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Title:  Method of treating multiple sclerosis

United States Patent:  6,586,443

Issued:  July 1, 2003

Inventors:  Bihari; Bernard (29 W. 15th St., New York, NY 10011); Drury; Finvola (25 Colby St., Rochester, NY 14610)

Appl. No.:  312758

Filed:  September 27, 1994

Abstract

Multiple sclerosis in a human patient is treated by the administration via a pharmacologically effective route of an essentially pure opiate receptor antagonist, preferably an essentially pure opiate receptor antagonist exhibiting a substantially higher blocking effectiveness against Mu opiate receptor sites than against Delta receptor sites, exempliefied by Naltrexone and Naloxone, at a low dose concentration which produces therapeutic results corresponding to those produced by Naltrexone when administered in the range of about 1 mg to about 10 mg and at a lelel at which Delta blocking activity is small while Mu blocking activity is significant and most preferably substantially exclusive.

DETAILED DESCRIPTION OF THE INVENTION

The diseases with which the invention is particularly concerned are listed below, together with a summary description of their pertinent medical features.

CHRONIC HERPES VIRUS INFECTIONS

The important herpes virus infections are chronic genital herpes and chronic infections due to the Epstein-Barr virus (EPV). Genital herpes is a highly prevalent disease caused by the herpes simplex virus (HSV) type No. 2, transmitted from person to person by direct contact. The disease typically begins with a genital rash and mild itching which develops into vesicular lesions appearing mainly on the genitalia and adjacent body regions, which lesions can expand to an ulcerated condition, which can be accompanied by a general malaise, fever and anorexia. Neurological complications are possible but rare. The disease is often self-limiting and may disappear after a single episode or, more typically, can reoccur in milder and less frequent episodes; but for some, it can be become chronic with severe and painful episodes at weekly or monthly intervals. Such episodes can be precipitated by stress, trauma, menstrual hormone changes, etc. The chronic disease is usually associated with high levels of serum antibodies against HSV. There is presently no cure for genital herpes. Treatment with the anti-viral drug, acylovir, administered in topical form appears to limit episodic duration but does not effect a cure, prevent transmission or protect against subsequent reoccurance. Otherwise, treatment is generally palliative. Substantial risk exists for infants delivered by normal birth from infected mothers; neonatal herpes can cause brain damage and possible death.

EBV is the cause of infectious mononucleosis which occurs mainly in late adolescence and young adults by transmission of the virus through direct oral contact. Its symptoms are "flu-like" and mainly include headache, sore throat, muscle soreness, swollen glands, and general fatigue and weakness. These symptoms usually dissipage within a few weeks and treatment consists mainly of rest and curtailed activities combined with analgesic administration to relieve pain and soreness, there being no curative treatment known. Occasionally, the condition becomes recurrent or chronic which is particularly indicated by serological evidence of EBV and a significant increase in lymphocytes, with a large atypical fraction. In chronic cases, the "flu-like" symptoms may persist for a considerable period, and it is this category with which the invention is concerned.

CHRONIC INFLAMMATORY CONNECTIVE TISSUE DISEASE

The most important inflammatory connective tissue diseases are rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).

RA is an inflammatory disease affecting the connective tissue of the joints and elsewhere in patients of all ages but mainly between 20 and 40. It occurs about equally in both sexes but with a considerably higher liklihood of severity in females. It begins typically in mild form with one or more joints becoming painfully inflamed and stiff accompanied by malaise, fever and weight loss. For some the episodes may be mild and separated by lengthy remissions, but more generally the episodes become more severe and frequent in a continuing pattern of remissions and exacerbations. Its cause is unknown, and opinion is divided over whether it is due to an autoimmune reaction of the body, infection by some unidentified virus or bacteria, or an inherited genetic predisposition. The chronic form can lead to both cartilage destruction and loss of muscle control at the joint. Degenerative effects may also occur in the collagen in various bodily organs. Curative treatment is unknown; treatment is symptomatic and usually involves the administration of anti-inflammatory drugs, most commonly aspirin. The objective is mainly to achieve tolerance and acceptance by the patient with activity aimed at maintaining joint mobility.

