Hyaluronic acid derivative and pharmaceutical composition thereof

A hyaluronic acid derivative containing a hydrophobic group, comprising at least one repeating unit represented by the formula (I):

• wherein
• R1, R2, R3, and R4 are each independently selected from a hydrogen atom, C1-6 alkyl, formyl, and C1-6 alkylcarbonyl;
• Z represents a direct bond, or a peptide linker comprising 2 to 30 arbitrary amino acid residues;
• X1 is a hydrophobic group selected from the groups represented by the following formulas:
• —NRb—R,
• —NRb—COO—R,
• —NRb—CO—R,
• —NRb—CO—NRc—R,
• —COO—R,
• —O—COO—R,
• —S—R,
• —CO—Ya—S—R,
• —O—CO—Yb—S—R,
• —NRb—CO—Yb—S—R, and
• —S—S—R;
• Ra, Rb, and Rc are each independently selected from a hydrogen atom, C1-20 alkyl, amino C2-20 alkyl, and hydroxy C2-20 alkyl, wherein 1 to 3 groups selected from —O— and —NRf— are optionally inserted in an alkyl moiety of these groups;
• Rf is selected from a hydrogen atom, C1-12 alkyl, amino C2-12 alkyl, and hydroxy C2-12 alkyl, wherein 1 or 2 groups selected from —O— and —NH— are optionally inserted in an alkyl moiety of these groups;
• R is a steryl group;
• Y is C2-30 alkylene or —(CH2CH2O)m—CH2CH2—, wherein 1 to 5 groups selected from —O—, —NR9—, and —S—S— are optionally inserted in the alkylene;
• Rg is selected from a hydrogen atom, C1-20 alkyl, amino C2-20 alkyl, and hydroxy C2-20 alkyl, wherein 1 to 3 groups selected from —O— and —NH— are optionally inserted in an alkyl moiety of these groups;
• Ya is C1-5 alkylene;
• Yb is C2-8 alkylene or C2-8 alkenylene;
• and
• m is an integer selected from 1 to 100.