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At the forefront of innovative drug discovery, every medicinal chemist faces the challenge of rapidly identifying high-quality hit compounds from vast repositories of chemical resources.

The MCE Natural Product Diversity Scaffold Library is the result of a streamlined optimization process built upon our existing natural product collection. Adhering to the rigorous selection principle of "retaining only one representative compound per BMS scaffold", we have concentrated the diversity of thousands of compounds into a high-value, low-redundancy core set containing 2,256 compounds. All compounds are derived from natural sources, inheriting their inherent advantages of structural complexity and drug-likeness. By eliminating redundancy, the library size is significantly reduced without any compromise to chemical diversity. This approach effectively lowers the cost and time required for primary screening while simplifying downstream data analysis and structure-activity relationship (SAR) studies.

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 468 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.

DNA damage response (DDR) is a fundamental mechanism for maintaining genomic stability. When DNA damage occurs, such as single- or double-strand breaks or replication fork stalling, cells rely on key proteins including ATM, ATR, PARP, and DNA-PK to sense the damage and transmit signals, thereby regulating DNA repair, cell-cycle arrest, and cell death. Inhibition of specific DNA repair or checkpoint pathways can prevent tumor cells from effectively repairing accumulated DNA damage, ultimately leading to tumor cell death.

MCE DNA Damage Repair Inhibitor Library contains 1,544 compounds, focusing on key nodes involved in DNA damage response and DNA repair. The library covers multiple DNA repair and cell-cycle checkpoint pathways, providing a systematic compound screening tool for research on precision oncology, synthetic lethality, drug resistance mechanisms, and chemo- or radiosensitization.

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 6,553 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.

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.

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.

A diverse compound library with favorable ADMET properties (Absorption, Distribution, Metabolism, Excretion, and Toxicity) is crucial in drug discovery. Early evaluation of ADMET properties allows for the exclusion of molecules with unfavorable profiles at the initial stages, thereby reducing the risk of late-stage development failures, lowering R&D costs, and accelerating optimization of lead compounds. Based on predictions from ADMET-related AI algorithms, the compounds in this library are predicted to exhibit favorable oral bioavailability (F > 30%), reasonable plasma protein binding (PPB < 98%), minimized CYP3A4 inhibition potential (inhibition probability < 50%, CYP3A4 is the most critical drug-metabolizing enzyme in the cytochrome P450 family) , low toxicity profiles, with 140 potentially toxic substructures pre-identified and excluded via substructure searching to eliminate compounds containing hazardous fragments. The diversity library enables broad applicability in high-throughput screening (HTS) and high-content screening (HCS).

Endoplasmic reticulum (ER) contributes to the production and folding of approximately one third of cellular proteins, and is thus inextricably linked to the maintenance of cellular homeostasis and the fine balance between health and disease. However, some adverse factors negatively impact ER functions and protein synthesis, resulting in the activation of Endoplasmic reticulum stress (ER stress, ERS) and unfolded protein response (UPR) signaling pathways. The UPR is triggered when ER protein folding capacity is overwhelmed by cellular demand and the UPR initially aims to restore ER homeostasis and normal cellular functions. However, if this fails, then the UPR triggers cell death. Chronic ER stress and defects in UPR signaling are emerging as key contributors to a growing list of human diseases, including diabetes, neurodegeneration and cancer.

MCE Endoplasmic Reticulum Stress Compound Library contains 379 ER stress-related compounds that mainly target PERK, IRE1, ATF6, etc. MCE ER stress library is a useful tool for researching ER stress and related diseases.

Unlike highly conserved orthosteric sites, allosteric sites exhibit low conservation, high hydrophobicity, weak polarity, confined geometry, and dynamic cryptic properties. Rather than rigid keyhole-like cavities, they typically appear as flexible grooves, subunit interface clefts, or shallow depressions formed by protein conformational changes.

Based on the dynamic, hydrophobic, and elongated nature of allosteric pockets, MCE has carried out targeted fragment modification and screening under strict physicochemical criteria: MW 120–280 Da, HBD ≤ 2, HBA ≤ 3, PSA 30–80 Ų, rotatable bonds ≤ 2, cLogP 1–3.5. High 3D diversity was further ensured by PMI analysis, yielding fragments with excellent shape complementarity to allosteric pockets.

This library contains 1,800 structurally diverse, drug-like fragments, this library supports allosteric drug development and pocket optimization. It significantly improves screening hit rates and enables efficient, precise early-stage R&D of allosteric drugs.

Proteolysis-targeting chimera (PROTAC) has been developed to be a useful technology for targeted protein degradation. PROTACs consist of a ligand for E3 ligase (E3 ligase binder), a linker and a ligand (mostly small-molecule inhibitor) for protein of interest（target binder）. Upon binding to the target protein, the PROTACs can recruit E3 for target protein ubiquitination, which is subjected to proteasome-mediated degradation.

