interactions

Macrocycles, molecules containing 12-membered or larger rings, are receiving increased attention in small-molecule drug discovery. The reasons are several, including providing access to novel chemical space, challenging new protein targets, showing favorable ADME- and PK-properties. Macrocycles have demonstrated repeated success when addressing targets that have proved to be highly challenging for standard small-molecule drug discovery, especially in modulating macromolecular processes such as protein–protein interactions (PPI). Otherwise, the size and complexity of macrocyclic compounds make possible to ensure numerous and spatially distributed binding interactions, thereby increasing both binding affinity and selectivity.

MCE offers a unique collection of 447 macrocyclic compounds which can be used for drug discovery for high throughput screening (HTS) and high content screening (HCS). MCE Macrocyclic Compound Library is a useful tool for discovering new drugs, especially for “undruggable” targets and protein–protein interactions.

Peptidomimetics are compounds whose essential elements (pharmacophore) mimic a natural peptide or protein in 3D space and which retain the ability to interact with the biological target and produce the same biological effect. Peptidomimetics are designed to circumvent some of the problems associated with a natural peptide: e.g. stability against proteolysis (duration of activity) and poor bioavailability. Certain other properties, such as receptor selectivity or potency, often can be substantially improved. The design and synthesis of peptidomimetics are most important because of the dominant position peptide and protein-protein interactions play in molecular recognition and signaling, especially in living systems. Hence mimics have great potential in drug discovery.

MCE Peptidomimetic Library contains 370 compounds including peptoid, α-helix mimetics, β-turn/sheets mimetics, etc. This library is an indispensable tool of structure-activity relationships in drug discovery.

Cysteine proteases (CPs), a key enzyme family regulating physiological metabolism and mediating pathological processes (e.g., abnormal bone resorption, tumour invasion, and pathogen infection), represent a core therapeutic target for disease intervention via the development of specific inhibitors. Currently reported CP covalent inhibitors encompass diverse structural types, including epoxides, aziridine, and activated double bonds (vinyl sulphones, α,β-unsaturated ketones), providing clear structural references for the development of novel CP covalent inhibitors.

This compound library contains multiple warheads that specifically target cysteine proteases, serving as a powerful tool for the efficient discovery of novel covalent inhibitors against this enzyme family.

Protein protein interactions (PPI) have pivotal roles in life processes. The studies showed that aberrant PPI are associated with various diseases. However, the design of modulators targeting PPI still faces tremendous challenges, such the difficult PPI interfaces for the drug design, lack of ligands reference, lack of guidance rules for the PPI modulators development and high-resolution PPI proteins structures.

The PPI Library comprises molecules of various sizes, frameworks, and shapes ranging from fragment-like entities to macrocyclic derivatives designed as secondary structure mimetics or as epitope mimetics. The designs cover β-turn / loop mimetics and α-helix mimetics. Since helices present at the interface in 62% of all protein-protein interactions. This library focused on designs including mimics with the substitution geometry of an a-helices, as well as designs that mimic the location of “hot-spot” side chains in helix-mediated PPIs.

POI (Protein of Interest) refers to the target protein, namely the disease-causing protein or key functional protein that undergoes degradation or functional modulation in molecular glue-mediated processes. The Molecular Glue POI Library consists of a series of fragments that can specifically bind to different types of POIs. As key components of molecular glues, these ligands form stable interactions with target proteins, laying the foundation for molecular glues to induce the interaction between POIs and E3 ubiquitin ligases. The covered POIs include various types such as cancer-associated GSPT1, androgen receptors, and abnormally aggregated proteins linked to neurodegenerative diseases.

This fragment library can be applied to the screening and optimization of targeted protein degraders. By screening ligands with high affinity and strong selectivity for specific POIs from the library, core structures can be identified to develop novel molecular glues. For instance, optimization of ligands targeting GSPT1 has yielded molecular glue degraders with enhanced degradation activity. Since many POIs are difficult to drug due to the lack of traditional small-molecule binding pockets, some ligands in the POI Ligand Library can modulate such POIs by inducing protein-protein interactions, thereby further expanding the scope of drug discovery for undruggable targets.

