Full Terms & Conditions of access and use can be found athttp://www.tandfonline.com/action/journalInformation?journalCode=ieod20

Download by: [UQ Library] Date: 11 December 2016, At: 15:06

Expert Opinion on Orphan Drugs

ISSN: (Print) 2167-8707 (Online) Journal homepage: http://www.tandfonline.com/loi/ieod20

Therapeutic targets and investigated treatmentsfor Ataxia-Telangiectasia

Martin F. Lavin, Abrey J. Yeo, Amanda W. Kijas, Ernst Wolvetang, Peter D. Sly,Claire Wainwright & Kate Sinclair

To cite this article: Martin F. Lavin, Abrey J. Yeo, Amanda W. Kijas, Ernst Wolvetang, PeterD. Sly, Claire Wainwright & Kate Sinclair (2016) Therapeutic targets and investigatedtreatments for Ataxia-Telangiectasia, Expert Opinion on Orphan Drugs, 4:12, 1263-1276, DOI:10.1080/21678707.2016.1254618

To link to this article: http://dx.doi.org/10.1080/21678707.2016.1254618

Accepted author version posted online: 04Nov 2016.Published online: 11 Nov 2016.

Submit your article to this journal

Article views: 18

View related articles

View Crossmark data

REVIEW

Therapeutic targets and investigated treatments for Ataxia-TelangiectasiaMartin F. Lavina, Abrey J. Yeoa, Amanda W. Kijasa, Ernst Wolvetangb, Peter D. Slyc,d, Claire Wainwrightc,d

and Kate Sinclaird

aCancer and Neuroscience Department, The University of Queensland, UQ Centre for Clinical Research, Herston, Brisbane, Australia; bAustralianInstitute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, Australia; cChild Health Research Centre, TheUniversity of Queensland, Brisbane, Australia; dLady Cilento Children’s Hospital, South Brisbane, Australia

ABSTRACTIntroduction: Ataxia-Telangiectasia (A-T) is an autosomal recessive multisystem disease affecting thebrain, immune system, lungs, liver and also characterised by an enhanced risk of lymphoid and othertumours. At present there is no cure for A-T with management relying on supportive care usingsymptom-specific medications. Identification of the gene defective in this syndrome, ATM, and furthercharacterization of the disorder together with greater insight into the function of the ATM protein hasprovided greater opportunity for the development of potential therapies.Areas covered: Here we review conventional as well as more recently developed approaches tomanage the symptoms of patients with A-T. In addition we explore ongoing and potential strategiesfor therapy involving gene correction, stem cells and use of antioxidants and anti-inflammatory agents.Expert opinion: Prevention or arrest of the progressive neurodegeneration, the most debilitatingfeature of A-T, represents a major goal in the development of a cure for this disorder. However, sincelung disease and increased risk of cancer are responsible for the majority of mortality in A-T, a greaterunderstanding of these pathologies together with more effective approaches to treatment is requiredin the overall management of patients.

ARTICLE HISTORYReceived 19 August 2016Accepted 26 October 2016

KEYWORDSAtaxia-telangiectasia; ATMprotein; neurodegeneration;lung disease; liver disease;clinical trials; oxidativestress; steroids

1. Introduction

1.1. Clinical presentation and pathology

Ataxia-telangiectasia (A-T) is a rare, autosomal recessive dis-ease caused by mutations in the ataxia-telangiectasia mutated(ATM) gene [1]. The ATM protein is a serine/threonine kinasethat plays a major role in sensing of DNA double-strand breaks(DSB). It phosphorylates several key repair proteins that initi-ates arrest at cell cycle checkpoints, DNA damage repair and/or apoptosis. A-T was first described as a distinct clinical entity,assisted by autopsies, reported organ developmental abnorm-alities, neurological manifestations and a third major charac-teristic of disease, recurrent sinopulmonary infection [2,3]. SeeFigure 1 for major characteristics.

1.1.1. NeurodegenerationA-T is characterized by its neurological symptomatology withataxia, the major presenting symptom in this syndrome, evidentwhen the child begins to walk toward the end of the first year oflife, exhibiting ataxic gait and truncal movements [4]. Ataxia isprogressive, spreading to affect the extremities and then speech.Involuntary movements become evident eventually, and by theend of the first decade of life the child usually requires a wheel-chair but milder forms of the disease have been described wheresymptoms develop more slowly [5]. These involuntary move-ments include twitching and jerking of the hands and feet(chorea), slower twisting movements of the upper body

(athetosis), adoption of stiff and twisted postures (dystonia),occasional uncontrolled jerks (myoclonic jerks), and variousrhythmic and nonrhythmic movements with attempts at coordi-nated action (tremors). Cortical cerebellar degeneration in A-Tinvolves primarily Purkinje and granule cells, but while degen-erative changes in the central nervous system (CNS) are seenpredominantly in the cerebellum, changes have also beendescribed in the dentate and olivary nuclei, the spinal cord andspinal ganglia, the cerebrum, the basal ganglia and the brainstem [6]. The latter changes are usually seen in older patients.

Telangiectasia is the second major clinical manifestation of thedisease with a later onset than ataxia, occurring between 2 and8 years of age [4]. This is due to dilation of blood vessels, primarilyin the ocular sclerae, and often gives the impression of ‘bloodshot’eyes. These are not confined to the eyes butmay also appear in thebutterfly regions of the face, ears and on the popliteal region.

1.1.2. ImmunodeficiencyA-T is a highly variable primary immunodeficiency, involving bothcellular and humoral immunity [7,8]. In the latter case, a reductionin IgA, IgG and IgE levels as well as abnormalities in IgM and IgGsubclasses iswidely observed. The infection history is variable,withsome having chronic sinopulmonary infections, others haverepeated infections and some having no more infections thantheir unaffected siblings [7]. Infections include otitis and sinusitisas well as bronchitis and recurrent pneumonia [9,10]. Patients withA-T are susceptible to common bacterial pathogens and viruses

CONTACT Martin F. Lavin m.lavin@uq.edu.au The University of Queensland, UQ Centre for Clinical Research (UQCCR), Royal Brisbane & Women’s HospitalCampus, QLD 4029, Australia

EXPERT OPINION ON ORPHAN DRUGS, 2016VOL. 4, NO. 12, 1263–1276http://dx.doi.org/10.1080/21678707.2016.1254618

© 2016 Informa UK Limited, trading as Taylor & Francis Group

but rarely to opportunistic infections, as observed in other primaryimmunodeficiencies. There appears to be no direct correlationbetween the severity and frequency of infections and the degreeof immunodeficiency. Faulty development of the thymus is alsocharacteristic of A-T and frequently this organ cannot be identifiedat autopsy [4]. More recently, evidence has been provided for aninflammatory phenotype in A-T [11] which has been linked to adefect in the innate immune response [12,13]. Thismay explain thefailure to observe a correlation between frequency of infection andB and T cell immunity. Recurrent upper and lower respiratory tractinfections may progress to bronchiectasis and interstitial lungdisease characterized by fibrosis and chronic inflammation [9,10].Respiratory disease causes significant morbidity and mortality inpatients with A-T, with up to 40% of deaths due to lung complica-tions [14,15].

1.1.3. Cancer predispositionThe second most common cause of death in patients with A-T iscancer with a lifetime prevalence of 30% which is approximately100-fold greater than expected for an age-matched population[16]. The breakdown of cancers observed are 40% non-Hodgkin’slymphomas, 25% leukemias, 25% assorted solid tumors and 10%Hodgkin’s lymphomas [17]. Most leukemias and lymphomas areof T-cell origin [18] a pattern that is similar to that observed inAtm knockout mice [19,20] but is distinct from the B-cell pre-dominance of lymphoreticular malignancies in children without

A-T. A number of solid tumors have also been found in patientswith A-T including adenocarcinomas, gonadoblastomas andmedulloblastomas [21]. There is also an increased risk of canceramongst A-T heterozygotes, particularly breast cancer pointingto some penetrance of the defective gene [22].

1.1.4. Lung diseaseRecurrent infection, immune deficiency, aspiration and impairedclearance of respiratory tract secretions combine to increase sus-ceptibility to lung disease in A-T [14,15]. Recurrent infections are amajor clinical feature of A-T with up to 80% of patients beingaffected [9]. These include both upper and lower respiratory tractinfections associated with the development of bronchiectasis orpersistent pleural abnormalities [10,23]. A second major form oflung disease, interstitial lung disease or pulmonary fibrosis devel-ops later in life and treatment with antibiotics only partiallyresolved the infections whereas treatment with corticosteroidsled to patient improvement. Progressive neurological declinemay also contribute to lung disease in patients through muscleimpairment which in turn may affect swallowing and lead toaspiration [14]. It is clear that immunodeficiency involving bothhumoral and cell-mediated immunitymakes a significant contribu-tion to susceptibility to infection and the resulting lung disease.The recent observation of a defect in innate immunity in A-T cellsand in Atm-deficient mice is compatible with pro-inflammatorychanges which would be expected to respond to steroid therapyas described [12].

1.1.5. Liver diseaseAlpha-fetoprotein (AFP) represents a useful biomarker to supportthe diagnosis of A-T since this protein remains elevated in theserumofmost patients [24]. It remains unclearwhyAFP is elevatedin patientswithA-T, however, a report by Jung et al. [25] suggestedthat a small alternatively spliced product from the AT motif-binding factor 1 (ATBF1) gene, that interacts with an AT-rich ele-ment located upstream of AFP promoter to suppress transcriptionof this gene, is defective in its translocation to the nucleus in A-Tcells. There is also evidence of increased liver transaminases in theserumofpatientswithA-Twhichmight point to subclinical chronicliver involvement in A-T. Hepatic dysfunction was first described infive patients with A-T in 1970 as indicated by bromsulphthaleinretention and serum enzyme elevations [26]. Hepatic insufficiency

Figure 1. Clinical features of ataxia-telangiectasia.

