**3. Expanding Indications for transplant**

HSCT has been explored in a number of malignant and nonmalignant diseases. Currently, research is rapidly expanding in areas not historically considered for HSCT. Also, as morbidity and mortality decrease, HSCT is being reconsidered for many diseases in which HSCT was previously considered and rejected. Several potential indications are reported in this section.

#### **3.1 Beta-thalassemia**

368 Advances in Hematopoietic Stem Cell Research

transplant) (Peters,1998,2004); outcome is affected by disease status, donor source and HLA matching (Peters, 2004). The most common causes of death are progressive cerebral X-ALD disease and GVHD. TRM is 10% in related donors and 18% in unrelated donors. Five-year survival rates for recipients of related donor and unrelated donor transplants have been reported at 64% and 53%, respectively (Peters, 2004); and finally, survival is clearly affected by disease status at time of transplant as assessed by the number of neurologic deficits and MRI severity score. In those with 0 or 1 neurologic deficit and MRI score of less than 9, the 5-year survival was 92% compare to 45% in all other patients

GLD or Krabbe disease is an autosomal recessive lysosomal storage disorder caused by deficiency of galactocerebrosidase (GALC), an enzyme responsible for degrading betagalactocerebroside, a major component of myelin sheath. GALC deficiency causes defective and decreased myelination and inflammation in the CNS and peripheral nervous systems from catabolic derivatives of beta-galactocerebroside such as psychosine. These changes lead to progressive deterioration in neurologic and cognitive function, resulting in spasticity, mental deterioration, blindness, deafness, seizures and early death. In the most severe "early onset or infantile" form, children develop symptoms before 6 months of age and usually die by age 2. In the "late onset" form, symptoms appear in early to late childhood, but only a few children survive into teenage

HSCT is the only available therapy with potential to improve neurocognitive function, increase survival and alter the natural history of the disease. Krivit and colleagues (Krivit et al., 1998) described the use of allogeneic HSCT to treat 5 patients with GLD (4 received HLA-sibling HSCT & 1 unrelated cord). Two children with late onset GLD had substantial neurologic disability and they had resolution of their symptoms after transplant. Cognition, language and memory continued to develop normally in 3 children with late-onset disease. Most children had improvement in MRI, CSF protein levels, and all had normalization of enzyme activity. These findings support the use of allogeneic HSCT for children with GLD. If a matched related donor is not available, unrelated cord blood has also been shown to be

MLD is an autosomal recessive lysosomal disorder arising from deficiency of arylsulfatase A (ARSA) enzyme activity and characterized by increased urinary sulfatides. The clinical phenotype is a broad continuous spectrum ranging from early-infantile MLD to adult-onset forms. Clinical symptoms vary depending on timing of presentation (infantile, juvenile or adult form), but all include abnormal cognitive skills, behavioral abnormalities with adults having mental regression and psychiatric symptoms, progressive spastic disease and

The first BMT for MLD was performed more than 20 years ago. According to the EBMT and CIBMTR registries, more than 100 transplants have since been performed for this disorder. Despite this number, the lack of graft-outcome and long-term follow up studies makes it

(Peters, 2004).

years.

**2.7.4 Globoid leukodystrophy (GLD)** 

beneficial (Escolar et al., 2005)**.** 

increased CSF protein.

**2.7.5 Metachromatic leukodystrophy (MLD)** 

Thalassemias result from mutations of the globin genes that cause reduced or absent hemoglobin production, reducing oxygen delivery. To treat the anemia and restore oxygen delivery to tissues, chronic lifelong transfusions are required in those who have thalassemia major. However, this promotes progressive iron overload and organ damage. The only definitive cure for thalassemia is to correct the genetic defect by HSCT. Transplantation is recommended early, if an allogeneic healthy related sibling donor or a related CB is available. Several studies have suggested that umbilical cord blood transplant (UCBT) recipients benefit from a lower risk of GVHD (Gluckman, 1997; Wagner, 1995) and a recent analysis comparing 113 children who received a UCBT from a compatible sibling with 2052 HLA-identical sibling marrow transplant recipients showed that children receiving UCB experienced a significantly reduced risk of developing aGVHD and cGVHD (Rocha, 2000).

