Tegafur

Absorption

Tegafur displays a dose-proportional pharmacokinetic properties. Tegafur is rapidly and well absorbed into the systemic circulation, reaching the peak plasma concentration within 1 to 2 hours of administration .

Toxicity

Oral LD50 value in rat, mouse and dog are 930mg/kg, 775mg/kg, and 34mg/kg, respectively . Continuous exposure to tegafur may cause physical defects in the developing embryo (teratogenesis).
Acute toxicity from the combination use of tegafur was associated with nausea, vomiting, diarrhoea, mucositis, gastrointestinal irritation, bleeding, bone marrow depression, and respiratory failure . Overdose may lead to fatal complications . In case of overdose, appropriate therapeutic and supportive medical interventions should be implemented.

Description

Tegafur is an orally bioavailable prodrug form of 5-fluorouracil (5-FU; ). It is converted to 5-FU in vivo enzymatically or by cytochrome P450 oxidation. Tegafur inhibits proliferation of HT-29, BxPC-3, and Panc02 cells (IC₅₀s = 201, 172, and 179 μM, respectively). It also reduces tumor growth in an HT-27 colon carcinoma mouse xenograft model when administered at a dose of 50 mg/kg and in a 4-1ST gastric carcinoma mouse xenograft model when used in combination with uracil. Formulations containing tegafur, in combination with uracil, have been used in the treatment of cancer.

Chemical properties

White Crystalline Powder

Originator

Futraful,Taiho,Japan,1974

The Uses of Tegafur

Isotope labelled Tegafur (T013900), used as an antineoplastic.

What are the applications of Application

Tegafur is a congener of fluorouracil

Background

Tegafur (INN, BAN, USAN) is a prodrug of Fluorouracil (5-FU), an antineoplastic agent used as the treatment of various cancers such as advanced gastric and colorectal cancers. It is a pyrimidine analogue used in combination therapies as an active chemotherapeutic agent in conjunction with Gimeracil and Oteracil, or along with Fluorouracil as Tegafur-uracil. Tegafur is usually given in combination with other drugs that enhance the bioavailability of the 5-FU by blocking the enzyme responsible for its degradation, or serves to limit the toxicity of 5-FU by ensuring high concentrations of 5-FU at a lower dose of tegafur . When converted and bioactivated to 5-FU, the drug mediates an anticancer activity by inhibiting thymidylate synthase (TS) during the pyrimidine pathway involved in DNA synthesis. 5-FU is listed on the World Health Organization's List of Essential Medicines.

Indications

Indicated for the treatment of cancer usually in combination with other biochemically modulating drugs.
Indicated in adults for the treatment of advanced gastric cancer when given in combination with Cisplatin .
Indicated for the first-line treatment of metastatic colorectal cancer with Uracil and calcium folinate .

Definition

ChEBI: Tegafur is an organohalogen compound and a member of pyrimidines.

Manufacturing Process

One process from US Patent 4,107,162: 27.4 g of 2,4-bis(trimethylsilyl)-5- fluorouracil and 7.7 g of 2,3-dihydrofuran are dissolved in 70 ml of acetonitrile, and 30 ml of an acetonitrile solution containing 1.3 g of anhydrous stannic chloride are added thereinto with cooling and stirring. 50 ml of acetonitrile containing 1.3 ml of water dissolved therein are then dropwise added over 15 minutes. After return to room temperature, the reaction is further effected with stirring at 40°C for 5 hours. The reaction mixture is neutralized by adding 1 N aqueous ammonia with cooling and stirring (conversion 83%). After the nondissolved substances are removed by filtration, the filtrate is concentrated and dried under reduced pressure. 100 ml of water and 300 ml of dichloromethane are added to the residue to completely dissolve the residue by stirring. The obtained dichloromethane layer is separated. The water layer is subjected to extraction twice with dichloromethane. The thus obtained extracts are combined with the separated dichloromethane layer and the combined extracts, after drying with anhydrous magnesium sulfate, are concentrated and dried. The obtained residue is dissolved in ethanol, and the nondissolved substances are removed by filtration. The filtrate is subjected to recrystallization to give white crystals, followed by further recrystallization of the mother liquor. There are totally obtained 15.6 g of N1-(2'-furanidyl)-5-fluorouracil.Yield: 78% of theory, with respect to 2,4-bis(trimethylsilyl)-5-fluorouracil.
An alternative process from US Patent 3,635,946: A vigorously stirred reaction mixture consisting of 32.87 g (0.1 mol) of 5-fluorouracilmercury, 100 ml of dimethylformamide and 50 ml of toluene is dried by azeotropic distillation of toluene. It is then cooled to -40°C in a stream of dry nitrogen, and a solution of 21.3 g (0.2 mol) of 2-chlorofuranidin in 20 ml of dried dimethylformamide is gradually added to the stirred mixture, the temperature being maintained between -40°C and -30°C. After completion of the reaction (which is marked by complete dissolution of the starting 5-fluorouracilmercury) i.e. after about 3 to 4 hours, 60 to 80 ml of the solvent are distilled off in vacuo at a bath temperature not exceeding 35°C. 50 to 70 ml of dry acetone are then added and also vacuum distilled. The residue is easily crystallized. It is collected, washed three times with small quantities of ethanol - 10 ml each - and airdried. 12.2 g of N1-(2'-furanidyl)-5-fluorouracil are obtained in the form of white crystalline solids; melting point 160°C to 162°C. Additional treatment of the mother liquor yields 3.0 g more of the product. Yield: 75% of theory, based on the starting 5-fluorouracilmercury.
After recrystallization from ethanol, 14.3 g of N1-(2'-furanidyl)-5- fluorouracilare obtained, MP 164°C to 165°C.

Therapeutic Function

Antineoplastic

Biochem/physiol Actions

Tegafur is a pro-drug of 5-fluorouracil, an antimetabolite used as an antineoplastic agent. It has been used as adjuvant chemotherapy for curatively resected colorectal cancer therapy.

Pharmacokinetics

Tegafur is an antineoplastic agent that belongs in the class of pyrimidine analogues. It interferes with the 2'-deoxythymidylate (DTMP) synthesis in the pyrimidine pathway, resulting in inhibition of DNA synthesis . In a phase III trial investigating the clinical efficacy of S-1 (tegafur/gimeracil/oteracil) in patients with advanced or recurrent gastric cancer, treatment resulted in a high response rate and was associated with a longer overall survival and longer progression-free survival rate when used in combination with cisplatin . In a meta analysis, triple combination therapy consisting of tegafur, gimeracil and oteracil showed longer survival times and well tolerance in patients with advanced gastric cancer . Tegafur and its active metabolites are potent myleosuppressive agents .

Safety Profile

Poison by ingestion. Moderately toxic to humans by intravenous route. Moderately toxic experimentally by intraperitoneal, intravenous, and subcutaneous routes. Experimental teratogenic data. Human systemic effects: nausea and vomiting. Experimental reproductive effects. Questionable human carcinogen producing gastrointestinal tumors. Human mutation data reported. Used as an anti-cancer agent. When heated to decomposition it emits very toxic fumes of Fand NOx.

Metabolism

Hepatic CYP2A6 is the predominant enzyme that mediates 5-hydroxylation of tegafur to generate 5'-hydroxytegafur. This metabolite is unstable and undergoes spontaneous degradation to form 5-FU, which is an active antineoplastic agent that exerts a pharmacological action on tumours. 5-FU is rapidly metabolised by the liver enzyme dihydropyrimidine dehydrogenase (DPD) .