MCE has compiled a POI Fragment Library comprising thousands of POI fragments with molecular weights ranging from 150 to 400. This compound library can be widely applied in Molecular Glue research and development.

RNA is crucial for the regulation of numerous cellular processes and functions. With the in-depth study of disease mechanisms, processes such as RNA expression, splicing, translation, and stability regulation have become new targets for disease intervention. RNA has provided new therapeutic modalities for metabolic diseases, genetic disorders, and cancer patients, resulting in several innovative drugs.

MCE R&D team collected small molecules targeting RNA from the PDB, R-BIND, ROBIN, and internal database as the positive dataset, and non-targeting RNA small molecules from ROBIN as the negative dataset. Based on the GeminiMol pre-trained model, we encoded the molecules and calculated over 1700 molecular descriptors using Mordred as inputs for the model. Subsequently, we employed 13 deep learning models to learn from the data. All of which yielded good training results, with AUROCs greater than 0.75. Ultimately, we selected the Finetune model to screen HY-L901P, which exhibited the best classification performance, achieving an AUROC of 0.82 and a prediction accuracy of 0.76. We then applied filtering based on StaR rules (with at least two of the following properties: cLogP ≥ 1.5, Molar Refractivity ≥ 4, Relative Polar Surface Area ≤ 0.3) to obtain a library containing approximately 5,000 small molecule compounds targeting RNA. This library serves as a valuable tool for screening small molecules that interact with RNA.

Linkers play a necessary role in the physicochemical properties and biological activity of the bifunctional molecule. These linkers are not a simply connection of two functional modules together, but its design and nature directly affect the stability, activity, selectivity, pharmacokinetics, and ultimately the therapeutic efficacy of the entire molecule. The length of the linker determines the extent of interaction between the two ligands and thus the maximum activity of the PROTAC molecule.

MCE has collected 0 PROTAC Linkers can be used for the design and synthesis of bifunctional molecules.

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 12,417 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.

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 3,699 PTM-targeting compounds, which can be used for drug screening in cancer, neurodegenerative diseases, metabolic disorders, etc.

Protein protein interactions (PPI) have pivotal roles in life processes. The studies showed that aberrant PPI are associated with various diseases, including cancer, infectious diseases, and neurodegenerative diseases. The classic drug targets are usually enzymes, ion channels, or receptors, the PPI indicate new potential therapeutic targets. Therefore, targeting PPI is a new direction in treating diseases and an essential strategy for the development of new drugs.

However, the design of modulators targeting PPI still faces tremendous challenges, such the difficult PPI interfaces for the drug design, lack of ligands reference, lack of guidance rules for the PPI modulators development and high-resolution PPI proteins structures.

With the development of high-throughput technology, high-throughput screening is also gradually used for the identification of PPI inhibitors, but the compound library used for conventional target screening is not very effective in screening PPI inhibitors. To improve screening efficiency, MCE carefully selected 767 PPI inhibitors and mainly targeting MDM2-p53, Keap1-Nrf2, PD-1/PD-L1, Myc-Max, etc. MCE Protein-protein Interaction Inhibitor Library is a useful tool for PPI drug discovery and related research.

PROTACs (Proteolysis-targeting chimeras) is a class of molecules that utilize ubiquitin-proteasome system (UPS) to ubiquitinate and degrade target proteins. The PROTACs molecule consists of two ligands joined by a linker. The one-to-one interaction between PROTACs and target proteins determines the high efficiency of PROTACs, making it a potential molecule for targeted protein degradation (TPD) therapy.

MCE supplies a unique collection of 510 PROTACs that effectively degrade target proteins with more powerful screening capability. MCE PROTAC Library is a useful tool for signal pathway research, protein degradation therapy research, drug discovery and drug repurposing, etc.

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.

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

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 324 small molecules target amino acid metabolizing enzymes, which is an important tool for studying studying amino acid metabolism processes or metabolism-related drug development.

