Alovudine (3'-fluoro-3'-deoxythymidine, FLT) is a synthetic nucleoside analog primarily utilized in medical research for antiviral applications, particularly against HIV. It acts as a reverse transcriptase inhibitor, interfering with viral replication by incorporating into viral DNA and causing chain termination. While preclinical studies demonstrated potent anti-HIV activity, clinical development was halted due to significant toxicity concerns, including bone marrow suppression, and the rise of more effective, less toxic antiretrovirals. As a research reagent, Alovudine is valuable for studying nucleoside analog mechanisms, viral resistance, and potential repurposing for other viruses like HBV or in oncology imaging (as [18F]-FLT for PET scans).