Phenotype and natural history of mitochondrial membrane protein-associated neurodegeneration.

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is an ultraorphan neurogenetic disease from the group of neurodegeneration with brain iron accumulation (NBIA) disorders. Here we report cross-sectional and longitudinal data to define the phenotype, to assess disease progression and to estimate sample sizes for clinical trials. We enrolled patients with genetically confirmed MPAN from the Treat Iron-Related Childhood-Onset Neurodegeneration (TIRCON) registry and cohort study, and from additional sites. Linear mixed-effect modelling (LMEM) was used to calculate annual progression rates for the Unified Parkinson's Disease Rating Scale (UPDRS), Barry-Albright Dystonia (BAD) scale, Schwab and England Activities of Daily Living (SE-ADL) scale and the Pediatric Quality of Life Inventory (PedsQL). We investigated 85 MPAN patients cross-sectionally, with functional outcome data collected in 45. Median age at onset was 9 years and the median diagnostic delay was 5 years. The most common findings were gait disturbance (99%), pyramidal involvement (95%), dysarthria (90%), vision disturbances (82%), with all but dysarthria presenting early in the disease course. After 16 years with the disease, 50% of patients were wheelchair dependent. LMEM showed an annual progression rate of 4.5 points in total UPDRS. The total BAD scale score showed no significant progression over time. The SE-ADL scale and the patient- and parent-reported PedsQL showed a decline of 3.9%, 2.14 and 2.05 points, respectively. No patient subpopulations were identified based on longitudinal trajectories. Our cross-sectional results define the order of onset and frequency of symptoms in MPAN, which will inform the diagnostic process, help to shorten diagnostic delay and aid in counselling patients, parents and caregivers. Our longitudinal findings define the natural history of MPAN, reveal the most responsive outcomes and highlight the need for an MPAN-specific rating approach. Our sample size estimations inform the design of upcoming clinical trials.

A Potential Citrate Shunt in Erythrocytes of PKAN Patients Caused by Mutations in Pantothenate Kinase 2.

Pantothenate kinase-associated neurodegeneration (PKAN) is a progressive neurodegenerative disease caused by mutations in the pantothenate kinase 2 (PANK2) gene and associated with iron deposition in basal ganglia. Pantothenate kinase isoforms catalyze the first step in coenzyme A (CoA) biosynthesis. Since PANK2 is the only isoform in erythrocytes, these cells are an excellent ex vivo model to study the effect of PANK2 point mutations on expression/stability and activity of the protein as well as on the downstream molecular consequences. PKAN erythrocytes containing the T528M PANK2 mutant had residual enzyme activities but variable PANK2 abundances indicating an impaired regulation of the protein. Patients with G521R/G521R, G521R/G262R, and R264N/L275fs PANK2 mutants had no residual enzyme activity and strongly reduced PANK2 abundance. G521R inactivates the catalytic activity of the enzyme, whereas G262R and the R264N point mutations impair the switch from the inactive to the active conformation of the PANK2 dimer. Metabolites in cytosolic extracts were analyzed by gas chromatography-mass spectrometry and multivariate analytic methods revealing changes in the carboxylate metabolism of erythrocytes from PKAN patients as compared to that of the carrier and healthy control. Assuming low/absent CoA levels in PKAN erythrocytes, changes are consistent with a model of altered citrate channeling where citrate is preferentially converted to α-ketoglutarate and α-hydroxyglutarate instead of being used for de novo acetyl-CoA generation. This finding hints at the importance of carboxylate metabolism in PKAN pathology with potential links to reduced cytoplasmic acetyl-CoA levels in neurons and to aberrant brain iron regulation.

A Nation-Wide, Multi-Center Study on the Quality of Life of ALS Patients in Germany.

