Phase I trials of pemetrexed

The maximum tolerated dose of the multitargeted antifolate drug pemetrexed is 600 mg/m² every 3 weeks in heavily pretreated patients without folic acid supplementation. However, with folic acid supplementation, higher doses have been given without limiting side effects. The dose-limiting toxicities of pemetrexed are neutropenia, asthenia, and thrombocytopenia. Other adverse effects include anemia, anorexia, rash, nausea, vomiting, peripheral edema, diarrhea, mucositis, and reversible elevations of transaminase and creatinine levels. Multiple pemetrexed combination phase I trials have been completed or are underway. Without folic acid supplementation, pemetrexed doses of 400 to 600 mg/m² could be safely administered with full therapeutic doses of irinotecan, gemcitabine, cisplatin, carboplatin, oxaliplatin, and 5-fluorouracil. Preliminary data from other ongoing trials (with folic acid and vitamin B₁₂ supplementation) have similarly shown that pemetrexed doses of at least 400 to 500 mg/m² an be safely administered with therapeutic doses of vinorelbine, docetaxel, and paclitaxel. Combination studies of pemetrexed with agents active in breast cancer (doxorubicin, epirubicin, and cyclophosphamide) and chest radiotherapy are also now underway. Adverse effects of these combinations have included neutropenia, anemia, thrombocytopenia, asthenia, vomiting, diarrhea, rash, nausea, anorexia, mucositis, and reversible transaminase elevation. The phase I trials of pemetrexed have consistently shown activity against a broad range of tumor types, including colorectal cancer, pancreatic cancer, breast cancer, non-small cell lung cancer, and mesothelioma. This activity has been noted not only in the combination trials, but when pemetrexed is given as a single agent as well. Pemetrexed is a promising drug. It is active against a broad range of cancers, and it has manageable side effects that seem to be lessened with folic acid and vitamin B₁₂ supplementation.