The Genetic Basis, Lung Involvement, and Therapeutic Options in Niemann-Pick Disease: A Comprehensive Review.

Niemann-Pick Disease (NPD) is a rare autosomal recessive disease belonging to lysosomal storage disorders. Three types of NPD have been described: NPD type A, B, and C. NPD type A and B are caused by mutations in the gene SMPD1 coding for sphingomyelin phosphodiesterase 1, with a consequent lack of acid sphingomyelinase activity. These diseases have been thus classified as acid sphingomyelinase deficiencies (ASMDs). NPD type C is a neurologic disorder due to mutations in the genes NPC1 or NPC2, causing a defect of cholesterol trafficking and esterification. Although all three types of NPD can manifest with pulmonary involvement, lung disease occurs more frequently in NPD type B, typically with interstitial lung disease, recurrent pulmonary infections, and respiratory failure. In this sense, bronchoscopy with broncho-alveolar lavage or biopsy together with high-resolution computed tomography are fundamental diagnostic tools. Although several efforts have been made to find an effective therapy for NPD, to date, only limited therapeutic options are available. Enzyme replacement therapy with Olipudase α is the first and only approved disease-modifying therapy for patients with ASMD. A lung transplant and hematopoietic stem cell transplantation are also described for ASMD in the literature. The only approved disease-modifying therapy in NPD type C is miglustat, a substrate-reduction treatment. The aim of this review was to delineate a state of the art on the genetic basis and lung involvement in NPD, focusing on clinical manifestations, radiologic and histopathologic characteristics of the disease, and available therapeutic options, with a gaze on future therapeutic strategies.

Real-life impacts of olipudase alfa: The experience of patients and families taking an enzyme replacement therapy for acid sphingomyelinase deficiency.

BACKGROUND: Acid Sphingomyelinase Deficiency (ASMD) is an ultra-rare autosomal recessive lysosomal storage disorder characterized by intracellular lipid accumulation resulting from reduced function of acid sphingomyelinase. Olipudase alfa, an enzyme replacement therapy, was recently approved in several countries for the treatment of the non-neurologic manifestations of ASMD. Studies demonstrate improvement in organomegaly, pulmonary function and lipid profiles with olipudase alfa, yet little is known about its impact on quality of life (QoL) for patients and caregivers. The purpose of this study is to better understand the real-life impact of ASMD on patients and caregivers and assess how olipudase alfa impacts QoL for pediatric patients and their caregivers. METHODS: Caregivers of pediatric patients (≤ 18 years of age) with a confirmed diagnosis of ASMD that received olipudase alfa for at least 12 months were recruited in early 2022 through national patient organizations to participate in a global online questionnaire followed by semi-structured interviews. Ten caregivers of patients with ASMD who utilized olipudase alfa as an experimental therapy for pediatric patients participated in the study. Quantitative analysis of the results was undertaken, and qualitative data was analyzed using an inductive thematic approach. RESULTS: Ten eligible participants completed questionnaires, and 8 of the 10 went on to participate in structured interviews. Symptom burden of ASMD and impact on symptomatology and quality of life after olipudase alfa use are reported here. Five themes emerged from analysis: (1) ASMD is a systemic disease with a wide array of manifestations that significantly impact QoL; (2) Olipudase alfa was associated with improvements in all non-neurologic manifestations of ASMD; (3) Participants perceived the risk associated with olipudase alfa to be low and the benefits to greatly outweigh any risk or burden; (4) Participants reported an unmet need to treat the neurologic manifestations of the disease despite the benefits of olipudase alfa in the management of non-neurological symptoms; (5) Participants felt all patients with ASMD need access to olipudase alfa based on the life-changing experience they perceived. CONCLUSIONS: These findings highlight the sustained positive impact olipudase alfa had in many domains that are deemed important to patients and families living with ASMD and outline the extensive unmet need for patients and families living with ASMD.

Niemann­Pick disease: own observations and new therapeutic options / Niemann-Pick-betegség: saját megfigyelések és új terápiás lehetoségek.

