The maturation of the RNA cap involving guanosine N-7 methylation, catalyzsed by the HsRNMT (RNA guanine-7 methyltransferase (HsRNMT)-RAM (RNA guanine-N7 methyltransferase activating subunit (RAM) complex, is currently under investigation as a novel strategy to combat PIK3CA -mutant breast cancer. However, the development of effective drugs is hindered by a limited understanding of the enzyme's mechanism and a lack of small molecule inhibitors. Following the elucidation of the HsRNMT-RAM molecular mechanism, we report the biophysical characterizsation of two small molecule hits. Biophysics, biochemistry and structural biology confirm that both compounds bind competitively with cap and bind effectively to HsRNMT-RAM in the presence of the co-product SAH, with a binding affinity (KD) of approximately 1 μM. This stabilisation of the enzyme--product complex results in uncompetitive inhibition. Finally, we describe the properties of the cap pocket and provided suggestions for further development of the tool compounds.

The proteasome is considered an excellent drug target for many infectious diseases as well as cancer. Challenges with robust and safe supply of proteasomes from infectious agents, lack of structural information, and complex pharmacology due to multiple active sites have hampered progress in the infectious disease space. We recombinantly expressed the proteasome of the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease, and demonstrate pharmacological equivalence to the native T. cruzi proteasome. Active-site mutant recombinant proteasomes reveal substrate promiscuity for WT proteasomes, with important implications for assessing pharmacological responses of active-site selective inhibitors. Using these mutant proteasomes, we show that some selective parasite proteasome inhibitors only partially inhibit the chymotrypsinlike activity, including a newly developed 5-(phenoxymethyl) furan-2-carboxamide-based proteasome inhibitor. In spite of partial inhibition, these compounds remain potent inhibitors of intracellular T. cruzi growth. Drug-resistant mutants provide further insights in drug mode-of-inhibition. We also present the high-resolution CryoEM structures of both native and recombinantly-expressed T. cruzi proteasomes which reveal pharmacologically relevant differences in the ligand-binding site compared to the related Leishmania proteasome. Furthermore, we show that the trypanosomatid (34/(35 selectivity pocket is not present in the proteasome structures of other protozoan parasites. This work highlights the need, and provides approaches, to precisely assess proteasome substrate selectivity and pharmacology. It enables structure-guided drug discovery for this promising Chagas disease drug target, provides a new chemical starting point for drug discovery, and paves the road for development of robust proteasome drug discovery programmes for other eukaryotic infectious diseases.

Leishmaniasis is a neglected tropical disease; there is currently no vaccine and treatment is reliant upon a handful of drugs suffering from multiple issues including toxicity and resistance. There is a critical need for development of new fit-for-purpose therapeutics, with reduced toxicity and targeting new mechanisms to overcome resistance. One enzyme meriting investigation as a potential drug target in Leishmania is M17 leucyl-aminopeptidase (LAP). Here, we aimed to chemically validate LAP as a drug target in L. major through identification of potent and selective inhibitors. Using RapidFire mass spectrometry, the compounds DDD00057570 and DDD00097924 were identified as selective inhibitors of recombinant Leishmania major LAP activity. Both compounds inhibited in vitro growth of L. major and L. donovani intracellular amastigotes, and overexpression of LmLAP in L. major led to reduced susceptibility to DDD00057570 and DDD00097924, suggesting that these compounds specifically target LmLAP. Thermal proteome profiling revealed that these inhibitors thermally stabilized two M17 LAPs, indicating that these compounds selectively bind to enzymes of this class. Additionally, the selectivity of the inhibitors to act on LmLAP and not against the human ortholog was demonstrated, despite the high sequence similarities LAPs of this family share. Collectively, these data confirm LmLAP as a promising therapeutic target for Leishmania spp. that can be selectively inhibited by drug-like small molecules.

Identification and assessment of novel targets is essential to combat drug resistance in the treatment of HIV/AIDS. HIV Capsid (HIV-CA), the protein playing a major role in both the early and late stages of the viral life cycle, has emerged as an important target. We have applied an NMR fragment screening platform and identified molecules that bind to the N-terminal domain (NTD) of HIV-CA at a site close to the interface with the C-terminal domain (CTD). Using X-ray crystallography, we have been able to obtain crystal structures to identify the binding mode of these compounds. This allowed for rapid progression of the initial, weak binding, fragment starting points to compounds 37 and 38, which have 19F-pKi values of 5.3 and 5.4 respectively.

