(-)-U-50488 hydrochloride ((-)-Trans-(1S,2S)-U-50488 hydrochloride) is a selective kappa-opioid receptor (KOR) agonist (b>K d =2.2 nM) which is a more selective than μ-opioid receptor (MOR) (b>K d =430 nM). (-)-U-50488 hydrochloride is a more active enantiomer than (+) trans-(1R,2R) U-50488 or the (±) trans-racemic mixture U-50488. (-)-U-50488 hydrochloride has a potent and sustained anti- HIV effect in fected blood monocyte-derived macrophages (MDM) [1].