The Pandemic Response Box─Accelerating Drug Discovery Efforts after Disease Outbreaks.

The current Covid-19 pandemic has underlined the need for a more coordinated and forward-looking investment in the search for new medicines targeting emerging health care threats. Repositioning currently approved drugs is a popular approach to any new emerging disease, but it represents a first wave of response. Behind this would be a second wave of more specifically designed therapies based on activities against specific molecular targets or in phenotypic assays. Following the successful deployment and uptake of previous open access compound collections, we assembled the Pandemic Response Box, a collection of 400 compounds to facilitate drug discovery in emerging infectious disease. These are based on public domain information on chemotypes currently in discovery and early development which have been shown to have useful activities and were prioritized by medicinal chemistry experts. They are freely available to the community as a pharmacological test set with the understanding that data will be shared rapidly in the public domain.

DNDI-6148: A Novel Benzoxaborole Preclinical Candidate for the Treatment of Visceral Leishmaniasis.

Visceral leishmaniasis (VL) is a parasitic disease endemic across multiple regions of the world and is fatal if untreated. Current therapies are unsuitable, and there is an urgent need for safe, short-course, and low-cost oral treatments to combat this neglected disease. The benzoxaborole chemotype has previously delivered clinical candidates for the treatment of other parasitic diseases. Here, we describe the development and optimization of this series, leading to the identification of compounds with potent in vitro and in vivo antileishmanial activity. The lead compound (DNDI-6148) combines impressive in vivo efficacy (>98% reduction in parasite burden) with pharmaceutical properties suitable for onward development and an acceptable safety profile. Detailed mode of action studies confirm that DNDI-6148 acts principally through the inhibition of Leishmania cleavage and polyadenylation specificity factor (CPSF3) endonuclease. As a result of these studies and its promising profile, DNDI-6148 has been declared a preclinical candidate for the treatment of VL.

Preclinical trial of a MAP4K4 inhibitor to reduce infarct size in the pig: does cardioprotection in human stem cell-derived myocytes predict success in large mammals?

Reducing infarct size (IS) by interfering with mechanisms for cardiomyocyte death remains an elusive goal. DMX-5804, a selective inhibitor of the stress-activated kinase MAP4K4, suppresses cell death in mouse myocardial infarction (MI), human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs), and 3D human engineered heart tissue, whose fidelity to human biology is hoped to strengthen the route to clinical success. Here, DMX-10001, a soluble, rapidly cleaved pro-drug of DMX-5804, was developed for i.v. testing in large-mammal MI. Following pharmacodynamic studies, a randomized, blinded efficacy study was performed in swine subjected to LAD balloon occlusion (60 min) and reperfusion (24 h). Thirty-six animals were enrolled; 12 were excluded by pre-defined criteria, death before infusion, or technical issues. DMX-10001 was begun 20 min before reperfusion (30 min, 60 mg/kg/h; 23.5 h, 17 mg/kg/h). At all times tested, beginning 30 min after the start of infusion, DMX-5804 concentrations exceeded > fivefold the levels that rescued hPSC-CMs and reduced IS in mice after oral dosing with DMX-5804 itself. No significant reduction occurred in IS or no-reflow corrected for the area at ischemic risk, even though DMX-10001 reduced IS, expressed in grams or % of LV mass, by 27%. In summary, a rapidly cleaved pro-drug of DMX-5804 failed to reduce IS in large-mammal MI, despite exceeding the concentrations for proven success in both mice and hPSC-CMs.

Design and Synthesis of a Pan-Janus Kinase Inhibitor Clinical Candidate (PF-06263276) Suitable for Inhaled and Topical Delivery for the Treatment of Inflammatory Diseases of the Lungs and Skin.

By use of a structure-based computational method for identification of structurally novel Janus kinase (JAK) inhibitors predicted to bind beyond the ATP binding site, a potent series of indazoles was identified as selective pan-JAK inhibitors with a type 1.5 binding mode. Optimization of the series for potency and increased duration of action commensurate with inhaled or topical delivery resulted in potent pan-JAK inhibitor 2 (PF-06263276), which was advanced into clinical studies.

Quantitative Chemical Proteomic Profiling of Ubiquitin Specific Proteases in Intact Cancer Cells.

