Coated lipid complexes and their use

A lipid composition comprising:

• a nucleic acid is selected from the group consisting of an RNAi, an siRNA, an siNA,
• a cationic lipid component that is a compound according to formula (I),
• wherein R1 and R2 are each independently alkyl;
• n is 1-4;
• R3 is acyl selected from the group consisting of lysyl, ornithyl, 2,4-diaminobutyryl, histidyl and an acyl moiety according to formula (II),
• wherein m is any integer from 1 to 3,
• wherein the NH3+ is optionally absent, and
• Y− is a pharmaceutically acceptable anion,
• a first helper lipid selected from a phospholipid or a steroid, and
• a shielding compound comprising PEG, HEG, polyhydroxyethyl starch (polyHES) and polypropylene,
• wherein said shielding compound provides for a prolonged circulation time in vivo of said lipid composition.