indication

Used in combination with cisplatin for the treatment of malignant pleural mesothelioma in adults whose disease is unresectable or who otherwise are not candidates for potentially curative surgery. Also used as a monotherapy for the treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC) after prior chemotherapy

pharmacology

Preclinical studies have shown that pemetrexed inhibits the in vitro growth of mesothelioma cell lines (MSTO-211H, NCI-H2052). Studies with the MSTO-211H mesothelioma cell line showed synergistic effects when pemetrexed was combined concurrently with cisplatin.

mechanism of action

Pemetrexed is an antifolate containing the pyrrolopyrimidine-based nucleus that exerts its antineoplastic activity by disrupting folate-dependent metabolic processes essential for cell replication. In vitro studies have shown that pemetrexed inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), all folate-dependent enzymes involved in the de novo biosynthesis of thymidine and purine nucleotides. Pemetrexed is transported into cells by both the reduced folate carrier and membrane folate binding protein transport systems. Once in the cell, pemetrexed is converted to polyglutamate forms by the enzyme folylpolyglutamate synthetase. The polyglutamate forms are retained in cells and are inhibitors of TS and GARFT. Polyglutamation is a time- and concentration-dependent process that occurs in tumor cells and, to a lesser extent, in normal tissues. Polyglutamated metabolites have an increased intracellular half-life resulting in prolonged drug action in malignant cells.

biotransformation

Metabolized by Cytochrome P450 Enzymes

half life

3.5 hours

route of elimination

Pemetrexed is not metabolized to an appreciable extent and is primarily eliminated in the urine, with 70% to 90% of the dose recovered unchanged within the first 24 hours following administration.

drug interactions

Ketoprofen: The NSAID, ketoprofen, may increase increase the serum concentration of pemetrexed by decreasing its renal clearance. Patients with mild to moderate renal insufficiency (CrCl 45-79 ml/min) should avoid use of ketoprofen within 2 days of a pemetrexed dose. Patients with better renal function do not appear to be at risk. Monitor for toxicity in all patients during concomitant therapy.

Sulindac: The NSAID, sulindac, may increase the serum concentration of pemetrexed by decreasing its elimination. This interaction more prevalent in patients with mild to moderate renal insufficiency. Consider alternate therapy or monitor for pemetrexed toxicity during concomitant therapy.

Tiaprofenic acid: Tiaprofenic acid may decrease Pemetrexed excretion. Tiaprofenic acid should not be used around the time when Pemetrexed is administered.

Tolmetin: Tolmetin may decrease the renal excretion of Pemetrexed in patients with decreased creatinine clearance. Tolmetin may be withheld in these patients from 2 days before to 2 days after Pemetrexed administration.