Cancer hazard identification is the first step in preventing cancer. Robust and transparent methods for rigorous interrogation of published research are vital for a high-quality assessment of the scientific evidence resulting in cancer hazard identification. The National Toxicology Program publishes cancer hazard assessments for possible listing in the Report on Carcinogens (RoC) that are conducted using a four-part systematic review (SR) following the process described in the RoC Handbook. This Handbook provides guidance for developing a substance-specific evaluation framework, assessing study informativeness, evaluating and integrating data across studies within each evidence stream (e.g., human, experimental animal, and mechanistic studies) and then integrating evidence across evidence streams to reach a cancer hazard conclusion.The recently updated RoC Handbook incorporates advances in SR methods and provides an updated suite of tools, approaches, and resources to assure scientific rigor, transparency, and confidence in conclusions reached in cancer hazard evaluations. The most significant advancements include a new fit-for-purpose SR strategy and guidance for assessing and integrating evidence from mechanistic studies, including read-across approaches, and clearer approaches for integrating evidence across evidence streams to reach causal conclusions. We also added toolkits for determining the informativeness of human, animal cancer, and mechanistic studies, and resources related to literature search strings, exposure assessment, and information on biomarkers and assays for the Key Characteristics of Carcinogens. These innovations have significantly enhanced the transparency and scientific integrity of RoC cancer hazard assessments and can be used by the scientific community for their own assessments.

A dose-response quantitative high-throughput screening of 147,334 small molecule compounds using a human Relaxin/Insulin-like Family Peptide Receptor 2 (RXFP2)-transfected HEK293T-RXFP2 cell line identified compound 5 with modest Insulin-Like3 (INSL3) agonist activity. An extensive structure-activity relationship (SAR) study was undertaken to improve potency, efficacy, and physical/metabolic properties of the series, resulting in the discovery of compound 68. This compound represents the first-in-class small molecule full agonist of RXFP2 that exhibits nanomolar potency and favorable pharmacokinetic characteristics, including high systemic exposure in vivo. Based on these findings, compound 68 was selected as the lead preclinical candidate for investigating the role of RXFP2 activation in bone remodeling and other physiological systems in vitro and in vivo.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has emerged as a global pandemic pathogen with high mortality. While treatments have been developed to reduce morbidity and mortality of COVID-19, more antivirals with broad-spectrum activities are still needed. Here, we identified lonafarnib (LNF), a Food and Drug Administration-approved inhibitor of cellular farnesyltransferase (FTase), as an effective anti-SARS-CoV-2 agent. LNF inhibited SARS-CoV-2 infection and acted synergistically with known anti-SARS antivirals. LNF was equally active against diverse SARS-CoV-2 variants. Mechanistic studies suggested that LNF targeted multiple steps of the viral life cycle. Using other structurally diverse FTase inhibitors and a LNF-resistant FTase mutant, we demonstrated a key role of FTase in the SARS-CoV-2 life cycle. To demonstrate in vivo efficacy, we infected SARS-CoV-2-susceptible humanized mice expressing human angiotensin-converting enzyme 2 (ACE2) and treated them with LNF. LNF at a clinically relevant dose suppressed the viral titer in the respiratory tract and improved pulmonary pathology and clinical parameters. Our study demonstrated that LNF, an approved oral drug with excellent human safety data, is a promising antiviral against SARS-CoV-2 that warrants further clinical assessment for treatment of COVID-19 and potentially other viral infections.