Összefoglaló. A Niemann-Pick-betegség autoszomális recesszíven öröklodo lizoszomális tárolási betegség, amelynek hátterében a savi szfingomielináz enzim hiánya vagy csökkent aktivitása (A-, A/B- és B-típus), illetve a Niemann-Pick C intracelluláris koleszterintranszporter fehérje deficientiája (C- és D-típus) állhat. A defektus következtében szfingomielin és koleszterin halmozódik fel a sejtek lizoszómáiban. A betegség leggyakoribb prezentációs tünete a hepatosplenomegalia miatt elodomborodó nagy has. A legsúlyosabb tünetek a progresszív neurodegeneráció következményei. A diagnózis megerosítésében elengedhetetlen a genetikai vizsgálat, amely az érintett családokban lehetoséget teremt praenatalis genetikai vizsgálatok végzésére is. A betegség idejekorán történo felismerése rendkívül fontos, hiszen napjainkban a terápiás lehetoségek egyre bovülnek. A szubsztrátredukciós, illetve enzimpótló kezeléseknek köszönhetoen a hepatosplenomegalia mérsékelheto, és lassítható vagy visszafordítható a neurológiai tünetek progressziója. A szerzo két esetismertetésen keresztül mutatja be a Niemann-Pick-betegség fobb típusait, klinikumát, molekuláris genetikai hátterét, és elemzi a diagnosztikus, illetve terápiás lehetoségeket. Orv Hetil. 2021; 162(2): 74-80. Summary. The Niemann-Pick disease is an autosomal recessive lysosomal storage disorder caused by the lack or decreased activity of the acid sphingomyelinase enzyme or a deficiency of the Niemann-Pick C intracellular cholesterol transporter protein. As a result of the defect, sphingomyelin and cholesterol accumulate in the lysosomes of the cells. The most common presentation symptom of the disease is abdominal protrusion due to hepatosplenomegaly. The most severe symptoms are the consequences of progressive neurodegeneration. Genetic testing is essential to confirm the diagnosis, which also allows for prenatal genetic testing in the affected families. Early detection of the disease is extremely important as therapeutic options are expanding. Thanks to substrate reduction and enzyme replacement therapies, hepatosplenomegaly can be reduced, and progression of neurological symptoms can be reversed. Through two case reports, the author presents the main types, clinical manifestations, and molecular genetic background of this rare metabolic disorder. The author describes the diagnostic and therapeutic approaches to Niemann-Pick disease. Orv Hetil. 2021; 162(2): 74-80.

Clinical relevance of endpoints in clinical trials for acid sphingomyelinase deficiency enzyme replacement therapy.

BACKGROUND: Acid sphingomyelinase deficiency (ASMD) also known as Niemann-Pick disease, is a rare lysosomal storage disorder with a diverse disease spectrum that includes slowly progressive, chronic visceral (type B) and neurovisceral forms (intermediate type A/B), in addition to infantile, rapidly progressive fatal neurovisceral disease (type A). PURPOSE AND METHODS: We review the published evidence on the relevance of splenomegaly and reduced lung diffusion capacity to the clinical burden of chronic forms of ASMD. Targeted literature searches were conducted to identify relevant ASMD and non-ASMD studies for associations between diffusing capacity of the lungs for carbon monoxide (DLCO) and splenomegaly, with clinical parameters and outcome measures. RESULTS: Respiratory disease and organomegaly are primary and independent contributors to mortality, disease burden, and morbidity for patients with chronic ASMD. The degree of splenomegaly correlates with short stature, atherogenic lipid profile, and degree of abnormality of hematologic parameters, and thus may be considered a surrogate marker for bleeding risk, abnormal lipid profiles and possibly, liver fibrosis. Progressive lung disease is a prevalent clinical feature of chronic ASMD, contributing to a decreased quality of life (QoL) and an increased disease burden. In addition, respiratory-related complications are a major cause of mortality in ASMD. CONCLUSIONS: The reviewed evidence from ASMD natural history and observational studies supports the use of lung function and spleen volume as clinically meaningful endpoints in ASMD trials that translate into important measures of disease burden for patients.

Addressing neurodegeneration in lysosomal storage disorders: Advances in Niemann Pick diseases.

Most lysosomal storage disorders (LSDs) cause progressive neurodegeneration leading to early death. While the genetic defects that cause these disorders impact all cells of the body, neurons are particularly affected. This vulnerability may be explained by neuronal cells' critical dependence on the lysosomal degradative capacity, as they cannot use division to eliminate their waste. However, mounting evidence supports the extension of storage beyond lysosomes to other cellular compartments (mitochondria, plasma membrane and synapses) as a key event in pathogenesis. Impaired energy supply, oxidative stress, calcium imbalance, synaptic failure and glial alterations may all contribute to neuronal death and thus could be suitable therapeutic targets for these disorders. Here we review the pathological mechanisms underlying neurodegeneration in Niemann Pick diseases and therapeutic strategies developed in animal models and patients suffering from these devastating disorders. This article is part of the special issue entitled 'The Quest for Disease-Modifying Therapies for Neurodegenerative Disorders'.

