Abstract:
A topical composition for the treatment of acne and other dermatological conditions comprises a liposomal formulation of a retinoid and an antibiotic in which the retinoid is disposed in the lipid phase of the formulation, and the antibiotic is disposed in the aqueous phase. Lincosamides, such as clindamycin, are one group of antibiotics which may be used in the composition. Tretinoin is one preferred retinoid. Also disclosed are methods for making the compositions and methods for using the composition.

Description:
RELATED APPLICATION 
       [0001]    This patent application claims priority of U.S. patent application Ser. No. 10/425,359, filed Apr. 29, 2003 and U.S. Provisional Patent Application Ser. No. 60/377,002 filed Apr. 30, 2002, both entitled “Composition and Method for Dermatological Treatment”. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to the treatment of skin conditions such as acne. More specifically, the invention relates to dermatological compositions based upon liposomal formulations of retinoids and antibiotics, and their use for the treatment of acne. 
       BACKGROUND OF THE INVENTION 
       [0003]    Acne is a dermatological disorder which occurs when inflamed sebaceous glands become blocked with sebum, skin cells and bacteria. Lesions occur in more superficial forms as open or closed comedones, as well as in deeper varieties such as nodules and cysts. Acne tends to appear at the onset of puberty and persists into early adulthood. One reason for the association of acne with puberty is that sebum levels are under hormonal control. While not usually physically disabling, acne can be particularly disturbing for cosmetic reasons to those affected. In addition, untreated or inappropriately treated acne can result in permanent, disfiguring scarring. 
         [0004]    One approach to the treatment of acne relies upon the systemic administration of antibiotics and/or isotretinoin. Antibiotics such as tetracycline have been given orally to target bacteria associated with the skin such as  Propionibacterium  acnes. However, systemic administration has the drawback of affecting all areas of the body and disrupting endogenous flora not involved in acne and producing side effects such as nausea and diarrhea. Isotretinoin is a highly effective systemic anti-acne agent which is given in cases of severe acne. However, isotretinoin has significant side effects and is contraindicated for women of childbearing age. Consequently, such systemic therapies are of somewhat limited utility; therefore, there is a need for effective topical therapies. 
         [0005]    A variety of topical acne therapies have been proposed and utilized. These therapies are usually fairly adequate for relatively mild cases of acne; however, they are often inadequate for relatively severe cases. Prior art topical therapies generally relied upon various combinations of antibiotics and/or retinoids together with organic peroxides such as benzoyl peroxide and anti-inflammatory compositions such as corticosteroids. The utility of prior art compositions has been limited by a number of factors. Oftentimes materials employed in such compositions are not mutually compatible in a common carrier or vehicle; hence problems of oxidation, phase separation or chemical degradation may occur and can affect the shelf life and efficacy of such materials. In some instances, combination therapies are employed wherein separate topical compositions are applied to a patient or combinations of oral and topical therapy are implemented. Prior art topical compositions have also been found to be overly drying or otherwise irritating to a patient&#39;s skin. All of these factors have limited the use of prior art topical compositions. 
         [0006]    As will be explained in greater detail hereinbelow, the present invention is directed to a topical composition for the treatment of dermatological conditions. While the composition of the present invention has significant and primary utility in the treatment of acne, it can also be employed for other dermatological conditions including conditions in which microbial infection is a factor, as well as noninfective conditions such as rosacea. The compositions of the present invention are based upon a liposomal structure in which a discontinuous, lipid phase material is dispersed in a continuous, aqueous phase material, which is most preferably a thickened or gelled aqueous phase material. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    There is disclosed herein a topical composition for the treatment of skin conditions. The composition includes a liposomal vehicle comprising a discontinuous, lipid phase dispersed in a continuous, aqueous phase. An antibiotic is disposed in the aqueous phase and a retinoid is disposed in the lipid phase. The retinoid is, in particular embodiments, tretinoin. The antibiotic is, in particular compositions, a lincosamide antibiotic, with clindamycin being one particular lincosamide having utility in this invention. 
         [0008]    In particular embodiments, the retinoid component is present in a range of 0.04-1.0% by weight. In particular instances, the retinoid is present in an amount of 0.03-0.75% by weight, and in some specific compositions the retinoid is present in an amount of 0.05-0.065% by weight. The composition may include further ingredients such as emollients, antioxidants, surfactants, thickeners, gelling agents, pH control agents, solvents, carriers, dispersion agents, fragrances and colors. 