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 914 protease inhibitors. MCE Protease Inhibitor Library is critical for drug discovery and 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.

Cyclic peptides are polypeptide chains taking cyclic ring structure, which exhibit diverse biological activities, such as antibacterial activity, immunosuppressive activity and anti-tumor activity. Cyclic peptides, with the features of good binding affinity, target selectivity and low toxicity, show great success as therapeutics. Multiple cyclic peptides are currently in clinical use, for examples, gramicidin and tyrocidine with bactericidal activity, cyclosporin A with immunosuppressive activity, and vancomycin with antibacterial activity. Furthermore, cyclic peptides usually have the sufficient size and a balanced conformational flexibility/rigidity for binding to flat protein-protein interaction (PPI) interfaces, which have potential to develop PPI drugs.

MCE offers a unique collection of 96 cyclic peptides, all of which have good bioactivities. MCE Cyclic Peptide Library is a powerful tool for drug discovery and PPI inhibitor screening.

19F-NMR has proved to be a detection mode in fragment-based drug discovery (FBDD) for studies of protein structure and interactions. 19F shows high sensitivity for NMR detection, and the exquisite sensitivity of 19F chemical shifts and linewidths to ligand binding all make it a valuable approach in FBDD.F (Fluorine) -Fragments can be used for 19F-NMR detection after binding to target proteins, and can be used as an effective 19F-NMR tool for FBDD.

MCE designs a unique collection of 5,124 F-fragments, all of which obey a heuristic rule called the “Rule of Three (RO3)”, in which molecular weight ≤300 Da, the number of hydrogen bond donors (H-donors) ≤3, the number of hydrogen bond acceptors (H-acceptors) is ≤3 and cLogP is ≤3. This F-fragments library is an important source of lead-like drugs.

Targeted protein degradation(TPD) is a novel and promising approach to new drug discovery and development. It shows great potential for treating diseases with “undruggable” pathogenic protein targets and for overcoming drug resistance. Molecular glues and PROTACs are both targeted protein degraders that have attracted the most attention.

Molecular glues are small molecular degraders that mainly induce novel interaction between an E3 ligase and a target protein to form a ternary complex, leading to protein ubiquitination and subsequent proteasome degradation. Compared with PROTACs, molecular glues generally possess more favorable drug-like properties, such as lower MW, higher cell permeability, and better oral absorption. Molecular glues are emerging as a promising new therapeutic strategy.

MCE supplies a unique collection of 101 molecular glues which target various proteins. MCE Molecular Glue Compound Library is a useful tool to conduct scientific research and disease mechanism study.

Cysteine proteases (CPs), a key enzyme family regulating physiological metabolism and mediating pathological processes (such as abnormal bone resorption, tumour invasion, and pathogen infection), represent a core therapeutic target for developing specific inhibitors in disease intervention. Currently reported CP inhibitors primarily achieve their inhibitory function by precisely binding to CP active pockets (e.g., S1-S4 non-primed regions or S1'-S2' primed regions) and forming covalent/non-covalent interactions with the active site cysteine residues, providing clear structural references for the development of novel inhibitors.

This compound library, designed based on the core strategy of "similarity-based known active structures", contains over 200 cysteine protease inhibitors. Leveraging AI-driven molecular screening technology, it retains the critical pharmacological and shape features of reported CP inhibitors, serving as a specialized tool for efficiently discovering novel cysteine protease inhibitors.

Protein ubiquitination is an enzymatic post-translational modification in which an ubiquitin protein is attached to a substrate protein. Ubiquitination involves three main steps: activation, conjugation, and ligation, performed by ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), and ubiquitin ligases (E3s), respectively. Ubiquitination affects cellular processes such as apoptosis, cell cycle, DNA damage repair, and membrane transportation, etc. by regulating the degradation of proteins (via the proteasome and lysosome), altering the cellular localization of proteins, affecting proteins activity, and promoting or preventing protein-protein interactions. Deregulation of ubiquitin pathway leads to many diseases such as neurodegeneration, cancer, infection and immunity, etc.

