Minimum effective betamethasone dosage on the neurological phenotype in patients with ataxia-telangiectasia: a multicenter observer-blind study

Ataxia-telangiectasia clinical trial landscape and the obstacles to overcome

INTRODUCTION

Ataxia telangiectasia (A-T) is a life-limiting autosomal recessive disease characterized by cerebellar degeneration, ocular telangiectasias, and sinopulmonary disease. Since there is no cure for A-T, the standard of care is primarily supportive.

AREAS COVERED

We review clinical trials available in PubMed from 1990 to 2023 focused on lessening A-T disease burden. These approaches include genetic interventions, such as antisense oligonucleotides, designed to ameliorate disease progression in patients with select mutations. These approaches also include pharmacologic treatments that target oxidative stress, inflammation, and mitochondrial exhaustion, to attenuate neurological progression in A-T. Finally, we discuss the use of biological immunotherapies for the treatment of malignancies and granulomatous disease, along with other supportive therapies being used for the treatment of pulmonary disease and metabolic syndrome.

EXPERT OPINION

Barriers to successful genetic and pharmacologic interventions in A-T include the need for personalized treatment approaches based on patient-specific ATM mutations and phenotypes, lack of an animal model for the neurologic phenotype, and extreme rarity of disease making large-scale randomized trials difficult to perform. Ongoing efforts are needed to diagnose patients earlier, discover more effective therapies, and include more individuals in clinical trials, with the goal to lessen disease burden and to find a cure for patients with A-T.

The natural history of ataxia-telangiectasia (A-T): A systematic review

BACKGROUND

Ataxia-telangiectasia is an autosomal recessive, multi-system, and life-shortening disease caused by mutations in the ataxia-telangiectasia mutated gene. Although widely reported, there are no studies that give a comprehensive picture of this intriguing condition.

OBJECTIVES

Understand the natural history of ataxia-telangiectasia (A-T), as reported in scientific literature.

SEARCH METHODS

107 search terms were identified and divided into 17 searches. Each search was performed in PubMed, Ovid SP (MEDLINE) 1946-present, OVID EMBASE 1980 -present, Web of Science core collection, Elsevier Scopus, and Cochrane Library.

SELECTION CRITERIA

All human studies that report any aspect of A-T.

DATA COLLECTION AND ANALYSIS

Search results were de-duplicated, data extracted (including author, publication year, country of origin, study design, population, participant characteristics, and clinical features). Quality of case-control and cohort studies was assessed by the Newcastle-Ottawa tool. Findings are reported descriptively and where possible data collated to report median (interquartile range, range) of outcomes of interest.

MAIN RESULTS

1314 cases reported 2134 presenting symptoms. The most common presenting symptom was abnormal gait (1160 cases; 188 studies) followed by recurrent infections in classical ataxia-telangiectasia and movement disorders in variant ataxia-telangiectasia. 687 cases reported 752 causes of death among which malignancy was the most frequently reported cause. Median (IQR, range) age of death (n = 294) was 14 years 0 months (10 years 0 months to 23 years 3 months, 1 year 3 months to 76 years 0 months).

CONCLUSIONS

This review demonstrates the multi-system involvement in A-T, confirms that neurological symptoms are the most frequent presenting features in classical A-T but variants have diverse manifestations. We found that most individuals with A-T have life limited to teenage or early adulthood. Predominance of case reports, and case series demonstrate the lack of robust evidence to determine the natural history of A-T. We recommend population-based studies to fill this evidence gap.

Progressive Depletion of B and T Lymphocytes in Patients with Ataxia Telangiectasia: Results of the Italian Primary Immunodeficiency Network

