L-Threonine,_N-[[[_1S_-3-amino-1-[3-[_1R_-1-amino-2-hydroxyethyl]-1,2

Protein serine/threonine kinases (PSKs) are protein kinases that use ATP as a high-energy donor molecule to transfer phosphate groups to serine/threonine residues of target protein. As an important signal transduction regulator, serine/threonine kinases can affect the function of target proteins by disrupting enzyme activity or binding of target proteins to other proteins. Serine/threonine kinases are involved in the regulation of immune response, cell proliferation, differentiation, apoptosis and other physiological processes. Serine/threonine kinase inhibitors are an important class of compounds that have been widely studied in cancer, chronic inflammation, autoimmune diseases, aging and other diseases.

MCE designs a unique collection of 2,186 serine/threonine kinase inhibitors, mainly targeting the receptor PKA, Akt, PKC, MAPK/ERK, etc, which is an effective tool for development and research of anti-cancer, anti-chronic inflammatory diseases, anti-autoimmune diseases and anti-aging compounds.

In the research of covalent inhibitors targeting serine and threonine, scientists have found that the nucleophilicity of these hydroxyl groups is significantly enhanced due to the influence of their surrounding environment. This results in higher activity during catalytic reactions. Aspirin, which targets the non-catalytic domain serine (Ser529 in human COX1) of cyclooxygenase, exerts its anti-inflammatory effect through covalent binding. β-lactam antibiotics, which targets the catalytic domain serine of penicillin-binding proteins, interferes with bacterial cell wall synthesis.

Through careful selection, we constructed a structural filter containing over 110 electrophilic groups. By analyzing the electrophilic fragments selected by the structural filter, we removed any molecules with trivial or undesirable structural features. Ultimately, we obtained 3,300 fragment molecules which can target serine and threonine residues and can be used for fragment-based covalent drug discovery.

Amino acids are indispensable building blocks for life activities and are widely involved in key biological processes such as cell signal transduction, energy metabolism, gene expression regulation, and neurotransmitter synthesis. As components of proteins, 20 kinds of amino acids make up over one million kinds of proteins in the human body. These amino acids can be classified into nine types of "essential amino acids" that the human body cannot synthesize on its own and must obtain from food, as well as eleven types of "non-essential amino acids" that the human body can synthesize on its own.

MCE offers 20 kinds of amino acids provided which can be applied in research fields such as the study of amino acid metabolic processes, metabolite identification, food/cosmetic ingredient research, and the development of nutritional supplements.

Amino acids are the fundamental components that sustain life activities, playing roles in ATP generation, promoting nucleotide synthesis, and maintaining cellular redox balance. Moreover, dysregulation of amino acid consumption is a significant potential regulatory mechanism leading to impaired anti-tumor immunity in immune cells. The normal functioning of immune cells relies on amino acid metabolic pathways to obtain energy and materials, and upon activation, they reprogram their metabolism to support growth, proliferation, and effector functions. Additionally, metabolic disorders of specific amino acids (such as branched-chain amino acids, glutamine, and arginine) can exacerbate mitochondrial dysfunction and oxidative stress, thereby promoting myocardial fibrosis and cardiac cell damage. Therefore, conducting research related to amino acid metabolism holds promise for discovering potential drugs for diseases related to cancer, immunity, and metabolism.

MCE can provide 200 kinds of metabolites of amino acid metabolic pathways, which can be used for drug screening in various diseases such as cancer, immune disorders, metabolic diseases, mitochondrial-targeted diseases

Unnatural amino acids (UAAs), also referred to as non-canonical amino acids (ncAAs) or non-proteinogenic amino acids, are a class of amino acids that are distinct from the 20 standard natural amino acids. They can be obtained through chemical synthesis, biosynthesis, and other approaches, with structural diversity far exceeding that of natural amino acids. UAAs are mainly including naturally occurring non-canonical amino acids, chemically synthesized amino acids, and biosynthetic amino acids, which provide a molecular basis for protein function design.

UAAs exhibit significant value in multiple fields. They can optimize the pharmacokinetic properties of peptide drugs and peptidomimetics, modify enzyme functions and endow them with new biological activities, thereby overcoming the limitations of traditional peptide drugs and expanding the chemical space . Meanwhile, UAAs can serve as molecular probes to analyze protein-protein interactions and investigate the regulatory mechanisms of protein functions.

