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Fragment screening

The initial incentive behind the creation of IniXium was the firm belief that fragment screening was going to become the ultimate tool for rapid and efficient drug discovery.  History shows that this method has delivered on its promises. IniXium is contributing to increase the success rate of fragment-based screening (FBS) by establishing new paradigms for fragment screening. We designed a fragment library optimized for crystal complex formation. For us, optimized means high solubility and absence of soluble aggregates at the highest possible concentration; two parameters that often hinder complex formation during crystallization. We offer two strategies for FBS. One is affinity-selection mass spectrometry (AS-MS) that is based on the enrichment of binders by ultrafiltration prior to detection by mass spectrometry. This rapid method provides hits that can be moved to crystallography in less than a month with very little protein consumption. In the second strategy, a subset of the most soluble fragments (300) are used directly for crystal soaking. This allows for a faster hit identification, and structures are instantly available to initiate your medicinal chemistry campaign.  Our fragment screening campaigns are followed by a round of “analogue by catalogue”. Virtual screening tools are also used for analogue selection. Structures of these analogues will provide validation of the hits and their binding mode.  We then stay on to provide crystallography support for ligand optimization.

Formatted fragment library

  • DLS measurement of solubility to insure high soaking concentration
  • Library screened for soluble aggregates 
  • Mass spectrometry friendly pooling of fragments

FBS by crystal soaking

  • An optimized library of 300 fragments are screened by crystal soaking
  • Fragments are soaked at high concentration in 2 crystal forms
  • X-ray structures rapidly provide you with a hit list ready for med chem optimization

FBS by affinity-selection mass spectrometry (ASMS)

  • Very low protein consumption
  • Formatted library of 1500 fragments rule of three compliant
  • Screening done with pools of 30 fragments binding to the target protein as the bait
  • Possibility of screening for allosteric sites in the presence of active site blockers
  • Hits are then used for crystal soaking

Fragment hit validation & expansion

  • Based on x-ray hits, analog-by-catalog or virtual screening of analogs for x-ray screening
  • The crystal system established for hit discovery will be ready for your hit expansion and optimization