Permeation through BBB endothelium Transport assays were performed in transwells (24-well format) on an orbital shaker (Edmund Bühler GmbH, Germany) at 100 rpm, 37 °C, 95 % humidity, and 5 % CO 2 . Stock solutions of A-pBuOzi-A/ATV or DMSO/ATV were diluted with human endothelial-SFM (Thermo Fisher Scientific, USA) containing 1 % platelet poorplasma derived serum (PPPDS; Alfa Aesar, USA) to the desired concentrations ([ATV] = 90 µM and 150 µM). Test concentrations of A-pBuOzi-A/ATV or DMSO/ATV (200 µL) were applied to the apical side of the BBB model. The basolateral side was supplied with 800 µL of human endothelial-SFM containing 1 % PPPDS and the respective concentration of sterile water (A-pBuOzi-A) or DMSO. The permeation was evaluated after incubation times of 4 h and 24 h. Apical and basolateral media were analyzed by HPLC to quantify the transport of A-pBuOzi-A/ATV or DMSO/ATV. As control, the substances were incubated on empty collagen IV-/fibronectin-coated inserts to exclude major ATV adsorption on the membrane. All permeability studies were performed in duplicates and three independent biological replicates, results are presented as means ± SD. The level of statistical significance was set at p<0.05, indicated with asterisk (*). Grading in significance is indicated as follows: *p<0.05, **p<0.01, ***p<0.001.