Computer-aided design of 1,4-naphthoquinone-based inhibitors targeting cruzain and rhodesain cysteine proteases.

Chagas disease and Human African Trypanosomiasis (HAT) are caused by Trypanosoma cruzi and T. brucei parasites, respectively. Cruzain (CRZ) and Rhodesain (RhD) are cysteine proteases that share 70% of identity and play vital functions in these parasites. These macromolecules represent promising targets for designing new inhibitors. In this context, 26 CRZ and 5 RhD 3D-structures were evaluated by molecular redocking to identify the most accurate one to be utilized as a target. Posteriorly, a virtual screening of a library containing 120 small natural and nature-based compounds was performed on both of them. In total, 14 naphthoquinone-based analogs were identified, synthesized, and biologically evaluated. In total, five compounds were active against RhD, being three of them also active on CRZ. A derivative of 1,4-naphthoquinonepyridin-2-ylsulfonamide was found to be the most active molecule, exhibiting IC50 values of 6.3 and 1.8 µM for CRZ and RhD, respectively. Dynamic simulations at 100 ns demonstrated good stability and do not alter the targets' structures. MM-PBSA calculations revealed that it presents a higher affinity for RhD (-25.3 Kcal mol-1) than CRZ, in which van der Waals interactions were more relevant. A mechanistic hypothesis (via C3-Michael-addition reaction) involving a covalent mode of inhibition for this compound towards RhD was investigated by covalent molecular docking and DFT B3LYP/6-31 + G* calculations, exhibiting a low activation energy (ΔG‡) and providing a stable product (ΔG), with values of 7.78 and - 39.72 Kcal mol-1, respectively; similar to data found in the literature. Nevertheless, a reversibility assay by dilution revealed that JN-11 is a time-dependent and reversible inhibitor. Finally, this study applies modern computer-aided techniques to identify promising inhibitors from a well-known chemical class of natural products. Then, this work could inspire other future studies in the field, being useful for designing potent naphthoquinones as RhD inhibitors.

Druggable targets from coronaviruses for designing new antiviral drugs.

Severe respiratory infections were highlighted in the SARS-CoV outbreak in 2002, as well as MERS-CoV, in 2012. Recently, the novel CoV (COVID-19) has led to severe respiratory damage to humans and deaths in Asia, Europe, and Americas, which allowed the WHO to declare the pandemic state. Notwithstanding all impacts caused by Coronaviruses, it is evident that the development of new antiviral agents is an unmet need. In this review, we provide a complete compilation of all potential antiviral agents targeting macromolecular structures from these Coronaviruses (Coronaviridae), providing a medicinal chemistry viewpoint that could be useful for designing new therapeutic agents.

Peptide derivatives as inhibitors of NS2B-NS3 protease from Dengue, West Nile, and Zika flaviviruses.

Currently, more than 70 flaviviruses were identified and reported in the literature, whose Dengue (DENV), Zika (ZIKV), and West Nile (WNV) viruses have been responsible for millions of cases of infections worldwide, mainly in developing countries. These viruses are transmitted by the bite of mosquitoes from genus Aedes, or Culex and, in some cases, Stegomyia. Despite numerous efforts to identify a selective, safe, and effective antiviral agent, there is no currently approved drug for the treatment of flaviviral infections. Then, current pharmacological therapy has the objective to treat the clinical symptoms. Various peptidomimetics and peptide-derivatives have been synthesized and evaluated against several biological targets from flaviviruses with different applications, such as diagnosis, E protein inhibitors, entry inhibitors, virucidal inhibitors, and also viral replication inhibitors. Flaviviral replication depends on the NS3pro that is completely activated when it is complexed to its cofactor, NS2B; forming a viral enzymatic complex. The development of NS2B-NS3pro inhibitors is considered a challenging work due to its active site is shallow and open-pocket. In this work, we report all advances involving peptidomimetics, peptide-derived, and peptide-hybrids found in the literature. In sense, we discuss the influence of different functional groups in the activity and selectivity. Moreover, the first inhibitors reported in the literature as covalent ligands, comprising two basic residues followed by an electrophilic moiety that binds to the catalytic serine (Ser135-O-) are also discussed in details, such as trifluoromethyl ketones, aldehydes, and boronic acids. Furthermore, it is presented the influence of introducing transition metals, providing metallopeptide inhibitors; and cyclization of linear peptides, generating cyclic and macrocyclic peptide inhibitors. Finally, we provide the most accurate state of the art found in the literature, which can be utilized to design new and effective antiviral agents.

