IE83480B1 - Uracil reductase inactivator - Google Patents

Description

URACIL REDUCTASE INACTIVATOR The present invention relates to certain enzyme inactivators which are useful in medicine, particularly cancer chemotherapy, especially in combination with antimetabo1ite antineoplastic agents such as -flnorouracil (5-FU).

-Fluorouracil has been used in cancer chemotherapy since 1957. Sensitive tumours include breast cancer, . gastrointestinal malignancies, and cancers of‘ the head and- neck; 5-fluorouracil is also used as a radiation ‘ sensitiser. 5—F1uorouracil is metabolised rapidly in the liver (half life between about 8 and 20 minutes) by the enzyme dihydropyrimidine dehydrogenase (uracil it- reductase). It has been reported (cancer Research 46, 1094, 1986) that 5-(2-bromovinyl)-uracil (BVU) is an inhibitor of dihydrothymidine dehydrogenase which both retards the metabolism of 5-fluorouracil and enhances its antitumour activity. It has been reported that’ —(2-bromovinyl)-2’-deoxyuridine (which is metabclised in 3339 to BVU) enhances the antitumour activity of Ssfluorouracil and 5—deoxyfluorouridine, a prodrug of -fluorouracil (Biochemical Pharmacology 38: 2885,'f1989)).

Unfortunately BVU is toxic to humans. it has now been discovered that 5-ethynyluracil is an inactivator of uracil reductase; it increases the level and half life of 5—fluorouraci1 in plasma and enhances the activity of 5-fluorouracil. It also reduces the normally encountered variations of 5-fluorouracil plasma levels between subjects.

Accordingly, in a first aspect, the present invention provides a uracil reductase inactivator which is 5%fihynyhnaCi1 for use iJ1 medicine, particularly for use iJ1 cancer The uracil reductase inactivator will generally in conjunction with 5-fluorouracil or a prodrug chemotherapy. be used thereof.

In a further aspect, the present invention provides a uracil derivative as hereinbefore defined for use in the manufacture of a medicament for use in cancer chemotherapy. The medicament may also be useful for rescue from 5-fluorouracil toxicity; and together with thereof for the -fluorouracil or a prodrug treatment of psoriasis or rheumatoid arthritis, or human papilloma virus infections.

In a yet further aspect, the present invention provides a combination of 5—ethynyluracil and 5-fluorouracil or a prodrug thereof.

Prodrugs of 5-fluorouracil (5-EU) are compounds which are metabolised in vivo to 5-fluorouracil and include 5- fluorouridine, 5-fluoro—2—deoxyuridine, 5-fluoro—2— deoxycytidine, 5’—deoxy-4',5-fluorouridine, 5'-deoxy—5- fluorouridine, 1-(2—tetrahydrofuranyl)—5—fluorouracil and 1‘Cpa allcylcarbamoylfluorouracil derivatives.

-FU or a prodrug thereof and 5-ethynyluracil may be employed with the of the combination to an in combination in accordance invention by administration of the components appropriate subject either concomitantly, for example in a unitary pharmaceutical formulation; or, more preferably, separately or sequentially within a sufficient time period whereby the desired therapeutic effect of the combination is achieved. Preferably 5—ethynyluracil is administered first and 5—FU or a prodrug thereof administered subsequently, advantageously fronx 15 mins to four days, usually 1. to 15 hours, especially 1 to 2 hours thereafter.

-FU or a prodrug thereof ‘and 5-ethynylu nacil may be administered respectively for therapy by any suitable route including oral, rectal, nasal, topical (including buccal and sublingual), vaginal and parenteral (including subcutaneous, intramuscular, intravenous and intradermal). It will be appreciated that the preferred ‘route will vary with the condition and age of the recipient, the nature of the infection and other clinical factors.

Hitherto it has not been viable to administer 5-FU orally, as it is destroyed by uracil reductase in the gastro—intestinal tract. However, it has now been found that if 5-ethynyluracil is administered prior to oral administration of 5-FU (or a prodrug thereof), high and persistent levels of 5-FU are obtained in the plasma, indicating that this compound is not being destroyed.

