A novel delivery system for macromolecules such as proteins and oligonucleotides, and specifically siRNA through biological membranes is provided, comprising conjugation of the macromolecule to a moiety, which enables effective crossing through the membranes. Respectively, novel compounds and pharmaceutical compositions are provided, utilizing said delivery system. In one aspect of the invention, the compounds may be utilized in medical practice, for example, in delivery of siRNA or antisense oligonucleotides across biological membranes for the treatment of medical disorders.
