Co-treatment for gene therapy

A method of treating a subject in need of gene therapy for a disease comprising:

• a. administering to said subject an amount of an enzyme effective to degrade or digest and/or inhibit or reduce effector function of serum antibodies in the subject;
• and
• b. administering the gene therapy to said subject;
• wherein the gene therapy is administered at a dose which is lower than the minimum effective dose (MED) that would be administered to a subject in the absence of step a.;
• and
• wherein said subject has no detectable antibodies that specifically bind to the gene therapy, or has either a low titre of neutralising antibodies (NAb) that specifically bind to the gene therapy or a low titre of total antibodies (TAb) that specifically bind to the gene therapy, optionally wherein the presence/titre of antibodies in the subject is measured in a serum sample obtained from the subject prior to step a.