MCE has compiled a UAAs Fragment Library comprising nearly a thousand unnatural amino acid fragments with extensive coverage of chemical space and enhanced structural diversity. This compound library can be widely applied in peptide synthesis, drug design, and protein engineering.

Amino acids, as one of the most fundamental organic compounds in living organisms, serve not only as the basic building blocks of proteins but also but also undertake the functions of energy supply, neurotransmitter synthesis, and maintenance of internal environment stability.Amino acid metabolic enzymes are a class of enzymes involved in the metabolic processes of amino acids, catalyzing their synthesis, breakdown, transformation, and interactions with other metabolic pathways. Abnormalities in amino acid metabolic enzymes can lead to various metabolic diseases, such as phenylketonuria and hyperammonemia, etc. Therefore, actively exploring and regulating the processes of amino acid metabolism is crucial for the development of drugs related to these diseases.

MCE designs a unique collection of 338 small molecules target amino acid metabolizing enzymes, which is an important tool for studying studying amino acid metabolism processes or metabolism-related drug development.

Unlike the 20 natural amino acids commonly found within living organisms, non-natural amino acids are synthesized through chemical or biosynthetic methods, thereby being endowed with unique chemical properties or biological activities. In drug development, these amino acids can be utilized to design novel pharmaceutical molecules that may exhibit superior pharmacological characteristics, such as increased selectivity, improved pharmacokinetic profiles, or reduced toxicity. In biomedical research, uon-natural amino acids can act as biological markers or probes for investigating biological processes like cell signaling, protein conformation, and protein-protein interactions. In addition, non-natural amino acids can also be used in the field of agriculture to develop new pesticides, plant growth regulators and so on.

Protein phosphorylation is a key post-translational modification underlying the regulation of many cellular processes. Phosphatases and kinases contribute to the regulation of protein phosphorylation homeostasis in the cell. This reversible regulation of protein phosphorylation is critical for the proper control of a wide range of cellular activities, including cell cycle, proliferation and differentiation, metabolism, cell-cell interactions, etc.

Protein phosphatases have evolved in separate families that are structurally and mechanistically distinct. Based on substrate specificity and functional diversity, protein phosphatases are classified into two superfamilies: Protein serine/threonine phosphatases and Protein tyrosine phosphatases. Ser/Thr phosphatases are metalloenzymes belonging to two major gene families termed PPP (phosphoprotein phosphatase) and PPM (metal-dependent protein phosphatases), whereas protein tyrosine phosphatases (PTPs) belong to distinct classes of enzymes that utilize a phospho-cysteine enzyme intermediate as a part of their catalytic action.

MCE supplies a unique collection of 177 phosphatase inhibitors that mainly targeting protein tyrosine phosphatases (PTPs) and serine/threonine-specific protein phosphatases. MCE Phosphatase Inhibitor Library is a useful tool for phosphatase drug discovery and related research.

Peptides are a group of biologically active substances that are involved in various cellular functions of organisms. Peptides are often used in functional analysis, vaccine research and especially in the field of drug research and development. At present, more than 80 peptide drugs have reached the market for a wide range of diseases, including diabetes, cancer, osteoporosis, multiple sclerosis, HIV infection and chronic pain.

MedChemExpress (MCE) offers a comprehensive collection of 2,537 peptides, including bioactive peptides, amino acid derivatives, and blocking peptides. MCE Peptide Library can be used for peptide library screening, peptide drug discovery, vaccine development, target verification, structural activity research, etc.

A histone modification, a covalent post-translational modification (PTM) to histone proteins, includes methylation, phosphorylation, acetylation, ubiquitylation, and sumoylation, etc. In general, histone modifications are catalyzed by specific enzymes that act predominantly at the histone N-terminal tails involving amino acids such as lysine or arginine, as well as serine, threonine, tyrosine, etc. The PTMs made to histones can impact gene expression by altering chromatin structure or recruiting histone modifiers. Histone modifications act in diverse biological processes such as transcriptional activation/inactivation, chromosome packaging, and DNA damage/repair. Deregulation of histone modification contributes to many diseases, including cancer and autoimmune diseases.

MCE owns a unique collection of 919 bioactive compounds targeting Epigenetic Reader Domain, HDAC, Histone Acetyltransferase, Histone Demethylase, Histone Methyltransferase, Sirtuin, etc. Histone Modification Research Compound Library is a useful tool for histone modification research and drug screening.