Improving quality of life (QoL) is central to amyotrophic lateral sclerosis (ALS) treatment. This Germany-wide, multicenter cross-sectional study analyses the impact of different symptom-specific treatments and ALS variants on QoL. Health-related QoL (HRQoL) in 325 ALS patients was assessed using the Amyotrophic Lateral Sclerosis Assessment Questionnaire 5 (ALSAQ-5) and EuroQol Five Dimension Five Level Scale (EQ-5D-5L), together with disease severity (captured by the revised ALS Functional Rating Scale (ALSFRS-R)) and the current care and therapies used by our cohort. At inclusion, the mean ALSAQ-5 total score was 56.93 (max. 100, best = 0) with a better QoL associated with a less severe disease status (ß = -1.96 per increase of one point in the ALSFRS-R score, p < 0.001). "Limb-onset" ALS (lALS) was associated with a better QoL than "bulbar-onset" ALS (bALS) (mean ALSAQ-5 total score 55.46 versus 60.99, p = 0.040). Moreover, with the ALSFRS-R as a covariate, using a mobility aid (ß = -7.60, p = 0.001), being tracheostomized (ß = -14.80, p = 0.004) and using non-invasive ventilation (ß = -5.71, p = 0.030) were associated with an improved QoL, compared to those at the same disease stage who did not use these aids. In contrast, antidepressant intake (ß = 5.95, p = 0.007), and increasing age (ß = 0.18, p = 0.023) were predictors of worse QoL. Our results showed that the ALSAQ-5 was better-suited for ALS patients than the EQ-5D-5L. Further, the early and symptom-specific clinical management and supply of assistive devices can significantly improve the individual HRQoL of ALS patients. Appropriate QoL questionnaires are needed to monitor the impact of treatment to provide the best possible and individualized care.

Treat Iron-Related Childhood-Onset Neurodegeneration (TIRCON)-An International Network on Care and Research for Patients With Neurodegeneration With Brain Iron Accumulation (NBIA).

In order to improve clinical care, coordinate research activities and raise awareness for the ultra-orphan Neurodegeneration with Brain Iron Accumulation (NBIA) disorders, a group of NBIA clinicians and researchers, industry partners and patient advocacies from six European countries, Canada and the US joined forces in 2010 to set-up the collaborative initiative TIRCON (Treat Iron-Related Childhood-Onset Neurodegeneration). As a research project, TIRCON received funding in the 7th Framework Programme (FP7) of the European Union (EU) from 2011 to 2015. After successful and timely completion of the initial FP7 project, funding and donations from industry and patient organizations have sustained the further development of TIRCON's dedicated clinical research infrastructure and its governance architecture, as well as the ongoing efforts undertaken in the NBIA community to establish a network of care. From the beginning, the University Hospital of the Ludwig-Maximilians-University in Munich, Germany has been coordinating the TIRCON initiative. It consists of 8 work packages, of which the first double-blind, placebo-controlled, randomized, multi-site clinical trial in NBIA (deferiprone in PKAN, completed) and a global patient registry and biobank, currently comprising baseline and follow-up data of > 400 NBIA patients have gained particular importance. Here we describe TIRCON's history with all the challenges and achievements in diagnosing and treating NBIA. Today, TIRCON lays the ground for future clinical care and research. In these times, it may also serve as a good example of well-directed governmental funding and fruitful international scientific collaboration.

PKAN neurodegeneration and residual PANK2 activities in patient erythrocytes.

OBJECTIVE: Pantothenate kinase 2-associated neurodegeneration (PKAN) is a rare neurodegenerative disease caused by mutations in the pantothenate kinase 2 (PANK2) gene. PKAN is associated with iron deposition in the basal ganglia and, occasionally, with the occurrence of misshaped erythrocytes (acanthocytes). The aim of this study was to assess residual activity of PANK2 in erythrocytes of PKAN patients and to correlate these data with the type of PANK2 mutations and the progression of neurodegeneration. METHODS: Residual PANK2 activities in erythrocytes of 14 PKAN patients and 14 related carriers were assessed by a radiometric assay. Clinical data on neurodegeneration included the Barry-Albright Dystonia Scale (BAD-Scale) besides further general patient features. A molecular visualization and analysis program was used to rationalize the influence of the PKAN causing mutations on a molecular level. RESULTS: Erythrocytes of PKAN patients had markedly reduced or no PANK2 activity. However, patients with at least one allele of the c.1583C > T (T528M) or the c.833G > T (R278L) variant exhibited 12-56% of residual PANK2 activity. In line, molecular modeling indicated only minor effects on enzyme structure for these point mutations. On average, these patients with c.1583C > T or c.833G > T variant had lower BAD scores corresponding to lower symptom severity than patients with other PANK2 point mutations. INTERPRETATION: Residual erythrocyte PANK2 activity could be a predictor for the progression of neurodegeneration in PKAN patients. Erythrocytes are an interesting patient-derived cell system with still underestimated diagnostic potential.

Delineating MT-ATP6-associated disease: From isolated neuropathy to early onset neurodegeneration.

