Oral maintenance clinical trial with miglustat for type I Gaucher disease: switch from or combination with intravenous enzyme replacement

Therapeutic applications of carbohydrate-based compounds: a sweet solution for medical advancement

Carbohydrates, one of the most abundant biomolecules found in nature, have been seen traditionally as a dietary component of foods. Recent findings, however, have unveiled their medicinal potential in the form of carbohydrates-derived drugs. Their remarkable structural diversity, high optical purity, bioavailability, low toxicity and the presence of multiple functional groups have positioned them as a valuable scaffold and an exciting frontier in contemporary therapeutics. At present, more than 170 carbohydrates-based therapeutics have been granted approval by varying regulatory agencies such as United States Food and Drug Administration (FDA), Japan Pharmaceuticals and Medical Devices Agency (PMDA), Chinese National Medical Products Administration (NMPA), and the European Medicines Agency (EMA). This article explores an overview of the fascinating potential and impact of carbohydrate-derived compounds as pharmacological agents and drug delivery vehicles.

First-in-human single-dose study of nizubaglustat, a dual inhibitor of ceramide glucosyltransferase and non-lysosomal glucosylceramidase: Safety, tolerability, pharmacokinetics, and pharmacodynamics of single ascending and multiple doses in healthy adults

Nizubaglustat is a novel, orally available, brain penetrant, potent, and selective dual inhibitor of ceramide glucosyltranferase and non-lysosomal neutral glucosylceramidase (NLGase), which is currently under development for the treatment of subjects with neurological manifestations in primary and secondary gangliosidoses. The objectives of this first-in-human study were to evaluate the safety and tolerability, pharmacokinetics, and pharmacodynamics (PD) of single oral doses of nizubaglustat after single (1, 3, and 9 mg) and multiple oral doses (9 mg once per day (QD) over 14 days) in healthy adults. Nizubaglustat was rapidly absorbed and systemic exposure was dose-proportional. Steady-state was achieved after three days of QD multiple dosing with minimal accumulation. Renal clearance accounted for around 15% of nizubaglustat elimination. Following multiple dosing, plasma concentrations of glucosylceramide (GlcCer), lactosylceramide (LacCer), and monosialodihexosylganglioside (GM3) decreased to a nadir at Day 10. PD target engagement of GCS inhibition was shown by a median decrease from baseline of plasma concentrations of GlcCer, LacCer, and GM3 ganglioside by 70%, 50%, and 48%, respectively. NLGase inhibition was also manifested by increased concentrations of GlcCer in cerebrospinal fluid from Day 1 to Day 14. Nizubaglustat was safe and well-tolerated at all doses tested. Consistent with the high selectivity, and the absence of intestinal disaccharidases inhibition, no cases of diarrhea were reported. No decreased appetite or weight loss was noted. Only treatment-emergent adverse events with preferred terms belonging to the system organ class skin and subcutaneous disorders of mild intensity were reported as drug-related in the nizubaglustat arm, in line with the pharmacological mechanism targeting glucosylceramide metabolism. Taken together, these data support QD dosing of nizubaglustat and its ongoing development in patients with primary and secondary forms of gangliosidoses.

Patient-reported outcomes in Gaucher's disease: a systematic review

BACKGROUND

Gaucher's disease (GD), a rare condition, represents the most common lysosomal storage disorder. The cardinal manifestations of GD are fatigue, hepatosplenomegaly, anemia, thrombocytopenia, bone pain, and bone infarction, thereby culminating in a marked deterioration of patients' quality of life (QoL). Patient-reported outcomes (PROs) offer valuable insights into the impact of GD on patients' QoL and symptoms. This systematic review aimed to identify and analyze PROs and outcome measures in GD patients.

METHODS

We systematically searched PubMed, Web of Science Core Collections, EMBASE, SCOPUS, Cochrane Library, PsycINFO, Wan Fang Data, China National Knowledge Infrastructure (CNKI), and the Chinese Biomedical Literature Database (CBM). The methodological quality of the included studies was assessed using a mixed methods assessment tool.

RESULTS

A total of 33 studies were identified, encompassing 24 distinct patient-reported outcome instruments, with the most frequently employed instrument being the SF-36. The study designs included eighteen cross-sectional studies, seven pre- and post-intervention investigations, three randomized controlled trials, two cohort studies, two qualitative inquiries, and one validation study. These studies explored diverse domains such as the QoL and cardinal symptoms (e.g., fatigue, pain, bleeding, cognition, social relationships, and psychological functioning) in patients with GD. Furthermore, significant attention was directed towards the appraisal of the therapeutic benefits of various interventions in patients with GD. A novel GD-specific instrument has also been developed, which has two applied versions: a 24-item variant for routine clinical monitoring and a 17-item form for use in clinical trials.

CONCLUSION

PROs have garnered increased attention and concern in the realm of GD. Despite this progress, it is noteworthy that the instruments used to measure PROs in GD are still predominantly generic instruments. While researchers have endeavored to develop and validate a disease-specific instrument, currently the use of this instrument is limited. Owing to several challenges, including the small number of patients, heterogeneity of the disease, and cross-regional discrepancies in study findings, GD poses substantial difficulties in the measurement of QoL and development of instruments. Consequently, patients with GD require more dependable measurement instruments that accurately reflect their QoL, efficacy of treatment, and facilitate healthcare decision-making.

High-Dose Ambroxol Therapy in Type 1 Gaucher Disease Focusing on Patients with Poor Response to Enzyme Replacement Therapy or Substrate Reduction Therapy

Ambroxol hydrochloride (ABX), an oral mucolytic drug available over the counter for many years, acts as a pharmacological chaperone for mutant glucocerebrosidase, albeit at higher doses. Proof-of-concept reports have been published over the past decade on all three types of Gaucher disease (GD). Here, we assess the safety and efficacy of 12 months of 600 mg ambroxol per day in three groups of Type 1 GD patients with a suboptimal response to enzyme replacement therapy (ERT) or substrate reduction therapy (SRT), defined as platelet count < 100 × 10³/L, lumbar spine bone density T-score < -2.0, and/or LysoGb1 > 200 ng/mL, and for a group of naïve patients who had abnormal values in two of these three parameters. We enrolled 40 patients: 28 ERT- or SRT-treated, and 12 naïve. There were no severe adverse effects (AEs). There were 24 dropouts, mostly due to AEs (n = 12), all transient, and COVID-19 (n = 7). Among the 16 completers, 5 (31.2%) had a >20% increase in platelet count, 6 (37.5%) had a >0.2 increase in T-score, and 3 (18.7%) had a >20% decrease in Lyso-Gb1. This study expands the number of patients exposed to high-dose ABX, showing good safety and satisfactory efficacy, and provides an additional rationale for adding off-label ABX to the arsenal of therapies that could be offered to patients with GD1 and a suboptimal response or those unable to receive ERT or SRT.