Brain metastasis occurs in about 50% of all women with metastatic HER2+ breast cancer and confers poor prognosis for patients. Despite effective HER2-targeted treatments of peripheral HER2+ breast cancer with trastuzumab and HER2 inhibitors, limited brain permeability renders these treatments inefficient for HER2+ breast cancer brain metastasis. The scarcity of suitable patient-derived in vivo models for HER2+ breast cancer brain metastasis has curtailed the study of molecular mechanisms that promote growth and therapeutic resistance in brain metastasis. In this study, we generated and characterized a luminal B HER2+ breast cancer brain metastasis cell model (BCBM94) isolated from a patient with HER2+ brain metastasis. Repeated hematogenic xenografting of BCBM94 consistently generated breast cancer brain metastasis in mice. The clinical receptor tyrosine kinase inhibitor (RTKi) lapatinib blocked phosphorylation of all ERBB receptors (ERBB1-4) and induced the intrinsic apoptosis pathway in BCBM94. Neuregulin 1 (Nrg1), an ERBB3/ERBB4 ligand that is abundantly expressed in the brain, abrogated lapatinib-induced apoptosis in HER2+ BCBM94 and BT474 models. ErbB3 signaling pathways that involved PI3K-AKT and the phosphorylation of BAD at serine 136 to prevent apoptosis were essential for Nrg1-induced survival. High-throughput RTKi screening identified the brain-penetrant pan-ErbB inhibitor poziotinib as a highly potent compound that reduced cell viability in HER2+ breast cancer brain metastasis in the presence of NRG1. Two weeks of poziotinib treatment successfully ablated BCBM94 and BT474 HER2+ brain tumors in vivo. In conclusion, this study established a patient-derived HER2+ breast cancer brain metastasis model and identified poziotinib as a highly efficacious RTKi with excellent brain penetrability that eliminated HER2+ breast cancer brain metastasis.Significance: Development of a preclinical patient-derived model to study HER2+ breast cancer brain metastasis enabled the identification of the irreversible pan-ERBB inhibitor poziotinib as highly efficacious in treating brain metastatic tumors.

ABSTRACT Because of the urgent need for new antibiotics to treat drug-resistant bacterial pathogens, we employed an assay that rapidly screens large quantities of compounds for their ability to interfere with bacterial protein synthesis, in particular, the delivery of amino acids to the ribosome via tRNA and elongation factor Tu (EF-Tu). We have identified a drug lead, named MGC-10, which kills Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), with a MIC of 6 µM, while being harmless to mammalian cells in vitro in that concentration range. The antibacterial activity of MGC-10 was broad against over 50 strains of antibiotic-resistant samples obtained from hospital infections, where MGC-10 inhibited all tested strains of MRSA. Extensive selection and screening with MGC-10 did not yield any resistant strains, indicating it may have universal antibacterial activity against S. aureus . Pharmacokinetics performed in mice suggested that MGC-10 was too toxic for systemic use; however, it appears to have potential as a topical treatment for difficult-to-treat wounds or skin infections by Gram-positive pathogens such as MRSA. In a mouse skin-infection model with MRSA, MGC-10 performed as well or better than the present topical drug of choice, mupirocin. MGC-10 showed little, if any, accumulation in the livers of topically treated mice. These results bode well for the future use of MGC-10 in clinical application as it could be used to treat a broad range of S. aureus skin infections that are resistant to known antibiotics. IMPORTANCE There is a critical need for new antibiotics to treat bacterial infections caused by pathogens resistant to many if not all currently available antibiotics. We describe here the identification of a prospective new antibiotic from high-throughput screening of a chemical library. The screening was designed to detect the inhibition of formation of a complex required for bacterial protein synthesis in all bacteria, the “ternary complex,” comprised of elongation factor Tu (EF-Tu), aminoacyl-tRNA, and GTP. The inhibitory compound, renamed MGC-10, was effective against all Gram-positive bacteria, including a wide variety of methicillin-resistant Staphylococcus aureus (MRSA) strains. Although apparently too toxic for systemic use, the compound was safe and effective for topical use for treating skin infections in a mouse model. No resistance to the compound has been detected thus far, suggesting the potential to develop this compound for topical use to treat infections, especially those caused by pathogens resistant to existing antibiotics.

