Synthesis, Structural and Biochemical Characterization of Cytostatic Methotrexate-γ-Glutamyl-Glutathione Conjugates

Abstract

The synthesis and pharmacological evaluation of methotrexate (MTX) derivatives with the aim of obtaining modified cellular uptake and transport properties, and cytostatic activity has been subject to intensive studies in the last years ¹. Among several approaches, modifications at the γ-glutamyl residue of MTX have been carried out both by covalent attachment of oligopeptides^2,3 and lipid moieties⁴, the latter adducts being able to form defined supramolecular structures. Based on previous work by Leszcynska and Pfaff who observed a significantly enhanced uptake of MTX in hepatocytes in the presence of extracellular glutathione (GSH)⁵, we have synthesized a series of covalent MTX-glutathionyl peptide conjugates. In the present study, an efficient synthetic pathway, structural and initial biochemical characterization data of MTX-y-glutamyl-GSH derivatives are described. The surprisingly high in vitro dihydrofolate reductase (DHFR) inhibitory activity found indicates these derivatives to be potentially interesting new cytostatic antifolates³.