-3.45), 1.42 (1.25-1.60) and 1.15 (1.09-1.22); asthma, 1.63 (1.06-2.50), 1.21 (1.04-1.41) and 1.16 (1.09-1.23); and wheezing, 1.39 (1.02-1.90), 1.37 (1.25-1.51) and 1.11 (1.06-1.17). CONCLUSION: Moderate preterm, late preterm and early term births were associated with a higher risk of growth failure and respiratory symptoms at 3 years of age than full-term births, with an inverse dose-response pattern.

New insights into the landscape of ALPL gene variants in patients with hypophosphatasia from the Global HPP Registry.

Hypophosphatasia (HPP) is a rare, inherited metabolic disease characterized by low tissue-nonspecific alkaline phosphatase activity due to ALPL gene variants. We describe ALPL variants from the observational, prospective, multinational Global HPP Registry. Inclusion in the analysis required a diagnosis of HPP, low serum ALP activity, and ≥1 ALPL variant. Of 1176 patients enrolled as of September 2022, 814 met inclusion criteria in Europe (48.9%), North America (36.7%), Japan (10.2%), Australia (2.6%), and elsewhere (1.6%). Most patients (74.7%) had 1 ALPL variant; 25.3% had ≥2 variants. Nearly all patients (95.6%) had known disease-causing variants; 4.4% had variants of uncertain significance. Disease-causing variants were predominantly missense (770/1556 alleles). The most common variants were c.571G>A (102/1628 alleles), c.1250A>G (66/1628 alleles), and c.1559del (61/1628 alleles). Variant profiles were generally consistent, except in Japan, where a higher proportion of patients (68.7%) had ≥2 ALPL variants, likely because more had disease onset before age 6 months (53.0% vs. 10.1%-23.1% elsewhere). Frameshift mutations (61/164 alleles) and inframe deletions (7/164 alleles) were more common in Japan. Twenty-three novel variants were discovered, each in a single geographic region, predominantly Europe. Analyses confirmed previously known ALPL variants, identified novel variants, and characterized geographic variation in frequency and type of ALPL variants in a large population.

Promising horizons in achondroplasia along with the development of new drugs.

Achondroplasia (ACH) is a representative skeletal disorder characterized by rhizomelic shortened limbs and short stature. ACH is classified as belonging to the fibroblast growth factor receptor 3 (FGFR3) group. The downstream signal transduction of FGFR3 consists of STAT1 and RAS/RAF/MEK/ERK pathways. The mutant FGFR3 found in ACH is continuously phosphorylated and activates downstream signals, resulting in abnormal proliferation and differentiation of chondrocytes in the growth plate and cranial base synchondrosis. A patient registry has been developed and has contributed to revealing the natural history of ACH patients. Concerning the short stature, the adult height of ACH patients ranges between 126.7-135.2 cm for men and 119.9-125.5 cm for women in many countries. Along with severe short stature, foramen magnum stenosis and spinal canal stenosis are major complications: the former leads to sleep apnea, breathing disorders, myelopathy, hydrocephalus, and sudden death, and the latter causes pain in the extremities, numbness, muscle weakness, movement disorders, intermittent claudication, and bladder-rectal disorders. Growth hormone treatment is available for ACH only in Japan. However, the effect of the treatment on adult height is not satisfactory. Recently, the neutral endopeptidase-resistant CNP analogue vosoritide has been approved as a new drug for ACH. Additionally in development are a tyrosine kinase inhibitor, a soluble FGFR3, an antibody against FGFR3, meclizine, and the FGF2-aptamer. New drugs will bring a brighter future for patients with ACH.

Development of a Weight-Band Dosing Approach for Vosoritide in Children with Achondroplasia Using a Population Pharmacokinetic Model.

BACKGROUND AND OBJECTIVE: Vosoritide is a recently approved therapy for achondroplasia, the most common form of disproportionate short stature, that has been shown to be well tolerated and effective in increasing linear growth. This study aimed to develop a population pharmacokinetic (PPK) model to characterize pharmacokinetics (PK) of vosoritide and establish a weight-band dosing regimen. METHODS: A PPK model was developed using data from five clinical trials in children with achondroplasia (aged 0.95-15 years) who received daily per-kg doses of vosoritide. The model was used to simulate expected exposures in children with a refined weight-band dosing regimen. Simulated exposure was compared with the observed exposure from the pivotal clinical trial to evaluate appropriateness of the weight-band dosing regimen. RESULTS: A one-compartment model with a change-point first-order absorption and first-order elimination accurately described PK of vosoritide in children with achondroplasia. Body weight was found to be a predictor of vosoritide's clearance and volume of distribution. Additionally, it was observed that dosing solution concentration and duration of treatment influenced bioavailability. The weight-band dosing regimen resulted in simulated exposures that were within the range demonstrated to be well tolerated and effective in the pivotal clinical trial and showed improved consistency in drug exposure across the achondroplasia population. CONCLUSIONS: The weight-band dosing regimen reduced the number of recommended dose levels by body weight and is expected to simplify dosing for children with achondroplasia and their caregivers. CLINICAL TRIAL REGISTRATION: NCT02055157, NCT02724228, NCT03197766, NCT03424018, and NCT03583697.

