PROBLEM TO BE SOLVED: To provide an oligonucleotide-modified nucleic acid body containing 1-β-D-arabinofuranosylcytosine, which is a modified nucleic acid having therapeutic efficacy, and guanosine. SOLUTION: A novel oligonucleotide-modified nucleic acid body containing one or more therapeutically effective modified nucleic acid (N) and abundant guanosine (G) is synthesized, and the oligonucleotide-modified nucleic acid body is a hematological cancer cell and a drug. It was confirmed that it has excellent cell killing activity against resistant hematological cancer cells, and based on this, prevention and improvement of hematological cancer containing the modified nucleic acid body or a pharmaceutically acceptable salt thereof as an active ingredient. Alternatively, a therapeutic composition is provided. [Selection diagram] Figure 1【課題】治療効能を持つ修飾核酸である１－β－Ｄ－アラビノフラノシルシトシン（１－β－Ｄ－Ａｒａｂｉｎｏｆｕｒａｎｏｓｙｌｃｙｔｏｓｉｎｅ）及びグアノシンを含有するオリゴヌクレオチド修飾核酸体を提供する。【解決手段】１つ以上の治療効能を持つ修飾核酸（Ｎ）と豊富なグアノシン（Ｇ）が含まれた新規オリゴヌクレオチド修飾核酸体を合成し、該オリゴヌクレオチド修飾核酸体が血液癌細胞及び薬物抵抗性血液癌細胞に対して優れた細胞死滅活性を有することを確認し、これに基づいて、前記修飾核酸体又はその薬学的に許容可能な塩を有効成分として含有する血液癌の予防、改善又は治療用組成物を提供する。【選択図】図１
