METHOD FOR THE TREATMENT AND/OR PREVENTION OF RADIATION BURN

Abstract: A method for the therapeutic treatment or prevention of radiation-induced skin damage, particularly ultraviolet-induced skin burn (e.g., sunburn), in which an alpha-hydroxy acid, or a derivative thereof, is topically applied to the affected skin areas. Glycolic acid is employed in a preferred embodiment.

Description: METHOD FOR THE TREATMENT AND/OR PREVENTION OF RADIATION BURN BACKGROUND OF THE INVENTION The present invention relates to the topical appli- cation to the skin of active agents, and/or preparations containing them, for the treatment and/or prevention of radiation damage to the skin, and particularly for the treatment of skin which has received excessive exposure to ultraviolet radiation, as in the case of sunburn. Ultraviolet induced burning of the skin is most com¬ monly seen in persons who have been excessively exposed to natural sunlight (i.e., sunburn), but also can be seen in persons who have been excessively exposed to ultraviolet radiation from non-sunlight (artificial) sources, as may occur in tanning booths or incident to application of ultra¬ violet radiation as part of a therapeutic treatment. Cuta¬ neous burn and other forms of skin damage also can arise from excessive or prolonged exposure to other forms of radiation outside the ultraviolet spectrum. The clinical manifestations of ultraviolet induced burn seen in acute reactions is attributed to ultraviolet radiation in the range of 290 - 320 nanometers, generally designated ultraviolet B (UVB) radiation, although pro¬ longed exposure to longer wavelength ultraviolet A light -2- (-320 - 400 nanometers) can produce mild burn and marked hyperpigmsntation. , The sunburn reaction is a complex inflammatory pro¬ cess causing dyskeratotic cells, spongiosis, vacuolation of kertj;i*nocytes and edema,from capillary leakage, 12 to 24 hours after exposure to light. In addition to redness and pain, blisters may evolve. Chronic effects of UV light in¬ clude degenerative changes of the skin which can lead to premalignant and malignant growths of the skin and degenera- tion of the dermal collagen. The detrimental effects of sunburn have been postu¬ lated to be related to a transfer of energy from ultra¬ violet radiation to the skin, resulting in generation of excited oxygen species, such as singlet oxygen, the super- oxide anion, and hydroxyl radicals that can damage lipid- rich membranes with the subsequent activation of the chemi¬ cal mediators of inflammation. It is well known that ultra¬ violet B radiation releases arachidonic acid, which is quickly oxidized to a variety of biologically active meta- bolites, such as prostaglandins PGD2, PGE2, PGEF2. When arachadonic acid is oxidized via the cyclo-oxygenase path¬ way, prostaglandins create marked erythema. Arachadonic acid oxidized via the 5-lipo-oxygenase pathway produces leukotrienes, which also can cause erythema and edema. The free radicals created by ultraviolet radiation can also damage the DNA of the cells, resulting in permanent injury, premature aging, and carcinogenesis. The clinical symptoms of ultraviolet burn are on a spectrum from mild increased sensitivity of the skin to severe pain. It should also be noted that damage to skin can be caused by other forms of radiation, that is, ioniz¬ ing radiation as well as longer wave length radiation such as infrared, which can result in erythema and pigmentation -3- as well as prem turs agir»g and malignancy. These other forms of radiation create damage by the same mechanism, i.e., generation of free radicals with subsequent damage to the cell membrane and DNA. Suggestions for dealing with sunburn and other forms of ultraviolet radiation burn have predominantly been aimed at prevention rather than treatment. Several topical sun¬ screens have been developed, and have proved to be very effective in preventing sunburn and long-term photo-damage. However, these agents must be used prior to ultraviolet exposure in order to exert their protective effect. The primary object of this invention is to provide a treatment for radiation skin burn, particularly ultraviolet skin burn, and most particularly sunburn, and more parti- cularly to provide a therapy based upon topical application to affected skin areas of an active agent or precursor thereof, preferably in association with a dermatologically acceptable carrier or vehicle. SUMMARY OF THE INVENTION in accordance with the present invention, a thera¬ peutic method for the treatment of radiation-induced skin damage is provided, which comprises topical application to the affected skin sites of an effective amount of one or more alpha-hydroxy acids or derivatives thereof. In the preferred practice of the invention, the alpha-hydroxy acid (or derivative) is applied in admixture with a dermatologically acceptable carrier or vehicle (e.g., as a lotion, cream, ointment, soap, or the like) so as to facilitate topical application and, in some cases. -4- provide additional therapeutic effects as might be brought about, e.g., by moisturizing of the