# Patent

## Title
Certain guanidine compounds, and their use as inhibitors of histamine

## Abstract

This is a division of application Ser. No. 448,748 filed Mar. 6, 1974, now U.S. Pat. No. 3,994,910.

## Background
Since its discovery almost a quarter of a century ago, phenylbutazone (4-n-butyl-1,2-diphenyl-3,5-pyrazolidinedione) has dominated the field of non-steroid anti-inflammatory drugs despite the fact that it has several serious toxic effects of which ulcerogenesis and fluid retention are probably the most frequent.

The most probable reason for the continued success of phenylbutazone is that none of the numerous modifications of its structure nor the even more numerous attempts to design novel structures with anti-inflammatory activity have resulted in a truly successful separation of desired pharmacological activity and undesired toxicity.

This invention relates to a process for preparing derivatives of 1,2-diphenyl-3,5-dioxo-4-n-butyl-pyrazolidine having the formula: ##STR2## in which R is represented by a basic compound namely: either 2-amino-4-methyl-pyridine or 2-amino-2-thiazoline, having the respective formulae: ##STR3##

It has been found that the compounds of Formula I are a clear improvement over phenylbutazone in that they have increased therapeutic activities but reduced or decreased toxicity.

As will be more fully discussed hereinafter, the therapeutic compounds of the present invention have a number of additional advantages over phenylbutazone. For example, smaller doses of the new therapeutic compounds as compared with phenylbutazone can be used with comparable and superior effectiveness. The therapeutic compounds of the present invention have fewer and less severe side effects.

In equimolar reaction with 1,2-diphenyl-3,5-dioxo-4-n-butyl-pyrazolidine, these compounds form stable crystalline combinations with an interesting therapeutic action as antiinflammatories, analgesics and analeptics.

Pharmacological testing of these compounds led to results to be described hereinafter and reflected in the compound formed by the equimolar combination of 1,2-diphenyl-3,5-dioxo-4-n-butyl-pyrazolidine-2-amino-2-thiazoline, referred to hereinafter as LAS-11871. The equimolar combination of phenylbutazone salt with 2-amino-4-methylpyridine is hereinafter referred to as LAS 6671.

The doses of compounds referred to are in mg of salt and not in mg equivalents of phenylbutazone content (i.e., the comparison has been made on a weight for weight basis and not equimolar) since it was considered that this would be more demonstrative of the potential value of the compound. Equimolar comparisons can be made by taking into account the respective molecular weights of LAS 11871 (410.54) and phenylbutazone (308.4) from which it is evident that 100 mg. of LAS 11871 contains the equivalent of 75 mg of phenylbutazone.

The properties and advantages of the therapeutic compounds of the present invention will be discussed below as to some of their therapeutic activities, their toxicity effects and their chemical functions and synthesis.

LAS 11871 and 6671 were compared in a preliminary screening test with phenylbutazone and a commercially available piperazine salt of phenylbutazone and they had definite advantages over each of these two products (see Table I below).

This shows the effects of LAS- 11871 in various screening tests as compared with phenylbutazone and a piperazine salt thereof. Desired Effects Toxic Effects Compound     CE      AA      AP    UG    TX ______________________________________ LAS 11871    ++      +++     +++   ++    + LAS 6671     ++      +       ++    ++    + Phenylbutazone ++      ++      ++    ++    ++ Piperazine salt of Phenylbutazone +       +       +     +     + ______________________________________ CE = Inhibition of carrageenin-induced oedema in rat's paw. AA = Inhibition of contortions induced by acetic acid in mice. AP = Inhibition of yeast-induced pyrexia in rats. UG = Intensity of ulceration produced in the rat stomach. TX = Acute toxicity in mice.

More detailed studies confirmed these preliminary results and clearly showed that LAS 11871, although more active as an analgesic and anti-inflammatory agent than phenylbutazone, produces fewer gastric lesions and is less toxic than phenylbutazone (see Tables 2, 3, 4, 5 and 6 below).

