WO1999056550A1

WO1999056550A1 - Method for treating migraine in mammals

Info

Publication number: WO1999056550A1
Application number: PCT/US1999/009745
Authority: WO
Inventors: Alvin J. Glasky
Original assignee: Neotherapeutics, Inc.
Priority date: 1998-05-04
Filing date: 1999-05-04
Publication date: 1999-11-11
Also published as: AU3785799A

Abstract

A method for treating migraine in mammals comprises the administration of an effective amount of a 9-substituted hypoxanthine derivative that selectively crosses the blood-brain barrier. Preferably, the 9-substituted hypoxanthine derivative is N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide. Other 9-substituted hypoxanthine derivatives can also be used. The invention also encompasses pharmaceutical compositions formulated for the treatment of migraine. The claimed compounds are also useful for protection against hypoxia, as demonstrated by the ability to protect against potassium cyanide-induced cell death in comparison to flunarizine as a positive control.

Description

METHOD FOR TREATING MIGRAINE IN MAMMALS

FIELD OF THE INVENTION

The present invention is broadly directed to pharmaceutical treatment methodologies. More particularly, the present invention is directed to a novel method for treating migraine in mammals through administration of a purine analog previously believed to have only neuroimmunologic activity.

BACKGROUND OF THE INVENTION

Migraine headache is a specific neurological syndrome that has a wide variety of manifestations. The headache may manifest itself with or without a preceding aura, typically marked by visual changes. The headache itself may last hours to days and may be accompanied with photophobia, hyperacusis, polyuria, or diarrhea. The frequency of migraine headaches in affected individuals may vary from one or two per year to as many as four per month. Migraine headaches are extremely common, and are estimated as affecting from 10% to 20% of the population. The morbidity associated with the large number of migraine sufferers is very high. According to one recent estimate, approximately 64 million workdays are lost per year as a result of migraine headaches. Although there has been an increasing understanding of the mechanism of migraine, drugs that are effective in the treatment of migraine are still surprisingly limited in number. As compared with other areas of pharmacology, therapeutic approaches to migraine have advanced only slightly over the past century. There is therefore a significant need for improved therapeutic approaches for the treatment of migraine.

A variety of novel 9-substituted hypoxanthine based bi-functional compounds and associated methods of use were discovered by the present inventor and disclosed in United States Patent No. 5,091,432 issued February 25, 1992 and incorporated herein by 2 reference. These compounds were believed to exhibit neuroimmunological activities based upon their ability to cross the blood-barrier in conjunction with their novel chemical structures comprising purine analogs chemically linked to analogs of biologically active compounds. Unlike large biologically active molecules which cannot cross the blood-brain barrier, these compounds could be administered orally or through injection into the bloodstream because the hypoxanthine based purine analog portion of the compound facilitates passage through the blood-brain barrier, and surprisingly, the chemically linked pharmaceutically active compound analog portions continue to exhibit biological activity as well.

While continuing to develop an understanding of the functions and pharmacology of these compounds, it was unexpectedly discovered by the present inventor that additional, unforeseen biological activities could be impacted by a number of these compounds beyond those activities which would be expected from their structure and known or suggested pharmacology.

Accordingly, it is an object of the present invention to provide novel pharmaceutical methods of treatment and associated pharmaceutical medicaments configured to treat physiologically disorders and disease conditions beyond those which would be expected from an understanding of the chemistry and structure of these pharmaceutical compounds.

It is an additional object of the present invention to provide a novel method and associated medicament for treating migraine in mammals.

SUMMARY

I have found that novel 9-substituted hypoxanthine derivatives have unexpected properties and have properties useful in the treatment of migraine in mammals. One aspect of the present invention is a method for treating migraine in a mammal comprising the step of administering an amount effective to reduce or eliminate at least one symptom of migraine of a 9-substituted hypoxanthine derivative of formula (I) to the mammal,

(I) wherein n is an integer from 1 to 6, Ri is selected from the group consisting of H, COOH, and COOWi, where Wi selected from the group consisting of lower alkyl, amino, and lower alkylamino, R₂ is selected from the group consisting of H and OH, and R₃ is selected from the group consisting of H and OH.

Typically, n is 2.

A particularly preferred 9-substituted hypoxanthine derivative for use in methods according to the present invention is N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3- (6-oxohydropurin-9-yl)propanamide, designated AIT-297. Other 9-substituted hypoxanthine derivatives useful according to the present invention are N-(2-(3,4-dihydroxyphenyl)ethyl)-3- (6-oxohydropurin-9-yl)propanamide, designated AIT-203, and N-(l-carboxyl-2-(3,4- dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide, designated AIT-201.