Metabolism is the set of life-sustaining chemical reactions in organisms that maintain cell homeostasis. Metabolic pathways are enzyme-mediated biochemical reactions that lead to biosynthesis (anabolism) or breakdown (catabolism) of molecules including glucose metabolism, lipid metabolism and amino acid or protein metabolism within a cell or tissue. As catalysts, enzymes are crucial to metabolism as they allow a reaction to proceed more rapidly and tregulate the rate of a metabolic reaction. Due to the importance of metabolic balance in the organism, the abnormal function of metabolic enzymes often leads to the occurrence of a variety of metabolic diseases, such as diabetes, obesity, cardiovascular disease, etc.

MCE designs a unique collection of 4,232 metabolic enzymes related small molecules, which is an important tool for studying the metabolic activities of organisms and developing drugs for metabolic diseases.

Mutations in oncogenes and tumor suppressor genes can modify multiple signaling pathways and in turn cell metabolism, which facilitates tumorigenesis. The paramount hallmark of tumor metabolism is “aerobic glycolysis” or the Warburg effect, coined by Otto Warburg in 1926, in which cancer cells produce most of energy from glycolysis pathway regardless of whether in aerobic or anaerobic condition. Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside. The increased uptake of glucose is facilitated by the overexpression of several isoforms of membrane glucose transporters (GLUTs). Likewise, the metabolic pathways of glutamine, amino acid and fat metabolism are also altered. Recent trends in anti-cancer drug discovery suggests that targeting the altered metabolic pathways of cancer cells result in energy crisis inside the cancer cells and can selectively inhibit cancer cell proliferation by delaying or suppressing tumor growth.

MCE provides a unique collection of 3,626 compounds which cover various tumor metabolism-related signaling pathways. These compounds can be used for anti-cancer metabolism targets identification, validation as well anti-cancer drug discovery.

Boronic acid and boronic ester represent a relatively novel and promising chemical structure in drug design. Boronic acid exists in an sp²-hybridized state, possessing an empty p-orbital that can act as a Lewis acid to accept lone pairs from heteroatoms (O, N, or S). This Lewis acidity enables it to form reversible covalent bonds with amino acid residues such as lysine, serine, threonine, and histidine. Currently, five FDA-approved drugs containing boronic acid or boronic ester predominantly involve such covalent binding mechanisms in their interactions with target proteins. Furthermore, boronic acid can serve as a bioisostere for carboxylic acids, phosphates, and phenolic groups, utilized to improve pharmacokinetic properties and enhance drug efficacy.

To date, five boron-containing drugs have been approved by the FDA. The unique properties of boronic acids and boronic esters confer significant potential in drug design, with applications spanning cancer therapy (e.g., multiple myeloma), anti-infectives (e.g., fungal infections, tuberculosis), anti-inflammatory treatments (e.g., atopic dermatitis), antibacterial agents (e.g., carbapenem-resistant bacterial infections), and Reactive Oxygen Species (ROS)-responsive prodrugs, among others. The MCE Boronic Acid/Boronic Ester Fragment Library, which contains 1,488 compounds, serves as a valuable tool for the development of boron-containing drugs.

A unique set of molecules containing mild electrophilic moieties that covalently interact with amino acid residues in the target protein. The diversity of our compounds for covalent drug discovery ranges from natural product-like scaffolds to macrocycles, creating multiple opportunities in hit generation for a selected target.

The most prominent mechanism of action of kinase inhibitors is their competition with ATP by binding to the hinge region of the kinase protein. Once the kinase is blocked by an inhibitor, it loses the ability to transfer phosphate groups from ATP to other molecules, resulting in the loss of kinase activity.

The hinge-binding region of kinase inhibitors mimics the interaction pattern between the ATP nucleobase and the kinase. MCE extracted thousands of kinase inhibitors from the ChEMBL database and isolated their molecular fragments. In certain cases, the amino and amide groups on the molecular fragments are crucial for binding in the hinge region. Therefore, we enhanced the diversity of the collected results by adding these two groups to unoccupied positions on the ring system. Subsequently, the fragments were assessed for their hinge region binding ability via docking at distinct kinases, we also applied pharmacophore constraints to ensure interactions with key amino acids in the kinase hinge region, ultimately obtaining kinase-related molecular fragments.