This shows the effect of various doses of phenylbutazone and LAS 11871 on carrageenin-induced oedema in the rat's paw. Compound per os     Volume of paw % Inhibition 1 h before  No. of  (ml) standard .+-. standard carrageenin animals error         error ______________________________________ Control     46      0.9663 .+-. 0.0564 0.00 .+-. 5.80 Phenylbutazone 200 12      0.2458 .+-. 0.0454** 74.60 .+-. 4.70 100         18      0.3139 .+-. 0.0224** 67.50 .+-. 2.30 50         22      0.6886 .+-. 0.0699* 28.70 .+-. 7.24 25         22      0.6545 .+-. 0.0545** LAS 11871 200 11      0.1545 .+-. 0.0384** 84.00 .+-. 3.97 100         18      0.2667 .+-. 0.0428** 72.40 .+-. 4.43 50         22      0.6182 .+-. 0.0683* 36.01 .+-. 7.06 25         22      0.7864 .+-. 0.0632 18.60 .+-. 6.54 ______________________________________

Volume of paws measured 3 hours after injection of carrageenin *P <0.05, >0.001; **P <0.001 for the differences from the control using Student's "t" test. __________________________________________________________________________ Effects of various doses of phenyl butazone and LAS 11871 on granuloma induced in rats by implantation of cotton balls. __________________________________________________________________________ Percentage No. of         Dry granuloma .+-. inhibition mg/Kg/day of compound granulomas Weight of wet standard error Wet    Dry per os       (animals) granuloma (mg)   granuloma granuloma __________________________________________________________________________ Control      40 (20) 454.20 .+-. 11.74 77.34 .+-. 0.33 0.00 .+-. 2.60 0.00 .+-. 0.40 Phenylbutazone 200 20 (10) 353.40 .+-. 13.14** 49.96 .+-. 4.25** 22.20 .+-. 2.80 35.40 .+-. 5.50 100          20 (10) 424.50 .+-. 13.47 71.23 .+-. 5.18 6.50 .+-. 2.90 7.90 .+-. 6.70 50          20 (10) 434.75 .+-. 18.36 83.94 .+-. 8.22 4.30 .+-. 4.10 8.50 .+-. 10.6 LAS 11871 200 20 (10) 361.21 .+-. 12.84** 48.29 .+-. 1.98** 20.50 .+-. 2.80 37.60 .+-. 2.50 100          20 (10) 369.69 .+-. 16.68** 61.95 .+-. 4.74* 18.60 .+-. 3.70 19.90 .+-. 6.10 50          20 (10) 388.59 .+-.  8.74** 61.82 .+-. 3.16** 14.40 .+-. 1.90 20.00 .+-. 4.10 __________________________________________________________________________ The figures refer to the net weight of granuloma tissue obtained by subtracting the original weight of the cotton ball. *P <0.05, >0.001 **P <0.001 for the differences from the control using Student's "t" test. ______________________________________ Effect of various doses of phenylbutazone and LAS 11871 on cortortions induced by acetic acid injected into the abdominal cavity of the mouse ______________________________________ mg/kg of compound    No. of per os 1 h before No. of   contortions .+-. % inhibition .+-. acetic acid injection animals  standard error standard error ______________________________________ Control     20       81.65 .+-. 5.73 0.00 .+-. 7.02 Phenylbutazone 300 10       42.30 .+-. 6.75** 48.20 .+-. 8.27 100         10       47.30 .+-. 6.70* 42.10 .+-. 8.20 30         10       59.00 .+-. 6.51* 27.70 .+-. 7.97 LAS 11871 300 10       24.10 .+-. 3.74** 70.50 .+-. 4.60 100         10       36.90 .+-. 6.34** 54.90 .+-. 7.76 30         10       44.20 .+-. 6.03** 45.90 .+-. 7.39 ______________________________________ *P <0.05, >0.001 **P >0.001 for the differences from the control using Student's "t" test.

Ulcerogenic activity of LAS 11871 on the stomach as compared with phenylbutazone ______________________________________ Ulcerogenic activity of LAS 11871 on the stomach as compared with phenylbutazone ______________________________________ mg/kg of compound No. of    .+-. standard error of per os         animals   ulcerogenic indices ______________________________________ Control        40        0.17 .+-. 0.07 Phenylbutazone 2.times.200 29        5.00 .+-. 0.56 2.times.100    30        4.33 .+-. 0.47 2.times. 50    30        0.73 .+-. 0.21 LAS 2.times.200 29        3.65 .+-. 0.56* 2.times.100    30        2.43 .+-. 0.41** 2.times. 50    29        0.59 .+-. 0.19 ______________________________________ *P <0.1, >0.01 **P <0.01 for the differences between equivalent doses of phenylbutazone and LAS 11871 using Student's "t" test.

