Fig. 1: Gene dosage and correlations with demyelinating lesion growth in CALD.

a Representative images of T2-weighted (T2W) and fractional anisotropy (FA) maps of a patient with CALD before (PRE), 1 and 2 years post successful gene therapy (GT). Magnifications illustrate the progress of the T2W lesion and structural tissue reorganization on FA maps primarily within the first year and only minor changes in the second year. b Schematic illustrations of microvascular vulnerability caused by ABCD1 deficiency. Loss of ABCD1 function in hemizygotes leads to altered interactions of leukocytes and brain-endothelium. Compared to healthy flow conditions (1), this causes increased flow heterogeneity and BBB-permeability within capillary beds (2) and precedes conversion to CALD exacerbated by a yet unknown “second hit” (red). As the CALD manifests, flow heterogeneity and BBB-permeability exacerbate (3). The degree of leukocyte-to-brain-endothelial cell interaction is thought to affect microcirculation causing flow disturbances and shunting in the capillary bed, impairing vascular efficacy (4). c Longitudinal data for T2W lesion volume (top) and mean lesional FA (bottom) of GT-treated patients (n = 15). For each row left, diagram shows the longitudinal course and right diagram shows relative monthly change in lesion volume and FA PRE to visit 1 (1–2 Mo) and within the first and second-year follow-up (1–12 Mo, 12–24 Mo) post treatment. Blue lines indicate individual, black line represents mean change. Welch’s ANOVA between-group difference P = 0.0004 and P < 0.0001. The P values were determined by Dunnett’s multiple comparison test. d Individual Vector copy number (VCN) in the GT product before infusion (green) and in the peripheral blood (blue) for each patient at follow-up after Infusion (n = 11–15, dotted line connects median; error bars indicate interquartile range). e Plot showing the relationship of VCN in the GT product and T2W lesion growth over 2 years (n = 9, two outliers removed, simple linear regression). f Plot showing the relationship of VCN in the GT product and FA decreases over two years (n = 11, simple linear regression). g Logistic regression curve representing an estimate of the probability of delayed T2W lesion growth depending on VCN in the peripheral blood at 12 months (yes vs. no increase V1-12 months, χ²[1] = 7.88, p = 0.037, Pseudo R² = 0.41, Exp(B) = 0.003, 95% CI 0.001–0.707, n = 15). Source data are provided as a Source Data file.