MCE offers a unique collection of 467 small molecule modulators with biological activity used for ubiquitination research. Compounds in this library target the key enzymes in ubiquitin pathway. MCE Ubiquitination Compound Library is a useful tool for the research of ubiquitination regulation and the corresponding diseases.

Metabolomics, positioned as the systemic characterization of small-molecule metabolites within biological systems, has emerged as an indispensable analytical platform in both fundamental research and translational applications across plant sciences, microbial biotechnology, and biomedical investigations. Functioning as a critical component in multi-omics integration, this discipline deciphers the intricate molecular networks operating downstream of genomic, transcriptomic, and proteomic regulation, thereby capturing the dynamic biochemical phenotype closest to organismal functionality. The metabolome, comprising endogenous compounds with molecular weights typically below 1500 Da, serves as the functional readout of cellular processes and environmental interactions, where perturbations in metabolic networks are frequently implicated in disease pathogenesis. Such unique attributes have propelled metabolomics into a pivotal role in pharmacological research, particularly in target deconvolution, pharmacodynamic assessment, and mechanistic elucidation of pathological processes.

MCE can provide 5,872 mass spectrometry human metabolites that can be used for metabolite identification and quantification, functional cell detection and phenotypic screening of mass spectrometry.

Extracellular vesicles (EVs) are small membrane binding structures that are released from cells into the surrounding environment and play a crucial role in mediating and regulating intercellular communication related to physiological and pathological processes. EVs are lipid membrane vesicles composed of proteins, lipids, and nucleic acids. EVs can be divided into several types based on their source, such as extracellular vesicles, microcapsules, and apoptotic vesicles. The size range of exosomes is 30-150nm, which are endocrine in multi vesicular endosomes (MVEs); microvesicles (50-1000nm) are secreted directly through extracellular interactions, thereby releasing plasma membrane vesicles. In contrast, apoptotic bodies are usually larger, ranging in size from 1 to 5 μ m. This is generated during programmed cell death. EV plays a crucial role in transmitting information between cells and influencing the behavior and function of receptor cells.

MCE designs a unique collection of 634 small molecules related to extracellular vesicles (EVs). It is a good tool to be used for research on metabolize, cancer and other diseases.

CRBN, namely cereblon, is the substrate recognition subunit of the E3 ubiquitin ligase complex in the ubiquitin-proteasome system. A CRBN ligand library refers to a collection of numerous fragments that can specifically bind to the CRBN protein.

These ligands are mostly designed based on validated CRBN-binding warheads and modified through AI-driven molecular generation optimization systems. They not only include classic lenalidomide-derived structures but also cover novel non-lenalidomide scaffolds. After drug-likeness filtering, these ligands exhibit structural diversity and favorable druggable properties. They can be further optimized and modified to facilitate the development of novel molecular glue degraders, accelerate the discovery of molecular glues that induce interactions between CRBN and new substrate proteins, and enable the exploration of novel CRBN substrates for identifying previously unknown CRBN-binding proteins.

MCE compiles 118 fragments that can specifically bind to the CRBN protein, with molecular weights ranging from 200 to 500. Compounds developed based on the library ligands target multiple disease targets such as cancer and autoimmune diseases, further advancing the development of Molecular Glues and PROTACs therapeutic agents.

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 174 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.

Chemokines, or chemotactic cytokines, are small cytokines or signaling proteins secreted by cells. They are a component of intercellular communication, controlling the directional movement of immune cells especially leukocytes, as well as other cell types, for instance, endothelial and epithelial cells, which are essential to maintain human health and the function of the immune system.

The biological effects of chemokines are achieved by binding to chemokine receptors, which are G protein-coupled receptors found on the surface of leukocytes. Some chemokine receptors are involved in directing tumor metastasis and over-expression by certain tumors. So inhibiting the interaction between chemokine and chemokine receptors on the surface of tumor cells may be a new possible therapeutic approach. Some chemokine receptors are coreceptors for HIV entry, and related inhibitors have been approved by the FDA to treat patients with HIV. Obviously, chemokines and chemokine receptors have become new targets for studying cancer, HIV, inflammation, and other diseases.

