Retropackaging occurs during AAV production in HEK cells when sequences are inadvertently packed into an AAV particle that are not located between the ITRs, but outside such as bacterial backbone sequences. This is not intentional and bears certain risks, e.g. increased immunogenicity. The risk of retropackaging can be greatly reduced by using minicircles for the production of AAVs. These do not carry any backbone sequences but only the GOI and a short SCAR sequence.