Systemic lupus erythematosus is a chronic inflammatory disease of connective tissue throughout the body and usually appears in a pattern of remissions and acute episodes. It occurs primarily in females, mainly of childbearing age, but any age can be affected, being about eight times more prevalent in females than in males. The black race is several times more susceptible than the white race. SLE is a syndrome and can affect various organs of the body; it is usually manifested by fever, weight loss, joint pain, skin lesions and rash, Renal, cardiovascular and pulmonary complications are common. Its origin is unknown but apparently is due to an inexplicable defect in the immune system. Contributing factors include exposure to ultraviolet radiation; e.g., from sunlight, infection and hormonal effects. No treatment is known; anti-inflammatories or analgesics are given for symptomatic relief together with corticosteroids and in extreme cases immunosupressive agents,

MULTIPLE SCLEROSIS

MS is a chronic neurological disease resulting in destruction of the myelin covering of nerve cells, particularly of the brain and spinal cord. It affects men and women equally, mainly between the ages of 20 and 40. Etiological evidence is mixed. Certain evidence suggests an infectious (viral) factor since occurrence is far more common in temperate regions than in tropical regions. Other evidence suggests autoimmune involvement changes in the seriology of the autoimmune system being usually evident prior to acute attacks. Still further evidence suggests a genetic predisposition, persons of Oriental and African ancestry being generally free of the disease independently of origin of birth. Or a combination of all three could be involved in that exposure to a virus at an early age, by which most individuals are unaffected, could after a period of latency trigger in genetically susceptible individuals an autoimmune response. Symptoms of the disease include physical weakness, loss of muscular coordination, unusual burning or prickling sensation and disturbances of speech and vision, especially double vision. Diagnosis is difficult and usually requires a considerable history. For some, the disease may effectively disappear after an attack or two with no disabling consequences. More generally, there is a pattern of relapse and spontaneous remission over time with progressive neurologic disfunction, causing increasing spasticity and loss of coordination. There is no curative treatment for MS; severity of a relapse may be reduced by treatment with corticosteroids, but without apparent long term beneficial effect. Administration of immunosuppressive agents and interferon have proved ineffective. Treatment is by rest and exercise and aims mainly at diminishing the severity of the physical effects of the disease and adaptive adjustment of the patient's lifestyle.

CHRONIC FATIGUE SYNDROME

CFS has been accepted as a disease only recently and is still subject to considerable uncertainty. It occurs principally in young adults but can appear from childhood through middle age. Symptomatically, its chief characteristic is chronic debilitating fatigue persisting over many months or even years, requiring adaptive changes in lifestyle for coping and in a significant few resulting in total disability. Associated with chronic fatigue in most instances are such symptoms as sore throat, muscle pain, headache, depression, and impairment of concentration and sleep. Diagnostically, the disease is one of "exclusion" as that possibility remaining after elimination of other organic diseases with similar symptoms. Early studies found an association with high levels of antibodies against EBV, but later evidence has questioned the validity of this association, at least in terms of a casual relationship, the EBV antibody level: variations frequently lacking a statistical significance or even being within normal limits in some cases. Evidence of an immunological involvement has been reported such as changes in the "natural Killer" cell population and loss of cytotoxicity against common infectious agents but such changes are also variable to nonexistent.

Recent press reports indicate that the antiviral agent acyclovir, otherwise effective against EPV, was no more effective than a placebo in treating CFS, thus putting into question the etiological involvement of EBV in this malady.

The distinction between CFS, chronic EBV infection and/or chronic infectious mononucleosis is presently unclear. These conditions may be separate and distinct diseases or they may represent different stages of a single wide-ranging disease. There is no present treatment for CPS other than symptomatic.

Except for chronic fatigue syndrome, the above disease summaries were extracted in simplified and condensed form from The Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health by Miller and Keane, W. B. Saunders Co. 3rd Edition, April 1983, and Cecil Essentials of Medicine by Andreolin et al, W. B. Saunders Co., copyright 1986. Information for CFS was taken from the following papers to which reference may be had:

Tosato et al., Characteristic T Cell Dysfunction in Patients with Chronic Active Epstein-Barr Virus Infection (Chronic Infectious Mononucleosis), The Journal of Immunology, Vol. 134, No. 5, 3082-3088.