Article highlights

● There is no cure for ataxia-telangiectasia but supportive care isavailable to treat specific symptoms

● Ataxia-telangiectasia is a multisystem disease affecting the brain,immune system, lungs and liver

● There is increasing evidence for involvement of oxidative stress inthis disorder

● Progress to date using clinical trials suggest that prophylactic anti-biotics and combinations of anti-oxidants and anti-inflammatorydrugs may be beneficial in slowing the progress of the disorder

● Potential therapies include the use of stem cells and readthroughcompounds

This box summarizes key points contained in the article.

1264 M. F. LAVIN ET AL.

was subsequently described in patients with histological evidenceof veno-occlusive disease and cirrhosis [27,28].More recently in thecase of a 22-year-old patient with A-T, with a 3 year history ofhyperlipidemia and liver test alterations, histological examinationof a liver biopsy revealed characteristic features of nonalcoholicsteatohepatitis with moderate macrovesicular and multivesicularsteatosis, ballooning hepatocytes and fibrosis [29]. They attributedthepathogenic changes in the liver to longer survival andoxidativestress. A recent investigation of hepatic involvement in a largecohort of patients with A-T (n = 53, mean age 14.6 ± 5.2 years)revealed abnormal liver enzyme levels in 43.4% (age9.98 ± 5.1 years) of patients [30]. Fatty liver was detected in 39%[10] of these by ultrasonography and liver biopsy revealedmild-to-moderate steatosis in two patients and fibrosis in one of these. Theauthors recommended screening for fatty liver in all patients withA-T. Deficiency in ATM is also associated with hyperlipidemia,metabolic syndrome and mitochondrial dysfunction [31].

1.1.6. DiabetesSchlack et al. [26] first described an unusual form of diabetes infive of eight patients with A-T characterized by marked hyper-glycemia, resistance to ketosis, no glycosuria and elevatedplasma insulin levels after glucose administration. The bloodglucose response to insulin was decreased suggesting insulinresistance. It is of interest that all five patients also had hepaticdisease. It was subsequently shown that monocytes from twopatients consistently demonstrated an approximately 80%decrease in insulin receptor affinity which could account for theinsulin resistance [32]. This relationship was further substantiatedwhen Yang and Kastan [33] demonstrated a role for ATM in aninsulin-signaling pathway that controls initiation of protein trans-lation. They followed this up providing evidence that ATM-dependent stress pathways mediate susceptibility to the meta-bolic syndrome and that chloroquine or related agents promot-ing ATM activity could modulate insulin resistance and decreasevascular disease [34]. Takagi et al. [35] found that Atm−/- micewere insulin resistant and possessed less subcutaneous adipose

tissue as well as a lower level of serum adiponectin than Atm+/+

mice. Furthermore, in vitro studies revealed impaired adipocytedifferentiation in Atm−/- cells caused by the lack of induction of C/EBPα and PPARγ, crucial transcription factors involved in adipo-cyte differentiation. Interestingly, ATM was activated by stimulithat induced differentiation, and the binding of ATM to C/EBPβand p300 was involved in the transcriptional regulation of C/EBPα and adipocyte differentiation.

1.2. Laboratory characteristics of A-T

Prior to the cloning of the ATM gene a patient presenting withataxia and suspected of having A-T would undergo a serumalpha-fetoprotein determination which is elevated in ~95% ofpatients [24]. Other abnormalities include absence of or markedreduction of IgA, IgG2 and IgE as well as elevated levels of IgMmonomer and lymphopenia [7]. Deficiencies in antibody produc-tionwhich is variable in this syndrome have been associatedwithintrinsic defects in B lymphocytes primarily class switching [36].This is also observed in Atm-deficient mice [37]. Depression ofT-cell function, spontaneous cytogenetic abnormalities, includ-ing chromatid gaps, chromosomal breaks, translocations, rear-rangements and inversions are observed in lymphocytes fromthe majority of patients [38–40]. Chromosomal translocationshave long been reported to occur predominantly in the T cellreceptor (TCR) loci and the immunoglobulin heavy chain gene(IGH) locus [41]. High rates of spontaneous intrachromosomalrecombination (~30–200 times increase) have also been reported[42]. Increased chromosomal breakage postirradiation is alsocharacteristic of A-T cells [43]. Reduced cell survival postirradia-tion is also a laboratory hallmark of patients’ cells and radio-sensitivity has been widely used as a screening tool for A-T wellbefore the gene was discovered. It is also of note that hypersen-sitivity to radiation was observed in patients exposed to radio-therapy for lymphoid malignancy well before the cellularsensitivity was reported [44–46]. A complete list of the laboratorycharacteristics and abnormalities in A-T cells appears in Figure 2.

Figure 2. Laboratory characteristics observed in A-T.

EXPERT OPINION ON ORPHAN DRUGS 1265

1.2.1. Identification of the ATM protein and diagnosisMapping of the A-T locus [47] and subsequent identification ofthe gene mutated in A-T [1] provided the opportunity formore rapid diagnosis of this disorder. The ATM protein is amember of the phosphatidylinositol 3-kinase like-kinase (PIKK)family of proteins capable of phosphorylating a multitude ofcellular proteins in response to DNA DSB [48,49]. These pro-teins function in cell cycle checkpoint control, DNA repair,apoptosis, transcriptional control and regulation of other cel-lular processes [50]. In short this protein functions to maintainthe integrity of the genome and minimize the risk of cancer,lung disease and neurodegeneration that characterizes thisdisease [51,52]. ATM is predominantly present in the nucleuswhich fits with its role in maintaining genome stability.However, it has been shown that ATM is also present in thecytoplasm where it is associated with peroxisomes [53,54], andmitochondria [55]. Cytoplasmic localization of ATM is in keep-ing with the observation that this protein is also activated inresponse to oxidative stress by a mechanism not dependenton DNA damage [56]. Since both peroxisomes and mitochon-dria produce excess reactive oxygen species (ROS) whenunder stress, association of ATM with these organelles wouldrepresent a ‘front line of defense’ against potential oxidativedamage. In the case of peroxisomes ATM bind to the peroxi-some receptor PEX5 where it becomes activated in responseto oxidative stress to induce pexophagy a process required forperoxisome hemostasis [54]. A fraction of ATM protein is alsolocalized to mitochondria and mitochondrial damage (ele-vated mROS) can directly activate ATM in the absence ofDNA damage [55,57]. As in the case of peroxisomes it appearslikely that ATM also plays a role in mitochondrial homeostasissince mitophagy is defective in cells lacking ATM.

As indicated above the majority of ATM mutations arecompound heterozygote and are largely indels, missense orsplice site mutations resulting in premature stop codons giv-ing rise to unstable ATM protein [58]. The great majority ofpatients with A-T are defined by lack of ATM protein or lowlevels of missense mutated protein but the ATM protein kinaseactivity is always lacking in patients. Of interest it has beenfound that some of the missense mutations for which a lowlevel of ATM protein is detectable, results in a milder form ofthe disease [59,60]. Thus the absence of ATM protein and/orlack of ATM protein kinase activity represent a solid laboratoryassay in conjunction with ATM gene mutation analysis andclinical diagnosis of A-T.

2. Treating different aspects of the defect

2.1. Clinical trials

Information on clinical trials for a wide range of diseases canbe found under https://clinicaltrials.gov/. While there are manytrials described for hereditary cerebellar ataxias such as theuse of riluzole to improve Scale for the assessment and Ratingof Ataxia (SARA) scores [61] the focus here will be on A-T. Atpresent there are 15 trials listed under A-T as either com-pleted, recruiting, not yet recruiting, enrolled by invitation orunknown (Table 1). Other trials reported in the literature arealso referred to.

2.2. Respiratory tract infections

Recurrent respiratory tract infections affect the majority ofpatients with A-T, becoming more prevalent with age [9,23].Microbiological evaluation of respiratory secretions frompatients with A-T identified Pseudomonas aeruginosa,Haemophilus influenza, Streptococcus pneumoniae andStaphylococcus aureus as the most common bacterial patho-gens [9,10]. Opportunistic infections are uncommon in A-Tunlike that in other immunodeficiency disorders [66], ratherthe pattern of infection resembles that observed in patientswith cystic fibrosis [9]. Infections with viral pathogens such asrespiratory syncytial virus and Epstein–Barr virus have alsobeen reported. As in other disorders, frequent infectionsaccompanied by hypogamma-globulinemia with antibodydeficiency can be treated with immune globulin replacementtherapy. Airway clearance strategies are used along with anti-biotic therapies and some groups have also instituted azithro-mycin to reduce the frequency of exacerbations of underlyingbronchiectasis although there are no trials to date that haveexamined the evidence for these approaches. Patient manage-ment is best overseen in a specialist multidisciplinary clinic.There is also evidence that pneumococcal conjugate antigenmay offer some protection.

2.3. Lung structure and function

Children with A-T often present in the first few years of life withrecurrent respiratory infections and suppurative lung diseasebut assessment of this is limited by the inability of children tocope with conventional lung function tests [67,68]. Patientshave increased sensitivity to ionizing radiation and repeatedX-rays or computed tomography scans are not acceptable. Inaddition, with progression of the neurological disease coordina-tion and respiratory function testing become more challenging.Magnetic Resonance Imaging (MRI) has generated interest as itdoes not involve ionizing radiation. MRI also enables functionalimaging (particularly pulmonary perfusion), which is importantas dilation of bronchial arteries. The reversibility of perfusiondefects after therapeutic intervention could be a method todifferentiate regions with reversible and irreversible disease.The application of current MRI sequences is limited due to thelow proton density of lung tissue; difficulty in differentiatingbetween bronchial wall thickening and bronchiectasis and theoccurrence of susceptibility artifacts in air–tissue interfaces.Standard MRI sequences are not currently able to identifytrapped air, emphysema or increased lung volume. Restrictedspatial resolution, increased set up and acquisition time andhigher cost have also been reported as challenges. Since meth-ods for assessing pulmonary function are unreliable in A-T, it isnecessary to develop tests that will accurately determine lungfunction to aid intervention and initiate treatment. A sensitivetechnique for measuring respiratory function during tidalbreathing that does not require any complex respiratory man-euvres has been described recently. This technique, known asT-FOT is a variation of the conventional forced oscillation tech-nique (FOT) that is highly sensitive and specific for detectingairway obstruction [69]. The lung disease in A-T is likely to bepatchy and involve airway obstruction/infection that can be

1266 M. F. LAVIN ET AL.

detected by T-FOT. The outcome of a forced Spirometry man-euvres longitudinal study with patients with A-T conducted atthe Sheba Medical Center, Israel remains unreported. Lungimaging by computed tomography (CT) is limited by anincreased sensitivity to ionizing radiation, making repeatedX-rays or CT scans unacceptable. Patients with recurrent lowerrespiratory tract infections should be assessed for dysfunctionalswallowing and aspiration (preferably without undue exposureto diagnostic X-rays). These defects are associated with pulmon-ary symptoms, which are exacerbated by poor mucociliaryfunction, defective inspiration and weak cough. Treatment fordysfunctional swallowing and aspiration includes the addition

of thickeners to thin liquids and the placement of a gastroscopytube to facilitate feeding in severe cases of malnutrition.Sinopulmonary infections usually respond well to antibio-tics [17].