Ataxia telangiectasia (AT) is a rare neurodegenerative genetic disorder due to bi-allelic mutations in the Ataxia Telangiectasia Mutated (ATM) gene. The aim of this paper is to better define the immunological profile over time, the clinical immune-related manifestations at diagnosis and during follow-up, and to attempt a genotype–phenotype correlation of an Italian cohort of AT patients. Retrospective data of 69 AT patients diagnosed between December 1984 and November 2019 were collected from the database of the Italian Primary Immunodeficiency Network. Patients were classified at diagnosis as lymphopenic (Group A) or non-lymphopenic (Group B). Fifty eight out of 69 AT patients (84%) were genetically characterized and distinguished according to the type of mutations in truncating/truncating (TT; 27 patients), non-truncating (NT)/T (28 patients), and NT/NT (5 patients). In 3 patients, only one mutation was detected. Data on age at onset and at diagnosis, cellular and humoral compartment at diagnosis and follow-up, infectious diseases, signs of immune dysregulation, cancer, and survival were analyzed and compared to the genotype. Lymphopenia at diagnosis was related per se to earlier age at onset. Progressive reduction of cellular compartment occurred during the follow-up with a gradual reduction of T and B cell number. Most patients of Group A carried bi-allelic truncating mutations, had a more severe B cell lymphopenia, and a reduced life expectancy. A trend to higher frequency of interstitial lung disease, immune dysregulation, and malignancy was noted in Group B patients. Lymphopenia at the onset and the T/T genotype are associated with a worst clinical course. Several mechanisms may underlie the premature and progressive immune decline in AT subjects.

Functional Classification of the ATM Variant c.7157C>A and In Vitro Effects of Dexamethasone

Most of the ATM variants associated with Ataxia Telangiectasia are still classified as variants with uncertain significance. Ataxia Telangiectasia is a multisystemic disorder characterized by “typical” and “atypical” phenotypes, with early-onset and severe symptoms or with late-onset and mild symptoms, respectively. Here we classified the c.7157C > A ATM variant found in homozygosity in two brothers of Lebanese ethnicity. The brothers presented with an atypical phenotype, showing less than 50% of the positive criteria considered for classification. We performed several in silico analyses to predict the effect of c.7157C > A at the DNA, mRNA and protein levels, revealing that the alteration causes a missense substitution in a highly conserved alpha helix in the FAT domain. 3D structural analyses suggested that the variant might be pathogenic due to either loss of activity or to a structural damage affecting protein stability. Our subsequent in vitro studies showed that the second hypothesis is the most likely, as indicated by the reduced protein abundance found in the cells carrying the variant. Moreover, two different functional assays showed that the mutant protein partially retains its kinase activity. Finally, we investigated the in vitro effect of Dexamethasone showing that the drug is able to increase both protein abundance and activity. In conclusion, our results suggest that the c.7157C > A variant is pathogenic, although it causes an atypical phenotype, and that dexamethasone could be therapeutically effective on this and possibly other missense ATM variants.

In vitro dexamethasone treatment does not induce alternative ATM transcripts in cells from Ataxia-Telangiectasia patients

Short term treatment with low doses of glucocorticoid analogues has been shown to ameliorate neurological symptoms in Ataxia–Telangiectasia (A–T), a rare autosomal recessive multisystem disease that mainly affects the cerebellum, immune system, and lungs. Molecular mechanisms underlying this clinical observation are unclear. We aimed at evaluating the effect of dexamethasone on the induction of alternative ATM transcripts (ATMdexa1). We showed that dexamethasone cannot induce an alternative ATM transcript in control and A–T lymphoblasts and primary fibroblasts, or in an ATM-knockout HeLa cell line. We also demonstrated that some of the reported readouts associated with ATMdexa1 are due to cellular artifacts and the direct induction of γH2AX by dexamethasone via DNA-PK. Finally, we suggest caution in interpreting dexamethasone effects in vitro for the results to be translated into a rational use of the drug in A–T patients.

In Ataxia-Telangiectasia, Oral Betamethasone Administration Ameliorates Lymphocytes Functionality through Modulation of the IL-7/IL-7Rα Axis Paralleling the Neurological Behavior: A Comparative Report of Two Cases