MCE supplies a unique collection of 237 chemokine or chemokine receptor inhibitors and activators, all of which have the identified inhibitory or activated effect on chemokine or chemokine receptors. MCE Chemokine Library is a useful tool for drug research related to cancer, AIDS, and wound therapy.

Tonifying traditional Chinese medicines occupy a central position in the traditional medical system, with their core value lying in the regulation of the body's functional state. Modern pharmacological studies have confirmed that these medicinal materials and their monomeric components possess multiple biological activities, including bidirectional immune regulation, anti-aging and lifespan extension, neuroprotection and cognitive enhancement, as well as hematopoietic and metabolic regulation. According to the traditional Chinese medicine theory of “strengthening the body’s resistance and consolidating the foundation”, tonifying medicines are mainly classified into four major categories: Qi-tonifying, Blood-tonifying, Yin-tonifying, and Yang-tonifying. This compound library strictly follows this classification system for compound collection.

Monomeric compounds derived from traditional Chinese medicines demonstrate excellent drug-like properties. They naturally possess structural diversity and clearly defined pharmacological activities, which help improve screening success rates and make them ideal tools for studying multi-target synergistic effects. This library contains 1,030 compounds, providing a material basis for investigating synergistic interactions among compounds (network pharmacology) and facilitating the development of multi-target therapeutic strategies for complex diseases such as cancer, neurodegenerative disorders, and metabolic syndrome.

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.

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.

Dopamine receptor (DAR), widely distributed in the brain, plays a key role in regulating motor function, motivation, driving force and cognition. The role of DA is mediated by D1-type (D1, D5) and D2-type receptors (D2S, D2L, D3, D4), which are distributed in presynaptic, postsynaptic and extrasynaptic, projection neurons and interneurons. Each receptor has a different function. D1 and D5 receptors couple with G stimulation sites and activate Adenylyl cyclase. The activation of Adenylyl cyclase leads to the production of the second messenger cAMP, which leads to the production of protein kinase A (PKA), which leads to further transcription in the nucleus. D2 to D4 receptors are coupled to G inhibitory sites to inhibit adenylyl cyclase and activate potassium Ion channel. These receptors utilize phosphorylation cascades or direct membrane interactions to affect the functions of voltage-gated and neurotransmitter-gated channels, cytoplasmic enzymes, and transcription factors. Dopamine receptor plays an important role in daily life.

MCE designs a unique collection of 263 small molecules related to dopamine receptor. It is a good tool for screening drugs from nervous system disease.

Molecular Glue Virtual Library is constructed using generative AI technology, integrating the structural features, activity data of known molecular glues, and interaction information of ternary complexes (target protein-E3-molecular glue). Endowed with structural novelty, drug-likeness, diversity and synthesizability, it is applicable to molecular glue-based AI drug screening and large-scale virtual screening.

MCE builds this library based on high-quality molecular building blocks by virtue of robust computing power, coupled with rigorous reaction rules and optimized compound generation strategies. To ensure library quality, molecules with high synthetic difficulty, poor drug-likeness, PAINS and other undesirable molecules are excluded first. Subsequently, scaffold-based compound analysis is performed to screen drug-like diverse molecules for synthesizability evaluation; those with excessively high synthetic difficulty are removed, ultimately forming a large-scale molecular glue virtual library with structural diversity, synthesizability and drug-likeness.

Compounds in the library can be synthesized in only 1-2 chemical reaction steps. With MCE’s experienced chemical synthesis team, custom synthesis of different scales from milligram to kilogram can be easily achieved to meet diverse customer needs.

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.

Withdrawal or delisting drugs refer to drugs that are recalled or discontinued from the market due to low efficiency, serious side effects, financial and regulatory problems and other reasons. Once the drug is withdrawn from the market, it will cause heavy losses to the original research company that invested a lot of time, finance and other costs to develop the drug.