The amount of the 9-substituted hypoxanthine derivative administered can be from about 0.01 mg/kg to about 60 mg/kg. However, other dosages can be used.

The method of the present invention can further comprise administering an effective amount to the mammal of at least one additional anti-migraine agent. The at least one additional anti-migraine agent can be selected from the group consisting of acetylsalicylic acid (aspirin), acetaminophen, ibuprofen, indomethacin, naproxen sodium, ergotamine, dihydroergotamine, other ergot analogues, and sumatriptan.

Another aspect of the present invention is a pharmaceutical composition useful in the treatment of migraine. A pharmaceutical composition according to the present invention comprises:

(a) an effective amount of a 9-substituted hypoxanthine derivative of formula (I) as described above; and (b) a pharmaceutically acceptable carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

The following invention will become better understood with reference to the specification, appended claims, and accompanying drawings, where:

Figure 1 is a diagram of a thin-layer chromatogram of the crude product from the synthesis of N-(2-(3,4-dihydroxyphenyl)ethyl)-3-(6-oxohydropurin-9-yl)propanamide of Example 2; chromatography was performed in 20% methanol in ethyl acetate, with visualization by ultraviolet light;

Figure 2 is a diagram of a thin-layer chromatogram of the purified product from the synthesis of N-(2-(3,4-dihydroxyphenyl)ethyl)-3-(6-oxohydropurin-9-yl)propanamide of Example 2; chromatography was performed in 30% methanol in ethyl acetate with visualization by ultraviolet light; and Figure 3 is a graph showing the results of an experiment in which mice were given the compound N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9- yl)propanamide or flunarizine as a positive control prior to administration of potassium cyanide; the compound N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9- yl)propanamide is shown to protect against potassium cyanide-induced cell death. DESCRIPTION

These and other objects are achieved by the novel method and associated medicament of the present invention which provides a new treatment intended to treat migraine in mammals.

In general, the method of the present invention comprises the administration of an effective amount of a 9-substituted hypoxanthine analogue of formula I

(I) wherein n is an integer from 1 to 6, Ri is selected from the group consisting of H, COOH, and

COOWi, where Wi selected from the group consisting of lower alkyl, amino, and lower alkylamino, R₂ is selected from the group consisting of H and OH, and R₃ is selected from the group consisting of H and OH.

Preferably, n is 2. When n is 2, one particularly preferred 9-substituted hypoxanthine derivative usable in methods according to the present invention is N-(2-hydroxy- 2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide, where n=2, Ri is H, R₂ is OH, and R₃ is OH; this compound is designated AIT-297. This compound is also known as 3-(l,6-dihydro-6-oxo-9H-purin-9-yl)-N-(2-(3,4-dihydroxyphenyl)-2- hydroxyethyl)propanamide. Another 9-substituted hypoxanthine derivative usable in methods according to the present invention is N-(2-(3,4-dihydroxyphenyl)ethyl)-3-(6-oxohydropurin-9- yl)propanamide, where n=2, Ri is H, R₂ is H, and R₃ is OH; this compound is designated AIT- 203. Still another particularly preferred 9-substituted hypoxanthine derivative is N-(l- 6 carboxyl-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide, where n=2, Ri is COOH, R is H, and R₃ is OH; this compound is designated AIT-201.

More specifically, the method of the present invention comprises the administration of an effective amount of N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6- oxohydropurin-9-yl)propanamide to a mammal in order to mitigate or treat migraine. Preferably, the N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9- yl)propanamide is configured as a pharmaceutical medicament including a pharmaceutically acceptable carrier such as water or other appropriate liquid carriers or dry carriers and excipients as known in the art. The pharmaceutically acceptable carrier can be chosen from those generally known in the art, including, but not limited to, human serum albumin, ion exchangers, alumina, lecithin, buffered substances such as phosphate, glycine, sorbic acid, potassium sorbate, and salts or electrolytes such as protamine sulfate. Other carriers can be used.

Although Applicant does not intend to be bound by this theory, it is believed that the method and medicament of the present invention function by blocking or inhibiting Type L calcium channels and by relieving hypoxia.

As used herein, the phrase "an amount effective to reduce or eliminate at least one symptom of migraine" means an amount effective to detectably reduce or eliminate at least one of the following symptoms as experienced by a migraine sufferer: pain, ophthalmic disturbances, photophobia, hyperacusis, polyuria, and diarrhea.

