The present invention provides a method for treating or preventing excessive scarring, including keloid and hypertrophic scars, by administering 4-hydroxy tamoxifen to a patient with excessive scarring or a wound at risk for developing excessive scarring.

Description of the Invention

BACKGROUND OF THE INVENTION

The present invention relates to the treatment and prevention of excessive scarring, including keloid and hypertrophic scars, with 4-hydroxy tamoxifen (4-OHT).

Keloid scars, or keloids, are overgrowths of dense fibrous tissue that result from variations in normal wound healing. The dense fibrous tissue of a keloid extends beyond the borders of the original wound, and usually does not regress spontaneously. Thus, keloid scarring is out of proportion to the severity of the inciting wound.

Likewise, hypertrophic scars also are overgrowths of dense fibrous tissue that result from abnormal wound healing. However, hypertrophic scars do not extend beyond the original boundaries of a wound. Also unlike keloids, hypertrophic scars reach a certain size, then stabilize or regress.

The normal wound healing process extends over a one to two year period, and conceptually consists of three distinct stages. The first stage, the inflammatory stage, is intensely degradative. It begins immediately after injury and provides a means to remove damaged tissues and foreign matter from the wound. A few days after injury, the second stage, the proliferation and matrix synthesis stage, begins. During this stage, fibroblasts from surrounding tissues move into the wound and proliferate. The fibroblasts actively produce collagen, which they secrete into the extracellular matrix. Newly synthesized collagen forms cross-linked fibrils, which provide structural integrity to the wound. After several weeks, the final stage, the remodeling stage, begins. During the remodeling stage, the collagen fibrils, which previously were randomly oriented, align in the direction of mechanical tension, providing further mechanical strength to the wound. Upon completion of the entire process, the skin regains its chemical and physical barrier functions.

Six to eight weeks into the normal wound healing process, anabolic and catabolic processes reach an equilibrium. At this time, scar strength is approximately 30-40% that of healthy skin, and scars typically are hyperemic and thickened. Over the next several months, catabolic and anabolic processes abate, and progressive cross-linking of collagen fibers improves the wound's tensile strength. Also, hyperemia and thickness subside until a flat, white, pliable mature scar develops.

Excessive scarring results from an imbalance in the anabolic and catabolic wound healing processes. In the formation of an excessive scar, more collagen is produced than is degraded. As a result, the scar grows larger than is required for wound healing, with an over-production of cells, collagen and proteoglycan. Keloids grow in all directions, become elevated above the skin, and remain hyperemic. The exact mechanisms of excessive scarring are poorly understood, but it is believed that common mechanisms underlie the formation of both keloids and hypertrophic scars. Evidence suggests that increased transforming growth factor .beta.1 (TGF-.beta.1) expression plays a role in excessive scarring. TGF-.beta.1 promotes extracellular matrix production, and is produced at elevated levels by keloid fibroblasts.

Keloids and hypertrophic scars primarily present a cosmetic concern but can cause contractures, which may result in a loss of function if overlying a joint. Additionally, excessive scars can be painful, pruritic and cause a burning sensation. Once keloid lesions occur, they tend to continue growing for weeks to months, even for years. Growth usually progresses slowly, but keloids occasionally enlarge rapidly, even tripling in size within months. Hypertrophic scars tend to stabilize, and regress over time. However, this regression can be quite slow, and often incomplete.

Management of keloids and hypertrophic scars remains a major unsolved clinical problem. Though many forms of treatment have been used, none has proven to be consistently reliable. Current forms of treatment include use of occlusive dressings, compression therapy, intralesional corticosteroid injections, radiation therapy, and surgery.

Occlusive dressings and pressure devices are unpredictable forms of treatment, as a large percentage of patients treated by these means show little or no improvement. Additionally, compliance with these forms of treatment can be impractical. For example, dressings and pressure devices may need to be worn 24 hours per day for up to 12 months. For a scar on a visible or sensitive location, this simply may not be possible.

Intralesional corticosteroids have been the mainstay of keloid treatment. Corticosteroids reduce excessive scarring by reducing collagen synthesis, altering glucosaminoglycan synthesis, and reducing production of inflammatory mediators and fibroblast proliferation during wound healing. However, roughly half of all keloids fail to respond to corticosteroids, and roughly half of the scars that are completely resolved by corticosteroid treatment recur. Additionally, corticosteroid injections can cause several complications, including atrophy, telangiectasia formation, and skin depigmentation.

