The purpose of the present invention is to provide a novel nucleic acid with which [beta]2GPI expression can be inhibited and a pharmaceutical composition for the prevention or treatment of diseases associated with [beta]2GPI expression. The foregoing is achieved by providing an antisense oligonucleotide having [beta]2GPI expression-inhibiting activity, a pharmaceutical composition comprising the antisense oligonucleotide, and a drug that contains the antisense oligonucleotide, inhibits expression of [beta]2GPI, and prevents or treats autoimmune diseases such as APS or SLE and thrombosis during hemodialysis.本發明之目的在於提供一種能夠抑制β2GPI之表現的新穎核酸及用於預防或治療與β2GPI之表現相關之疾病之醫藥組合物。本發明提供具有β2GPI之表現抑制活性之反義寡核苷酸、包含該反義寡核苷酸之醫藥組合物、及包含該反義寡核苷酸之抑制β2GPI之表現的APS、SLE等自體免疫疾病及血液透析之血栓症之預防或治療藥，藉此解決上述問題。
