150399-23-8

Crystalline Solid

Eli Lilly (US)

Multitargeted antifolate; inhibits thymidylate synthase as well as other folate dependent enzymes. Antineoplastic

Pemetrexed is a novel antifolate and antimetabolite for TS, DHFR and GARFT with Ki of 1.3 nM, 7.2 nM and 65 nM, respectively

ChEBI: An organic sodium salt that is the disodium salt of N-{4-[2-(2-amino-4-oxo-4,7-dihydro-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl}-L-glutamic acid. Inhibits thymidylate synthase (TS), 4 1 dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT).

Alimta (Lilly).

The drug is available in a 100-mg sterile vial for IV use. Thedrug appears to be effective against a range of tumors includingmesothelioma, NSCLC, colorectal cancer, bladdercancer, and lung cancer. The mechanism of action involvesinhibition of TS resulting in inhibition of thymidylate andDNA synthesis. This drug is a pyrrolopyrimidine analog offolate with antifolate activity. Resistance can occur by increasedexpression of TS, decreased binding affinity for TS,or decreased drug transport into cells. The drug is administeredonly via the IV route and distributes to all tissues.Cellular activation to the more potent polyglutamated formsoccurs, and the majority of the dose is excreted unchangedin the urine. The drug interaction and toxicity profiles aresimilar to that of methotrexate.

Like methotrexate, it is actively transported into tumor cells through reduced folate carriers and, in polyglutamated form, inhibits the synthesis of pyrimidine and purine-based nucletotides by disrupting folatedependent metabolic processes . In addition to DHFR, this pyrrolopyrimidine-based inhibitor binds tightly to thymidylate synthase and GAR transformylase.

Pemetrexed is a novel multitarget antifolate used by the IV route for the treatment of advanced or metastatic nonsmall cell lung cancer and in combination with cisplatin in malignant pleural mesothelioma.

Patients on pemetrexed must take folate and vitamin B12 supplements to reduce the risk of bone marrow suppression (neutropenia, thrombocytopenia, and anemia) and GI side effects. Pretreatment with corticosteroids can reduce the risk of drug-induced skin rash. Pemetrexed has a half-life of 3.5 hours and is excreted primarily unchanged via the kidneys. Significant cross-resistance has been noted between pemetrexed and other pyrimidine and folate antagonists.

A number of papers outlining the syntheses of pemetrexed and related analogs have appeared. A practical and scalable synthetic route is depicted in Scheme 9. Palladium (0) coupling of methyl 4-bromobenzoate (57) with 3-butyn-1-ol (58) gave crystalline 59, which was then reduced over palladium on carbon in DCM to give alcohol 60. Filtration of the catalyst afforded a DCM solution of alcohol 60, which was utilized directly in a TEMPO-catalyzed sodium hypochlorite oxidation, providing known aldehyde 61 without isolation. Addition of 5,5-dibromobarbituric acid (DBBA) and catalytic amount of HBr in acetic acid to the DCM solution of 61 effected the conversion to a-bromoaldehyde 62. After aqueous work-up, the solution was concentrated and diluted with acetonitrile to exchange solvents. Addition of commercially available 2,4-diamino-6-hydroxypyrimidine (63), aqueous sodium acetate and heating to 45??C resulted in cyclic condensation and precipitation of pyrrolo[2,3- d]pyrimidine 64 from the reaction mixture in 67% yield based on 60. Saponification of 64 with aqueous sodium hydroxide followed by acidification afforded the carboxylic acid derivative 65, which was elaborated to 66 by chlorodimethoxytriazine active ester coupling method. Reaction of 65 with 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) in the presence of N-methylmorpholine in DMF solution followed by reaction of the resulting dimethoxy-s-triazinyl ester with diethyl L-glutamate afforded crude 66, which was isolated via crystallization as pTSA salt 67. Saponification of 67 with aqueous sodium hydroxide followed by acidification with HCl gave pemetrexed as the free acid, which was crystallized as disodium salt form.

MEK | ERK

Potentially hazardous interactions with other drugs
Antimalarials: antifolate effect increased by pyrimethamine.
Antipsychotics: avoid with clozapine, increased risk of agranulocytosis.
Nephrotoxic agents: may reduce clearance of pemetrexed - use with caution.
Live vaccines: avoid use; YELLOW FEVER VACCINE ABSOLUTELY CONTRAINDICATED.

Pemetrexed undergoes minimal hepatic metabolism, and about 70-90% of a dose is eliminated unchanged in the urine within 24 hours. In vitro studies indicate that pemetrexed is actively secreted by OAT3 (organic anion transporter).