Adverse drug reaction (ADR) is the main reason for drug withdrawal from the market. ADR refers to the unexpected effects caused by the reasons such as the target-directed interaction during the treatment. However, studying the mechanism of these ADRs may just be a breakthrough in finding new indications. For example, thalidomide, the protagonist of the drug damage event that caused numerous "seal babies" deformed infants, was found to be due to the degradation of a transcription factor - SALL4 after delisting, which made thalidomide have a new clinical application. In 1998, it was approved by FDA for the treatment of leprosy nodular erythema, and in 2006, it was approved for the treatment of multiple myeloma. ADR study of delisted drugs can not only avoid the loss of drug development in advance but also bring hope to new indications.

MCE has sorted out 231 drug compounds withdrawn from the market through FDA, EMA and other authoritative platforms. Each compound has withdrawal records in at least one country/market. It is a useful tool for conducting research on drug side effects or drug toxicity mechanisms and discovering new indications of drugs.

Currently,the incidence and mortality rates of clinical fungal infections remain high. Existing antifungal drugs are limited in variety and associated with numerous adverse effects, creating an urgent demand for the development of novel antifungal agents. Antifungal compound libraries can support the screening and development of new antifungal drugs.

The mechanisms of action of antifungal drugs cover key processes such as fungal cell membrane synthesis, cell wall synthesis, and cell division. They exert fungicidal or fungistatic effects by specifically targeting different molecular pathways. This library includes a variety of core analogs of antifungal drugs, making it adaptable to antifungal research in diverse scenarios. It can be used for the high-throughput screening of novel antifungal drug candidates, enabling the rapid identification of compounds with potential antifungal activity and facilitating the elucidation of drug-target interactions and resistance mechanisms. Additionally, it supports the screening of compounds and combinations that reverse drug resistance, thereby uncovering the novel antifungal potential of existing compounds.

The library comprises 8350 compounds with a well-defined screening strategy. The core sources of the compounds include analogs of known antifungal active moleculeswith a similarity score of ≥ 0.6 MCE has collected more than 500 antifungal molecules.All screened compounds conform to lead-like physicochemical properties, exhibiting both structural diversity and drug-like characteristics, and providing valuable support for the research and development of novel antifungal drugs.

Targeted Protein Degradation (TPD) is a novel and promising approach to drug development. It shows great potential for targeting proteins traditionally considered "undruggable" due to the lack of enzymatic function and absence of binding sites by tagging them for degradation or recruiting natural degradation mechanisms.

Molecular glues are a type of small-molecule degraders that primarily induce novel interactions between E3 ubiquitin ligases and target proteins, forming ternary complexes that lead to protein ubiquitination and subsequent proteasomal degradation. Compared with PROTACs, molecular glues generally have lower molecular weights, higher cell permeability, and better drug-like properties. Additionally, the design of molecular glues is relatively simple, without the requirements for complex linkers and ligand optimization. As a result, molecular glues have gradually emerged as a promising therapeutic approach for various diseases.

Multiple types of molecular glues have been reported previously. Analysis of co-crystal complex structures reveals that CRBN-related molecular glues are more versatile. Therefore, MCE researchers select active molecules related to these targets as probes for artificial intelligence (AI) screening.Subsequently, molecular docking technology was used to verify whether the screened molecules retained the key pharmacophore features. Ultimately, we obtained 317 molecular glue analogs, and these compounds serve as powerful tools for the research of molecular glues.

Owing to the widespread transmission and frequent mutation of viral diseases, as well as the continuous emergence of new viruses and drug-resistant strains, antiviral drug development is facing increasingly stringent requirements. Antiviral compound libraries serve as important tools for drug screening, mechanism research and development, enabling the discovery and investigation of various antiviral drugs.