Recent advances in the molecular design and applications of viral RNA-targeting antiviral modalities.

Pathogenic viruses are a profound threat to global public health, underscoring the urgent need for the development of efficacious antiviral therapeutics. The advent of RNA-targeting antiviral strategies has marked a significant paradigm shift in the management of viral infections, offering a potent means of control and potential cure. In this review, we delve into the cutting-edge progress in RNA-targeting antiviral agents, encompassing antisense oligonucleotides (ASOs), small interfering RNAs (siRNAs), small and bifunctional molecules. We provide an in-depth examination of their strategic molecular design and elucidate the underlying mechanisms of action that confer their antiviral efficacy. By synthesizing recent findings, we shed light on the innovative potential of RNA-targeting approaches and their pivotal role in advancing the frontiers of antiviral drug discovery.

Cyrene™ as a tyrosinase inhibitor and anti-browning agent.

The tyrosinase pathway takes part in the enzymatic process of food browning and is primarily responsible for food spoilage - manifesting itself from a decrease in its nutritional value to a deterioration of taste, which consequently leads to a gradual loss of shelf life. Finding safe and bio-based tyrosinase inhibitors and anti-browning agents may be of great importance in agriculture and food industries. Herein, we showed that Cyrene™ exhibits tyrosinase inhibitory activity (IC50: 268.2 µM), the 1.44 times higher than ascorbic acid (IC50: 386.5 µM). Binding mode studies demonstrated that the carbonyl oxygen of Cyrene™ coordinates with both copper ions. Surprisingly, both hydroxyl groups of Cyrene gem-diol perform a monodentate binding mode with both copper ions, at similar distances. This fact suggests that both compounds could have a similar binding mode and, as consequence, similar biological activities in tyrosinase inhibition assays and anti-browning activities.

Insights on Natural Products Against Amyotrophic Lateral Sclerosis (ALS).

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that causes the death of motor neurons and consequent muscle paralysis. Despite many efforts to address it, current therapy targeting ALS remains limited, increasing the interest in complementary therapies. Over the years, several herbal preparations and medicinal plants have been studied to prevent and treat this disease, which has received remarkable attention due to their blood-brain barrier penetration properties and low toxicity. Thus, this review presents the therapeutic potential of a variety of medicinal herbs and their relationship with ALS and their physiopathological pathways.

PI3K Signaling Pathways as a Molecular Target for Glioblastoma Multiforme.

Glioblastoma multiforme (GBM) is the most common type of cancer that affects the central nervous system (CNS). It currently accounts for about 2% of diagnosed malignant tumors worldwide, with 296,000 new cases reported per year. The first-choice treatment consists of surgical resection, radiotherapy, and adjuvant chemotherapy, which increases patients' survival by 15 months. New clinical and pre-clinical research aims to improve this prognosis by proposing the search for new drugs that effectively eliminate cancer cells, circumventing problems such as resistance to treatment. One of the promising therapeutic strategies in the treatment of GBM is the inhibition of the phosphatidylinositol 3-kinase (PI3K) pathway, which is closely related to the process of tumor carcinogenesis. This review sought to address the main scientific studies of synthetic or natural drug prototypes that target specific therapy co-directed via the PI3K pathway, against human glioblastoma.

Potentiating-antibiotic activity and absorption, distribution, metabolism, excretion and toxicity properties (ADMET) analysis of synthetic thiadiazines against multi-drug resistant (MDR) strains.