MCE provides over 12,410 kinase fragment molecules that meet the above requirements and are available off the shelf, serving as an effective tool for screening and developing drugs targeting kinases.

The transforming growth factor beta (TGF-β) signaling pathway is involved in many cellular processes in both the adult organism and the developing embryo including cell growth, cell differentiation, apoptosis, cellular homeostasis and other cellular functions. The TGF-β superfamily comprises TGF-βs, bone morphogenetic proteins (BMPs), activins and related proteins. Signaling begins with the binding of a TGF beta superfamily ligand to a TGF beta type II receptor. The type II receptor is a serine/threonine receptor kinase, which catalyzes the phosphorylation of the Type I receptor. The type I receptor then phosphorylates receptor-regulated SMADs (R-SMADs) which can now bind the coSMAD (e.g. SMAD4). R-SMAD/coSMAD complexes accumulate in the nucleus where they act as transcription factors and participate in the regulation of target gene expression. Deregulation of TGF-β signaling contributes to developmental defects and human diseases, including cancers, some bone diseases, chronic kidney disease, etc.

MCE designs a unique collection of 428 TGF-beta/Smad signaling pathway compounds. TGF-beta/Smad Compound Library acts as a useful tool for TGF-beta/Smad-related drug screening and disease research.

Cyclic peptide library have advantages such as high affinity, high selectivity, and suitability for targeting protein–protein interactions. Through DEL synthesis technology, the library size can achieve hundreds of millions. DEL cyclic peptide library have advantages like low cost andhigh screeing efficiency, making them valuable for discovering lead compounds against challenging drug targets.

This cyclic peptide library is constructed with unnatural amino acids as building block, synthesized through DNA-compatible chemical reactions. Each cyclic peptide consist of six amino acids and constrained conformations such as side-chain cross-linking, disulfide bonds, and macrocyclization. These cyclic peptides exhibit significantly improved stability and druggability compared with linear peptides, filling the gap between small molecules and macromolecular biologics. Each cyclic peptide is uniquely conjugated to a DNA barcode sequence for molecular identification and sequencing decoding.

MCE’s cyclic peptide library has8 independent sub-libraries, with a total molecular diversity of 1.2 billion. It is constructed via multi-round combinatorial assembly of building blocks and diverse cyclization strategies, facilitating the discovery of cyclic peptide leads for undruggable targets.

Post-translational modifications (PTMs) refer to chemical modifications that occur on amino acid residues of proteins after translation, involving the addition or removal of specific functional groups. These modifications regulate protein activity, localization, folding, and interactions with other biomolecules. By influencing protein function, PTMs play a crucial role in various pathophysiological processes. Common types of PTMs include protein phosphorylation, methylation, acetylation, ubiquitination, glycosylation, and more.

MCE offers 3,704 PTM-targeting compounds, which can be used for drug screening in cancer, neurodegenerative diseases, metabolic disorders, etc.

Neurotransmitters are chemical messengers that allows a neuron's electrical signal to pass to a postsynaptic neuron or effect target. Neurotransmitters include amino acids, monoamines, and peptides, while other neurotransmitters are composed of metabolites such as nitric oxide and carbon monoxide. The function of neurotransmitters is closely related to the disease of life, helping to regulate the body's heartbeat, blood pressure, breathing, sleep, aging and muscle activity. Therefore, research based on neurotransmitters can help to increase human understanding of diseases.

MCE collects and organizes 58 neurotransmitters and is a tool library for drug screening and mechanism research.

Glutamine is an important metabolic fuel that helps rapidly proliferating cells meet the increased demand for ATP, biosynthetic precursors, and reducing agents. Glutamine Metabolism pathway involves the initial deamination of glutamine by glutaminase(GLS), yielding glutamate and ammonia. Glutamate is converted to the TCA cycle intermediate α-ketoglutarate (α-KG) by either glutamate dehydrogenase (GDH) or by the alanine or aspartate transaminases (TAs), to produce both ATP and anabolic carbons for the synthesis of amino acids, nucleotides and lipids. During periods of hypoxia or mitochondrial dysfunction, α-KG can be converted to citrate in a reductive carboxylation reaction catalyzed by IDH2. The newly formed citrate exits the mitochondria where it is used to synthesize fatty acids and amino acids and produce the reducing agent, NADPH.