Straus et al., Persisting Illness and Fatigue in Adults with Evidence of Epstein-Barr Virus Infection, Annals of Internal Medicine, Vol. 102, No. 1, 7-16.

Jones et al., Evidence for Active Epstein-Barr Virus Infection in Patients with Persistent, Unexplained Illnesses; Elevated Anti-Early Antigen Antibodies, Annals of Internal Medicine, Vol. 102, No. 1, 1-7.

Caligiuri et al., Phenotypic and Functional Deficiency of Natural Killer Cells in Patients with Chronic Fatigue Syndrome, Journal of Immunology, Vol, 138, No. 10, 3306-3313.

Holmes et al., A Cluster of Patients with a Chronic Mononucleosis-like Syndrome, JAMA, Vol. 257, No. 1, 2297-2302.

Komaroff, The `Chronic Mononucleosis` Syndromes, Hospital Practice, May 30, 1987, 71-75.

Buchwald et al., Frequency of `Chronic Active Epstein-Barr Virus Infection` in a General Medical Practice, JAMA, Vol. 257, No. 17, 2303-2307

In view of the highly diverse nature of the several diseases with which this invention is concerned, it is quite unexpected that they as a group could be successfully treated by the administration, of the essentially pure opiate antagonists of the invention, especially at the extremely low dosage levels herein contemplated. RA, SLE, and MS all share an apparent common association with autoimmune action but for such action, enhancement of the natural immune function of the body, as is believed to be achieved by the invention, would seem to be directly contraindicated. Indeed, as the above discussions indicate, treatment with immunosuppressive agents has been considered as one approach in the management of these diseases. As regards herpes infections, to the extent that a chronic state of infection might indicate an impairment of the immune function of the body, it is nonetheless surprising that the treatment of the invention could induce such a significant improvement in immune function as to actually prove efficacious for these diseases.

The therapeutic agents useful in the present method are the essentially pure opiate antagonists. It is generally accepted that drugs exert their characteristic physiological action in the body by interacting or complexing with certain so-called receptor sites existing in cells in the brain and elsewhere. An opiate antagonist has the capability of interacting with those specific receptor sites which are sensitive to opiate or narcotic drugs, and so long as such interaction persists and of thereby blocking such receptor sites from any additional interaction with the opiate drugs and in this manner preventing the opiate drugs from exerting their characteristic analgesic and euphoric action on the body. These opiate antagonists which do not exert any physiological action of their own are deemed essentially pure and are suitable for purposes of this invention. The great majority of drugs found to possess antagonist action also exert a significant agonist action and are referred to as "mixed agonist/antagonists". Such mixed agonist/antagonists are not suitable for use in the present method which requires essential purity in the antagonist effect.

There appear to be several different kinds of receptor sites that are sensitive to opiates or narcotics, perhaps five or so, and the important sensitivity is possessed by those identified as Mu and Delta receptor sites. The Mu receptor sites have particularly strong affinity for opiate drugs and produce a correspondingly strong physiological (agonist) reaction upon interaction with such drugs. Blockage of the Mu receptor sites is hence an important objective of the invention. Any essentially pure opiate antagonist is effective in blocking Mu receptor sites and thus would be advantageous to at least some extent for achieving the the therapeutic results of this invention.

Delta receptor sites, on the other hand, appear to contribute to an effectively functioning immune system when unblocked. It is, therefore, preferred to select an essentially pure opiate antagonist which possesses a preferential blocking action for Mu receptor sites over Delta receptor sites in order to leave the latter in unblocked condition. Such preferential blocking action of Mu sites over Delta sites may be dosage related; that is, a particular antagonist can have an effectively stronger blocking action for Mu sites than for Delta sites at a given dosage range; whereas at higher levels, the amount may be enough to block both sites in substantial entirety. By appropriate selection of the dosage level, one can achieve with a given antagonist, a significant and valuable blocking action against Mu receptor sites while maintaining the blocking action against Delta sites at appreciably lower levels at which the blocking effect on the Delta sites is minor or at least inconsequential. If increasingly higher dosages were to be employed, then ultimately both Mu and Delta sites would both become blocked, which is less advantageous in therapeutic results and preferably to be avoided. However, by judicious adjustment of the dosage level, one can take advantage of the differential between the Mu blocking and Delta blocking capabilities and achieve an effective blocking of Mu sites with only minimal blocking of the Delta sites which is optimum for therapeutic purposes.