Prior to transplant, the patient should be assigned to 1 of 3 Pesaro risk class to assess risk factors for BMT. This classification is based upon clinical features of thalassemia that include: (1) adherence to a program of regular iron chelation therapy, (2) the presence or absence of hepatomegaly and (3) the presence or absence of portal fibrosis observed by liver biopsy. The conditioning regimen is uniform for classes 1 and 2 patients, but is modified for those who have class 3 features due to an increased risk of transplant-related mortality (Lucarelli, 1990). As a result of this risk classification and the development of new conditioning regimens, the outcome of thalassemia patients have improved with thalassemia-free survival and EFS over 70% reported worldwide. When stratifying patients, initially those with Pesaro Class 1 characteristics < 17 years had a superior thalassemia-free survival; however, recent updates show that outcomes are very similar across all three risk categories after employing risk-based conditioning regimens (Bhatia, 2008). Unrelated donor transplants are also used in selected patients (Bhatia, 2008). Following transplant, iron overload may still be a problem; consequently, chelation or phlebotomy may still be necessary.

#### **3.2 Sickle cell disease (SCD)**

SCD contrasts with thalassemia major by its variable course of clinical severity. Its typical clinical manifestation include anemia, severe painful crisis, acute chest syndrome, splenic

Hematopoietic Stem Cells Therapeutic Applications 371

burst sustained by pre transplant memory cells, the organ is repopulated by likely harvest-derived naïve T cells, and also the T-lymphocyte repertoire may significantly differ before and after autografting, thus suggesting the possibility of achieving an immune resetting through autologous HSCT (Isaacs, 2004; Sun, 2004). Allogeneic probably results in the highest potential for cure. However, there is higher morbidity and mortality caused by GVHD. Marmont summarize several allogeneic transplant cases in which the patient achieved full post transplant donor chimerism but their autoimmune disease still relapsed. A European database, the International Autoimmune Disease Stem Cell Project Database, was established in 1996. The database contains 600 patients, most treated with autologous HSCT; 15% of the patients registered are children. Some of the autoimmune diseases in children that were treated with HSCT are juvenile idiopathic arthritis, immune cytopenias, systemic sclerosis, systemic lupus and Crohn's disease

ARO is a rare genetic bone disease in which a deficit in bone resorption by osteoclasts leads to increased bone density and secondary defects. The disease is often lethal early in life unless treated with HSCT. However, recently the dissection of the molecular bases of the disease has shown that ARO is genetically heterogeneous and has revealed the presence of subsets of patients which do not benefit from HSCT, highlighting the importance of molecular diagnosing ARO to identify and establish the proper therapies for better prognosis (Villa, 2008). EBMT conducted a retrospective analysis of 122 children who had received an allogeneic HSCT for ARO between 1980 and 2001. The actuarial probabilities of 5 years disease free survival were 73% for recipients of a genotype HLA-identical HSCT (n=40), 43% for recipients of a phenotype HLA-identical or one HLA antigen mismatch graft from a related donor (n=21), 40% for recipients of a graft from a matched unrelated donor (n=20) and 24% for patients who received a graft from an HLA-haplotype-mismatch related donor (n=41). Causes of death after HSCT were graft failure and early-TRM complications. Conservation of vision was better in children transplanted before the age of 3 months (Driessen, 2003). HSCT is the only curative treatment for ARO and should be offered as

CEP is a rare autosomal recessive disorder of porphyrin metabolism in which the genetic defect is the deficiency of uroporphyrinogen III cosynthase (UIIIC). Deficiency of this enzyme results in an accumulation of high amounts of uroporphyrin I in all tissues leading to hemolytic anemia, splenomegaly, erythrodontia, bone fragility, exquisite photosensitivity and mutilating skin lesions. The vital prognosis is very bad and until now, no treatment seems to be efficient. Bone marrow transplantation seems to be able to correct the enzymatic deficit that causes the disease because it is located in the bone marrow. A few cases of patients have been reported to be cured of the disease with stem cell transplantation (Shaw, 2001). HSCT should be strongly considered because this is currently the only known

(Rabusin, 2008).

early as possible.

curative therapy.