Cancer cells display an altered metabolic circuitry that is directly regulated by oncogenic mutations and loss of tumor suppressors. Mounting evidence indicates that altered glutamine metabolism in cancer cells has critical roles in supporting macromolecule biosynthesis, regulating signaling pathways, and maintaining redox homeostasis, all of which contribute to cancer cell proliferation and survival. Thus, intervention in glutamine metabolic processes could provide novel approaches to improve cancer treatment.

MCE owns a unique collection of 1,730 compounds targeting the mainly proteins and enzymes involved in glutamine metabolism pathway. Glutamine Metabolism compound library is a useful tool for intervention in glutamine metabolic processes.

Dipeptide compounds have attracted extensive attention in drug discovery and life science research due to their simple structures, ease of modification, and favorable biocompatibility. As small peptides composed of two amino acids, dipeptides exhibit diverse biological activities, including anti-inflammatory, antioxidant, antimicrobial, anticancer, and immunomodulatory effects, showing significant application potential in metabolic disorders, neurological diseases, and cancer research. Compared with traditional small molecules, dipeptide compounds possess favorable target-binding properties and high structural plasticity, making them valuable tools for drug screening and mechanism studies.

The MCE Dipeptide Compound Library contains 80 dipeptide compounds and can be applied to peptide drug discovery and development.

DEL technology enables the simultaneous screening of millions or billions of compounds in a single tube by covalently linking each small molecule with a unique DNA sequence. Traditional DEL screening primarily focuses on identifying non-covalent binding molecules, where interactions with the target are reversible. In contrast, DNA‑encoded covalent library is an ultra‑high‑throughput screening library developed on the basis of conventional DNA‑encoded library technology. It incorporates controllable electrophilic covalent warheads capable of forming irreversible covalent bonds with amino acid residues at the active sites of target proteins, including Cys, Lys, Ser, Tyr, and others. This covalent binding enhances binding affinity, prolongs residence time at the target site, and has the potential to overcome challenges associated with traditional non-covalent inhibitors, such as drug resistance or off-target effects.

Each compound in the library contains both a binding domain and an electrophilic warhead. It first recognizes and binds to the target through non covalent interactions, and then forms a stable covalent bond with key amino acid residues to achieve irreversible inhibition. This library is specifically designed for the discovery of potent, long lasting, and highly selective covalent inhibitors, particularly for undruggable targets such as kinases, GPCRs, proteases, and mutant oncoproteins. Each molecule is uniquely labeled with a DNA barcode for molecular identification and sequencing decoding.

This library is an advanced and highly diverse collection, consists of 35 independent sub-libraries with a total scaleof 14 million compounds, It incorporates over 14 experimentally validated covalent warheads capable of targeting cysteine, lysine, arginine, aspartic acid and glutamic acid. This library is constructed with diverse drug like core scaffolds and integrated controllable covalent warheads, it features structural diversity, reaction spec

A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. Proteases play important roles in regulating multiple biological processes in all living organisms, such as regulating the fate, localization, and activity of many proteins, modulating protein-protein interactions, creating new bioactive molecules, contributing to the processing of cellular information, and generating, transducing, and amplifying molecular signals.

Proteases are important targets in drug discovery. Some protease inhibitors are often used as anti-virus drugs and anti-cancer drugs. MCE offers a unique collection of 932 protease inhibitors. MCE Protease Inhibitor Library is critical for drug discovery and development.

Covalent inhibitors are small molecules that can bind specifically to target proteins through covalent bonds and inhibit their biological functions. Although for a long time, covalent targeting has been playing a subordinate role in drug discovery, with an increasing number of reports on successful clinical applications of such drugs, the potential of these agents is now being acknowledged.

Covalent ligands rely on reactive groups (“warheads”), and new warheads are key to expanding the scope of covalent modalities. Through careful selection, we constructed a structural filter containing over 110 electrophilic groups. By analyzing the electrophilic fragments selected by the structural filter, we removed any molecules with trivial or undesirable structural features. Ultimately, we obtained 8,900 fragment molecules with covalent modification potential, which can target various reactive amino acid residues and can be used for fragment-based covalent drug discovery.

Exosomes are small membrane vesicles of endocytic origin that are secreted by most cells in culture. Exosomes contain nucleic acids, proteins, lipids, amino acids, and metabolites, etc. Their diverse constituents can reflect their cell of origin. Exosomes are associated with immune responses, viral pathogenicity, pregnancy, cardiovascular diseases, central nervous system-related diseases, and cancer progression. Proteins, metabolites, and nucleic acids delivered by exosomes into recipient cells effectively alter their biological response. Such exosome-mediated responses can be disease promoting or restraining.