These compounds act through diverse antiviral mechanisms, targeting key steps in viral replication, assembly and invasion. They exert antiviral effects by inhibiting viral nucleic acid synthesis, blocking viral protein processing, and preventing viral binding to host cells. This library covers various types of antiviral compounds, including nucleosides, non-nucleosides, protease inhibitors and integrase inhibitors. It supports research on influenza virus, herpes virus, hepatitis virus, emerging respiratory viruses and other pathogens, and enables high-throughput screening of novel antiviral candidates to rapidly identify potential active compounds against diverse viruses. It also facilitates mechanistic studies to elucidate drug-target interactions and viral resistance mechanisms, and supports the screening of effective compounds against mutant strains for research on viral variation and drug resistance.

This antiviral library consists of 6,804 compounds with lead-like physicochemical properties. The core sources of the compounds include analogs of known antiviral molecues with a similarity score ≥ 0.6. MCE has collected more than 1450 antiviral molecules. As a small-molecule collection with both activity potential and structural modifiability, it provides strong support for antiviral drug research and development.

Hepatitis C virus (HCV) is a hepatotropic enveloped positive- strand RNA virus (family Flaviviridae) that infects the parenchymal cells of the liver. HCV infection is a significant public health burden. Globally, an estimated 71 million people have chronic hepatitis C virus infection. A significant number of those who are chronically infected will develop cirrhosis or liver cancer. To date, there is no vaccine against HCV, and combination pegylated alpha interferon (pIFN-) and ribavirin, the main standard-of-care treatment for HCV, is effective in only a subset of patients and is associated with a wide spectrum of toxic side effects and complications. More recently, new therapeutic approaches that target essential components of the HCV life cycle have been developed, including direct-acting antiviral (DAA) that specifically block a viral enzyme or functional protein and host-targeted agents (HTA) that block interactions between host proteins and viral components that are essential to the viral life cycle. However, the genetic diversity of HCV viruses and the stage of liver disease (i.e., cirrhosis) are revealing themselves as obstacles for effective, pan-genotypic treatments. There still exists a need for the discovery and development of new HCV inhibitors. In particular, since the future of HCV therapy will likely consist of a cocktail approach using multiple inhibitors that target different steps of infection, new antivirals targeting all steps of the viral infection cycle.

MCE offers a unique collection of 389 compounds with identified and potential anti-HCV activity. MCE Anti- Hepatitis C Virus Compound Library is a useful tool for discovery new anti-HCV drugs and other anti-infection research.

Oxygen homeostasis regulation is the most fundamental cellular process for adjusting physiological oxygen variations, and its irregularity leads to various human diseases, including cancer. Hypoxia is closely associated with cancer development, and hypoxia/oxygen-sensing signaling plays critical roles in the modulation of cancer progression.

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that functions as a master regulator of oxygen homeostasis. A variety of HF-1 target genes have been identified thus far which encode proteins that play key roles in critical developmental and physiological processes including angiogenesis/vascular remodeling, erythropoiesis, glucose transport, glycolysis, iron transport, and cell proliferation/survival.

HIF-1 is a heterodimeric transcription factor consisting of a constitutively expressed β-subunit and an oxygen-regulated α-subunit. The unique feature of HIF-1 is the regulation of HIF-1α expression and activity based upon the cellular O₂ concentration. Under normoxic conditions, hydroxylation of HIF-1α on these different proline residues is essential for HIF proteolytic degradation by promoting interaction with the von Hippel-Lindau tumor-suppressor protein (pVHL) through hydrogen bonding to the hydroxyproline-binding pocket in the pVHL β-domain. As oxygen levels decrease, hydroxylation of HIF decreases; HIF-1α then no longer binds pVHL, and becomes stabilized, allowing more of the protein to translocate to the cell’s nucleus, where it acts as a transcription factor, upregulating (often within minutes) the production of proteins that stimulate blood perfusion in tissues and thus tissue oxygenation.

MCE offers a unique collection of 3,987 oxygen sensing related compounds targeting HIF/HIF Prolyl-Hydroxylase, MAPK/ERK, PI3K/AKT signaling pathways, etc. MCE Oxygen Sensing Compound Library is a useful tool to study hypoxia, oxidative stress and discover new anti-cancer drugs.