In addition to antibiotic administration and immunoglobu-lin replacement, respiratory therapy can be employed toreduce the development of bronchiectasis and interstitiallung disease. Since maximum inspiratory and expiratory pres-sures are good markers of respiratory muscle strength, espe-cially in patients with A-T, they have been employed inpatients to improve quality of life. Inspiratory muscle traininghas been shown to improve ventilatory pattern, lung volume

Table 1. Ataxia-telangiectasia clinical trials.

Name of trial Sponsor ID No. Study start dateEstimatedcompletion

Patientsenrolled Outcome or expected outcome

Susceptibility to Infections in AtaxiaTelangiectasia

Johann WolfgangGoethe UniversityHospital

NCT02345135 September 2012 January 2016 41 Last update: January 2015

Body Composition and HormonalStatus in Ataxia Telangiectasia

Johann WolfgangGoethe UniversityHospital

NCT02345200 April 2013 April 2014 52 See Pommerening et al. [62]

Conjugate Pneumococcal Vaccine inAtaxia Telangiectasia (AT)

Institute of ChildHealth, GreatOrmond StHospital

NCT00656409 June 2006 March 2008 30 Immunogenicity of vaccine andadverse outcomes

Response of Individuals WithAtaxia-Telangiectasia toMetformin and Pioglitazone(RAMP)

NHS Tayside andUniversity ofDundee

NCT02733679 June 2016 February 2018 30 Change in insulin sensitivity aftertaking metformin in A-T comparedto controls

Status of Growth Hormone/Insulin-like Growth Factor-1 (GH/IGF-1)Axis and Growth Failure in AtaxiaTelangiectasia (AT) (GHAT)

Johann WolfgangGoethe UniversityHospital

NCT01052623 January 2010 September 2012 23 To evaluate the GH increase afterarginine provocation test. See Vosset. al. [63]

Immunogenicity of PneumococcalVaccines in Ataxia-telangiectasiaPatients

Sheba MedicalCentre, Tel Aviv

NCT01075438 March 2010 February 2011 20 Primary end point will be levels ofantibodies against 13 serotypes ofStreptococcus pneumoniae.Outcome unclear

Oxidative Stress, Low GradeInflammation, Tissue Breakdownand Biomarkers in CerebrospinalFluid of A-T

Johann WolfgangGoethe UniversityHospital

NCT02285348 April 2013 May 2015 40 Alterations in protein expressionrelated to A-T using proteomicstudies. See Dzieciatkowska Met al. [64]

Cell-Based Approaches for Modelingand Treating Ataxia-Telangiectasia

Sidney KimmelComprehensiveCancer Centre,Johns HopkinsUniversity

NCT02246491 September 2014 September 2018 20 Fibroblasts from patients with A-Twill be collected forreprogramming and iPSC analysisin the laboratory but not fortherapy

Study for Treatment of Cancer inChildren with Ataxia-telangiectasia

St. Jude Children’sResearch Hospital

NCT00187057 September 2002 June 2013 6 To determine the feasibility ofdelivering modified intensivechemotherapy to children with A-Twho present with cancer. SeeSandlund JT et al. [65]

Baclofen Treatment of AtaxiaTelangiectasia to checkusefulness for treatingneurological problems

Johns HopkinsUniversity

NCT00640003 April 2007 February 2011 12 Improvement in the decay constantfor velocity storage as assessed byquantitative video examination ofeye movement during and afterrotation. Outcome unclear

The Validity of Forced ExpiratoryManoeuvres in AtaxiaTelangiectasia StudiedLongitudinally

Sheba MedicalCentre

NCT00951886 July 2009 July 2009 28 Determining ability to performspirometry. Outcome not clear

EDS in Ataxia TelangiectasiaPatients (ATTeST)

Erydel NCT02770807 June 2016 December 2018 180 Steroid infusion trial underway.Change from baseline analyzedusing a Mixed Model RepeatedMeasures (MMRM) approach

Amantadine for ImprovingNeurological Symptoms inAtaxia-Telangiectasia

Sheba MedicalCentre

NCT00950196 November 2008 November 2009 30 Improvement in ataxia

EXPERT OPINION ON ORPHAN DRUGS 1267

and respiratory muscle strength in patients and has the poten-tial to act as an adjuvant to drug treatment [70].

2.4. Neurological defects

A-T is primarily a syndrome of progressive cerebellar ataxia butmore diffuse changes to the CNS are also evident. Microcephaly isusually not observed in A-T unlike that in Nijmegen breakagesyndrome (NBS) and Rad50-deficient patients [71,72], althoughone report described a small head circumference in 60% ofpatients in a retrospective study of 57 patients [73]. Cerebellardegeneration in A-Tmanifests as dystrophic changes involving thedendrites and axons of Purkinje cells and ectopic Purkinje cells areevident [4]. Of all the features of A-T, the progressive cerebellarneurodegeneration is the most debilitating. By the end of the firstdecade, ataxia has progressed to the extent that the child isconfined to a wheelchair and may have poor control of headand torso [17]. This progresses to include peripheral neuropathyand eventually to spinal muscular atrophy [6]. Neurological out-come measures have relied in the past on the more general toolsfor assessing ataxia, SARA and International Cooperative AtaxiaRating Scale (ICARS) More recently two scoring systems, designedto capture the special features of A-T, have been developed for theassessment of neurological features in A-T patients, the A-T Indexor Crawford Score that consists of a 39 point scale derived from 10separate parameters [74], and the A-T neurological ExaminationScale Toolkit (A-T Nest). The A-T Nest is more comprehensive with53 neurological parameters and also includes a communicationdomain [75]. While a good correlation was obtained betweenthese two systems performed on the same day the A-T Nestmay prove to be more discriminatory in the more comprehensiveset of parameters tested. Thus, any effective treatment for A-Twould ideally involve prevention or at least slowing of the pro-gressive neurodegeneration and an ability to increase the latencyperiod or markedly reduce the risk of lymphoid malignancies.

2.5. Dystrophy and nutritional studies

Failure to thrive has been reported in several studies with A-Tpatients [76,77]. Low body mass index (BMI) is also observed in50–80% of patients which may be explained by dysphagia, aspira-tion or lung disease [78]. Patients exhibiting aspiration were olderand had lower body weight for height z-scores (WHZ) and pre-mature death appeared to be the result of secondary complica-tions of the disorder. Pronounced deficiency of the GH/IGF-1 axisaccompanied by markedly reduced body weight and high ataxiascores has also been reported for patients [79], pointing to a rolefor IGF-1 and nutritional status in neuroprotection.

A recent assessment of the nutritional status in Australianpatients with A-T showed that they were vulnerable to issuesthat influenced their nutritional status [80]. Almost 80% hadshort stature and 50% were underweight with evidence ofsignificant malnutrition in approximately 70% of patients.Poor food intake and diet quality suggested the need forearly intervention. This would require ongoing support forfamilies and discussions on the introduction of gastrostomytube feeding. High rates of malnutrition and reduced leanbody mass were also reported elsewhere [81,82].

2.6. Bone marrow transplantation

A-T is characterized by immunodeficiency and an increasedrisk of developing leukemias and lymphomas [83]. Thus thesepatients would be expected to benefit from bone marrowtransplantation to treat the hematopoietic phenotype espe-cially since there is no current cure for the disorder and up to30% of patients die from malignancy. However, ethical issuesexist since patients are hypersensitive to agents using anablative therapy such as ionizing radiation and alkylatingagents. Replacement of the bone marrow compartment inAtm−/- mice with clinically relevant nonmyeloablative host-conditioning regimes (anti-CD4, anti-CD8 antibodies) over-came the immune deficiency and prevented the developmentof malignancy in these mice [84]. However, treatment withcyclophosphamide was also necessary for engraftment whichmight be predicted to have increased toxicity in patients. Notsurprisingly very few A-T patients have had this form of treat-ment given the associated risks. Ghosh et al. [85] reported thefirst BMT for an A-T patient presenting with Hyper IgM while afull lympho-hematopoietic reconstitution was observed thepatient died of encephalopathy and liver failure 8 monthslater. There is only one report of long-term survival of a3 year old A-T child with T-ALL that received allogeneic-matched sibling donor peripheral blood stem cells [86]. Tominimize toxicity a modified form of the German regimeused in Fanconi anemia (GEFA02) was employed which lackedmyeloablative properties. Cyclophosphamide was not used.More recently, an A-T patient with immunodeficiency andrecurrent EBV-associated lymphoproliferation was cured bychemotherapy followed by allogeneic-matched sibling stemcell transplantation [87]. In this case also, a conditioningregime based on the Fanconi anemia protocol GFFA-02 wasused. This patient developed severe mucosal toxicity duringthe early transplant course as well as veno-occlusive diseaseand respiratory distress syndrome all of which responded tomanagement. After experiencing deteriorating ataxia he isnow able to sit and stand without support and can walkwith assistance. It is evident from these studies that A-Tpatients are particularly susceptible to toxicity after exposureto chemotherapy and ablative conditioning prior to transplan-tation. Removing cyclophosphamide from the conditioningregime may have benefit but its reduction in the treatmentof lymphoid malignancies is not recommended [88]. Recentadvances in the generation of pluripotent stem cells from A-Tpatients also offers the possibility of patient-specific cell trans-plantation [89,90].