BACKGROUND: Thiadiazines are heterocyclic compounds that contain two nitrogen atoms and one sulfur atom in their structure. These synthetic molecules have several relevant pharmacological activities, such as antifungal, antibacterial, and antiparasitic. OBJECTIVES: The present study aimed to evaluate the possible in vitro and in silico interactions of compounds derived from thiadiazines. METHODS: The compounds were initially synthesized, purified, and confirmed through HPLC methodology. Multi-drug resistant bacterial strains of Staphylococcus aureus 10 and Pseudomonas aeruginosa 24 were used to evaluate the direct and modifying antibiotic activity of thiadiazine derivatives. ADMET assays (absorption, distribution, metabolism, excretion, and toxicity) were conducted, which evaluated the influence of the compounds against thousands of macromolecules considered as bioactive targets. RESULTS: There were modifications in the chemical synthesis in carbon 4 or 3 in one of the aromatic rings of the structure where different ions were added, ensuring a variability of products. It was possible to observe results that indicate the possibility of these compounds acting through the cyclooxygenase 2 mechanism, which, in addition to being involved in inflammatory responses, also acts by helping sodium reabsorption. The amine group present in thiadiazine analogs confers hydrophilic characteristics to the substances, but this primary characteristic has been altered due to alterations and insertions of other ligands. The characteristics of the analogs generally allow easy intestinal absorption, reduce possible hepatic toxic effects, and enable possible neurological and anti-inflammatory action. The antibacterial activity tests showed a slight direct action, mainly of the IJ23 analog. Some compounds were able to modify the action of the antibiotics gentamicin and norfloxacin against multi-drug resistant strains, indicating a possible synergistic action. CONCLUSIONS: Among all the results obtained in the study, the relevance of thiadiazine analogs as possible coadjuvant drugs in the antibacterial, anti-inflammatory, and neurological action with low toxicity is clear. Need for further studies to verify these effects in living organisms is not ruled out.

Inhibitors Targeting Hepatitis C Virus (HCV) Entry.

Infections caused by the Hepatitis C virus (HCV) affect around 70 million people worldwide, leading to serious liver problems, such as fibrosis, steatosis, and cirrhosis, in addition to progressing to hepatocellular carcinoma and becoming globally the main cause of liver disease. Despite great therapeutic advances in obtaining pan-genotypic direct-acting antivirals (DAAs), around 5-10% of affected individuals are unable to eliminate the virus by their own immune system's activity. Still, there are no licensed vaccines so far. In this context, the orchestrated process of virus entry into host cells is a crucial step in the life cycle and the infectivity capability of most viruses. In recent years, the entry of viruses has become one of the main druggable targets used for designing effective antiviral molecules. This goal has come to be widely studied to develop pharmacotherapeutic strategies against HCV, combined or not with DAAs in multitarget approaches. Among the inhibitors found in the literature, ITX 5061 corresponds to the most effective one, with EC50 and CC50 values of 0.25 nM and >10 µM (SI: 10,000), respectively. This SRBI antagonist completed the phase I trial, constituting a promising compound against HCV. Interestingly, chlorcyclizine (an antihistamine drug) showed action both in E1 apolipoproteins (EC50 and CC50 values of 0.0331 and 25.1 µM, respectively), as well as in NPC1L1 (IC50 and CC50 values of 2.3 nM and > 15 µM, respectively). Thus, this review will discuss promising inhibitors targeting HCV entry, discussing their SAR analyzes, recent contributions, and advances in this field.

Medicinal chemistry insights into antiviral peptidomimetics.

The (re)emergence of multidrug-resistant viruses and the emergence of new viruses highlight the urgent and ongoing need for new antiviral agents. The use of peptidomimetics as therapeutic drugs has often been associated with advantages, such as enhanced binding affinity, improved metabolic stability, and good bioavailability profiles. The development of novel antivirals is currently driven by strategies of converting peptides into peptidomimetic derivatives. In this review, we outline different structural modification design strategies for developing novel peptidomimetics as antivirals, involving N- or C-cap terminal structure modifications, pseudopeptides, amino acid modifications, inverse-peptides, cyclization, and molecular hybridization. We also present successful recent examples of peptidomimetic designs.

Natural Compounds as Inhibitors of Aß Peptide and Tau Aggregation.

Neurodegenerative conditions like Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) encompass disorders characterized by the degeneration of neurons in specific circumstances. The quest for novel agents to influence these diseases, particularly AD, has unearthed various natural compounds displaying multifaceted activities and diverse pharmacological mechanisms. Given the ongoing extensive study of pathways associated with the accumulation of neurofibrillary aggregates and amyloid plaques, this paper aims to comprehensively review around 130 studies exploring natural products. These studies focus on inhibiting the formation of amyloid plaques and tau protein tangles, with the objective of potentially alleviating or delaying AD.

Computer-aided drug design in seeking viral capsid modulators.