Radiation therapy may be the only predictably effective treatment for keloids that is presently available. It has the potential to cause cancer, however, and for this reason it is not generally recommended or accepted as a keloid treatment. Moreover, roughly 20 percent of keloids treated by radiation therapy alone recur within one year.

Surgical procedures, including excision, cryosurgery and laser therapy, can effectively remove keloid tissue, and currently are the treatment of choice for hypertrophic scars. However, these techniques often cause tissue trauma that results in further hypertrophic or keloid scars. Indeed, keloids recur in well more than half of patients treated by surgical excision, cryosurgery, and laser therapy. Additionally, these procedures cause pain and present a risk of infection. Cryosurgery also causes skin depigmentation in some patients.

As an alternative keloid treatment, some researchers have proposed using the breast cancer drug tamoxifen (Hu, 1998; Hu 2002). In vitro, tamoxifen inhibits keloid fibroblast proliferation and decreases collagen production. Apparently, tamoxifen effects this inhibition by downregulating TGF-.beta.1 expression, which promotes collagen formation (Chau 1998; Mikulec, 2001).

In vivo use of tamoxifen for treating scars would have drawbacks, however. Tamoxifen is currently available only for oral administration, and its administration by this route poses serious health risks and causes significant unwanted side effects. Tamoxifen potentially impacts on every estrogen receptor in the body, and, as both an agonist and antagonist, provokes a wide range of systemic effects. These effects include the increased risk of endometrial cancer, endometrial hyperplasia and polyps, deep vein thrombosis and pulmonary embolism, changes in liver enzyme levels, and ocular disturbances, including cataracts. Additionally, patients treated with oral tamoxifen reported having hot flashes, vaginal discharge, depression, amenorrhea, and nausea (Fentiman 1986; Fentiman 1988; Fentiman 1989; Ibis 2002). Locally administered tamoxifen, which might pose fewer risks, would eliminate first-pass liver metabolism, which changes tamoxifen into its active metabolites. Without liver metabolism, tamoxifen would be less effective.

Thus, despite the broad array of treatments available, there is no widely accepted and predictably effective means for preventing or treating excessive scars. Therefore, an effective approach to reducing keloid and hypertrophic scars would offer significant benefit if it also provoked few systemic side effects.

SUMMARY OF THE INVENTION

This invention relates to a method for minimizing or preventing excessive scarring, including keloid scars and hypertrophic scars. The method comprises administering an effective amount of 4-hydroxy tamoxifen for a period of time sufficient to minimize the scar or prevent its formation. This treatment approach offers several advantages over other treatments for scars, including (1) few systemic side effects, (2) a better safety profile, (3) easy patient compliance. Additionally, 4-hydroxy tamoxifen can be administered to a wound prophylactically to prevent or minimize excessive scar formation.

In performing the inventive method, 4-hydroxy tamoxifen may be administered by any means that delivers it to a wound or scar tissue in vivo. Preferably, the administration is performed by means that deliver 4-hydroxy tamoxifen locally, limiting systemic exposure to the drug. Examples of such modes include (1) topical administration at the site of a wound or scar, (2) direct injection into a wound or scar site, and (3) implantation of a controlled release polymer or other delivery device that incorporates 4-hydroxy tamoxifen. The inventive method may be performed as the sole form of therapy or prophylaxis, or may be combined with other forms.

A broad range of topical formulations are suitable for performing the invention, but hydroalcoholic solutions and hydroalcoholic gels are preferred. The concentration of 4-hydroxy tamoxifen in these formulations may vary, but a dose should result in local 4-hydroxy tamoxifen concentrations that effectively inhibit fibroblast proliferation and collagen production.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present inventors have discovered that, by administering 4-hydroxy tamoxifen in a pharmaceutically effective amount, one can treat or prevent excessive scars with fewer unwanted side effects. Thus, the approach of the invention provides a superior safety profile and easier patient compliance, compared to other treatment and prophylactic methods.

According to the present invention, the term "excessive scar" or "excessive scarring" refers to overgrowths of dense fibrous tissue that result from abnormal wound healing. Excessive scars have grown larger than necessary for normal wound healing, and are characterized by overproduction of cells, collagen and/or proteoglycan.