2.7. Therapy for malignancy in children with A-T

Up to 30% of children with A-T are diagnosed with malignancyduring their lifetime [91]. The tumors involved tend to beprimarily lymphomas and leukemias but with better manage-ment patients are living longer and developing a spectrum ofsolid tumors [92]. Prior to understanding the sensitivity toradiation and agents used in chemotherapy, patients withA-T showed severe adverse reactions to treatment [44].Accordingly, reduced intensity therapy has been employedto reduce the risk of adverse effects. Seidemann et al. [93]

1268 M. F. LAVIN ET AL.

treated patients with A-T for non-Hodgkin’s lymphoma(B-NHL) and showed that curative treatment was possiblewith intensity of therapy adjusted to individual risk factorsand tolerance. They suggested omission of alkylating agentsand epipodophyllotoxins and limitation of methotrexate dose.At the time of the report 5/9 patients with either A-T or NBSwere in continuous complete remission (CCR). In a later studyon 19 patients with A-T with malignancy where 10 werediagnosed with B-NHL, it was evident that dose reductionattenuated the toxicity side effects of chemotherapy such asmucosal inflammation and infectious complications [94].Earlier reports showed poor results on the treatment of A-Tpatients for lymphoid malignancies [88,95]. The former studydemonstrated that patients treated with standard chemother-apy doses had a significantly better median survival thanthose treated with reduced dose. However, Bienemann et al.[94] revealed long-term survival in >50% of patients and atleast intermittent cure for second malignancies. The study alsodemonstrated that there was no disadvantage for diseasecontrol for patients in whom chemotherapy was significantlyreduced.

More recently a curative intent approach was employed foradvanced stage high grade mature B-cell malignancies in fivechildren with A-T [65]. They used a modified form of the SFOPLMB-89 regime for B-cell lymphoma described previously [96].This modification was made taking into account the uniquetoxicity profile observed in A-T patients receiving chemother-apy (see Table 1 [65]). Sustained CCR was observed in twopatients, one patient had CCR at 6 years and a second patientmaintained CCR for 3 years prior to symptoms as imbalance-dying from pulmonary complications. Two patients died fromtoxicity during induction and the other failed inductionbecause of progressive disease. Clearly reduction of che-motherapeutic dose is not in itself sufficient to obtain optimaloutcome for patients with A-T being treated for malignancy.Sandlund et al. [93] suggest the introduction of novel targetedtherapeutic agents such as monoclonal antibodies or smallmolecule inhibitors within the less intensive chemotherapeu-tic approach. Other issues include drug resistance in somepatients and a greater understanding of the biology of thetumors.

3. Treatment for the neurological defects

Modest improvements can sometimes be achieved by treatingthe associated neurological symptoms of A-T. Basal gangliadysfunction may respond to L-DOPA derivatives, dopamineagonists and, occasionally, to anticholinergics. The latter mayalso reduce drooling. The loss of balance may respond toamantadine (a tricyclic amine that releases dopamine andother monoamines at central synapses) [97], fluoxetine (selec-tive inhibitor of serotonin re-uptake) or buspiron (serotonin5-HT1A receptor partial agonist with moderate affinity forbrain dopamine D2 receptors [98]. A second 5-HT1A receptoragonist has also been shown to be successful in treatingpatients with other forms of spinocerebellar ataxia [99]. Amore comprehensive list of pharmacotherapeutic interven-tions for neurological disease symptoms of A-T appear in anexcellent review by Hoche et al. [100].They address such

symptoms as imbalance, motor incoordination, dysarthria, tre-mor, nystagmus, choria, dystonia, drooling, spasticity and per-ipheral neuropathy and the drugs used to treat thesesymptoms. Cerebellar tremors may also be treated with pro-pranolol (a beta-adrenergic blocking agent), gabapentine (aGABA analogue) or clonazepam (a benzodiazepine). Some ofthese agents may also improve speech and coordination.Furthermore, although deficiencies of thiamine, vitamin Band vitamin E can cause ataxia, multivitamin supplements donot correct the ataxia of patients with A-T [17].

3.1. Betamethasone

There is evidence from several studies that steroids produceshort-term improvement in A-T. Amelioration of neurologicalsigns, assessed by SARA, has been reported after short-termtreatment with oral betamethasone [101,102]. In a follow-upstudy using significantly lower doses of betamethasone (0.03and 0.01 mg/kg/day) with six patients responsive to beta-methasone, SARA scores significantly improved in all patientsat the higher dose and some improvement was also observedat the lower dose [103]. These authors suggest that antioxida-tive mechanisms may be at play in improving cerebellar func-tions in A-T [102]. In a separate randomized trial of 13 patientswith A-T, betamethasone reduced ICARS total score signifi-cantly (~30%) in both intent-to-treat (all patients randomized)and in per-protocol patients [104]. Unfortunately, long-termcomplications of steroid use far outweigh the short-term ben-efits of this treatment.

3.2. Intra-erythrocyte dexamethasone delivery

The EryDex System (EDS) permits the encapsulation of dexa-methasone sodium phosphate to autologous erythrocytesderived from a 50 ml blood sample, processed ex vivo withhypotonic saline which permits osmotic opening of the erythro-cyte (RBC) pores and diffusion of dexamethasone phosphate intothe cells (www.erydel.com/). EDS was developed by EryDel(Urbino, Italy). Chessa et al. [105] employed EDS in single-arm,open-label,6 month extended phase II trial where patientsreceived a monthly treatment of 50 ml of autologous red bloodcells (RBC) loaded with 2 vials of 250 mg of dexamethasonesodium phosphate. In this study which enrolled 22 patients (18completed), after six infusions, a mean reduction of 5 points inICARS was reported. In an extension of this study for an addi-tional 24 months, patients experienced a continuous neurologicimprovement with respect to pretreatment status whereas con-trols showed a progressive neurologic deterioration after discon-tinuation of the treatment [106]. Evidence has been provided forthe mechanism involved by the induction of a noncanonicalsplicing event which generated a miniATM variant with partialrestoration of ATM activity. More recently, dexamethasone hasbeen shown to increase the production of the antioxidants, GSHand NADPH, which improved the antioxidant capacity of A-Tcells to counteract oxidative stress [107]. This can be explainedby the promotion of nuclear accumulation of the transcriptionfactor NRF2 which drives expression of antioxidant pathways. Insummary, EDS proved to be safe and well-tolerated and none ofthe side effects associated with chronic administration of steroid

EXPERT OPINION ON ORPHAN DRUGS 1269

were observed. Based on the success of the initial trial with EDS,an international, noninterventional observational study was per-formed in 6 centers specialized in treating pediatric ataxiapatience. This study indicates that the ICARS and the CGI-S canbe used as measures of severity in patients with A-T 6 years ofage and older [108]. EryDel is also in the process of recruitingpatients with A-T for an international, multicentre, 1-year, rando-mized, prospective, double-blind, placebo-controlled, phase IIIstudy which will assess the effect of two nonoverlapping doseranges of EDS-EP, administered by IV infusion once per month,with assessment of neurological symptoms of enrolled patientswith A-T (NCT02770807). Criteria for inclusion include meetingclinical criteria for diagnosis of A-T; 6 years and older of either sex;in autonomous gait or assistance by periodic use of support andhaving a body weight >15 kg.

3.3. Treatment with amantadine sulfate

Nissenkorn et al. [109] treated 17 children over 8 weeks with thedopaminergic and anti-IV-methyl-d-aspartate (NMDA) agentamantadine sulfate assessing ataxia using the InternationalCooperative Ataxia Scale, Parkinsonism by the Unified ParkinsonDisease Rating Scale and chorea/myoclonus by the AbnormalMovement Scale. Overall, 76.5% of patients responded with amean improvement of approximately 30%. The drug was welltolerated with mild and transient side effects that did not requirediscontinuation of the trial. Amantadine increases dopaminergictransmission by inhibiting synaptic uptake of the neurotransmit-ter. A larger follow-up study is required to further test the efficacyof the use of amantadine.

4. Treatment for oxidative stress

4.1. Oxidative stress and biomarkers in cerebrospinalfluid

Since it is neither safe nor ethical to surgically biopsy braintissue from patients with A-T, cerebrospinal fluid (CSF), whichis directly in contact with brain tissue, is relatively easy tosample safely by lumbar puncture. The aim by Zielen et al.,at the Johann Wolfgang Goethe University Hospital is toinvestigate oxidative stress, low grade inflammation and tissuebreakdown in the brains of patients with A-T by analyzing CSF.Alterations in protein expression related to A-T will be quanti-fied by liquid chromatography/mass spectrometry (LC/MS)-based proteomic analysis of CSF from healthy individualsand patients with A-T to determine candidate proteins (newbiomarkers) which might be used as surrogate markers ofdisease progression (NCT02285348).

4.2. Oxidative stress clinical trial

This was conducted by Dr Howard Lederman, John’s HopkinsHospital, to test safety and identify markers for treatment ofpatients with a combination of nicotinamide and the antiox-idant α-lipoic acid to investigate effect on progress of neuro-degeneration. Two laboratory markers of oxidative stresssignificantly improved when participants took both α-lipoicacid and nicotinamide. A trend toward increased lymphocyte

counts was also observed, but did not reach statistical signifi-cance. They suggest that these findings will form the basis forexamination of other laboratory markers of oxidative stress infuture trials of novel antioxidant treatments.

4.3. Use of myoinositol on neurological and immunefunction

Dr. Gerald Berry (Philadelphia) conducted the first A-T clinicalstudy to investigate the effects of myoinositol on neurologicaland immune functions. They referred to promising changes incertain immune cells in some A-T children (www.treatAT.org).While the study was described as revealing valuable informa-tion about the progression of A-T in the brain, the study sizewas not large enough to have statistical power to draw con-clusions about the efficacy of this approach [110].

5. Potential new therapies

In addition to the therapeutic approaches described aboveextensive research into A-T, since the ATM gene was identi-fied, has provided several potential approaches for treatment.