         [0009]    Also disclosed herein is a method for using the composition for treating acne and other skin conditions, as well as methods for the manufacture of the composition. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    The present invention provides compositions and methods for the topical treatment of acne. The compositions are formulated as a liposomal preparation having an aqueous or continuous phase containing an antibiotic as well as a lipid phase which contains a retinoid. The composition may also include a carrier or dispersion medium, a solvent, an emollient, an antioxidant a surfactant, a thickener or gelling agent and a pH stabilizer, as well as coloring agents, fragrances and the like. 
         [0011]    One specific composition includes tretinoin as a retinoid, preferably at a concentration ranging from 0.01-1.0% w/w. More preferably, tretinoin is included at a concentration ranging from 0.04-0.075% w/w. In one preferred preparation, tretinoin present at 0.05-0.65% w/w. In another preferred composition, tretinoin is present in the range of 0.05-0.065% w/w. 
         [0012]    An antibiotic of the lincosamide class is one preferred type of antibiotic used in a composition according to the invention, and clindamycin is one specific lincosamide having utility in this invention. In particular, clindamycin phosphate is found to be especially effective and is one preferred ingredient of the inventive composition. Clindamycin phosphate is included at a concentration ranging from 0.5-10% w/w (calculated as clindamycin base), but is preferably included at a concentration ranging from 0.75-2.0% w/w (calculated as clindamycin base). Clindamycin may also be included as a free base or other suitable salt, including for example, clindamycin HCl. 
         [0013]    In the broadest sense, the compositions of the present invention are based upon liposomal formulations comprising a discontinuous, lipid phase which includes the retinoid, and which is dispersed in a continuous, aqueous phase, which includes the antibiotic. The multiphase nature of the material of the present invention has been found to greatly enhance the stability and therapeutic efficacy of the compositions. 
         [0014]    As is known in the art, liposomal materials comprise vesicles of the lipid phase dispersed throughout the aqueous phase. Typically, the walls of the vesicles are comprised of a phospholipid material such as phosphatidyl choline. One such material is available from the American Lecithin Corporation under the designation Phospholipion®. As is known in the art, the lipid phase may include stabilizing materials such as cholesterol as well as surfactants, antioxidants and the like. The aqueous phase of the material may be based upon an aqueous solution of the antibiotic. However, in specifically preferred embodiments, this phase is thickened or gelled with art known, compatible thickenings agents such as Carbopol® water-soluble, acrylic resins. Compositions in accord with the present invention may also include ancillary ingredients such as emollients, antioxidants, surfactants, pH control agents, additional solvents, additional carriers, dispersion agents, coloring agents, fragrances and the like. These ancillary ingredients may be added to either or both of the phases. Carriers and dispersion media are known and will be recognized as suitable by one of ordinary skill in the art. Propylene glycol is one particularly preferred carrier which may be used in a topical treatment composition of the present invention. Solvents useful in dissolving tretinoin or clindamycin independently for use in preparing compositions according to the present invention are known in the art and illustratively include benzyl alcohol, propylene glycol, water, art recognized equivalents and mixtures thereof. 
         [0015]    Emollients are well known in the preparation of topical formulations, and a suitable choice for inclusion in a composition of the present invention will be recognized as such by one of skill in the art. Illustrative examples include hydrocarbons such as C8-C30 saturated or unsaturated fatty acids or alkyl esters of fatty acids, such as isopropyl myristate; sterols such as cholesterol and derivatives thereof; mixtures of emollients; and art recognized equivalents. 
         [0016]    An antioxidant suitable for inclusion in an inventive composition includes any of those recognized in the art illustratively including ascorbic acid, BHT, BHA, a carotenoid, a tocopherol such as vitamin E acetate, a flavinoid, a glutathione. An antioxidant may be used independently or more than one may be used in an inventive composition. 
         [0017]    A surfactant may be cationic, anionic, amphoteric, or nonionic or mixtures thereof. A non-ionic surfactant such as polysorbate 80 or an art recognized equivalent is preferred for use in an inventive topical treatment composition. 
         [0018]    A composition according to the present invention includes a thickener or gelling agent such as Carbopol 980NF acrylic resin or an art recognized equivalent. A neutralizer may be added following dispersion of the thickener. For example, triethanolamine or an art recognized equivalent is useful in neutralizing an inventive composition. 