A Systematic Review and Meta-analyses of Longitudinal Studies on Drug Treatments for Gaucher Disease

OBJECTIVE

Gaucher disease (GD) is a rare disorder linked to the absence/deficiency of glucocerebrosidase. GD can be treated by enzyme replacement therapy (ERT) and substrate reduction therapy (SRT). The aim of this systematic review (SR) is to assess the effectiveness of drugs used for GD treatment.

DATA SOURCES

Searches were conducted in PubMed and Scopus, in April 2021. The search strategies encompassed the name of the disease and of the drug treatments. Manual search was also conducted.

STUDY SELECTION AND DATA EXTRACTION

Observational and interventional longitudinal studies evaluating ERT and SRT for GD were included. Single mean meta-analyses were conducted for each drug using R.

DATA SYNTHESIS

The initial search retrieved 2246 articles after duplicates were removed. Following screening and eligibility assessment, 68 reports were included. The studies evaluated imiglucerase, velaglucerase alfa, taliglucerase alfa, miglustat, and eliglustat. The results showed that ERT is effective as a treatment in both naïve and experienced patients. Miglustat did not significantly improve blood outcomes in naïve patients and resulted in a decrease in the platelet levels of experienced patients. Eliglustat was mainly assessed for experienced patients and resulted in stable outcome values.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This extensive SR confirms the effectiveness of GD treatments in short- and long-term follow-ups.

CONCLUSIONS

The results were favorable for all ERTs and for eliglustat. Based on the assessed evidence, miglustat did not achieved expressive results. However, all evidence should be interpreted considering its limitations and does not replace well-conducted randomized trials.

Real-Life Experience with Oral Eliglustat in Patients with Gaucher Disease Previously Treated with Enzyme Replacement Therapy

Three types of enzyme replacement therapies (ERTs) and two substrate reduction therapies (SRTs) are approved for symptomatic patients with type 1 Gaucher disease (GD1). Eliglustat is the second SRT approved, yet the first to be approved as first-line therapy for any adult patients with compatible CYP2D6 metabolizer genotype. Herein we report safety and efficacy data of the first 29 patients switched from ERT to eliglustat from the Gaucher Unit at Shaare Zedek Medical Center (SZMC) between 07/2017 and 06/2022; the median (range) time on ERT was 13 (0.66-30) years, and the median (range) time on eliglustat was 7 (1-52) months. Most patients switched due to oral preference or sub-optimal response to low-dose ERT. Twelve patients stopped eliglustat after a median (range) of 4 (1-18) months; 11 due to adverse events (AEs) and one due to personal request. There were no drug-related serious AEs and no drug-related cardiac events. Most AEs were mild and transient, mainly dyspepsia. Efficacy achievements were reflected by maintaining stability. We concluded that switching from ERT to eliglustat is safe if choosing the appropriate patients. Reassuring patients to tolerate early AEs may reduce discontinuation. Following the response and compliance to therapy is important to ensure long-term efficacy.

Carbohydrate-based drugs launched during 2000-2021

Carbohydrates are fundamental molecules involved in nearly all aspects of lives, such as being involved in formating the genetic and energy materials, supporting the structure of organisms, constituting invasion and host defense systems, and forming antibiotics secondary metabolites. The naturally occurring carbohydrates and their derivatives have been extensively studied as therapeutic agents for the treatment of various diseases. During 2000 to 2021, totally 54 carbohydrate-based drugs which contain carbohydrate moities as the major structural units have been approved as drugs or diagnostic agents. Here we provide a comprehensive review on the chemical structures, activities, and clinical trial results of these carbohydrate-based drugs, which are categorized by their indications into antiviral drugs, antibacterial/antiparasitic drugs, anticancer drugs, antidiabetics drugs, cardiovascular drugs, nervous system drugs, and other agents.

Dual enzyme therapy improves adherence to chemotherapy in a patient with gaucher disease and Ewing sarcoma

This case reports concomitant use of enzyme and substrate reduction therapy to improve chemotherapy adherence in a pediatric patient diagnosed with Ewing sarcoma (ES) and type 1 Gaucher disease (GD). The 17-year-old female presented with 5 months of right knee pain with associated mass on exam. She was diagnosed with ES with pulmonary metastasis. The patient was treated with 17 alternating cycles of vincristine-doxorubicin-cyclophosphamide and ifosfamide and etoposide chemotherapy followed by tumor resection and radiation per standard protocol. As part of her staging work-up, bone marrow biopsy was performed, significant for Gaucher cells. After the second cycle of chemotherapy the patient began to experience severe delays averaging 30 days between cycles compared to 17.29 days observed in Children's Oncology Group data. Given her bone marrow biopsy findings and chemotherapy delays GD screening was obtained and the patient was diagnosed with GD following genetic confirmation. Due to delays in chemotherapy decreasing chance of remission, the patient was referred to Genetics for aggressive management with imiglucerase and eliglustat. After initiation of therapy the period between chemotherapy cycles decreased to 23 days on average, with a 21% increase in platelet count during therapy. The patient was able to complete ES therapy achieving remission. GD is associated with an increased risk of malignancy, as seen in our patient with ES. GD patients experience prolonged hematologic cytopenia during cancer treatment. Combining Enzyme and Substrate Reduction Therapies should be investigated as an option to improve chemotherapy adherence in GD patients.

