How a Heart Drug Could Pave the Way for Targeted Lymphoma Treatments

In a groundbreaking advance poised to reshape the landscape of cancer therapeutics, a research team at the VCU Massey Comprehensive Cancer Center has uncovered a novel method to repurpose an established antiarrhythmic drug to selectively disrupt enzymatic functions implicated in lymphoid malignancies. This discovery leverages the unique structural domains of the USP11 enzyme, representing a strategic departure from conventional approaches and illuminating a promising avenue for precision oncology. The study, recently published in Pharmacological Research, lays the foundation for targeting non-catalytic regions of enzymes to elicit potent anti-tumor effects while minimizing collateral toxicity.

USP11, a member of the deubiquitinase (DUB) family, orchestrates the stability of numerous intracellular proteins by cleaving ubiquitin moieties, thus regulating critical cellular processes including protein degradation, DNA repair, and signal transduction. Traditionally, drug discovery efforts have focused on inhibiting the catalytic active site of these enzymes. However, the catalytic domains of DUB family members exhibit considerable structural homology, posing a formidable barrier to achieving selective inhibition. Additionally, active site inhibitors frequently suffer from suboptimal pharmacokinetic properties and limited in vivo efficacy.

The innovative approach adopted by the VCU team circumvents these limitations by targeting USP11’s ubiquitin-like (UBL) domain—a non-enzymatic scaffolding region essential for mediating protein-protein interactions specific to USP11. This domain is structurally divergent from analogous regions in closely related enzymes such as USP4 and USP15, offering a unique target for selective modulation. By focusing on the scaffolding function rather than the catalytic mechanism, the researchers have unlocked a previously unexploited therapeutic vulnerability.

Central to this discovery was the application of advanced computational chemistry. Led by Professor Glen E. Kellogg, Ph.D., the team conducted an extensive structure-based virtual screen of over ten million compounds to identify molecules capable of binding USP11’s UBL domain with high specificity. Their efforts culminated in the identification of RBF4, a molecule that exhibited potent inhibition of USP11’s scaffolding interactions without disrupting catalytic activity. Remarkably, RBF4 was chemically identical to dronedarone, an FDA-approved drug commonly used to treat cardiac arrhythmias.

The pharmacological profile of RBF4 revealed a compelling therapeutic window: it demonstrated significant cytotoxicity towards diffuse large B-cell lymphoma (DLBCL) cells, one of the most aggressive and prevalent subtypes of non-Hodgkin lymphoma, while sparing normal immune cells. Preclinical models engineered to mimic MYC-driven lymphoma exhibited dramatic tumor regression, reduced metastatic dissemination, and prevention of malignant effusions upon treatment with RBF4. Notably, these anti-cancer effects emerged without overt toxicity to surrounding healthy tissues, underscoring the potential clinical applicability of this approach.

The serendipitous identification of an existing drug as a potent USP11 inhibitor holds profound implications for translational oncology. Because dronedarone has already undergone rigorous safety evaluation and clinical use, repurposing it for lymphoma therapy could significantly accelerate the transition from bench to bedside. This discovery exemplifies a powerful strategy for drug repurposing by targeting non-catalytic enzyme domains, potentially bypassing the protracted timelines and substantial costs associated with de novo drug development.

Dr. Ronald Gartenhaus, the study’s senior author and a distinguished expert in lymphoma biology, emphasized the transformative nature of these findings. By redefining the functional landscape of USP11 and elucidating the mechanisms underlying RBF4’s anti-tumor activity, the research challenges long-standing paradigms and opens new therapeutic avenues in cancer treatment. This precision approach not only enhances selectivity but also enriches our understanding of the multifaceted roles that DUB enzymes play in tumorigenesis.

Further building on prior research from this team—published in Nature Communications—which highlighted USP11’s pivotal role in modulating RNA translation and protein synthesis in lymphoma cells, this current work demonstrates how disrupting scaffolding functions translates into tangible anti-cancer consequences. Targeting non-catalytic domains may thus represent a broader principle applicable to other enzymes and cancer types characterized by complex multi-domain architectures.

Moving forward, collaborative efforts with clinicians such as Dr. Victor Yazbeck, a hematologist-oncologist at Massey, aim to transition these promising preclinical observations into early-phase clinical trials. Should RBF4 prove effective in human patients with lymphoma, its therapeutic potential could extend well beyond hematologic cancers. USP11’s involvement in diverse solid tumors—including breast, cervical, colorectal, esophageal, liver, ovarian, and pancreatic cancers—highlights the breadth of impact that selective USP11 inhibition might achieve.

This pioneering research was made possible by the interdisciplinary collaboration among experts in oncology, pharmacology, computational chemistry, and clinical medicine, spanning institutions such as the VCU School of Medicine, the VCU School of Pharmacy, the Maryland Healthcare System, and the Richmond Veterans Affairs Medical Center. Their collective expertise underscores the significance of integrated approaches in unraveling complex biological targets and translating these insights into innovative therapies.

Ultimately, the discovery of USP11’s non-catalytic domain as a druggable site, coupled with the fortuitous repurposing of an existing medication, represents a paradigm shift in cancer therapeutics. It exemplifies how deep mechanistic understanding paired with cutting-edge computational tools can reveal concealed vulnerabilities within cancer cells. This strategy not only promises enhanced efficacy but also the prospect of reducing adverse effects, a critical consideration for improving patient quality of life during treatment.

As the oncology community eagerly anticipates the initiation of clinical trials to validate these findings in patients, there is a palpable sense of optimism. The convergence of molecular biology, pharmacology, and computational sciences heralds a new era where precision medicine can be realized through innovative targeting strategies. By exploiting the non-enzymatic functions of enzymes like USP11, researchers have opened an exciting frontier for the development of next-generation cancer therapies.

• https://www.sciencedirect.com/science/article/pii/S1043661825005006?via%3Dihub
• https://www.cancer.org/cancer/types/non-hodgkin-lymphoma/about/b-cell-lymphoma.html
• https://www.nature.com/articles/s41467-018-03028-y
  References: 10.1016/j.phrs.2025.108075
  Keywords: Lymphoma, Enzyme inhibitors, Cancer treatments, Computational chemistry, B cell lymphoma, RNA transcripts