DRUG REPURPOSING IN ONCOLOGY:OPPORTUNITIES,CHALLENGES AND FUTURE PERSPECTIVES

Drug repurposing, also known as drug repositioning, is an emerging strategy that involves identifying new therapeutic applications for existing drugs originally developed or approved for other diseases. In oncology, drug repurposing has gained considerable interest because conventional anticancer drug development is associated with high cost, long development timelines, treatment-related toxicity, and a high risk of failure. Existing drugs have established pharmacological, pharmacokinetic, safety, and manufacturing information, which may facilitate their evaluation for new cancer indications. Repurposed drugs may exert anticancer effects through multiple mechanisms, including inhibition of cancer-cell proliferation, induction of apoptosis, modulation of cancer metabolism, inhibition of autophagy and angiogenesis, immune modulation, alteration of the tumor microenvironment, and inhibition of invasion and metastasis. Several drugs, including metformin, statins, aspirin, propranolol, doxycycline, hydroxychloroquine, and antimalarial agents, have been investigated for potential anticancer applications. Drug repurposing may also support combination therapy with chemotherapy, targeted therapy, hormonal therapy, immunotherapy, or radiotherapy, as well as precision oncology approaches based on molecular characteristics of individual tumors. Computational approaches, network pharmacology, molecular docking, multi-omics, artificial intelligence, and machine learning can further assist in identifying and prioritizing promising candidates. However, challenges such as appropriate anticancer dosing, toxicity, tumor heterogeneity, drug interactions, limited clinical evidence, and inconsistent clinical outcomes remain. Therefore, well-designed preclinical studies and clinical trials are essential to establish efficacy, safety, optimal dosing, and appropriate patient selection. Overall, drug repurposing represents a complementary and potentially cost-effective approach to conventional cancer drug discovery and may contribute to the development of more personalized and combination-based cancer therapies.