5.1. Use of stem cells

Stem cells play a key role not only in development and growthof organisms but also in building new tissues and replacingothers after injury. Thus they have great potential in regen-erative medicine for the development of new therapies in avariety of different disease types. Clearly A-T is a good candi-date since different tissues are involved and it would be verybeneficial to be able to correct the decline in neurologicalfunction with patient-specific stem cells. Reports on the regen-eration of pluripotent stem cells (iPSC) from different cell types(e.g. skin fibroblasts and blood mononuclear cells) have eli-cited considerable interest since they can be produced fromchildren/adults and avoid ethical considerations associatedwith use of human embryos. We employed fibroblasts frompatients with A-T to reprogram into bona fide A-T inducedpluripotent stem cells (A-T iPSCs) [90]. We showed that A-TiPSCs recapitulate key features of the A-T cellular phenotype,including radiation-induced cell cycle defects and increasedsensitivity to radiation. A-T iPSC can be cultured for prolongedperiods of time without acquisition of karyotypic instability, inagreement with the observation that ATM knockout inembryonic stem cells does not interfere with DSB repair andgenomic stability [111]. Fukawatase et al. also reported thatAT-iPSCs did not show any chromosomal instability in vitro forat least 80 passages (560 days) despite their parental A-T cellsshowing significant chromosomal abnormalities [112]. Severalgroups have now shown that A-T iPSC can be successfullydifferentiated into neural progenitors an appropriate experi-mental system for modeling A-T. Olfactory neurosphere-derived multipotent stem cells have also been generatedfrom patients with A-T which also represent a good diseasemodel for A-T [89]. The challenge ahead is to differentiatethese stem cells into the cell types that are most affected inA-T, for example into cerebellar cells which might be used for

1270 M. F. LAVIN ET AL.

regenerative medicine approaches with patients. However,before this can be attempted it is necessary to correct theATM mutations in each patient. This can now be achievedusing gene editing to correct the defective gene. One suchapproach is the CRISPR-Cas9 assisted homologous recombina-tion mediated gene repair [113,114]. CRISPR-Cas9 operatesthrough targeted introduction of dsDNA breaks that allowstrand invasion of a repair template (Figure 3). Since ATM iscentrally involved in dsDNA break repair, homologous recom-bination in A-T stem cells may prove to be particularly challen-ging. These resulting, corrected stem cells will need to bechecked for their efficacy and safety especially with respectto genomic sequence in animal models to confirm their ther-apeutic use in patients. These corrected stem cells frompatients represent an important resource for use as an iso-genic cell model for differentiation into neuronal cells ofinterest to screen for therapeutic agents.

5.2. Use of read-through of premature terminationcodons

Reading of the genetic code across nonsense mutations toexpress full-length normal protein and restore protein func-tion has been employed in a range of disease states [115].Important targets have included genes encoding the cysticfibrosis transmembrane conductance regulator (CFTR) and

dystrophin defective in Duchenne muscular dystrophy. Duet al. [116] used high-throughput screening of small-molecule libraries to identify novel read-through compounds(RTCs) that suppress all three stop codons (TGA, TAG, and TAA)in A-T. The two top candidates were RTC 13 and RTC 14 thatwere shown to induce low-levels of full-length functional ATM.Since the efficiency of read-through was low (<15%) and therewas some toxicity associated with RTC 13 their clinical benefitwas questionable. Subsequent studies by this group identifiedtwo novel compounds (GJ071 and GJ072) with low toxicity,capable of read-through in cells derived from patients withA-T with three different types of nonsense mutations [117].These compounds produced full-length ATM protein capableof being activated by radiation exposure and also which abro-gated radiosensitivity in these cells. Future studies are plannedin a mouse model prior to considering use in patients with A-T(Gatti RA, personal communication).

5.3. Use of antioxidants

There is increasing evidence for a role for oxidative stress inA-T that includes increased levels of ROS in a variety of A-T celltypes and in cells from Atm-deficient mice; high levels ofoxidative damage in A-T cells in culture; reduced antioxidantcapacity in the serum of patients with A-T and the capacity ofantioxidants to rescue several aspects of the A-T cellular

Figure 3. Genome editing in A-T using CRISPR-Cas9.(a) CRISPRs (clustered interspersed short palindromic repeats) are an RNA sequence that can be designed to bind to a specific DNA sequence. This CRSIPR associateswith the Cas9 protein which can cut the DNA. (b) CRISPR’s can be designed to target the specific DNA sequence (red highlighted region of the green double helixDNA strands) near the ATM mutation, shown here as the G > A mutation occurring in AT32ABR patient cells (denoted as A-T in the green double helix). (c) The Cas9protein specifically associates with the CRISPR RNA molecule then forms a specific DNA cut at the site creating a double strand break. (d) The cells endogenousrepair machinery will rapidly repair this break, shown are the two major repair pathways, non-homologous end joining (NHEJ) and homologous recombination (HR).Mutation correction requires a defined gene modification, this can only occur when the cell utilises the HR pathway. (e) Donor sequence (g-c in the green doublehelix). Use of drug resistance selection cassettes enables specific selection of these cells, which is likely to be required for successful editing in A-T stem cells such asthe ‘foot-printless’ approach of Yusa et al [114]. (f) When the cell uses the donor sequence which has DNA sequence homology to this region instead of the sisterchromatid the mutation can be edited. (g) Leaving a corrected ATM gene, shown by the return to g-c in the green double helix.

EXPERT OPINION ON ORPHAN DRUGS 1271

phenotype [118,119]. These observations together with thepresence of ATM in the cytoplasm, where it is associateswith both mitochondria and peroxisomes, and its activationby agents that cause oxidative damage, at concentrations notcausing DNA damage, support a role for this protein in pro-tecting against oxidative stress [53,54,57]. While one trial withlipoic acid has been conducted with little success, it is evidentfrom animal studies with several different antioxidants thatprotection against neurological changes and cancer develop-ment occurs as well as extended life-span [120–122].

6. Expert opinion

At present there is no established treatment that prevents orslows the progress of symptoms for the human genetic dis-order A-T. This is a multisystem disease that involves the brain,immune system, the lungs, the endocrine systems, and theliver and is also characterized by a high susceptibility todeveloping lymphoid and other tumors. Notwithstandingthis, recent data on intra-erythrocyte delivery of dexametha-sone (EryDex) provide evidence of continuous neurologicimprovement in patients with A-T. Since this is a multisystemdisease it is not surprising that a number of specialist A-Tclinics have been established in Australia (Brisbane), Israel(Tel Aviv), Italy (Rome), Germany (Frankfurt), UK (Nottingham)and US (Baltimore). Patients are best managed under a multi-disciplinary team covering the many areas of expertiserequired for treatment, including the obvious ones in immu-nology, neurology, respiratory medicine etc. as well as phy-siotherapy and speech therapy.

Patients with A-T are primarily detected either by an immu-nologist or a neurologist although sometimes present to respira-tory physicians with recurrent respiratory infections. This is aprimary immunodeficiency disorder affecting humoral immunity,cellular immunity and there is a growing body of evidence for adefect in innate immunity in A-T. While numbers of B-cells arelargely normal in A-T there is an intrinsic defect in these cells dueto defective class switch recombination [36]. This in turn leads toreduced synthesis of immunoglobulins with a marked deficiencyin IgA and poor antibody response in many cases. Prophylactictreatment with immunoglobulin replacement therapy (IVIG) isoften recommended for patients with a history of recurrentinfections, which reduces the number and severity of theseinfections. Although IVIG may improve the ability of somepatients to handle infections, blind treatment with antibioticssuch as trimethoprim-sulfamethoxazole (TMP-SMX) is also pre-scribed as a prophylactic measure [123]. However, it is evidentthat respiratory disease including bronchiectasis and interstitiallung disease arises in a significant number of patients accountingfor up to 40% of the morbidity and mortality in this disorder. Theprogress of lung disease in A-T resembles that in cystic fibrosis(CF) and it has been suggested that therapies used to improvethe quality of life in CF (e.g. bronchodilators, intravenous anti-biotics and anti-inflammatory agents) be employed for patientswith A-T [9]. Prophylactic antibiotics are prescribed for patientswith recurrent infection but this is done blindly in most casessince microbiological evaluation will not have taken place andthere is the added risk of bacterial resistance developing. Very

few studies have been conducted on microorganisms infectingthe respiratory tract of patients with A-T. Cultures establishedfrom respiratory secretions performed during acute pulmonaryexacerbation identified Staphylococcus aureus, Streptococcuspneumoniae, Haemophilus influenza, Pseudomonas aeruginosaand other gram negative bacilli [9,10]. It remains unclear whatthe etiology of the lung disease is and how persistent orrepeated infections from these microorganisms, together withcomplications from dysfunctional swallowing and aspiration,contribute to the progress of lung disease. Evidence for theinvolvement of oxidative stress is accumulating in investigationsof patients with A-T, studies in cultured A-T cells and in Atm-deficient animal models [118,124–127]. These include elevatedlevels of reactive oxygen species (ROS) in cells and tissues, pro-tection by antioxidants and the capacity of ATM to recognize andbe activated by stimuli that lead to oxidative stress [56,128]. Arecent report demonstrated that one of the microorganismsidentified in the respiratory tract of patients with A-T,S. pneumoniae, caused DNA damage and death of lung epithelialcells by a mechanism that induces oxidative stress [129]. Thesedata suggest that S. pneumoniae together with other microor-ganisms invading the respiratory tract may contribute to deathof airway epithelial cells and thus to the progressive lung diseasein patients.

A separate investigation has shown that loss of ATM impairsinflammasome-dependant anti-bacterial innate immunity asdetermined by diminished caspase 1 and IL-1β responses afterbacterial infection [13]. The authors further demonstrated thatoxidative stress was responsible for inhibition of the inflamma-some, impaired innate immunity and higher susceptibility tobacterial infection. This is consistent with increased levels ofROS in A-T cells and in Atm-deficient mice [130,131]. However,these results appear to be at variance with data from a previousstudy Hartlova et al. [12] where they revealed the presence ofcytoplasmic DNA in A-T cells and in Atm-deficient mice whichenhanced antiviral and antibacterial responses. Contrary to theErttmann et al. [13] report these results point to a consistentlyhigh innate immune response in A-T cells and Atm mutant mice.Such an inflammatory phenotype is consistent with the capacityof steroids to alleviate the neurological symptoms in patientswith A-T [103–105].

