WO1984004677A1

WO1984004677A1 - Pharmaceutical compositions with anthelmintic activity, dosage units thereof and method for treating helminthiasis in animals

Info

Publication number: WO1984004677A1
Application number: PCT/EP1984/000155
Authority: WO
Inventors: Eva-Maria Bennet; Christopher Bryant; Carolyn Anne Behm
Original assignee: Hoechst Ag
Priority date: 1983-05-27
Filing date: 1984-05-24
Publication date: 1984-12-06
Also published as: EP0146573A1

Abstract

Pharmaceutical composition having a high degree of anthelmintic activity comprising I) levamisole of formula (2), and IIa) a subsituted benzimidazole carbamates of formula (3), wherein R1 represents a 5- or 6-membered heterocyclic ring or a radical -NHCO2R2, wherein R2 represents alkyl; R3 represents alkyl, or a radical -NHCO2R2 or a radical -XR4, wherein X represents O, CO, S, SO, SO2, -SO2-O- or -O-SO2 and R4 represents a hydrocarbon group or aryl substituted by alkoxy, halogen or alkyl groups which in turn are substituted by at least one halogen atom, with the proviso that when R1 is in the 5-position and R1 represents -NHCO2CH3 and X represents CO, R4 does not represent phenyl and with the further proviso that at least one of R1 and R3 must represent the radical -NHCO2 alkyl, (IIb) pro-drugs therefor or (IIc) non-toxic acid addition salts of said substituted benzimidazole carbamates or pro-drugs. The invention also relates to a dosage unit of such a composition and a method for treating helminthiasis in animals by administering an effective amount of such composition.

Description

PHARMACEUTICAL COMPOSITIONS WITH ANTHELMINTIC ACTIVITY, DOSAGE UNITS THEREOF AND METHOD FOR TREATING HELMINTHIASIS

IN ANIMALS

This invention relates to methods and compositions useful in the treatment of parasitic diseases in animals. More particularly, the invention relates to compositions containing a substituted benzimidazole carbamate, or a pro-drug there for, and levamisole in which the anthelmintic action of the composition is enhanced over that expected from the activity of either ingredient when used alone.

Helminthiasis is a widely occurring disease affecting animals, causing substantial economic losses in both game and the domesticated animal industry. Particularly susceptible to the disease are sheep, cattle, goats, horses and mules. Many anthelminitc agents have been discovered possessing varying degrees of efficacy on the particular helminths causing the infections. For example, mebendazole (1) (of. Formula sheet) is a broad-spectrum anthelmintic [Heath, D.D., Christie, M.J. and Chevis, RAF, 1975. Parasitology, 70, 273-285] and levamisole (2) (formula as. shown in claim 1) is effective against nematodes at low concentrations [Janssen, PAJ, 1976, Prog. Res., 20, 347-3533.

Research has been directed both to seeking new classes of anthelmintic active materials and to finding ways for elirainating disadvantages in, and improving the efficacy of, the currently known anthelmintic agents. It is known, for example, that simultaneous administration of levamisole (2), in combination with mebendazole (1) [EM Bennet, C. Behm and C. Bryant, Int. J. Parasitology, 1978, 8, 463-466] or other 2-substituted benzimidazoles [JD Netta et al, US Patent No. 3,325,356] enhances the anthelmintic activity of benzimidazoles against tetrathyridia of Mesocestoides Corti in the raouse and Haemonchus Contortus in sheep and cattle respectively.

One disadvantage of the repeated use of the same composition is that the parasites, for which the composition is initially effective against, become more resistant to the composition, requiring higher administration rates to effect a therapeutic dose. This increases the costs of curing helminthiasis and, for relatively insoluble agents such as mebendazole, increases the difficulty in administering the compositions as larger quantities have to be introduced into the animals.

Accordingly, it is a first object of the present invention to provide compositions possessing a high degree of anthelmintic activity which overcome the above problems. A second object is to provide compositions which contain substituted benzimidazole carbamates, or pro-drugs therefor, and levamisole in which the anthelmintic potency and efficacy of the composition is enhanced over the additive effect of th.e substituted benzimidazole carbamate, or a pro-drug therefor, and levamisole. A third object is to provide a method for treating helminthiasis with compositions containing anthelmintically active substituted benzimidazole carbamates, or pro-drugs therefor, and levamisole wherein the dosage levels are substantially reduced over those required when each is administered alone. According to one aspect of the present invention, there is provided a method of treating helminthiasis by the administration of a composition having a high degree of anthelmintic activity said composition comprising I) levamisole and II) a substituted benzimidazole carbamate of the general formula (3) (of. Claim 1) wherein