affected skin areas. Preferred alpha-hydroxy acids are organic acids having an aliphatic backbone of up to 5 carbons to which is attached a single hydroxyl group (other than that asso¬ ciated with the carboxyl moiety) on the alpha-carbon atom, and may contain one or two additional carboxyl groups. Especially preferred are alpha-hydroxy monocarboxylic acids, particularly glycolic acid. The amount of the alpha-hydroxy acid or derivative thereof (hereinafter referred to collectively as hydroxy acid for ease of reference) necessary to bring about the therapeutic treatment of radiation-induced skin damage is not fixed per se, and necessarily is dependent upon the severity and extent of the condition, the identity and form of hydroxy acid employed, and the concentration of the hy¬ droxy acid when employed in association with a carrier. Generally, the hydroxy acid or composition containing it is topically applied to the affected skin areas in a predeter- mined or as-needed regimen to bring about improvement, it generally being the case that gradual improvement is noted with each successive application. Insofar as has been determined based upon clinical studies to date, no adverse side effects are encountered. DETAILED DESCRIPTION OF THE INVENTION This invention describes methods for the prevention and treatment of radiation-induced skin damage, parti¬ cularly sunburn, by the topical application of alpha- hydroxy acids or alpha-hydroxy acid derivatives to affected skin areas. -5- As used herein, the terminology "alpha-hydroxy acid" has reference to and encompasses the general class of or¬ ganic compounds containing at least one hydroxy group and at least one carboxyl group, and wherein at least one hy- droxyl group is located on the alpha-carbon atom. Typi¬ cally, the compounds are organic acids having at least one carboxylic acid group and at least one hydroxyl group on the alpha-carbon atom, and may contain other functional groups including additional hydroxyl and carboxylic acid moieties. Most typically, alpha-hydroxy acids will have a basic structure of lower aliphatic compounds having from two to six carbon atoms. The "derivatives" of these alpha-hydroxy acids most typically will involve derivatives related to the carboxyl functionality, i.e., wherein the hydrogen or hydroxyl por¬ tion of the carboxyl moiety is substituted by metallic ions (to form salts) , alkoxy groupings (to form esters) , ammo¬ nium ions (to form ammonium salts) , as well as other substi¬ tution reactions and products leading to formation of cor- responding lactones, anhydrides or amines. However, the derivatives may also include reactions involving the alpha- hydroxy1 group, most notably ketone formation, to form corresponding alpha-keto carboxylic acids. Among the hydroxy acids and derivative compounds useful in the present invention are hydroxy monocarboxylic acids such as glycolic acid, hydroxymethylglycolic acid, lactic acid, glucuronic acid, galacturonic acid, gluconic acid, glucoheptonic acid, alpha-hydroxybutyric acid, alpha-hydroxyisobutyric acid, alpha-hydroxyvaleric acid, alpha-hydroxyisovaleric acid, alpha-hydroxycaproic acid, and alpha-isocaproic acid. Also included are di- and tri-carboxylic hydroxy acids such as tartronic acid, tartaric acid, malic acid, hydroxyglutaric acid, hy- droxyadipic acid, hydroxypimelic acid, muric acid, citric -6- acid, isocitric acid, saccharic acid, dihydroxymaleic acid, dihydroxytartaric scid. and dihydroxyfumaric acid. Deri¬ vatives involving keto groups include keto acids and keto esters such as pyruvic acid, methyl pyrivate, ethyl pyru- vate, isopropyl pyruvate, benzoylformic acid, methyl ben- zoylformate, and ethyl benzoylformate. Hydroxy acids and their derivatives have varying degrees of solubility in water, organic solvents, oils and the like. Since topical application to affected sites of radiation-induced skin damage according to the invention requires that the. active ingredient be in a form permitting such use, it generally will be the case that the hydroxy acid or precursor or derivative thereof be employed in asso¬ ciation with a carrier, and particularly one in which the active ingredient is soluble per se or is effectively solubilized (e.g., as an emulsion or microemulsion) . It is necessary that the carrier be inert in the sense of not bringing about a deactivation of the hydroxy acid or derivative, and in the sense of not bringing about any adverse effect on the skin areas to which it is applied. Suitable carriers include water, alcohols, oils and the like, chosen for their ability to dissolve or disperse the active ingredient at concentrations of active ingre¬ dient most suitable for use in the therapeutic treatment. Generally, even low concentrations of active ingredient in a carrier will be suitable, requiring only that more frequent topical application be resorted to. As a prac¬ tical matter, however, to avoid the need for repeated application, it is desirable that the topically applied composition (i.e., hydroxy acid or derivative plus carrier) be formulated to contain at least about 