Therefore, although no conclusion can be made after only eight weekly ICV doses of rhβ-gal in GLB1 KO mice, our biomarker analysis of glycan substrate accumulation in human GM1 gangliosidosis patients,4 together with the results in a limited number of animals shown here, warrant further studies to investigate the potential of A2G2′ glycan as a noninvasive biomarker of rhβ-gal systemic exposure and substrate turnover during ICV-ERT clinical trials. The gene discussed is GLB1; the disease is GM1 gangliosidosis.