R ¹ represents a 5- or 6-membered heterocyclic ring containing at least one hetero atom selected from O, N and S, or a radical -NHCO ₂ R ² , wherein R ² represents alkyl; R ³ preferably is in 5-position and represents alkyl, a radical -NHCO ₂ R ² or a radical -XR ⁴ , wherein X represents O, CO, S, SO, SO ₂ , -SO ₂ -O- or -O- SO ₂ - and R ⁴ represents a hydrocarbon group, eg alkyl, cyclo alkyl, aryl or aryl hydrocarbon, or substituted aryl, ie aryl substituted by alkoxy, halogen or alkyl groups substituted in turn by at least one halogen atom, with the proviso that when R ³ is in the 5-position and R ¹ represents -NHCO ₂ CH ₃ and X represents CO, R ⁴ does not represent phenyl and with the further proviso that at least one of R ¹ and R ³ must represent the radical -NHCO ₂ alkyl, or a pro-drug therefor or a non-toxic acid addition salt of said substituted benzimidazole carbamate or said prodrug therefor, where such acid addition salts exist. As used throughout the specification, the terms "heterocyclic ''," alkyl "," substituted alkyl "," cycloalkyl "," aryl "and" substituted aryl "are used to denote the following:" heterocyclic "5- or 6-membered aliphatic or aromatic rings containing at least one hetero atora selected from O, N and S; preferred examples include furan, thiophene, tetrahydrofuran, pyrrolidine, isoxazole, piperidine, pyrrole, oxazole, thiazole, imidazole, pyrazole, triazole, tetrazole, pyridine, pyridazine , pyrimidines, pyrazine and pyran; "alkyl" straight or branched-chain hydrocarbons of 1 to

10, preferably 1 to 4 carbon atoms; "cycloalkyl" alicyclic rings containing from 3 to 6 carbon atoms; preferred examples are cyclopropyl, cyclopentyl and cyclohexyl; "aryl" 6- or more-membered aromatic rings which may or may not be fused to further 6- or more-membered aromatic or 5- or more-membered aliphatic rings; preferred examples include benzene, naphthalenes, indene and tetrahydronaphthalenes; "aryl hydrocarbon" aryl substituted by one or more, preferably at most three hydrocarbon groups separately selected from the group consisting of alkyl having from 1 to 4 carbon atoms, alkenyl and alkynyl; a preferred example is methylindene; "substituted aryl" aryl which is substituted by one or more, preferably at most three, radicals separately selected from the group consisting of alkoxy, halogen and alkyl substituted by at least one halogen atom, and optionally also by one or more of the hydrocarbon groups cited with the aryl hydrocarbons.

Among the aryls, those having from 6 to 10 carbon atoms and more especially phenyl and substituted phenyl and among the aryl hydrocarbons and substituted hydrocarbons those which contain at most three substitents to the aromatic skeleton, are preferred.

A "non-toxic salt", as used throughout this specification, denotes pharmaceutically acceptable salts which do not produce undesired side effects when administered at effective dosage levels. Examples of such addition salts include the hydrohalic, sulfuric, nitric, phosphoric, citric, acetic and oxalic acid salts.

Throughout the specification, the term "pro-drug therefor" is used to denote a compound having a structural formula different from the substituted benzimidazole carbamate which, after administration to the animal, is converted to the substituted benzimidazole carbamate.

Examples of suitable pro-drugs are compounds having the general formula (4) (of. Claim 4) wherein X is O or S and both X may be equal or different;

R ⁵ and R ⁶ represent the same or different alkyl or cycloalkyl radicals; and R ⁸ represents H or R ³ , wherein R ³ is as inbefore defined. Further examples of pro-drugs according to the present invention are compounds having the general formula (5) (of. Claim 4), or tautomeric forms thereof, wherein R ⁷ represents a radical selected from the group consisting of amino, unsubstituted alkyl, and alkyl substituted by one or more, preferably at most three, radicals separately selected from the group consisting of alkenyl, al kynyl, alkoxy or halogen; most preferably one alkenyl or alkynyl group or one or two alkoxy groups or halogen atoms, and X, R ³ , R ⁵ and R ⁶ are as defined before. According to a second aspect of the present invention, there is provided a composition for the treatment of helminthiasis, said composition comprising levamisole and a substituted benzimidazole carbamate of the general formula (3) or a pro-drug therefor or a non-toxic acid addition salt of said substituted benzimidazole carbamate or said pro-drug therfor.