OBJECTIVE: To delineate the phenotypic and genotypic spectrum in carriers of mitochondrial MT-ATP6 mutations in a large international cohort. METHODS: We analyzed in detail the clinical, genetical, and neuroimaging data from 132 mutation carriers from national registries and local databases from Europe, USA, Japan, and China. RESULTS: We identified 113 clinically affected and 19 asymptomatic individuals with a known pathogenic MT-ATP6 mutation. The most frequent mutations were m.8993 T > G (53/132, 40%), m.8993 T > C (30/132, 23%), m.9176 T > C (30/132, 23%), and m.9185 T > C (12/132, 9%). The degree of heteroplasmy was high both in affected (mean 95%, range 20%-100%) and unaffected individuals (mean 73%, range 20%-100%). Age at onset ranged from prenatal to the age of 75 years, but almost half of the patients (49/103, 48%) became symptomatic before their first birthday. In 28 deceased patients, the median age of death was 14 months. The most frequent symptoms were ataxia (81%), cognitive dysfunction (49%), neuropathy (48%), seizures (37%), and retinopathy (14%). A diagnosis of Leigh syndrome was made in 55% of patients, whereas the classic syndrome of neuropathy, ataxia, and retinitis pigmentosa (NARP) was rare (8%). CONCLUSIONS: In this currently largest series of patients with mitochondrial MT-ATP6 mutations, the phenotypic spectrum ranged from asymptomatic to early onset multisystemic neurodegeneration. The degree of mutation heteroplasmy did not reliably predict disease severity. Leigh syndrome was found in more than half of the patients, whereas classic NARP syndrome was rare. Oligosymptomatic presentations were rather frequent in adult-onset patients, indicating the need to include MT-ATP6 mutations in the differential diagnosis of both ataxias and neuropathies.

Safety and efficacy of deferiprone for pantothenate kinase-associated neurodegeneration: a randomised, double-blind, controlled trial and an open-label extension study.

BACKGROUND: Pantothenate kinase-associated neurodegeneration (PKAN) is a rare genetic disorder characterised by progressive generalised dystonia and brain iron accumulation. We assessed whether the iron chelator deferiprone can reduce brain iron and slow disease progression. METHODS: We did an 18-month, randomised, double-blind, placebo-controlled trial (TIRCON2012V1), followed by a pre-planned 18-month, open-label extension study, in patients with PKAN in four hospitals in Germany, Italy, England, and the USA. Patients aged 4 years or older with a genetically confirmed diagnosis of PKAN, a total score of at least 3 points on the Barry-Albright Dystonia (BAD) scale, and no evidence of iron deficiency, neutropenia, or abnormal hepatic or renal function, were randomly allocated (2:1) to receive an oral solution of either deferiprone (30 mg/kg per day divided into two equal doses) or placebo for 18 months. Randomisation was done with a centralised computer random number generator and with stratification based on age group at onset of symptoms. Patients were allocated to groups by a randomisation team not masked for study intervention that was independent of the study. Patients, caregivers, and investigators were masked to treatment allocation. Co-primary endpoints were the change from baseline to month 18 in the total score on the BAD scale (which measures severity of dystonia in eight body regions) and the score at month 18 on the Patient Global Impression of Improvement (PGI-I) scale, which is a patient-reported interpretation of symptom improvement. Efficacy analyses were done on all patients who received at least one dose of the study drug and who provided a baseline and at least one post-baseline efficacy assessment. Safety analyses were done for all patients who received at least one dose of the study drug. Patients who completed the randomised trial were eligible to enrol in a single-arm, open-label extension study of another 18 months, in which all participants received deferiprone with the same regimen as the main study. The trial was registered on ClinicalTrials.gov, number NCT01741532, and EudraCT, number 2012-000845-11. FINDINGS: Following a screening of 100 prospective patients, 88 were randomly assigned to the deferiprone group (n=58) or placebo group (n=30) between Dec 13, 2012, and April 21, 2015. Of these, 76 patients completed the study (49 in the deferiprone group and 27 in the placebo group). After 18 months, the BAD score worsened by a mean of 2·48 points (SE 0·63) in patients in the deferiprone group versus 3·99 points (0·82) for patients in the control group (difference -1·51 points, 95% CI -3·19 to 0·16, p=0·076). No subjective change was detected as assessed by the PGI-I scale: mean scores at month 18 were 4·6 points (SE 0·3) for patients in the deferiprone group versus 4·7 points (0·4) for those in the placebo group (p=0·728). In the extension study, patients continuing deferiprone retained a similar rate of disease progression as assessed by the BAD scale (1·9 points [0·5] in the first 18 months vs 1·4 points [0·4] in the second 18 months, p=0·268), whereas progression in patients switching from placebo to deferiprone seemed to slow (4·4 points [1·1] vs 1·4 points [0·9], p=0·021). Patients did not detect a change in their condition after the additional 18 months of treatment as assessed by the PGI-I scale, with mean scores of 4·1 points [0·2] in the deferiprone-deferiprone group and of 4·7 points [0·3] in the placebo-deferiprone group. Deferiprone was well tolerated and adverse events were similar between the treatment groups, except for anaemia, which was seen in 12 (21%) of 58 patients in the deferiprone group, but was not seen in any patients in the placebo group. No patient discontinued therapy because of anaemia, and three discontinued because of moderate neutropenia. There was one death in each group of the extension study and both were secondary to aspiration. Neither of these events was considered related to deferiprone use. INTERPRETATION: Deferiprone was well tolerated, achieved target engagement (lowering of iron in the basal ganglia), and seemed to somewhat slow disease progression at 18 months, although not significantly, as assessed by the BAD scale. These findings were corroborated by the results of an additional 18 months of treatment in the extension study. The subjective PGI-I scale was largely unchanged during both study periods, indicating that might not be an adequate tool for assessment of disease progression in patients with PKAN. Our trial provides the first indication of a decrease in disease progression in patients with neurodegeneration with brain iron accumulation. The extensive information collected and long follow-up of patients in the trial will improve the definition of appropriate endpoints, increase the understanding of the natural history, and thus help to shape the design of future trials in this ultra-orphan disease. FUNDING: European Commission, US Food and Drug Administration, and ApoPharma Inc.