0.5% by weight, more preferably at least about 2% by weight, and most preferably at least about 8 to 10% by weight, of the active ingredient, and accordingly, carriers will be chosen which -7- can solubilize or disperse the active ingredient at such concentrations. While the carrier for the hydroxy acid or derivative of hydroxy acid can consist of a relatively simple solvent or dispersant such as water or oils, it is generally pre¬ ferred that the carrier comprise a composition more condu¬ cive to topical application, and particularly one which will form a film or layer on the skin to which it is ap¬ plied so as " to localize the application and provide some resistance to washing off by immersion in water or by pers¬ piration and/or aid in the percutaneous delivery of the active agent. Many such compositions are known in the art, and can take the form of lotions, creams, gels or even solid compositions (e.g., stick-form preparations). Typi- cal compositions include lotions containing water and/or alcohols and emollients such as hydrocarbon oils and waxes, silicone oils, vegetable, animal or marine fats or oils, glyceride derivatives, fatty acids or fatty acid esters or alcohols or alcohol ethers, lecithin, lanolin and deriva- tives, polyhydric alcohols or esters, wax esters, sterols, phospholipids and the like, and generally also emulsifiers (nonionic, cationic or anionic) , although some of the emol¬ lients inherently possess emulsifying properties. These same general ingredients can be formulated into a cream rather than a lotion, or into gels, or into solid sticks by utilization of different proportions of the ingredients and/or by inclusion of thickening agents such as gums or other forms of hydrophillic colloids. Such compositions are referred to herein as dermatologically acceptable carriers. As noted, the hydroxy acid is provided in the form of the acid per se or in the form of a derivative. Exemplary compounds include the simple ionic salts (e.g., for glyco- lic acid, sodium glycolate, calcium glycolate, potassium -8- glycolate, magnesium glycolate), fatty acid esters (e.g., lauryl glycolate, myristyl glycolate, palmityl glycolate, stearyl glycolate), anhydrides, or other chemical rH=riv-»- tives which preserve or provide the effective acid compound upon dissolution or dispersion in a carrier or upon topical application. The most preferred compounds are low mole¬ cular weight alpha-hydroxy carboxylic acids having an ali¬ phatic backbone of 2 to 5 carbons such as glycolic acid. In order to demonstrate the efficacy of alpha-hydroxy acids in treatment of radiation skin burn, a composition containing about 8% glycolic acid in an oil-in-water cream was prepared. Five test subjects were employed in the stu¬ dy, using their forearms as test sights. The test sights were covered with paper, with two windows 3 cm in diameter exposed on each forearm. These were then irradiated using a high pressure mercury halide lamp with 3 times the ery¬ thema dose (MED) of UVB irradiation. Upon the appearance of erythema (6 to 10 hours after irradiation) , the glycolic acid composition was applied to one lesion of each forearm, and a control oil-in-water cream containing no glycolic acid was applied to the other. After 24 hours from the time of application, erythema in the treated areas had decreased as compared to the control areas to which only the oil-in-water cream (containing no glycolic acid) had been applied. After 72 hours, the glycolic acid-treated areas exhibited only hyperpigmentation, whereas the control areas exhibited marked erythema as well. The subjects all reported marked reduction in symptoms of burn on the areas treated with active ingredient. Use of glycolic acid solubilized in an oil-in-water cream form is greatly preferred in the method of this in¬ vention for a variety of reasons. Glycolic acid is a small molecule, generally permeable to plasma membranes. In this carrier, the acid is better able to penetrate the skin. -9- allowing the active ingredient to be released in a fat-solu¬ ble environment. Also, in this form the hydroxy acid can be solubilized in a fat-soluble base (cream, lotion, etc.) which aids in skin penetration. Still further, this form of hydroxy acid is less prone to oxidative breakdown (and particularly so when further admixed in a fat-soluble base) , and thus is capable of being made up as a stable preparation having a suitably long shelf-life and which has prolonged effectiveness after being applied to the skin. The mode by which the alpha-hydroxy acids and deriva¬ tives are effective in treatment and prevention of sunburn as described herein is not particularly well understood, but may be related to the anti-oxidant properties of the active compounds and/or their interference with chemical reactions. It should also be noted that alpha-hydroxy acids and certain derivatives thereof have in the past been taught for preventing disorders of hyperkeratinization as well as other uses related to skin problems. See, for example, U.S. Pat. Nos. 3,920,835, 4,105,782, 4,197,316, 4,234,599, 4,380,549, and 