This article explores the promising strategy of drug repurposing, specifically investigating how anthelmintic benzimidazole derivatives—traditionally used to treat parasitic infections—can be effectively redirected as novel anticancer therapeutics for various blood malignancies. The article synthesizes in vitro and in vivo evidence showing that compounds such as mebendazole, albendazole, flubendazole, and fenbendazole can significantly suppress cancer cell proliferation, induce apoptosis, and disrupt key oncogenic signaling pathways while sparing healthy cells. Furthermore, the text highlights the potential of combining these repurposed medications with standard-of-care treatments to overcome drug resistance, reduce systemic toxicity, and ultimately improve clinical outcomes for patients suffering from hematological cancers such as leukemia, lymphoma, and multiple myeloma. This article discusses in vitro and in vivo preclinical testing (lab & animal).
Benzimidazole derivatives are a class of heterocyclic aromatic compounds defined by a fused six-membered benzene ring and a five-membered imidazole ring. Originally synthesized in 1872 and widely adopted in the early 1960s, these compounds were initially developed as anthelmintics in human and veterinary medicine to treat gastrointestinal parasitic infections. In parasites, they primarily function by selectively binding to \(\beta\)-tubulin to block microtubule assembly and by disrupting glucose transport and energy metabolism.
Through drug repurposing, benzimidazole derivatives have emerged as significant multi-targeted agents in oncology, categorized into FDA-approved targeted therapies, clinical pipeline compounds, and repurposed anthelmintics:
1. FDA-Approved & Clinical Benzimidazole Anticancer Drugs
Bendamustine: Currently the primary FDA-approved benzimidazole derivative used for chronic lymphocytic leukemia (CLL), multiple myeloma (MM), and non-Hodgkin’s lymphoma. In advanced CLL, bendamustine achieved a 68% complete or partial response rate and a median progression-free survival of 21.6 months (compared to 31% and 8.3 months with chlorambucil). Unlike standard alkylating agents, it drives an 8-fold upregulation of Ser15-phosphorylated p53, activates DNA damage stress responses, and triggers mitotic catastrophe.
Clinical Pipeline Derivatives: Advanced clinical-stage candidates featuring benzimidazole moieties include Selumetinib (a selective MEK1/2 inhibitor), Binimetinib, Abemaciclib (CDK4/6 inhibitor), Pracinostat (HDAC inhibitor), Pevonedistat, and Galeterone (androgen receptor/eIF4E inhibitor).
2. Anthelmintic Benzimidazoles (Human & Veterinary)
Anthelmintic benzimidazoles are grouped by their clinical approval targets:
Human Medicine: Mebendazole (MBZ), Albendazole (ABZ), Flubendazole (FLBZ), and Ricobendazole.
Veterinary Medicine: Fenbendazole (FBZ), Parbendazole, Oxfendazole, and Oxibendazole.
3. Primary Molecular Mechanisms of Action in Cancer
Tubulin Depolymerization & Mitotic Arrest: Repurposed benzimidazoles bind to tubulin subunits, inhibiting polymerization and capturing dividing cells in G2/M phase cell cycle arrest. Flubendazole binds tubulin at a site distinct from vinblastine, allowing it to bypass P-glycoprotein-mediated vinblastine resistance and act synergistically with Vinca alkaloids.
Proteasomal Degradation of Oncogenic Transcription Factors:
c-MYB: Mebendazole interferes with the HSP70 chaperone system, inducing proteasomal degradation of the c-MYB transcription factor in acute myeloid leukemia (AML) without harming normal CD34+ cord blood stem cells.
GLI1 & GLI2: Mebendazole inhibits HSP70/90 chaperone activity, driving proteasomal degradation of Hedgehog signaling effectors GLI1 and GLI2.
c-Maf: Mebendazole suppresses the deubiquitinase USP5, triggering degradation of the c-Maf oncogene in multiple myeloma.
Blast Differentiation Therapy: Rather than solely relying on non-specific cytotoxicity, benzimidazoles force immature malignant blasts into terminal differentiation. Fenbendazole transforms HL-60 leukemic blasts into mature granulocytes with 14.5-fold higher selectivity over normal stem cells, while albendazole differentiates non-APL AML cells into monocytes via the KLF4–DPYSL2A axis.
Oncogenic Cascade Blockade:
PI3K/AKT & ERK1/2: Mebendazole suppresses AKT and ERK1/2 phosphorylation in leukemic cells.
NF-\(\kappa\)B Pathway: Albendazole downregulates p65 and phospho-p65, depleting ALDH1+ cancer stem cells and resensitizing myeloma cells to bortezomib.
Notch1 Signaling: Mebendazole downregulates Notch1 intracellular domain (NICD), c-Myc, and Hes1 expression in chemoresistant T-ALL models.
Loss of Heterozygosity (LOH): Albendazole acts as a potent spindle poison, accelerating chromosomal missegregation and driving Loss of Heterozygosity (LOH) in mammalian cells.
4. Therapeutic Bottlenecks
A primary challenge with conventional anthelmintic benzimidazoles is their poor aqueous solubility and rapid systemic clearance, alongside potential toxicities such as embryotoxicity. Consequently, current research focuses on novel formulations, nanocarriers, and combination strategies with standard chemotherapy to maximize systemic bioavailability and therapeutic efficacy.
Source:
Golla, U., Patel, S., Shah, N., Talamo, S., Bhalodia, R., Claxton, D., Dovat, S., & Sharma, A. (2024). From deworming to cancer therapy: Benzimidazoles in hematological malignancies. Cancers, 16(20), 3454.