Exemplary dosages may range from 0.01 mg/kg to 60 mg/kg for an average adult human. However, those skilled in the art will appreciate that smaller or larger dosages are contemplated as being within the scope of the present invention. The most effective mode of administration and dosage regimen for the 9-substituted hypoxanthine derivatives as used in the methods in the present invention depend on the severity and course of the disease, the frequency of migraine attacks, the patient's health, the response to treatment, other drugs being administered and the response to them, pharmacokinetic considerations such as the condition of the patient's liver and/or kidneys that can affect the metabolism and/or excretion of the administered 9-substituted hypoxanthine derivatives, and the judgment of the treating physician. According, the dosages should be titrated to the individual patient.

The mammal can be a human or another socially or economically important mammal such as a dog, a cat, a horse, a cow, a pig, or a sheep. The method of the present invention is not limited to treatment of humans.

The method of the present invention can be used individually to treat migraine or can be used as part of combination therapy together with other agents useful in the treatment of migraine. These additional agents include analgesics or non-steroidal anti- inflammatory agents such as acetylsalicylic acid (aspirin), acetaminophen, ibuprofen, indomethacin, or naproxen sodium, ergotamine, dihydroergotamine, other ergot analogues, and sumatriptan. The dosages of these other agents can be readily determined by one of ordinary skill in the art.

Exemplary chemical syntheses for compounds useful in methods according to the present invention are presented in Examples 1-3.

The invention is illustrated by the following Examples. These examples are provided for exemplification only and are not intended to limit the invention.

8 Example 1

Condensation of 3-(6-Oxohvdropurin-9-yl) Propanoic Acid With N-Hydroxysuccinimide

As a first step in the synthesis of N-(2-(3,4-dihydroxyphenyl)ethyl)-3-(6- oxohydropurin-9-yl)propanamide, a derivative of hypoxanthine, 3-(6-oxohydropurin-9-yl) propanoic acid, was activated by condensation with N-hydroxysuccinimide (NHS). The hypoxanthine derivative, 3-(6-oxohydropurin-9-yl) propanoic acid (12.48 g) was reacted with 8.97 g of NHS and 13.62 g of the coupling agent dicyclohexylcarbodiimide (DCC) in 550 ml of dry dimethylformamide (DMF). The resulting mixture was heated with magnetic stirring in an atmosphere of argon in an oil bath (bath temperature 85-90°C) for 4 hours. The reaction mixture was used as such for the reaction of Example 2.

Example 2

Synthesis ofN-(2-(3,4-Dihydroxyphenyl)ethyl)-3-(6-Oxohvdropurin-9-yl)propanamide

The dopamine analogue N-(2-(3,4-dihydroxyphenyl)ethyl)-3-(6- oxohydropurin-9-yl)propanamide was synthesized by reacting the reaction mixture resulting from Example 1 directly with tyramine hydrochloride to form the amide link. In a flask a suspension of 14.9 g tyramine hydrochloride in 40 ml DMF was heated with 16.7 ml triethylamine with swirling and this mixture was added to the reaction mixture from Example 1. The flask was washed with another 20 ml DMF and added to the reaction mixture. Stirring and heating at 90°C (oil bath) continued. Within 15-20 minutes the reaction mixture became homogeneous. After heating for a total of 2 hours, thin-layer chromatography (TLC) was performed in 20% methanol in ethyl acetate, with visualization by ultraviolet light. The results are shown in Figure 1; the reaction mix is the third lane from the top.

The product was cooled to room temperature and then in an ice/water bath for 30 minutes. The precipitated dicyclohexylurea was filtered off. The filtrate was evaporated to dryness. The residue was heated with methanol with magnetic stirring for 2 hours, filtered, 9 and washed with methanol. The residue was heated with heated with 300 ml saturated aqueous NaHCO₃ with magnetic stirring for 30 minutes to remove any unreacted acid. The product was filtered, washed with water, and dried under vacuum at 60°C overnight. A total of 20 g of the product was recrystallized from 300 ml DMF and 200 ml acetonitrile. The recrystallization mixture was kept in the freezer overnight, filtered, washed with acetonitrile and dried at 60°C under high vacuum for 18 hours.

The yield of product was 13.4 g. Thin-layer chromatography was performed in 30% methanol in ethyl acetate with visualization by ultraviolet light. The results are shown in Figure 2, with a single spot being visualized with an Rf of 0.6; the reaction mix is the second lane from the top. The product had a melting point of 260-263°C.