         [0019]    Liposomes are a particularly preferred component of a topical treatment for acne. A composition including a liposomal gel preparation of the present invention has the advantages of containing skin-compatible ingredients, such as emollients, lipids and antioxidants, capable of soothing and promoting healing in damaged skin in an acne affected area without irritation. In addition, a liposomal gel preparation has the advantage of allowing delivery of hydrophilic, hydrophobic and amphipathic therapeutic agents since the preparation contains a lipid phase and an aqueous or continuous gel phase. The distribution of a therapeutic agent in a liposome will depend on numerous factors, such as, for example, characteristics of drug solubility, concentration of the drug, components of the liposome and the method of liposome preparation. Examples of known methods of liposome preparation are described in  Liposomes: A Practical Approach , R.R.C. New, Editor, Oxford University Press, 1990, 1997. 
         [0020]    Particularly preferred in the present invention is a liposomal gel preparation including an antibiotic in the aqueous or continuous phase and a retinoid in a lipid phase. Especially preferred is a liposomal gel preparation having clindamycin phosphate concentrated in the aqueous or continuous phase and tretinoin present in a lipid phase. While the compositions of this invention are described as having the retinoid contained in the lipid phase, it is to be understood that some portion of the retinoid may partition into the aqueous phase. Such compositions are within the scope of this invention. Preferably, compositions of the present invention have a majority of the retinoid contained in the lipid phase. In specifically preferred embodiments, at least 80% w/w of the retinoid is in the lipid phase, and in particular embodiments, 80-90% w/w of the retinoid is in the lipid phase. Disposing the retinoid in the lipid phase avoids problems of toxicity and the like which have heretofore limited the utility of retinoids. 
         [0021]    The compositions of the present invention are used as topical agents for the treatment of acne and other skin conditions. Typically, they are applied to affected areas 1-3 times per day. It is generally preferred that the skin be cleaned with a mild cleanser prior to the application of the composition. 
         [0022]    A method of making a liposomal gel preparation according to the present invention includes generating two phases, a lipid phase A including a retinoid and a gel dispersion phase B including an antibiotic. Phases A and B are mixed, resulting in the final preparation. Specific examples of inventive compositions and methods are described below. 
       EXAMPLES 
     Example 1 
       [0023]    An example formulation and method of preparation of a retinoid/antibiotic acne treatment composition: 
         [0024]    A formulation according to the present invention is prepared in two phases, a lipid phase A and a gel dispersion phase B. The lipid phase preparation A is prepared by dissolving a retinoid in a solvent or a carrier. Preferred solvents are water-miscible materials, such as alcohols, esters, ethers and ketones. Such materials need not be infinitely soluble in water, but they should have some solubility; typically at least 10%. Following dissolution of the retinoid, oil phase materials including emollients, antioxidants and surfactants are added and mixed over gentle heat if necessary to achieve a uniform solution. Typically the material is heated to a temperature between 40° to 60° centigrade and mixed, as for example, with an anchor mixer at speeds of approximately 40 to 100 rpm. When the oil phase materials have melted, phospholipids are added to the mixture and gently agitated to achieve a solution without lumps. Again, gentle heating may be applied, usually in a range from 40° to 80° centigrade. Lipid phase preparation A is then mixed under light vacuum, for instance from about 10 to 30 inches of mercury (in-Hg) for a time sufficient to achieve a uniform preparation, typically ranging from 30 to 60 minutes using an anchor mixer at a speed ranging from 50 to 100 rpm. Preparation A is then cooled, for example, cooled to room temperature over a period of 90 minutes using an anchor mixer mixed on a water-circulating bath mixer under a low vacuum. 
         [0025]    Preparation b is made by dissolving an antibiotic in a carrier. A thickener or gelling agent is slowly added into the antibiotic mixture and continuously stirred until a uniform and lump-free dispersion is achieved. Preparation B is then added to Preparation A and mixed. The resulting preparation is then mixed in a mixer/emulsifier and disperser under vacuum beginning as low as possible and climbing to a range of approximately 20 to 30 in-Hg for a time sufficient to achieve a uniform dispersion. After that time, the vacuum may be released and the product scraped from the agitators followed by a second mix step in a mixer/emulsifier and disperser under vacuum beginning as low as possible and climbing to a range of approximately 20 to 30 in-Hg for a time sufficient to achieve a smooth gel having a uniform dispersion. The resulting uniformly dispersed smooth gel has a liposome structure and very little or no crystalline structure when examined microscopically. 
         [0026]    In other variants of this process, Preparation A is mixed with water prior to being mixed with Preparation B. This mixing creates the liposomal structure in Preparation A, and this liposomal structure is then blended with Preparation B. 
       Example 2 
       [0027]    An example formulation of tretinoin 0.05%/clindamycin phosphate 1% acne treatment composition. 
       Procedure 
       [0000]    
       