Respiratory impairment in Niemann-Pick B disease: Two case reports and review for the pulmonologist.

Acid sphingomyelinase deficiency (ASMD), also called Niemann-Pick disease, is a storage disorder with pulmonary involvement but few respiratory symptoms in adults. However, the disease may evolve towards clinically relevant respiratory symptoms with referral to the pulmonologist for management and care. Based on two case reports illustrating respiratory impairment, the aim of this work was to review clinical features, diagnosis, respiratory prognostic and therapeutics for the pulmonologist. Overall, storage disorder should be suspected in the presence of hepatosplenomegaly and interstitial lung disease. Concomitant thrombopenia or hyperlipidemia should also draw attention. Following recent consensus guidelines, diagnosis is based on enzyme assay for ASM activity in blood, with subsequent gene sequencing once the biochemical diagnosis has been confirmed. Disease is slowly progressive and the main causes of death are respiratory and liver failure. Presence of emphysema lesions or worsening of respiratory symptoms should call for the intensification of treatment. Though enzyme replacement therapy is a promising way of development, lung transplantation might be considered for these patients in the absence of contraindication.

Quantitative Systems Pharmacology Modeling of Acid Sphingomyelinase Deficiency and the Enzyme Replacement Therapy Olipudase Alfa Is an Innovative Tool for Linking Pathophysiology and Pharmacology.

Acid sphingomyelinase deficiency (ASMD) is a rare lysosomal storage disorder with heterogeneous clinical manifestations, including hepatosplenomegaly and infiltrative pulmonary disease, and is associated with significant morbidity and mortality. Olipudase alfa (recombinant human acid sphingomyelinase) is an enzyme replacement therapy under development for the non-neurological manifestations of ASMD. We present a quantitative systems pharmacology (QSP) model supporting the clinical development of olipudase alfa. The model is multiscale and mechanistic, linking the enzymatic deficiency driving the disease to molecular-level, cellular-level, and organ-level effects. Model development was informed by natural history, and preclinical and clinical studies. By considering patient-specific pharmacokinetic (PK) profiles and indicators of disease severity, the model describes pharmacodynamic (PD) and clinical end points for individual patients. The ASMD QSP model provides a platform for quantitatively assessing systemic pharmacological effects in adult and pediatric patients, and explaining variability within and across these patient populations, thereby supporting the extrapolation of treatment response from adults to pediatrics.

Limited benefits of presymptomatic cord blood transplantation in neurovisceral acid sphingomyelinase deficiency (ASMD) intermediate type.

Acid sphingomyelinase (ASM) deficient Niemann-Pick disease is a lysosomal storage disorder resulting from mutations in the SMPD1 gene. The clinical spectrum distinguishes a severe infantile neurological form (type A), a non-neurological visceral form (type B) and a rare intermediate neurovisceral form. We report the first case of presymptomatic cord blood transplantation in a child with the intermediate type of ASM deficiency due to a homozygous Tyr369Cys mutation, whose affected elder brother had developed neurodevelopmental delay from 19 months of age, and had died from severe visceral complications at the age of 3. In the transplanted propositus, neurological deterioration became evident by 4 years of age; the child was alive at age 8, although severely disabled. Whereas the transplant prevented visceral progression and early death, it could only delay neurocognitive deterioration.

Pulmonary Involvement in Niemann-Pick Disease: A State-of-the-Art Review.

Niemann-Pick disease is a rare autosomal recessive lysosomal storage disease with three subtypes. Types A and B result from a deficiency of acid sphingomyelinase activity, associated with the accumulation of lipid-laden macrophages (so-called Niemann-Pick cells) in various tissues, especially the liver and spleen. Type A is a fatal neurodegenerative disorder of infancy. Type B Niemann-Pick disease is a less severe form with milder neurological involvement, characterized by hepatosplenomegaly, hyperlipidemia, and pulmonary involvement; most patients live into adulthood. Type C Niemann-Pick disease is a complex lipid storage disorder caused by defects in cholesterol trafficking, resulting in a clinical presentation dominated by neurological involvement. Pulmonary involvement occurs in all three types of Niemann-Pick disease, but most frequently in type B. Respiratory manifestations range from a lack of symptoms to respiratory failure. Progression of respiratory disease is slow, but inexorable, due to the accumulation of Niemann-Pick cells in the alveolar septa, bronchial walls, and pleura, potentially leading to a progressively worsening restrictive pattern on pulmonary function testing. Bronchoalveolar lavage has important diagnostic value because it shows the presence of characteristic Niemann-Pick cells. Radiographic findings consist of a reticular or reticulonodular pattern and, eventually, honeycombing, involving mainly the lower lung zones. The most common changes identified by high-resolution computed tomography are ground-glass opacities, mild smooth interlobular septal thickening, and intralobular lines. The aim of this review is to describe the main clinical, imaging, and pathological aspects of Niemann-Pick disease, with a focus on pulmonary involvement.