Overall oxidative stress and inflammation are emergingas important hallmarks of patients with A-T. Whether bothof these are interrelated or whether they represent threatsto different tissues in patients remains to be resolved. Therehave also been a number of reports of liver disease in A-Twhich are further supported by a recent clinical trial thatreports fatty liver and abnormal liver enzymes in approxi-mately 40% of patients. This is particularly interesting in thecontext of oxidative stress since it has been shown pre-viously that Atm-mutant mice have increased hepatic iron,serum iron and ferritin [132]. Furthermore, iron chelatorshave been shown to reduce chromosomal breaks in A-Tcells and when combined with antioxidants were evenmore effective in maintaining genome stability [133]. If thiswere to translate to patients the presence of excess iron inthe liver and indeed in other tissues would lead toenhanced levels of ROS generated through the Fenton reac-tion [134]. The association of oxidative stress and

1272 M. F. LAVIN ET AL.

inflammation with different aspects of this multisystem dis-ease (e.g. neurodegeneration, lung disease) offer new pos-sibilities for therapy.

Funding

We acknowledge funding from the National Health and Medical ResearchCouncil (NHMRC) (GNT1020028), Australia, BrAshA-T Foundation, Australia(RM2016001474), and The A-T Children’s Project, USA (RM2016000563).

Declaration of interest

The authors have no other relevant affiliations or financial involvement withany organization or entity with a financial interest in or financial conflict withthe subject matter or materials discussed in the manuscript. This includesemployment, consultancies, honoraria, stock ownership or options, experttestimony, grants or patents received or pending, or royalties.

References

Papers of special note have been highlighted as either of interest (•) or ofconsiderable interest (••) to readers.

1. Savitsky K, Bar-Shira A, Gilad S, et al. A single ataxia telangiectasiagene with a product similar to PI-3 kinase. Science.1995;268:1749–1753.

•• Seminal description of the gene defective in A-T, which her-alded a multitude of studies on how the protein (ATM) func-tions to protect against neurodegeneration and otherphenotypes.

2. Boder E, Sedgwick RP Ataxia-telangiectasia; a familial syndrome ofprogressive cerebellar ataxia, oculocutaneous telangiectasia andfrequent pulmonary infection. A Preliminary Report on 7 children,an autopsy, and a case history: USC Med Bull; 1957.

3. Biemond A. [Acute ataxia in children]. Ned Tijdschr Geneeskd.1957;101:529–532.

4. Sedgewick RP, Boder E. Ataxia-telangiectasia. In: Vinken BG, editor.Handbook of clinical neurology. Vol. 14. Amsterdam: North HollandPublishers; 1972. p. 267–339.

5. Taylor AMR, Byrd PJ. Molecular pathology of ataxia telangiectasia. JClin Pathol. 2005;58:1009–1015.

6. Verhagen MMM, Martin JJ, Van Deuren M, et al. Neuropathology inclassical and variant ataxia-telangiectasia. Neuropathology.2012;32:234–244..

• Draws attention to extracerebellar regions of the brain such asbrain stem and spinal cord affected in A-T

7. Mcfarlin DE, Waldmann TA, Strober W. Ataxia-telangiectasia.Medicine. 1972;51:281.

8. Peterson RD, Kelly WD, Good RA. Ataxia-telangiectasia: Its associa-tion with a defective thymus, immunological-deficiency disease,and malignancy. Lancet 1964;13:1189–1193

9. Schroeder SA, Zielen S. Infections of the respiratory system inpatients with ataxia-telangiectasia. Pediatr Pulm. 2014;49:389–399..

• A retrospective study on pulmonary disease in A-T patientsdrawing parallels with the similarities to lung disease in cysticfibrosis

10. Bhatt JM, Bush A. Microbiological surveillance in lung disease inataxia telangiectasia. Eur Respir J. 2014;43:1797–1801.

11. McGrath-Morrow SA, Collaco JM, Crawford TO, et al. Elevatedserum IL-8 levels in ataxia telangiectasia. J Pediatr-US.2010;156:682–U213.

12. Hartlova A, Erttmann SF, Raffi FAM, et al. DNA damage primes thetype I interferon system via the cytosolic DNA sensor STING to pro-mote anti-microbial innate immunity. Immunity. 2015;42:332–343.

13. Erttmann SF, Hartlova A, Sloniecka M, et al. Loss of the DNAdamage repair kinase ATM impairs inflammasome-dependentanti-bacterial innate immunity. Immunity. 2016;45:106–118.

14. McGrath-Morrow SA, Gower WA, Rothblum-Oviatt C, et al.Evaluation and management of pulmonary disease inataxia-telangiectasia. Pediatr Pulmonol. 2010;45:847–859.

15. McGrath-Morrow SA, Lederman HM, Aherrera AD, et al. Pulmonaryfunction in children and young adults with ataxia telangiectasia.Pediatr Pulm. 2014;49:84–90.

16. Spector BD, Filipovich AH, Perry GSI, et al. Epidemiology of cancerin ataxia-telangiectasia. In: Bridges BA, Harnden DG, editors. Ataxiatelangiectasia: a cellular and molecular link between cancer, neu-ropathology and immune deficiency. New York: Wiley; 1982. p.103–138.

17. Lavin MF, Gueven N, Bottle S, et al. Current and potential thera-peutic strategies for the treatment of ataxia-telangiectasia. Brit MedBull. 2007;81-82:129–147.

18. Davis MM, Gatti RA, Sparks RS. Neoplasia and chromosomal break-age in ataxia-telangiectasia. In: Gatti R, Harnden DG, editors. Ataxiatelangiectasia: a cellular and molecular link between cancer, neu-ropathology and immune deficiency. New York: Alan R. Liss, Inc;1985. p. 197–203.

19. Barlow C, Hirotsune S, Paylor R, et al. ATM-deficient mice: a para-digm of ataxia telangiectasia. Cell. 1996;86:159–171.

20. Xu Y, Baltimore D. Dual roles of ATM in the cellular response toradiation and in cell growth control. Gene Dev. 1996;10:2401–2410.

21. Hecht F, Hecht BK. Cancer in ataxia-telangiectasia patients. CancerGenet Cytogen. 1990;46:9–19.

22. Swift M, Morrell D, Massey RB, et al. Incidence of cancer in 161families affected by ataxia-telangiectasia. New Engl J Med.1991;325:1831–1836.

23. Bhatt JM, A B, van Gerven M, et al. ERS statement on the multi-disciplinary respiratory management of ataxia telangiectasia. EurRespir Rev. 2015;24:565–581.

• Describes respiratory defects in A-T, including chronic and recur-rent infections; bronchiectasis and interstitial lung disease; immu-nodeficiency and aspiration due to incoordinate swallowing

24. Waldmann TA, Mcintire KR. Serum-alpha-fetoprotein levels inpatients with ataxia-telangiectasia. Lancet. 1972;2:1112.

25. Jung CG, Kim HJ, Kawaguchi M, et al. Homeotic factor ATBF1induces the cell cycle arrest associated with neuronaldifferentiation. Development. 2005;132:5137–5145.

26. Schalch DS, McFarlin DE, Barlow MH. An unusual form of diabetesmellitus in ataxia telangiectasia. N Engl J Med. 1970;282:1396–1402.

27. Srisirirojanakorn N, Finegold MJ, Gopalakrishna GS, et al. Hepaticveno-occlusive disease in ataxia-telangiectasia. J Pediatr.1999;134:786–788.

28. Amromin GD, Boder E, Teplitz R. Ataxia-telangiectasia with a32 year survival. A clinicopathological report. J Neuropathol ExpNeurol. 1979;38:621–643.

29. Caballero T, Caba-Molina M, Salmeron J, et al. Nonalcoholic stea-tohepatitis in a patient with ataxia-telangiectasia. Case ReportsHepatol. 2014;2014:761250.

30. Weiss B, Krauthammer A, Soudack M, et al. Liver disease in pediatricpatients with ataxia telangiectasia: a novel report. J PediatrGastroenterol Nutr. 2016;62:550–555.

31. Mercer JR, Cheng KK, Figg N, et al. DNA damage links mitochon-drial dysfunction to atherosclerosis and the metabolic syndrome.Circ Res. 2010;107:1021–1031.

32. Bar RS, Levis WR, Rechler MM, et al. Extreme insulin resistance inataxia telangiectasia - defect in affinity of insulin receptors. NewEngl J Med. 1978;298:1164–1171.

33. Yang DQ, Kastan MB. Participation of ATM in insulin signallingthrough phosphorylation of eIf-4E-binding protein 1. Nat Cell Biol.2000;2:893–898.

34. Schneider JG, Finck BN, Ren J, et al. ATM-dependent suppression ofstress signaling reduces vascular disease in metabolic syndrome.Cell Metab. 2006;4:377–389.

EXPERT OPINION ON ORPHAN DRUGS 1273

35. Takagi M, Uno H, Nishi R, et al. ATM regulates adipocyte differen-tiation and contributes to glucose homeostasis. Cell Rep. 2015;10(6):957–967.

36. Reina-San-Martin B, Chen HT, Nussenzweig A, et al. ATM is requiredfor efficient recombination between immunoglobulin switchregions. J Exp Med. 2004;200:1103–1110.

37. Lumsden J, McCarty T, Petiniot L, et al. Immunoglobulin classswitch recombination is impaired in ATM-deficient mice. Faseb J.2005;19:A16–A.

38. Vacchio MS, Olaru A, Livak F, et al. ATM deficiency impairs thymo-cyte maturation because of defective resolution of T cell receptor alocus coding end breaks. P Natl Acad Sci USA. 2007;104:6323–6328.

39. McConville CM, Stankovic T, Byrd PJ, et al. Mutations associatedwith variant phenotypes in ataxia-telangiectasia. Am J Hum Genet.1996;59:320–330.

40. Nakamura K, Du LT, Tunuguntla R, et al. Functional characterizationand targeted correction of ATM mutations identified in japanesepatients with ataxia-telangiectasia. Hum Mutat. 2012;33:198–208.

