Transport of treosulfan and temozolomide across an in-vitro blood–brain barrier model

Abstract

In vitro, treosulfan (TREO) has shown high effectiveness against malignant gliomas. However, a first clinical trial for newly diagnosed glioblastoma did not show any positive effect. Even though dosing and timing might have been the reasons for this failure, it might also be that TREO does not reach the brain in sufficient amount. Surprisingly, there are no published data on TREO uptake into the brain of patients, despite extensive research on this compound. An in-vitro blood-brain barrier (BBB) model consisting of primary porcine brain capillary endothelial cells was used to determine the transport of TREO across the cell monolayer. Temozolomide (TMZ), the most widely used cytotoxic drug for malignant gliomas, served as a reference. An HPLC-ESI-MS/MS procedure was developed to detect TREO and TMZ in cell culture medium. Parallel to the experimental approach, the permeability of TREO and the reference substance across the in-vitro BBB was estimated on the basis of their physicochemical properties. The detection limit was 30 nmol/l for TREO and 10 nmol/l for TMZ. Drug transport was measured in two directions: influx, apical-to-basolateral (A-to-B), and efflux, basolateral-to-apical (B-to-A). For TREO, the A-to-B permeability was lower (1.6%) than the B-to-A permeability (3.0%). This was in contrast to TMZ, which had higher A-to-B (13.1%) than B-to-A (7.2%) permeability values. The in-vitro BBB model applied simulated the human BBB properly for TMZ. It is, therefore, reasonable to assume that the values for TREO are also meaningful. Considering the lack of noninvasive, significant alternative methods to study transport across the BBB, the porcine brain capillary endothelial cell model was efficient to collect first data for TREO that explain the disappointing clinical results for this drug against cerebral tumors.

Penetration of Treosulfan and its Active Monoepoxide Transformation Product into Central Nervous System of Juvenile and Young Adult Rats

“…However, the efflux ratio for TREO (1.88) did not reach the threshold for recognition of P-gp substrates, that is 2, and no concentration dependency of the drug distribution was observed. Therefore, involvement of the active efflux mechanisms in elimination of TREO from brain in vivo remains an open question (Linz et al, 2015). If that is the case, the higher brain exposure to TREO in the 10-day-old JR, in which the P-gp expression at BBB could be several times lower than in the 34-to 35-day-old YAR (Gazzin et al, 2008;Ose et al, 2008), is not surprising.…”

“…In fact, all molecules enter from blood to CSF at a rate inversely related to molecular weight (MW), which explains why S,S-EBDM (MW 182 Da) penetrated into the rat CSF better than TREO (MW 278 Da) (Nau et al, 2010;Tam and Watts, 2010;Pardridge, 2012). As TREO may be a substrate for the efflux transporters, it is also worth mentioning that P-gp substrates, which cannot be found in appreciable concentrations in brain, typically penetrate into CSF (Linz et al, 2015).…”

Population pharmacokinetic approach for evaluation of treosulfan and its active monoepoxide disposition in plasma and brain on the basis of a rat model

“…Several studies provide data on the blood-brain transport of treosulfan and EBDM. In an in vitro study, Linz et al found that transport of treosulfan in the apical-to-basolateral direction (influx) is lower than the basolateral-to-apical (efflux), with permeability values of 1.6% and 3.0%, respectively [39]. The authors have also calculated a small logBB value (− 1.98), upon the ratio of treosulfan concentrations in brain and plasma.…”

Bone Marrow-Derived Cell Accumulation in the Spinal Cord Is Independent of Peripheral Mobilization in a Mouse Model of Amyotrophic Lateral Sclerosis

“…Based upon its hydrophilicity, TREO would not be predicted to readily cross the BBB and gain access to the CNS. In support of this claim, little penetrance of TREO and its active metabolites were detectable within the CNS of rats administered 500 mg/kg TREO, and limited amounts of TREO crossed an in vitro BBB model (20, 21). Virtually, all of the BMDCs detectable in TREO-conditioned mice had morphologies suggesting blood vessel-associated localizations (Table 1).…”

“…Treosulfan (TREO; Medac, DE), a hydrophilic analog of BU that does not readily cross the BBB (20, 21), was resuspended in sterile ddH 2 O at a concentration of 50 mg/mL just prior to administration. Doses were selected based upon previous studies by Van Pel et al and Nasa et al (22, 23).…”