Exosome- and extracellular vesicle-based approaches for the treatment of lysosomal storage disorders

Cell-generated extracellular vesicles (EVs) are being engineered as biologically-inspired vehicles for targeted delivery of therapeutic agents to treat difficult-to-manage human diseases, including lysosomal storage disorders (LSDs). Engineered EVs offer distinct advantages for targeted delivery of therapeutics compared to existing synthetic and semi-synthetic nanoscale systems, for example with regard to their biocompatibility, circulation lifetime, efficiencies in delivery of drugs and biologics to target cells, and clearance from the body. Here, we review literature related to the design and preparation of EVs as therapeutic carriers for targeted delivery and therapy of drugs and biologics with a focus on LSDs. First, we introduce the basic pathophysiology of LDSs and summarize current approaches to diagnose and treat LSDs. Second, we will provide specific details about EVs, including subtypes, biogenesis, biological properties and their potential to treat LSDs. Third, we review state-of-the-art approaches to engineer EVs for treatments of LSDs. Finally, we summarize explorative basic research and applied applications of engineered EVs for LSDs, and highlight current challenges, and new directions in developing EV-based therapies and their potential impact on clinical medicine.

Recommendations for oral treatment for adult patients with type 1 Gaucher disease

This work is a review of the scientific evidence on the oral treatment of adult patients with Gaucher disease type 1 (GD1) with a clinical guideline format according to the Agree II regulations. It describes the main differences between the two oral treatments currently available for treating this disease (miglustat and eliglustat). This review reminds us that the criteria for starting oral treatment in patients with GD1 must be assessed individually. Although miglustat and eliglustat are both glucosylceramide synthase (GCS) enzyme inhibitors, they have different mechanisms of action and pharmacological properties and should never be considered equivalent. Miglustat is indicated in patients with non-severe GD1 who cannot receive other first-line treatments, while eliglustat is indicated as first-line treatment for patients with GD1 of any severity without the need for prior stabilization with enzyme replacement therapy (ERT). It is important to emphasize that in order to start treatment with eliglustat, we must know the CYP2D6 metabolic phenotype and its association with drugs metabolized through the CYP2D6 and CYP3A4 cytochromes-or alternatively those that use P-Glycoprotein must be evaluated on an individual basis. During pregnancy, the use of eliglustat should be avoided; only ERT can be used. Unlike miglustat, whose adverse effects have limited its use, eliglustat has not only demonstrated similar efficacy to ERT but has also been shown to improve the quality of life of patients with GD1.

Gene Therapy for Lysosomal Storage Disorders: Ongoing Studies and Clinical Development

Rare monogenic disorders such as lysosomal diseases have been at the forefront in the development of novel treatments where therapeutic options are either limited or unavailable. The increasing number of successful pre-clinical and clinical studies in the last decade demonstrates that gene therapy represents a feasible option to address the unmet medical need of these patients. This article provides a comprehensive overview of the current state of the field, reviewing the most used viral gene delivery vectors in the context of lysosomal storage disorders, a selection of relevant pre-clinical studies and ongoing clinical trials within recent years.

1-Deoxynojirimycin and its Derivatives: A Mini Review of the Literature

1-Deoxynojirimycin (1-DNJ) is a naturally occurring sugar analogue with unique bioactivities. It is found in mulberry leaves and silkworms, as well as in the metabolites of certain microorganisms, including Streptomyces and Bacillus. 1-DNJ is a potent α-glucosidase inhibitor and it possesses anti-hyperglycemic, anti-obese, anti-viral and anti-tumor properties. Some derivatives of 1-DNJ, like miglitol, miglustat and migalastat, were applied clinically to treat diseases such as diabetes and lysosomal storage disorders. The present review focused on the extraction, determination, pharmacokinetics and bioactivity of 1-DNJ, as well as the clinical application of 1-DNJ derivatives.

Patient and observer reported outcome measures to evaluate health-related quality of life in inherited metabolic diseases: a scoping review

Background

Health-related Quality of Life (HrQoL) is a multidimensional measure, which has gained clinical and social relevance. Implementation of a patient-centred approach to both clinical research and care settings, has increased the recognition of patient and/or observer reported outcome measures (PROMs or ObsROMs) as informative and reliable tools for HrQoL assessment. Inherited Metabolic Diseases (IMDs) are a group of heterogeneous conditions with phenotypes ranging from mild to severe and mostly lacking effective therapies. Consequently, HrQoL evaluation is particularly relevant.

Objectives

We aimed to: (1) identify patient and/or caregiver-reported HrQoL instruments used among IMDs; (2) identify the main results of the application of each HrQoL tool and (3) evaluate the main limitations of HrQoL instruments and study design/methodology in IMDs.

Methods

A scoping review was conducted using methods outlined by Arksey and O’Malley. Additionally, we critically analysed each article to identify the HrQoL study drawbacks.

Results

Of the 1954 studies identified, 131 addressed HrQoL of IMDs patients using PROMs and/or ObsROMs, both in observational or interventional studies. In total, we identified 32 HrQoL instruments destined to self- or proxy-completion; only 2% were disease-specific. Multiple tools (both generic and disease-specific) proved to be responsive to changes in HrQoL; the SF-36 and PedsQL questionnaires were the most frequently used in the adult and pediatric populations, respectively. Furthermore, proxy data often demonstrated to be a reliable approach complementing self-reported HrQoL scores. Nevertheless, numerous limitations were identified especially due to the rarity of these conditions.

Conclusions

HrQoL is still not frequently assessed in IMDs. However, our results show successful examples of the use of patient-reported HrQoL instruments in this field. The importance of HrQoL measurement for clinical research and therapy development, incites to further research in HrQoL PROMs’ and ObsROMs’ creation and validation in IMDs.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0953-9) contains supplementary material, which is available to authorized users.

Combined miglustat and enzyme replacement therapy in two patients with type 1 Gaucher disease: two case reports

BACKGROUND

Intravenous enzyme replacement therapy is a first-line therapy for Gaucher disease type 1, and substrate reduction therapy represents an oral treatment alternative. Both enzyme replacement therapy and substrate reduction therapy are generally used as monotherapies in Gaucher disease. However, one randomized study and several case reports have described combination therapy over short time periods.

CASE PRESENTATION

We report two female Gaucher disease type 1 patients of mainly Anglo-Saxon descent, where combined enzyme replacement therapy and miglustat substrate reduction therapy were administered to overcome refractory clinical symptoms. The first patient was diagnosed at age 17 and developed Gaucher disease-related bone manifestations that worsened despite starting imiglucerase enzyme replacement therapy. After switching to miglustat substrate reduction therapy, her bone symptoms improved, but she developed tremors and eventually switched back to enzyme replacement therapy. Miglustat was later recommenced in combination with ongoing enzyme replacement therapy due to continued bone pain, and her bone symptoms improved along with maintained visceral manifestations. Enzyme replacement therapy was subsequently tapered off and the patient has since been successfully maintained on miglustat. The second patient was diagnosed aged 3, and commenced imiglucerase enzyme replacement therapy aged 15. After 9 years on enzyme replacement therapy she switched to miglustat substrate reduction therapy and her core symptoms were maintained/stable for 3 years. Imiglucerase enzyme replacement therapy was later added as a boost to therapy and her symptoms were subsequently maintained over a 2.3-year period. However, miglustat was discontinued due to her relocation, necessitating an increase in enzyme replacement therapy dose. Overall, both patients benefited from combination therapy.