"Keloid scars" are excessive scars in which the dense fibrous tissue extends beyond the borders of the original wound or incision, and does not usually regress spontaneously. Determining whether a scar is a keloid can be difficult, since keloids often superficially resemble other hypertrophic scars. However, keloids have distinguishing histological features. One such feature is the collagen nodule, which contains a high density of fibroblasts and unidirectional collagen fibrils in a highly organized and distinct orientation. Additionally, keloids have a rich vasculature, a high mesenchymal cell density, and a thickened epidermal cell layer.

Skin color and genetics, which correlate with keloid formation, also can aid a determination of whether a scar is a keloid. As many as 16% of black Africans have keloids, while Polynesians, Chinese, Indians and Malaysians have fewer. Whites and albinos have the fewest. Patients with keloid scars tend to have an associated strong family history; both autosomal dominant and autosomal recessive modes of transmission have been reported.

The factors that correlate with keloid formation are helpful as well for determining whether a patient will benefit from prophylactic administration of 4-hydroxy tamoxifen. According to one aspect of the invention, 4-hydroxy tamoxifen is administered to a patient having a wound, when the patient presents an elevated risk for keloid formation. Factors especially useful for determining an elevated risk are an individual and family history of keloids.

"Hypertrophic scars" are excessive scars in which the dense fibrous tissue does not extend beyond the borders of the original wound or incision. They tend to be wider than necessary for normal wound healing to occur. Histologically, hypertrophic scars have more organized collagen fibers than keloids, and scant mucoid matrix. Hypertrophic lesions are characterized by randomly distributed tissue bundles consisting of uniaxially oriented extracellular matrix and cells.

The compound 4-hydroxy tamoxifen, or 1-[4-(2-N-dimethylaminoethoxy)phenyl]-1-(4-hydroxyphenyl)-2-phenylbut-1-e- ne, constitutes an active metabolite of the well characterized anti-estrogen compound, tamoxifen. Both E and Z isomers exist, either of which, alone or in combination, are useful according to the present invention. The Z isomer is preferred.

It is well known that 4-hydroxy tamoxifen acts as a selective estrogen receptor modulator (SERM) that exhibits tissue-specificity for estrogen receptive tissues. Studies have shown that 4-hydroxy tamoxifen can regulate the transcriptional activity of estrogen-related receptors, which may contribute to its tissue-specific activity. In vitro, 4-hydroxy tamoxifen exhibits more potency than tamoxifen, as measured by binding affinity to estrogen receptors, or ERs, and a binding affinity similar to estradiol for estrogen receptors (Robertson et al., 1982; Kuiper et al., 1997). Z-4-hydroxy tamoxifen inhibits the growth in culture of normal human epithelial breast cells 100 fold more than Z-tamoxifen (Malet et al., 1988).

Although 4-hydroxy tamoxifen is a tamoxifen metabolite, its usefulness for treating and preventing excessive scars is not presaged by previous experience with tamoxifen itself. Tamoxifen is extensively metabolized in humans, as shown in FIG. 1 (see Original Patent). Thus, its action in vivo is the net result of individual actions by the parent compound and its metabolite compounds competing for the occupation of receptors within target tissues. For example, see Jordan, 1982. Each of these compounds manifests different and unpredictable biological activities in different cells, determined in part by each compound's individual effect on receptor conformation. That is, receptor binding of each compound generates a unique receptor-ligand conformation that recruits different cofactors, and results in varying pharmacologies for the different compounds (Wijayaratne et al., 1999; Giambiagi et al., 1988).

Several examples of these varying effects have been documented. For instance, tamoxifen but not 4-hydroxy tamoxifen is a potent rat liver carcinogen. (Carthew et al., 2001; Sauvez et al., 1999). Additionally, tamoxifen but not 4-hydroxy tamoxifen initiates apoptosis in p53(-) normal human mammary epithelial cells (Dietze et al., 2001). By contrast, 4-hydroxy tamoxifen exhibits a significant inhibitory effect on estrone sulphatase activity in mammary cancer cell lines, while tamoxifen has little or no effect in this regard (Chetrite et al., 1993).