From Table 2 it is demonstrated that LAS 11871 is at least as active as phenylbutazone against inflammation and at doses of 50 mg/kg and above LAS 11871 was the more active compound.

Table 3 compares the activity of LAS 11871 and phenylbutazone against chronic inflammation. It is seen that although both products produced about the same degree of inhibition of granuloma tissue formation at high doses (200 mg/kg), at the lower dose levels (100 and 50 mg/kg) LAS 11871 continued to inhibit the granuloma tissue formation but phenylbutazone did not.

Table 4 demonstrates that LAS 11871 is more potent than phenylbutazone as an analgesic.

Although LAS 11871, in common with virtually all of the other non-steroid anti-inflammatory compounds, possesses a certain capacity to cause ulcerous lesions in the gastro-intestinal tract. However, as Table 5 illustrates, it is much less active in this respect than phenylbutazone. TOXICITY LD50 per os in the rat of LAS 11871 Group Dose       No. animals No. deaths % mortality ______________________________________ I     1000 mg/kg 10         1       10 II    1210 mg/kg 12         3       25 III   1470 mg/kg 10         5       50 IV    1780 mg/kg 10         9       90 V     2150 mg/kg 10         10      100 LD50 = 1425 mg/kg (1250 - 1624) LD50 per os in the rat of phenylbutazone Group Dose       No. animals No. deaths % mortality ______________________________________ I      464 mg/kg  9         1       11 II     562 mg/kg 10         4       40 III    681 mg/kg 10         8       80 IV     825 mg/kg 10         8       80 V     1000 mg/kg 10         9       90 VI    1210 mg/kg 10         10      100 LD50 = 620 (530 - 725) LD50 per os in the rat of 2-amino-thiazoline Group Dose       No. animals No. deaths % mortality ______________________________________ I     316 mg/kg  10         2       20 II    383 mg/kg  10         4       40 III   464 mg/kg  10         6       60 IV    562 mg/kg  10         7       70 V     681 mg/kg  10         9       90 VI    825 mg/kg  10         9       90 LD50 = 430 mg/kg (358 - 516) ______________________________________

In general, the new therapeutic compounds can be used to treat the same disorders as phenylbutazone. As the above discussion illustrates, the therapeutic compounds of the present invention are less toxic and less ulcerogenic than phenylbutazone, and they have greater effectiveness in anti-inflammatory, analgesic, and antipyretic activity. These therapeutic compounds have been found effective in treating humans as well as animals. For example, LAS 11871 has been shown effective in the treatment of humans with reumatic diseases and LAS 11871 has been used to successfully treat polyarthritics at doses of 200 mg. two, or three times per day.

These new therapeutic compounds also have limited and reduced side effects. As noted earlier, they have no anti-diuretic effect and relatively low ulcerogenic potential. They are also relatively free of serious side effects on the central nervous system.

However, the compounds, much more than phenylbutazone, show marked inhibition of spontaneous motor activity. This activity is best described as a tranquilizing or muscle relaxant activity. Also, the compounds appear to have immunosuppressant activity. PHARMACEUTICAL FORMULATIONS - LAS 11871 capsules     g ______________________________________ LAS 11871               0.200 Colloidal silica        0.005 LAS 11871 tablets LAS 11871               0.250 Hydroxypropyl cellulose 0.016 Microcrystalline cellulose 0.100 Carboxymethyl starch    0.012 Colloidal silica        0.003 Magnesium stearate      0.003 LAS 11871 suppositories LAS 11871               0.300 Stearine composition    1.240 LAS 11871 suppositories LAS 11871               0.5000 Ascorbyl palmitate      0.0025 Stearine composition    1.9975 Dose: from 200 to 1,500 mg/day ______________________________________

The reaction process for synthesising the therapeutic compounds of the present invention is carried into effect with the use of organic solvents such as methanol, ethanol, acetone, methyl ethyl acetone and dioxane in conditions which will be described in the following Examples. 1,2-diphenyl-3,5-dioxo-4-n-butylpyrazolidine-2-amino-4-methyl-pyridine.