Role of ACAT1-positive late endosomes in macrophages: cholesterol metabolism and therapeutic applications for Niemann-Pick disease type C.

Macrophages in hyperlipidemic conditions accumulate cholesterol esters and develop into foamy transformed macrophages. During this transformation, macrophages demonstrate endoplasmic reticulum fragmentation and consequently produce acyl coenzyme A: cholesterol acyltransferase 1 (ACAT1)-positive late endosomes (ACAT1-LE). ACAT1-LE-positive macrophages effectively esterify modified or native low-density lipoprotein-derived free cholesterol, which results in efficient cholesterol esterification as well as atherosclerotic plaque formation. These macrophages show significant cholesterol ester formation even when free cholesterol egress from late endosomes is impaired, which indicates that free cholesterol is esterified at ACAT1-LE. Genetic blockade of cholesterol egress from late endosomes causes Niemann-Pick disease type C (NPC), an inherited lysosomal storage disease with progressive neurodegeneration. Induction of ACAT1-LE in macrophages with the NPC phenotype led to significant recovery of cholesterol esterification. In addition, in vivo ACAT1-LE induction significantly extended the lifespan of mice with the NPC phenotype. Thus, ACAT1-LE not only regulates intracellular cholesterol metabolism but also ameliorates NPC pathophysiology.

Safety study of adeno-associated virus serotype 2-mediated human acid sphingomyelinase expression in the nonhuman primate brain.

Niemann-Pick disease is a lysosomal storage disorder resulting from inherited deficiency in acid sphingomyelinase (ASM). Use of adeno-associated virus serotype 2 (AAV2) to deliver human acid sphingomyelinase (hASM) is currently being explored as a means to treat the devastating neurological features of NPD, which are refractory to traditional enzyme replacement therapy. In this study, we evaluated the long-term efficacy and safety of AAV2-hASM after direct infusion into the CNS of nonhuman primates. First, we confirmed the efficacy of AAV2-hASM in naive rats, which exhibited increased ASM expression and enzyme activity after infusion, without evidence of local or systemic toxicity. Next, the model was adapted to naive nonhuman primates (NHPs) with various doses of AAV2-hASM or saline delivered into the brainstem and both thalami. Strikingly, NHPs that received a high dose of AAV2-hASM displayed significant motor deficits that were not seen in low-dose animals in both the short-term (3-month) and long-term (9-month) treatment groups. In treated NHPs, ASM expression and activity were elevated with associated alterations in the sphingolipidomic profile in brain regions transduced with AAV2-hASM. Initial histological analysis indicated marked inflammatory reactions, and immunohistochemical analysis confirmed a robust inflammatory response. Importantly, pronounced upregulation of the chemokine CCL5, a target of ASM-mediated inflammatory signaling, was detected that correlated with the inflammatory response, providing a possible mechanism for hASM-associated toxicity. This study defines dose-dependent and dose-independent toxicities of AAV2-hASM in the naive primate brain, and reveals potential challenges in the design of a clinical trial.

Cathepsin B overexpression due to acid sphingomyelinase ablation promotes liver fibrosis in Niemann-Pick disease.

Niemann-Pick disease (NPD) is a lysosomal storage disease caused by the loss of acid sphingomyelinase (ASMase) that features neurodegeneration and liver disease. Because ASMase-knock-out mice models NPD and our previous findings revealed that ASMase activates cathepsins B/D (CtsB/D), our aim was to investigate the expression and processing of CtsB/D in hepatic stellate cells (HSCs) from ASMase-null mice and their role in liver fibrosis. Surprisingly, HSCs from ASMase-knock-out mice exhibit increased basal level and activity of CtsB as well as its in vitro processing in culture, paralleling the enhanced expression of fibrogenic markers α-smooth muscle actin (α-SMA), TGF-ß, and pro-collagen-α1(I) (Col1A1). Moreover, pharmacological inhibition of CtsB blunted the expression of α-SMA and Col1A1 and proliferation of HSCs from ASMase-knock-out mice. Consistent with the enhanced activation of CtsB in HSCs from ASMase-null mice, the in vivo liver fibrosis induced by chronic treatment with CCl(4) increased in ASMase-null compared with wild-type mice, an effect that was reduced upon CtsB inhibition. In addition to liver, the enhanced proteolytic processing of CtsB was also observed in brain and lung of ASMase-knock-out mice, suggesting that the overexpression of CtsB may underlie the phenotype of NPD. Thus, these findings reveal a functional relationship between ASMase and CtsB and that the ablation of ASMase leads to the enhanced processing and activation of CtsB. Therefore, targeting CtsB may be of relevance in the treatment of liver fibrosis in patients with NPD.