Dry DMSO can rapidly pull water vapor out of the air due to its hygroscopic nature. This is a well-documented problem within drug discovery, particularly within high-throughput screening (HTS). This hydration is caused by atmospheric moisture being absorbed each time a compound library is used. This effect becomes increasingly pronounced when a compound library is used routinely. The result of this hydration is a change to both the total volume of solution and the concentration of sample still in solution. This can result in a large amount of variability in the measured biological activity of a sample depending on the library usage. In this paper, we show the detrimental effects the hydration of sample libraries has on the reproducibility of biological data and present a novel way to remove it from HTS library plates. Our approach involves creating a DMSO-rich environment, created by placing anhydrous DMSO in compound storage pods purged with nitrogen, and incubating library plates in this environment for up to 3 days. Quantification via evaporative light scattering detection (ELSD) showed that removing water greatly increased the molarity of solutions, with a greater effect being seen for compounds with poor solubility. We also demonstrated how this approach can restore the inhibitory activity of stock solutions of compounds (pIC50) of samples containing ∼30 % water from >30 µM to sub-micromolar after moisture removal. This method improves the reliability of tested compounds in HTS by potentially saving pharmaceutical companies hundreds of thousands of dollars in screening campaigns and increasing the quality of data.

Currently, available therapeutics for the treatment of Parkinson’s disease (PD) fail to provide sustained and predictable relief from motor symptoms without significant risk of adverse events (AEs). While dopaminergic agents, particularly levodopa, may initially provide strong motor control, this efficacy can vary with disease progression. Patients may suffer from motor fluctuations, including sudden and unpredictable drop-offs in efficacy. Dopamine agonists (DAs) are often prescribed during early-stage PD with the expectation they will delay the development of levodopa-associated complications, but currently available DAs are less effective than levodopa for the treatment of motor symptoms. Furthermore, both levodopa and DAs are associated with a significant risk of AEs, many of which can be linked to strong, repeated stimulation of D2/D3 dopamine receptors. Targeting D1/D5 dopamine receptors has been hypothesized to produce strong motor benefits with a reduced risk of D2/D3-related AEs, but the development of D1-selective agonists has been previously hindered by intolerable cardiovascular AEs and poor pharmacokinetic properties. There is therefore an unmet need in PD treatment for therapeutics that provide sustained and predictable efficacy, with strong relief from motor symptoms and reduced risk of AEs. Partial agonism at D1/D5 has shown promise for providing relief from motor symptoms, potentially without the AEs associated with D2/D3-selective DAs and full D1/D5-selective DAs. Tavapadon is a novel oral partial agonist that is highly selective at D1/D5 receptors and could meet these criteria. This review summarizes currently available evidence of tavapadon’s therapeutic potential for the treatment of early through advanced PD.

BackgroundChagas disease is caused by the protozoan parasite Trypanosoma cruzi and leads to ~10,000 deaths each year. Nifurtimox and benznidazole are the only two drugs available but have significant adverse effects and limited efficacy. New chemotherapeutic agents are urgently required. Here we identified inhibitors of the acidic M17 leucyl-aminopeptidase from T. cruzi (LAPTc) that show promise as novel starting points for Chagas disease drug discovery.Methodology/principal findingsA RapidFire-MS screen with a protease-focused compound library identified novel LAPTc inhibitors. Twenty-eight hits were progressed to the dose-response studies, from which 12 molecules inhibited LAPTc with IC50 < 34 μM. Of these, compound 4 was the most potent hit and mode of inhibition studies indicate that compound 4 is a competitive LAPTc inhibitor, with Ki 0.27 μM. Compound 4 is selective with respect to human LAP3, showing a selectivity index of >500. Compound 4 exhibited sub-micromolar activity against intracellular T. cruzi amastigotes, and while the selectivity-window against the host cells was narrow, no toxicity was observed for un-infected HepG2 cells. In silico modelling of the LAPTc-compound 4 interaction is consistent with the competitive mode of inhibition. Molecular dynamics simulations reproduce the experimental binding strength (-8.95 kcal/mol), and indicate a binding mode based mainly on hydrophobic interactions with active site residues without metal cation coordination.Conclusions/significanceOur data indicates that these new LAPTc inhibitors should be considered for further development as antiparasitic agents for the treatment of Chagas disease.

Studies have shown that disrupting the formation of the ligand-RET-GFRα complex could be an effective way of treating pain and itch. Compared to traditional high-throughput screens, DNA encoded libraries (DELs) have distinguished themselves as a powerful technology for hit identification in recent years. The present work demonstrates the use of DEL technology identifying compound 16 as the first GFRa2/GFRa3 small molecule inhibitor (0.1/0.2 μM respectively) selective over RET. This molecule represents an opportunity to advance the development of small-molecule inhibitors targeting the GFRα-RET interface for the treatment of pain and itch.

