Aspects of the disclosure relate to complexes and other aspects relate to formulations (e.g., aqueous, lyophilized forms) comprising such complexes (e.g., wherein each complex is of the exemplary formula shown below) comprising a phosphorodiamidate morpholino oligomer (e.g., useful for targeting DMD) covalently linked to an antibody (e.g., anti-TfR1 antibody). In some embodiments, the complexes are formulated with histidine (e.g., L-histidine) and sucrose at a specified pH (e.g., about 5.0 to 7.0). Also provided are uses of these formulations for treating a subject having a mutated DMD allele associated with Duchenne Muscular Dystrophy.