**3.4 Other non-malignant disease** 

**3.4.1 Autosomal recessive osteopetrosis (ARO)** 

**3.4.2 Congenital erythropoietic porphyria (CEP)** 

sequestration, stroke (clinically overt and silent), chronic pulmonary and renal dysfunction, growth retardation, neuropsychological deficits and premature death. Historically, the mainstays of treatment are both preventive and supportive. The three major therapeutic options available for children affected with SCD are: chronic blood transfusion, hydroxyurea and HSCT. Of these options, only HSCT affords patients the possibility of cure. The use of transplantation for the treatment of patients with SCD has been considered for many years. However, because of the morbidity and mortality of HSCT, it was considered too risky. Recently, due to advances in supportive care and immunosuppressive therapy, transplant is again being considered for SCD. The preliminary experience of HSCT for betathalassemia major has in part provided the rationale for extending this treatment to sickle cell anemia. Walter et al (Walter et al., 1996) used selection criteria similar to that applied to patients with beta thalassemia major and chose patients with debilitating clinical events, including stroke, recurrent acute chest syndrome and recurrent painful vaso-occlusive crises, but selected children rather than adults and before the development of permanent end organ damage. These recommendations are associated with significant morbidity and early mortality among patients with SCD and are the criteria upon which most early studies using HSCT are based.

Three major clinical series account for most of the experience of HSCT for SCD (Bernaudin et al, 2007; Walters et al, 2000; Vermylen et al, 1998). In all three series, the majority of patients received HLA-identical sibling donor allograft and all patients received the same conditioning regimen (busulfan 14-16mg/kg with cytoxan 200) and GVHD prophylaxis (ATG, cyclosporine and methotrexate). The results of these three studies were very similar. OS was 92-94% and EFS was 82-86% with a median follow-up range of 0.9-17.9 years. TRM from all three series was also similar and was approximately 7% with infections as the chief cause. Similarly, the incidence of aGVHD > grade II was approximately 15-20%. The rate of cGVHD was 20% in Vermylen et al study compared to 12 and 13.5% in the Walters et al and Bernaudin et al reports, respectively. While HSCT is curative in patients with SCD, only 14-18% of patients have a matched family donor. The use of unrelated donors in HSCT for SCD is under development. There are several limitations which restrict the uniform utilization of allogeneic adult donors that include donor availability, and the high risk of severe aGVHD. The use of unrelated cord blood transplantation is also being considered and recent studies have shown promising results, although g raft rejection and aGVHD still remain issues. In addition, efforts to expand the application of HSCT for SCD have been restricted not only by lacking suitable donors, but also by the risk of significant toxicity from the myeloablative conditioning regimen. With the advent of lower intensity conditioning regimens which rely on less myeloablation and more immunosuppression, many of the long-term effects, such as growth and endocrine dysfunction observed after myeloablative conditioning regimens, may be ameliorated.