Effectiveness of asfotase alfa for treatment of adults with hypophosphatasia: results from a global registry.

BACKGROUND: Hypophosphatasia (HPP) is a rare inherited disease caused by deficient activity of tissue-nonspecific alkaline phosphatase. Many adults with HPP have a high burden of disease, experiencing chronic pain, fatigue, limited mobility, and dental issues, contributing to decreased health-related quality of life (HRQoL). HPP may be treated with the enzyme replacement therapy asfotase alfa though real-world data in adults are limited. This analysis was conducted to assess the clinical effectiveness of asfotase alfa among adults in the Global HPP Registry. METHODS: The Global HPP Registry is an observational, prospective, multinational study. Adults ≥ 18 years of age were included in this analysis if they had serum alkaline phosphatase (ALP) activity below the age- and sex-adjusted reference ranges, and/or ALPL variant(s), and received asfotase alfa for ≥ 6 months. Mobility was assessed with the 6-Minute Walk Test (6MWT), and patient-reported outcomes tools were used to assess pain (Brief Pain Inventory-Short Form), quality of life (36-item Short Form Health Survey, version 2 [SF-36v2]), and disability (Health Assessment Questionnaire-Disability Index) at multiple time points from baseline through Month 36. Data were collected as per usual standard of care; patients may not have contributed data at all time points. RESULTS: A total of 190 patients met the inclusion criteria. For patients with ≥ 1 follow-up measurement, the mean distance achieved on 6MWT increased from 404 m (range 60-632 m) at baseline (n = 31) to 484 m at Month 12 (range 240-739 m; n = 18) and remained above baseline through Month 36 (n = 7). Improvements in mean self-reported pain severity scores ranged from - 0.72 (95% CI: - 1.23, - 0.21; n = 38) to - 1.13 (95% CI: - 1.76, - 0.51; n = 26) and were observed at all time points. Improvements in the Physical Component Summary score of SF-36v2 were achieved by Month 6 and sustained throughout follow-up. There was a trend toward improvement in the Mental Component Summary score of SF-36v2 at most time points, with considerable fluctuations from Months 12 (n = 28) through 36 (n = 21). The most frequent adverse events were injection site reactions. CONCLUSIONS: Adults with HPP who received asfotase alfa for ≥ 6 months experienced improvements in mobility, physical function, and HRQoL, which were maintained over 3 years of follow-up. REGISTRATION: NCT02306720; EUPAS13514.

The 2023 Guidelines for the management and treatment of glucocorticoid-induced osteoporosis.

INTRODUCTION: Although synthetic glucocorticoids (GCs) are commonly used to treat autoimmune and other diseases, GC induced osteoporosis (GIOP) which accounts for 25% of the adverse reactions, causes fractures in 30-50% of patients, and markedly decreases their quality of life. In 2014, the Japanese Society for Bone and Mineral Research (JSBMR) published the revised guidelines for the management and treatment of steroid-induced osteoporosis, providing the treatment criteria based on scores of risk factors, including previous fractures, age, GC doses, and bone mineral density, for patients aged ≥18 years who are receiving GC therapy or scheduled to receive GC therapy for ≥3 months. MATERIALS AND METHODS: The Committee on the revision of the guidelines for the management and treatment of GIOP of the JSBMR prepared 17 clinical questions (CQs) according to the GRADE approach and revised the guidelines for the management and treatment of GIOP through systematic reviews and consensus conferences using the Delphi method. RESULTS: Bisphosphonates (oral and injectable formulations), anti-RANKL antibody teriparatide, eldecalcitol, or selective estrogen receptor modulators are recommended for patients who has received or scheduled for GC therapy with risk factor scores of ≥3. It is recommended that osteoporosis medication is started concomitantly with the GC therapy for the prevention of fragility fractures in elderly patients. CONCLUSION: The 2023 guidelines for the management and treatment of GIOP was developed through systematic reviews and consensus conferences using the Delphi method.

Comprehensive analyses of neurodevelopmental outcomes and quality of life of children with biliary atresia.