There is an urgent need for the development of new therapeutics with novel modes of action to target Gram-negative bacterial infections, due to resistance to current drugs. Previously, FabA, an enzyme in the bacterial type II fatty acid biosynthesis pathway, was identified as a potential drug target in Pseudomonas aeruginosa, a Gram-negative bacteria of significant clinical concern. A chemical starting point was also identified. There is a cysteine, Cys15, in the active site of FabA, adjacent to where this compound binds. This paper describes the preparation of analogues containing an electrophilic warhead with the aim of covalent inhibition of the target. A wide variety of analogues were successfully prepared. Unfortunately, these analogues did not increase inhibition, which may be due to a loop within the enzyme partially occluding access to the cysteine.

There is a need for novel chemical matter for phenotypic and target-based screens to find starting points for drug discovery programmes in neglected infectious diseases and non-hormonal contraceptives that disproportionately affect Low- and Middle-Income Countries (LMICs). In some disease areas multiple screens of corporate and other libraries have been carried out, giving rise to some valuable starting points and leading to preclinical candidates. Whilst in other disease areas, little screening has been carried out. Much screening against pathogens has been conducted phenotypically as there are few robustly validated protein targets. However, many of the active compound series identified share the same molecular targets. To address the need for new chemical material, in this article we describe the design of a new library, designed for screening in drug discovery programmes for neglected infectious diseases. The compounds have been selected from the Enamine REAL (REadily AccessibLe) library, a virtual library which contains approximately 4.5 billion molecules. The molecules theoretically can be synthesized quickly using commercially available intermediates and building blocks. The vast majority of these have not been prepared before, so this is a source of novel compounds. In this paper we describe the design of a diverse library of 30,000 compounds from this collection (graphical abstract). The new library will be made available to laboratories working in neglected infectious diseases, subject to a review process. The project has been supported by the Bill & Melinda Gates Foundation and the Wellcome Trust (Wellcome).

Dopamine agonists (DAs) have demonstrated efficacy for the treatment of Parkinson's disease (PD) but are limited by adverse effects (AEs). DAs can vary considerably in their receptor subtype selectivity and affinity, chemical composition, receptor occupancy, and intrinsic activity on the receptor. Most currently approved DAs for PD treatment primarily target D2/D3 (D2-like) dopamine receptors. However, selective activation of D1/D5 (D1-like) dopamine receptors may enable robust activation of motor function while avoiding AEs related to D2/D3 receptor agonism. Full D1/D5 receptor-selective agonists have been explored in small, early-phase clinical studies, and although their efficacy for motor symptoms was robust, challenges with pharmacokinetics, bioavailability, cardiovascular AEs, and dyskinesia rates similar to levodopa prevented clinical advancement. Generally, repeated dopaminergic stimulation with full DAs is associated with frontostriatal dysfunction and sensitization that may induce plastic changes in the motor system, and neuroadaptations that produce long-term motor and nonmotor complications, respectively. Recent preclinical and clinical studies suggest that a D1/D5 receptor-selective partial agonist may hold promise for providing sustained, predictable, and robust motor control, while reducing risk for motor complications (e.g., levodopa-induced dyskinesia) and nonmotor AEs (e.g., impulse control disorders and excessive daytime sleepiness). Clinical trials are ongoing to evaluate this hypothesis. The potential emerging availability of novel dopamine receptor agonists with selective dopamine receptor pharmacology suggests that the older terminology "dopamine agonist" may need revision to distinguish older-generation D2/D3-selective agonists from D1/D5-selective agonists with distinct efficacy and tolerability characteristics.

The sporozoite stages of malaria parasites are the primary cause of infection of the vertebrate host and are targeted by (experimental) vaccines. Yet, little is known about their susceptibility to chemical intervention. Phenotypic high-throughput screens have not been feasible due to a lack of in vitro systems. Here we tested 78 marketed and experimental antimalarial compounds in miniaturized assays addressing sporozoite viability, gliding motility, hepatocyte traversal, and intrahepatocytic schizogony. None potently interfered with sporozoite viability or motility but ten compounds acted at the level of schizogony with IC50s < 100 nM. To identify compounds directly targeting sporozoites, we screened 81,000 compounds from the Global Health Diversity and reFRAME libraries in a sporozoite viability assay using a parasite expressing a luciferase reporter driven by the circumsporozoite promoter. The ionophore gramicidin emerged as the single hit from this screening campaign. Its effect on sporozoite viability translated into reduced gliding motility and an inability of sporozoites to invade human primary hepatocytes and develop into hepatic schizonts. While providing proof of concept for a small molecule sporontocidal mode of action, our combined data indicate that liver schizogony is more accessible to chemical intervention by (candidate) antimalarials.