Deubiquitinating enzymes play an important role in a plethora of therapeutically relevant processes and are emerging as pioneering drug targets. Herein, we present a novel probe, Ubiquitin Specific Protease (USP) inhibitor, alongside an alkyne-tagged activity-based probe analogue. Activity-based proteome profiling identified 12 USPs, including USP4, USP16, and USP33, as inhibitor targets using submicromolar probe concentrations. This represents the first intact cell activity-based profiling of deubiquitinating enzymes. Further analysis demonstrated functional inhibition of USP33 and identified a synergistic relationship in combination with ATR inhibition, consistent with USP4 inhibition.

Novel Amino-pyrazole Ureas with Potent In Vitro and In Vivo Antileishmanial Activity.

Visceral leishmaniasis is a severe parasitic disease that is one of the most neglected tropical diseases. Treatment options are limited, and there is an urgent need for new therapeutic agents. Following an HTS campaign and hit optimization, a novel series of amino-pyrazole ureas has been identified with potent in vitro antileishmanial activity. Furthermore, compound 26 shows high levels of in vivo efficacy (>90%) against Leishmania infantum, thus demonstrating proof of concept for this series.

Small-molecule anti-inflammatory drug compositions for the treatment of asthma: a patent review (2013 - 2014).

INTRODUCTION: Asthma is a chronic condition affecting 235 million people worldwide, with prevalence continuing to increase. A significant number of patients have poorly controlled asthma but despite this, a new mechanistic class of small-molecule asthma therapy has not emerged over the past 15 years. AREAS COVERED: In this article, the authors review the published patent literature from 2013 to 2014 that describes the discovery of novel small-molecule anti-inflammatory agents for the treatment of asthma. This patent analysis was performed using multiple search engines including SciFinder and Free Patents Online. EXPERT OPINION: This review highlights that significant research is still directed towards the development of novel anti-inflammatory agents for the treatment of asthma. Current standard-of-care therapies are given topically to the lung via an inhaled dose, which the authors believe can offer significant advantages in terms of efficacy and therapeutic index, compared with an oral dose. Several of the patents reviewed disclose preferred compounds and data that suggest an inhaled approach is being specifically pursued. The patents reviewed target a wide range of inflammatory pathways, although none have yet delivered an approved novel medicine for asthma; this gives an indication of both the opportunity and challenge involved in such an endeavor.

Multiparameter optimization in CNS drug discovery: design of pyrimido[4,5-d]azepines as potent 5-hydroxytryptamine 2C (5-HT2C) receptor agonists with exquisite functional selectivity over 5-HT2A and 5-HT2B receptors.

A series of 4-substituted pyrimido[4,5-d]azepines that are potent, selective 5-HT2C receptor partial agonists is described. A rational medicinal chemistry design strategy to deliver CNS penetration coupled with SAR-based optimization of selectivity and agonist potency provided compounds with the desired balance of preclinical properties. Lead compounds 17 (PF-4479745) and 18 (PF-4522654) displayed robust pharmacology in a preclinical canine model of stress urinary incontinence (SUI) and no measurable functional agonism at the key selectivity targets 5-HT2A and 5-HT2B in relevant tissue-based assay systems. Utilizing recent advances in the structural biology of GPCRs, homology modeling has been carried out to rationalize binding and agonist efficacy of these compounds.

Rapid discovery of a novel series of Abl kinase inhibitors by application of an integrated microfluidic synthesis and screening platform.

Drug discovery faces economic and scientific imperatives to deliver lead molecules rapidly and efficiently. Using traditional paradigms the molecular design, synthesis, and screening loops enforce a significant time delay leading to inefficient use of data in the iterative molecular design process. Here, we report the application of a flow technology platform integrating the key elements of structure-activity relationship (SAR) generation to the discovery of novel Abl kinase inhibitors. The platform utilizes flow chemistry for rapid in-line synthesis, automated purification, and analysis coupled with bioassay. The combination of activity prediction using Random-Forest regression with chemical space sampling algorithms allows the construction of an activity model that refines itself after every iteration of synthesis and biological result. Within just 21 compounds, the automated process identified a novel template and hinge binding motif with pIC50 > 8 against Abl kinase--both wild type and clinically relevant mutants. Integrated microfluidic synthesis and screening coupled with machine learning design have the potential to greatly reduce the time and cost of drug discovery within the hit-to-lead and lead optimization phases.