#### **3.3 Autoimmune disease**

Autoimmune diseases are often controlled with treatments that act on the immune system. However, these therapies are usually not curative. Recently many autoimmune diseases have been treated with HSCT. The goal of autologous HSCT is to reset the immune system. Studies on thymic lymphocytes after auto HSCT have shown that, after a

sequestration, stroke (clinically overt and silent), chronic pulmonary and renal dysfunction, growth retardation, neuropsychological deficits and premature death. Historically, the mainstays of treatment are both preventive and supportive. The three major therapeutic options available for children affected with SCD are: chronic blood transfusion, hydroxyurea and HSCT. Of these options, only HSCT affords patients the possibility of cure. The use of transplantation for the treatment of patients with SCD has been considered for many years. However, because of the morbidity and mortality of HSCT, it was considered too risky. Recently, due to advances in supportive care and immunosuppressive therapy, transplant is again being considered for SCD. The preliminary experience of HSCT for betathalassemia major has in part provided the rationale for extending this treatment to sickle cell anemia. Walter et al (Walter et al., 1996) used selection criteria similar to that applied to patients with beta thalassemia major and chose patients with debilitating clinical events, including stroke, recurrent acute chest syndrome and recurrent painful vaso-occlusive crises, but selected children rather than adults and before the development of permanent end organ damage. These recommendations are associated with significant morbidity and early mortality among patients with SCD and are the criteria upon which most early studies

Three major clinical series account for most of the experience of HSCT for SCD (Bernaudin et al, 2007; Walters et al, 2000; Vermylen et al, 1998). In all three series, the majority of patients received HLA-identical sibling donor allograft and all patients received the same conditioning regimen (busulfan 14-16mg/kg with cytoxan 200) and GVHD prophylaxis (ATG, cyclosporine and methotrexate). The results of these three studies were very similar. OS was 92-94% and EFS was 82-86% with a median follow-up range of 0.9-17.9 years. TRM from all three series was also similar and was approximately 7% with infections as the chief cause. Similarly, the incidence of aGVHD > grade II was approximately 15-20%. The rate of cGVHD was 20% in Vermylen et al study compared to 12 and 13.5% in the Walters et al and Bernaudin et al reports, respectively. While HSCT is curative in patients with SCD, only 14-18% of patients have a matched family donor. The use of unrelated donors in HSCT for SCD is under development. There are several limitations which restrict the uniform utilization of allogeneic adult donors that include donor availability, and the high risk of severe aGVHD. The use of unrelated cord blood transplantation is also being considered and recent studies have shown promising results, although g raft rejection and aGVHD still remain issues. In addition, efforts to expand the application of HSCT for SCD have been restricted not only by lacking suitable donors, but also by the risk of significant toxicity from the myeloablative conditioning regimen. With the advent of lower intensity conditioning regimens which rely on less myeloablation and more immunosuppression, many of the long-term effects, such as growth and endocrine dysfunction observed after

Autoimmune diseases are often controlled with treatments that act on the immune system. However, these therapies are usually not curative. Recently many autoimmune diseases have been treated with HSCT. The goal of autologous HSCT is to reset the immune system. Studies on thymic lymphocytes after auto HSCT have shown that, after a

myeloablative conditioning regimens, may be ameliorated.

using HSCT are based.

**3.3 Autoimmune disease** 

burst sustained by pre transplant memory cells, the organ is repopulated by likely harvest-derived naïve T cells, and also the T-lymphocyte repertoire may significantly differ before and after autografting, thus suggesting the possibility of achieving an immune resetting through autologous HSCT (Isaacs, 2004; Sun, 2004). Allogeneic probably results in the highest potential for cure. However, there is higher morbidity and mortality caused by GVHD. Marmont summarize several allogeneic transplant cases in which the patient achieved full post transplant donor chimerism but their autoimmune disease still relapsed. A European database, the International Autoimmune Disease Stem Cell Project Database, was established in 1996. The database contains 600 patients, most treated with autologous HSCT; 15% of the patients registered are children. Some of the autoimmune diseases in children that were treated with HSCT are juvenile idiopathic arthritis, immune cytopenias, systemic sclerosis, systemic lupus and Crohn's disease (Rabusin, 2008).