Pan Assay INterference compoundS (PAINS) are known to be a source of false positives in High Throughput Screening (HTS) campaigns. This has become a major problem in medicinal chemistry, often resulting in undesirable project outcomes and increased overall cost. Our recent campaign to identify inhibitors of USP8 that could be used in the treatment of Parkinson’s disease identified several PAINS that worked via a variety of mechanisms. Herein, we discuss the process developed to identify not only the PAINS but also confirming the interference mechanism causing their activity. We found in this project that our USP8 assay was susceptible to multiple modes of interference, making it difficult to identify genuine hit molecules. ![Figure][1] ### Competing Interest Statement The authors have declared no competing interest. [1]: pending:yes

Decades of research have highlighted the importance of optimal stimulation of cortical dopaminergic receptors, particularly the D1R receptor (D1R), for prefrontal-mediated cognition. This mechanism is particularly relevant to the cognitive deficits in schizophrenia, given the abnormalities in cortical dopamine (DA) neurotransmission and in the expression of D1R. Despite the critical need for D1R-based therapeutics, many factors have complicated their development and prevented this important therapeutic target from being adequately interrogated. Challenges include determination of the optimal level of D1R stimulation needed to improve cognitive performance, especially when D1R expression levels, affinity states, DA levels, and the resulting D1R occupancy by DA, are not clearly known in schizophrenia, and may display great interindividual and intraindividual variability related to cognitive states and other physiological variables. These directly affect the selection of the level of stimulation necessary to correct the underlying neurobiology. The optimal mechanism for stimulation is also unknown and could include partial or full agonism, biased agonism, or positive allosteric modulation. Furthermore, the development of D1R targeting drugs has been complicated by complexities in extrapolating from in vitro affinity determinations to in vivo use. Prior D1R-targeted drugs have been unsuccessful due to poor bioavailability, pharmacokinetics, and insufficient target engagement at tolerable doses. Newer drugs have recently become available, and these must be tested in the context of carefully designed paradigms that address methodological challenges. In this paper, we discuss how a better understanding of these challenges has shaped our proposed experimental design for testing a new D1R/D5R partial agonist, PF-06412562, renamed CVL-562.

BACKGROUND: The progressive nature of Parkinson disease (PD), together with a lack of curative treatments, contributes to its economic burden. OBJECTIVE: To estimate the longitudinal incremental costs attributable to PD among Medicare beneficiaries. METHODS: In this retrospective cohort study, we used data from the Chronic Conditions Data Warehouse to identify Medicare beneficiaries with and without PD-related claims identified from 2006 to 2014 with follow-up until 2015. We grouped PD cases and controls based on their survival profiles using a grouping algorithm that used the following baseline measures: age, race, sex, and comorbidity. We identified 3 survival groups and used them to stratify the descriptive annual cost estimates in the 9 years after the index date. We estimated the incremental 1-, 3-, and 5-year costs of PD using generalized linear models (GLM) that controlled for baseline factors. RESULTS: We identified 27,394 cases and controls who were grouped into 3 survival groups. The mean age of the full study sample was 73 years. No material differences were found in the incremental cost of PD across the survival groups. Based on the multivariable GLM, the 1-year incremental cost of PD was $9,625 (95% CI, $9,054-$10,197). The 3-year incremental cost of PD was $20,832 (95% CI, $19,390-$22,274). The 5-year incremental cost of PD was $27,466 (95% CI, 25,088-$29,844). CONCLUSIONS: Among Medicare beneficiaries, PD is associated with excess costs compared with controls. We did not identify substantial differences in the incremental cost of PD across the survival groups. DISCLOSURES:This study was funded by Pfizer Inc. The funding agreement did not impact the authors' independence in designing the study, collecting the data, interpreting the data, writing the manuscript, and submitting the manuscript for publication. Dr Onukwugha reports grants from Pfizer Inc for the conduct of this study and is an employee of University of Maryland, Baltimore, which received financial support from Pfizer Inc in connection with the development of this manuscript; Dr Shulman reports research funding from Pfizer Inc related to the current work, is an employee of University of Maryland, Baltimore, which received financial support from Pfizer Inc in connection with the development of this manuscript, and reports research funding from the NIH, The Rosalyn Newman Foundation, and the Eugenia and Michael Brin family unrelated to the current work and royalties from Oxford University Press and Johns Hopkins University Press; Ms Myers and Dr Alvir are employees and stockholders of Pfizer Inc; Dr Gray was an employee and stockholder of Pfizer Inc at the time of analysis.

