GB2257361A - Anti-tumour substituted dihydroimidazoquinoxalines - Google Patents

Abstract

1,2-Dihydro-8-piperazinyl-4-phenylimadazo pyridopyrazine oxides and 1,2-dihydro-8-piperazinyl-4-phenylimidazo quinoxaline oxides of general formula (I) are useful in the treatment of cancer, in particular hypoxic tumours:- <IMAGE> where R<1> is alkyl of 1 to 6 carbon atoms, benzyl, phenyl, R<4>SO<2>-where R<4> is C1-6 alkyl, NH2COCH2-, R<5>-CO-where R<5> is alkyl of 1 to 6 carbon atoms, aminomethyl, pyridinyl, phenyl, halophenyl or <IMAGE> -where R<6> is alkyl of 1 to 6 carbon atoms; R<2> is phenyl unsubstituted or substituted by 1 or 2 substituents selected from halogen and alkoxy of 1 to 6 carbon atoms; R<3> is hydrogen or halogen; and X is-CH=or-N=;or a pharmaceutically acceptable salt thereof.d 1,2

Description

ANTI-TUMOUR COMPOUNDS The present invention relates to the use of dihydroimidazo-quinoxalines and dihydroimidazopyridopyrazines in the manufacture of medicaments useful in the treatment of cancer.

EP-A-214,632 discloses quinoxaline and pyridopyrazine derivatives which are useful as anti-anaerobic agents, for the treatment of diseases related to anaerobic bacteria.

Such diseases include for example, post-operative sepsis following lower gastrointestinal surgery or female urinogenital surgery, pelvic inflammatory disease, ulcers, gangrene, trichomonal vaginitis, non-specific vaginitis, amoerbiasis, giardiasis, periodontal disease, acne, and the like.

Accordingly the present invention provides the use in the manufacture of a medicament, for use in the treatment of a tumour, such as a hypoxic tumour, of a compound of formula (I)

wherein R' is alkyl of 1 to 6 carbon atoms1 benzyl, phenyl,

where R4 is alkyl of 1 to 6 carbon atoms,

where R5 is alkyl of 1 to 6 carbon atoms, aminomethyl, pyridinyl, phenyl, halophenyl (e.g. fluorophenyl, chloroph-nyl or bromophenyl) or

where R6 is alkyl of 1 to 6 carbon atoms; R2 is phenyl unsubstituted or substituted by 1 or 2 substituents selected from halogen and alkoxy of 1 to 6 carbon atoms; R3 is hydrogen or halogen; and X is -CH= or -N=; or a pharmaceutically acceptable salt thereof.

According to a further feature the present invention provides a method for the treatment of a human or animal patient suffering from a tumour, such as a hypoxic tumour, which method comprises administering to the patient an effective amount of a compound of Formula (I), as hereinbefore defined, or a pharmaceutically acceptable salt thereof.

The invention provides, as a further feature, products comprising a compound of Formula (I) as hereinbefore defined or a pharmaceutically acceptable salt thereof, for use in the treatment of a tumour, such as a hypoxic tumour. The invention provides, as yet a further feature, a pharmaceutical agent for use in the treatment of a tumour, such as a hypoxic tumour, which agent comprises a compound of Formula (I), as hereinbefore defined, or a pharmaceutically acceptable salt thereof.

In the compounds of formula (I), the alkyl and alkoxy groups may be either straight or branched.

It is preferred that any alkyl groups in the compounds of formula (I) (including alkyl groups which form part of alkoxy groups) be alkyl groups of 1 to 4 carbon atoms, i.e.

methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl. Particularly preferred alkyl substituents are methyl, and ethyl, most preferably methyl.

