The purpose of the present invention is to provide a novel miR-143 derivative described herein that can be used as a nucleic acid drug. In the derivative, the first strand is an oligonucleotide comprising the sequence set forth in SEQ ID NO: 3 or a sequence obtained by the substitution, deletion, insertion, or addition of 1 or 2 bases in the sequence set forth in SEQ ID NO: 3, and does not include a 3'-terminal modification, but may include a 5'-terminal modification. The second strand is an oligonucleotide comprising the sequence set forth in SEQ ID NO: 4 or a sequence obtained by the substitution, deletion or insertion of 1 or 2 bases in the sequence set forth in SEQ ID NO: 4, and includes a 3'-terminal modification and may include a 5'-terminal modification. The second strand is alternatively an oligonucleotide comprising the sequence set forth in SEQ ID NO: 5 or a sequence obtained by the substitution or insertion of 1 or 2 bases in the sequence set forth in SEQ ID NO: 5, and which does not include a 3'-terminal modification, and may include a 5'-terminal modification. Here, the 3'-terminal modification is a 1 to 5-mer oligonucleotide derivative that may contain a nucleoside derivative and/or a modified internucleoside bond, or a benzene-pyridine derivative. The 5'-terminal modification is a phosphate site or a group represented by the formula =CQ1-P(=O) (OH)2 (in the formula, Q1 is hydrogen, a halogen, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkenyl, a substituted or unsubstituted alkynyl, or a substituted or unsubstituted alkyloxy).La présente invention décrit un nouveau dérivé d'ARNmi-143 qui peut être utilisé comme médicament acide nucléique. Dans le dérivé, le premier brin est un oligonucléotide comprenant la séquence exposée dans SEQ ID no : 3 ou une séquence obtenue par la substitution, la délétion, l'insertion, ou l'addition de 1 ou 2 bases dans la séquence exposée dans SEQ ID no : 3, et n'inclut pas de modification en positi