Tuesday, April 5May 3, 2022Free AccessPharmacokinetics, Pharmacodynamics, and Safety of the Highly Selective Dopamine D1/D5 Agonist Tavapadon: Summary of Phase 1 Clinical Studies (P10-11.001)Gina Pastino, Josh Yuan, Sridhar Duvvuri, Matthew Leoni, Kimberly Largay, Ih Chang, Amy Giugliano, Stacey Versavel, David Gray, Raymond Sanchez, and John RengerAuthors Info & AffiliationsMay 3, 2022 issue98 (18_supplement)https://doi.org/10.1212/WNL.98.18_supplement.2728 Letters to the Editor

Pyrazolo[1,5-a]pyrimidin-7(4H)-one was identified through high-throughput whole-cell screening as a potential antituberculosis lead. The core of this scaffold has been identified several times previously and has been associated with various modes of action against Mycobacterium tuberculosis (Mtb). We explored this scaffold through the synthesis of a focused library of analogues and identified key features of the pharmacophore while achieving substantial improvements in antitubercular activity. Our best hits had low cytotoxicity and showed promising activity against Mtb within macrophages. The mechanism of action of these compounds was not related to cell-wall biosynthesis, isoprene biosynthesis, or iron uptake as has been found for other compounds sharing this core structure. Resistance to these compounds was conferred by mutation of a flavin adenine dinucleotide (FAD)-dependent hydroxylase (Rv1751) that promoted compound catabolism by hydroxylation from molecular oxygen. Our results highlight the risks of chemical clustering without establishing mechanistic similarity of chemically related growth inhibitors.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) represents a significant threat to human health. Despite its similarity to related coronaviruses, there are currently no specific treatments for COVID-19 infection, and therefore there is an urgent need to develop therapies for this and future coronavirus outbreaks. Formation of the cap at the 5′ end of viral RNA has been shown to help coronaviruses evade host defenses. Nonstructural protein 14 (nsp14) is responsible for N7-methylation of the cap guanosine in coronaviruses. This enzyme is highly conserved among coronaviruses and is a bifunctional protein with both N7-methyltransferase and 3′-5′ exonuclease activities that distinguish nsp14 from its human equivalent. Mutational analysis of SARS-CoV nsp14 highlighted its role in viral replication and translation efficiency of the viral genome. In this paper, we describe the characterization and development of a high-throughput assay for nsp14 utilizing RapidFire technology. The assay has been used to screen a library of 1771 Food and Drug Administration (FDA)-approved drugs. From this, we have validated nitazoxanide as a selective inhibitor of the methyltransferase activity of nsp14. Although modestly active, this compound could serve as a starting point for further optimization.

OBJECTIVE:To compare differences in health care resource utilization (HcRU) over time between Medicare beneficiaries with and without Parkinson disease (PD).METHODS:This retrospective observational study used the Chronic Conditions Data Warehouse (5% Medicare sample) between 2005 and 2015. In a propensity score-matched (age, sex, race, and comorbidity adjusted) sample of beneficiaries with and without PD, we examined all-cause HcRU due to inpatient admissions, emergency department (ED) admissions, skilled nursing facility (SNF) admissions, health care provider encounters, neurologist visits, rehabilitation service visits, and non-PD medication fills. Relative to beneficiaries without PD, we reported adjusted incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for beneficiaries with PD using generalized linear models with log link and negative binomial variance functions.RESULTS:A total of 467,064 Medicare enrollees (unmatched sample) met the inclusion criteria. Of these, 3.3% had PD. In the matched sample and relative to beneficiaries without PD, beneficiaries with PD displayed higher rates of inpatient admissions (IRR 1.29, 95% CI 1.24-1.34), ED admissions (IRR 1.31, 95% CI 1.27-1.34), SNF admissions (IRR 2.00, 95% CI 1.92-2.09), health care provider encounters (IRR 1.18, 95% CI 1.16-1.20), neurologist visits (IRR 5.57, 95% CI 5.35-5.78), rehabilitation service visits (IRR 1.47, 95% CI 1.41-1.53), and non-PD medication fills (IRR 1.10, 95% CI 1.08-1.11) over time.CONCLUSION:These results reflect patterns of medical care among Medicare beneficiaries with PD. The findings can help clinicians, payers, and policy makers make evidence-based decisions for the allocation of scarce health care resources for PD management.CLASSIFICATION OF EVIDENCE:This study provides Class II evidence that Medicare beneficiaries with PD use more health care resources than matched controls without PD.