CONCLUSION

While the majority of Gaucher disease type 1 patients will not need treatment with both substrate reduction therapy and enzyme replacement therapy, the current case reports demonstrate that judicious use of combination therapy may be of benefit in some cases.

Attitudes of Individuals with Gaucher Disease toward Substrate Reduction Therapies

Type 1 Gaucher disease (GD) is the most common lysosomal storage disorder. Previously, treatment for GD was limited to intravenous enzyme replacement therapies (ERTs). More recently, oral substrate reduction therapies (SRTs) were approved for treatment of GD. Although both therapies alleviate disease symptoms, attitudes toward SRTs and patient perceptions of health while using SRT have not been well established. Electronic surveys were administered to adults with GD and asked about treatment history, attitudes toward SRTs, and perception of health while using SRTs as compared to ERTs, if applicable to the participant. ERT users that were offered treatment with SRTs cited potential side effects, wanting more research on SRTs, and satisfaction with their current treatment regimen as reasons for declining SRTs. SRT users expressed convenience and less invasiveness as reasons for choosing SRTs. Additionally, those using SRTs most often perceived their health to be similar to when they previously used ERT. Participant responses illustrate that attitudes toward SRTs can be variable and that one particular treatment may not be ideal for all patients with GD depending on individual perceptions of factors such as convenience, invasiveness, or side effects. Thus, individuals with GD should be counseled adequately by healthcare providers about both ERTs and SRTs for treatment of GD now that SRTs are clinically available.

Taliglucerase alfa in Gaucher disease: Description of a Brazilian experience

We evaluated retrospectively, efficacy and safety of taliglucerase alfa for Gaucher disease in a Brazilian population. Thirteen patients were included for efficacy analysis only one of them naïve to enzyme replacement therapy. All the parameters evaluated remained stable throughout treatment (mean duration 3,5years). Only three patients (out of 35) had to discontinue treatment due to a serious adverse event. In conclusion, treatment with taliglucerase alfa was found to be safe and efficient.

Successful switch from enzyme replacement therapy to miglustat in an adult patient with type 1 Gaucher disease: a case report

Background

Gaucher disease is one of the most common lipid-storage disorders, affecting approximately 1 in 75,000 births. Enzyme replacement therapy with recombinant glucocerebrosidase is currently considered the first-line treatment choice for patients with symptomatic Gaucher disease type 1. Oral substrate reduction therapy is generally considered a second-line treatment option for adult patients with mild to moderate Gaucher disease type 1 who are unable or unwilling to receive lifelong intravenous enzyme infusions. The efficacy and safety of the oral substrate reduction therapy miglustat (Zavesca®) in patients with Gaucher disease type 1 have been established in both short-term clinical trials and long-term, open-label extension studies. Published data indicate that miglustat can be used as maintenance therapy in patients with stable Gaucher disease type 1 switched from previous enzyme replacement therapy.

Case presentation

We report a case of a 44-year-old Caucasian man with Gaucher disease type 1 who was initially treated with enzyme replacement therapy but, owing to repeated cutaneous allergic reactions, had to be switched to miglustat after several attempts with enzyme replacement therapy. Despite many attempts, desensitization treatment did not result in improved toleration of imiglucerase infusions, and the patient became unwilling to continue with any intravenous enzyme replacement therapy. He subsequently agreed to switch to oral substrate reduction therapy with miglustat 100 mg twice daily titrated up to 100 mg three times daily over a short period. Long-term miglustat treatment maintained both hemoglobin and platelet levels within acceptable ranges over 8 years. The patient’s spleen volume decreased, his plasma chitotriosidase levels stayed at reduced levels, and his bone mineral density findings have remained stable throughout follow-up. The patient’s quality of life has remained satisfactory. Miglustat showed good gastrointestinal tolerability in this patient, and no adverse events have been reported.

Conclusions

Oral miglustat therapy proved to be a valid alternative treatment to intravenous enzyme replacement therapy for long-term maintenance in this patient with Gaucher disease type 1, who showed persistent allergic intolerance to imiglucerase infusions. This report exemplifies the type of patient with Gaucher disease type 1 who can benefit from switching from enzyme replacement therapy to substrate reduction therapy.

Limited responsiveness related to the minimal important difference of patient-reported outcomes in rare diseases

OBJECTIVES

To explore the responsiveness of patient-reported outcomes (PROs) in interventional studies involving patients with rare lysosomal storage diseases (LSDs).

STUDY DESIGN AND SETTING

We searched eight databases for experimental and nonexperimental studies. Pairs of trained reviewers independently screened articles and subsequently extracted data from the eligible studies. Among studies with 10 or more patients using a valid PRO, we assessed the responsiveness of PROs based on a reanalysis of the data using minimal important difference estimates. Our analyses focused on statistically significant within-group differences in PROs for observational studies or the statistically significant between-group differences in PRO scores for controlled studies.

RESULTS

Of 2,679 unique records, 62 interventional studies addressing patients with Fabry (55%), Gaucher (19%), Pompe (16%), and mucopolysaccharidoses (11%) proved eligible. The most frequently used PROs were the Short-Form-36 (25 studies), Brief Pain Inventory (20 studies), EuroQoL-5D (9 studies), and the Fatigue Severity Scale (6 studies). Observational studies suggest that PROs sometimes detect significant within-group changes when present. Randomized trials raise questions regarding the responsiveness of PROs to small differences between groups.

CONCLUSIONS

Most studies have relied on generic PROs to evaluate quality of life and symptoms in patients with rare LSDs. PROs appear more responsive in observational studies than randomized trials.

Biochemical response to substrate reduction therapy versus enzyme replacement therapy in Gaucher disease type 1 patients

Background

We retrospectively compared biochemical responses in type 1 Gaucher disease patients to treatment with glycosphingolipid synthesis inhibitors miglustat and eliglustat and ERT.

