Emerging targeted drug therapies in skeletal dysplasias

New treatments for children with achondroplasia

Achondroplasia is the most common form of dwarfism in humans, caused by a common pathogenic variant in the gene encoding fibroblast growth factor receptor 3, FGFR3, which impairs the process of endochondral ossification of the growing skeleton. In this Review, we outline the clinical and genetic hallmarks of achondroplasia and related FGFR3 conditions, the natural history and impact of achondroplasia over a patient's lifespan, and diagnosis and management options. We then focus on the new and emerging drug therapies that target the underlying pathogenesis of this condition. These new options are changing the natural growth patterns of achondroplasia, with the prospect of better long-term health outcomes for patients.

Development of the Screening Tool for Everyday Mobility and Symptoms (STEMS) for skeletal dysplasia

BACKGROUND

Skeletal dysplasia are genetic disorders of cartilage and bone, characterized by impairments commonly resulting in short stature, altered movement biomechanics, pain, fatigue and reduced functional performance. While current tools quantify functional mobility performance, they have not been standardly used in this population group and do not capture patient-reported symptoms such as pain or fatigue. This study evaluated a new tool, the Screening Tool for Everyday Mobility and Symptoms (STEMS), designed to accurately and objectively assess functional mobility and associated symptomology for individuals with skeletal dysplasia.

METHODS

Individuals aged 5-75 years with a skeletal dysplasia completed the STEMS, the Functional Mobility Scale (FMS) and Six Minute Walk Test (6MWT). The correlation among the STEMS, use of mobility aides, FMS and 6MWT normalised for leg length was calculated. One-way analysis of variance compared the STEMS symptomatology to normalised 6MWT distance.

RESULTS

One hundred and fifty individuals with skeletal dysplasia (76 achondroplasia, 42 osteogenesis imperfecta, 32 other; 74 < 18 years, 76 ≥ 18 years) participated. Almost two thirds of the group reported pain and/or fatigue when mobilising at home, at work or school and within the community, but only twenty percent recorded use of a mobility device. The STEMS setting category demonstrated highly significant correlations with the corresponding FMS category (r = - 0.983 to - 0.0994, all p < 0.001), and a low significant correlation with the normalised 6MWT distance (r = - 0.323 to - 0.394, all p < 0.001). A decreased normalised 6MWT distance was recorded for individuals who reported symptoms of pain and/or fatigue when mobilising at home or at work/school (all p ≤ 0.004). Those who reported pain only when mobilising in the community had a normal 6MWT distance (p = 0.43-0.46).

CONCLUSIONS

The Screening Tool for Everyday Mobility and Symptoms (STEMS) is a useful new tool to identify and record mobility aide use and associated self-reported symptoms across three environmental settings for adults and children with skeletal dysplasia. The STEMS may assist clinicians to monitor individuals for changes in functional mobility and symptoms over time, identify individuals who are functioning poorly compared to peers and need further assessment, and to measure effectiveness of treatment interventions in both clinical and research settings.

Equitable Expanded Carrier Screening Needs Indigenous Clinical and Population Genomic Data

Expanded carrier screening (ECS) for recessive monogenic diseases requires prior knowledge of genomic variation, including DNA variants that cause disease. The composition of pathogenic variants differs greatly among human populations, but historically, research about monogenic diseases has focused mainly on people with European ancestry. By comparison, less is known about pathogenic DNA variants in people from other parts of the world. Consequently, inclusion of currently underrepresented Indigenous and other minority population groups in genomic research is essential to enable equitable outcomes in ECS and other areas of genomic medicine. Here, we discuss this issue in relation to the implementation of ECS in Australia, which is currently being evaluated as part of the national Government's Genomics Health Futures Mission. We argue that significant effort is required to build an evidence base and genomic reference data so that ECS can bring significant clinical benefit for many Aboriginal and/or Torres Strait Islander Australians. These efforts are essential steps to achieving the Australian Government's objectives and its commitment "to leveraging the benefits of genomics in the health system for all Australians." They require culturally safe, community-led research and community involvement embedded within national health and medical genomics programs to ensure that new knowledge is integrated into medicine and health services in ways that address the specific and articulated cultural and health needs of Indigenous people. Until this occurs, people who do not have European ancestry are at risk of being, in relative terms, further disadvantaged.

Best practice guidelines for management of spinal disorders in skeletal dysplasia

BACKGROUND

Disorders of the spine present a common and difficult management concern in patients with skeletal dysplasia. Due to the rarity of these conditions however, the literature, largely consisting of small, single institution case series, is sparse in regard to well-designed studies to support clinical decision making in these situations.

METHODS

Using the Delphi method, an international, multi-disciplinary group of individuals, with significant experience in the care of patients with skeletal dysplasia, convened to develop multi-disciplinary, "best practice" guidelines in the care of spinal disorders in patients with skeletal dysplasia.

RESULTS

Starting with 33 statements, the group a developed a list of 31 "best practice" guidelines.

CONCLUSIONS

The guidelines are presented and discussed to provide context for clinicians in their decision making in this often-challenging realm of care.

The evolving therapeutic landscape of genetic skeletal disorders

BACKGROUND

Rare bone diseases account for 5% of all birth defects yet very few have personalised treatments. Developments in genetic diagnosis, molecular techniques and treatment technologies however, are leading to unparalleled therapeutic advance. This review explores the evolving therapeutic landscape of genetic skeletal disorders (GSDs); the key conditions and there key differentials.

METHODS

A retrospective literature based review was conducted in December 2018 using a systematic search strategy for relevant articles and trials in Pubmed and clinicaltrials.gov respectively. Over 140 articles and 80 trials were generated for review.

