Protein-Protein 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 445 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 373 compounds including peptoid, α-helix mimetics, β-turn/sheets mimetics, etc. This library is an indispensable tool of structure-activity relationships in drug discovery.

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.

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 806 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.

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 707 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.

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

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 374 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.

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.