#### **3.4 Other non-malignant disease**

#### **3.4.1 Autosomal recessive osteopetrosis (ARO)**

ARO is a rare genetic bone disease in which a deficit in bone resorption by osteoclasts leads to increased bone density and secondary defects. The disease is often lethal early in life unless treated with HSCT. However, recently the dissection of the molecular bases of the disease has shown that ARO is genetically heterogeneous and has revealed the presence of subsets of patients which do not benefit from HSCT, highlighting the importance of molecular diagnosing ARO to identify and establish the proper therapies for better prognosis (Villa, 2008). EBMT conducted a retrospective analysis of 122 children who had received an allogeneic HSCT for ARO between 1980 and 2001. The actuarial probabilities of 5 years disease free survival were 73% for recipients of a genotype HLA-identical HSCT (n=40), 43% for recipients of a phenotype HLA-identical or one HLA antigen mismatch graft from a related donor (n=21), 40% for recipients of a graft from a matched unrelated donor (n=20) and 24% for patients who received a graft from an HLA-haplotype-mismatch related donor (n=41). Causes of death after HSCT were graft failure and early-TRM complications. Conservation of vision was better in children transplanted before the age of 3 months (Driessen, 2003). HSCT is the only curative treatment for ARO and should be offered as early as possible.

#### **3.4.2 Congenital erythropoietic porphyria (CEP)**

CEP is a rare autosomal recessive disorder of porphyrin metabolism in which the genetic defect is the deficiency of uroporphyrinogen III cosynthase (UIIIC). Deficiency of this enzyme results in an accumulation of high amounts of uroporphyrin I in all tissues leading to hemolytic anemia, splenomegaly, erythrodontia, bone fragility, exquisite photosensitivity and mutilating skin lesions. The vital prognosis is very bad and until now, no treatment seems to be efficient. Bone marrow transplantation seems to be able to correct the enzymatic deficit that causes the disease because it is located in the bone marrow. A few cases of patients have been reported to be cured of the disease with stem cell transplantation (Shaw, 2001). HSCT should be strongly considered because this is currently the only known curative therapy.

Hematopoietic Stem Cells Therapeutic Applications 373

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[7] Ayas M, Al-Jefri A, Al-Seraihi A, Elkum N, Al-Mahr M, El-Solh H. Matched-related

year's experience. *Bone Marrow Transplant.* Aug 2008; 42 Suppl 1:S45-S48. [8] Ayas M, Solh H, Mustafa MM, et al. Bone marrow transplantation from matched siblings

[9] Baccarani M, Cortes J, Pane F, Niederwieser D, Saglio G, Apperley J, et al. Chronic

[10] Bader P, Kreyenberg H, Hoelle W, et al. Increasing mixed chimerism defines a high-risk

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[14] Berger R, Bernheim A, Gluckman E, Gisselbrecht C. In vitro effect of cyclophosphamide

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#### **3.4.3 Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome**

IPEX syndrome is a rare, fatal autoimmune disorder caused by mutations in the forkhead box protein 3 (FOXP3) genes leading to the disruption of signaling pathways involved in regulatory T-Lymphocyte function. Patients with IPEX syndrome often present in early infancy and without therapeutic intervention, affected male patients usually die within the first or second year of life. These patients require supportive therapy including parental nutrition, insulin, antibiotics and blood transfusions. Immunosuppressive therapy has been used with variable improvement in symptoms. Correction of the dysregulated immune system can be achieved by allogeneic HSCT using a suitable donor. Although, HSCT is the only viable option for long-term survival, patients are usually very ill to tolerate traditional myeloablative conditioning regimens. Recent studies reported the successful outcome of HSCT using a low-intensity, nonmyeloablative conditioning regimen in 2 patients with IPEX syndrome and significant pre transplant risk factors (Burroughs, 2010; Rao, 2007).

#### **3.4.4 Epidermolysis bullosa (EM)**

EB is a group of blistering skin disorders resulting from mutations in genes encoding protein components of the cutaneous basement membrane zone. HSCT has been shown to ameliorate the deficiency of the skin-specific structural protein in children with EB (Fujita, 2010; Tolar, 2011).