Methods for preparing 4-hydroxy tamoxifen are well known. For example, U.S. Pat. No. 4,919,937 to Mauvais-Jarvis et al. describes a synthesis derived from Robertson and Katzenellenbogen, 1982. That synthesis occurs in several stages: Stage 1--Reaction between 4-(.beta.-dimethylaminoethoxy)-.alpha.-ethyldeoxybenzoin and p-(2-tetrahydropyranyloxy)phenylmagnesium bromide; Stage 2--Separately from stage 1, formation of 1-(4-hydroxyphenyl)-2-phenyl-1-butanone by hydroxylation of 1,2-diphenyl-1-butanone; Stage 3--Reaction between the products of stages 1 and 2 to form 1-(4-dimethylaminoethoxyphenyl)-1-[p-2-tetrahydropyranyloxy)phenyl]-2-phe- nylbutan-1-ol; Stage 4--Dehydration with methanol/hydrochloric acid produces 1-[p-(.beta.-dimethylaminoethoxy)phenyl]-Z-1-(p-hydroxyphenyl)-2- -pheny-1-but-1-ene=4-OH-tamoxifen, a mixture of E and Z isomers; Stage 5--Separation of the E and Z isomers by chromatography and crystallization to constant specific activity.

According to the present invention, 4-hydroxy tamoxifen may be administered in any dosage form and via any system that delivers the active compound to a wound or scar in vivo. Preferably, the administration is performed by a means that delivers 4-hydroxy tamoxifen locally, limiting systemic exposure to the drug. For example, 4-hydroxy tamoxifen, alone or in combination with a pharmaceutically acceptable vehicle, can be topically applied to the surface of a wound or scar site, can be injected into a wound or scar site, or can be incorporated in to a controlled release polymer and surgically implanted in a region to be treated. The optimal method of administering an acceptable dose to minimize scarring will depend upon the location of the scar and the extent of scarring.

Preferably, the 4-hydroxy tamoxifen is delivered topically, such as by "cutaneous administration," a phrase that denotes any mode of delivering a drug from the surface of a patient's skin, through the stratum corneum, epidermis, and dermis layers, and into the microcirculation. This is typically accomplished by diffusion down a concentration gradient. The diffusion may occur via intracellular penetration (through the cells), intercellular penetration (between the cells), transappendageal penetration, (through the hair follicles, sweat, and sebaceous glands), or any combination of these. Topical administration offers the distinct advantage of being non-invasive.

A proper dose for administration should result in local 4-hydroxy tamoxifen concentrations that effectively inhibit fibroblast proliferation and collagen production, without causing significant side effects. Although the invention is not constrained to any particular theory, clinically significant side effects of anti-estrogen agents occur when the agents displace estradiol in non-target tissues. Because 4-hydroxy tamoxifen and estradiol have similar binding affinities for estrogen receptors, a competition between them for receptor binding would be approximately equal when the concentration of each compound approximates that of the other. If the 4-hydroxy tamoxifen concentration exceeds the estradiol concentration, then the former will be bound preferentially to the estrogen receptors, and vice versa.

Accordingly, doses of 4-hydroxy tamoxifen that result in plasma concentrations less than the estradiol concentration are preferred. The daily doses to be administered can initially be estimated based upon the absorption coefficients of 4-hydroxy tamoxifen, the tissue concentration that is desired, and the plasma concentration that should not be exceeded. By administering 4-hydroxy tamoxifen locally, high concentrations can be achieved in the target tissues without simultaneously raising 4-hydroxy tamoxifen plasma levels to a point where significant systemic competition for estradiol receptors occurs. Of course, the initial dose may be optimized in each patient, depending on individual responses.

In a topical formulation, doses on the order of 0.25 to 3 ug of 4-hydroxy tamoxifen/cm.sup.2/day should achieve the desired result, with doses of about 0.5 to 2.5 ug/cm.sup.2/day being preferred. Doses of about 1.0 and 2.0 ug/cm.sup.2/day are more highly preferred.

Cutaneous administration can be accomplished mainly in two different ways: (i) by mixing a therapeutically active compound or its non-toxic pharmaceutically acceptable salt with suitable pharmaceutical carriers and, optionally, penetration enhancers to form ointments, emulsions, lotions, solutions, creams, gels or the like, where an amount of said preparation is applied onto a wound or scar site, or (ii) by incorporating the therapeutically active substance into patches or transdermal delivery systems according to known technology.