Methods

Seventeen GD1 patients were included (n = 6 eliglustat, (two switched from ERT), n = 9 miglustat (seven switchers), n = 4 ERT (median dose 60U/kg/m). Plasma protein markers reflecting disease burden (chitotriosidase, CCL18) and lipids reflecting substrate accumulation (glucosylsphingosine, glucosylceramide) were determined. Also, liver and spleen volumes, hemoglobin, platelets, and fat fraction were measured.

Results

In patients naïve to treatment, chitotriosidase, CCL18 and glucosylsphingosine decreased comparably upon eliglustat and ERT treatment, while the response to miglustat was less. After 2 years, median decrease of chitotriosidase was 89 % (range 77–98), 88 % (78–92) and 37 % (29–46) for eliglustat, ERT and miglustat naïve patients respectively; decrease of CCL18 was 73 % (63–78), 54 % (43–86), and 10 % (3–18); decrease of glucosylsphingosine was 86 % (78–93), 78 % (65–91), 48 % (46–50). Plasma glucosylceramide in eliglustat treated patients (n = 4) reached values below the normal range (n = 20 healthy controls). Biochemical markers decreased or stabilized in switchers from ERT to eliglustat (n = 2), but less in miglustat switchers (n = 7). Clinical parameters responded comparably upon eliglustat and ERT treatment.

Conclusions

Our explorative study provides evidence that biochemical markers respond comparably in patients receiving eliglustat treatment and ERT, while the corresponding response to miglustat treatment is less.

Diagnostic workup and management of patients with suspected Niemann-Pick type C disease

Niemann-Pick type C (NP-C) disease is a neurovisceral disorder caused by mutations in the NPC1 and NPC2 genes. It is characterized by lysosomal storage of a broad range of lipids as a result of abnormal intracellular lipid trafficking. Typically patients develop neurodegeneration; however, the speed of disease progression is variable. The exact functions of NPC1 and NPC2 proteins have not been determined and therefore the molecular pathophysiology of NP-C is still not clearly understood. Due to the disease's rarity and clinical heterogeneity, delays from symptom onset to diagnosis and treatment initiation are common. Current therapeutic approaches focus on multidisciplinary symptom control and deceleration (rather than reversal) of disease progression. Thus identification of cases at early stages of disease is particularly important. Recent advances in genetic and biochemical testing have resulted in the generation of relatively non-invasive, quick and cost-effective laboratory assays that are highly sensitive and specific and have the capacity to enhance the clinicians' ability to reach a diagnosis earlier. Miglustat is a compound recently licensed in many countries for the treatment of NP-C that has been shown to decelerate neurological regression, whereas many other promising drugs are currently being trialled in preclinical models or human studies. This review summarizes key clinical, genetic and biochemical features of NP-C, suggests a simple diagnostic investigation strategy and gives an overview of available therapeutic options as well as potential novel treatments currently under development.

Observational cohort study of the natural history of Niemann-Pick disease type C in the UK: a 5-year update from the UK clinical database

BACKGROUND

Niemann-Pick disease type C (NP-C) is a rare neurovisceral lipid storage disorder characterised by progressive, disabling neurological symptoms and premature death in most patients. During the last decade, national cohort studies have accrued a great deal of data on the symptomatology and natural history of NP-C.

METHODS

In an observational cohort study, we present a substantial update based on the clinical presentation and follow-up of all known UK-based patients with a confirmed diagnosis of NP-C who have been tracked on an electronic database at the Department of Genetic Medicine, University of Manchester, UK. Patients were stratified according to accepted age-at-neurological-onset categories. Data on patients' clinical signs and symptoms, medical history and genetic studies are summarised using descriptive methods.

RESULTS

A total of 146 patients with NP-C were included, representing the full known UK NP-C cohort, as observed from database information between 1999 and the end of 2011: 72 patients (49 %) were alive at the end of the observation period. Among a total of 116 patients (79 %) who possessed at least one identified, disease-causing NP-C gene mutation, 114 (98 %) had NPC1 and two (2 %) had NPC2 mutations. Overall, 53/194 (27 %) identified mutations were novel. Six patients (4 %) had an early, non-neurological neonatal onset form of NP-C. The numbers (%) of patients with accepted age-at-neurological onset forms were: 8 (5 %) early-infantile onset, 51 (35 %) late-infantile onset, 42 (29 %) juvenile onset, and 25 (17 %) adolescent/adult onset. Fourteen patients diagnosed based on visceral symptoms and/or sibling history, confirmed in most cases by genetic analysis, did not have any neurological manifestations at last follow up (11 patients with mean [SD] age at last follow up 2.5 [1.8] years: 3 with mean [SD] age at death 20.8 [15.9] years). A total of 51 patients (35 %) received miglustat therapy. The mean (SD) overall treatment duration up to the end of the observation period was 2.6 (2.3) years.

CONCLUSIONS

This UK cohort is the largest national NP-C cohort reported to date, and confirms the wide phenotypic variability of the disease, as reported in other countries. Further analyses are required to assess the impact of miglustat therapy on neurological disease progression.

Gaucher Disease: Clinical, Biological and Therapeutic Aspects

We present a brief review of Gaucher disease (GD), the most common lysosomal storage disease. GD is a rare autosomal recessive disorder characterized by the defective function of the catabolic enzyme β-glucocerebrosidase (GBA), leading to an accumulation of its substrate, glucocerebroside. Clinical signs and symptoms include neurological dysfunctions, bone infarcts and malformations, hepatosplenomegaly and hypersplenism leading to anemia, neutropenia and thrombocytopenia. Enzyme replacement therapy with recombinant GBA is the mainstay of treatment for GD, which became the first successfully managed lipid storage disease. Future treatments may include oral enzyme replacement and/or gene therapy interventions.

A double-blind, randomized, placebo-controlled trial studying the effects of Saccharomyces boulardii on the gastrointestinal tolerability, safety, and pharmacokinetics of miglustat

Background

Gastrointestinal (GI) disturbances such as diarrhea and flatulence are the most frequent adverse effects associated with miglustat therapy in type 1 Gaucher disease (GD1) and Niemann-Pick disease type C (NP-C), and the most common recorded reason for stopping treatment during clinical trials and in clinical practice settings. Miglustat-related GI disturbances are thought to arise from the inhibition of intestinal disaccharidases, mainly sucrase isomaltase. We report the effects of a co-administered dietary probiotic, S. boulardii, on the GI tolerability of miglustat in healthy adult subjects.

