Biology subjects

Mukerji, R.

Publications and source records attributed to Mukerji, R..

3 recordsLinked to original sources

bioRxiv2026

Bexobrutideg: A Selective, Catalytic Degrader of Bruton's Tyrosine Kinase Overcomes Inhibitor Resistance and Suppresses Autoantibody-Mediated Disease

Brutons tyrosine kinase (BTK) transduces B-cell receptor (BCR), Toll-like receptor (TLR), and Fc receptor (FcR) signaling, and overactivation of these pathways drives B-cell malignancies and antibody-mediated autoimmune disease. Small molecule inhibitors block the enzymatic functions of BTK, but this inhibition is undermined by resistance mutations, several of which abolish BTKs kinase activity yet promote oncogenic signaling through BTK scaffolding functions. We report the discovery and characterization of bexobrutideg (NX-5948), a heterobifunctional degrader that recruits cereblon (CRBN) to selectively degrade BTK while sparing molecular glue neosubstrates. We demonstrate that bexobrutideg acts catalytically, degrading thousands of copies of BTK per molecule per hour, and this event-driven pharmacology renders it resilient to mutations that confer resistance to both covalent- and noncovalent-inhibitors. Bexobrutideg is orally bioavailable, driving deep and durable BTK degradation across species. Bexobrutideg demonstrates strong efficacy in wild-type and ibrutinib-resistant lymphoma models and robustly suppresses pathway activation in models of autoimmune disease.

cancer biology↗

bioRxiv2026

Small-molecule CBLB inhibitor abolishes EGFR ubiquitination, reduces receptor endocytosis and diminishes cell motility signaling

Endocytosis of the epidermal growth factor receptor (EGFR) is considered a key regulator of the receptor signaling activity. However, the molecular mechanisms underlying EGFR endocytosis are incompletely understood. Although ligand-induced ubiquitination of EGFR is known to promote its endocytic trafficking, the importance of EGFR ubiquitination in clathrin-mediated endocytosis, the primary physiological route of EGFR internalization, remains debated, and the relative contributions of ubiquitination-dependent and - independent mechanisms are not defined. Hence, we used NX-1013, a novel small-molecule inhibitor of the CBLB E3 ubiquitin ligase, to dissect the role of EGFR ubiquitination in its endocytic trafficking and signaling. Strikingly, brief treatment with NX-1013 completely abolished EGF-induced EGFR ubiquitination, demonstrating that this process is exclusively mediated by the closely related CBLB and CBL ligases. NX-1013 inhibited clathrin-mediated internalization of activated EGFR by 60-70%. The remaining, ubiquitination-independent internalization required EGFR kinase activity, was highly clathrin-dependent, and was significantly impaired by depletion of the AP-2 clathrin adaptor complex. Interestingly, inhibition of CBLs and EGFR endocytosis by NX-1013 did not affect major downstream signaling pathways in human oral squamous cell carcinoma cells, with the exception of Rac1 activation and EGFR-dependent cell migration, both of which were suppressed. Significance StatementCBL E3 ubiquitin ligases mediate ubiquitin conjugation of EGFR but their functional contributions to EGFR endocytic trafficking and signaling remain poorly defined. Here, we describe a newly developed small-molecule inhibitor of CBL proteins that potently blocks EGFR ubiquitination. This tool allowed us to dissect ubiquitination-dependent versus - independent components of the clathrin-mediated endocytosis and ligand-induced downregulation of EGFR. Strikingly, while inhibition of CBLs suppressed EGFR-driven cell motility signaling, it spared other major downstream pathways in EGFR-dependent human oral squamous cell carcinoma cells. These findings establish acute inhibition of CBLs as a powerful approach to interrogate ubiquitin-mediated receptor regulation and highlight its potential for therapeutic targeting of cancer cell migration.

cell biology↗

bioRxiv2026

Discovery and characterization of small molecule inhibitors of CBL-B that act as intramolecular glue to enhance T-cell anti-tumor activity

CBL-B is a RING-type E3 ubiquitin ligase that acts as a critical negative regulator of T-cell activation. It promotes T-cell anergy and suppresses immune responses through ubiquitin-mediated control of signaling proteins at the immunological synapse. T cells deficient in CBL-B activity lose their dependence on CD28 co-stimulation, exhibit heightened activation and increased cytokine production, and fail to re-establish anergy. In addition, mice deficient in CBL-B activity reject tumors. Together, this cellular mechanism and in vivo phenotype suggest inhibition of CBL-B may be a viable immuno-oncology therapeutic strategy. Here, we report the rational design and execution of a high-throughput screen (HTS) to identify small molecule inhibitors of CBL-B. This campaign led to the discovery of a scaffold that inhibits CBL-B E3 ligase activity with micromolar potency. Structural characterization revealed an intramolecular glue mechanism, in which the compound stabilizes the closed state of CBL-B, preventing phosphorylation of a tyrosine residue that is critical for activation and E2 binding. Iterative structure-activity optimization yielded compounds with nanomolar activity that enhanced T-cell activation and cytokine secretion in primary human T cells and suppressed tumor growth in a syngeneic colorectal mouse model. Together, these studies validate the biological rationale for pharmacological CBL-B inhibition and enabled the de novo discovery of intramolecular CBL-B glue inhibitors. This work culminated in the identification of NX-1607, a first-in-class oral CBL-B inhibitor now in clinical development for cancer immunotherapy.

immunology↗