The biology of exosomes in disease is still emerging, and the number of studies addressing their utility in the diagnosis and treatment of various pathologies has increased substantially. MCE supplies a unique collection of 53 compounds with the activity of inhibiting or stimulating exsomes secretion/biosynthesis. MCE Exosomes Compound Library is a useful tool for exsomes research.

Human metabolism is an integral part of cellular function that reflects individual differences in health, disease, diet, and lifestyle. Many health conditions such as obesity, diabetes, hypertension, heart disease, and cancer are associated with abnormal metabolic states. In the pathological state of the human body, metabolic pathways are significantly altered, resulting in aberrant levels of intermediates or end-products that can be viewed as potential diagnostic biomarkers or even therapeutic targets. Therefore, detection, identification and quantification of human metabolites are very important for drug metabolism research in drug development.

MCE offers a unique collection of 6,744 human metabolites, including endogenous metabolites and exogenous metabolites, covering multiple structure types, such as lipids, amino acids, nucleic acids, carbohydrates, organic acids, biogenic amines, vitamins,. MCE Human Metabolites Library is a helpful tool for studying the relationship between diseases and metabolism.

Dietary supplement, also known as nutritional supplement or food supplement, include dietary components such as vitamins, minerals, and amino acids. The unique value of dietary supplement is particularly significant in the post-pandemic era. Compared to traditional medication, dietary supplement is often more readily accepted by the public due to their higher safety profile and the natural origin. By orally supplementing essential nutrients and bioactive substances, dietary supplement can help to enhance the body's health level and reduce the risk of diseases. For certain chronic conditions, proper dietary supplement can also serve as a powerful adjunct to conventional medical treatment, enhancing the effectiveness of medication.

Covalent inhibitors are small molecules that can bind specifically to target proteins through covalent bonds and inhibit their biological functions. Although for a long time, covalent targeting has been playing a subordinate role in drug discovery, with an increasing number of reports on successful clinical applications of such drugs, the potential of these agents is now being acknowledged. Currently, cysteine is the most common covalent amino acid residue in a variety of covalent drugs, and various warheads have been developed that can react with cysteine, providing the key building blocks for covalent drugs to form covalent bonds.

To meet the development needs of covalent inhibitors targeting cysteine, MCE has designed a unique collection of 5,137 compounds with different covalent warheads that target cysteine. The MCE Cysteine Targeted Covalent Library is designed using the following covalent warheads: Acrylamides, Propiolic acid ester, Dimethylamine functionalized acrylamides, Chloroacetamides, Acrylonitrile, 2-Cyanoacrylamide, Aziridine, Haloacetamide, etc.

Heterocyclic compounds are cyclic organic compounds which contain at least one hetero atom, the most common heteroatoms are nitrogen, oxygen ,and sulfur. Heterocycles are common in biology, featuring a wide range of structures from enzyme co-factors to amino acids and proteins. On the one hand, heterocycles are common structural units in approved drugs and in medicinal chemistry targets in the drug discovery process. In addition, heterocycles have been found as a key structure in medical chemistry and also they are frequently found in large percent of biomolecules such as vitamins, natural products ,and biologically active compounds including antifungal, anti-inflammatory, antibacterial, antioxidant, antiallergic, anti-HIV, antidiabetic, anticancer activity.

MCE offers a unique collection of 6,508 heterocyclic compounds which can be used for drug discovery for high throughput screening (HTS) and high content screening (HCS). MCE heterocyclic compound library is critical for drug discovery and development.

Covalent inhibitors are small molecules that can bind specifically to target proteins through covalent bonds and inhibit their biological functions. Although for a long time, covalent targeting has been playing a subordinate role in drug discovery, with an increasing number of reports on successful clinical applications of such drugs, the potential of these agents is now being acknowledged. Currently, cysteine is the most common covalent amino acid residue in a variety of covalent drugs, and various warheads have been developed that can react with cysteine, providing the key building blocks for covalent drugs to form covalent bonds.