Ataxia-Telangiectasia (A-T) is characterized by cerebellar neurodegeneration and immunodeficiency. Recent studies suggest that very low glucocorticoids (GCs) doses may help improve A-T neurological phenotype in some patients. Interestingly, in GCs studies an unexpected improvement of lymphocytes proliferation in some A-T patients has been observed. GCs are able to upregulate IL-7 Rα expression and rescue it from the recycling. In this study, we compared several immunological functions, including PBMC proliferative responses, cell activation events and IL-7/IL-7 Rα axis functionality, with the neurological behavior during an in-vivo GCs treatment between the most Responder patient to GC and the Non-Responder at all. During in-vivo GC treatment, we observed an increase of lymphocyte proliferation upon stimulation with PHA or IL-7 only in the Responder. This finding paralleled the increase in the surface expression of IL-7 R and up-regulation of the CD69 T-cell activation marker. Internalization and recycling of IL-7 R occurred properly only in the Responder. Microarray analysis revealed a remarkable difference in the DE-genes levels among Responder and Non-Responder, mostly concerning miRNAs and Multiple Complex families. Our findings suggest that the improvement of lymphocyte functionality, which correlates to the neurological behavior, is mediated through an effect of GCs on the IL-7/IL-7 Rα axis.

DDIT4 gene expression is switched on by a new HDAC4 function in ataxia telangiectasia

Ataxia telangiectasia (AT) is a rare, severe, and ineluctably progressive multisystemic neurodegenerative disease. Histone deacetylase 4 (HDAC4) nuclear accumulation has been related to neurodegeneration in AT. Since treatment with glucocorticoid analogues has been shown to improve the neurological symptoms that characterize this syndrome, the effects of dexamethasone on HDAC4 were investigated. In this paper, we describe a novel nonepigenetic function of HDAC4 induced by dexamethasone, through which it can directly modulate HIF-1a activity and promote the upregulation of the DDIT4 gene and protein expression. This new HDAC4 transcription regulation mechanism leads to a positive effect on autophagic flux, an AT-compromised biological pathway. This signaling was specifically induced by dexamethasone only in AT cell lines and can contribute in explaining the positive effects of dexamethasone observed in AT-treated patients.

Long-Term Evaluation of Low-Dose Betamethasone for Ataxia Telangiectasia

BACKGROUND

Ataxia telangiectasia is an autosomal recessive disorder characterized by cerebellar ataxia, telangiectases, immune defects, and a predisposition to malignancy. Quality of life is severely impaired by neurological symptoms. However, curative options for the neurological symptoms are limited. Recent studies have demonstrated short-term improvement in neurological symptoms with betamethasone therapy. However, the long-term and adverse effects of betamethasone are unclear. The aim of this study was to evaluate the long-term effects, benefits, and adverse effects of low-dose betamethasone in ataxia telangiectasia.

METHODS

Six patients with ataxia telangiectasia received betamethasone at 0.02 mg/kg/day for two years. After cessation of betamethasone, the patients were observed for two additional years. Neurological assessments were performed, and adverse effects were monitored every three months throughout the four-year study period.

RESULTS

Transient improvement of neurological symptom was observed in five of the six patients. However, after two years betamethasone treatment, only one of the six patients showed a slight improvement in the neurological score, one patient showed no change, and the neurological scores of the remaining four patients deteriorated. After the cessation of betamethasone treatment, neurological symptoms worsened in all patients. As an adverse effect of betamethasone, transient adrenal dysfunction was observed in all cases.

CONCLUSIONS

Although these findings are in agreement with previous studies suggesting that short-term betamethasone treatment transiently benefits patients with ataxia telangiectasia, the long-term benefits and risks should be carefully considered.

Chromosome instability syndromes

Fanconi anaemia (FA), ataxia telangiectasia (A-T), Nijmegen breakage syndrome (NBS) and Bloom syndrome (BS) are clinically distinct, chromosome instability (or breakage) disorders. Each disorder has its own pattern of chromosomal damage, with cells from these patients being hypersensitive to particular genotoxic drugs, indicating that the underlying defect in each case is likely to be different. In addition, each syndrome shows a predisposition to cancer. Study of the molecular and genetic basis of these disorders has revealed mechanisms of recognition and repair of DNA double-strand breaks, DNA interstrand crosslinks and DNA damage during DNA replication. Specialist clinics for each disorder have provided the concentration of expertise needed to tackle their characteristic clinical problems and improve outcomes. Although some treatments of the consequences of a disorder may be possible, for example, haematopoietic stem cell transplantation in FA and NBS, future early intervention to prevent complications of disease will depend on a greater understanding of the roles of the affected DNA repair pathways in development. An important realization has been the predisposition to cancer in carriers of some of these gene mutations.