Identification of type-II inhibitors using kinase structures.

Spleen tyrosine kinase is a non-receptor tyrosine kinase, overactivation of which is thought to contribute to autoimmune diseases as well as allergy and asthma. Protein kinases have a highly conserved ATP binding site, thus making challenging the design of selective small molecule inhibitors. It has been well documented that some protein kinases can be stabilized in their inactive conformations (Type-II inhibitors). Herein, we describe a protein structure/ligand-based approach to successfully identify ligands that bind to novel conformations of spleen tyrosine kinase. By utilizing kinase protein crystal structures both in the public domain (RCSB) and within Pfizer's protein crystal database, we report the discovery of the first spleen tyrosine kinase Type-II ligands. Compounds 1 and 3 were found to bind to the DFG-out conformation of spleen tyrosine kinase, while compound 2 binds to a DFG-in, C-Helix-out conformation. In this instance, the C-helix moved significantly to create a large hydrophobic pocket rarely seen in kinase protein crystal structures.

Pyrimido[4,5-d]azepines as potent and selective 5-HT2C receptor agonists: design, synthesis, and evaluation of PF-3246799 as a treatment for urinary incontinence.

New pyrimido[4,5-d]azepines 7 are disclosed as potent 5-HT(2C) receptor agonists. A preferred example, 7b had minimal activation at either the 5-HT(2A) or 5-HT(2B) receptors combined with robust efficacy in a preclinical canine model of stress urinary incontinence (SUI) and attractive pharmacokinetic and safety properties. Based on this profile, 7b (PF-3246799) was identified as a candidate for clinical development for the treatment of SUI. In addition, it proved to be critical to build an understanding of the translation between recombinant cell-based systems, native tissue preparations and in vivo preclinical models. This was a significant undertaking and proved to be crucial in compound selection.

Second generation N-(1,2-diphenylethyl)piperazines as dual serotonin and noradrenaline reuptake inhibitors: improving metabolic stability and reducing ion channel activity.

New N-(1,2-diphenylethyl)piperazines 6 are disclosed as dual serotonin and noradrenaline reuptake inhibitors (SNRI) which may have potential in treating stress urinary incontinence (SUI). In this Letter, we present new data for SNRI PF-526014 (4) including performance in a canine in vivo model of SUI, cardiovascular assessment, pharmacokinetics in dog and determination of the primary routes of metabolism in vitro. Starting from 4, detailed structure activity relationships established that potent dual SNRIs could be achieved by appropriate substitution of the phenyl rings (6: R; R(1)) combined with a preferred stereochemistry. From this set of compounds, piperazine (-)-6a was identified as a potent and selective dual SNRI with improved metabolic stability and reduced ion channel activity when compared to 4. Based on this profile, (-)-6a was selected for further evaluation in a preclinical model of SUI.

Discovery of a novel azepine series of potent and selective 5-HT2C agonists as potential treatments for urinary incontinence.

A range of heterocycle fused azepines were synthesized in order to find a CNS penetrant, selective 5-HT(2C) agonist for the treatment of incontinence. The pyridazo-azepines such as compound 11 were shown to be potent 5-HT(2C) agonists and have potential for CNS penetration and good in vitro ADME properties but lacked selectivity against 5-HT(2B). Fusing a further heterocycle gave the selective triazolopyrimido-azepines. An example of this series, compound 36, was shown to be potent, selective, metabolically stable in vitro and efficacious in an in vivo model of stress urinary incontinence.

N-[(3S)-Pyrrolidin-3-yl]benzamides as novel dual serotonin and noradrenaline reuptake inhibitors: impact of small structural modifications on P-gp recognition and CNS penetration.

The structure-activity relationship and the synthesis of novel N-[(3S)-pyrrolidin-3-yl]benzamides as dual serotonin and noradrenaline monoamine reuptake inhibitors (SNRI) is described. Preferred compound 9 aka PF-184,298 is a potent SNRI with good selectivity over dopamine reuptake inhibition (DRI), good in vitro metabolic stability, weak CYP inhibition and drug-like physicochemical properties consistent with CNS target space. Evaluation in an in vivo preclinical model of stress urinary incontinence showed 9 significantly increased urethral tone at free plasma concentrations consistent with its in vitro primary pharmacology.

