Preclinical and clinical studies with combinations of pemetrexed and gemcitabine.

The novel antimetabolite pemetrexed inhibits the folate-dependent enzymes thymidylate synthase, dihydrofolate reductase, and glycinamide ribonucleotide formyltransferase. This agent is broadly active in a wide variety of solid tumors, including non-small cell lung, breast, bladder, head and neck, and ovarian cancers, as well as mesothelioma. Gemcitabine is a pyrimidine nucleoside antimetabolite that is approved worldwide for the treatment of pancreatic and non-small cell lung cancers, and bladder cancer outside the United States. In addition, gemcitabine is active against a broad range of tumors including breast, ovarian, and other cancers. Preclinical studies have shown cytotoxic synergy when pemetrexed is combined with gemcitabine. Based on these data, a phase I study of this combination was performed that showed striking activity. Phase II studies of this combination are being performed in breast and non-small cell lung cancer. In addition, a phase III study in pancreatic cancer is ongoing.