RB-120 (benzyl (2S)-2-{[(2S)-2-({[(2S)-2-amino-4-methylsulfanylbutyl]disulfanyl}methyl)-3-phenylpropanoyl]amino}propanoate) is an orally active analog of the drug RB-101.

[1] It acts as an enkephalinase inhibitor, which is used in scientific research.

administration RB120 is approximately twice as weak as morphine in terms of analgesia; however, it is 16x weaker during i.p.

[1] RB 120 produces a significant dose-dependent antinociceptive response in the rat tail-flick test at 10 and 25 min after i.v.

[1] The analgesic effect occurred with a slower onset compared to typical IV opioids likely because, following enkephalinase inhibition, it may take some time for endogenous enkephalin to accumulate without degradation until sufficient concentration is reached for analgesic effect, whereas for opioids, onset only requires entry into the brain via the blood–brain barrier which occurs rapidly for lipophilic molecules, and binding to the opioid receptor produces a near-instantaneous G-protein mediated response and production of second messenger, without need for de novo synthesis of any neurotransmitters.