41. Aurias A, Dutrillaux B, Buriot D, et al. High-frequencies of inversionsand translocations of chromosomes 7 and 14 in ataxia telangiectasia.Mutat Res. 1980;69:369–374.

42. Meyn MS. High spontaneous intrachromosomal recombinationrates in ataxia-telangiectasia. Science. 1993;260:1327–1330.

43. Taylor AMR. Unrepaired DNA strand breaks in irradiated ataxia telan-giectasia lymphocytes suggested from cytogenetic observations.Mutat Res. 1978;50:407–418.

44. Gotoff SP, Amirmokri E, Liebner EJ. Ataxia telangiectasia - neoplasiauntoward response to X-irradiation and tuberous sclerosis. Am JDis Child. 1967;114:617.

45. Morgan JL, Holcomb TM, Morrissey R. Radiation reaction in ataxiatelangiectasia. Am J Dis Child. 1968;116:557.

46. Taylor AM, Harnden DG, Arlett CF, et al. Ataxia telangiectasia: ahuman mutation with abnormal radiation sensitivity. Nature.1975;258:427–429.

47. Gatti RA, Berkel I, Boder E, et al. Localization of an ataxia-telangiectasiagene to chromosome 11q22-23. Nature. 1988;336:577–580.

48. Matsuoka S, Ballif BA, Smogorzewska A, et al. ATM and ATR sub-strate analysis reveals extensive protein networks responsive toDNA damage. Science. 2007;316:1160–1166.

49. Brown KD, Ziv Y, Sadanandan SN, et al. The ataxia-telangiectasiagene product, a constitutively expressed nuclear protein that is notup-regulated following genome damage. P Natl Acad Sci USA.1997;94:1840–1845.

50. Lavin MF. Ataxia-telangiectasia: from a rare disorder to a paradigm forcell signalling and cancer. Nat Rev Mol Cell Biol. 2008;9:759–769.

51. McKinnon PJ. ATM and the molecular pathogenesis of ataxiatelangiectasia. Annu Rev Pathol-Mech. 2012;7:303–321.

52. Shiloh Y, Lederman HM. Ataxia-telangiectasia (A-T): an emergingdimension of premature ageing. Ageing Res Rev. 2016 May 12. pii:S1568–1637(16)30078-2. doi:10.1016/j.arr.2016.05.002. [Epub aheadof print].

53. Watters D, Kedar P, Spring K, et al. Localization of a portion of extra-nuclear ATM to peroxisomes. J Biol Chem. 1999;274:34277–34282.

54. Zhang JW, Tripathi DN, Jing J, et al. ATM functions at the peroxi-some to induce pexophagy in response to ROS. Nat Cell Biol.2015;17:1259.

55. Valentin-Vega YA, MacLean KH, Tait-Mulder J, et al. Mitochondrialdysfunction in ataxia-telangiectasia. Blood. 2012;119:1490–1500.

56. Guo Z, Kozlov S, Lavin MF, et al. ATM activation by oxidative stress.Science. 2010;330:517–521.

57. Morita A, Tanimoto K, Murakami T, et al. Mitochondria are requiredfor ATM activation by extranuclear oxidative stress in culturedhuman hepatoblastoma cell line Hep G2 cells. Biochem Bioph ResCo. 2014;443:1286–1290.

58. Nakamura K, Fike F, Haghayegh S, et al. A-TWinnipeg: pathogenesisof rare ATM missense mutation c.6200C>A with decreased proteinexpression and downstream signaling, early-onset dystonia, cancer,and life-threatening radiotoxicity. Mol Genet Genomic Med.2014;2:332–340.

59. Verhagen MM, Last JI, Hogervorst FB, et al. Presence of ATM proteinand residual kinase activity correlates with the phenotype inataxia-telangiectasia: a genotype-phenotype study. Hum Mutat.2012;33:561–571.

60. Barone G, Groom A, Reiman A, et al. Modeling ATM mutant pro-teins from missense changes confirms retained kinase activity.Hum Mutat. 2009;30:1222–1230.

61. Romano S, Coarelli G, Marcotulli C, et al. Riluzole in patients withhereditary cerebellar ataxia: a randomised, double-blind,placebo-controlled trial. Lancet Neurol. 2015;14:985–991.

62. Pommerening H, van Dullemen S, Kieslich M, et al. Body composi-tion, muscle strength and hormonal status in patients with ataxiatelangiectasia: a cohort study. Orphanet J Rare Dis. 2015 Dec9;10:155. doi:10.1186/s13023-015-0373-z

63. Voss S, Pietzner J, Hoche F, et al. Growth retardation and growthhormone deficiency in patients with ataxia telangiectasia. GrowthFactors. 2014;32:123–129.

64. Dzieciatkowska M, Qi G, You J, et al. Proteomic characterization ofcerebrospinal fluid from ataxia-telangiectasia (A-T) patients using aLC/MS-based label-free protein quantification technology. Int JProteomics. 2011;2011:578903.

65. Sandlund JT, Hudson MM, Kennedy W, et al. Pilot study of modifiedLMB-based therapy for children with ataxia-telangiectasia andadvanced stage high grade mature B-cell malignancies. PediatrBlood Cancer. 2014;61:360–362..

• Describes treatment protocol for A-T patients with cancer andthe need for treatments with less toxicity

66. Nowak-Wegrzyn A, Crawford TO, Winkelstein JA, et al.Immunodeficiency and infections in ataxia-telangiectasia. J Pediatr-Us. 2004;144:505–511.

67. Dournes G, Menut F, Macey J, et al. Lung morphology assessmentof cystic fibrosis using MRI with ultra-short echo time at submilli-meter spatial resolution. Eur Radiol. 2016;26(11):3811–3820.

68. Tiddens HA, Stick SM, Wild JM, et al. Respiratory tract exacerbationsrevisited: ventilation, inflammation, perfusion, and structure (VIPS)monitoring to redefine treatment. Pediatr Pulmonol. 2015;50(Suppl40):S57–S65.

69. Czovek D, Shackleton C, Hantos Z, et al. 2016. Tidal changes inrespiratory resistance are sensitive indicators of airway obstructionin children. Thorax. Epub in press. doi:10.1136/thoraxjnl-2015-208182

70. Felix E, Gimenes AC, Costa-Carvalho BT. Effects of inspiratory mus-cle training on lung volumes, respiratory muscle strength, andquality of life in patients with ataxia telangiectasia. PediatrPulmonol. 2014;49:238–244.

71. Varon R, Demuth I, Digweed M. Nijmegen Breakage Syndrome. In:Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews(R).Seattle (WA): University of Washington; 1993.

72. Waltes R, Kalb R, Gatei M, et al. Human RAD50 deficiency in aNijmegen breakage syndrome-like disorder. Am J Hum Genet.2009;84:605–616.

73. Nissenkorn A, Levi YB, Vilozni D, et al. Neurologic presentation inchildren with ataxia-telangiectasia: is small head circumference ahallmark of the disease? J Pediatr-Us. 2011;159:466–U526.

74. Crawford TO, Mandir AS, Lefton-Greif MA, et al. Quantitative neurologicassessment of ataxia-telangiectasia. Neurology. 2000;54:1505–1509.

•• Designed A-T scores with a multidimensional index to demon-strate a very high correlation of progression of disease with age.

75. Jackson TJ, Chow G, Suri M, et al. Longitudinal analysis of theneurological features of ataxia-telangiectasia. Dev Med ChildNeurol. 2016;58:690–697.

76. Woods CG, Taylor AM. Ataxia telangiectasia in the British Isles: theclinical and laboratory features of 70 affected individuals. Q J Med.1992;82:169–179.

77. Moin M, Aghamohammadi A, Kouhi A, et al. Ataxia-telangiectasia inIran: clinical and laboratory features of 104 patients. Pediatr Neurol.2007;37:21–28.

78. Berkun Y, Vilozni D, Levi Y, et al. Reversible airway obstruction inchildren with ataxia telangiectasia. Pediatr Pulm. 2010;45:230–235.

1274 M. F. LAVIN ET AL.

79. Kieslich M, Hoche F, Reichenbach J, et al. ExtracerebellarMRI-lesions in ataxia telangiectasia go along with deficiency ofthe GH/IGF-1 axis, markedly reduced body weight, high ataxiascores and advanced age. Cerebellum. 2010;9:190–197.

80. Ross LJ, Capra S, Baguley B, et al. Nutritional status of patients withataxia-telangiectasia: a case for early and ongoing nutrition sup-port and intervention. J Paediatr Child H. 2015;51:802–807..

• Demonstrated profound malnutrition in Australian patientswith A-T and the need for early nutrition intervention

81. Stewart E, Prayle AP, Tooke A, et al. Growth and nutrition inchildren with ataxia telangiectasia. Arch Dis Child. 2016.doi:10.1136/archdischild-2015-310373

82. da Silva R, Dos Santos-Valente EC, Scomparini FB, et al. The rela-tionship between nutritional status, vitamin A and zinc levels andoxidative stress in patients with ataxia-telangiectasia. AllergolImmunopath. 2014;42:329–335.

83. Boder E. Ataxia-telangiectasia: an overview. Kroc Found Ser.1985;19:1–63.

•• First comprehensive description of clinical and pathologicalfindings in A-T.

84. Bagley J, Cortes ML, Breakefield XO, et al. Bone marrow transplan-tation restores immune system function and prevents lymphoma inATM-deficient mice. Blood. 2004;104:572–578.

85. Ghosh S, Schuster FR, Binder V, et al. Fatal outcome despite fulllympho-hematopoietic reconstitution after allogeneic stem celltransplantation in atypical ataxia telangiectasia. J Clin Immunol.2012;32:438–440.

86. Ussowicz M, Musial J, Duszenko E, et al. Long-term survival afterallogeneic-matched sibling PBSC transplantation with conditioningconsisting of low-dose busilvex and fludarabine in a 3-year-old boywith ataxia-telangiectasia syndrome and ALL. Bone MarrowTranspl. 2013;48:740–741.

