Sonada et al. conjugated a novel fusion protein complex to treat MPS II by combining iduronate-2-sulfatase (IDS) with an anti-TfR antibody, and demonstrated the proof-of-concept efficacy of their enzyme-antibody complex in reducing GAG accumulation in the brain parenchyma and peripheral tissue of an MPS II mouse model, though they did not test neurocognitive function of treated mice in the study [64]. This evidence concerns the gene TFRC and mucopolysaccharidosis type 2.