The effectiveness of cutaneous drug administration depends on many factors, including drug concentration, surface area of application, time and duration of application, skin hydration, physicochemical properties of the drug, and partitioning of the drug between the formulation and the skin. Drug formulations intended for cutaneous use take advantage of these factors to achieve optimal delivery. Such formulations often contain penetration enhancers that improve cutaneous absorption by reducing the resistance of the stratum corneum by reversibly altering its physiochemical properties, changing hydration in the stratum corneum, acting as co-solvent, or changing the organization of lipids and proteins in the intercellular spaces. Such enhancers of cutaneous absorption include surfactants, DMSO, alcohol, acetone, propyleneglycol, polyethylene glycol, fatty acids, fatty alcohols and related molecules, pyrrolidones, urea, and essential oils. In addition to chemical enhancers, physical methods can increase cutaneous absorption. For example, occlusive bandages induce hydration of the skin. Other physical methods include iontophoresis and sonophoresis, which use electrical fields and high-frequency ultrasound, respectively, to enhance absorption of drugs that are poorly absorbed due to their size and ionic characteristics.

The many factors and methods relating to cutaneous drug delivery are reviewed in REMINGTON: THE SCIENCE AND PRACTICE OF PHARMACY, Alfonso R. Gennaro (Lippincott Williams & Wilkins, 2000), at pages 836-58, and in PERCUTANEOUS ABSORPTION: DRUGS COSMETICS MECHANISMS METHODOLOGY, Bronaugh and Maibach (Marcel Dekker, 1999). As these publications evidence, those in the pharmaceutical field can manipulate the various factors and methods to achieve efficacious cutaneous delivery.

4-Hydroxy tamoxifen is a large and very lipophilic molecule; hence, without assistance from penetration enhancers it poorly penetrates the skin. Accordingly, formulations of 4-hydroxy tamoxifen used in the present invention preferably contain one or more penetration enhancers. Alcohols are preferred enhancers because 4-hydroxy tamoxifen is soluble in alcohol. Isopropyl myristate also is a preferred enhancer.

For cutaneous administration, 4-hydroxy tamoxifen may be delivered in an ointment, cream, gel, emulsion (lotion), powder, oil or similar formulation. To this end, the formulation may comprise customary excipient additives, including vegetable oils such as almond oil, olive oil, peach kernel oil, groundnut oil, castor oil and the like, animal oils, DMSO, fat and fat-like substances, lanolin lipoids, phosphatides, hydrocarbons such as paraffins, petroleum jelly, waxes, detergent emulsifying agents, lecithin, alcohols, carotin, glycerol, glycerol ethers, glycols, glycol ethers, polyethylene glycol, polypropylene glycol, non-volatile fatty alcohols, acids, esters, volatile alcoholic compounds, urea, talc, cellulose derivatives, and preservatives.

For practicing the present invention, preferred formulations contain 4-hydroxy tamoxifen in a hydroalcoholic gel. The amount of 4-hydroxy tamoxifen per 100 grams of gel may range from about 0.001 gram to about 1.0 gram. Preferably, it ranges from about 0.01 gram to about 0.1 gram. Table 1 (see Original Patent) describes the composition of two highly preferred 4-hydroxy tamoxifen gel formulations.

According to the present invention, 4-hydroxy tamoxifen also may be delivered via a transdermal patch. In one embodiment, the patch comprises a reservoir for the 4-hydroxy tamoxifen formula. The patch may comprise (a) a solution-impermeable backing foil, (b) a layer-like element having a cavity, (c) a microporous or semi-permeable membrane, (d) a self-adhesive layer, and (e) optionally, a removable backing film. The layer-like element having a cavity may be formed by the backing foil and the membrane. Alternatively, the patch may comprise (a) a solution-impermeable backing foil, (b) an open-pored foam, a closed-pore foam, a tissue-like layer or a fibrous web-like layer as reservoir, (c) if the layer according to (b) is not self-adhesive, a self-adhesive layer, and (d) optionally a removable backing film.

It is contemplated that the administration of 4-hydroxy tamoxifen may be combined with other keloid therapies. According to the present invention, therefore, administration of 4-hydroxy tamoxifen may be accompanied by the use of occlusive dressings, compression therapy, intralesional corticosteroid injections, radiation therapy, and surgery, including cryotherapy and laser therapy.

Claim 1 of 19 Claims

1. A method of treating or reducing the risk of excessive scars, comprising locally cutaneously administering 4-hydroxy tamoxifen to a site of excessive scarring or a wound or incision at risk for developing excessive scarring.
 

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