Allogeneic hematopoietic cell transplantation (HCT) in Hurler's syndrome using a reduced intensity preparative regimen

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Allogeneic hematopoietic stem cell transplantation for inherited metabolic disorders

Allogeneic hematopoietic stem cell transplantation (HSCT) has been used to treat patients with inherited metabolic disorders (IMDs) for more than 40 years. In the first two decades, various IMDs were treated by HSCT with a wide variety of donor sources and conditioning regimens selected at the institutional level. However, HSCT was not always successful due to post-transplant complications such as graft failure. In the third decade, myeloablative conditioning with targeted busulfan-based pharmacokinetic monitoring was established as an optimal conditioning regimen, and unrelated cord blood was recognized as an excellent donor source. During the fourth decade, further improvements were made to transplant procedures, including modification of the conditioning regimen, and the survival rate after HSCT markedly improved. Simultaneously, several long-term observational studies for patients after HSCT clarified its therapeutic effects on growth and development of cognitive function, fine motor skills, and activities of daily living when compared with enzyme replacement therapy. Although immune-mediated cytopenia was newly highlighted as a problematic morbidity after HSCT for IMDs, especially in younger patients who received unrelated cord blood, a recent study with rituximab added to the conditioning raised expectations that this issue can be overcome.

Mucopolysaccharidosis Type I: Current Treatments, Limitations, and Prospects for Improvement

Mucopolysaccharidosis type I (MPS I) is a lysosomal disease, caused by a deficiency of the enzyme alpha-L-iduronidase (IDUA). IDUA catalyzes the degradation of the glycosaminoglycans dermatan and heparan sulfate (DS and HS, respectively). Lack of the enzyme leads to pathologic accumulation of undegraded HS and DS with subsequent disease manifestations in multiple organs. The disease can be divided into severe (Hurler syndrome) and attenuated (Hurler-Scheie, Scheie) forms. Currently approved treatments consist of enzyme replacement therapy (ERT) and/or hematopoietic stem cell transplantation (HSCT). Patients with attenuated disease are often treated with ERT alone, while the recommended therapy for patients with Hurler syndrome consists of HSCT. While these treatments significantly improve disease manifestations and prolong life, a considerable burden of disease remains. Notably, treatment can partially prevent, but not significantly improve, clinical manifestations, necessitating early diagnosis of disease and commencement of treatment. This review discusses these standard therapies and their impact on common disease manifestations in patients with MPS I. Where relevant, results of animal models of MPS I will be included. Finally, we highlight alternative and emerging treatments for the most common disease manifestations.

Considerations in Preparative Regimen Selection to Minimize Rejection in Pediatric Hematopoietic Transplantation in Non-Malignant Diseases

The variables that influence the selection of a preparative regimen for a pediatric hematopoietic stem cell transplant procedure encompasses many issues. When one considers this procedure for non-malignant diseases, components in a preparative regimen that were historically developed to reduce malignant tumor burden may be unnecessary. The primary goal of the procedure in this instance becomes engraftment with the establishment of normal hematopoiesis and a normal immune system. Overcoming rejection becomes the primary priority, but pursuit of this goal cannot neglect organ toxicity, or post-transplant morbidity such as graft-versus-host disease or life threatening infections. With the improvements in supportive care, newborn screening techniques for early disease detection, and the expansion of viable donor sources, we have reached a stage where hematopoietic stem cell transplantation can be considered for virtually any patient with a hematopoietic based disease. Advancing preparative regiments that minimize rejection and transplant related toxicity will thus dictate to what extent this medical technology is fully utilized. This mini-review will provide an overview of the origins of conditioning regimens for transplantation and how agents and techniques have evolved to make hematopoietic stem cell transplantation a viable option for children with non-malignant diseases of the hematopoietic system. We will summarize the current state of this facet of the transplant procedure and describe the considerations that come into play in selecting a particular preparative regimen. Decisions within this realm must tailor the treatment to the primary disease condition to ideally achieve an optimal outcome. Finally, we will project forward where advances are needed to overcome the persistent engraftment obstacles that currently limit the utilization of transplantation for haematopoietically based diseases in children.