Compounds of the general formula (3) are either known or can be prepared from known compounds by Standard reactions well known in the art. For example, Fenbendazole (3a), Cambendazole (3b), Parbendazole (3c), Albendazole (3d), Oxfendazole (3e), Oxibendazole (3f), Flubendazole (3g) and Ciclobendazole (3h) (cf. formula sheet) are all coramercially available.

Examples of suitable pro-drugs include Thiophanate (4a) and Febantel (5a) both of which are commercially available (cf. formula sheet).

It has been found that when a substituted benzimidazole carbamate of general formula (3), or a pro-drug therefor, or their acid addition salt, is administered in combination with levamisole (2), reduced dosages to those normally employed for the individual components are therapeutically effective. The dosage rate will depend upon the activity of each particular benzimidazole carbamate, or pro-drug therefor, the size of the animal to be cured and the severity of infection.

Generally, it has been found that a ratio of active components of the order of about 1 to 10 parts of the benzimidazole carbamate, or pro-drug therefor, or their acid addition salt, to about 0.1 to 5 parts of levamisole is effective in removing the parasites.

The compositions of the present invention exhibit a synergistic effect at combined dosage levels lower than those employed when using each active component separately. The compositions are normally administered in daily amounts of 1 to 50 mg / kg body weight for a period of 1 to 14 days. The compositions of the present invention are effective against helminths and especially effective against Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Chabertia, Strongyloides, Oesophagostomum, Hyostrongylus, Ancylostoma, Dictyocaulus, Ascaris, Heterakis and Fasciola. Particularly impressive is their activity against helmintic infections of the intestinal tract and against liver flukes. Therefore, the compositions are very useful for the treatment of infections in animals.

The combined amounts of each component in the composition will vary according to the type of treatment to be employed, the host animal, and the particular parasitic disease being treated.

The compositions of the present invention may be administered as a feed or feed supplement. The compositions of the present invention could therefore be mixed with the animal's normal feed ingredients. It is preferred to administer the composition in dosage units corresponding to the daily doses or a certain fraction thereof (divided dosage). Suitable dosage units are 1 to 50 mg / kg body weight. Each active component of the composition of the present invention may be administered simultaneously or sequentially provided that the administration of the second active component is during the period of biological activity in the animal of the first active component. The compositions of the present invention may be administered as a single dose or in any suitable sustained release device.

In addition to the active ingredients, the compositions of the present invention may include other, nonactive ingredients, such as the usual carriers.

The carrier may be an orally ingestible container for the composition, for example, a gelatin capsule, or it may be an excipient of the kind normally used in medicaments of this character including maize starch, terra alba, lactose, sucrose, calcium phosphate, gelatin, stearic acid, agar, pectin or the like. A wide variety of forms can be employed in those cases wherein the medicament is not admixed with the feed. Thus, if a solid carrier is used, the composition can be administered in tablet or capsule form. If a liquid carrier like peanut oil, sesame oil or water is used, the composition may be in the form of a soft gelatin capsule or in a liquid suspension.

When the compositions are prepared as solid unit dosage forms, as in tablets, the additional ingredients may be any other acceptable vehicle (s) convenient in the preparation of such forms.

When the unit dosage form is a drench, the composition may contain, where appropriate, agents which aid the subsequent suspending of the active ingredients in water, such as bentonite and the like, to form a dry pre-drench composition, and this pre- drench composition added to water just before use. In the predrench composition, in addition to the suspending agent, further possible additives include preservatives and anti-foaming compounds.

The general method of treating helminthiasis and of monitoring the resultant decrease in parasite numbers according to the present invention is illustrated in the example below. This method follows the international guidelines for evaluating the efficacy of anthelmintics in animals (Vet. Parasit. (1982) 10, 265-84). EXAMPLE A

Parasite free animals were each infected by injection with a parasitic larvae, either selected or not selected by benzimidazole anthelmintics. After a period of infection, the animals were split into four groups based on similar body weight and a similar random faecal nematode egg count. Alternatively, aftef a shorter period of infection, the animals were split on basis of similar body weight only, and the subsequent treatment effected on the fourth parasitic larval stage of the parasite. The first group was not subjected to anthelmintic treatment and was used as a comparison control. A second group was administered a dose of levamisole. A third group was treated with a substituted benzimidazole carbamate of formula (3). The final test group was administered a composition comprising 1 to 10 parts of a substituted benzimidazole carbamate of general formula (3) to 0.1 to 5 parts levamisole. All dosage levels were administered orally and calculated on the basis of the mean body weight of each group such that a

Standard dose was administered.

