Optimized in vivo delivery system with endosomolytic agents for nucleic acid conjugates

A conjugated nucleic acid molecule which has the following formula:

• wherein N is a nucleotide, n is an integer from 15 to 195, the underlined N refers to a nucleotide having or not a modified phosphodiester backbone, L′ is a linker;
• m is 1 and L is a linker, C is a molecule facilitating endocytosis selected from the group consisting of single or double chain fatty acids, tocopherol, folates or folic acid, cholesterol, sugar, peptide and protein, and wherein C is conjugated via L to the 5′ end of the nucleic acid molecule.