Principles of alemtuzumab immunoablation in hematopoietic cell transplantation for non-malignant diseases in children: A review

Alemtuzumab is a humanized mAb targeted to CD52. Alemtuzumab is highly immunosuppressive with the ability to deplete T and B cells (in addition to other immune cell lines). A growing understanding of the PKs, dosing, and timing of administration of alemtuzumab has allowed for the study of its use as a conditioning agent for allogeneic HCT. The highly immunosuppressive properties of the drug are particularly appealing in the setting of non-malignant HCT, where GVHD provides no clinical benefit and relapse of malignancy is not applicable. In addition, the degree of immune suppression achieved with alemtuzumab has allowed for a reduction in the intensity of myeloablative cytotoxic agents included in some HCT conditioning regimens, allowing for fewer acute and late toxicities. This review paper will provide a comprehensive summary of the mechanism of action, PKs, dosing, and timing of alemtuzumab, a brief description of its use in various allogeneic HCT protocols for non-malignant conditions and a summary of the data regarding its use for GVHD therapy. The goal of this review was to provide an understanding as to how alemtuzumab might be safely incorporated into HCT conditioning regimens for children with non-malignant disease, allowing for expanded access to curative HCT therapy.

[Reduced-intensity conditioning haematopoietic stem cell transplantation in genetic diseases: Experience of the Spanish Working Group for Bone Marrow Transplantation in Children]

INTRODUCTION

Haematopoietic stem cell transplantation (HSCT) involves implanting cellular elements capable of generating a new and healthy haematopoietic system. Reduced intensity conditioning (RIC) consists of an immunosuppressive treatment to facilitate a progressive implant with lower morbidity. This type of conditioning can also lead to myelosuppression, which is potentially reversible over time. Reduced intensity conditioning enables HSCT to be performed on patients with genetic diseases for whom added comorbidity is undesirable due to the high doses of chemotherapy that accompanies conventional myeloablative regimens.

PATIENTS AND METHODS

An analysis was performed on the outcomes of 68 paediatric patients with genetic diseases who underwent HSCT with RIC between 2005 and 2013 in the of Paediatric Haematopoietic Stem Cell Transplantation Units that are part of the Spanish Working Group for Bone Marrow Transplantation in Children. A multicentre study was conducted including 68 patients, of whom 43 had Primary Immunodeficiency, 21 with congenital haematological diseases, and 4 with metabolic diseases.

RESULTS

Fifty (73.5%) of the 68 patients were still alive. The Overall Survival (OS) at nine years was 0.74. Twenty-three (33.8%) had some event during the course of the HSCT, with an event-free survival rate of 0.66. The OS in patients with haematological diseases was 0.81, being 0.7 in primary immunodeficiencies, and 0.4 in metabolic diseases. No significant difference was observed between the 3 groups of diseases. As regards the source of haematopoietic progenitors, there was an OS rate of 0.74 in patients transplanted with peripheral blood, 0.70 with bone marrow, and 0.70 and with cord blood, with no statistically significant differences.

CONCLUSIONS

Favourable results have been obtained in HSCT with reduced intensity conditioning in genetic diseases. It should be noted that the risks and benefits of the RIC in patients with metabolic diseases need to be assessed on an individual basis.

Stem Cell Therapy for the Central Nervous System in Lysosomal Storage Diseases

Neurological diseases with genetic etiologies result in the loss or dysfunction of neural cells throughout the CNS. At present, few treatment options exist for the majority of neurogenetic diseases. Stem cell transplantation (SCT) into the CNS has the potential to be an effective treatment modality because progenitor cells may replace lost cells in the diseased brain, provide multiple trophic factors, or deliver missing proteins. This review focuses on the use of SCT in lysosomal storage diseases (LSDs), a large group of monogenic disorders with prominent CNS disease. In most patients the CNS disease results in intellectual disability that is refractory to current standard-of-care treatment. A large amount of preclinical work on brain-directed SCT has been performed in rodent LSD models. Cell types that have been used for direct delivery into the CNS include neural stem cells, embryonic and induced pluripotent stem cells, and mesenchymal stem cells. Hematopoietic stem cells have been an effective therapy for the CNS in a few LSDs and may be augmented by overexpression of the missing gene. Current barriers and potential strategies to improve SCT for translation into effective patient therapies are discussed.

Alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following alemtuzumab, fludarabine, and melphalan RIC HCT

Reduced intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (HCT) with alemtuzumab, fludarabine, and melphalan is an effective approach for patients with nonmalignant disorders. Mixed chimerism and graft-versus-host-disease (GVHD) remain limitations on success. We hypothesized that higher levels of alemtuzumab at day 0 would result in a low risk of acute GVHD, a higher risk of mixed chimerism, and delayed early lymphocyte recovery and that alemtuzumab level thresholds for increased risks of these outcomes would be definable. We collected data from 105 patients to examine the influence of peritransplant alemtuzumab levels on acute GVHD, mixed chimerism, and lymphocyte recovery. The cumulative incidences of initial grades I-IV, II-IV, and III-IV acute GVHD in patients with alemtuzumab levels ≤0.15 vs ≥0.16 μg/mL were 68% vs 18% (P < .0001), 47% vs 13% (P = .0002), and 32% vs 8%, respectively (P = .005). The cumulative incidence of mixed chimerism in patients with an alemtuzumab level ≤0.15 μg/mL was 21%, vs 42% with levels of 0.16 to 4.35 μg/mL, and 100% with levels >4.35 μg/mL (P = .003). Patients with alemtuzumab levels ≤0.15 or 0.16 to 0.56 μg/mL had higher lymphocyte counts at day +30 and higher T-cell counts at day +100 compared with patients with levels ≥0.57 μg/mL (all P < .05). We conclude that peritransplant alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following RIC HCT with alemtuzumab, fludarabine, and melphalan. Precision dosing trials are warranted. We recommend a day 0 therapeutic range of 0.2 to 0.4 μg/mL.

Experience with Alemtuzumab, Fludarabine, and Melphalan Reduced-Intensity Conditioning Hematopoietic Cell Transplantation in Patients with Nonmalignant Diseases Reveals Good Outcomes and That the Risk of Mixed Chimerism Depends on Underlying Disease, Stem Cell Source, and Alemtuzumab Regimen

Alemtuzumab, fludarabine, and melphalan reduced-intensity conditioning (RIC) regimens are increasingly used for the hematopoietic cell transplantation (HCT) of pediatric and young adult patients with nonmalignant diseases. Early experience suggests that these regimens are associated with good survival but a high incidence of mixed chimerism, which we have previously shown to be influenced by the alemtuzumab schedule. We hypothesized that the underlying diagnosis and donor graft source would also affect the development of mixed chimerism and that the majority of patients would survive RIC HCT without graft loss. To examine this, we conducted a retrospective study of 206 patients with metabolic diseases, non-Fanconi anemia marrow failure disorders, and primary immune deficiencies who underwent 210 consecutive RIC HCT procedures at Cincinnati Children's Hospital. Ninety-seven percent of the patients engrafted. Mixed donor and recipient chimerism developed in 46% of patients. Patients with marrow failure had a low risk of mixed chimerism (hazard ratio [HR], .208; 95% confidence interval [CI], .061 to .709; P = .012). The risk of mixed chimerism was high in patients who received a cord blood graft (HR, 3.122; 95% CI, 1.236 to 7.888; P = .016). As expected, patients who received a proximal or higher dose per kilogram of alemtuzumab schedule also experienced higher rates of mixed chimerism (all HR > 2, all P < .05). At the time of last follow-up (median, 654 days; range, 13 to 3337), over 75% of patients had greater than 90% whole blood donor chimerism. A second transplantation was performed in 5% of patients. Three-year survival without retransplantation was 84% (95% CI, 71% to 98%) for patients who underwent transplantation with an HLA-matched sibling donor. Survival without retransplantation was negatively affected by lack of a matched related donor, increasing age, and development of grades III and IV acute graft-versus-host disease. We conclude that alemtuzumab, fludarabine, and melphalan RIC HCT offers good results for many patients and that the risk of developing mixed chimerism is influenced by underlying diagnosis, graft source, and alemtuzumab dosing.

Effect of donor chimerism to reduce the level of glycosaminoglycans following bone marrow transplantation in a murine model of mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder caused by deficient activity of the iduronate-2-sulfatase. This leads to accumulation of glycosaminoglycans (GAGs) in the lysosomes of various cells. Although it has been proposed that bone marrow transplantation (BMT) may have a beneficial effect for patients with MPS II, the requirement for donor-cell chimerism to reduce GAG levels is unknown. To address this issue, we transplanted various ratios of normal and MPS II bone marrow cells in a mouse model of MPS II and analyzed GAG accumulation in various tissues. Chimerism of whole leukocytes and each lineage of BMT recipients' peripheral blood was similar to infusion ratios. GAGs were significantly reduced in the liver, spleen, and heart of recipients. The level of GAG reduction in these tissues depends on the percentage of normal-cell chimerism. In contrast to these tissues, a reduction in GAGs was not observed in the kidney and brain, even if 100 % donor chimerism was achieved. These observations suggest that a high degree of chimerism is necessary to achieve the maximum effect of BMT, and donor lymphocyte infusion or enzyme replacement therapy might be considered options in cases of low-level chimerism in MPS II patients.

