Biomarkers of central nervous system inflammation in infantile and juvenile gangliosidoses.

BACKGROUND: The gangliosidoses (Tay-Sachs disease, Sandhoff disease, and GM1-gangliosidosis) are progressive neurodegenerative diseases caused by lysosomal enzyme activity deficiencies and consequent accumulation of gangliosides in the central nervous system (CNS). The infantile forms are distinguished from the juvenile forms by age of onset, rate of disease progression, and age of death. There are no approved treatments for the gangliosidoses. In search of potential biomarkers of disease, we quantified 188 analytes in CSF and serum from living human patients with longitudinal (serial) measurements. Notably, several associated with inflammation were elevated in the CSF of infantile gangliosidosis patients, and less so in more slowly progressing forms of juvenile gangliosidosis, but not in MPS disease. Thirteen CSF and two serum biomarker candidates were identified. Five candidate biomarkers were distinguished by persistent elevation in the CSF of patients with the severe infantile phenotype: ENA-78, MCP-1, MIP-1α, MIP-1ß, and TNFR2. Correspondence of abnormal elevation with other variables of disease-i.e., severity of clinical phenotype, differentiation from changes in serum, and lack of abnormality in other neurodegenerative lysosomal diseases-identifies these analytes as biomarkers of neuropathology specific to the gangliosidosis diseases.

START, a double blind, placebo-controlled pharmacogenetic test of responsiveness to sapropterin dihydrochloride in phenylketonuria patients.

UNLABELLED: Sapropterin dihydrochloride, a synthetic tetrahydrobiopterin (BH4), works as a chaperone of phenylalanine hydroxylase (PAH) in phenylketonuria (PKU) to facilitate and stabilize folding of PAH into its most active conformation. No standard pharmacogenetic tests exist to identify responsive genotypes. Previous studies have failed to identify genotypes that consistently predict response; they are weakened by varied: 1) doses; 2) response definitions; 3) duration; 4) phenylalanine (PHE) test times during different protein catabolic states; 5) control of dietary PHE. START (sapropterin therapy actual response test) protocol is a double blind, placebo-controlled, 4-week clinical test that obviates the confounders aforementioned. START results were evaluated for response-genotype correlates and trends in molecular characteristics. RESULTS: Seventy-four patients completed START. Thirty-six patients (48.6%) responded, 55 patients' genotypes are known, 38 unique genotypes are present. Alleles consistently associated with response include Y414C (8/8 patients, 6 genotypes) and I65T (9/9 patients, 6 genotypes). The p.R408W mutation, in which substitution of straight chain arginine with bulky aromatic amine, tryptophan, at the crux of a strategic hinge site activating folding of PAH, amino acid sequence 408, was strongly associated with non-response (21/29 patients non-responsive, 12/17 genotypes non-responsive). Genotypes containing at least one allele with ≥25% residual activity compared to wild type, were strongly associated with response. CONCLUSIONS: The START protocol provides a rigorous pharmacogenetic test to identify sapropterin responsiveness and genotypes associated with responsiveness and non-responsiveness. Some genotypes were found to be predictive of responsiveness or non-responsiveness, and responsiveness was associated with specific alleles. The START protocol provides a reliable test for sapropterin responsiveness and will continue to improve understanding of how PKU mutations impact PAH protein-folding dynamics and enhance understanding of PKU disease and its management.

Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI): a single dose of galsulfase further reduces urine glycosaminoglycans after hematopoietic stem cell transplantation.

BACKGROUND: Maroteaux-Lamy syndrome, or mucopolysaccharidosis (MPS) type VI, is the autosomal recessive lysosomal disorder resulting from deficient N-acetylgalactosamine 4-sulfatase (ARSB) and the consequent accumulation of glycosaminoglycan (GAG). Patients fully engrafted after hematopoietic stem cell transplantation (HSCT) demonstrate several indicators of metabolic correction such as reduction in liver size, absence of hepatic ultrastructural pathology, and patients do not develop cervical cord compression. Engrafted patients demonstrate reduction in urine GAG achieving near-normal levels. HYPOTHESIS: We presumed that HSCT engraftment from a normal individual would provide sufficient systemic enzyme to accomplish maximal metabolic correction, and that no additional benefit would accrue from additional therapy such as with intravenous recombinant human ARSB protein, galsulfase. MATERIALS AND METHODS: A 22-year-old male had received an allogeneic bone marrow transplant from an HLA-identical sibling donor, and remained fully engrafted after 20 years. In response to his request regarding the potential benefit of enzyme replacement therapy, we administered a single, standard dose of galsulfase while monitoring urine GAG daily, before and after the treatment. RESULTS: Urine GAG declined from slightly high pre-treatment levels (7.63 mg GAG/mmol creatinine; range 7.0-8.5, N=3) progressively declining below the age-specific normal range (<6.5) over 10 days to the lowest level of 4.4, with a mean post-treatment level of 5.60 (N=10). CONCLUSIONS: Somewhat surprisingly, the biomarker urine GAG was significantly reduced after a single treatment of intravenous galsulfase thus suggesting that supplemental enzyme replacement therapy might improve the clinical outcome for donor-engrafted patients with MPS VI.

Delayed Infusion Reactions to Enzyme Replacement Therapies.

BACKGROUND: There are currently ten intravenous enzyme replacement therapy (ERT) products available for the treatment of eight different lysosomal diseases (LD) in the USA. Additional ERT products are in clinical trials. The most common ERT adverse events are infusion reactions (IR). While IR are often defined as hypersensitivity or anaphylactoid reactions occurring concurrently with (i.e., during) infusion administration (CIR), there exists the potential for delayed infusion reactions (DIR), which present after completion of infusion administration. HYPOTHESIS: Concurrent infusion reactions (CIR) are not the only infusion reactions associated with enzyme therapy. METHODS: This study evaluated the occurrence of infusion reactions in 46 patients with LD who had received ERT for a minimum of 2 years. Infusion reactions were evaluated according to symptoms, time of onset, and duration of reactions. The frequency of infusion reactions with each ERT product was compared to that reported in the FDA-approved product package insert. RESULTS AND CONCLUSIONS: In this study, DIR were observed and occurred as often as CIR in the study population, despite not being characterized or reported in most ERT product package inserts. Effective methods for managing DIR and CIR differed, thus emphasizing the importance of monitoring for both types of infusion reactions in order to optimize outcomes for patients using ERT.