This is a further advantage of the present invention.

Preferably the 5-FU is administered within 15 mins to four days, usually 1 to 15 hours, especially 1—to 2 hours of the 5-uracil derivative.

Normally, patients exhibit a high degree of variability in.

-FU plasma concentrations resulting from a given 5-FU dosage, which may be due to rates of 5-FU elimination which differ from patient to patient. There may also be diurnal variations within individual patients. The use of the 5-substituted uracil derivative according to the present invention is found to markedly reduce this subject-to-subject variability (see Experiment 3).

In general a suitable dose of 5-FU or a prodrug thereof will be in the range of 0.1 to 1000 mg per kilogram body weight of the recipient per day, preferably in the range of 0.1 to 200 mg per kilogram body,weight per day. If O- -FU itself is administered the dose is preferably in the range of 0.1 to 50 mg per kilogram body weight per day but ,higher doses of prodrugs of 5-FU may be administered. The dose of 5-FU or prodrug thereof may be administered in unit dosage forms, for example, containing 5 to 3000 mg, ‘preferably 20 to 1000 mg, active ingredient per unit dosage form.

Experiments with 5-FU suggest that a dose should be administered to achieve peak plasma concentrations of the active compound of from about 0.01 to about 1.5 ug/ml.

?S—ethyny1uraci1_ may be administered in a dosage in the range of 0.01 to 50 mg per kilogram body weight of the recipient per day, particularly 0.01 to 10 mg/kg. The dose is more preferably in the range of 0.01 to 0.4 mg per kilogram body weight per day, depending on the derivative used. An alternative preferred administration regime is 0.5 to 10 mg/kg once per week.

The desired dose is preferably presented as one, two or more sub-doses administered at appropriate intervals throughout the day. These sub-doses may be administered in unit dosage forms for example containing 1 to 200 mg preferably 2 to 100 mg, more preferably 2 to 50 mg, of the -uracil derivative.’ ‘ The uracil reductase inactivator and the 5-FU are usuallyi employed in an appropriate ratio to substantially reduce the natural subsisting uracil reductase level in the subject. Such a ratio based on the respective weights of ‘uracil reductase inactivator and 5-FU is generally in the range 1:0.01 to 1:100, preferably in the range 1:0.1 to 1:50, and particularly in the range 1:1 to 1:10.

-FU or prodrug thereof and the 5-uracil derivative are preferably administered in a pharmaceutical formulation, either in a single pharmaceutical formulation containing both components or in separate administrations each containing one of the components of the combinations. '5-ethynyduratil‘wit1 potentiate SLFU so that lower doses of 5-FU will be employed.

Tfie present invention thus includes as a further feature a:pharmaceutica1 formulation comprising 5-ethynyluracil optionally in combination with 5-FU be a prodrug thereof together with at least one pharmaceutically acceptable carrier or excipient.

Each carrier must be "pharmaceutically acceptable" in the sense of being compatible with the other ingredients of the formulation and not injurious to the patient.

Formulations include those adapted for oral, rectal, nasal, topical (including buccal and sublingual), vaginal and parenteral (including subcutaneous, intramuscular, intravenous and intradermal) administration. The formulations may conveniently be presented in unit dosage form and may be prepared by any methods well known in the art of pharmacy. such methods include the step of bringing into association the active ingredient with the carrier which constitutes one or more accessory ‘ ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the » active ingredient with liquid carriers or finely divided solid carriers or both, and then if necessary shaping the product. N Formulations of the present invention adapted for oral administration may he presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient; as a powder or granules: as a solution or a suspension in an aqueous or non-aqueous liquid; or as an oil-in—water liquid emulsion or a water-in-oil liquid emulsion. The active ingredient may also be presented as-a bolus electuary or paste. Oral administration is the preferred I route.