87. Beier R, Sykora KW, Woessmann W, et al. Allogeneic-matched sib-ling stem cell transplantation in a 13-year-old boy with ataxiatelangiectasia and EBV-positive non-Hodgkin lymphoma. BoneMarrow Transplant. 2016;51:1271–1274.

88. Sandoval C, Swift M. Treatment of lymphoid malignancies inpatients with ataxia-telangiectasia. Med Pediatr Oncol.1998;31:491–497.

89. Stewart R, Kozlov S, Matigian N, et al. A patient-derived olfactorystem cell disease model for ataxia-telangiectasia. Human MolecularGenetics. 2013;22:2495–2509.

90. Nayler S, Gatei M, Kozlov S, et al. Induced pluripotent stem cellsfrom ataxia-telangiectasia recapitulate the cellular phenotype.Stem Cell Transl Med. 2012;1:523–535.

91. Olsen JH, Hahnemann JM, Borresen-Dale AL, et al. Cancer inpatients with ataxia-telangiectasia and in their relatives in theNordic countries. J Natl Cancer I. 2001;93:121–127.

92. Chessa L, Micheli R, Molinaro A. Focusing new ataxia telangiectasiatherapeutic approaches. J Rare Disorders. 2016;2:2.

93. Seidemann K, Henze G, Beck JD, et al. Non-Hodgkin’s lymphoma inpediatric patients with chromosomal breakage syndromes (ATand NBS): experience from the BFM trials. Ann Oncol.2000;11:141–145.

94. Bienemann K, Burkhardt B, Modlich S, et al. Promising therapyresults for lymphoid malignancies in children with chromosomalbreakage syndromes (Ataxia teleangiectasia or Nijmegen-breakagesyndrome): a retrospective survey. Brit J Haematol.2011;155:468–476.

95. Dembowska-Baginska B, Perek D, Brozyna A, et al. Non-HodgkinLymphoma (NHL) in children with Nijmegen Breakage Syndrome(NBS). Pediatr Blood Cancer. 2009;52:186–190.

96. Patte C, Auperin A, Michon J, et al. The Societe Francaised’Oncologie pediatrique LMB89 protocol: highly effective multia-gent chemotherapy tailored to the tumor burden and initialresponse in 561 unselected children with B-cell lymphomas andL3 leukemia. Blood. 2001;97:3370–3379.

97. Perlman SL. Cerebellar ataxia. Curr Treat Options Neurol.2000;2:215–224.

98. Perlman S, Becker-Catania S, Gatti RA. Ataxia-telangiectasia: diag-nosis and treatment. Semin Pediatr Neurol. 2003;10:173–182.

99. Takei A, Hamada T, Yabe I, et al. Treatment of cerebellar ataxia with5-HT1A agonist. Cerebellum. 2005;4:211–215.

100. Hoche F, Seidel K, Theis M, et al. Neurodegeneration in ataxiatelangiectasia: what is new? What is evident? Neuropediatrics.2012;43:119–129.

101. Broccoletti T, Del Giudice E, Amorosi S, et al. Steroid-inducedimprovement of neurological signs in ataxia-telangiectasiapatients. Eur J Neurol. 2008;15:223–228.

102. Russo I, Cosentino C, Del Giudice E, et al. In ataxia-teleangiectasiabetamethasone response is inversely correlated to cerebellar atro-phy and directly to antioxidative capacity. Eur J Neurol.2009;16:755–759.

103. Broccoletti T, Del Giudice E, Cirillo E, et al. Efficacy of very-low-dosebetamethasone on neurological symptoms in ataxia-telangiectasia.Eur J Neurol. 2011;18:564–570.

104. Zannolli R, Buoni S, Betti G, et al. A randomized trial of oralbetamethasone to reduce ataxia symptoms in ataxiatelangiectasia. Movement Disord. 2012;27:1312–1316.

105. Chessa L, Leuzzi V, Plebani A, et al. Intra-erythrocyte infusion ofdexamethasone reduces neurological symptoms in ataxia telean-giectasia patients: results of a phase 2 Trial. Orphanet J Rare Dis.2014;9:5. doi:10.1186/1750-1172-9-5

106. Leuzzi V, Micheli R, D’Agnano D, et al. Positive effect oferythrocyte-delivered dexamethasone in ataxia-telangiectasia.Neurol Neuroimmunol Neuroinflamm. 2015;2:e98.

107. Biagiotti S, Menotta M, Orazi S, et al. Dexamethasone improves redoxstate in Ataxia Telangiectasia cells by promoting NRF2-mediatedantioxidant response. FEBS J. 2016. doi:10.1111/febs.13901

108. Nissenkorn A, Borgohain R, Micheli R, et al. Development of globalrating instruments for pediatric patients with ataxia telangiectasia.Eur J Paediatr Neuro. 2016;20:140–146.

109. Nissenkorn A, Hassin-Baer S, Lerman SF, et al. Movement disorderin ataxia-telangiectasia: treatment with amantadine sulfate. J ChildNeurol. 2013;28:155–160.

110. Yorek MA, Dunlap JA, Manzo-Fontes A, et al. Abnormalmyo-inositol and phospholipid metabolism in cultured fibroblastsfrom patients with ataxia telangiectasia. Biochim Biophys Acta.1999;1437:287–300.

111. Adams BR, Hawkins AJ, Povirk LF, et al. ATM-independent,high-fidelity nonhomologous end joining predominates in humanembryonic stem cells. Aging (Albany NY). 2010;2:582–596.

112. Fukawatase Y, Toyoda M, Okamura K, et al. Ataxia telangiectasiaderived iPS cells show preserved x-ray sensitivity and decreasedchromosomal instability. Sci Rep-Uk. 2014;4. Article number: 5421.doi:10.1038/srep05421

113. Li HL, Gee P, Ishida K, et al. Efficient genomic correction methods inhuman iPS cells using CRISPR-Cas9 system. Methods. 2016;101:27–35.

114. Yusa K, Rashid ST, Strick-Marchand H, et al. Targeted gene correc-tion of alpha(1)-antitrypsin deficiency in induced pluripotent stemcells. Nature. 2011;478:391.

115. Keeling KM, Wang D, Conard SE, et al. Suppression of prematuretermination codons as a therapeutic approach. Crit Rev BiochemMol. 2012;47:444–463.

116. Du LT, Damoiseaux R, Nahas S, et al. Nonaminoglycoside com-pounds induce readthrough of nonsense mutations. J Exp Med.2009;206:2285–2297.

117. Du LT, Jung ME, Darnoiseaux R, et al. A new series of smallmolecular weight compounds induce read through of all threetypes of nonsense mutations in the ATM gene. Mol Ther.2013;21:1653–1660.

118. Reichenbach J, Schubert R, Schindler D, et al. Elevated oxidativestress in patients with ataxia telangiectasia. Antioxid Redox Sign.2002;4:465–469.

119. Reliene R, Schiestl RH. Experimental antioxidant therapy in ataxiatelangiectasia. Clin Med Oncol. 2008;2:431–436.

120. Gueven N, Luff J, Peng C, et al. Dramatic extension of tumor latencyand correction of neurobehavioral phenotype in ATM-mutant mice

EXPERT OPINION ON ORPHAN DRUGS 1275

with a nitroxide antioxidant. Free Radical Bio Med.2006;41:992–1000.

121. Reliene R, Fleming SM, Chesselet MF, et al. Effects of antioxidantson cancer prevention and neuromotor performance in ATM defi-cient mice. Food Chem Toxicol. 2008;46:1371–1377.

122. Schubert R, Erker L, Barlow C, et al. Cancer chemoprevention by theantioxidant tempol in ATM-deficient mice. Hum Mol Genet.2004;13:1793–1802.

123. Chin T, Alonazi N B-cell and T-cell combined disorders medication2014. Available from: http://emedicine.medscape.com/article/885493-medication#showall

124. Chen WT, Ebelt ND, Stracker TH, et al. ATM regulation of IL-8 linksoxidative stress to cancer cell migration and invasion. Elife. 2015;4.doi:10.7554/eLife.07270

125. Yang Y, Hui CW, Li JL, et al. The Interaction of the ATM Genotype withinflammation and oxidative stress (vol 9, e85863, 2014). Plos One. 2014.Jan 20;9(1):e85863. doi:10.1371/journal.pone.0085863. eCollection2014.

126. Kamsler A, Daily D, Hochman A, et al. Increased oxidative stress inataxia telangiectasia evidenced by alterations in redox state ofbrains from ATM-deficient mice. Cancer Res. 2001;61:1849–1854.

127. Chen P, Peng C, Luff J, et al. Oxidative stress is responsible fordeficient survival and dendritogenesis in Purkinje neurons from

ataxia-telangiectasia mutated mutant mice. J Neurosci.2003;23:11453–11460.

128. Paull TT, Lee JH, Ditch S, et al. Mechanisms of ATM activation.Proceedings of the 103rd Annual Meeting of the AmericanAssociation for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL.Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nrSY11-03. doi:10.1158/1538-7445.AM2012-SY11-03.

129. Rai P, Parrish M, Tay IJJ, et al. Streptococcus pneumoniae secreteshydrogen peroxide leading to DNA damage and apoptosis in lungcells. P Natl Acad Sci USA. 2015;112:E3421–E3430.

130. Quick KL, Dugan LL. Superoxide stress identifies neurons at risk in amodel of ataxia-telangiectasia. Ann Neurol. 2001;49:627–635.

131. Kim J, Wong PKY. Oxidative stress is linked to ERK1/2-p16signaling-mediated growth defect in ATM-deficient astrocytes. JBiol Chem. 2009;284:14396–14404.

132. McDonald CJ, Ostini L, Wallace DF, et al. Iron loading and oxidativestress in the ATM(-/-) mouse liver. Am J Physiol-Gastr L. 2011;300:G554–G60.

133. Shackelford RE, Fu YM, Manuszak RP, et al. Iron chelators reducechromosomal breaks in ataxia-telangiectasia cells. DNA Repair.2006;5:1327–1336.

134. Winterbourn CC. Toxicity of iron and hydrogen peroxide: theFenton reaction. Toxicol Lett. 1995;82–3:969–974.

1276 M. F. LAVIN ET AL.