OBJECTIVES: To holistically evaluate neurodevelopmental outcomes and quality of life (QOL) of Japanese patients with biliary atresia (BA) and to investigate the factors associated with the outcomes. METHODS: This study enrolled patients with BA aged 5-18 years who visited Osaka University Hospital in 2021. Neurodevelopmental assessments were performed to evaluate intellectual ability, cognitive functions and adaptive skill levels. Furthermore, emotional and behavioral issues, characteristics of attention deficit hyperactivity disorder, and QOL were concomitantly assessed in the same cohort. Biochemical and social factors associated with the results were examined. RESULTS: Fifty-three patients, with a median age of 11.2 years were included in the analyses. Patients with BA had a significantly lower Full-Scale Intelligence Quotient or developmental quotient (FSIQ/DQ) score and Vineland Adaptive Behavior Scale (VABS) composite score than the general Japanese population. Household education level and short stature were associated with low and borderline FSIQ/DQ and VABS composite scores, respectively. Among patients with low and borderline FSIQ/DQ scores, those with average or high VABS composite scores received significantly less neuroeducational care than those with low and borderline VABS composite scores. Despite the low FSIQ/DQ and VABS composite scores, the total QOL scores were higher than those of the general population. CONCLUSION: Patients with BA had intellectual and behavioral impairments. Notably, patients with intellectual impairments are overlooked and not followed up, especially if adaptive skills are maintained.

Clinical outcomes and medical management of achondroplasia in Japanese children: A retrospective medical record review of clinical data.

Achondroplasia (ACH) is a rare, autosomal dominant skeletal dysplasia characterized by short stature, characteristic facial configuration, and trident hands. Before vosoritide approval in Japan, patients with ACH could start growth hormone (GH) treatment at age 3 years. However, ACH and its treatment in young Japanese children have not been studied. This retrospective, longitudinal, medical records-based cohort study (before vosoritide approval) summarized symptoms, complications, monitoring, surgery/interventions, and height with/without GH in Japanese patients with ACH <5 years. Complications were observed in 89.2% of all 37 patients; 75.7% required surgery or intervention. All patients were monitored by magnetic resonance imaging; 73.0% had foramen magnum stenosis, while 54.1% had Achondroplasia Foramen Magnum Score 3 or 4. Of 28 GH-treated patients, 22 initiating at age 3 years were generally taller after 12 months versus 9 non-GH-treated patients. Mean annual growth velocity significantly increased from age 2 to 3 versus 3 to 4 years in GH-treated patients (4.37 vs. 7.23 cm/year; p = 0.0014), but not in non-GH-treated patients (4.94 vs. 4.20 cm/year). The mean height at age 4 years with/without GH was 83.6/79.8 cm. These results improve our understanding of young patients with ACH in Japan and confirm that early diagnosis of ACH and monitoring of complications help facilitate appropriate interventions.

Complex intrinsic abnormalities in osteoblast lineage cells of X-linked hypophosphatemia: Analysis of human iPS cell models generated by CRISPR/Cas9-mediated gene ablation.

X-linked hypophosphatemia (XLH) is caused by inactivating variants of the phosphate regulating endopeptidase homolog X-linked (PHEX) gene. Although the overproduction of fibroblast growth factor 23 (FGF23) is responsible for hypophosphatemia and impaired vitamin D metabolism, the pathogenesis of XLH remains unclear. We herein generated PHEX-knockout (KO) human induced pluripotent stem (iPS) cells by applying CRISPR/Cas9-mediated gene ablation to an iPS clone derived from a healthy male, and analyzed PHEX-KO iPS cells with deletions extending from exons 1 to 3 and frameshifts by inducing them to differentiate into the osteoblast lineage. We confirmed the increased production of FGF23 in osteoblast lineage cells differentiated from PHEX-KO iPS cells. In vitro mineralization was enhanced in osteoblast lineage cells from PHEX-KO iPS cells than in those from isogenic control iPS cells, which reminded us of high bone mineral density and enthesopathy in patients with XLH. The extracellular level of pyrophosphate (PPi), an inhibitor of mineralization, was elevated, and this increase appeared to be partly due to the reduced activity of tissue non-specific alkaline phosphatase (TNSALP). Osteoblast lineage cells derived from PHEX-KO iPS cells also showed the increased expression of multiple molecules such as dentine matrix protein 1, osteopontin, RUNX2, FGF receptor 1 and early growth response 1. This gene dysregulation was similar to that in the osteoblasts/osteocytes of Phex-deficient Hyp mice, suggesting that common pathogenic mechanisms are shared between human XLH and Hyp mice. Moreover, we found that the phosphorylation of CREB was markedly enhanced in osteoblast lineage cells derived from PHEX-KO iPS cells, which appeared to be associated with the up-regulation of the parathyroid hormone related protein gene. PHEX deficiency also affected the response of the ALPL gene encoding TNSALP to extracellular Pi. Collectively, these results indicate that complex intrinsic abnormalities in osteoblasts/osteocytes underlie the pathogenesis of human XLH.