Although there are more than 600 E3 ubiquitin ligases, only several with small molecule ligands have been used for designing PROTACs, including Skp1-Cullin-F box complex containing Hrt1 (SCF), Von Hippel-Lindau tumor suppressor (VHL), Cereblon (CRBN), inhibitor of apoptosis proteins (IAPs), and mouse double minute 2 homolog (MDM2).

MCE carefully prepared a unique collection of 187 ligands for E3 ligase, which have been reported to be used in PROTAC design. MCE E3 ligase ligand library is a useful tool for PROTAC development.

Linkers, as key structural units in PROTAC molecules that connect the two functional ends, not only determine the overall molecular conformation and spatial compatibility but also directly influence the stability of the ternary complex, as well as cellular permeability and degradation efficiency. In recent years, with the widespread application of click chemistry in medicinal chemistry, the incorporation of bioorthogonal reactive groups such as azides (-N₃) into PROTAC linker design has become an emerging research focus, providing an important tool for modular assembly and rapid structural optimization.

The MCE Azide PROTAC Linker Library contains 0 linkers specifically designed for targeted protein degradation molecule design and optimization. These linkers serve as efficient “click handles,” enabling rapid and highly selective covalent coupling with alkyne reaction partners, thereby facilitating modular assembly and structural diversification of PROTAC molecules. In drug development, this design not only improves the efficiency of molecular construction but also significantly accelerates the screening and optimization of lead compounds. Meanwhile, by tuning linker properties such as length, flexibility, and polarity, the ability to form ternary complexes and degradation activity can be optimized.

Bioactive small molecules are important sources of lead compounds and effective tools for drug screening. Because the target of active small molecules is clear, it is conducive to the study of mechanism. In addition, due to the large structural differences between the individual active molecules, it is easier to obtain a greater variety of lead compounds.

MCE integrates the Bioactive Compound Library (HY-L001) and Novel Bioactive Compound Library (HY-L111) to form the Bioactive Compound Library Max. Bioactive Compound Library Max contains novel active small molecules, molecules that have entered the clinical stage and the market, and small molecules that have been verified by cell experiments or biochemical experiments, which fundamentally expands the number of compound libraries in the library and improves the structural diversity, and is an effective tool to start drug screening and mechanism research.

MCE can provide a library of 30,147 mitophagy compounds, which can be used for drug development and mechanism research in cancer, immunity, infection and other hot research fields.

Natural products are small-molecule compounds produced in nature, derived from animals, plants, and microorganisms, including both primary and secondary metabolites. With their structural diversity and favorable biological activities, natural products have long been an important source for drug discovery. Traditional natural product research has often focused on isolating single active components, whereas metabolomics emphasizes a holistic approach—comprehensively detecting all metabolites in a sample and systematically capturing both known and unknown constituents. Consequently, mass spectrometry‑based metabolomics databases have become a key technological support for screening known components and identifying unknown compounds from natural sources.

MCE Mass Spectrometry Natural Product Library contains 4,412 natural products, covering multiple structural classes, including sugars and glycosides, phenylpropanoids, quinones, flavonoids, terpenoids, etc. All compounds have undergone rigorous quality control by LC/MS and other analytical methods, and can serve as high‑purity reference standards for metabolite identification.

In modern medicinal chemistry and chemical biology research, alkyne (-C≡C-) structures play an important role in click chemistry, bioorthogonal labeling, and the construction of functional molecules due to their unique linear geometry and high reactivity. In particular, driven by the development of copper-catalyzed azide-alkyne cycloaddition (CuAAC) and copper-free click reactions (SPAAC), terminal alkyne groups have become important “chemical handles” for building complex biomolecular systems.

The MCE Alkyne Compound Library contains 437 compounds designed for the construction of click chemistry reaction systems and the development of diverse functional molecules. In drug discovery, these structures serve as key reactive sites that can efficiently undergo click reactions with azide groups, enabling modular assembly of PROTAC molecules, construction of ADC linkers, and rapid synthesis of bioorthogonal labeling probes. In addition, alkyne groups exhibit high stability, mild reaction conditions, and excellent biocompatibility, allowing them to maintain reactivity in complex biological environments. This contributes to improved efficiency and controllability in drug development, making them indispensable chemical building blocks in modern drug design and functional molecular engineering.

