Vitamin B12 as a Vector for the Transport of Drugs to the Tumor

Studies of various aspects of the action of vitamin B12 bring interesting, often unexpected, results and open up new prospects for their practical application. The review focuses on recent advances in the use of natural cobalamins and their synthetic analogues in medical practice as vectors for targeted drug delivery to tumors. Particular attention is paid to the rationale for the use of corrinoids in this area in terms of their biodistribution and metabolism in the hu-man body. The most common in nature cobalamins and a number of the most important synthetic derivatives of vita-min B12, the absorption and distribution of cobalamins, the main functions of vitamin B12 in the cell, general ap-proaches to bioorthogonal (i.e., preserving the biological functions of the molecule) modification, as well as consid-eration of sites in the structure of this compound, which are most suitable for conjugation, are successively discussed. The use of corrinoids for the diagnosis of tumors and drug delivery is considered separately. Examples of the synthe-sis of conjugates of cobalamins and various low molecular weight drugs, as well as proteins and oligonucleotides and targeted transport of the resulting compounds in tumors are analyzed. In conclusion, examples of the use of co-balamins as promising vectors for various colloidal delivery systems, including micro and nanoparticles, are given. The obtained results testify to the prospects of this direction. Of particular importance to the authors is the develop-ment of cobalamin-vectored drug delivery vehicles for chemotherapy of tumors, for which an increased expression of vitamin B12 transport proteins is observed.