Dexelvucitabine is a cytidine analogue, which has been shown to be active in both naive and HIV-experienced individuals and has in vitro activity against a variety of NRTI-resistant strains. Dexelvucitabine belongs to a class of HIV drugs called nucleoside reverse transcriptaseinhibitors (NRTIs). In the Phase IIb study most side effects were generally mild and included headache, fatigue, and gastrointestinal disorders. However, some participants developed severe hyperlipasemia and pancreatitis. Drug development is discontinued due to 40% incidence of grade 4 hyperlipasemia including one case of pancreatitis.