GFAP and Hereditary diffuse leukoencephalopathy with axonal spheroids and pigmented glia: Biochemical assays of levels of various soluble biomarkers in CSF (tau proteins, NfL proteins and glial fibrillary acidic protein) and in plasma (NfL) of ALSP patients may serve as meaningful surrogate endpoints for clinical trials (14, 20, 24, 40, 67, 86).