Targeted selective degradation of Bruton’s tyrosine kinase by PROTACs

Bruton tyrosine kinase degrader BP001 attenuates the inflammation caused by high glucose in raw264.7 cell

BP001 is a promising small molecule compound that has been specifically designed to target and degrade Bruton's tyrosine kinases (BTK), which is known to play a crucial role in lymphoma development. Macrophages are important immune cells in inflammation regulation and immune response. In this study, we aimed to investigate the effect of BP001 on RAW264.7 macrophage activation stimulated by a high glucose environment. Our findings revealed that treatment with BP001 significantly inhibited the production of nitric oxide (NO), reactive oxygen species (ROS), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) in RAW264.7 macrophages exposed to high glucose conditions. Furthermore, we observed that BP001 treatment also down-regulated the expression of BTK in these activated macrophages. To elucidate the underlying mechanism behind these observations, we investigated the phosphorylation level of NF-κB. Our results demonstrated that BP001 treatment led to decreased phosphorylation levels of NF-κB, thereby inhibiting the level of inflammation. In addition, we also found that BP001 could restore RAW264.7 macrophages from the pro-inflammatory state to the normal phenotype and reduce the occurrence of inflammation. The regulatory function of BP001 in autoimmunity is mediated through the degradation of BTK protein, thereby attenuating macrophage activation. Additionally, BTK plays a pivotal role in transcriptional regulation by inducing NF-κB activity. Consequently, it is not difficult to understand that BP001 effectively inhibits inflammation. In conclusion, the present study provides evidence that BP001, a BTK degrader, can serve as a novel immunomodulator of inflammation induced by high glucose, making it an attractive candidate for further investigation.

Discovery of Novel Potent and Fast BTK PROTACs for the Treatment of Osteoclasts-Related Inflammatory Diseases

Bruton's tyrosine kinase (BTK) is an attractive target in inflammatory and autoimmune diseases. However, the effectiveness of BTK inhibitors is limited by side effects and drug resistance. In this study, we report the development of novel BTK proteolysis targeting chimeras (PROTACs) with different classes of BTK-targeting ligands (e.g., spebrutinib) other than ibrutinib. Compound 23 was identified as a potent and fast BTK PROTAC degrader, exhibiting outstanding degradation potency and efficiency in Mino cells (DC50, 4 h = 1.29 ± 0.3 nM, t1/2, 20 nM = 0.59 ± 0.20 h). Furthermore, compound 23 forms a stable ternary complex, as confirmed by the HTRF assay. Notably, 23 down-regulated the BTK-PLCγ2-Ca2+-NFATc1 signaling pathway activated by RANKL, thus inhibiting osteoclastogenesis and attenuating alveolar bone resorption in a mouse periodontitis model. These findings suggest that compound 23 is a potent and promising candidate for osteoclast-related inflammatory diseases, expanding the potential of BTK PROTACs.

Exploring the target scope of KEAP1 E3 ligase-based PROTACs

Targeted protein degradation (TPD) uses small molecules to recruit E3 ubiquitin ligases into the proximity of proteins of interest, inducing ubiquitination-dependent degradation. A major bottleneck in the TPD field is the lack of accessible E3 ligase ligands for developing degraders. To expand the E3 ligase toolbox, we sought to convert the Kelch-like ECH-associated protein 1 (KEAP1) inhibitor KI696 into a recruitment handle for several targets. While we were able to generate KEAP1-recruiting degraders of BET family and murine focal adhesion kinase (FAK), we discovered that the target scope of KEAP1 was narrow, as targets easily degraded using a cereblon (CRBN)-recruiting degrader were refractory to KEAP1-mediated degradation. Linking the KEAP1-binding ligand to a CRBN-binding ligand resulted in a molecule that induced degradation of KEAP1 but not CRBN. In sum, we characterize tool compounds to explore KEAP1-mediated ubiquitination and delineate the challenges of exploiting new E3 ligases for generating bivalent degraders.

PROTACs: great opportunities for academia and industry (an update from 2020 to 2021)

PROteolysis TArgeting Chimeras (PROTACs) technology is a new protein-degradation strategy that has emerged in recent years. It uses bifunctional small molecules to induce the ubiquitination and degradation of target proteins through the ubiquitin-proteasome system. PROTACs can not only be used as potential clinical treatments for diseases such as cancer, immune disorders, viral infections, and neurodegenerative diseases, but also provide unique chemical knockdown tools for biological research in a catalytic, reversible, and rapid manner. In 2019, our group published a review article "PROTACs: great opportunities for academia and industry" in the journal, summarizing the representative compounds of PROTACs reported before the end of 2019. In the past 2 years, the entire field of protein degradation has experienced rapid development, including not only a large increase in the number of research papers on protein-degradation technology but also a rapid increase in the number of small-molecule degraders that have entered the clinical and will enter the clinical stage. In addition to PROTAC and molecular glue technology, other new degradation technologies are also developing rapidly. In this article, we mainly summarize and review the representative PROTACs of related targets published in 2020-2021 to present to researchers the exciting developments in the field of protein degradation. The problems that need to be solved in this field will also be briefly introduced.

Targeting Protein Kinases Degradation by PROTACs

Kinase dysregulation is greatly associated with cell proliferation, migration and survival, indicating the importance of kinases as therapeutic targets for anticancer drug development. However, traditional kinase inhibitors binding to catalytic or allosteric sites are associated with significant challenges. The emergence of resistance and targeting difficult-to-degrade and multi-domain proteins are significant limiting factors affecting the efficacy of targeted anticancer drugs. The next-generation treatment approaches seem to have overcome these concerns, and the use of proteolysis targeting chimera (PROTAC) technology is one such method. PROTACs bind to proteins of interest and recruit E3 ligase for degrading the whole target protein via the ubiquitin-proteasome pathway. This review provides a detailed summary of the most recent signs of progress in PROTACs targeting different kinases, primarily focusing on new chemical entities in medicinal chemistry.

Small molecule approaches to treat autoimmune and inflammatory diseases (Part I): Kinase inhibitors

Autoimmune and inflammatory diseases place a huge burden on the healthcare system. Small molecule (SM) therapeutics provide much needed complementary treatment options for these diseases. This digest series highlights the latest progress in the discovery and development of safe and efficacious SMs to treat autoimmune and inflammatory diseases with each part representing a class of SMs, namely: 1) protein kinases; 2) nucleic acid-sensing pathways; and 3) soluble ligands and receptors on cell surfaces. In this first part of the series, the focus is on kinase inhibitors that emerged between 2018 and 2020, and which exhibit increased target and tissue selectivity with the aim of increasing their therapeutic index.

Progress in the Development of Small Molecular Inhibitors of Focal Adhesion Kinase (FAK)

Focal adhesion kinase (FAK) is a nonreceptor intracellular tyrosine kinase that plays an essential role in cancer cell adhesion, survival, proliferation, and migration through both its enzymatic activities and scaffolding functions. Overexpression of FAK has been found in many human cancer cells from different origins, which promotes tumor progression and influences clinical outcomes in different classes of human tumors. Therefore, FAK has been considered as a promising target for small molecule anticancer drug development. Many FAK inhibitors targeting different domains of FAK with various mechanisms of functions have been reported, including kinase domain inhibitors, FERM domain inhibitors, and FAT domain inhibitors. In addition, FAK-targeting PROTACs, which can induce the degradation of FAK, have also been developed. In this Perspective, we summarized the progress in the development of small molecular FAK inhibitors and proposed the perspectives for the future development of agents targeting FAK.