The effects of early and late bone marrow transplantation in siblings with alpha-mannosidosis. Is early haematopoietic cell transplantation the preferred treatment option?

This article documents both the neurological and physical outcomes of the first published set of siblings undergoing transplantation at differing ages for α-mannosidosis. The older brother, the index case, was diagnosed at the age of 3 years and underwent transplantation at 13 years for the treatment of increasing somatic problems and recurrent infections. The younger brother had undergone transplantation pre-symptomatically at 6 months of age. Their clinical, radiological and developmental outcomes are documented and compared with the previous published cases, with the case for early transplantation being weighted against other potential therapies.

Cord blood and bone marrow transplantation in inherited metabolic diseases: scientific basis, current status and future directions

Progressive degeneration of the central nervous system leading to the loss of neuromotor, neurophysiological and cognitive abilities is the fundamental clinical problem in patients with many inherited metabolic diseases (IMD). Worldwide experience shows that morbidity, quality of life, and survival in these patients can be improved by allogeneic haematopoietic stem cell transplantation (HSCT), particularly when performed early in the course of the disease. At present, while available for some conditions, exogenous enzyme replacement therapy is unable to correct cognitive and central nervous system disease because of its inability to cross the blood-brain barrier. In contrast, HSCT allows donor-derived, enzyme-producing cells to migrate to the brain and other organs providing a permanent enzyme replacement therapy. HSCT may also mediate non-hematopoietic cell regeneration or repair. Traditionally, bone marrow has been the graft source for IMD patients. However, in the last 5 years many studies utilizing unrelated donor umbilical cord blood (UCB) as a graft source have demonstrated that UCB provides rapid and increased access to transplantation with favourable outcomes. This review describes preclinical studies and past and present clinical treatment approaches and discusses current controversies and future directions of this promising field.

Umbilical cord blood transplantation for non-malignant diseases

Many factors, including lower risk of GVHD, rapid availability of 4/6-6/6 matched cord blood (CB) units and incremental gains in the outcomes, have led to an increasing use of CB transplantation (CBT) to treat many patients who lack fully matched adult BM donors. A large electronically searchable worldwide inventory of publicly banked CB units allows for quicker donor identification and selection. In this review, we examine the current status and cumulative experience of related and unrelated donor CBT for the treatment of non-malignant diseases, including hemoglobinopathies, BM failure syndromes, primary immunodeficiency diseases (PIDs) and inherited metabolic disorders (IMDs), and conclude that CBT offers a promising and effective therapy for these diseases. Future strategies to facilitate earlier diagnosis and to decrease transplant-related risks should further improve the short- and long-term outcomes. Every effort should be made to perform transplantation early in the course of disease before extensive damage to various tissues and organs ensues.

alpha-L-iduronidase therapy for mucopolysaccharidosis type I

More than 500 patients with mucopolysaccharidosis type IH (MPS IH; Hurler syndrome) have been treated with hematopoietic cell transplantation (HCT) throughout the world since the introduction of transplantation as therapy almost 30 years ago. More recently, the availability of recombinant alpha-L-iduronidase (IDUA) has resulted in the widespread treatment of less severe forms of MPS I with enzyme replacement therapy (ERT). In addition, over 50 MPS IH patients have been treated with a combination of ERT and HCT. The rationale for both ERT and HCT stems from the pivotal experiments performed 4 decades ago that showed alpha-L-iduronidase supplied in the environment can correct the accumulation of substrate in MPS I cells. Our purpose is to address the multiple applications associated with the therapeutic delivery of IDUA: intermittent delivery of recombinant protein (ERT), continuous administration through cellular therapy (HCT), the use of other stem cells or, potentially, correction of the enzyme defect itself through gene therapy approaches. Even though gene therapy and non-hematopoietic stem cell approaches, have yet to be tested in a clinical setting, it is possible that all these approaches will in the near future be a part of a paradigm shift from unimodal to multimodal therapy for MPS I.