Identification of novel ion channel binders: TRPA1 antagonist case study

Ray Boffey¹, Chris Richardson¹, Duncan Hannah¹, Marc Rogers², Robert Kirby², Ian Witton², Trevor Perrior¹

1. Domainex Ltd, Chesterford Research Park, Little Chesterford, Saffron Walden, CB10 1XL
2. Metrion Biosciences Ltd, Riverside 3; Suite 1, Granta Park, Cambridge, CB21 6AD, United Kingdom

Collaborative drug discovery for ion channel screening

Contract Research Organisations (CROs) Domainex and Metrion have formed a collaborative drug discovery partnership to identify novel chemical hits against ion-channel targets. Key to this collaboration are Domainex’s experience in hit identification and Metrion Bioscience’s expertise in ion channel screening and pharmacology. Both partners bring their extensive knowledge of drug target screening.

The transient receptor potential cation channel A1 (TRPA1) is a voltage-dependent, non-selective cation channel that plays a crucial role in sensory processes, particularly in the detection of noxious stimuli such as irritants and chemicals. It is an established therapeutic target, as antagonists of TRPA1 may have significant utility in the treatment of pain, chronic cough, and other inflammatory conditions. Due to its involvement in mediating pain and inflammatory responses, TRPA1 has been a focus of drug development efforts aimed at alleviating various chronic conditions, including neuropathic pain, asthma, and irritable bowel syndrome. Bautista et al.¹ described TRPA1 as a ‘gatekeeper of chronic inflammatory disorders of the skin, airways, and gastrointestinal tract’, highlighting its importance in managing a broad spectrum of inflammatory disorders and making it a key target for therapeutic intervention.

As part of this collaboration, Domainex applied its proprietary LeadBuilder platform to identify commercial compounds for screening based on Metrion’s validated agonist and antagonist profiles of reference compounds. Compounds were then purchased and screened at Metrion through an extensive cascade of assays, to identify true antagonists of the TRPA1 ion channel, with the ultimate goal of advancing the development of novel therapeutic agents targeting this critical ion channel, which plays a pivotal role in various physiological processes, including pain sensation and inflammation.

Results of TRPA1calcium imaging assay: three novel antagonists identified

• 400 compounds were purchased and assayed against human TRPA1 at 10 µM in a validated Ca²⁺ imaging assay on Metrion’s FLIPR platform, which was able to detect both agonists and antagonists of the voltage dependent ion channel.
• 14 hits were progressed to IC₅₀ determination, revealing 3 novel antagonists.
• AMG-0902 derived pharmacophores produced the majority of the hit compounds with the HC-030031 and toxin derived pharmacophores also producing antagonist hits.
• Hits were a balance between compounds closely related to one or more query molecules, such as the match illustrated within the figure below, and more diverse compounds.

Figure 1. Results of the TRPA1 Ca²⁺ imaging assay and B: Plate view of TRPA1 agonists and antagonists.

Future directions for drug discovery and ion channel research

Domainex has applied its LeadBuilder platform to the identification of antagonists for the therapeutically relevant voltage-dependent ion channel TRPA1.

The ligand-based study used Nuclear Magnetic Resonance (NMR) derived structural data and site-directed mutagenesis data as well as small molecule SAR.

Small molecule hits have been obtained from multiple chemotypes with micromolar potency. These include compounds with high similarity to the query molecules and also some more diverse structures. The compound structures are suitable for optimisation as part of a drug discovery project.

Metrion offers expertise in detailed pharmacological evaluation of ligands and this was used to underpin the ligand selection used for the virtual screen.

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2. Paulsen et al, Nature, 520, 511, (2015)
3. Chen and Hackos, Naunyn Schmiedebergs Arch Pharmacol, 388(4), 451, 2015)
4. Lehto et al, Mol Pain, 12, (2016),PMID:27899696
5. Rooney et al, J Med Chem, 57(12), 5129, (2014)
6. Gui et al, Curr Biol, 24, 473, (2014)
7. ChEMBL24: www.ebi.ac.uk/chembl
8. Schenkel et al, J Med Chem, 59(6), 2794, (2016)