Approved or licensed antiviral drugs have limited applications because of their drug resistance and severe adverse effects. By contrast, by stabilizing or destroying the viral capsid, compounds known as capsid modulators prevent viral replication by acting on new targets and, therefore, overcoming the problem of clinical drug resistance. For example, computer-aided drug design (CADD) methods, using strategies based on structures of biological targets (structure-based drug design; SBDD), such as docking, molecular dynamics (MD) simulations, and virtual screening (VS), have provided opportunities for fast and effective development of viral capsid modulators. In this review, we summarize the application of CADD in the discovery, optimization, and mechanism prediction of capsid-targeting small molecules, providing new insights into antiviral drug discovery modalities.

Naphthoquinone Derivatives Targeting Melanoma.

Cancer is responsible for high mortality rates worldwide, representing a serious health problem. In this sense, melanoma corresponds to the most aggressive type of skin cancer, being the cause of the highest death rates. Therapeutic strategies for the treatment of melanoma remain limited, with problems associated with toxicity, serious side effects, and mechanisms of resistance. The potential of natural products for the prevention and treatment of melanoma has been reported in different studies. Among these compounds, naphthoquinones (1,2-naphthoquinones and 1,4-naphthoquinones) stand out for their diverse pharmacological properties, including their antitumor activity. Thus, this review covers different studies found in the literature on the application of natural naphthoquinones targeting melanoma, providing information regarding the mechanisms of action investigated for these compounds. Finally, we believe that this review provides a comprehensive basis for the use of natural naphthoquinones against melanoma and that it may contribute to the discovery of promising compounds, specifically naphthoquinones, aimed at the treatment of this cancer.

LQM10, a guanylhydrazone derivative, reduces nociceptive and inflammatory responses in mice.

In the present study, we examined the antinociceptive and anti-inflammatory activities of a guanylhydrazone derivative, (E)-(3,5-di-tert-butyl-4-hydroxybenzylidene)-2-guanylhydrazone hydrochloride (LQM10), in mice. The antinociceptive effect was determined by assessing behavioural responses in different pain models, while anti-inflammatory activity was examined in carrageenan-induced pleurisy. Intraperitoneal LQM10 administration reduced the acetic acid-induced nociceptive behaviour, a phenomenon that was unaltered by pretreatment with yohimbine, atropine, naloxone or glibenclamide. In the formalin assay, LQM10 reduced nociceptive behaviour only in the second phase, indicating an inhibitory effect on inflammatory pain. LQM10 did not alter the pain latency in the hot plate assay and did not impact the locomotor activity of mice in the rotarod assay. In the carrageenan-induced pleurisy assay, LQM10 treatment inhibited critical events involved in inflammatory responses, namely, leucocyte recruitment, plasma leakage and increased inflammatory mediators (tumour necrosis factor Like Properties of Chalchones and Flavonoid Derivatives [TNF]-α and interleukin [IL]-1ß) in the pleural exudate. Overall, these results indicate that LQM10 exhibits antinociceptive effects associated with peripheral mechanisms and anti-inflammatory activity mediated via a reduction in leucocyte migration and proinflammatory mediators, rendering this compound a promising candidate for treating pain and inflammatory process.

BACE-1 Inhibitors Targeting Alzheimer's Disease.

The accumulation of amyloid-ß (Aß) is the main event related to Alzheimer's disease (AD) progression. Over the years, several disease-modulating approaches have been reported, but without clinical success. The amyloid cascade hypothesis evolved and proposed essential targets such as tau protein aggregation and modulation of ß-secretase (ß-site amyloid precursor protein cleaving enzyme 1 - BACE-1) and γ-secretase proteases. BACE-1 cuts the amyloid precursor protein (APP) to release the C99 fragment, giving rise to several Aß peptide species during the subsequent γ-secretase cleavage. In this way, BACE-1 has emerged as a clinically validated and attractive target in medicinal chemistry, as it plays a crucial role in the rate of Aß generation. In this review, we report the main results of candidates in clinical trials such as E2609, MK8931, and AZD-3293, in addition to highlighting the pharmacokinetic and pharmacodynamic-related effects of the inhibitors already reported. The current status of developing new peptidomimetic, non-peptidomimetic, naturally occurring, and other class inhibitors are demonstrated, considering their main limitations and lessons learned. The goal is to provide a broad and complete approach to the subject, exploring new chemical classes and perspectives.