Naltrexone and naloxone are both essentially pure opiate antagonists which also exert strong preferential blocking action against Mu over Delta sites, the Mu blocking action being generally rated at about ten times the Delta blocking action. Both of these drugs are presently commercially available and are, so far as is known, the only essentially pure opiate antagonists which have received governmental approval for administration to humans. Both of these drugs can be employed in the practice of this invention with naltrexone being the preferred choice. If other essentially pure opiate antagonists, preferably those exerting significant preferential action against Mu over Delta receptors, become available and receive government approval, such drugs, at least in principle, qualify for application in the present method.

The therapeutic agent should obviously be administered by a pharmacological mode or route of administration which is effective for the particular drug. Naltrexone can be administered effectively orally; i.e., in the form of tablets, capsules, caplets, powder, a powdered suspension or solution in a suitable liquid carrier or the like. It is not available in a form suitable for administration by injection. On the other hand, naloxone has not proved to be effective when administered orally at least at dosage levels which would be practical and appropriate in this invention. It is, however, available in forms suitable for administration by injection and can be applied by this mode in the invention if desired. Generally, oral administration is preferable from the standpoint of simplicity and convenience and naltrexone is thus the preferred choice. However, for those patients for whom oral administration is not permissible, administration of naloxone by injection, either intravenously, intramuscularly, or subcutaneously, is an alternative.

The useful dosage range, at which Mu receptor sites are substantially blocked while the Delta sites are substantially unblocked, for naltrexone is about 1-10 mg/day daily. The limits of this range are not critical but below about 1 mg the therapeutic effect is quite small, while at levels several times above 10 mg, at which these drugs have been generally administered in the past for other purposes, especially narcotic addiction, the effects of the preferential blocking action against Mu over Delta receptor sites disappears, since the amount of the drug is large enough to cause at least substantial blocking of Delta sites while the Mu sites remain fully blocked. A preferred range for naltrexone is about 1.5-3.0 mg/day daily,

The dosage levels for naloxone and any other essentially pure opiate antagonist that might become available in the future are to be determined with reference to the above-specified dosage ranges for naltrexone. That is, the dosage level for naltrexone or any new essentially pure opiate antagonist should be such as to produce an antagonist effect which corresponds or is equivalent to that produced by naltrexone at the range of about 1-10 mg/day. Such equivalent amounts can be readily determined for other opiate antagonists. Morphine is well recognized as a classical Mu agonist, and other antagonists than naltrexone can be readily standardized against morphine to quantify the amounts thereof that are equivalent to the effective dosage for naltrexone, For example, by means of tests evaluating the response of rats or mice, e.g., the "tail flick" test, that amount of morphine which is offset or counteracted in its narcotic dependency effect by a given amount of naltrexone can then be tested against other antagonists to determine the specific amount of the latter which is necessary to produce the equivalent antagonist action against morphine as the naltrexone. For further information concerning such tests, reference may be had, for example, to the text Principles of Drug Action: The Basis of Pharmacology, Goldstein et al, second edition, copyright 1974, John Wiley & Sons, at pages 604-609 in particular.

Claim 1 of 5 Claims

What is claimed is:

1. A method of treating humans suffering from multiple sclerosis, which comprises the step of administering by a pharmacologically effective mode to such patient a therapeutically effective dose of a therapeutic agent consisting essentially of an essentially pure opiate receptor antagaonist, the amount of said dose being selected to produce therapeutic results substantially corresponding to those produced by Naltrexone when administered in the range of about 1 mg to about 10 mg.




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