Compounds of formula (I) in which R2 is substituted phenyl may be substituted in any position by 1 or 2 substituents selected from halogen atoms, e.g. fluorine, chlorine or bromine atoms, and alkoxy groups e.g. methoxy or ethoxy. The following substituted phenyl groups are illustrative of such groups: 4-chlorophenyl, 4-fluorophenyl, 2,4-dichlorophenyl, 2,4-difluorophenyl, 3-bromophenyl, 3chlorophenyl, 2-methoxyphenyl, 4-methoxyphenyl, 3 methoxyphenyl, 2-ethoxyphenyl, 4-ethoxyphenyl, 3ethoxyphenyl, 3,4-dimethoxyphenyl, 3,5-dimethoxyphenyl, 3,4diethoxyphenyl 3,5-diethoxyphenyl and 2-chloro-4methoxyphenyl. Preferred substituted phenyl groups are-A- halophenyl groups, such as 4-fluorophenyl.

Where Rl is a group

preferably R5 is aminomethyl, pyridinyl, phenyl or halophenyl.

Preferred compounds of formula (I) are those in which Rl is alkyl of 1 to 6 carbon atoms, benzyl or phenyl, especially those in which Rl is alkyl of 1 to 6 carbon atoms.

Also preferred are compounds of formula (I) in which R2 is unsubstituted phenyl or in which R3 is hydrogen.

Preferably X is -N=.

Of the compounds of formula (I) 1,2-dihydro-8-(4 methylpiperazinyl) -4-phenylimidazo [1,2-a) -quinoxaline-5-oxide and 1,2-dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo[1,2- a]pyrido[3,2-e)pyrazine-5-oxide may be specifically mentioned ås particularly preferred. Of these two the pyrido-pyrazine is more preferable.

Salts of the compounds of formula (I) used in the present invention may be any pharmaceutically acceptable acid addition salts. Examples of suitable salts include, salts of inorganic acids such as chlorides, bromides, iodides, phosphates and sulphates and salts of organic acids such as acetates, citrates, lactates and tartrates.

The compounds used in the present invention are known compounds which may be prepared using known methods. In particular they may be prepared according to procedures described in EP-A-214,632.

The compounds of Formula (I) may according to the invention, be used in uncomplexed form or in the form of a complex, such as a complex formed with one or more molecules of organic solvent, water (i.e. a hydrate), or hydrogen halide, e.g. hydrogen chloride.

The compounds of formula (I) are useful in increasing the sensitivity of tumour cells to radiation in radiotherapy and as bioreductive agents. A compound is administered to a patient having a radiation-treatable cancer, prior to or after, more typically shortly after irradiation of the tumour, in an amount effective to increase the sensitivity of the tumour cells to the effects of the irradiation.

Any solid tumour, which may have regions where cells are radiobiologically hypoxic and become resistant to ionising radiation, may be treated. Examples of such tumours are epithelial tumours of the head, neck, thorax and abdomen, soft tissue sarcomas and brain tumours. The compounds of formula (I) can therefore be employed in the radiotherapy of all such solid tumours where hypoxic cells are known or suspected to exist.

The compounds of formula (I) may also be used where an agent having differential hypoxic cytotoxicity is required.

The compounds can be employed for chemopotentiation of a chemotherapeutic agent or as a chemotherapeutic by administration of a compound (I) to a patient having a localised or metastatic cancer. Administration is carried out prior to simultaneously with or after administration, typically prior to or simultaneously with, of a chemotherapeutic agent such as melphalan, cyclophosphamide, 5-fluorouracil, adriamycin, CCNU(1-(2-chloroethyl)-3- cyclohexyl-l-nitrosourea) or tumour necrosis factor (TNF).

Any solid tumours, such as above, which are primary or secondary deposits, where it is known or suspected that hypoxic cells are present can therefore benefit from treatment employing a compound of formula (I).

The compounds of formula (I) are useful in particular for the treatment of hypoxic tumours. However the compounds of formula (I) may also be useful in the treatment of other tumours rich in enzymes required to activate the compounds of formula (I) as bioreductive agents or radiosensitisers. Such enzymes may include cytochrome P450, NADPH dependent cytochrome P450 reductase, DT-diaphorase and xanthine oxidase.

The compounds of formula (I) and salts thereof may be administered orally or intravenously. The amount administered depends on factors such as the cancer, the condition of the patient and the body weight of the patient.

