Carborane-Containing Folic Acid bis -Amides: Synthesis and In Vitro Evaluation of Novel Promising Agents for Boron Delivery to Tumour Cells.

The design of highly selective low-toxic, low-molecular weight agents for boron delivery to tumour cells is of decisive importance for the development of boron neutron capture therapy (BNCT), a modern efficient combined method for cancer treatment. In this work, we developed a simple method for the preparation of new closo - and nido -carborane-containing folic acid bis -amides containing 18-20 boron atoms per molecule. Folic acid derivatives containing nido -carborane residues were characterised by high water solubility, low cytotoxicity, and demonstrated a good ability to deliver boron to tumour cells in in vitro experiments (up to 7.0 µg B/10 6 cells in the case of U87 MG human glioblastoma cells). The results obtained demonstrate the high potential of folic acid- nido -carborane conjugates as boron delivery agents to tumour cells for application in BNCT.