5,091,171. While sunburn may have associated with it a component of hyperkeratosis, it is, if present, quite minimal in most cases as compared to other causes and effects of the problem, and accordingly the activity and effectiveness of the alpha-hydroxy acids and derivatives in the present invention is not apparently related to effectiveness in treating hyperkeratinization disorders. In terms of a possible explanation for the effec¬ tiveness of alpha-hydroxy acids in the treatment of ra- diation damage to the skin, it is noted that certain preferred hydroxy acids are anti-oxidants which can sca¬ venge free radicals such as the oxygen radicals created by exposure of cells to radiation, as well as the generation of free radicals produced by normal metabolism extra- -10- cellularly and intracellularly. Certain of the hydroxy acids sequester metals, and may be involved in deactivation of the heme-containing dioxygenase that produces prosta- glandin precursors in the endoplasmic reticulum. The plas- ma membranes of most cells are highly permeable to small- sized alpha-hydroxy acids such as lactate and pyruvate, and these may play a role in affecting the activity of prosta- glandin production, e.g., by depressing prostaglandin cyclo-oxygenase where these compounds are employed in the method of the invention. Cyclo-oxygenase is a key enzyme in the oxidation of arachadonic acid, which leads the formation of prostaglandins which in turn mediates inflam¬ mation. The method of the present invention is particularly useful for the treatment of skin which has been damaged by exposure to ultraviolet radiation, but, based upon the likely mechanism of action, also is useful in general for treatment of any radiation-induced skin damage, particu¬ larly that associated with free radical related damage. As such, the topical application of alpha-hydroxy acid accor¬ ding to the invention can also be effective for chronic administration to prevent the free radical damage seen in the natural aging process of the skin and the free radical damage caused by chronic exposure to sunlight. The hydroxy acid can thus be added to commercial suncreens to enhance their anti-aging and anti-cancer activity. It can also be applied prior to sun exposure for added protection against burn. Having described the invention with reference to particular compositions, theories of effectiveness, and the like, it will be apparent to those of skill in the art that it is not intended that the invention be limited by such illustrative embodiments or mechanisms, and that modifi¬ cations can be made without departing from the scope or spirit of the invention, as defined by the appended claims.

Claims: -11- CLAIMS 1. A method for the treatment of radiation-induced skin damage, said treatment comprising topically applying to the affected skin areas an effective amount of an active com¬ pound selected from the group consisting of alpha-hydroxy acids, derivatives of alpha-hydroxy acids, and mixtures thereof. 2. A method according to claim 1 wherein the alpha-hydroxy acid is a monocarboxylic acid. 3. A method according to claim 1 wherein the alpha-hydroxy acid has an aliphatic backbone of 2 to 3 carbons. 4. A method according to claim 1 wherein the compound is glycolic acid. 5. A method according to claim 1 wherein the compound is provided in association with a dermatologically acceptable carrier. 6. A method according to claim 5 wherein the combination of the compound and the carrier is in a form selected from the group consisting of solutions, dispersions, creams, lotions, gels and solid sticks. 7. A method according to claim 6 wherein the carrier is an oil-in-water cream. 8. A method according to claim 7 wherein the combination comprises about 2 to about 10% by weight glycolic acid. 9. A method according to claim 8 comprising about 8% by weight glycolic acid. -12- 10. A method for the treatment of radiation-induced skin daisags, s il, treatment comprising topically applying to the affected skin areas an effective amount of a composition comprised of glycolic acid in association with a dermato¬ logically acceptable carrier. 11. A method for the prevention of radiation-induced skin damage, said method comprising topically applying to ex¬ posed skin areas an effective amount of an active compound selected from the group consisting of alpha-hydroxy acids, derivatives of alpha-hydroxy acids, and mixtures thereof. 12. A method according to claim 11 wherein the active com¬ pound is glycolic acid. 13. A method according to claim 11 wherein the active com¬ pound is provided in association with a dermatologically acceptable carrier. 14. A method according to claim 13 wherein the active com¬ pound is a component of a sunscreen preparation. 15. A method according to claim 12 wherein the compound is provided in association with a dermatologically acceptable oil-in-water cream.

Inventors: PERRICONE NICHOLAS V, PERRICONE, NICHOLAS, V.
Applicants: PERRICONE NICHOLAS V, PERRICONE, NICHOLAS, V.
Application year: 1992
Main classification: A61K7
IPC codes: A61K8, A61K9, A61K31, A61Q17, A61Q19