An antitumor osteotropic agent based on tumor necrosis factor

Abstract

An osteotropic agent based on the human recombinant tumor necrosis factor alpha (TNF-alpha) has been designed for treatment of bone metastases. It represents a molecular construct containing yeast double- stranded ribonucleic acid (dsRNA) covered by the conjugate of polyanion dextran with TNF-alpha and bisphosphonate alendronic acid. This construct is characterized by the combination of substances possessing antitumor activity (TNF-alpha, dsRNA) and a vector molecule (bisphosphonate) providing tropism to hydroxyapatite, the main mineral component of the bone tissue matrix. The conjugation conditions were optimized and the conjugates of TNF-alpha and alendronic acid with dextran were synthesized. The molecular constructs were obtained by self-assembly, and the resultant complexes were separated by gel filtration on Sepharose CL-6B. The electrophoretic analysis has shown decreased mobility of dsRNA in the complex with the conjugate as compared to mobility of the original dsRNA. This confirms formation of the designed structures. Transmission electron microscopy confirmed the presence of particles with sizes of 30–40 nm in the drug preparation. Evaluation by the sorption/desorption method showed a higher affinity of TNF-alpha conjugates to hydroxyapatite as compared to original TNF-alpha molecules (from 1.0–1.8 mol/L vs. 0.3 mol/L of potassium phosphate buffer for desorption, respectively).