Plicamycin is presumed to inhibit cellular and enzymic RNA synthesis by forming a complex with DNA. Plicamycin may also lower calcium serum levels by inhibiting the effect of parathyroid hormone upon osteoclasts or by blocking the hypercalcemic action of pharmacologic doses of vitamin D.
Plicamycin is lethal to Hela cells in 48 hours at concentrations as low as 0.5 micrograms per milliliter of tissue culture medium. Plicamycin has shown significant anti-tumor activity against experimental leukemia in mice when administered intraperitoneally.
The most important form of toxicity associated with the use of plicamycin consists of a dose-related bleeding syndrome which usually begins with an episode of epistaxis. Plicamycin crosses the blood-brain barrier; the concentration found in brain tissue is low but it persists longer than in other tissues.