Oral cysteamine bitartrate and N-acetylcysteine for patients with infantile neuronal ceroid lipofuscinosis: a pilot study

Abstract

Background: Infantile neuronal ceroid lipofuscinosis is a devastating neurodegenerative lysosomal storage disease caused by mutations in the gene (CLN1 or PPT1) encoding palmitoyl-protein thioesterase-1 (PPT1). We have previously reported that phosphocysteamine and N-acetylcysteine mediate ceroid depletion in cultured cells from patients with this disease. We aimed to assess whether combination of oral cysteamine bitartrate and N-acetylcysteine is beneficial for patients with neuronal ceroid lipofuscinosis.

Methods: Children between 6 months and 3 years of age with infantile neuronal ceroid lipofuscinosis with any two of the seven most lethal PPT1 mutations were eligible for inclusion in this pilot study. All patients were recruited from physician referrals. Patients received oral cysteamine bitartrate (60 mg/kg per day) and N-acetylcysteine (60 mg/kg per day) and were assessed every 6-12 months until they had an isoelectric electroencephalogram (EEG, attesting to a vegetative state) or were too ill to travel. Patients were also assessed by electroretinography, brain MRI and magnetic resonance spectroscopy (MRS), and electron microscopic analyses of leukocytes for granular osmiophilic deposits (GRODs). Children also underwent physical and neurodevelopmental assessments on the Denver scale. Outcomes were compared with the reported natural history of infantile neuronal ceroid lipofuscinosis and that of affected older siblings. This trial is registered with ClinicalTrials.gov, number NCT00028262.

Findings: Between March 14, 2001, and June 30, 2012, we recruited ten children with infantile neuronal ceroid lipofuscinosis; one child was lost to follow-up after the first visit and nine patients (five girls and four boys) were followed up for 8 to 75 months. MRI showed abnormalities similar to those in previous reports; brain volume and N-acetyl aspartic acid (NAA) decreased steadily, but no published quantitative MRI or MRS studies were available for comparison. None of the children acquired new developmental skills, and their retinal function decreased progressively. Average time to isoelectric EEG (52 months, SD 13) was longer than reported previously (36 months). At the first follow-up visit, peripheral leukocytes in all nine patients showed virtually complete depletion of GRODs. Parents and physicians reported less irritability, improved alertness, or both in seven patients. No treatment-related adverse events occurred apart from mild gastrointestinal discomfort in two patients, which disappeared when liquid cysteamine bitartrate was replaced with capsules.

Interpretation: Our findings suggest that combination therapy with cysteamine bitartrate and N-acetylcysteine is associated with delay of isoelectric EEG, depletion of GRODs, and subjective benefits as reported by parents and physicians. Our systematic and quantitative report of the natural history of patients with infantile neuronal ceroid lipofuscinosis provides a guide for future assessment of experimental therapies.

Funding: National Institutes of Health.

Conflict of interest statement

Conflicts of Interest

All authors declare that they have no conflicts of interest.

Copyright © 2014 Elsevier Ltd. All rights reserved.

Figures

Figure 1. Progression of cerebral atrophy in a single subject (Patient 8)

All images are axial T1 weighted images acquired in the plane defined by the anterior commissure and posterior commissure. Age (in years) is noted adjacent to each image. Atrophy progressed rapidly between ages 1.2 yrs and 2.6 yrs, with gradual changes thereafter. This trajectory was typical for the patients in this study. Gray matter loss proceeded rapidly, and gray matter was not clearly identified after 2.6 yrs in this patient. Signal abnormalities in the deep nuclei progressed as follows: first the thalamus became hyperintense relative to white matter, then the globus pallidus, and finally the putamen and caudate.

Figure 2. Progression of MRS abnormalities in a single subject (Patient 8)

All spectra are on the same scale (equal area for equal mM NAA), and have been corrected for T1 decay, T2 decay and CSF partial volume. NAA (mM) in tissue is noted next to the NAA peak. Cysteamine bitartrate-N-acetylcysteine combination treatment was initiated shortly after the examination at 2.6 yr. Abnormalities are most severe in the cerebral gray matter. Decline in the thalamus and cerebellum is slower than in the cerebrum. Progression of abnormalities is slowest in the pons. NAA demonstrates a steady decline at all locations. Cr = creatine, Ins = myo-inositol, Cho = choline, Glx = glutamine+glutamate+GABA, NAA = N-acetyl aspartic acid, Lac = lactate.

Figure 3. Electroretinographic recordings from two representative study patients

A. Patient 7 presented at the earliest age (10 m) and had the best preserved response amplitudes among all study patients at that visit. The follow-up visit for Patient 7 was at the age of 19.0 m and by that time her recordings showed the characteristic findings expected in INCL including significantly reduced b-wave amplitude on both the rod response and the scotopic combined (rod-cone) response. Note the electronegative waveform on the combined response at the 19.0 m follow-up visit (but not on initial presentation). B. Patient 1 had multiple study follow-ups with the ERG showing progressive reduction in amplitude across all recorded responses. Note that, for all study patients, the scotopic responses were more severely affected and showed earlier changes than the photopic responses.

Figure 4. Electron microscopic analysis of GRODs in leukocytes before and after treatment

Transmission electron microscopic analyses of peripheral WBCs from all patients were performed at all patient visits, both pre-treatment and post-treatment. GRODs are irregularly-shaped dark extranuclear structures that are distinct from mitochondria, secretory granules, and other membrane–enclosed cellular organelles. Representative micrographs (A) from a patient are shown at 3 time points (pre-treatment and two post-treatment). Note that GRODs are readily detectable only in the pre-treatment image. Arrows indicate GRODs; M, mitochondria; N, nucleus. Number of GRODs per cell (B) and area of the GRODs (C) for all 9 patients together are shown as they evolved over time. For all patients, both the number and size of the GRODs declined over time, starting with the first visit after initiation of treatment.