Expanded phenotypic spectrum of the m.8344A>G "MERRF" mutation: data from the German mitoNET registry.

The m.8344A>G mutation in the MTTK gene, which encodes the mitochondrial transfer RNA for lysine, is traditionally associated with myoclonic epilepsy and ragged-red fibres (MERRF), a multisystemic mitochondrial disease that is characterised by myoclonus, seizures, cerebellar ataxia, and mitochondrial myopathy with ragged-red fibres. We studied the clinical and paraclinical phenotype of 34 patients with the m.8344A>G mutation, mainly derived from the nationwide mitoREGISTER, the multicentric registry of the German network for mitochondrial disorders (mitoNET). Mean age at symptom onset was 24.5 years ±10.9 (6-48 years) with adult onset in 75 % of the patients. In our cohort, the canonical features seizures, myoclonus, cerebellar ataxia and ragged-red fibres that are traditionally associated with MERRF, occurred in only 61, 59, 70, and 63 % of the patients, respectively. In contrast, other features such as hearing impairment were even more frequently present (72 %). Other common features in our cohort were migraine (52 %), psychiatric disorders (54 %), respiratory dysfunction (45 %), gastrointestinal symptoms (38 %), dysarthria (36 %), and dysphagia (35 %). Brain MRI revealed cerebral and/or cerebellar atrophy in 43 % of our patients. There was no correlation between the heteroplasmy level in blood and age at onset or clinical phenotype. Our findings further broaden the clinical spectrum of the m.8344A>G mutation, document the large clinical variability between carriers of the same mutation, even within families and indicate an overlap of the phenotype with other mitochondrial DNA-associated syndromes.

Deficiency of ECHS1 causes mitochondrial encephalopathy with cardiac involvement.