A tablet may be made by compression or moulding, optionally with one or more accessory ingredients.

Compressed tablets may be prepared by compressing in a suitable machine the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder (e.g. povidone, gelatin, _ hydroxypropylmethylcellulose), lubricant, inert diluent, preservative, disintegrant (eg. sodium starch glycollate, cross-linked povidone, cross-linked sodium caroxymethylcellulose) surface-active or dispersing agent.

Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with’ an inert liquid diluent. The tablets may optionally be" coated or scored and may be formulated so as to provide controlled release of the active ingredient therein using, for example, hydroxypropylmethylcellulose in varying proportions to provide the desired release profile.

Formulations for topical administration in the mouth include lozenges comprising the active ingredient in a flavoured basis, usually sucrose and acacia or tragacanth; pastilles comprising the active ingredient in an inert basis such as gelatin and glycerin, or sucrose and acacia; and mouthwashes comprising the active ingredient in a suitable liquid carrier.

Formulations for rectal administration may be presented as a suppository with a suitable base comprising for example cocoa butter or a salicylate.

Formulation for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations containing in addition to the active ingredient such carriers as are known in the art to be appropriate. ' Formulations for parenteral administration include aqueous and non—aqueous isotonic sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non—aqueous sterile suspensions which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored inla freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use.

Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the kind previously described.

Liquid formulations including dissolved 5-uracil derivative are preferably buffered to a pH of 7 to ll, generally 9.5 to 10.5. Preferred unit dosage formulations are those containing a daily dose or unit, daily sub-dose, as hereinabove recited, or an appropriate fraction thereof, of an-active ingredient. -ethynyluracil which is employed in combination with 5- fluorouracil or a prodrug thereof in accordance with the present invention may be prepared in conventional manner. For example, the inactivators referred to above may be prepared by the methods described in J.

Heterocycl. Chem. 19(3) 463-4 (1982) for the preparation of 5-ethynyluracil.

Example 1 (5—ethynyluracil (EU)) (a) 5 — (trimethylsilylethynyl)uracil A solution of 5 - iodouracil (8g, 30mmol) in redistilled triethylamine (500m1) and dry DMF (10m1) was degassed with oxygen free nitrogen for 15 minutes, Bis (triphenylophosphine)palladium (II) chloride (O.5g), copper (I) iodide (O.5g) and trimethylsilylacetylene (log, 102mol) were then added and the mixture was heated with stirring at 50°C for 24 hours, The eooled reaction mixture was filtered, the filtrate evaporated to dryness and the residue dissolved in dichloromethane (500mL). The _organic solution was washed with a 2% aqueous solution of disodium EDTA (3 x 250mL), water (3 x 200mL), dried (Na2SO4) and evaporated to dryness. The residue was triturated with ethanol to give the first crop of the title compound. The solid filtered from the reaction mixture was also found to contain the required product but in a more impure form and so was worked up as above in a‘ separate batch to give a second crop.

H nmr & (d5DMSO) 11.75-10.35 (2H, bs, NH), 7.75 (1H, s, H-6), 0.15ppm (9H, m, SiCH3). (b) 5—Ethynyluracil A solution of 5-(trimethylsilylethynyl)uracil (5.39, 24.4mmol) in 0.2M solution of sodium methoxide in methanol (400 mL) was stirred at room temperature for 3 hours and neutralized to pH 7 with dilute hydrochloric acid. The precipitated product was filtered, washed with methanol and dried to give a first crop of the title compound. The filtrates and washings were combined, evaporated to dryness and the residue crystallised from methanol to give the second crop of product. Combination of both crops and a further recrystallisation from ethanol gave a pure product.‘ M.pt. : 260°C (dec.) H nmr & (d5DMSO) 11.6-10.8 (2H, bs, NB), 7.3 (1H, s, H-6), 4.03 ppm (1H, s, acetylenic H) A Microanalysis calculated for C5H4N202 : C, 52.95: H, 2.96; N, 20.58 ‘ Found : C, 52.04; H, 2.92: N, 20.3 ' Example 2 (5—ethynyluracil) a) QLA—Dimethoxyiodo-pyrimidine_ A dry 1L round—bottomed flask was charged with -iodouracil (50 g, 0.21 mol), phosphorus oxychloride (300 ml), and N,N-diethylaniline (6 drops). The heterogenous mixture was heated in a 120°C oil bath under a nitrogen atmosphere for 24 hours. The phosphorus oxychloride was distilled off (some product-co-distills off). The reaction solution was next slowly and cautiously poured over ice (1L) and solid sodium bicarbonate keeping the internal temperature at or below -20°C. (This was accomplished by cooling in a dry-ice acetone bath). Once the addition was complete, the reaction mixture was adjusted to pH 7 by addition of solid sodium bicarbonate.

