Chemical stabilities and biological activities of thalidomide and its N-alkyl analogs

PURPOSE. To determine whether the N-alkyl analogs of the thalidomide are active and stable, their stabilities in buffer and their abilities to inhibit tumor necrosis factor alpha (TNF-alpha) in vitro in human peripheral blood mononuclear cell cultures were investigated.

TNF-alpha concentrations were determined with the aid of ELISA kits. Chemical stabilities of the compounds were determined in three phosphate buffer solutions (pH 6, 6.4, and 7.4) at 25 and 32 degrees C by high-pressure liquid chromatography, and half-lives were calculated.

The addition of N-alkyl groups to the glutarimide ring of the thalidomide molecule had little effect on the ability such compounds have to inhibit TNF-alpha production. There was no statistical difference between the activity of thalidomide and its N-alkyl analogs at a 95% confidence level. Like thalidomide, the N-alkyl analogs in this series inhibit an average of 60% of the TNF-alpha synthesis in lipopolysaccharide-stimulated peripheral blood mononuclear cell cultures. Thalidomide and its N-alkyl analogs are hydrolyzed at very similar rates, with half-lives ranging from 25 to 35 h at 32 degrees C at pH 6.4 and an average rate constant of 2.35 x 10(-2)/h.

Alkylating thalidomide had little effect on its ability to inhibit the production of TNF-alpha in these cell cultures. All of the compounds tested seem to have some, perhaps comparable, therapeutic potential.