BACKGROUND:The 10 key characteristics (KCs) of carcinogens form the basis of a framework to identify, organize, and evaluate mechanistic evidence relevant to carcinogenic hazard identification. The 10 KCs are related to mechanisms by which carcinogens cause cancer. The International Agency for Research on Cancer (IARC) Monographs programme has successfully applied the KCs framework for the mechanistic evaluation of different types of exposures, including chemicals, metals, and complex exposures, such as environmental, occupational, or dietary exposures. The use of this framework has significantly enhanced the identification and organization of relevant mechanistic data, minimized bias in evaluations, and enriched the knowledge base regarding the mechanisms of known and suspected carcinogens. OBJECTIVES:We sought to report the main outcomes of an IARC Scientific Workshop convened by the IARC to establish appropriate, transparent, and uniform application of the KCs in future IARC Monographs evaluations. METHODS:A group of experts from different disciplines reviewed the IARC Monographs experience with the KCs of carcinogens, discussing three main themes: a) the interpretation of end points forming the evidence base for the KCs, b) the incorporation of data from novel assays on the KCs, and c) the integration of the mechanistic evidence as part of cancer hazard identification. The workshop participants assessed the relevance and the informativeness of multiple KCs-associated end points for the evaluation of mechanistic evidence in studies of exposed humans and experimental systems. DISCUSSION:Consensus was reached on how to enhance the use of in silico, molecular, and cellular high-output and high-throughput data. In addition, approaches to integrate evidence across the KCs and opportunities to improve methodologies of mechanistic evaluation of cancer hazards were explored. The findings described herein and in a forthcoming IARC technical report will support future working groups of experts in reporting and interpreting results under the KCs framework within the IARC Monographs or in other contexts. https://doi.org/10.1289/EHP15389.

Background Inhibitors targeting cyclin-dependent kinases 4 and 6 (CDK4/6), crucial for cell cycle regulation, have shown promise in early-stage studies for treating central nervous system (CNS) tumors. However, challenges such as limited CNS penetration, optimal treatment duration, and systemic side effects have impeded their clinical translation for pediatric brain tumors (PBTs).Methods We evaluated the potency of CDK4/6 inhibitors across various PBT cell lines, focusing particularly on palbociclib against atypical teratoid rhabdoid tumor (ATRT) with cell viability assays and gene expression analysis. Additionally, we assessed the efficacy and safety of intrathecal (IT) delivery of palbociclib through neurotoxicity and pharmacokinetic studies, along with survival assessments in murine leptomeningeal ATRT models.Results Palbociclib showed the highest potency across various PBT cells, with extended treatments reducing growth inhibition 50 (GI50) values from the micromolar to nanomolar range. It suppressed critical cell cycle genes (CCNB1, CCNA2, CDK1) in BT16 ATRT cells. Neurotoxicity (GFAP, CD45, NeuN, Iba1) and pharmacokinetic assays confirmed IT route as a feasible and effective method for delivering palbociclib to the cerebrospinal fluid (CSF), avoiding systemic toxicity and enhancing drug concentration to the brain. Finally, metronomic IT delivery using an osmotic pump (OP, 48 mg/kg) increased survival in 2 murine leptomeningeal ATRT models, showcasing its potential as a novel therapy for leptomeningeal tumors.Conclusions Metronomic IT delivery of palbociclib enhances drug efficacy and safety, improves survival, and offers a promising treatment strategy for PBTs with CSF dissemination.

STAT6 is an essential transcription factor in the IL-4/IL-13 signaling pathways and the central driver of Th2 inflammation in allergic/atopic diseases. Multiple gain of function mutations of STAT6 have been identified to cause severe atopic/allergic diseases in humans. Dupilumab, an injectable monoclonal antibody that blocks IL-4/IL-13 signaling, is an approved therapy for multiple atopic/allergic diseases therefore targeting STAT6 in these diseases is supported by both human genetics and dupilumab’s clinical activity. STAT6 functions through protein-protein and protein-DNA interactions. It has been challenging to selectively and potently inhibit STAT6 with traditional small molecule inhibitors. However, STAT6 is well suited for a novel targeted protein degradation approach, where a simple binding event is sufficient to drive degradation of the protein and fully block its functions.

BACKGROUND:Non-directed donors (NDDs), individuals who donate their organs with no intended recipient, in the United States increased 90-fold from 1999 to 2019. There is a paucity of studies investigating the motivations of NDDs. The objective of our study is to identify actionable items to increase NDDs. METHODS:A survey of kidney NDDs at CUIMC from 2009 to 2021 was conducted. The survey was conducted via Qualtrics. RESULTS:Seventy individuals met the study criteria. Forty-seven (67.1%) individuals completed the survey. A total of 98% of respondents reported participating in other altruistic activities prior to donation. A total of 70% donors identified as religious, and 57% reported religion/spirituality positively affected the decision to donate. The three most common factors that got respondents interested in NDD included: (1) hearing about an individual in need of a transplant, (2) knowing someone who had donated an organ, and (3) as a next step in altruistic behavior. A total of 85% said that donating a kidney met or exceeded expectations. A total of 44% and 31% of NDDs were interested in being either liver or uterus NDDs, respectively. CONCLUSIONS:We identified six potential action items: (1) Identify pools of receptive individuals who participated in other altruistic behaviors and/or identify as religious. (2) Outreach to individuals who came forward as directed donors, but whose intended recipient was successfully transplanted with a kidney from another donor. (3) Promote stories of those who need organ transplants or whose lives have been changed by transplantation. (4) Promote NDDs as resources for potential NDDs. (5) Educate interested kidney NDDs about liver and uterus transplant programs. (6) Decrease financial barriers to donation.