The mixture was extracted with methylene chloride and the organic fractions dried by passage through phase separator paper. The crude solution of 2,4-dichloroiodopyrimidine was immediately added dropwise to a-solution containing Me0H (400 ml) and sodium methoxide (28.3 g, 0.533 mol). This addition took 1 hour. The reaction was then stirred at room temperature overnight. The solution was neutralized with Co2(gas), extracted with methylene chloride, dried over anhydrous Na2SO4, filtered and concentrated. The crude product was adsorbed onto silica gel (100 g) and loaded onto a 400 g silica gel flash chromatography column. The column was eluted with 90:10 hexanes: ethyl acetate (v:v). The appropriate fractions were combined and concentrated to a white solid as the title compound.

Yield 26.7 g (48%) ZOOMHZ Nmm cnc13 a=3.97 (s, 3H); 4.02 (s, 3H), 3.43 (s,lH). h) g,4-Dimethoxy(b-trimethylsilyl)-ethynylpyrimidine A dry 1L round-bottomed flask under a nitrogen atmosphere was charged with the product of stage a) (26.7 g, 0.10 mol), dry methylene chloride (Aldrich, 150 mL), dry Et3N (freshly distilled from KOH pellets, 250 mL). The system was evacuated and purged with nitrogen several times via a Firestone valve. Trimethylsilylacetylene (21.2 mL, .15 mol: Aldrich) was added by syringe. Next were added his(triphenylphosphine)palladium (II) chloride (Aldrich .84 g, 8.32 mmol) and copper (I) iodide (Aldrich 4.76'g, mmol). The mixture was heated in a 60°C oil bath for 2 hours, cooled and filtered through Celite. The filtrate was concentrated in ggggg. The residue was diluted with toluene (100 mL) and then the toluene was removed ig vacuo. The residue was taken up into methylene chloride (200 mL), filtered and the filtrate extracted with 5% aq. ethylenediaminetetraacetic acid, disodium salt dihydrate (3 x 100 mL Aldrich), H20 (1 x 100 mL). The organic layer was dried via passage through phase separator paper and concentrated ig 33939. The product was purified on a Waters Prep 500 eluting with 95:5 hexanes: ethyl acetate (v:v). The crude product was adsorbed onto 100 g of silica gel and loaded onto a 400 g silica gel flash chromatography column. The column was eluted with 97.5:2.5 hexanes: ethyl acetate (v:v). The appropriate fractions were combined and concentrated.

Yield 16.94 g (73%).

