Novel Methodology to Identify TRPV1 Antagonists Independent of Capsaicin Activation

Abstract

TRPV1 was originally characterized as an integrator of various noxious stimuli such as capsaicin, heat, and protons. TRPV1-null mice exhibit a deficiency in sensing noxious heat stimuli, suggesting that TRPV1 is one of the main heat sensors on nociceptive primary afferent neurons and a candidate target for heat hypersensitivity in chronic pain. Several different potent and selective TRPV1 antagonists have been developed by more than 50 companies since the characterization of the receptor in 1997. A consequence of this competitive interest is the crowding of patentable chemical space, because very similar in vitro screening assays are used. To circumvent this issue and to expand our understanding of TRPV1 biology, we sought to take advantage of recent advancements in automated patch-clamp technology to design a novel screening cascade. This SAR-driving assay identified novel modulators that blocked the depolarization-induced activation of outwardly-rectifying TRPV1 currents independent of agonist stimulation, and we correlated the pharmacology to three other innovative assays for higher-throughput screening. Ultimately, we have identified a screening paradigm that would have good predictive value for future TRPV1 drug discovery projects and novel chemical space with a higher probability of gaining intellectual property coverage.

A Thallium-Based Screening Procedure to Identify Molecules That Modulate the Activity of Ca2+-Activated Monovalent Cation-Selective Channels

“…Methods have been developed that probe Ca 2+ or Mn 2+ flux through TRPA1, TRPC4, TRPM7, TRPM8, or TRPV1 with Fluo-4 or FURA2. [23][24][25][26][27] The activity of TRPM4 and TRPM5 cannot be assessed with a Ca 2+ -based screening method since they are monovalent cation-selective channels and impermeable to Ca 2+ . Fluorescent membrane potential dyes and Na + -sensitive dyes could be useful in this regard.…”

Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine

“…For example, the R114E mutant (in the N terminus) shows normal heat responses but is insensitive to both protons and capsaicin (Jung et al, 2002a). Indeed, a new methodology was developed to screen for TRPV1 antagonists that do not inhibit capsaicin activation (Zicha et al, 2013). Added to this complexity are reports of allosteric TRPV1 modulators Lebovitz et al, 2012) and partial agonists/antagonists .…”

Single‐ and multiple dose pharmacokinetics and multiple dose pharmacodynamics of oral ABT‐116 (a TRPV1 antagonist) in dogs

“…Several TRPV1 antagonists have been developed since 1997 (Zicha et al ., ). Approximately, fifteen compounds entered phase 1 clinical trials with about five progressing to phase 2 trials (Trevisani & Gatti, ) some of which have been suspended or terminated because of side effects, such as unmanageable hyperthermia.…”