Typically, however, doses of 50 to 1000mg/m2 of a patient's body area may be employed.

A compound of formula (I) may be formulated in a tanner appropriate to the treatment for which it is to be used by bringing it into association with a pharmaceutically compatible carrier or diluent. The compound may be included in a dosage form suitable for bolus injection or such as a tablet or capsule, for example a capsule comprising known formulation components. The compound may also be formulated for intravenous administration e.g. in a saline drip solution.

The following Examples illustrate the invention.

EXAMPLE 1 C3H mice in which the HT tumour had been implanted subcutaneously were administered RB 90003X [1, 2-dihydro-8- (4- methylpiperazinyl)-4-phenylimidazo-[1,2a]-pyrido-t3,2- e]pyrazine-5-oxide] interperitoneally immediately after irradiation with 10 Gy X-rays. The results are set out in Table 1 and comparison is made with the anti-tumour effects of the benztriazene di-N-oxide, SR 4233 [3-amino-1,2,4- benzotriazine 1,4-dioxide]; the dual function nitroimidazoles RSU 1069 [1-(2-nitro-1-imidazolyl)- 3-(1-aziridino)-2- propanol] and RB 6145 [l-(2-nitro-l-imidazolyl)-3-(2 bromoethylamino) -2-propanol3 and the radiosensitizer misonidazole. Values of the maximum tolerated dose (MTD) to C3H mice are also recorded.All compounds were administered in phosphate buffered saline (PBS) at pH 7.4, except RB=6145 which was in PBS at pH 5.4. Results are expressed as the administered i.p. dose required to cause a 4-fold increase in cell killing compared to radiation alone, i.e. 10 Gy alone gives a tumour cell surviving fraction of 2 x 10 TABLE 1 Compound Administered dose required to give a surviving fraction of 5 x MTD (iLmol keg4) RB 90003X 80 330 SR 4233 150 400 RSU 1069 90 380 RB 6145 200 940 Misonidazole 5000 5000 Clearly the anti-tumour efficacy of RB 90003X is similar to that of the other bioreductive drugs RSU 1069 and SR 4233.

EXAMPLE 2 C3H mice in which the transplantable rodent tumour RIF1 had been implanted subcutaneously were administered RB 90003X intraperitoneally immediately after irradiation with 10 Gy X-rays. The time for the tumour to increase in size to four times its original volume is compared with the corresponding time where no treatment was applied to the tumour and where the tumour was treated by irradiation alone.

The results shown in Table 2 below indicate that the use of RB 90003X immediately after irradiation to kill of viable cells which were hypoxic at the time of irradiation, leads to a significant slowing in the growth of the tumour.

TABLE 2 Treatment Time (in days) to 4 x treatment volume None 5.0 25 Gy only 24 30 Gy only 35 25 Gy + 100 mg/kg RB 90003X 36 25 Gy + 50 mg/mg RB 90003X 43 25 Gy + 20 mg/kg RB 90003X 41 EXAMPLE 3 The toxicity of RB 90003X towards aerobic or hypoxic V79 Chinese hamster cells in vitro is shown in Table 3 and comparison is made with SR 4233. Toxicity was determined by the use of the modified MTT assay (Stratford and Stephens (1989), Int. J. Radiat. Oncol. Biol. Phys. 16, 973-976).

Values quoted represent concentrations of drug required to reduce proliferation of treated cultures by 50%. Cells are treated with various drug doses for 3 hours at 370C under aerobic or hypoxic conditions, following drug removal cells are allowed to proliferate for 3 days prior to assay.

TABLE 3 Compound C air C N2 Ratio mmol dm3 RB 90003X 1.0 0.05 20 SR 4233 0.3 0.006 50 Clearly RB 90003 X is substantially more toxic to hypoxic compared with aerobic cells. While the differential is slightly higher for SR 4233, the aerobic toxicity of the mono-N-oxide is considerably less.