A 1.2 g sample of the resulting compound was bound to 6 g of silica gel and loaded onto a.50 g flash chromatography column. The column was eluted with hexanes: ethyl acetate 95:5 (v:v). The appropriate fractions were combined, concentrated, stripped with CHZCI2 (2 x 30 mL), and drieéi in vacuo to yield 1.000 g of the title compound, m.p. 72.5-73°C 1 Lit. m.p. 73-74°C J. Heterocyclic Chem., 19, 463‘(1982).; c) 5-(b-trimethylsilyl)ethynyluracil A dry 3-necked round—bottomed flask under nitrogen wa charged with ' 2,4-dimethoxy—5-(b-trimethylsilyl)ethynylpyrimidine (6.5 g, 27.5 mmol), dry acetonitrile (120 mL Aldrich), sodium iodide (oven dried in ygggg 80°C, 18 h, 12.4 g, 82.7 mmol) and chlorotrimethylsilane (10.5 mL, 82.7 mmol freshly distilled). The mixture was heated at reflux for 3 hours and then concentrated in vacuo. The residue was digested with a solution containing methanol (40 mL) and water ( (20 mL) and the product filtered off to give 1.48 g (26%). The product was dissolved in chloroform and the solution adsorbed onto silica gel 7 g) which was then loaded onto a 35 g silica gel flash chromatography column. Elution with chloroform:methanol 95:5 (y:v) followed by chloroform:methanol 90:10 (v:v) and evaporation of the product-containing fractions yielded 1.23 g of the title compound as a white solid. d) 5-Ethynyluracil A solution containing 5-(b-trimethylsilyl)ethynyluracil (3.85 g, 18.4 mmol) and methanol (370 mL) was treated with _a second solution containing sodium hydroxide (2.3 g, 57.5 mmol) and water (18mL). The mixture was stirred at room temperature for 2 hours and then concentrated in vacuo. The residue was suspended in water (35 mL) and the pH adjusted to using 0.1 N HCl. The solids dissolved and then a second precipitate formed when the pH=5. The product was filtered, washed with H53, and then dried in vacuo to give 2.3 g (92%) of —ethynyluracil as a light beige powder.

Microanalysis calculated for CJuNgh: C, 52.95: H, N, 20.58 Found: C, 52.79; H, 3.02; N, 20.44 .96; The following Examples illustrate pharmaceutical formulations in which the "Active ethynyluracil or Ingredient" is 5—propynyluracil, 5- reductase inactivator as mentioned above; or mixtures thereof with 5-fluorouracil. other uracil Tablet Formulations ____________________ The following formulations 5A, 5B and 5C are prepared by wet granulation of the ingredients (except the magnesium stearate) with a solution, of the povidone followed tar drying of the granules, addition of the magnesium stearate and compression.

Formulation 5A mg/tablet mg/tablet Active ingredient 5 2 Lactose, B.P. 205 75 Povidone, B.P. 15 10 Sodium starch glycollate 20 10 Magnesium stearate 5 3 Formulation SB ' mggtablet mggtablet ' 250 so Formulation SC I mggtablet Active ingredient 5 Lactose, B.P. 205 Starch -. 50 Povidone, B.P. 6 Magnesium stearate The following formulation SD was prepared by direct compression of the admixed ingredients. The lactose used is of the direct compression type.

Formulation 5D m tablet Active ingredient 5 Lactose 155 Avicel PH 101 100 ' 260 The following formulation SE is a controlled release tablet and is prepared by wet granulation of the ingredients (except magnesium stearate) with a solution of the povidone, followed by drying of the granules, addition of the magnesium stearatg and compression.

Formulation SE mg(tab1et Active ingredient ‘ 5 Hydroxypropylmethylcellulose 110 (uethocel K4M Premium) Lactose, B.P. 50 Povidone, B.P. 28 Magnesium stearate __Z_ _ _ 200‘ Example 4 Capsule Formulations The following formulations 6A and 6B are prepared by admixing the uncompressed ingredients and filling into a two—part hard gelatin capsule.

Formulation 6A mggcapsu1e' Active ingredient '10 Lactose, B.P. -. 250 Sodium starch glycollate 25 Magnesium stearate 5 290 Formulation 6B mggcapsule Active ingredient 5 Pregelatinized starch NF15 245 ' - 250 Formulation 6C mggcagsule Active ingredient 10 Macrogol 4000, B.P. ‘ 3The Macrogol 4000, B.P. is melted and the active - ingredient dispersed therein. The thoroughly mixed melt is then filled into a two-part hard gelatin capsule.

