Amitivir [LY217896], an amino thiadiazole derivative, is an inhibitor of the enzyme inosine monophosphate dehydrogenase. Amitivir has activity against several influenza A and B viruses. Amitivir possesses broad antiviral activity in vitro and in animal models against or thomyxo-and paramyxoviruses. In phase I studies with healthy volunteers, single doses of up to 500 mg were well tolerated and had predictable pharmacokinetics. Oral LY217896 was in trial for prevention of experimental influenza A virus infection and illness in humans. LY217896 was associated with asymptomatic rises in serum uric acid levels and was ineffective in modifying the virologic or clinical course of experimental influenza A (H1N1) virus infection. Amitivir development was discontinued.