Synthesis and evaluation of aryl-naloxamide opiate analgesics targeting truncated exon 11-associated μ opioid receptor (MOR-1) splice variants

J Med Chem. 2012 Jul 26;55(14):6352-62. doi: 10.1021/jm300305c. Epub 2012 Jul 16.


3-Iodobenzoylnaltrexamide 1 (IBNtxA) is a potent analgesic acting through a novel receptor target that lack many side-effects of traditional opiates composed, in part, of exon 11-associated truncated six transmembrane domain MOR-1 (6TM/E11) splice variants. To better understand the SAR of this drug target, a number of 4,5-epoxymorphinan analogues were synthesized. Results show the importance of a free 3-phenolic group, a phenyl ring at the 6 position, an iodine at the 3'or 4' position of the phenyl ring, and an N-allyl or c-propylmethyl group to maintain high 6TM/E11 affinity and activity. 3-Iodobenzoylnaloxamide 15 (IBNalA) with a N-allyl group displayed lower δ opioid receptor affinity than its naltrexamine analogue, was 10-fold more potent an analgesic than morphine, elicited no respiratory depression or physical dependence, and only limited inhibition of gastrointestinal transit. Thus, the aryl-naloxamide scaffold can generate a potent analgesic acting through the 6TM/E11 sites with advantageous side-effect profile and greater selectivity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amides / chemical synthesis*
  • Amides / chemistry
  • Amides / metabolism
  • Amides / pharmacology*
  • Analgesics / chemical synthesis
  • Analgesics / chemistry
  • Analgesics / metabolism
  • Analgesics / pharmacology
  • Animals
  • Behavior, Animal / drug effects
  • Brain / drug effects
  • Brain / metabolism
  • Cell Line
  • Chemistry Techniques, Synthetic
  • Exons / genetics*
  • Male
  • Mice
  • Opiate Alkaloids / chemical synthesis*
  • Opiate Alkaloids / chemistry
  • Opiate Alkaloids / metabolism
  • Opiate Alkaloids / pharmacology*
  • Protein Isoforms / chemistry
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Structure, Tertiary
  • Receptors, Opioid, mu / chemistry
  • Receptors, Opioid, mu / genetics*
  • Receptors, Opioid, mu / metabolism*
  • Structure-Activity Relationship


  • Amides
  • Analgesics
  • Opiate Alkaloids
  • Protein Isoforms
  • Receptors, Opioid, mu