OBJECTIVE: Short-chain enoyl-CoA hydratase (ECHS1) is a multifunctional mitochondrial matrix enzyme that is involved in the oxidation of fatty acids and essential amino acids such as valine. Here, we describe the broad phenotypic spectrum and pathobiochemistry of individuals with autosomal-recessive ECHS1 deficiency. METHODS: Using exome sequencing, we identified ten unrelated individuals carrying compound heterozygous or homozygous mutations in ECHS1. Functional investigations in patient-derived fibroblast cell lines included immunoblotting, enzyme activity measurement, and a palmitate loading assay. RESULTS: Patients showed a heterogeneous phenotype with disease onset in the first year of life and course ranging from neonatal death to survival into adulthood. The most prominent clinical features were encephalopathy (10/10), deafness (9/9), epilepsy (6/9), optic atrophy (6/10), and cardiomyopathy (4/10). Serum lactate was elevated and brain magnetic resonance imaging showed white matter changes or a Leigh-like pattern resembling disorders of mitochondrial energy metabolism. Analysis of patients' fibroblast cell lines (6/10) provided further evidence for the pathogenicity of the respective mutations by showing reduced ECHS1 protein levels and reduced 2-enoyl-CoA hydratase activity. While serum acylcarnitine profiles were largely normal, in vitro palmitate loading of patient fibroblasts revealed increased butyrylcarnitine, unmasking the functional defect in mitochondrial ß-oxidation of short-chain fatty acids. Urinary excretion of 2-methyl-2,3-dihydroxybutyrate - a potential derivative of acryloyl-CoA in the valine catabolic pathway - was significantly increased, indicating impaired valine oxidation. INTERPRETATION: In conclusion, we define the phenotypic spectrum of a new syndrome caused by ECHS1 deficiency. We speculate that both the ß-oxidation defect and the block in l-valine metabolism, with accumulation of toxic methacrylyl-CoA and acryloyl-CoA, contribute to the disorder that may be amenable to metabolic treatment approaches.

Safety and tolerability of carbamylated erythropoietin in Friedreich's ataxia.

BACKGROUND: Erythropoietin (EPO) derivatives have been found to increase frataxin levels in Friedreich's ataxia (FRDA) in vitro. This multicenter, double-blind, placebo-controlled, phase II clinical trial aimed to evaluate the safety and tolerability of Lu AA24493 (carbamylated EPO; CEPO). METHODS: Thirty-six ambulatory FRDA patients harboring >400 GAA repeats were 2:1 randomly assigned to either CEPO in a fixed dose (325 µg thrice-weekly) or placebo. Safety and tolerability were assessed up to 103 days after baseline. Secondary outcome measures of efficacy (exploration of biomarkers and ataxia ratings) were performed up to 43 days after baseline. RESULTS: All patients received six doses of study medication. Adverse events were equally distributed between CEPO and placebo. There was no evidence for immunogenicity of CEPO after multiple dosing. Biomarkers, such as frataxin, or measures for oxidative stress and ataxia ratings did not differ between CEPO and placebo. CONCLUSION: CEPO was safe and well tolerated in a 2-week treatment phase. Secondary outcome measures remained without apparent difference between CEPO and placebo.

Effects of idebenone on color vision in patients with leber hereditary optic neuropathy.

BACKGROUND: The authors investigated the correlation of protan and tritan color vision with disease characteristics in Leber hereditary optic neuropathy (LHON). The authors also characterized the therapeutic potential of idebenone in protecting patients from developing dyschromatopsia in LHON. METHODS: Color contrast data of 39 LHON patients participating in a randomized, double-blind placebo-controlled intervention study were evaluated. Patients reported disease onset <5 years before enrolment and were genetically confirmed. Protan and tritan color contrast sensitivity was measured using a computer graphics method in patients receiving idebenone (Catena; 900 mg/d; N = 28) or placebo (N = 11) for 6 months. RESULTS: Mean age of patients was 28.1 years, 87.2% were men, 76.9% carried the m11778G>A mutation, and mean duration since onset was 2 years. Assessing protan and tritan color vision at baseline revealed a high degree of color confusion even in young patients (<25 years) and with a short history of disease (<1 year). Treatment with idebenone improved tritan color vision compared with placebo (P = 0.008 at week 24); a similar trend was seen for protan. The effect of idebenone was most prominent in patients with discordant visual acuity (interocular difference of logMAR >0.2). In this subgroup, the treatment effect at week 24 was 20.4% (P = 0.005) in favor of idebenone for the tritan color domain and 13.5% (P = 0.067) for the protan domain. CONCLUSION: This study confirms that protan and tritan color confusion is an early symptom in LHON. Treatment with idebenone can protect from loss of color vision, particularly in patients who are at imminent risk of further vision loss.

An international registry for neurodegeneration with brain iron accumulation.

We report the development of an international registry for Neurodegeneration with Brain Iron Accumulation (NBIA), in the context of TIRCON (Treat Iron-Related Childhood-Onset Neurodegeneration), an EU-FP7 - funded project. This registry aims to combine scattered resources, integrate clinical and scientific knowledge, and generate a rich source for future research studies. This paper describes the content, architecture and future utility of the registry with the intent to capture as many NBIA patients as possible and to offer comprehensive information to the international scientific community.