Preclinical data on morpholine (3,5-di-tertbutyl-4-hydroxyphenyl) methanone induced anxiolysis.

Trimetozine is used to be indicated for the treatment of mental illnesses, particularly anxiety. The present study provides data on the pharmacological profile of trimetozine derivative morpholine (3,5-di-tert-butyl-4-hydroxyphenyl) methanone (LQFM289) which was designed from molecular hybridization of trimetozine lead compound and 2,6-di-tert-butyl-hydroxytoluene to develop new anxiolytic drugs. Here, we conduct molecular dynamics simulations, docking studies, receptor binding assays, and in silico ADMET profiling of LQFM289 before its behavioral and biochemical assessment in mice within the dose range of 5-20 mg/kg. The docking of LQFM289 showed strong interactions with the benzodiazepine binding sites and matched well with receptor binding data. With the ADMET profile of this trimetozine derivative that predicts a high intestinal absorption and permeability to blood-brain barrier without being inhibited by the permeability glycoprotein, the oral administration of LQFM289 10 mg/kg consistently induced anxiolytic-like behavior of the mice exposed to the open field and light-dark box apparatus without eliciting motor incoordination in the wire, rotarod, and chimney tests. A decrease in the wire and rotarod´s fall latency coupled with an increase in the chimney test´s climbing time and a decrease in the number of crossings in the open field apparatus at the dose of 20 mg/kg of this trimetozine derivative suggest sedative or motor coordination impairment at this highest dose. The attenuation of the anxiolytic-like effects of LQFM289 (10 mg/kg) by flumazenil pretreatment implicates the participation of benzodiazepine binding sites. The lowering of corticosterone and tumor necrosis factor alpha (cytokine) in LQFM289-treated mice at a single oral (acute) dose of 10 mg/kg suggests that the anxiolytic-like effect of this compound also involves the recruitment of non-benzodiazepine binding sites/GABAergic molecular machinery.

Inhibiting the "Undruggable" RAS/Farnesyltransferase (FTase) Cancer Target by Manumycin-related Natural Products.

Cancer is an uncontrolled cell growth that can generate diverse types of cancer, in which these will also present a different behavior in the face of pharmacological treatment. These cancers' types are found in one of the three categories, leukemias (also named lymphomas), carcinomas, and sarcomas. In general, cancer's pathogenesis is associated with three genetic mutations, where could emerge from oncogenes, tumor suppressor genes, and/or genes responsible for regulating DNA replication. The term "undruggable" is frequently related to the difficulty to design drugs to specific targets, such as MYC, MYB, NF-κB, and RAS family of proteins. This last comprises more than 140 proteins, and these are responsible for 30% of mutations in human cancers. Also, there are three ras genes transcribed in human cells, called H-, K-, and N-ras oncogenes. Still, the RAS proteins (farnesyltransferase (FTase) and geranylgeranyltransferase (GGTase) enzymes) perform essential steps in post-translational modification of eukaryotes cells, such as (1) the farnesylation of the cysteine residue at the C-terminal tetrapeptide CAAX; (2) proteolytic cleavage of the three C-terminal AAX oligopeptide; and (3) carboxymethylation of the new C-terminal prenylated cysteine. Thus, the inhibition of this undruggable RAS family of proteins has been considered a promising alternative to design new anticancer agents since they are responsible for many types of human cancers. Then, the manumycin A (obtained from the Streptomyces parvulus Tü64) and its analogs (epoxyquinol core with or without their southern and eastern side chains; and dihydroxycyclohexenones core) have been described as promising FTase inhibitors, which have demonstrated their benefits against several types of cancer. In this review, a complete introduction about cancer and its relation with RAS proteins is provided, as well as, the prenylation mechanism of the cysteine residue is discussed in detail. Posteriorly, studies involving manumycin-related compounds are described, showing some synthetic routes for obtaining them and utilizing these natural products in monotherapies or combined therapies with other anticancer drugs.

Multi-target Approaches of Epigallocatechin-3-O-gallate (EGCG) and its Derivatives against Influenza Viruses.

