Hematopoietic stem cell transplantation as a treatment for childhood cerebral adrenoleukodystrophy (ALD) has historically only been successful in early disease. As ALD is associated with oxidative damage, we reasoned that adjunctive therapy with an antioxidant agent, N-acetyl-L-cysteine (NAC), may provide protection from rapid neurologic decline in boys with advanced cerebral disease. We report three boys with advanced ALD, whose neurologic status and brain radiographic findings were stabilized by treatment including NAC 8–11 months after hematopoietic stem cell transplantation. These results contrast with previous survival data in cerebral ALD patients who had a similar degree of brain involvement, all of whom died within 1 year of stem cell infusion despite a full donor engraftment. Thus, NAC merits investigation as a therapeutic strategy for patients with advanced ALD as an intervention that could change this lethal disease to a condition amendable to treatment with hematopoietic stem cell transplantation.
Adrenoleukodystrophy (ALD) is an X-linked disorder of very long-chain fatty acid (VLCFA) metabolism caused by loss of function of the peroxisomal transporter ABCD1.1, 2 Elevated plasma levels of VLCFA correlate with adrenal and nervous system dysfunction. Initial symptoms of the cerebral form of ALD are visual and hearing disturbances and defects in cognition and motor function, depending on localization of disease.
Of several ALD phenotypes that can be distinguished on the basis of clinical onset and manifestations, the cerebral form of ALD is the most severe, resulting in a rapid neurologic deterioration and early death.3 The prognosis for symptomatic boys with cerebral ALD with extensive white matter changes on magnetic resonance imaging (MRI) is poor.4, 5 The Loes score,6, 7 a system of scoring MRI in ALD, has been found to be predictive of survival after hematopoietic stem cell transplantation (HSCT). Owing to central nervous system demyelination, death occurs usually within 2–5 years of clinical onset, unless the patient receives HSCT. Overall, the 5-year survival of patients with a Loes MRI severity score of <9 before HSCT is 92%, versus 45% for patients who have a severity score of >9 and have more than one neurologic deficit.8 As a result of the increased risk of death after HSCT, transplant is not currently recommended for individuals with advanced disease. Unfortunately, there are no other current treatment alternatives.
Neuropsychological testing identifies the functional deficits associated with the disease process and is a sensitive measure of disease severity at the time of diagnosis as well as a measure of disease progression during and after treatment. The Wechsler Performance IQ (PIQ) of <80 predicts poor functional outcome after HSCT.9, 10
Based on Powers’ work on oxidative stress and damage in ALD,11 we have explored the use of an agent with antioxidant and radical scavenger capabilities, N-acetyl-L-cysteine (NAC), in an attempt to arrest progression of demyelination in advanced ALD. NAC stimulates glutathione synthesis and scavenges free radicals, which has been hypothesized to provide neuroprotective capacity.12, 13, 14 Here, we show that administration of NAC before and after HSCT in three patients with advanced ALD resulted in survival of a disease process that would be expected to be lethal.
Patients and methods
All boys were delivered at full-term with early developmental milestones acquired within normal age level expectations. The diagnosis of ALD was established in all patients by elevation of VLCFA and characteristic changes by MRI. The Loes scores and PIQ data are provided in Table 1.
A 10-year-old boy was admitted to the hospital with headaches. An MRI was performed, demonstrating significant abnormalities in the posterior body and splenium of the corpus callosum, as well as in the corticospinal tracts and middle cerebellar peduncle.
Results of the neuropsychological testing before HSCT indicated significant auditory and visual processing deficits, whereas vocabulary, academic achievement and adaptive functions were low average to average.
A 9.8-year-old boy developed behaviors consistent with attention deficit/hyperactivity disorder and changes in his ability to hear. The MRI indicated marked abnormalities in the posterior white matter involving the occipital and parietal lobes and extending across the splenium of the corpus callosum and the corticospinal tracts.
Before HSCT, neuropsychological testing yielded both auditory and visual processing impairment, severe difficulties in fine motor speed and coordination, and poor non-verbal reasoning, in contrast to executive function and academic achievement which were low average.
A 9.9-year-old boy developed an impaired ability to track with his right eye, dysarthria and difficulty walking. The MRI showed bilateral parietal occipital white matter abnormalities extending into the posterior rim of the internal capsule into the front lobe, posterior temporal lobe and in some early involvement of descending cortical spinal tract with gadolinium enhancement and diffusion abnormalities (Figure 1).
Neuropsychological results before HSCT indicated severe visual spatial impairment, moderate coordination, auditory memory and attention problems with average verbal reasoning.
All three patients received allogeneic HSCT with NAC for severe ALD, defined as PIQ <80 and Loes score >14 (Table 1). Transplant protocols were approved by institutional review board, and informed consent was obtained in all cases before the procedure. Follow-up is reported through October 2006. As patients with advanced ALD, it was anticipated that they would be at very high risk for dying with a standard regimen. Thus, they received NAC 140 mg/kg/day intravenously (i.v.) followed by 70 mg/kg four times daily orally. When mucositis developed after HSCT, the NAC was administered i.v. at the same dosing schedule (70 mg/kg four times daily). The treatment with NAC was initiated following their initial evaluation at the University of Minnesota, with a range of 54–67 days before HSCT, and discontinued 114–250 days after HSCT.