         Step 1. Weigh ingredients to be used. In this example, ingredients are included at percentages shown in Table 2 below. 
         Step 2. Start water circulation in a temperature-controlled homogenizer (Mokon) and set the temperature at 80° C. 
       
     
       Lipid Phase Preparation 
       [0000]    
       
         Step 3. Stir to dissolve tretinoin in benzyl alcohol and most of propylene glycol (part A) in a II-L stainless steel container.
       Stirring speed 5, solution temperature 50° C.   
     
         Step 4, Transfer oil phase materials: Isopropyl Myristate, Cholesterol, Vitamin E Acetate, Polysorbate 80 and BHT to mix can. Mix to melt them (Anchor speed 75.2 rpm). When the oil phase materials are melted, add Phospholipon 80H to mix can and mix to melt it. 
         Step 5. Heat purified water (part A) to 60° C. 
         Step 6. Transfer tretinoin solution into mix can while anchor is on. Rinse the SS container with PG. Mix for 5 minutes at 75 rpm. 
         Step 7. Add water (part A) to mix can while anchor is on. Apply vacuum to mix can at 15 in-Hg. Mix for 45 minutes.
       Anchor speed 75.2 rpm, vacuum level 15 in. Hg. Product temperature at the beginning 61.2° C. Product temperature at the end 52.1° C.   
     
         Step 8. Turn on Mokon. Apply maximum vacuum to mix can. Cool the product to room temperature for 90 minutes with anchor. 
       
     
         [0000]    
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Product 
                 Vacuum level 
               
               
                 Mokon temperature (° C.) 
                 Temperature 
                 (in-Hg) 
               
               
                   
               
             
             
               
                 40 
                 50.1 
                 20 
               
               
                 30 
                 45.6 
                 22 
               
               
                 30 
                 40.7 
                 23 
               
               
                 20 
                 32.9 
                 24 
               
               
                 20 
                 27.9 
                 25 
               
               
                   
               
             
          
         
       
     
       Carbopol Dispersion Preparation 
       [0000]    
       
         Step 9. Set up Lightnin mixer. Add most of water (part B) and propylene glycol (part B) into a stainless steel container. Start mixing at 600 rpm 
         Step 10. Add clindamycin phosphate into the above container. Rinse the container with water. Dissolve clindamycin phosphate. 
         Step 11. Add Carbopol slowly into stainless steel container. Continue to stir until a uniform and lump-free dispersion is achieved. 
         Step 12. Stop the vacuum. Transfer Carbopol dispersion to mix can while anchor is on, rinse the container with rinse water. 
         Step 13. Mix for 10 minutes using anchor at 75 rpm. 
         Step 14. Add Triethanolamine 85% while the anchor is on. Rinse the container using the rinse water. 
         Step 15. Apply maximum vacuum. Mix with mixer/emulsifier at 3000 rpm and disperser at 
         2398 rpm for 10 minutes. Continue to mix with anchor for 20 minutes. 
         Step 16. Release the vacuum and stop the anchor. Scrape the product from the agitators. 
         Step 17. Apply maximum vacuum. Mix with mixer/emulsifier at 3000 rpm and disperser at 2398 rpm for 10 minutes. Continue to mix with anchor for 20 minutes. 
         Step 18. Scrape the product from the agitators. Measure the yield, pH and bulk density. Take samples in order to evaluate the final product visually and microscopically. 
       
     
       Results 
       [0049]    Slightly yellow gel. Smooth. Uniformly disperse. A lot of liposome structure. No crystal presented. Passed cycle study. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Example Formulation of Tretinoin/Clindamycin 
               
               
                 Phosphate Acne Treatment Composition 
               
             
          
           
               
                   
                 Ingredient 
                 % w/w 
               
               
                   
                   
               
             
          
           
               
                   
                 Benzyl Alcohol, NF 
                 2.0 
               
               
                   
                 Isopropyl Myristate, NF 
                 8.0 
               
               
                   
                 Cholesterol, USP 
                 0.3 
               
               
                   
                 Tretinoin 
                 0.06 
               
               
                   
                 Propylene Glycol USP (part A) 
                 10.0 
               
               
                   
                 Vitamin E Acetate, USP 
                 0.3 
               
               
                   
                 Polysorbate 80, NF 
                 0.75 
               
               
                   
                 Phospholipon 80H 
                 7.32 
               
               
                   
                 BHT 
                 0.1 
               
               
                   
                 Purified Water (part A) 
                 28.0 
               
               
                   
                 Carbopol 980NF 
                 0.4 
               
               
                   
                 Clindamycin Phosphate 
                 1.29 
               
               
                   
                 Triethanolamine 85% 
                 0.25 
               
               
                   
                 Propylene Glycol USP (part B) 
                 10.0 
               
               
                   
                 Purified Water (part B) 
                 31.23 
               
               
                   
                   
               
             
          
         
       
     
         [0050]    A process for treating acne is provided by the present invention. An inventive process includes the steps of providing a composition including a liposomal gel preparation of an antibiotic and a retinoid and applying the composition to an area of skin affected by acne in a subject having acne. 
         [0051]    While the foregoing describes liposomal compositions in which the lipid phase is discontinuous, and the aqueous phase is continuous, reverse structures are known in the art; and, they may also be employed in the present invention. In such structures, the retinoid will be in a continuous, lipid phase, and the antibiotic in a discontinuous aqueous phase. 
         [0052]    One skilled in the art will readily appreciate that the present invention is well-adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The present methods, procedures, treatments, molecules, and specific compounds described herein are presently representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention as defined by the scope of the claims.