Example 5 Injectable Formulation Active ingredient 10mg Sterile, pyrogen free pyrophosphate buffer (pH 10), q.s. to _ 10ml The active ingredient is dissolved in most of the phosphate buffer (35-40°C), then made up to volume and filtered through a sterile micropore filter into a 10 ml amber glass vial (type 1) and sealed with a sterile closure and.overseal.

Example 6’ Suppository Formulation mggsuppositogxg Active ingredient, 63um* 10 Hard fat, B.P. (Witepsol H15- Dynamit Noble 1) 1790 1800 *The active ingredient is used as a powder wherein at least 90% of the particles are of 63 um or less. our—fifth of the Witepsol H15 is melted in a steam-jacketed pan at 45°C maximum. The active ingredient is sifted through a 200 um sieve and added to the molten base with mixing, using a silverson fitted with a'cutting head, until a smooth dispersion is achieved. Haintaining the mixture at 45°C, the remaining Witepsol H15 is added to the suspension and stirred to ensure a homogeneous mix. The entire suspension is passed through a 250 um stainless steel screen and, with continuous stirring, is allowed to cool to about 40°C. At a temperature of 38°C to 40°C 1.80 g of the mixture is filled into suitable plastic moulds. The suppositories are allowed to cool to room temperature.

Certain Experiments were carried out into the effectiveness of 5-substituted uracils according to the invention.

Determination of Uracil Reductase Inactivation Uracil reductase (1 micromolar) (dihydropyrimidine dehydrogenase, EC 1.3.1.2) purified from bovine liver was incubated with 100 micromolar inactivator and 5mM dithiothreitol (enzyme reductant) at 37° for 30 minutes in 0.05 M Tris-HC1 at pH 8.0. The enzyme and inactivator were diluted 100-fold into the assay buffer, which contained 200 micromolar NADPH, 200 micromolar thymine and 1mM dithiothreitol in Tris-HC1 at pH 8.0. The velocity of the enzyme was determined spectrophotometrically. These velocities have been corrected for NADPH oxidase activity; which was less than 10% of the rate of thymine—dependent oxidation of NADPH. The % inactivation of the enzyme was equal to 100% minus the percent of enzymatic activity remaining.’ Enzyme incubated without inhibitor was stable under these conditions. Parenthetical values are the relative first-order rate constants for inactivation of enzyme determined from similar experiments where the fractional activity was measured as a function of the time of incubation of 50 micromol inactivator with enzyme.

The results are given be1ow:- \ comgound % Inactivation -ethynyluracil 100 (100) -cyanouracila y 100 (14) -propynyluracil 100 (8) -bromoethynyluracil ' 100 (8) -(1-chloroviny1)uraci1 100 (5) -iodouracil 100 (4) -hexynyluracila 90 -vinyluracilarb . 86 -trifluoromethyluracil 75 -bromouracil , 75 a The inhibition was reversible since enzyme treated with this derivative slowly regained activity after a 100-fold dilution into the assay mixture; b These nucleobases were generated in situ by treating the respective nucleosides with 40 units/ml of thymidine phosphorylase in 35 mM potassium phosphate for 20 minutes prior to addition to uracil » reductase. The parent nucleosides were not inactivators. .

The effectiveness of 5-ethynyluracil (EU) was investigated and is reported in the following Experiments 2 to 4 and Figures wherein Figure 1 shows increased levels of uracil and thymine at a time of four hours following various oral EU doses in rats; and Figure 2 shows that EU increased plasma levels of -fluorouracil (5-FU). Mice were dosed either orally (p.o.) or interperitoneally (i.p.) with 5-FU. 5-ethynyluracil (EU) at 2mg/kg was dosed i.p. 90 minutes prior to the 5-H}.

