Endogenous, non-reducing end glycosaminoglycan biomarkers are superior to internal disaccharide glycosaminoglycan biomarkers for newborn screening of mucopolysaccharidoses and GM1 gangliosidosis.

Measurement of enzymatic activity in newborn dried blood spots (DBS) is the preferred first-tier method in newborn screening (NBS) for mucopolysaccharidoses (MPSs). Our previous publications on glycosaminoglycan (GAG) biomarker levels in DBS for mucopolysaccharidosis type 1 (MPS-I) and MPS-II demonstrated that second-tier GAG biomarker analysis can dramatically reduce the false positive rate in NBS. In the present study, we evaluate two methods for measuring GAG biomarkers in seven MPS types and GM1 gangliosidosis. We obtained newborn DBS from patients with MPS-IIIA-D, -IVA, -VI, -VII, and GM1 gangliosidosis. These samples were analyzed via two GAG mass spectrometry methods: (1) The internal disaccharide biomarker method; (2) The endogenous non-reducing end (NRE) biomarker method. This study supports the use of second-tier GAG analysis of newborn DBS by the endogenous NRE biomarker method, as part of NBS to reduce the false positive rate.

GM1-gangliosidosis: The caregivers' assessments of symptom impact and most important symptoms to treat.

GM1-gangliosidosis (GM1) is a rare neurodegenerative disorder leading to early mortality and causing progressive decline of physical skills and cerebral functioning. No approved treatment for GM1 exists. In this study-the first to explore priorities of parents of subjects with pediatric onset forms of GM1-we address a crucial gap by characterizing symptoms most critical to caregivers of children with GM1 to treat. Our two-part, mixed-methods approach began with focus groups, followed by interviews with a distinct set of parents. Interviews included a prioritization activity that used best-worst scaling. Quantitative data were analyzed descriptively. Qualitative data were analyzed using thematic analysis and rapid analysis process. Parents prioritized the symptoms they believed would increase their child's lifespan and improve their perceived quality of life (QoL); these symptoms focused on communicating wants/needs, preventing pain/discomfort, getting around and moving one's body, and enhancing eating/feeding. Although lifespan was highly valued, almost all parents would not desire a longer lifespan without acceptable child QoL. Parents indicated high caregiver burden and progressive reduction in QoL for children with GM1. This novel study of caregiver priorities identified important symptoms for endpoints' selection in patient-focused drug development in the context of high disease impact and unmet treatment needs.

Detection of GM1-gangliosidosis in newborn dried blood spots by enzyme activity and biomarker assays using tandem mass spectrometry.

GM1-gangliosidosis is a rare autosomal recessive lysosomal storage disease caused by deficiency of ß-galactosidase (GLB1). Newborn screening (NBS) may be warranted in the near future given the initiation of a number of gene therapy clinical trials. Here, we report a tandem mass spectrometry (MS/MS) enzymatic assay of GLB1 using dried blood spots (DBS), and the demonstration that GLB1 activities in newborn DBS from seven GM1-gangliosidosis patients are well below those measured in random newborn DBS. MS/MS analysis of two glycan biomarkers, dp5 and A2G2, shows high elevation in newborn DBS from GM1-gangliosidosis compared to the levels in the nonaffected reference range.