Autopsies were carried out on all members of each group after a number of days to establish total worm burdens. The number of adult worms recovered was used to calculate the percentage reduction in worms using the following formula:

mean No. worms in - mean No. worms in control group treated group

% reduction = mean No. worms in control group

In the group which had been administered levamisole in combination with a benzimidazole carbamate of formula (3), the worm count was greatly reduced, with the maximum effect being the complete removal of the parasitic nematodes. Further, the administration of levamisole in combination with a benzimidazole carbamate of formula (3) was found to be particularly effective against strains of parasitic larvae which are resistant to treatment with benzimidazple carbamates of formula (3) alone.

The prpsent invention is specifically illustrated by the following Examples which demonstrate the anthelmintic potency and efficacy of the compositions. EXAMPLE 1

Following the general method described in Example A, worm-free εheep were infected by intrarυminal injection with infective larvae of a laboratory selected, benzimidazole resistant strain of the gastro-intestinal nematode Haemonchus contortus. After 21-28 days of infection, the sheep were allocated to the four groups based on similar body weight and a random faecal nematode egg count. Group 1 was used as the comparison control. Group 2 was administered a dose of levamisole (LMS). Group 3 was treated with fenbendazole (FBZ). Group 4 was administered a composition comprising fenbendazole and levamisole. Several experiments were conducted, in which various dose rates were used. The results of those experiments are given in Table I.

Similar experiments in which sheep from Group 3 were administered fenbendazole at a dose rate of 5.00 mg / kg (the normal therapeutic dose rate) and 13.00 mg / kg, resulted in a percentage reduction in worms of 79.0 and 89.2 respectively. These experiments illustrate that FBZ at 0.75 x normal dose rate in combination with LMS is as effective as FBZ at 2.5 x normal dose rate, thus demonstrating the improved efficacy of the compositions of the present invention. EXAMPLE 2

Following a similar experimental procedure to that described in Example 1, worm-free sheep were infected with a laboratory selected, benzimidazole resistant strain of Trichostrongylus colubriformis. The synergistic effect of combining FBZ and LMS against this particular parasite can be seen from the Information given in Table II.

EXAMPLE 3

Following a similar experimental procedure to that described in Example 2, worm-free sheep were infected with a mixture of 3 nematode species - Haemonchus contortus (1), Ostertagia circumcincta (2) (laboratory selected and benzimidazole resistant) and Trichostrongylus Colubriformis (3) (a field strain), and then treated at dosage levels substantially below the normal therapeutic dose rates for each individual component of the composition. It was found that, by combining FBZ and LMS at theεe lower dose rates, complete removal of the parasitic nematodes was possible. The results of these experiments are given in Table III.

EXAMPLE 4

Following a similar experimental procedure to that described in Example 1, worm-free sheep were infected by an unselected benzimidazole susceptible strain of Haemonchus cpntortus. The results of that experiment, given in Table IV, further illustrate the anthelmintic efficacy and potency of fenbendazole in combination with levamisole, at substantially reduced dosage levels over the additive effect of the individuai components.

EXAMPLE 5

Following the general method described in Example A, two separate experiments were undertaken in which worm-free sheep were infected with benzimidazole susceptible Haemonchus contortus or Trichostrongylus colubriformis. After 7 days of infection, the sheep were allocated to the four groups to test the effect of the present compositions on the fourth parasitic larval stage of the parasite. The results of those experiments are given in Tables V and VI, which illustrate the synergistic effect of FBZ / LMS compositions against the fourth larval stage.

EXAMPLE 6

Following a similar experimental procedure to that described 'in Example 1, the effect of albendazole (ABZ) against mebendazole-resistant Haemonchus contortus was determined. The synergistic effect of ABZ in combination with LMS can be seen from the results detailed in Table VII.

A similar experiment in which sheep from Group 3 were administered the normal therapeutic dose rate of albendazole of 3.8 mg / kg, resulted in a percentage reduction in worms of 61.5. EXAMPLE 7

Following a similar experimental procedure to that described in Example 1, the effect of febantel (FBT) against Ostertagia spp. in sheep from the field was determined. The lower effective dose rate required for FBT in combination with LMS can be seen from the results presented in Table VIII.

A similar experiment in which sheep from Group 3 were administered the normal therapeutic dose rate for febantel of 5.0 mg / kg, resulted in a percentage reduction in worms of 80.0.

EXAMPLE 8

Following a method as described by EM Bennet, C Behm and C Bryant, in Int. J. Parasitology, 1978, 8, 463-466, it has been established that oxfendazole in combination with levamisole is effective against the larval stage of the tape-worm mesocestoides corti in mice, as the results detailed in Table IX illustrate.