Example 3

Synthesis of N-(2-Hvdroxy-2-(3,4-Dihvdroxyphenyl )ethyl-3-(6-Oxohydropurin-9- vDpropanamide

A synthesis of N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6- oxohydropurin-9-yl)propanamide was carried out as follows: A quantity (0.300 g; 0.9111 mmol) of 3-(l,6-dihydro-6-oxo-9H-purin-9-yl)propanoic acid, 4-nitrophenyl ester and (R)-(-)- norepinephrine hydrochloride (0.190 g; 0.924 mmol) were placed into a 10-ml round bottom flask with 2 ml dimethylsulfoxide and a magnetic stirring bar. Triethylamine (128 mg; 1.26 mmol) was added and the solution was stirred at room temperature for one hour. Chloroform (10 ml) was added and a copious yellow precipitate formed immediately. The solution was stirred for several minutes and was filtered by vacuum. The resulting solid was washed with chloroform and allowed to dry. After drying, 359 mg of a yellow solid, N-(2-hydroxy-2-(3,4- dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide, was obtained. The yield was about 110%. 10 Example 4

Pharmacological Activities of N-(2-Hvdroxy-2-(3,4-DihydroxyphenvD)ethyl-3-(6-

Oxohvdropurin-9-yl)propanamide

The following are the relevant pharmacological activities of N-(2-hydroxy-2- (3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide:

(1) The compound N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6- oxohydropurin-9-yl)propanamide exhibited substantial adrenergic βi antagonism of 99% at a concentration of 30 μM when tested on left atrial tissue from the guinea pig for 5 minutes. The test was performed in duplicate. An antagonism of equal to or greater than 50% was considered significant.

(2) The compound also exhibited significant inhibition of Type L calcium channels of 59% when tested on tissue from guinea pig ileum at a concentration of 30 μM for 5 minutes. The test was performed in duplicate. An inhibition of equal to or greater than 50% was considered significant.

(3) The compound also exhibited significant relief of hypoxia when tested in vivo in mice. The relief was 100%. Relief of equal to or greater than 50% was considered significant. A dose of 100 mg/kg was administered orally. Hypoxia was induced by exposure to potassium cyanide. Relief from hypoxia was determined after 60 minutes. The test was performed on 5 mice.

(4) The compound also exhibited significant leukotriene LTD₄ antagonism when tested in vitro in guinea pig ileum at a concentration of 30 μM for 5 minutes. The test was performed in duplicate. The antagonism seen was 69%. An antagonism of equal to or greater than 50% was considered significant. 11

(5) The compound also exhibited significant neurokinin NKi antagonism when tested in vitro in guinea pig ileum at a concentration of 30 μM for 5 minutes. The test was performed in duplicate. The antagonism seen was 100%. An antagonism of equal to or greater than 50% was considered significant.

The compound did not exhibit significant analgesia as measured by the phenylquinone writhing and tail flick tests in mice, did not affect anxiety as measured by the 5- MeODT potentiation test, did not display cholinergic agonism in either the central or peripheral nervous systems or cholinergic antagonism, did not affect convulsions by either the maximal electroshock or metrazole tests, did not affect depression by the behavioral or tetrabenazine hypothermia tests, did not affect motor coordination by the roto-rod test, and did not display motor stimulation. Unexpectedly, the compound also did not display dopamine agonism or antagonism, or DOPA potentiation.

Also, the compound did not exhibit either adenosine Ai agonism or antagonism, did not exhibit either adrenergic ai agonism or antagonism, did not exhibit either adrenergic α₂ agonism or antagonism, did not exhibit adrenergic βi agonism, did not affect angiotensin I activity, did not affect arachidonic acid-mediated platelet aggregation, did not affect cardiac inotropy or chronotropy, did not affect vas deferens contractility, did not exhibit activity in the potassium depolarized portal vein test or in the spontaneously activated portal vein test, did not affect thromboxane A₂-mediated platelet aggregation, did not affect cardiac arrythmia in the chloroform test, did not affect blood pressure or heart rate, and did not affect hypoxia induced by exposure to hypobaric conditions.

The compound did not affect cholesterol serum levels or levels of HDL cholesterol. The compound also did not affect renal function.

The compound further did not exhibit bradykinin B₂ antagonism, affect tracheal contractility, did not affect platelet activation factor-mediated platelet aggregation, did not display activity in the passive cutaneous anaphylaxis test, did not display histamine Hi antagonism, and did not display activity in the carrageenan-induced inflammation test. 12

Moreover, the compound did not exhibit cholecystokinin CCK_A antagonism, did not affect electrical stimulation of the ileum, did not display cholinergic antagonism in the peripheral nervous system, did not affect gastric acidity or gastric ulcers, and did not display 5-HT₃ antagonism toward serotonin-specific receptors.

