OPRK1 and myeloid sarcoma: Preclinical research has shown that nalfurafine (5–30 μg/kg) does not cause CPA, anhedonia, sedation, or motor incoordination associated with traditional KOR agonists (Liu et al., 2019) at doses that promote remyelination in MS models (10 μg/kg) (Denny et al., 2021).