The molecular mechanisms underlying seizure generation remain elusive, yet they are crucial for developing effective treatments for epilepsy. The current study shows that inhibiting c-Abl tyrosine kinase prevents apoptosis, reduces dendritic spine loss, and maintains N-methyl-d-aspartate (NMDA) receptor subunit 2B (NR2B) phosphorylated in in vitro models of excitotoxicity. Pilocarpine-induced status epilepticus (SE) in mice promotes c-Abl phosphorylation, and disrupting c-Abl activity leads to fewer seizures, increases latency toward SE, and improved animal survival. Currently, clinically used c-Abl inhibitors are non-selective and have poor brain penetration. The allosteric c-Abl inhibitor, neurotinib, used here has favorable potency, selectivity, pharmacokinetics, and vastly improved brain penetration. Neurotinib-administered mice have fewer seizures and improved survival following pilocarpine-SE induction. Our findings reveal c-Abl kinase activation as a key factor in ictogenesis and highlight the impact of its inhibition in preventing the insurgence of epileptic-like seizures in rodents and humans.

Efficiently circumventing the blood-brain barrier (BBB) poses a major hurdle in the development of drugs that target the central nervous system. Although there are several methods to determine BBB permeability of small molecules, the Parallel Artificial Membrane Permeability Assay (PAMPA) is one of the most common assays in drug discovery due to its robust and high-throughput nature. Drug discovery is a long and costly venture, thus, any advances to streamline this process are beneficial. In this study, ∼2,000 compounds from over 60 NCATS projects were screened in the PAMPA-BBB assay to develop a quantitative structure-activity relationship model to predict BBB permeability of small molecules. After analyzing both state-of-the-art and latest machine learning methods, we found that random forest based on RDKit descriptors as additional features provided the best training balanced accuracy (0.70 ± 0.015) and a message-passing variant of graph convolutional neural network that uses RDKit descriptors provided the highest balanced accuracy (0.72) on a prospective validation set. Finally, we correlated in vitro PAMPA-BBB data with in vivo brain permeation data in rodents to observe a categorical correlation of 77%, suggesting that models developed using data from PAMPA-BBB can forecast in vivo brain permeability. Given that majority of prior research has relied on in vitro or in vivo data for assessing BBB permeability, our model, developed using the largest PAMPA-BBB dataset to date, offers an orthogonal means to estimate BBB permeability of small molecules. We deposited a subset of our data into PubChem bioassay database (AID: 1845228) and deployed the best performing model on the NCATS Open Data ADME portal (https://opendata.ncats.nih.gov/adme/). These initiatives were undertaken with the aim of providing valuable resources for the drug discovery community.

STAT6 is an undrugged essential transcription factor in the IL-4/IL-13 signaling pathways and the central driver of TH2 inflammation in allergic diseases. Multiple gain of function mutations of STAT6 were identified to cause severe allergic diseases in human. Dupilumab, an injectable monoclonal antibody that blocks IL-4/IL-13 signaling, is an approved therapy for multiple allergic diseases. STAT6 targeting is therefore supported by both human genetics and dupilumab's clinical pathway validation. STAT6 functions through protein-protein and protein-DNA interactions. For these reasons, it has been challenging to selectively and potently inhibit STAT6 with traditional small molecule inhibitors. It is, however, well suited for a targeted protein degradation approach, where a binding event is sufficient to drive degradation. We have developed highly potent STAT6 degraders that can selectively degrade and deplete STAT6 in various disease relevant human immune and tissue cells, fully block various IL-4/IL-13 functions in these cells with picomolar potencies comparable or superior to dupilumab, and do not degrade or inhibit any other STAT transcription factors. In addition, our STAT6 degraders show potent STAT6 degradation and IL-4/ IL-13 functional inhibition in human whole blood. Our STAT6 degraders are orally bioavailable in multiple preclinical species and are able to deplete STAT6 in vivo. In a MC903-induced atopic dermatitis mouse model, orally administered STAT6 degraders demonstrated excellent in vivo efficacy, blocking TH2 inflammation and reducing disease severity. STAT6 degradation is a potential novel oral approach for blocking the IL-4/IL-13 pathways in development for the treatment of atopic dermatitis and other allergic diseases.