To meet the development needs of covalent inhibitors targeting cysteine, MCE has designed a unique collection of 3,622 fragments with different covalent warheads that target cysteine. The MCE Cysteine Targeted Covalent Fragment Library is designed using the following covalent warheads: Acrylamides, Propiolic acid ester, Dimethylamine functionalized acrylamides, Chloroacetamides, Acrylonitrile, 2-Cyanoacrylamide, Aziridine, Haloacetamide, etc. All fragments are pre-filtered with the Rule of Three restrictions which can be used for fragment-based covalent drug development.

Peptides, composed of amino acids, serve as crucial building blocks for proteins and have gained significant attention in drug development over the past decade. The advancements in production, modification, and analytical technologies have led to a surge in the potential applications of peptides in medicine. Peptides offer a number of advantages over small molecule drugs, including: greater target specificity and efficacy, more predictable metabolic profiles, easier delivery to where they are needed in the body, and fewer side effects. Peptides are increasingly appearing in all branches of medicine as components of innovative drugs, imaging agents, diagnostic agents, and other complex drugs such as peptide-drug conjugates. To date, more than 80 peptide drugs have been approved to treat a variety of diseases, including microbial infections, obesity, anti-diabetes, and cancer, as well as to develop cell targeting platforms and improve cell penetration properties.

MCE designs a unique collection of 832 peptide compounds. HY-L105S is a peptide compound library that can be provided with solution form based on HY-L105, and can be applied to peptides-based drug development.

Bile acids are a class of amphiphilic molecules derived from the metabolic breakdown of cholesterol, primarily synthesized in the liver, and play a crucial role in the intestines. Based on their structural characteristics, bile acids are mainly divided into two categories: free bile acids (including Cholic acid, Deoxycholic acid, Chenodeoxycholic acid) and conjugated bile acids (including Glycocholic acid, Glycochenodeoxycholic acid, Taurocholic acid, etc.). Bile acids play a significant role in the pathophysiological research of liver and gastrointestinal diseases and are closely associated with the occurrence of metabolic diseases such as obesity, type II diabetes, non-alcoholic fatty liver disease, and atherosclerosis. Bile acids maintain metabolic balance within the body by regulating sugar metabolism, lipid metabolism, and amino acid metabolism, and they influence the activity of metabolism-related enzymes and transporters. In addition, Bile acids can also be used to construct a bile acid metabolism research platform, which helps to delve into the metabolic pathways and dynamic changes of bile acids in living organisms and aids in identifying new biomarkers for certain diseases.

MCE included 61 bile acids, including Cholic acid, Deoxycholic acid, Glycocholic acid, etc., which are effective tools for the study of liver and gallbladder diseases.

Small molecule covalent inhibitors, or irreversible inhibitors, are a type of inhibitors that exert their biological functions by irreversibly binding to target through covalent bonds. Compared with non-covalent inhibitors, covalent inhibitors have obvious advantages in bioactivity, such that covalent warheads can target rare residues of a particular target protein, thus leading to the development of highly selective inhibitors and achieving a more complete and continued target occupancy in living systems. In recent years, the distinct strengths of covalent inhibitors in overcoming drug resistance had been recognized. However, toxicity can be a real challenge related to this class of therapeutics due to their potential for off-target reactivity and has led to these drugs being disfavored as a drug class. The drug design and optimization of covalent inhibitors has become a hot spot in drug discovery.

MCE Lead-like Covalent Screening Library offers a valuable resource of 1,049 lead-like compounds with commonly used covalent warheads. These warheads, such as acrylamide, activated terminal alkyne, acyloxymethyl ketone, and boronic acid, are capable of reacting with specific amino acid residues, including cysteine, lysine, serine, and histidine. The inclusion of these reactive warheads in the library allows researchers to explore the potential of covalent inhibition, a powerful approach in drug discovery.

G protein-coupled receptors (GPCRs) are membrane proteins in humans and one of the most important targets in drug discovery. Approximately 35% of launched drugs are targeted GPCRs, making them a crucial class of targets in drug discovery.

The orthosteric site of a GPCR is its endogenous ligand’s (such as neurotransmitters or hormones) binding site. This site plays a central role in signal transduction. Small molecules binding to this site typically contain a protonatable amino group, enabling the formation of salt bridges or hydrogen bonds with acidic residues in the binding pocket. In contrast, the allosteric site does not directly initiate signaling but modulates the signal intensity of the GPCR by altering or stabilizing the conformation of the orthosteric site. Small molecules binding to the allosteric site often contain multiple aromatic rings to occupy hydrophobic pockets and achieve their functional effects.