The Global ALPL gene variant classification project: Dedicated to deciphering variants.

BACKGROUND: Hypophosphatasia (HPP) is an inherited multisystem disorder predominantly affecting the mineralization of bones and teeth. HPP is caused by pathogenic variants in ALPL, which encodes tissue non-specific alkaline phosphatase (TNSALP). Variants of uncertain significance (VUS) cause diagnostic delay and uncertainty amongst patients and health care providers. RESULTS: The ALPL gene variant database (https://alplmutationdatabase.jku.at/) is an open-access archive for interpretation of the clinical significance of variants reported in ALPL. The database contains coding and non-coding variants, including single nucleotide variants, insertions/deletions and structural variants affecting coding or non-coding sequences of ALPL. Each variant in the database is displayed with details explaining the corresponding pathogenicity, and all reported genotypes and phenotypes, including references. In 2021, the ALPL gene variant classification project was established to reclassify VUS and continuously assess and update genetic, phenotypic, and functional variant information in the database. For this purpose, the database provides a unique submission system for clinicians, geneticists, genetic counselors, and researchers to submit VUS within ALPL for classification. An international, multidisciplinary consortium of HPP experts has been established to reclassify the submitted VUS using a multi-step process adhering to the stringent ACMG/AMP variant classification guidelines. These steps include a clinical phenotype assessment, deep literature research including artificial intelligence technology, molecular genetic assessment, and in-vitro functional testing of variants in a co-transfection model to measure ALP residual activity. CONCLUSION: This classification project and the ALPL gene variant database will serve the global medical community, widen the genotypic and phenotypic HPP spectrum by reporting and characterizing new ALPL variants based on ACMG/AMP criteria and thus facilitate improved genetic counseling and medical decision-making for affected patients and families. The project may also serve as a gold standard framework for multidisciplinary collaboration for variant interpretation in other rare diseases.

Vosoritide therapy in children with achondroplasia aged 3-59 months: a multinational, randomised, double-blind, placebo-controlled, phase 2 trial.

BACKGROUND: Vosoritide is a recombinant C-type natriuretic peptide analogue that increases annualised growth velocity in children with achondroplasia aged 5-18 years. We aimed to assess the safety and efficacy of vosoritide in infants and children younger than 5 years. METHODS: This double-blind, randomised, placebo-controlled, phase 2 trial was done in 16 hospitals across Australia, Japan, the UK, and the USA. Children younger than 60 months with a clinical diagnosis of achondroplasia confirmed by genetic testing and who had completed a baseline growth study or observation period were enrolled into one of three sequential cohorts based on age at screening: 24-59 months (cohort 1); 6-23 months (cohort 2); and 0-5 months (cohort 3). Each cohort included sentinels who received vosoritide to determine appropriate daily drug dose, with the remainder randomly assigned (1:1) within each age stratum (except in Japan, where participants were randomly assigned within each cohort) to receive daily subcutaneous injections of vosoritide (30·0 µg/kg for infants aged 0-23 months; 15·0 µg/kg for children aged 24-59 months) or placebo for 52 weeks. Participants, caregivers, investigators, and the sponsor were masked to treatment assignment. The first primary outcome was safety and tolerability, assessed in all participants who received at least one study dose. The second primary outcome was change in height Z score at 52 weeks from baseline, analysed in all randomly assigned participants. This trial is registered with EudraCT, 2016-003826-18, and ClinicalTrials.gov, NCT03583697. FINDINGS: Between May 13, 2018, and March 1, 2021, 75 participants were recruited (37 [49%] females). 11 were assigned as sentinels, whereas 32 were randomly assigned to receive vosoritide and 32 placebo. Two participants discontinued treatment and the study: one in the vosoritide group (death) and one in the placebo group (withdrawal). Adverse events occurred in all 75 (100%) participants (annual rate 204·5 adverse events per patient in the vosoritide group and 73·6 per patient in the placebo group), most of which were transient injection-site reactions and injection-site erythema. Serious adverse events occurred in three (7%) participants in the vosoritide group (decreased oxygen saturation, respiratory syncytial virus bronchiolitis and sudden infant death syndrome, and pneumonia) and six (19%) participants in the placebo group (petit mal epilepsy, autism, gastroenteritis, vomiting and parainfluenza virus infection, respiratory distress, and skull fracture and otitis media). The least-squares mean difference for change from baseline in height Z score between the vosoritide and placebo groups was 0·25 (95% CI -0·02 to 0·53). INTERPRETATION: Children with achondroplasia aged 3-59 months receiving vosoritide for 52 weeks had a mild adverse event profile and gain in the change in height Z score from baseline. FUNDING: BioMarin Pharmaceutical.