30.8 g (0.1 mol) of 1,2-diphenyl-3,5-dioxo-4-butyl-pyrazolidine are introduced with agitation into a 500 cc flask and mixed with 150 ml of acetone until complete dissolution. 10.8 g (0.1 mol) of 2-amino-4-methylpyridine which have previously been dissolved in 100 cc of acetone are then added and the mixture is boiled for 30 minutes. It is filtered cold, and 39 g of a product having a melting point of 121.degree.-2.degree. C are crystallized out. 1,2-diphenyl-3,5-dioxo-4-n-butylpyrazolidine-2-amino-2-thiazoline.

Working is performed under the same conditions as in Example 1 but using ethyl alcohol as the solvent. 2.04 g (0.02 mol) of 2-amino-2-thiazoline are heated in ethanol with 6.16 g (0.02 mol) of 1,2-diphenyl-3,5-dioxo-4-n-butylpyrazolidine for 30 minutes; after cooling, the crystals which form are collected. The substance has a melting point of 161.degree.-2.degree. C. The yield is 86%. The final product was a white crystalline powder virtually insoluble in ether, sparingly soluble in water and soluble in hot ethanol.

## Claims

1. A pharmaceutical composition having anti-inflammatory activity in humans as well as in other animals, said composition comprising a therapeutic compound having the formula: ##STR4## in which R is 2-amino-2-thiazoline having the formula: ##STR5## together with a non-toxic pharmaceutically acceptable carrier or diluent therefor, said therapeutic compound present in sufficient amount to exhibit said activity.

2. The composition of claim 1 wherein said composition contains a dose of the therapeutic compound in the range 50-250 mg.

3. The composition of claim 1 wherein the composition is formulated so as to provide the equivalent of 200-1,500 mg/day of said therapeutic compound to the host.

4. The composition of claim 1 wherein it is in the form of a capsule.

5. The composition of claim 1 wherein it is in the form of a suppository.

6. The composition of claim 1 wherein it is in the form of a tablet.

7. A pharmaceutical composition having analgesic activity in humans as well as in other animals, said composition comprising a therapeutic compound having the formula: ##STR6## in which R is 2-amino-2-thiazoline having the formula: ##STR7## together with a non-toxic pharmaceutically acceptable carrier or diluent therefor, said therapeutic compound present in sufficient amount to exhibit said activity.

8. The composition of claim 7 wherein said composition contains a dose of the therapeutic compound in the range 50-250 mg.

9. The composition of claim 7 wherein the composition is formulated so as to provide the equivalent of 200-1,500 mg/day of said therapeutic compound to the host.

10. The composition of claim 7 wherein it is in the form of a capsule.

11. The composition of claim 7 wherein it is in the form of a suppository.

12. The composition of claim 7 wherein it is in the form of a tablet.

13. A pharmaceutical composition having anti-pyretic activity in humans as well as in other animals, said composition comprising a therapeutic compound having the formula: ##STR8## in which R is 2-amino-2-thiazoline having the formula: ##STR9## together with a non-toxic pharmaceutically acceptable carrier or diluent therefor, said therapeutic compound present in sufficient amount to exhibit said activity.

14. The composition of claim 13 wherein said composition contains a dose of the therapeutic compound in the range 50-250 mg.

15. The composition of claim 13 wherein the composition is formulated so as to provide the equivalent of 200-1,500 mg/day of said therapeutic compound to the host.

16. The composition of claim 13 wherein it is in the form of a capsule.

17. The composition of claim 13 wherein it is in the form of a suppository.

18. The composition of claim 13 wherein it is in the form of a tablet.

19. A pharmaceutical composition for treating rheumatic diseases in humans as well as in other animals, said composition comprising a therapeutic compound having the formula: ##STR10## in which R is 2-amino-2-thiazoline having the formula: ##STR11## together with a non-toxic pharmaceutically acceptable carrier or diluent therefor, said therapeutic compound present in an effective amount for carrying out said treatment.

20. The composition of claim 19 wherein said composition contains a dose of the therapeutic compound in the range 50-250 mg.

21. The composition of claim 19 wherein the composition is formulated so as to provide the equivalent of 200-1,500 mg/day of said therapeutic compound to the host.

22. The composition of claim 19 wherein it is in the form of a capsule.

23. The composition of claim 19 wherein it is in the form of a suppository.

24. The composition of claim 19 wherein it is in the form of a tablet.