Arformoterol ((R,R)-Formoterol) maleate, the (R,R)-enantiomer of Formoterol, is a long-acting β2-adrenergic receptor (β2-AR) agonist, with a K d of 2.9 nM. Arformoterol maleate can be used for the research of chronic obstructive pulmonary disease (COPD).