Use of Intramolecular 1,5-Sulfur-Oxygen and 1,5-Sulfur-Halogen Interactions in the Design of N-Methyl-5-aryl- N-(2,2,6,6-tetramethylpiperidin-4-yl)-1,3,4-thiadiazol-2-amine SMN2 Splicing Modulators

J Med Chem. 2021 Apr 22;64(8):4744-4761. doi: 10.1021/acs.jmedchem.0c02173. Epub 2021 Apr 6.

Abstract

Spinal muscular atrophy (SMA) is a debilitating neuromuscular disease caused by low levels of functional survival motor neuron protein (SMN) resulting from a deletion or loss of function mutation of the survival motor neuron 1 (SMN1) gene. Branaplam (1) elevates levels of full-length SMN protein in vivo by modulating the splicing of the related gene SMN2 to enhance the exon-7 inclusion and increase levels of the SMN. The intramolecular hydrogen bond present in the 2-hydroxyphenyl pyridazine core of 1 enforces a planar conformation of the biaryl system and is critical for the compound activity. Scaffold morphing revealed that the pyridazine could be replaced by a 1,3,4-thiadiazole, which provided additional opportunities for a conformational constraint of the biaryl through intramolecular 1,5-sulfur-oxygen (S···O) or 1,5-sulfur-halogen (S···X) noncovalent interactions. Compound 26, which incorporates a 2-fluorophenyl thiadiazole motif, demonstrated a greater than 50% increase in production of full-length SMN protein in a mouse model of SMA.

MeSH terms

  • Animals
  • Drug Design*
  • Half-Life
  • Halogens / chemistry
  • Humans
  • Male
  • Mice
  • Molecular Conformation
  • Motor Neurons / metabolism
  • Muscular Atrophy, Spinal / genetics
  • Muscular Atrophy, Spinal / pathology
  • Oxygen / chemistry
  • Pyridazines / chemistry
  • RNA Splicing* / drug effects
  • Rats
  • Rats, Sprague-Dawley
  • Structure-Activity Relationship
  • Sulfur / chemistry
  • Survival of Motor Neuron 1 Protein / genetics
  • Survival of Motor Neuron 1 Protein / metabolism
  • Survival of Motor Neuron 2 Protein / genetics
  • Survival of Motor Neuron 2 Protein / metabolism
  • Thiadiazoles / chemistry*
  • Thiadiazoles / metabolism
  • Thiadiazoles / pharmacology

Substances

  • Halogens
  • Pyridazines
  • SMN1 protein, human
  • SMN2 protein, human
  • Survival of Motor Neuron 1 Protein
  • Survival of Motor Neuron 2 Protein
  • Thiadiazoles
  • 1,3,4-thiadiazole
  • pyridazine
  • Sulfur
  • Oxygen