I am currently conducting research to develop a novel chemically-modified nucleoside analogue and to characterize its functions with the goal of applying it to antisense nucleic acid, a type of nucleic acid drug. During my undergraduate studies, my co-researchers and I designed and synthesized two thymidine analogues: (S)-5′-C-aminopropyl-thymidine and (S)-5′-C-aminopropyl-2′-arabinofluoro-thymidine. In addition, we characterized the physical and biochemical functions of oligonucleotides containing these analogues. We found that nucleoside analogs with (S)-5′-C-aminopropyl-2′-arabinofluoro modifications are relatively useful for therapeutic applications. In the CIBoG program, I will conduct research to optimize the introduction positions for nucleoside analogues and then synthesize new nucleosides with (S)-5′-C-aminopropyl-2′-arabinofluoro modifications, building on my undergraduate work. Basic research on nucleic acid drugs is considered to be useful for establishing a platform of nucleic acid drugs with excellent properties. I hope I can be involved in developing novel individualized nucleic acid drugs, particularly for cancer treatment.