Understanding CYP2D6 interactions.

Owing to the polymorphic nature of CYP2D6, clinically significant issues can arise when drugs rely on that enzyme either for clearance, or metabolism to an active metabolite. Available screening methods to determine if the compound is likely to cause drug-drug interactions, or is likely to be a victim of inhibition of CYP2D6 by other compounds will be described. Computational models and examples will be given on strategies to design out the CYP2D6 liabilities for both heme-binding compounds and non-heme-binding compounds.

Pharmacological properties of 2-((R-5-chloro-4-methoxymethylindan-1-yl)-1H-imidazole (PF-3774076), a novel and selective alpha1A-adrenergic partial agonist, in in vitro and in vivo models of urethral function.

2-((R-5-chloro-4-methoxymethyl-indan-1-yl)-1H-imidazole (PF-3774076) is a central nervous system (CNS) penetrant, potent, selective, partial agonist at the human alpha1(A)-adrenoceptor, demonstrating efficacy and selectivity in a range of binding and functional assays. In vivo, PF-3774076 increases peak urethral pressure in anesthetized female dogs in a dose-dependent manner, inducing changes in both the proximal and distal portions of the urethra via a central mechanism of action. The profile of this compound suggests that a CNS penetrant partial agonist at the alpha1(A)-adrenoceptor may offer significant benefit in stress urinary incontinence (SUI). However, despite partial agonism at the alpha1(A)-adrenoceptor and selectivity over alpha1(B)- and alpha1(D)-adrenoceptors, PF-3774076 did not offer the necessary degree of separation over cardiovascular events when assessed in in vivo models of cardiovascular function. This may be due to activation of both peripheral and central alpha1(A)-adrenoceptors. These data indicate that although central, partial alpha1(A)-agonists may offer significant benefit in the treatment of SUI, it may not be possible to achieve the desired level of urethral selectivity over cardiovascular events with this class of agent.

6,7-Dihydro-5H-pyrrolo[1,2-a] imidazoles as potent and selective alpha1A adrenoceptor partial agonists.

Novel pyrroloimidazoles have been identified as potent partial agonists of the alpha(1A) adrenergic receptor, with good selectivity over the alpha(1B), alpha(1D) and alpha(2A) receptor subtypes. Pyrimidine 19 possessed attractive CNS drug-like properties with good membrane permeability and no evidence for P-gp mediated efflux.

Potent and selective alpha1A adrenoceptor partial agonists--novel imidazole frameworks.

Novel imidazole frameworks have been identified as potent partial agonists of the alpha(1A) adrenergic receptor, with good selectivity over the alpha(1B), alpha(1D) and alpha(2A) receptor sub-types. Nitrile 28 possessed attractive CNS drug-like properties with good membrane permeability and no P-pg mediated efflux. 28 also possessed excellent solubility, metabolic stability and wide ligand selectivity.

4-Piperidines and 3-pyrrolidines as dual serotonin and noradrenaline reuptake inhibitors: design, synthesis and structure-activity relationships.

Single enantiomer [(aryloxy)(pyridinyl)methyl]piperidine and pyrrolidine derivatives 5-9 are inhibitors of monoamine reuptake. Structure-activity relationships established that monoamine reuptake inhibition are functions of amine, pyridine isomer, aryloxy ring substitution and stereochemistry. Consequently, selective NRIs, selective SRIs, dual SNRIs and triple SNDRIs were all identified. Dual SNRIs 5l-a and 9c were evaluated in additional pharmacology and pharmacokinetic studies as representative examples from this series.

Chloroquine-astemizole hybrids with potent in vitro and in vivo antiplasmodial activity.

A dual activity, conjugated approach has been taken to form hybrid molecules of two known antimalarial drugs, chloroquine (CQ) and the non-sedating H1 antagonist astemizole. A variety of linkers were investigated to conjugate the two agents into one molecule. Compounds 5-8 possessed improved in vitro activity against a CQ-resistant strain of Plasmodium falciparum, and examples 7 and 8 were active in vivo in mouse models of malaria.