Enhancement of the brain delivery of methotrexate with administration of mid-chain ester prodrugs: In vitro and in vivo studies.

In the present study, with the aim of improving the permeability of methotrexate (MTX) to the brain, the lipophilic MTX prodrugs containing the ester functional moiety were synthesized. The chemical structure of synthesized prodrugs was characterized and confirmed by FT-IR, NMR and mass spectral studies. Based on the results of in vitro cytotoxic studies, all of the synthesized prodrugs led to decrease in the IC50 in 72 h on U87 cancer cell line and the best result was observed for dihexyl methotrexate (MTX-DH) in comparison with free MTX, which led to decrease the IC50 amount up to 6 folds. In addition, in vivo toxicity on Artemia salina (A. salina) showed that the lipophilic MTX prodrugs have been able to partially mask the toxic profile of free MTX, at the same concentrations. These findings were also in compliance with hemolysis assay results, which confirm that the conjugates has not made the drug more toxic. Furthermore, in vivo study in rat model, was employed to determine the simultaneous drug concentration in brain and plasma. According to the obtained results, the brain-to-plasma concentration ratios (Kp values) of MTX-DH and dioctyl methotrexate (MTX-DO) groups were significantly higher compared with free MTX. Moreover, the uptake clearance of MTX by brain parenchyma increased significantly (3.85 and 9.08-time increased for MTX-DH and MTX-DO prodrugs, respectively). These findings indicate that the synthesized lipophilic MTX prodrugs are non-toxic and able to enhance brain penetration of MTX.