Ophiobolin A is a fungal metabolite, toxic to many crops and found to have antimicrobial and anticancer activity. Ophiobolin A is a calmodulin antagonist and inhibitor of big conductance Ca2+-activated K+ channel (BKCa) activity. Its anticancer activity may involve inhibition of multiple oncogenic signaling pathways including PI3K/mTOR, Ras/Raf/ERK and CDK/RB. One study suggested the possibility of pyrrolylation of lysine residues on its intracellular target protein(s) as a mechanism of action on various targets.