Danger signals are a hallmark of many common inflammatory diseases, and these stimuli can function to activate the cytosolic innate immune signalling receptor NLRP3 (NOD-, LRR- and pyrin domain-containing 3). Once activated, NLRP3 nucleates the assembly of an inflammasome, leading to caspase 1-mediated proteolytic activation of the interleukin-1β (IL-1β) family of cytokines, and induces an inflammatory, pyroptotic cell death. Pharmacological inhibition of NLRP3 activation results in potent therapeutic effects in a wide variety of rodent models of inflammatory diseases, effects that are mirrored by genetic ablation of NLRP3. Although these findings highlight the potential of NLRP3 as a drug target, an understanding of NLRP3 structure and activation mechanisms is incomplete, which has hampered the discovery and development of novel therapeutics against this target. Here, we review recent advances in our understanding of NLRP3 activation and regulation, highlight the evolving landscape of NLRP3 modulators and discuss opportunities for pharmacologically targeting NLRP3 with novel small molecules.

Targeting the NLRP3 inflammasome in inflammatory diseases

Attempts to reduce the number of efficacy- and safety-related failures that may be linked to the physicochemical properties of small-molecule drug candidates have been inconclusive owing to the limited size of data sets from individual companies. Waring and colleagues analyse the largest data set compiled so far on the causes of attrition for oral, small-molecule drug candidates, derived from a pioneering data-sharing effort by AstraZeneca, Eli Lilly and Company, GlaxoSmithKline and Pfizer.

An analysis of the attrition of drug candidates from four major pharmaceutical companies

Microengineered cell culture systems are becoming sufficiently sophisticated that they can recapitulate many of the phenomena observed in tissues and organisms. Here, Huh and colleagues discuss the advances made in these 'organs-on-chips' and how they could be used in drug development, including target identification and validation, toxicity screening and stratified medicine.

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Organs-on-chips at the frontiers of drug discovery

Polypharmacology describes the activity of compounds at multiple targets. Current research focuses on two aspects of polypharmacology: (1) unintended polypharmacology can lead to adverse effects; (2) polypharmacology across several disease-relevant targets can improve therapeutic efficacy, prevent drug resistance, or reduce therapeutic-target-related adverse effects. This perspective reviews these interconnected aspects of polypharmacology. The first part discusses the relevance of polypharmacology for the safety of drugs, the mitigation of safety risks, and methods to identify polypharmacological compounds early in the drug discovery process. The second part discusses the advantages of polypharmacology in the treatment of multigenic diseases and infections, and opportunities for drug discovery and drug repurposing. This perspective aims to provide a balanced view on polypharmacology, which can compromise the safety of drugs, but can also confer superior efficacy.

Polypharmacology - foe or friend?

The early and efficient assessment of cardiac safety liabilities is essential to confidently advance novel drug candidates. This article discusses evolving mechanistically based preclinical strategies for detecting drug-induced electrophysiological and structural cardiotoxicity using in vitro human ion channel assays, human-based in silico reconstructions and human stem cell-derived cardiomyocytes. These strategies represent a paradigm shift from current approaches, which rely on simplistic in vitro assays that measure blockade of the Kv11.1 current (also known as the hERG current or IKr) and on the use of non-human cells or tissues. These new strategies have the potential to improve sensitivity and specificity in the early detection of genuine cardiotoxicity risks, thereby reducing the likelihood of mistakenly discarding viable drug candidates and speeding the progression of worthy drugs into clinical trials.

Evolution of strategies to improve preclinical cardiac safety testing

In vitro pharmacological profiling is increasingly being used earlier in the drug discovery process to identify undesirable off-target activity profiles that could hinder or halt the development of candidate drugs or even lead to market withdrawal if discovered after a drug is approved Here, for the first time, the rationale, strategies and methodologies for in vitro pharmacological profiling at four major pharmaceutical companies (AstraZeneca, GlaxoSmithKline, Novartis and Pfizer) are presented and illustrated with examples of their impact on the drug discovery process We hope that this will enable other companies and academic institutions to benefit from this knowledge and consider joining us in our collaborative knowledge sharing

Reducing safety-related drug attrition: the use of in vitro pharmacological profiling

BACKGROUND AND PURPOSE P2X3 and P2X2/3 receptors are highly localized on the peripheral and central pathways of nociceptive signal transmission. The discovery of A-317491 allowed their validation as chronic inflammatory and neuropathic pain targets, but this molecule has a very limited oral bioavailability and CNS penetration. Recently, potent P2X3 and P2X2/3 blockers with a diaminopyrimidine core group and better bioavailability were synthesized and represent a new opportunity for the validation of P2X3-containing receptors as targets for pain. Here we present a characterization of three representative diaminopyrimidines.



EXPERIMENTAL APPROACH The activity of compounds was evaluated in intracellular calcium flux and electrophysiological recordings from P2X receptors expressed in mammalian cells and in a in vivo model of inflammatory pain (complete Freund's adjuvant (CFA) in rat paws).



KEY RESULTS Compound A potently blocked P2X3 (pIC50 = 7.39) and P2X2/3 (pIC50 = 6.68) and showed no detectable activity at P2X1, P2X2, P2X4 and P2X7 receptors (pIC50 < 4.7). Whole-cell voltage clamp electrophysiology confirmed these results. Compounds showed good selectivities when tested against a panel of different classes of target. In the CFA model, compound B showed significant anti-nociceptive effects (57% reversal at 3 mg·kg−1).



CONCLUSIONS AND IMPLICATIONS The diaminopyrimidines were potent and selective P2X3 and P2X2/3 receptor antagonists, showing efficacy in vivo and represent useful tools to validate these receptors as targets for inflammatory and neuropathic pain and provide promising progress in the identification of therapeutic tools for the treatment of pain-related disorders.

https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1476-5381.2011.01322.x

Wolfgang Jarolimek

Papers

Reducing safety-related drug attrition: the use of in vitro pharmacological profiling

Characterization of three diaminopyrimidines as potent and selective antagonists of P2X3 and P2X2/3 receptors with in vivo efficacy in a pain model

Rational design of an in vitro safety profiling panel to reduce undesired secondary pharmacology of drug candidates