A chemotherapeutic agent, used to treat Kaposi's sarcoma, cancer, and persistent warts, among other things.
Bleomycin causes lung damage, so I think it was one of the drugs that Lance Armstrong didn't use for his chemotherapy, because he didn't want to compromise his athletic ability.
It's a drug, but not the pleasant kind. It's a poison. It just kills cancer and warts a little faster than the rest of you.