Chemical structure of W-18
Well, that's changed a bit. At least officially unofficially.
Dr. Brian Roth (@zenbrainest) of Roth Lab in the Department of Pharmacology at the University of North Carolina - Chapel Hill tweeted a few days ago that they had preliminary information on W-18 via the NIMH Psychoactive Drug Screening Program.
Regarding W-18 and possible activity at mu opioid receptors...
And what about activity at kappa and delta opioid receptors?
@andcunningham @rgcjk @forensictoxguy No activity there. Compound seems quite toxic (unknown target) which is problematic for some assays.— BryanRoth (@zenbrainest) May 11, 2016
And toxicity at what cells?
@drugmonkeyblog @andcunningham @rgcjk @forensictoxguy HEK cells though I wouldn't be surprised if others also toxic— BryanRoth(@zenbrainest) May 11, 2016
So, there you have it. Officially unofficially W-18 has no activity at the mu, kappa, or delta opioid receptors.