The present invention discloses anti-idiotypic antibodies and fragments thereof against inhibitory Factor VIII anti-bodies, said inhibitory antibodies having an affinity for the C2 domain of Factor VIII. The anti-idiotypic antibodies of the present invention are able to completely neutralise in vitro and in an in vivo mouse model the inhibitory activity of FVIII inhibitors. The anti idiotypic antibodies of the present invention can be applied for the prevention, treatment or reduction of bleeding disorders of hemophilia patients with inhibitory antibody against the C2 domain of Factor VIII.