Egperiment 2 Inactivation of uracil reductase (in vivo) Mice, rats, dogs and monkeys dosed with small amounts of -ethynyluracil (EU) rapidly developed greatly elevated plasma uracil and thymine levels. The maximum effect occurred at about 0.1 mg/kg p.o. in rats, at 0.5 to 1 mg/kg s.c. in mice, and at approximately 1 mg/kg intravenously (i.v.) in dogs and probably represents total inactivation of uracil reductase. These'doses elevated mouse, dog, and rat plasma uracil from about 3 uM to about 50-60 uM. Plasma uracil decreased to normal over 24 hr (half-life = lohr). Figure 1 shows the increased plasma levels of uracil and thymine in the rat at a time of 4 hours following various oral doses of 5-ethynyluracil, due to inactivation of uracil reductase. The ED5o equals 0.01 mg/kg.

Egperiment 3 Effect on plasma-FU level Mice and rats pretreated with 5-ethynyluracil (EU) and then dosed with FU sustained higher plasma levels of FU than mice not pretreated (Figure 2). In addition, the usual variability in plasma FU in rats orally dosed with FU at 50 mg/kg was eliminated by EU pretreatment. The AUC of the plasma FU concentration-time curves were 41, 126 and 68 (ave = %) for nonpretreated an respectively.

Egperiment 4 + -fluorouracil Colon 38 tumor was implanted in mice on day zero. per group) were treated with 5 with the doses indicated in Ta mg/kg 30 minutes prior to 5 Table 2 % Mice Tumor Free on Day 17 Dose 5-FU FU i.p. plus EU FU i.Q. (mggkg) .25 I5 o 1 . 2 3 4 ' O 12.5 37.5 100 100 .5 12.5 .37.5? %) versus 417, 446 and 426 (ave = 430 d EU pretreated rats, nice (8 —FU on days one through nine ble 2 EU was dosed i.p. at 2 -FU dosing where indicated.

FU p.o.p1us EU FU D.o. .5 12.5 12.5 12.5 one non-tumor related death occurred in these groups

Claims (1)

1.

1. CLAIMS Use of 5—ethynyluracil in the manufacture of a medicament for use as a uracil reductase inactivator in cancer chemotherapy. A pharmaceutically acceptable combination which comprises 5-ethylnyluracil and 5—fluorouracil or a prodrug thereof as separate or mixed components for concomitant, separate or sequential administration. A combination as claimed in claim 2, which comprises 1 to 200 mg of 5—ethynyluracil. A combination as claimed in claim 3, which comprises 2 to 50 mg of 5—ethylnyluracil per unit dosage form. A combination as claimed in claims 3 or 4 and comprising 20 to 1000 mg of 5—fluorouracil or prodrug thereof, per unit dosage form. A combination as claimed in claim 5, wherein the ratio of 5—ethynyluracil to 5—fluorouracil or prodrug thereof is in the range l:0.01 to 1:100 by weight. A combination as claimed in any of claims 2 to 6 presented for oral administration. A combination as claimed in claim 7, wherein the active components are presented in the form of a tablet, capsule or sachet. A pharmaceutical formulation comprising 5—ethynyluracil, 5—fluorouracil or a prodrug pharmaceutically acceptable carrier. thereof, and a A formulation according to claim 9, comprising from 1 to 200 mg 5—ethynyluracil per unit dosage form. A formulation according to claim 10, comprising from 2 to 50 mg 5—ethynyluracil per unit dosage form. A formulation according to claim 9, 10 or 11, which comprises 5 to 3000 mg 5-fluorouracil or prodrug thereof. A formulation according to Claim 12 which comprises 20 to 1000 mg 5-fluorouracil or prodrug thereof. A process of preparing a pharmaceutically acceptable combination which bringing ethynyluracil and 5-fluorouracil or a prodrug thereof. comprises together 5- Use of a compound substantially as hereinbefore described with reference to the examples and drawings. IX pharmaceutically acceptable combination substantially as hereinbefore described with reference to the examples and drawings. A pharmaceutical formulation substantially as hereinbefore described with reference to the examples and drawings.