(organic chemistry) A dark red crystalline substance, isomeric with and resembling indigo blue, and obtained from isatide and dioxindol.

(pharmacology) An antiretroviral drug C₃₆H₄₇N₅O₄ of the protease inhibitor class that is used in the form of its sulfate in combination with antiretroviral drugs (such as zidovudine) to treat HIV infected patients.