Example 5

The Compound N-(2-Hvdroxy-2-(3,4-DihvdroxyphenyD)ethyl-3-(6-Oxohydropurin-9- vDpropanamide Protects Mice Against Potassium Cyanide-Induced Death

The compound N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6- oxohydropurin-9-yl)propanamide protects mice against potassium cyanide-induced death. This supports the hypothesis that this compound acts as a calcium antagonist and protects against hypoxia.

Swiss Webster mice were given the compound N-(2-hydroxy-2-(3,4- dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide, methylcellulose as a vehicle control for N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9- yl)propanamide, flunarizine as a positive control, or 2% Tween 80 as a vehicle control for flunarizine, by oral gavage, 1 hour before an intravenous injection of 2.0 mg/kg in phosphate buffered saline. Survival of the animals was monitored.

The results are shown in Figure 3. These results indicate that the compound N- (2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide protects against potassium cyanide-induced death and thus acts as a calcium antagonist. 13 ADVANTAGES OF THE INVENTION

The present invention provides new methods for the treatment of migraine in mammals, including, but not limited to humans. These methods provide a new route for treatment of migraine and can be used together with other standard methods of treatment such as analgesics, nonsteroidal anti-inflammatory agents, and other drugs such as ergotamine, ergotamine derivatives, or sumatriptan.

Although the present invention has been described with considerable detail, with reference to certain preferred versions thereof, other versions and embodiments are possible. Therefore, the scope of the invention is determined by the following claims.

Claims

14What is claimed is:

1. A method for treating migraine in a mammal comprising the step of administering an amount effective to reduce or eliminate at least one symptom of migraine of a 9-substituted hypoxanthine derivative of formula (I) to the mammal,

(I)

wherein n is an integer from 1 to 6, Ri is selected from the group consisting of H, COOH, and COOWi, where W╬╣ selected from the group consisting of lower alkyl, amino, and lower alkylamino, R₂ is selected from the group consisting of H and OH, and R₃ is selected from the group consisting of H and OH.

2. The method of claim 1 wherein the 9-substituted hypoxanthine derivative is the compound of formula (I) wherein n is 2.

3. The method of claim 2 wherein the 9-substituted hypoxanthine derivative is N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide.

4. The method of claim 2 wherein the 9-substituted hypoxanthine derivative is N-(2-(3,4-dihydroxyphenyl)ethyl)-3-(6-oxohydropurin-9-yl)propanamide. 15

5. The method of claim 2 wherein the 9-substituted hypoxanthine derivative is N-(l-carboxyl-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin-9-yl)propanamide.

6. The method of claim 1 wherein the amount of the 9-substituted hypoxanthine derivative administered is from about 0.01 mg/kg to about 60 mg/kg.

7. The method of claim 1 further comprising administering an effective amount to the mammal of at least one additional anti-migraine agent.

8. The method of claim 7 wherein the at least one additional anti-migraine agent is selected from the group consisting of acetylsalicylic acid (aspirin), acetaminophen, ibuprofen, indomethacin, naproxen sodium, ergotamine, dihydroergotamine, other ergot analogues, and sumatriptan.

9. A pharmaceutical composition comprising:

(a) an effective amount of a 9-substituted hypoxanthine derivative of formula

(I); and

(b) a pharmaceutically acceptable carrier;

O

Sr (CH₂)_n-

1

(I)

wherein n is an integer from 1 to 6, Ri is selected from the group consisting of H, COOH, and COOW_t, where Wi selected from the group consisting of lower alkyl, amino, and lower 16 alkylamino, R₂ is selected from the group consisting of H and OH, and R₃ is selected from the group consisting of H and OH; wherein the composition is formulated for treatment of migraine in a mammal.

10. The pharmaceutical composition of claim 9 wherein the 9-substituted hypoxanthine derivative is the compound of formula (I) wherein n is 2.

11. The pharmaceutical composition of claim 10 wherein the 9-substituted hypoxanthine derivative is N-(2-hydroxy-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin- 9-yl)propanamide.

12. The pharmaceutical composition of claim 10 wherein the 9-substituted hypoxanthine derivative is N-(2-(3,4-dihydroxyphenyl)ethyl)-3-(6-oxohydropurin-9- yl)propanamide.

13. The pharmaceutical composition of claim 10 wherein the 9-substituted hypoxanthine derivative is N-(l-carboxyl-2-(3,4-dihydroxyphenyl))ethyl-3-(6-oxohydropurin- 9-yl)propanamide.

14. The pharmaceutical composition of claim 9 that is formulated so that the amount of the 9-substituted hypoxanthine derivative administered is from about 0.01 mg/kg to about 60 mg/kg.