The anti-cancer drug library meticulously collects all drugs approved by FDA and other major national drug regulatory authorities for cancer treatment. These drugs cover a variety of cancer types, including but not limited to lung cancer, breast cancer, colorectal cancer, leukemia, and other common cancers. The library includes a wide range of drugs, from classic chemotherapeutic agents to cutting-edge targeted therapies and immunotherapies. It contains various types of drug compounds with different mechanisms of action. There are cytotoxic drugs that directly kill cancer cells, as well as drugs that work by modulating the tumor microenvironment, inhibiting tumor angiogenesis, and activating the immune system. This diversity provides researchers with a broad range of perspectives and options for intervention strategies.

This library can be used for basic research on cancer treatment, exploring new targets and new mechanisms of drug action; Conducting drug reuse research to look for potential therapeutic effects of existing drugs on other cancer types or diseases; Or conducting research into combination drugs to optimize cancer treatment.

MCE has collected 265 small-molecule compounds with cancer indications, which are good tools for drug repurposing.

Lysine is the second most common target residue used in the design of TCIs and related covalent ligands. Its appeal lies in its abundance in human proteins, which is approximately three times higher than that of cysteine (5.8% vs. 1.9%). This significantly increases the number of proteins suitable for covalent targeting, especially given that many human proteins lack ligandable cysteine residues. Moreover, it has been suggested that functional lysines have a lower probability of being replaced by mutation, as they often play a crucial role in catalysis by acting as bases or nucleophiles. Additionally, lysines are essential for maintaining the structural integrity of proteins and for regulating post-translational modifications (PTMs). Consequently, targeting lysine has garnered significant interest in recent years.

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 445 fragment molecules which can target lysine residue and can be used for fragment-based covalent drug discovery.

New drug development is a time-consuming and high-cost process. Drug repurposing (also called drug repositioning, reprofiling or re‑tasking) offers various advantages over developing an entirely new drug for a given indication. First, the risk of failure is lower. Second, the time frame for drug development can be reduced. Third, less investment is needed. Approved and clinical drugs, especially after phase I drugs, have identified bioactivities, good pharmacokinetic characteristics and safety, which are suitable for drug repurposing.

MCE Drug Repurposing Compound Library plus contains 6,142 approved and passed phase I clinical drugs, which have been completed extensive preclinical and clinical studies and have well-characterized bioactivities, safety and bioavailability properties.

MCE Drug Repurposing Compound Library plus, with more powerful screening capability, further complement MCE Drug Repurposing Compound Library (HY-L035) by adding some compounds with low solubility or stability (Part B) to this library. All those supplementary compounds are supplied in powder form.

Flavors and fragrances serve as indispensable enhancing elements in modern industries, playing multidimensional roles in the fields of food, cosmetics, and pharmaceutical development. In the food industry, flavors and fragrances are not only used to compensate for flavor loss during processing but also to create novel sensory experiences and enhance product appeal. Natural flavors such as vanilla and citrus oils impart rich, layered aromas to foods, while synthetic flavors can precisely replicate specific tastes, meeting the demands of standardized production and extending the flavor stability of food products. In the cosmetics sector, flavors and fragrances are key to emotional design. They enhance product recognition and elevate the pleasure of use through pleasant scents. In pharmaceutical development, the application of flavors and fragrances focuses on improving compliance. Especially in formulations such as oral liquids and chewable tablets, the addition of mint, fruit, and other flavoring components effectively masks the bitter or irritating taste of medications, increasing patient acceptance. Additionally, some natural flavors may themselves possess auxiliary therapeutic benefits.

MCE contains 495 kinds of flavors and fragrances, which can be used in fields such as food, cosmetics and drug development.

KRAS (Kirsten Rat Sarcoma Viral Oncogene Homolog) is one of the most important oncogenic driver genes in oncology, with high mutation frequencies in pancreatic cancer, non‑small cell lung cancer, and colorectal cancer. For a long time, KRAS was considered "undruggable" due to the lack of suitable small‑molecule binding pockets on its protein surface. In recent years, with the discovery of the switch‑II pocket and the successful approval of KRAS G12C inhibitors, KRAS‑targeted research has achieved groundbreaking progress, which has also spurred a wave of development targeting non‑G12C mutants such as G12D and G12V, as well as upstream and downstream regulatory factors including SOS1 and SHP2.

MCE KRAS Targeted Compound Library contains 82 small‑molecule compounds targeting the KRAS, serving as high‑quality research tools for mechanistic studies of KRAS‑mutant tumors, combination therapy development, resistance mechanism exploration, and high‑throughput drug screening, thereby providing robust support for KRAS‑targeted drug discovery.

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 covalent inhibitor library contains 1,618 small molecules including identified covalent inhibitors and other bioactive molecules having common covalent reactive groups as warheads, such as acrylamides, activated terminal acetylenes, Sulfonyl fluorides/esters, cloracetamides, alkyl halides, epoxides, aziridines, disulfides, etc.