Lead discovery

Venoms are highly complex mixtures of biologically active compounds known as toxins. These natural substances, which are produced by a variety of living organisms, tend to be extremely potent and highly selective for physiological targets. They vary in their mode of action and may cause minor, but mostly acute and severe, often lethal effects. However, whether produced by bacteria, fungi, algae, higher plants or animals, toxins are not solely focused on these adverse effects they were designed for by Nature.

These biomolecules have been tailor-made by millions of years of evolution to endow their possessors with the means to carry out the specific offensive, defensive and digestive tasks needed for their survival. They could also cause antibiosis by preventing infection, parasitism and overgrowth by other organisms or have signal functions to deter predators. In marked contrast to the detrimental effects of toxin cocktails at high doses, their appropriate use as individual biomolecules also offers huge benefits, when:

• They are used as molecular tools for scientific research in life sciences.
  
  
• They serve as key reagents for medical diagnosis.
  
  
• They allow designing antidotes to poisoning and envenomations.
  
  
• They inspire novel drugs for human health.
  
  

Despite the large number of venomous animals (more than 100'00 species) and the complexity of their venoms, only a tiny proportion (estimated to represent less than 0.1%) of venom components have been identified and characterized, and less than 1% of genetic information is available. Venoms still have many surprises to reveal and they offer ample room for innovation!

Could It Be Magic ?

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Venomics

What we like to call "venomics" is a pertinent and validated combination of strategies that are:

• Bioactivity-guided through conventional bioactivity follow-up.
  
  
• Structure-driven through simultaneous mass spectrometry investigations.
  
  
• Biocomputing-assisted through homology assessments in parallel.
  
  
• Based on the long term expertise we have at Atheris.
  
  

With our complementary “structure-to-function” discovery strategy, we undertake a backward-looking approach that is complementary to the classical bioactivity-guided approach. This is based on a combination of genomics (through sequencing of cDNA from venom glands), proteomics (through systematic identification and characterization of the venom components) and bio-computing (through the exploitation of unique biochemical and biological databases on venomous animals and their venoms).

These investigations are carried out using state-of-the-art technologies and equipment such as: HPLC and other chromatographic techniques, 2D-SDS-PAGE separation, peptide sequencing via Edman degradation, automated solid phase peptide synthesis, MALDI-TOF-MS, ESI-MS, LC-MS and MS/MS.

This technology platform allows us to complete the discovery process of lead candidates in record time and to transfer valuable supplementary information to the next discovery steps: lead candidate profiling and optimisation.

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Atheris has developed its own “smart” approach of in silico screening, by leveraging its in-depth knowledge of venomous animals. A careful selection of natural sources that have a better chance to contain lead compounds reduces the number of samples that have to be analysed (or increase the number of relative hits) at a later stage by a factor of 100 or more.

Atheris’ unique data- and text-mining strategies for in silico investigations rely on the following proprietary information repositories:

Venomous animals database. Knowledge database of toxins and enzymes. MS maps of crude venoms. References database. Envenomation symptoms and clinical data. Intelectual property files. Technology surveys and market studies.

This unique concentration of know-how allows us to efficiently select the appropriate venom or other natural extract before initiating the “wet-lab” investigations.

We also like to rely on our existing collection of hundreds of venoms, hemolymphs and other natural extracts:

• MELUSINE Collections - Libraries with hundreds of pre-fractionated venoms dispensed in microplates, ready-made for high throughput biological activity screening.
  

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Sample fractionation

The selection of a venomous species marks the beginning of an in-depth investigation that involves:

• Venom extraction and homogenization.
  
  
• Venom fractionation.
  
  
• Peptide & protein isolation.
  
  
• First purification step.
  
  
• Sample preparation & dispensing for bioactivity and structural studies.
  
  

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The bioactivity of the grossly purified fraction is then screened through an iterative process that involves:

• Design and carry out of relevant bioassays experiments on validated targets.
  
  
• Mass spectrometric screening and structural investigations.
  
  
• Matching of the combined results against private & public databases.
  
  

This offers a weath of additional information that allows an optimized early stage pre-selection of hits.

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Deconvolution

Follow-up of active fractions is first performed by mass spectrometry proteomic analyses with database matching. The structural information thus gathered is used for hit selection and subsequent sub-fractionation and bioactivity screening. We also like to couple such investigation to cDNA or EST transcriptomic sequence information. This "Venomics" approach drastically speeds up the process and sometimes allows us to identify leads based on structural infomation prior to any subsequent purification.

Indeed, very often, a biological activity assay is the first step taken in the quest for new compounds, followed by the isolation and characterization of the native bioactive substance from natural libraries. This strategy is time consuming and requires large amounts of material. Nowadays, current mass spectrometry (MS) techniques can generate an abundance of valuable data not only in a very short period of time, but more importantly using much smaller sample amounts.

Through a structure-driven process and thanks to constant evolving biocomputing capacities, MS has become paramount not only for analytical purposes, but also for the rapid discovery and characterization of new components in the field of toxinology. When used in combination with DNA sequencing from cDNA libraries or ESTs, a wealth of information on the venom gland components can be obtained.

This allows us to judiciously select candidate fractions, which we can:

• Sub-fractionate for subsequent follow-up and hit identification.
  
  
• Submit to systematic sequencing of all its components.
  
  

This combined strategy allows us to identify hits very swiftly and from minute amounts of natural substances. Identified hits can thus be synthesized at a very early stage and in depth bioactivity studies can be conduced.

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Characterization & synthesis

Confirmation of the biological activity of a given biochemical entity is obtained by undertaking the following steps:

• Final purification, if necessary at all.
  
  
• Structural characterisation.
  
  
• Small scale synthesis, folding & purification.
  
  
• Structural matching against the natural substance.
  
  
• Additional bioassays.
  
  
• Lead identification.

Once the structure of a hit is determined, we synthesize the molecule in small amount to validate the observed activity and perform a broader set of bioassays. 

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Lead validation

We conduct stringent feasibility studies at a very early stage. This includes selectivity, potency, primary toxicity or stability.

Prior to any further laboratory investigations, a lead candidate undergoes a thorough evaluation of the intellectual property, costs of goods for industrial production and market potential.

Finally, confirmation of biological activity of a lead compound signals the beginning of substantial investigations towards lead optimization and early development.

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