The evolving role of pemetrexed (Alimta) in lung cancer

Pemetrexed (Alimta; Eli Lilly and Co, Indianapolis, IN) is a multitargeted antifolate that inhibits several folate-dependent enzymes that play roles in purine and pyrimidine synthesis. The principal toxicities of pemetrexed are neutropenia, diarrhea, nausea/vomiting, mucositis, and skin rash. These toxicities are more frequent in vitamin-deficient (folate and vitamin B12) patients, and can be ameliorated by the co-administration of folate and vitamin B12. The use of prophylactic dexamethasone is also recommended to reduce the frequency of severe skin rash. Pemetrexed has significant single-agent activity in previously treated and untreated patients with non-small cell lung cancer (NSCLC). A recent phase III trial comparing pemetrexed with docetaxel in previously treated NSCLC patients showed equivalent efficacy with less bone marrow toxicity (eg, neutropenia) in the pemetrexed group. These results were pivotal in the approval of pemetrexed for the treatment of refractory NSCLC. Pemetrexed has been combined with the platinums (ie, cisplatin, carboplatin, and oxaliplatin) in NSCLC to yield clinical activity similar to that of other platinum-based doublets. A comparative phase III trial of cisplatin/pemetrexed against cisplatin/gemcitabine (Gemzar; Eli Lilly and Co) is under way. Pemetrexed has also been evaluated in combination with gemcitabine, and although the optimal dose and schedule of this combination has not been defined, clinical activity similar to other nonplatinum-based doublets has been observed. Preliminary evidence suggests that pemetrexed can be combined with thoracic radiation therapy, but more data are needed to evaluate the potential advantage(s) pemetrexed may have in this setting. Pemetrexed/platinum doublets also appear to possess activity in extensive stage small cell lung cancer. A phase II trial of single-agent pemetrexed is under way in both sensitive- and refractory-relapsed small cell lung cancer. Given the activity and excellent tolerability of pemetrexed, further studies in lung cancer are warranted.