MCE has collected over 7,116 reported bioactive molecules targeting GPCRs, covering Class A, B, and C GPCRs. These small molecules were subjected to AI representation to extract 2D and 3D features. Subsequently, we do screening by AI score based on similarity to identify molecules in diversity library highly similar to the reported bioactive molecules in both 2D and 3D, with a threshold greater than 0.7. Further screening based on cLogP was applied to select molecules with good lipophilicity, which facilitates the binding of small molecules to GPCRs. This diversity library can be widely applied to the discovery of compounds targeting GPCR proteins.

Recently, significant advancements in tyrosine-targeting electrophiles have primarily occurred in the field of protein-protein interactions (PPIs), where cysteine residues are often underrepresented and novel chemistries are needed to address these interfaces. In this context, tyrosines are frequently more accessible compared to more buried binding sites. Moreover, they are commonly found at "hot spots," which are functional epitopes of PPIs, with 12.3% of the residues consisting of tyrosines. This prevalence is likely due to the hydrophobic nature of tyrosine, its ability to participate in aromatic π-interactions, and its capacity for hydrogen bonding. Beyond PPIs, some progress has also been made in covalent tyrosine targeting in other areas where more commonly addressed side chains are lacking. Even though tyrosine has a slightly lower pKa value compared to the protonated lysine side chain (approximately 10 vs. 10.5 for the unprotected amino acid side chains), significantly less progress has been made in the development of tyrosine-targeted covalent ligands compared to lysine. This is likely due to the reduced flexibility of the tyrosine side chain and the greater steric hindrance of its hydroxy group, which makes it more challenging to adopt suitable reaction geometries.

Through careful selection, we constructed a structural filter containing over 110 electrophilic groups. By analyzing the electrophilic fragments selected by the structural filter, we removed any molecules with trivial or undesirable structural features. Ultimately, we obtained 124 fragment molecules which can target tyrosine residue and can be used for fragment-based covalent drug discovery.

Phosphatase Inhibitor Cocktail Ⅲ (100× in DMSO) is a mixture of multiple phosphatase inhibitors that effectively inhibit serine/threonine phosphatases and alkaline phosphatases, and is used to preserve the phosphorylation status of proteins.The 1 mL volume is defined as the base specification. All larger sizes correspond to incremental volumes of this base.

Phosphatase Inhibitor Cocktail I (100× in DMSO) is a blend of 2 phosphatase inhibitors that can effectively inhibit alkaline phosphatases and serine/threonine phosphatases. It is used to maintain the phosphorylation status of proteins.The 1 mL volume is defined as the base specification. All larger sizes correspond to incremental volumes of this base.

O-Glycosidase is highly specific and can release Galβ1-3GalNAc from serine, threonine residues or as part of a glycopeptide or glycoprotein. Applied to glycoprotein biosynthesis analysis, O-glycan bioactive protein O-glycosylation detection and binding site analysis.

L-glutamine is an important amino acid supplement commonly added to mammalian cell culture media. L-glutamine serves as an auxiliary energy source, especially when cells are rapidly dividing. L-glutamine is also important in the production of purine and pyrimidine nucleotides, amino sugars, glutathione, L-glutamate, other amino acids, and plays a role in protein synthesis and glucose production.

MEM Non-essential Amino Acid Solution (100×) has been filtered and can be used directly. It adds nutrients and reduces the biosynthetic burden on cell in vitro. The 100 mL is defined as the base specification. All larger sizes correspond to incremental volumes of this base.

MCE Amino magnetic beads (200 nm，10 mg/mL) can easily and efficiently combine with a variety of biological ligand in high loads, such as proteins, peptides, oligonucleotides, drug molecules, etc. It can be used as a good basic material for subsequent processing, adsorption, chemical modification and other follow-up processing.

Minimum Essential Medium (MEM), also known as Minimal Essential Medium, was developed by Harry Eagle based on Eagle’s Basal Medium (BME). It is a basic cell culture medium with a simple formulation and broad applicability, and is one of the most commonly used media in animal cell culture. MEM contains only 12 essential amino acids, L-glutamine, and 8 vitamins. It is primarily used for the culture of adherent cells. With appropriate formulation modifications, it can also be used for other types of cell culture.