These drugs are undergoing study because a suitable dose and schedule has been found in Phase I trials. Phase II studies are trying to establish the drugs' effectiveness, usually in a wide range of tumor types. Several drugs already show promise against certain types of cancer, but this information is very preliminary.

Gemcitabine (difluorodeoxycytidine) is an antimetabolite introduced by Lilly Laboratories. It has shown encouraging activity—20 percent or more responses (temporary tumor shrinkage)—in lung, ovarian and breast cancers. Some patients with pancreatic cancer have also shown improvement, although objective responses will likely not exceed 10 percent of patients even when they have been given no treatment before.
    The toxicity profile is quite favorable. The drug has mild effects on the bone marrow . Short-term skin rashes and flu-like symptoms are the most commonly observed side effects.

Irinotecan (CPT-11) is a Japanese drug that shows activity against a large number of tumor types, with or without exposure to other drugs. It is in the family of camptothecin derivatives. Toxicities include decreased white blood cell and platelet counts, diarrhea, hair loss, anemia , nausea and vomiting. There have been responses in patients with lung cancer, colon and other gastrointestinal cancers, gynecologic cancers and lymphomas and leukemias. Very active combinations are also being reported. Wide testing of these leads, sponsored by the NCI, is expected in the United States.