A semisynthetic derivative of podophyllotoxin that exhibits antitumor activity. teniposide inhibits dna synthesis by forming a complex with topoisomerase II and dna. This complex induces breaks in double stranded dna and prevents repair by topoisomerase II binding. Accumulated breaks in dna prevent cells from entering into the mitotic phase of the cell cycle, and lead to cell death. teniposide acts primarily in the G2 and S phases of the cycle.