Those skilled in the art will appreciate that modifications and variations to the invention described above are possible without departing. from the present inventive concept.

(3h)

(4a)

Thiophanates

(5a)

Claims

Claims:

1. Pharmaceutical composition having a high degree of anthelmintic activity comprising I) levamisole of formula (2)

(2) and

II) at least one of the compounds (IIa) substituted benzimidazole carbamates of the general formula (3)

(3)

wherein R ¹ represents a 5- or 6-membered heterocyclic ring containing at least one hetero atom selected from O, N and S, or a radical -NHCO ₂ R ² , wherein R ² represents alkyl; R ³ preferably is in 5-position and represents alkyl, or a radical -NHCO ₂ R ² or a radical -XR ⁴ , wherein X represents O, CO, S, SO, SO ₂ , -SO ₂ -O- or -O -SO ₂ - and R ⁴ represents a hydrocarbon group or aryl substituted by alkoxy, halogen or alkyl groups which in turn are substituted by at least one halogen atom, with the proviso that when R ³ is in the 5-position and R ¹ represents -NHCO ₂ CH ₃ and X represents CO, R ⁴ does not represent phenyl and with the further proviso that at least one of R ¹ and R ³ must represent the radical -NHCO ₂ -alkyl, (Ilb) pro-drugs therefor and

(IIc) non-toxic acid addition salts of said substituted benzimidazole carbamates or pro-drugs.

2. Composition as claimed in claim 1, wherein any alkyl has from 1 to 10 carbon atoms, cycloalkyl has from 3 to 6 carbon atoms, aryl is 6- or more-membered rings or 6- or more-membered rings which are fused to further 6- or more-membered aromatic or 5- or more-membered aliphatic rings, hydrocarbon substituents of aryl are alkyl, alkenyl or alkynyl and substituents - other than hydrocarbon substituents - of aryl groups are alkoxy, halogen or alkyl substituted by at least one halogen atom.

3. Composition as claimed in claim 1 or 2 in which the substituted benzimidazole carbamate is fenbendazole, cambendazole, parbendazole, albendazole, oxfendazole, oxibendazole, flubendazole or ciclobendazole.

4. Composition as claimed in claim 1 or 2, the pro-drug being a compound of the general formula (4)

(4)

wherein X is a radicals separately selected from the group consisting of O and S; R ⁵ and R ⁶ represent the same or different alkyl or cycloalkyl radicals; and R ⁸ represents H or R ³ , wherein R ³ is as defined in claim 1; or a compound of the general formula (5) or tautomeric forms thereof

(5)

wherein R ⁷ represents a radical selected from the group consisting of amino, unsubstituted alkyl, and alkyl substituted by one or more radicals separately selected from the group consisting of alkenyl, alkynyl, alkoxy or halogen; and X, R ³ , R ⁵ and R ⁶ are as inbefore defined, the pro-drug preferably being Febantel or Thiophanate.

5.Composition as claimed in one or more of Claims 1 to 4, comprising a mixture of 0.1 to 5 parts by weight of levamisole of formula (2) in claim 1 and 1 to 10 parts by weight of a substituted benzimidazole carbamate of formula ( 3) in claim 1, or a pro-drug therefor, or a non-toxic acid addition salt thereof.

6. Composition as claimed in one or more of Claims 1 to

5, wherein any alkyl groups including those being substituents of aryl groups, alkenyl groups, alkynyl groups andalkoxy groups as well as alkyl groups substituted by at least one halogen atom have at most 4 carbon atoms.

7. Composition as claimed in one or more of Claims 1 to

6, wherein any aryl hydrocarbon or substituted hydrocarbon has an aromatic skeleton of from 6 to 10 carbon atoms and contains at most three substitutes to the aromatic skeleton and is preferably phenyl or substituted phenyl.

8. Composition as claimed in one or more of Claims 1 to

7, wherein the non-toxic acid addition salt is selected from the group comprising hydrohalic, sulfuric, nitric, phosphoric, citric, acetic and oxalic acid salts.

9. A dosage unit of a composition as claimed in one or more of Claims 1 to 8 containing from 1 to 50 mg of the mixture of components (I) and (II) per kg body weight of the animal to be treated.

10. Method for treating helminthiasis in animals by administering an effective amount of a composition of one or more of Claims 1 to 9, preferably in a daily amount of 1 to 50 mg / kg body weight of the animal and preferably for a period of from 1 to 14 days.