Indinavir is an antiviral drug that treats HIV, acting as a protease inhibitor; this compound also exhibits anti-diabetic and anticancer chemotherapeutic activities. Like other antivirals, indinavir also exerts effects on insulin resistance and glucose tolerance. In vitro, indinavir decreases phosphorylation of the insulin receptor β subunit, inhibits the GLUT4 glucose transporter, and decreases levels of the insulin receptor, sterol regulatory element binding protein 1 (SREBP1), and PPAR-γ, impairing adipocyte function and altering insulin sensitivity. In diabetic rats, indinavir increases glucose tolerance and hyperglycemia, potentially though induction of the suppressor of cytokine signaling 1 (SOCS1) signaling cascade. Indinavir may also exhibit chemotherapeutic potential, as it inhibits adenocarcinoma tumor growth in vivo; this activity may be dependent on inhibition of matrix metalloproteinases. Additionally, indinavir inhibits multiple isotypes of calpain, preventing apoptosis in cellular models.