As a result of further determinations of the toxicity of RB 90003X using the same method, the following cumulative results were obtained: C air C N2 Ratio 0.85 0.07 12.1 EXAMPLE 4 The procedure of Example 3 was repeated but using a cells from a variety of human tumour cell lines, rather than the V79 Chinese hamster cells. The results were as follows: TABLE 4 Cell line C air C N2 Ratio H647 - lung tumour 1.8 0.15 12 H322 lung tumour 1.3 0.37 3.5 H460 lung tumour 2.8 0.15 18 A549 lung tumour 2.6 0.18 14 HT29 - colon tumour 1.2 0.07 17 MDA468 - breast tumour 1.3 0.07 19 EXAMPLE 5 The procedure of Example 3 was repeated but using a variety of compounds of Formula (I) rather than RB 90003X.

The results were as follows: TABLE 5 Compound C air C (N)2 Ratio RB 91726 0.9 0.023 42.0 RB 91701 0.63 0.055 11.5 RB 92810 0.8 0.03 26 RB 92812 1.0 0.04 25 The compounds identified in Table 4 are as follows: RB91726 - 1,2-Dihydro-8-(4-methylpiperazinyl)-4- phenylimidazo [1,2-a] pyrido [3,2-e] pyrazine 5-oxide bishydrochloride RB91701 - 1,2-Dihydro-8-(4-methylpiperazinyl)-4- phenylimidazo [1,2-a] quinoxaline 5-oxide RB9281O - 1,2-Dihydro-8-(4-methylpiperazinyl)-4(p- fluorophenyl)imidazo-[1,2-a] pyrido [3 ,2-e] pyrazine 5-oxide bishydrochloride RB92812 - 1, 2-Dihydro-8- (4-ethylpiperazinyl) -4- phenylimidazo [1,2-a] pyrido [3,2-e] pyrazine 5 oxide

Claims (10)

1. Use in the manufacture of a medicament, for use in the treatment of a tumour, of a compound of formula (I)

where Rl is alkyl of 1 to 6 carbon atoms, benzyl, phenyl,

where R4 is alkyl of 1 to 6 carbon atoms,

where R5 is alkyl of 1 to 6 carbon atoms, aminomethyl, pyridinyl, phenyl, halophenyl or

where R6 is alkyl of 1 to 6 carbon atoms; R2 is phenyl unsubstituted or substituted by 1 or 2 substituents selected from halogen and alkoxy of 1 to 6 carbon atoms; R3 is hydrogen or halogen; and X is -CH= or -N=; or a pharmaceutically acceptable salt thereof.

2. Use according to claim 1 of a compound of formula (I) in which Rl is alkyl of 1 to 6 carbon atoms, benzyl or phenyl, or a pharmaceutically acceptable salt thereof.

3. Use according to claim 3 in which Rl is alkyl of 1 to 6 carbons atoms, or a pharmaceutically acceptable salt thereof.

4. Use according to claim 3 in which Rl is methyl or ethyl, or a pharmaceutically acceptable salt thereof.

5. Use according to any one of claims 1 to 4 of a compound of formula (I) in which R2 is unsubstituted phenyl or 4-halophenyl, or a pharmaceutically acceptable salt thereof.

6. Use according to any one of claims 1 to 5 of a compound of formula (I) in which R3 is hydrogen, or a pharmaceutically acceptable salt thereof.

7. Use according to any one of claims 1 to 6 of a compound of formula (I) in which X is -N=, or a pharmaceutically acceptable salt thereof.

8. Use according to claim 1 of 1,2-dihydro-8-(4methylpiperazinyl)-4-phenylimidazo[1,2-a]quinoxaline-5-oxide or 1,2-dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo[1,2 a]pyrido[3,2-e]pyrazine-5-oxide, or a pharmaceutically acceptable salt thereof.

9. Use according to claim 8 of 1,2-dihydro-8-(4 methylpiperazinyl)-4-phenylimidazo[1,2-a]pyrido[3,2- e]pyrazine-5-oxide, or a pharmaceutically acceptable salt thereof.

10. Use according to any one of the preceding claims for use in the treatment of a hypoxic tumour.