Methods

In a double-blind, placebo-controlled, two-period, two-treatment cross-over trial, healthy adult male and female subjects were randomly allocated to treatment sequences, A–B and B–A (treatment A - miglustat 100 mg t.i.d. + placebo; treatment B - miglustat 100 mg t.i.d. + S. boulardii [500 mg, b.i.d.]). GI tolerability data were collected in patient diaries. The primary endpoint was the total number of ‘diarrhea days’ (≥3 loose stools within a 24-h period meeting Bristol Stool Scores [BSS] 6–7) based on WHO criteria. Secondary endpoints comprised numerous other diarrhea and GI tolerability indices.

Results

Twenty-one subjects received randomized therapy in each treatment sequence (total N = 42), and overall, 37 (88 %) subjects completed the study. The total number of diarrhea days was <1.5 for both treatment sequences, and approximately 60 % of subjects did not experience diarrhea during either treatment period. The mean (SD) number of diarrhea days was lower with miglustat + S. boulardii (0.8 [2.4] days) than with miglustat + placebo (1.3 [2.4] days), but the paired treatment difference was not statistically significant (−0.5 [2.4] days; p = 0.159). However, a significant treatment difference (−0.7 [1.9]; p < 0.05) was identified after post hoc exclusion of a clear outlier who had a very high number of diarrhea days (n = 13) and inconsistent GI tolerability reporting. The incidence of the GI AEs was higher with miglustat + placebo (82 %) than with miglustat + S. boulardii (73 %). There were no between-treatment differences in miglustat pharmacokinetics.

Conclusions

Although the primary endpoint was not met, the results of the post-hoc analysis suggest that co-administration of miglustat with S. boulardii might improve GI tolerability.

Eliglustat compared with imiglucerase in patients with Gaucher's disease type 1 stabilised on enzyme replacement therapy: a phase 3, randomised, open-label, non-inferiority trial

BACKGROUND

The mainstay of treatment for Gaucher's disease type 1 is alternate-week infusion of enzyme replacement therapy (ERT). We investigated whether patients stable on such treatment would remain so after switching to oral eliglustat, a selective inhibitor of glucosylceramide synthase.

METHODS

In this phase 3, randomised, multinational, open-label, non-inferiority trial, we enrolled adults (aged ≥18 years) who had received ERT for 3 years or more for Gaucher's disease. Patients were randomly allocated 2:1 at 39 clinics (stratified by ERT dose; block sizes of four; computer-generated centrally) to receive either oral eliglustat or imiglucerase infusions for 12 months. Participants and investigators were aware of treatment assignment, but the central reader who assessed organ volumes was masked. The composite primary efficacy endpoint was percentage of patients whose haematological variables and organ volumes remained stable for 12 months (ie, haemoglobin decrease not more than 15 g/L, platelet count decrease not more than 25%, spleen volume increase not more than 25%, and liver volume increase not more than 20%, in multiples of normal from baseline). The non-inferiority margin was 25% for eliglustat relative to imiglucerase, assessed in all patients who completed 12 months of treatment. This trial is registered with ClinicalTrials.gov, number NCT00943111, and EudraCT, number 2008-005223-28.

FINDINGS

Between Sept 15, 2009, and Nov 9, 2011, we randomly allocated 106 (66%) patients to eliglustat and 54 (34%) to imiglucerase. In the per-protocol population, 84 (85%) of 99 patients who completed eliglustat treatment and 44 (94%) of 47 patients who completed imiglucerase treatment met the composite primary endpoint (between-group difference -8·8%; 95% CI -17·6 to 4·2). The lower bound of the 95% CI of -17·6% was within the prespecified threshold for non-inferiority. Dropouts occurred due to palpitations (one patient on eliglustat), myocardial infarction (one patient on eliglustat), and psychotic disorder (one patient on imiglucerase). No deaths occurred. 97 (92%) of 106 patients in the eliglustat group had treatment-emergent adverse events, as did 42 (79%) of 53 in the imiglucerase group (mostly mild or moderate in severity).

INTERPRETATION

Oral eliglustat maintained haematological and organ volume stability in adults with Gaucher's disease type 1 already controlled by intravenous ERT and could be a useful therapeutic option.

FUNDING

Genzyme, a Sanofi company.

Enzyme replacement and substrate reduction therapy for Gaucher disease

BACKGROUND

Gaucher disease, a rare disorder, is caused by inherited deficiency of the enzyme glucocerebrosidase. It is unique among the ultra-orphan disorders in that four treatments are currently approved by various regulatory authorities for use in routine clinical practice. Hitherto, because of the relatively few people affected worldwide, many of whom started therapy during a prolonged period when there were essentially no alternatives to imiglucerase, these treatments have not been systematically evaluated in studies such as randomized controlled trials now considered necessary to generate the highest level of clinical evidence.

OBJECTIVES

To summarize all available randomized controlled study data on the efficacy and safety of enzyme replacement therapies and substrate reduction therapy for treating Gaucher disease.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Inborn Errors of Metabolism Trials Register. Additional searches were conducted on ClinicalTrials.gov for any ongoing studies with potential interim results, and through PubMed. We also searched the reference lists of relevant articles and reviews.Date of last search: 07 August 2014.

SELECTION CRITERIA

All randomized and quasi-randomized controlled studies (including open-label studies and cross-over studies) assessing enzyme replacement therapy or substrate reduction therapy, or both, in all types of Gaucher disease were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias in the included studies, and extracted relevant data.

