Tubulin inhibitors(University of Münster)

Tubulin is a validated anticancer target, yet the clinical translation of colchicine-binding site inhibitors remains limited by toxicity and resistance. To accelerate the discovery of safer tubulin-targeting agents, we employed a machine learning (ML)-driven drug repurposing strategy integrating computational and experimental validation. Robust AutoQSAR classification models were trained on 279 curated tubulin inhibitors and used to screen 4500 US FDA-approved drugs, predicting 1800 compounds as potential tubulin inhibitors. These candidates were subjected to multistage structure-based virtual screening using Glide HTVS, SP, and XP docking, narrowing the selection from 698 (HTVS) and 350 (SP) to 38 compounds at the XP stage. Binding free-energy calculations (MM-GBSA) and 200 ns molecular dynamics simulations identified four stable colchicine-site binders: omeprazole, podofilox, sulfadoxine, and trimethoprim, exhibiting favourable binding energetics (Glide XP scores -10.06 to -8.12 kcal/mol; ΔG bind ranging from -10.06 to -8.12 kcal/mol; ΔG bind ranging from -64.16 to -38.61 kcal/mol). Biochemical tubulin polymerization assays confirmed tubulin inhibition, while cell-based cytotoxicity studies demonstrated low-micromolar antiproliferative activity of omeprazole and podofilox against melanoma (IC₅₀ = 4.32 ± 0.29 μM and 4.98 ± 0.37 μM, respectively) and colorectal cancer cells (IC₅₀ = 6.22 ± 0.22 μM and 5.76 ± 0.18 μM; n = 3). Overall, this study highlights a ML-guided drug repurposing framework that, unlike prior colchicine binding site-focused virtual screening studies, integrates large-scale ML prioritization with experimental validation to identify novel colchicine-site-targeted anticancer candidates.

Breast cancer brain metastasis (BCBM) remains a clinical challenge marked by limited therapeutic options and poor survival rates. Approximately 30% of all patients with metastatic breast cancer develop BCBM, with the highest incidence in patients with aggressive molecular subtypes, including triple-negative breast cancer (TNBC). Patients with TNBC with brain metastasis experience rapid disease progression and significantly reduced survival times due to a lack of targeted treatments that can penetrate the blood–brain barrier (BBB) and effectively control metastatic expansion. Current treatment options, such as whole-brain radiotherapy and chemotherapy, offer limited efficacy and are associated with significant toxicities, underscoring the urgent need for novel therapeutics that can target BCBM directly. We developed innovative colchicine binding site inhibitors (CBSI) targeting tubulin, SB-216 and SP-1-39, that show potent preclinical efficacy against brain and extracranial metastases in BCBM models. Both CBSIs cross the BBB, inhibit cell growth and migration, and induce apoptosis with low nanomolar potencies, similar to Azixa (MPC-6827), another CBSI previously evaluated in clinical trials. SB-216 reduced brain and concurrent extracranial metastases in a preventive dosing paradigm, extending overall survival. SB-216 also suppressed the expansion of preestablished brain lesions. In a taxane-refractory patient-derived TNBC model, SP-1-39 therapy markedly reduced brain and extracranial tumor burden. Together, these results highlight the promising therapeutic potential of SB-216 and SP-1-39 in treating taxane-sensitive or -resistant BCBM, filling a critical gap in TNBC management by offering targeted treatments that can cross the BBB and combat chemorefractory disease.