This improvement is similar to that reported after treating adult MPS VI mice with either 2 × 1012 genome copies/Kg of the canonical AAV-ARSB vector (which is also a dose used in our NCT03173521 clinical trial) or enzyme replacement therapy30 which is the current standard-of-care for MPS VI. The gene discussed is ARSB; the disease is mucopolysaccharidosis type 6.