Influenza viruses (INFV), the Orthomyxoviridae family, are mainly transmitted among humans via aerosols or droplets from the respiratory secretions. However, fomites could be a potential transmission pathway. Annually, seasonal INFV infections account for 290-650 thousand deaths worldwide. Currently, there are two classes of approved drugs to treat INFV infections, being neuraminidase (NA) inhibitors and blockers of matrix-2 (M2) ion channel. However, cases of resistance have been observed for both chemical classes, reducing the efficacy of treatment. The emergence of influenza outbreaks and pandemics calls for new antiviral molecules that are more effective, and that could overcome the current resistance to anti-influenza drugs. In this context, polyphenolic compounds are found in various plants, and these have displayed different multi-target approaches against diverse pathogens. Among these, green tea (Camellia sinensis) catechins, in special epigallocatechin-3-O-gallate (EGCG), have demonstrated significant activities against the two most relevant human INFV, subtypes A and lineages B. In this sense, EGCG has been found to be a promising multi-target agent against INFV since it can act inhibiting NA, hemagglutination (HA), RNA-dependent RNA polymerase (RdRp), and viral entry/adsorption. In general, the lack of knowledge about potential multi-target natural products prevents an adequate exploration of them, increasing the time for developing multi-target drugs. Then, this review aimed to compile most relevant studies showing the anti-INFV effects of EGCG and its derivatives, which could become antiviral drug prototypes in the future.

TNF-α Inhibitors from Natural Compounds: An Overview, CADD Approaches, and their Exploration for Anti-inflammatory Agents.

Inflammation is a natural process that occurs in the organism in response to harmful external agents. Despite being considered beneficial, exaggerated cases can cause severe problems for the body. The main inflammatory manifestations are pain, increased temperature, edema, decreased mobility, and quality of life for affected individuals. Diseases such as arthritis, cancer, allergies, infections, arteriosclerosis, neurodegenerative diseases, and metabolic problems are mainly characterized by an exaggerated inflammatory response. Inflammation is related to two categories of substances: pro- and anti-inflammatory mediators. Among the pro-inflammatory mediators is Tumor Necrosis Factor-α (TNF-α). It is associated with immune diseases, cancer, and psychiatric disorders which increase its excretion. Thus, it becomes a target widely used in discovering new antiinflammatory drugs. In this context, secondary metabolites biosynthesized by plants have been used for thousands of years and continue to be one of the primary sources of new drug scaffolds against inflammatory diseases. To decrease costs related to the drug discovery process, Computer-Aided Drug Design (CADD) techniques are broadly explored to increase the chances of success. In this review, the main natural compounds derived from alkaloids, flavonoids, terpene, and polyphenols as promising TNF-α inhibitors will be discussed. Finally, we applied a molecular modeling protocol involving all compounds described here, suggesting that their interactions with Tyr59, Tyr119, Tyr151, Leu57, and Gly121 residues are essential for the activity. Such findings can be useful for research groups worldwide to design new anti-inflammatory TNF-α inhibitors.

Computer-Aided Drug Design of Anti-inflammatory Agents Targeting Microsomal Prostaglandin E2 Synthase-1 (mPGES-1).

Inflammation is a natural reaction to external stimuli to protect the organism. However, if it is exaggerated, it can cause severe physiopathological damage, linked to diseases like rheumatoid arthritis, cancer, diabetes, allergies, and infections. Inflammation is mainly characterized by pain, increased temperature, flushing, and edema, which can be controlled using anti-inflammatory drugs. In this context, prostaglandin E2 (PGE2) inhibition has been targeted for designing new compounds with anti-inflammatory properties. It is a bioactive lipid overproduced during an inflammatory process, in which its increased production is carried out mainly by COX-1, COX-2, and microsomal prostaglandin E2 synthase-1 (mPGES-1). Recently, studies have demonstrated that mPGES-1 inhibition is a safe strategy for developing anti-inflammatory agents, which could protect against pain, acute inflammation, arthritis, autoimmune diseases, and different types of cancers. Thus, in recent years, computer-aided drug design (CADD) approaches have been increasingly used to design new inhibitors, decreasing costs and increasing the probability of discovering active substances. Finally, this review will cover all aspects involving high-throughput virtual screening, molecular docking, dynamics, fragment-based drug design, and quantitative structure-activity relationship in seeking new promising mPGES-1 inhibitors.