[39] Although stability of the aqueous A-pBuOzi-A/ATV formulations up to ATV feeds of 8 g/L was reasonably good, a minor loss in ATV content occurred in all formulations within 30 d storage (Figure ). Shelf-life of drug-loaded micelles can potentially be increased by freeze-drying the aqueous formulations and redispersing them right before usage. POx and POzi based formulations of PTX or CUR have already displayed excellent redispersibility without the need of cryoprotectants. Similar, freeze-dried A-pBuOzi-A/ATV = 10/2 g/L formulations could be conveniently redispersed in H 2 O (Figure blue), PBS (red) or PBS containing 40 g/L bovine serum albumin (BSA, green) after 7 d storage of the freeze-dried formulations at ambient conditions. Redispersion in PBS containing 40 g/L BSA corresponding to the albumin concentration in blood was performed as preliminary test for upcoming in vitro and potential in vivo studies, as initially stable formulations can precipitate in the presence of proteins. The excellent stability in the presence of serum protein suggests that this formulation may be safely injected i.v. 2D in vitro studies Cytotoxicity of A-pBuOzi-A/ATV or ATV dissolved in DMSO against mouse glioma cells GL261 and CT-2A or human glioblastoma cells U87, U251 and U373 was evaluated after 24 h, 48 h and 72 h incubation (Figure ). To the best of our knowledge, a potential growth inhibition or cytotoxicity of ATV against GL261, CT-2A and U373 has not previously been investigated. Except for CT-2A, cytotoxicity after 24 h incubation was moderate with half maximal inhibitory concentrations (IC 50 ) of 97 µM and higher. A similar low cytotoxicity of ATV after 24 h incubation (no decrease in proliferation up to [ATV] = 50 µM) compared to 48 h and 72 h was observed for human leukemic natural killer cells YT-INDY. Furthermore, absence of cytotoxicity against U87 after 24 h incubation at [ATV] ≤ 100 µM was also observed by Yongjun et al. In contrast, ATV exhibits a pronounced dose-dependent cytotoxicity after 48 h and 72 h incubation. The IC 50 values for A-pBuOzi-A/ATV and DMSO/ATV were either comparable (U87 (72 h); U373 (48 and 72 h)) or slightly lower for A-pBuOzi-A/ATV. Generally, cytotoxicity increased from 48 h to 72 h incubation. Only for CT-2A, an unexpected increase in cell viability with IC 50 values increasing from 33 µM (48 h) to 98 µM (72 h) occurred for DMSO/ATV. Furthermore, biphasic dose-response curves occurred in selected cases for DMSO/ATV (GL261) as well as A-pBuOzi-A/ATV (U251). Such multiphasic features are well known in cancer pharmacology due to the presence of combined agonist (stimulatory or hormetic )