RESULTS

Over 20 personalised therapies are discussed in addition to several novel disease modifying treatments in over 25 GSDs. Treatments discussed are at different stages from preclinical studies to clinical trials and approved drugs, including; Burosumab for X-linked hypophosphatemia, Palovarotene for Hereditary Multiple Exostoses, Carbamazepine for Metaphyseal Chondrodysplasia (Schmid type), Lithium carbonate and anti-sclerostin therapy for Osteoporosis Pseudoglioma syndrome and novel therapies for Osteopetrosis. We also discuss therapeutic advances in Achondroplasia, Osteogenesis Imperfecta (OI), Hypophosphotasia (HPP), Fibrodysplasia Ossificans Progressiva, and RNA silencing therapies in preclinical studies for OI and HPP.

DISCUSSION

It is an exciting time for GSD therapies despite the challenges of drug development in rare diseases. In discussing emerging therapies, we explore novel approaches to drug development from drug repurposing to in-utero stem cell transplants. We highlight the improved understanding of bone pathophysiology, genetic pathways and challenges of developing gene therapies for GSDs.

Current knowledge of medical complications in adults with achondroplasia: A scoping review

This article provides an overview of the current knowledge on medical complications, health characteristics, and psychosocial issues in adults with achondroplasia. We have used a scoping review methodology particularly recommended for mapping and summarizing existing research evidence, and to identify knowledge gaps. The review process was conducted in accordance with the PRISMA‐ScR guidelines (Preferred Reporting Items for Systematic reviews and Meta‐Analyses Extension for Scoping Reviews). The selection of studies was based on criteria predefined in a review protocol. Twenty‐nine publications were included; 2 reviews, and 27 primary studies. Key information such as reference details, study characteristics, topics of interest, main findings and the study author's conclusion are presented in text and tables. Over the past decades, there has only been a slight increase in publications on adults with achondroplasia. The reported morbidity rates and prevalence of medical complications are often based on a few studies where the methodology and representativeness can be questioned. Studies on sleep‐related disorders and pregnancy‐related complications were lacking. Multicenter natural history studies have recently been initiated. Future studies should report in accordance to methodological reference standards, to strengthen the reliability and generalizability of the findings, and to increase the relevance for implementing in clinical practice.

Best practice guidelines regarding diagnosis and management of patients with type II collagen disorders

PURPOSE

Skeletal dysplasias comprise a heterogeneous group of inherited disorders of development, growth, and maintenance of the human skeleton. Because of their relative rarity and wide phenotypic variability, patients should be accurately identified, uniformly assessed, and managed by clinicians who are aware of their potential complications and possess the knowledge and resources to treat them effectively. This study presents expert guidelines developed to improve the diagnosis and management of patients with type II collagen skeletal disorders to optimize clinical outcomes.

METHODS

A panel of 11 multidisciplinary international experts in the field of skeletal dysplasia participated in a Delphi process, which comprised analysis of a thorough literature review with subsequent generation of 26 diagnosis and care recommendations, followed by two rounds of anonymous voting with an intervening face-to-face meeting. Those recommendations with more than 80% agreement were considered as consensual.

RESULTS

After the first voting round, consensus was reached to support 12 of 26 (46%) statements. After the panel discussion, the group reached consensus on 22 of 24 revised statements (92%).

CONCLUSIONS

Consensus-based, expert best practice guidelines developed as a standard of care to assist accurate diagnosis, minimize associated health risks, and improve clinical outcomes for patients with type II collagen skeletal dysplasias.

Best practice guidelines regarding prenatal evaluation and delivery of patients with skeletal dysplasia

BACKGROUND

Skeletal dysplasia comprises a heterogeneous and collectively common group of inherited disorders of development, growth, and maintenance of the human skeleton. There is potential for increased perinatal morbidity and mortality in pregnant women who themselves have skeletal dysplasia, and for affected fetuses where skeletal dysplasia is suspected in utero.

OBJECTIVE

We sought to establish guidelines for perinatal health care professionals who should be aware of these risks, to optimize maternal and child health pregnancy outcomes through best prenatal and delivery management practices.

STUDY DESIGN

A panel of 13 multidisciplinary international experts participated in a Delphi process, which comprised consideration of thorough literature review and a list of 54 possible care recommendations subject to 2 rounds of anonymous voting and a face-to-face meeting. Those recommendations with >80% agreement were considered as consensual.

RESULTS

During the first round, consensus was reached to support 30 out of the 54 statements. After the panel discussion, the group reached consensus on 40 statements. These statements include guidelines for the evaluation and treatment of pregnant women with skeletal dysplasia and for the unborn child with or suspected to have skeletal dysplasia.

CONCLUSION

Consensus-based best practice guidelines are provided as a minimum of standard care to minimize associated health risks, and improve clinical outcomes for patients with skeletal dysplasia.

Skeletal Dysplasias: Growing Therapy for Growing Bones

Skeletal dysplasias represent a large and diverse group of rare conditions affecting collagen and bone. They can be clinically classified based on radiographic and physical features, and many can be further defined at a molecular level (Bonafe et al., 2015). Early diagnosis is critical to proper medical management including pharmacologic treatment when available. Patients with severe skeletal dysplasias often have small chests with respiratory insufficiency or airway obstruction and require immediate intubation after birth. Thereafter a variety of orthopedic, neurosurgical, pulmonary, otolaryngology interventions may be needed. In terms of definitive treatment for skeletal dysplasias, there are few pharmacotherapeutic options available for the majority of these conditions. We sought to describe therapies that are currently available or under investigation for skeletal dysplasias.