a substance being studied in the treatment of cancer. it is made from an antibiotic called geldanamycin. 17-aag helps cause the breakdown of certain proteins in the cell, and may kill cancer cells. it is a type of antineoplastic antibiotic and a type of hsp90 inhibitor. also called 17-n-allylamino-17-demethoxygeldanamycin and tanespimycin.