The pathogenesis and treatment of acid sphingomyelinase-deficient Niemann-Pick disease.

Patients with Niemann-Pick disease (NPD) Types A and B have an inherited deficiency of acid sphingomyelinase (ASM) activity. The clinical spectrum of this disorder ranges from the infantile neurological form that results in death by 3 years of age (NPD Type A) to the non-neurological form that is compatible with survival into adulthood (NPD Type B). Intermediate cases have also been reported, and the disease is best thought of as a single entity with a spectrum of phenotypes. ASM deficiency is panethnic, but appears to be more frequent in individuals of Middle Eastern and North African descent. Current estimates of the disease incidence range from 0.5 to 1 per 100,000 births, although these approximations are thought to underestimate the true frequency of the disorder. The gene encoding ASM--SMPD1--has been studied extensively, and over 100 mutations in SMPD1 have been found to cause ASM-deficient NPD. Based on these findings, DNA-based carrier screening has been implemented in the Ashkenazi Jewish community. ASM-knockout mouse models also have been generated and used to investigate disease pathogenesis and treatment with stem cell transplantation, gene therapy and enzyme replacement therapy (ERT). Based on these studies, clinical trials of ERT are underway in patients with non-neurological ASM-deficient NPD.

Neural stem cell implantation extends life in Niemann-Pick C1 mice.

In order to evaluate the phenotypic effects of implanted neural stem cells (NSCs) in the mouse model of Niemann-Pick C (NPC) disease, we injected a well-characterized clone of murine NSCs into the cerebella of neonatal Npc1(-/-) and control mice. The implanted cells survived and were abundant in some regions of the cerebellum. Life span was lengthened in NPC mice with the implanted NSCs. However, the rate of weight gain and subsequent weight loss, resulting from neurodegeneration, was not significantly different from un-injected controls. Ataxia was measured by Rota-Rod performance. The overall rate of decline in time on the Rota-Rod was not significantly slowed down. Thus, in this small group of NPC mice, a single administration in the neonatal period of the NSCs (which were not engineered to over-express the missing gene and not directed into the parenchyma) was only partially therapeutic.

Combination brain and systemic injections of AAV provide maximal functional and survival benefits in the Niemann-Pick mouse.

Niemann-Pick disease (NPD) is caused by the loss of acid sphingomyelinase (ASM) activity, which results in widespread accumulation of undegraded lipids in cells of the viscera and CNS. In this study, we tested the effect of combination brain and systemic injections of recombinant adeno-associated viral vectors encoding human ASM (hASM) in a mouse model of NPD. Animals treated by combination therapy exhibited high levels of hASM in the viscera and brain, which resulted in near-complete correction of storage throughout the body. This global reversal of pathology translated to normal weight gain and superior recovery of motor and cognitive functions compared to animals treated by either brain or systemic injection alone. Furthermore, animals in the combination group did not generate antibodies to hASM, demonstrating the first application of systemic-mediated tolerization to improve the efficacy of brain injections. All of the animals treated by combination therapy survived in good health to an investigator-selected 54 weeks, whereas the median lifespans of the systemic-alone, brain-alone, or untreated ASM knockout groups were 47, 48, and 34 weeks, respectively. These data demonstrate that combination therapy is a promising therapeutic modality for treating NPD and suggest a potential strategy for treating disease indications that cause both visceral and CNS pathologies.

Successful hematopoietic stem cell transplantation for Niemann-Pick disease type B.

Histocompatible hematopoietic stem cell transplantation (HSCT) was conducted on a 4.5-year-old girl with Niemann-Pick disease type B. The donor was her unaffected brother. At the time of transplantation, she had severe pulmonary disease. After her first HSCT, she developed graft failure. Five years after her second HSCT, her sphingomyelinase levels are within normal levels, she has no pulmonary symptoms, and aside from persistent graft versus host disease, she is doing well.