MAIN RESULTS

Of the 488 studies retrieved by the electronic searches, eight met the inclusion criteria and were analysed (300 participants). Response parameters were restricted to haemoglobin concentration, platelet count, spleen and liver volume and serum biomarkers (chitotriosidase and CCL18). Only one publication reported a 'low risk of bias' score in all parameters assessed, and all studies included were randomized.Four studies reported the responses to enzyme replacement therapy of previously untreated individuals with type 1 Gaucher disease. Two studies investigated maintenance enzyme replacement therapy in people with stable type 1 Gaucher disease previously treated for at least two years. One study compared substrate reduction therapy, enzyme replacement therapy and a combination thereof as maintenance therapy in people with type 1 Gaucher disease previously treated with enzyme replacement therapy. One study examined substrate reduction therapy in people with chronic neuronopathic (type 3) Gaucher disease who continued to receive enzyme replacement therapy.Treatment-naïve participants had similar increases in haemoglobin when comparing those receiving imiglucerase or alglucerase at 60 units/kg, imiglucerase or velaglucerase alfa at 60 U/kg, taliglucerase alfa at 30 units/kg or 60 units/kg, and velaglucerase alfa at 45 units/g or 60 units/kg. For platelet count response in participants with intact spleens, a benefit for imiglucerase over velaglucerase alfa at 60 units/kg was observed, mean difference -79.87 (95% confidence interval -137.57 to -22.17). There were no other significant differences in platelet count response when comparing different doses of velaglucerase alfa and of taliglucerase alfa, and when comparing imiglucerase to alglucerase. Spleen and liver volume reductions were not significantly different in any enzyme replacement therapy product or dose comparison study. Although a dose effect on serum biomarkers was not seen after nine months, a significantly greater reduction with higher dose was reported after 12 months in the velaglucerase study, mean difference 16.70 (95% confidence intervaI 1.51 to 31.89). In the two enzyme replacement therapy maintenance studies comparing infusions every two weeks and every four weeks, there were no significant differences in haemoglobin concentration, platelet count, and spleen and liver volumes over a 6 to 12 month period when participants were treated with the same cumulative dose.A total of 25 serious adverse events were reported, nearly all deemed unrelated to treatment.There are, as yet, no randomized trials of substrate reduction therapy in treatment-naïve patients that can be evaluated. Miglustat monotherapy appeared as effective as continued enzyme replacement therapy for maintenance of hematological, organ and biomarker responses in people with type 1 Gaucher disease previously treated with imiglucerase for at least two years. In those with neuronopathic Gaucher disease, no significant improvements in haemoglobin concentration, platelet count or organ volumes occurred when enzyme replacement therapy was augmented with miglustat.One randomized controlled study assessing substrate reduction therapy was published immediately prior to producing the final version of this review, and this, along with a further ongoing study (expected to be published in the near future), will be assessed for eligibility in a future update of the review.

AUTHORS' CONCLUSIONS

The results reflect the limitations of analysing evidence restricted to prospective randomized controlled trials, especially when dealing with chronic rare diseases. This analysis suggests that, during the first year of treatment, different recombinant glucocerebrosidases are bio-similar and non-inferior in safety and efficacy for surrogate biological response parameters. Enzyme replacement therapy given at 30 to 45 units/kg body weight every two to four weeks was generally as effective as the 60 unit/kg dose for the assessed clinical outcomes. The analysis emphasise the need to determine whether it is realistic to carry out multi-decade prospective clinical trials for rare diseases such as type 1 Gaucher disease. With large treatment effects on the classical manifestations of the disorder, therapeutic investigations in Gaucher disease mandate innovative trial designs and methodology to secure decisive data concerning long-term efficacy and safety - with the realization that knowledge about disease-modifying actions that are sustained are of crucial importance to people with this chronic condition.

Results from a 9-year Intensive Safety Surveillance Scheme (IS(3) ) in miglustat (Zavesca(®) )-treated patients

BACKGROUND

Following approval in the EU in 2002 and the USA in 2003, an Intensive Safety Surveillance Scheme (IS(3) ) was initiated to educate prescribers on the appropriate use of miglustat for the treatment of type I Gaucher disease (GD1), and to actively solicit safety-relevant information. This report summarises data from all patients enrolled in IS(3) between its initiation in 2003 and its closure in October 2012.

METHODS

The IS(3) was a prospective observational drug registry with a secure internet-based data capture system. All patients receiving miglustat at participating sites received standard medical care according to routine medical practice. Data on patient and disease characteristics were collected at patient enrolment, subsequent follow-up visits and treatment discontinuation (if applicable). Data were summarised using descriptive statistics.

RESULTS

During the 9 years of IS(3) , 407 patients were enrolled at 111 sites across 15 European countries. Approximately half (n = 202) had GD1, and half had other diseases (mainly Niemann-Pick disease type C (NP-C), for which miglustat was approved in Europe in 2009). In total, 368 patients had data from at least one follow-up visit, 192 of whom had GD1. IS(3) provided data from 798 patient-years exposure to miglustat. Safety-relevant data were consistent with earlier published 5-year findings from IS(3) , the safety profile reported for miglustat in GD1 clinical trials and other published information on GD1 manifestations.

CONCLUSIONS

Overall, the results of this long-term safety surveillance programme were in line with the well-known, documented safety profile of miglustat.

Management of bone disease in Gaucher disease type 1: clinical practice

Gaucher disease is a rare autosomal recessive disorder of glycosphingolipid metabolism resulting from deficient activity of the lysosomal enzyme beta-glucocerebrosidase that causes accumulation of glucosylceramide in tissue macrophage with damage to hematological, visceral, and skeletal organ systems. Severity and progression may vary independently among these domains, necessitating individualized therapy. Skeletal involvement is highly prevalent and often associated with intense pain, impaired mobility, and reduced quality of life. Enzyme replacement therapy improves parameters in all affected domains, but skeletal involvement requires longer treatment and higher dosages to obtain significant results. Despite numerous papers on bone complications in patients with Gaucher disease, there are no specific indications on how to assess properly bone involvement in such condition, the frequency of assessment, the use of markers for osteoblast and osteoclast activity, or the administration of bisphosphonates or other symptomatic drugs in adult and pediatric patients. Starting from a re-evaluation of cases with bone involvement, we have identified some common errors in the diagnostic approach and management. The aim of this paper was to propose a methodological and critical approach to the diagnosis, follow-up and treatment of bone disease in patients with Gaucher disease type 1.

Gaucher disease and bone manifestations

Gaucher disease is a relatively rare metabolic disease caused by the inherited deficiency of the lysosomal enzyme glucocerebrosidase. Gaucher disease affects multiple organs, among which is the skeleton. Bone involvement occurs frequently in Gaucher disease, and is one of its most debilitating features, reducing the quality of life of patients. Bone status is an important consideration for treatment to ameliorate symptoms and reduce the risk of irreversible complications. We have conducted a systematic review of all the various aspects of Gaucher disease, focusing on different skeletal manifestations, pathophysiology of bone alterations, clinical symptoms, and current diagnostic and therapeutic approaches.