This comprehensive study delves into the intricate dynamics of CDK4/6 inhibitors (abemaciclib, ribociclib, palbociclib) efficacy in the context of pediatric brain tumors, with a specific focus on establishing the temporal dependencies of their effectiveness. Beyond elucidating the time-dependent aspects, the research also explores into the feasibility and safety considerations associated with a metronomic intrathecal delivery with Palbociclib. This involves a thorough examination of pharmacokinetics and an analysis of liver and renal function through a panel assessment in vivo. By methodically exploring the optimal dosing within the brain after administration of Palbociclib via a systemic or intrathecal administration; the study aims to provide nuanced insights into enhancing therapeutic outcomes for pediatric brain tumors. Ultimately, we also provide a mechanistic understanding of the inhibition of CDK4/6 over time using RNAseq analysis; and an assessment of the efficacy of the proposed metronomic intrathecal delivery strategy in a preclinical mouse model of leptomeningeal ATRT. This multifaceted study not only expands our understanding of the temporal dynamics of CDK4/6 inhibitors but also lays the foundation for informed decision-making regarding the potential of this innovative therapeutic delivery method in the realm of pediatric brain tumor treatment.

Context: Thyroid-stimulating hormone (or thyrotropin) receptor (TSHR) could be a selective target for small molecule ligands to treat thyroid cancer (TC). Objective: We report a novel, orally efficacious ligand for TSHR that exhibits proliferation inhibitory activity against human TC in vitro and in vivo, and inhibition of metastasis in vivo. Methods: A35 (NCATS-SM4420; NCGC00241808) was selected from a sublibrary of >200 TSHR ligands. Cell proliferation assays including BrdU incorporation and WST-1, along with molecular docking studies were done. In vivo activity of A35 was assessed in TC cell-derived xenograft (CDX) models with immunocompromised (NSG) mice. Formalin-fixed, paraffin-embedded sections of tumor and lung tissues were observed for the extent of cell death and metastasis. Results: A35 was shown to stimulate cAMP production in some cell types by activating TSHR but not in TC cells, MDA-T32, and MDA-T85. A35 inhibited proliferation of MDA-T32 and MDA-T85 in vitro and in vivo, and pulmonary metastasis of MDA-T85F1 in mice. In vitro, A35 inhibition of proliferation was reduced by a selective TSHR antagonist. Inhibition of CDX tumor growth without decreases in mouse weights and liver function showed A35 to be efficacious without apparent toxicity. Lastly, A35 reduced levels of Ki67 in the tumors and metastatic markers in lung tissues. Conclusion: We conclude that A35 is a TSHR-selective inhibitor of TC cell proliferation and metastasis, and suggest that A35 may be a promising lead drug candidate for the treatment of differentiated TC in humans.

A quantitative high throughput screen (qHTS) of 7,988 compounds with annotated libraries using biliary tract cancer cell lines with or without isocitrate dehydrogenase I (IDH1) mutations had identified YC-1 as being selectively cytotoxic against the IDH1 mutant cell lines. We present the structure-activity relationship study of YC-1 analogs and identify the key structural motifs that are essential for activity. We highlight the narrow SAR around the furfuryl alcohol that has been reported as a critical motif that is activated by the sulfotransferase enzyme SULT1A1. Drug-like properties of key analogs are evaluated. We also show the SAR of a smaller subset of 2-choloro-4-amino benzyl alcohols from the NCI compound collection with a similar benzyl alcohol motif. We also demonstrate the ability of key analogs to act as substrates of SULT1A1 in a colorimetric biochemical assay.

Compare the treatment efficacy of a derivative of Docosahexaenoic acid (DHA), Synaptamide (SYN) versus its analog, Dimethylsynaptamide (DMS) in suppression of experimental allergic encephalomyelitis (EAE) in mice.