One patient received stem cell infusions derived from matched related donor bone marrow (patient 1). Two patients received an unrelated donor umbilical cord blood utilizing two cord blood grafts; the first received units matched at four of six and five of six human leukocyte antigen (HLA) antigens (patient 2) and the other received two cord blood units matched at four of six HLA antigens (patient 3).
The preparative regimen consisted of busulfan 0.8 mg/kg i.v. four times daily for 4 consecutive days (days −9 and −6; total dose 12.8 mg/kg), cyclophosphamide 50 mg/kg once daily i.v. for four consecutive days (days −4 to −1; total dose 200 mg/kg), horse antithymocyte globulin (ATGAM) 30 mg/kg once daily i.v. for 3 consecutive days (days −3 to −1; total dose 90 mg/kg). To potentially reduce brain demyelination and inflammation while waiting for transplant, patient 1 received alemtuzumab (Campath-1 H) 0.3 mg/kg once daily for 3 consecutive days (days −41 to −43; total dose 0.9 mg/kg). All patients received cyclosporine and mycophenolate mofetil for graft-versus-host disease prophylaxis.
Hematopoietic chimerism was assessed on peripheral blood leukocyte DNA by competitive polymerase chain reaction analysis of variable tandem repeat regions.15
A comparison group for analysis of survival consisted of all boys transplanted at the University of Minnesota with PIQ <80 and MRI Loes score >14 under the age of 18 years treated with HSCT before November 2005 (N=8).
Patient donor graft characteristics and transplant outcomes are summarized in the Table 1. The median age at HSCT was 10.2 years (range, 10.1–10.3 years). Donor engraftment (defined as donor chimerism of 95–100%) was observed in all three patients. Significant transplant related morbidity consisted of the following: hemorrhagic cystitis (patients 1, 2 and 3); engraftment syndrome responsive to steroids (patient 2); and spasticity and upper airway edema requiring 10 days of assisted ventilation (patient 3).
From a functional standpoint, all boys are wheelchair bound 6–9 months after transplant. Patient 1 can follow limited commands. Patient 2 has limited expressive language and can follow commands. Patient 3 is able to sit independently, can stand and take steps with support. He uses a communicative device. Auditory comprehension is good, and he follows commands in a consistent manner. He can read and his vision is similar to before transplant. He is continent of bowel and bladder, and can walk with assistance from one person.
All three patients had stable disease as evidenced by brain MRI findings 6 months after HSCT (representative images are shown in Figure 1).
Patients in the comparison group (defined as PIQ <80 and Loes score >14; N=8) all died within the first year after HSCT despite full donor engraftment HSCT4 (Figure 2). A test for the equality of the survival distributions using log-rank statistic was significant (3.91, df=1, P<0.05).
Our findings suggest that peri-transplant administration of NAC is protective from fulminant demyelination in advanced, symptomatic ALD, presumably because of its antioxidant and radical scavenging properties. This observation has important therapeutic implications, because there is an urgent need for effective therapy for advanced cerebral ALD patients who are not candidates for standard HSCT because of disease progression.
All three boys initially presented with rapidly progressing visual or auditory deficits, which continued to worsen during and shortly after HSCT. Currently, they appear to be stable clinically and by MRI. As ALD is associated with oxidative damage, we aimed to halt rapid neurologic decline observed in such patients with advanced disease with an adjunctive therapy with an antioxidant agent, NAC. In support of this concept, NAC has been shown to protect neurons from apoptosis in experimental models of neurodegenerative conditions (e.g., multiple sclerosis, experimental autoimmune encephalitis, Alzheimer's and Parkinson's diseases.16, 17, 18, 19, 20
NAC has been used clinically as an inhalational mucolytic agent in bronchopulmonary illnesses including cystic fibrosis, and as an antidote for liver injury from acute acetaminophen toxicity.21 This is important, since several decades of toxicity data established that NAC administration is safe (even with long-term use). Aside from one episode of acute nausea after the first intravenous dose and the unpleasant odor of the suspension during oral administration, we have not observed any adverse reactions related to NAC. Clearly, further studies will be needed to determine the optimal timing and dose of NAC. In addition, it will be important to explore to what degree it benefits neurologic outcomes of patients with advanced ALD (or early ALD), and whether it has any role in ALD outside of an adjunct to transplantation. Another important issue relates to whether the protective effects of NAC would be important in transplantation for other inherited neurological disorders such as globoid cell leukodystrophy or metachromatic leukodystrophy. Although the biology of these diseases is distinct, apoptosis and neuroinflammation may be important in these disorders as well.22, 23 Nevertheless, the novel results reported here add to the accumulating evidence that cerebral ALD pathophysiology is characterized, in part at least, by oxidative damage.
These data suggest that NAC, a drug already in clinical use, merits investigation as a therapeutic strategy for patients with advanced ALD and has a potential to change this lethal disease to a condition amendable to treatment with HSCT.
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The rationale for the use of NAC in this study was prompted by a phone call from J Powers, MD (University of Rochester School of Medicine and Dentistry, Department of Pathology and Laboratory Medicine, Rochester, NY, USA) in July, 2005. This study was supported by the Children's Cancer Research Fund.
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Tolar, J., Orchard, P., Bjoraker, K. et al. N-acetyl-L-cysteine improves outcome of advanced cerebral adrenoleukodystrophy. Bone Marrow Transplant 39, 211–215 (2007). https://doi.org/10.1038/sj.bmt.1705571
- peroxisomal disorder
- hematopoietic stem cell transplantation
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