Imaging of Gaucher disease

Gaucher disease is the prototypical lysosomal storage disease. It results from the accumulation of undegraded glucosylceramide in the reticuloendothelial system of the bone marrow, spleen and liver due to deficiency of the enzyme glucocerebrosidase. This leads to hematologic, visceral and skeletal maifestions. Build up of glucosylceramide in the liver and spleen results in hepatosplenomegaly. The normal bone marrow is replaced by the accumulating substrate leading to many of the hematologic signs including anemia. The visceral and skeletal manifestations can be visualized with various imaging modalities including radiography, computed tomography, magnetic resonance imaging (MRI) and radionuclide scanning. Prior to the development of enzyme replacement therapy, treatment was only supportive. However, once intravenous enzyme replacement therapy became available in the 1990s it quickly became the standard of care. Enzyme replacement therapy leads to improvement in all manifestations. The visceral and hematologic manifestations respond more quickly usually within a few months or years. The skeletal manifestations take much longer, usually several years, to show improvement. In recent years newer treatment strategies, such as substrate reduction therapy, have been under investigation. Imaging plays a key role in both initial diagnosis and routine monitoring of patient on treatment particularly volumetric MRI of the liver and spleen and MRI of the femora for evaluating bone marrow disease burden.

A Phase 3, multicenter, open-label, switchover trial to assess the safety and efficacy of taliglucerase alfa, a plant cell-expressed recombinant human glucocerebrosidase, in adult and pediatric patients with Gaucher disease previously treated with imiglucerase

Taliglucerase alfa is a β-glucosidase enzyme replacement therapy (ERT) approved in the US and other countries for the treatment of Gaucher disease (GD) in adults and is approved in pediatric and adult patients in Australia and Canada. It is the first approved plant cell-expressed recombinant human protein. A Phase 3, multicenter, open-label, 9-month study assessed safety and efficacy of switching to taliglucerase alfa in adult and pediatric patients with GD treated with imiglucerase for at least the previous 2years. Patients with stable disease were offered taliglucerase alfa treatment using the same dose (9-60U/kg body weight) and regimen of administration (every 2weeks) as imiglucerase. This report summarizes results from 26 adult and 5 pediatric patients who participated in the trial. Disease parameters (spleen and liver volumes, hemoglobin concentration, platelet count, and biomarker levels) remained stable through 9months of treatment in adults and children following the switch from imiglucerase. All treatment-related adverse events were mild or moderate in severity and transient in nature. Exploratory parameters of linear growth and development showed positive outcomes in pediatric patients. These findings provide evidence of the efficacy and safety profile of taliglucerase alfa as an ERT for GD in patients previously treated with imiglucerase. This trial was registered at www.clinicaltrials.gov as # NCT00712348.

Gaucher disease

Gaucher disease is the commonest lysosomal storage disease seen in India and worldwide. It should be considered in any child or adult with an unexplained splenohepatomegaly and cytopenia which are seen in the three types of Gaucher disease. Type 1 is the non-neuronopathic form and type 2 and 3 are the neuronopathic forms. Type 2 is a more severe neuronopathic form leading to mortality by 2 years of age. Definitive diagnosis is made by a blood test-the glucocerebrosidase assay. There is no role for histological examination of the bone marrow, liver or spleen for diagnosis of the disease. Molecular studies for mutations are useful for confirming diagnosis, screening family members and prognosticating the disease. A splenectomy should not be performed except for palliation or when there is no response to enzyme replacement treatment or no possibility of getting any definitive treatment. Splenectomy may worsen skeletal and lung manifestations in Gaucher disease. Enzyme replacement therapy (ERT) has completely revolutionized the prognosis and is now the standard of care for patients with this disease. Best results are seen in type 1 disease with good resolution of splenohepatomegaly, cytopenia and bone symptoms. Neurological symptoms in type 3 disease need supportive care. ERT is of no benefit in type 2 disease. Monitoring of patients on ERT involves evaluation of growth, blood counts, liver and spleen size and biomarkers such as chitotriosidase which reflect the disease burden. Therapy with ERT is very expensive and though patients in India have so far got the drug through a charitable access programme, there is a need for the government to facilitate access to treatment for this potentially curable disease. Bone marrow transplantation is an inferior option but may be considered when access to expensive ERT is not possible.

Sphingolipids and lysosomal pathologies

Endocytosed (glyco)sphingolipids are degraded, together with other membrane lipids in a stepwise fashion by endolysosomal enzymes with the help of small lipid binding proteins, the sphingolipid activator proteins (SAPs), at the surface of intraluminal lysosomal vesicles. Inherited defects in a sphingolipid-degrading enzyme or SAP cause the accumulation of the corresponding lipid substrates, including cytotoxic lysosphingolipids, such as galactosylsphingosine and glucosylsphingosine, and lead to a sphingolipidosis. Analysis of patients with prosaposin deficiency revealed the accumulation of intra-endolysosmal vesicles and membrane structures (IM). Feeding of prosaposin reverses the storage, suggesting inner membrane structures as platforms of sphingolipid degradation. Water soluble enzymes can hardly attack sphingolipids embedded in the membrane of inner endolysosomal vesicles. The degradation of sphingolipids with few sugar residues therefore requires the help of the SAPs, and is strongly stimulated by anionic membrane lipids. IMs are rich in anionic bis(monoacylglycero)phosphate (BMP). This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.

Enzyme replacement therapy for lysosomal diseases: lessons from 20 years of experience and remaining challenges

In 1964, Christian de Duve first suggested that enzyme replacement might prove therapeutic for lysosomal storage diseases (LSDs). Early efforts identified the major obstacles, including the inability to produce large quantities of the normal enzymes, the lack of animal models for proof-of-concept studies, and the potentially harmful immune responses to the "foreign" normal enzymes. Subsequently, the identification of receptor-mediated targeting of lysosomal enzymes, the cloning and overexpression of human lysosomal genes, and the generation of murine models markedly facilitated the development of enzyme replacement therapy (ERT). However, ERT did not become a reality until the early 1990s, when its safety and effectiveness were demonstrated for the treatment of type 1 Gaucher disease. Today, ERT is approved for six LSDs, and clinical trials with recombinant human enzymes are ongoing in several others. Here, we review the lessons learned from 20 years of experience, with an emphasis on the general principles for effective ERT and the remaining challenges.