Fragment-based lead discovery (FBLD) has been demonstrated over the last two decades to be an efficient alternative to traditional HTS and is continuously growing in popularity as it also provides information on binding mode, mechanism of action and target engagement.


Red Glead Discovery in partnership with SARomics Biostructures offers versatile and integrated lead discovery services based on a common fragment screening platform. Our key technologies are:

  • Weak Affinity Chromatography (WAC™)
  • Nuclear Magnetic Resonance spectroscopy (NMR)
  • Thermal Shift Assay (DSF)
  • X-ray Crystallography
  • Microscale Thermophoresis (MST)
  • Biochemical & cell-based screening

”Sample the largest amount of chemical space economically”

There are many advantages in using libraries of a few hundred up to thousands of fragments (small molecules of a molecular weight of 120 – 300 g/mol) instead of vast libraries of larger substances. Besides significant savings in cost and time, the FBLD approach has repeatedly demonstrated its high potential of generating innovative and novel chemical entities for fast progression into clinical trials.

Screening strategies

Fragment-based approaches allow strategical, rational drug discovery due to the ability to combine several biophysical methods to strengthen the confidence in data. Besides the identification of novel binders, this approach frequently also provides a wealth of other target-specific information such as binding mode, binding energies and other type of structural and thermodynamic data that can accelerate downstream drug discovery activities.

With a range of versatile and diverse fragment screening technologies, we can customise a fragment screen campaign according to various drug targets and needs of clients and partners. If the drug target is feasible for immobilization on a LC column, we exclusively offer weak affinity chromatography (WAC™) as a cost-efficient, high-throughput method for the initial step in the fragment screening process. WAC™ can be used as stand-alone technique as well as in combination with other complementary techniques. The exact strategy is always carefully tailored to the needs and budget of each client project. An example is outlined below:



  • WAC™ – weak affinity chromatography (proprietary technology)
  • NMR – primarily ligand-detected 1D 1H/19F NMR techniques
  • DSF – differential scanning fluorimetry (i.e. thermal shift assay)
  • HCS – high concentration screening using functional readout, e.g. biochemical assay
  • CFS – crystallographic fragment screening

As a follow-up activity to confirm found actives in the primary screening and remove false positives, we apply a secondary method with orthogonal output, normally NMR, DSF and/or X-ray crystallography. LC-MS and NMR are also used to confirm purity and identity of the obtained active fragments.

Evaluation and prioritisation of active fragments can be performed by the Client or by our team of medicinal and computational chemists with supporting data obtained from our in vitro biology and ADME capabilities.



WAC™ – weak affinity chromatography (proprietary technology) is a powerful technique for primary screening of fragment libraries and is an integral part of our FBLD platform. This unique technology originates from the academic research of Professor Sten Ohlson and his co-workers. The commercial rights of WAC are fully owned by Red Glead Discovery and SARomics Biostructures AB. Download a flyer here.

Principles and advantages of WAC™

  • Physiological buffer as mobile phase
  • Target protein immobilized on HPLC column
  • Detection by LC-MS
  • Simple detection of retention times
  • Kd calculated from retention time
  • Allows simultaneous identification of weak binders (mM) in complex mixtures
  • High throughput potential (up to 3000-4000 fragments per week)
  • Finding mM hits by screening at 1-5 µM
  • Hit ranking / Quality control

Literature and applications of WAC™

WAC™ has been applied to a wide range of targets, e.g. kinases, proteases, nuclear hormone receptors, epigenetic targets, PPIs, chaperones and channels. Here is a reference list as of September 5, 2017. For an example of how WAC™ was applied to thrombin, look at the J Biomolecular Screening 2013;18:160-71. If you are interested in information how WAC™ can be applied to your specific target or target class, please contact us.



The quality and design of the screening library is paramount for the success of finding hits. We can screen libraries provided by our clients and partners in a cost-effective fashion and/or use our own growing fragment collection. In addition, specific fragment collections can be specifically ordered from external suppliers for each campaign depending on the need of the client. Our fragment collection consists of selected commercial fragments and own exclusive fragments made by our medicinal chemistry group.

It is critical to ensure that the fragments screed are pure and of the correct identity, i.e. quality control (QC) must be included. If WAC and NMR are used as screening techniques, there will be a high degree of fragment quality control (QC) already within the screening but additional QC by a standard analytical methods should always be added as appropriate.



If you would like to know more about how to exploit our in vitro biology and assay capabilities, please contact us at:

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+46 46 460 12 90
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