Prostaglandin analog compositions and methods to treat epithelial-related conditions

This application claims the benefit of U.S. Provisional Application No. 60/984,198, filed Oct. 31, 2007, the contents of which are incorporated by reference in their entirety.

The present invention relates to the formulation and delivery of prostaglandin analogs to treat epithelial-related conditions. In some embodiments, the compositions of the invention are used to stimulate hair growth. In some embodiments, the compositions of the invention are used to restore hair color to depigmented hair. The present invention further relates to the formulation and delivery of prostaglandin analogs to reduce intraocular pressure.

Hair, a filamentous outgrowth of protein found only on mammals, is integral to our body image and can have a profound influence on our self-esteem and self-confidence. The hair of non-human mammal species is commonly referred to as fur. In some species, hair is absent at certain stages of life.

Hair grows from hair follicles deep in the dermis and projects from the epidermis of the skin. Human skin has two types of hair: vellus hair and terminal hair. Much of human hair is short, underpigmented vellus hair rather than terminal hair. The most noticeable part of human hair is the hair on the head, which can grow longer than on most mammals and is more dense than most hair found elsewhere on the body. The term “scalp” refers to the integument of the upper part of the head, usually including the associated subcutaneous structures. The scalp is the anatomical area bordered by the face anteriorly and the neck to the sides and posteriorly.

Vellus hair is short, fine, “peach fuzz” body hair. It is a very soft, generally pale, and short hair that grows in most places on the human body in both sexes. It is usually less than two cm long and the follicles are not connected to sebaceous glands. It is most easily observed in women and children, as they have less terminal hair to obscure it. It is also found in pre-adolescents and in male pattern baldness.

Terminal hair is developed hair, which is generally longer, coarser, thicker and darker than the shorter and finer vellus hair. Phases of growth in terminal hair are more apparent than in vellus hair; it generally has a longer anagen phase. It has associated sebaceous glands, whereas a vellus hair may not. Under certain conditions, such as puberty, some vellus hair may become androgenic hair. Under other conditions, such as male pattern baldness, it may revert to a vellus-like state.

Each hair comprises two structures: the follicle in the skin and the shaft we see. The follicle contains several layers. At the base of the follicle is a projection called a papilla, which contains capillaries, or tiny blood vessels, that feed the cells. The living part of the hair, the area surrounding the papilla called the bulb, is the only part fed by the capillaries. The cells in the bulb divide every 23 to 72 hours, faster than any other cells in the body. The follicle is surrounded by two sheaths—an inner and outer sheath. These sheaths protect and mold the growing hair shaft. The inner sheath follows the hair shaft and ends below the opening of a sebaceous (oil) gland, which produces sebum, a natural conditioner and sometimes an apocrine (scent) gland. The outer sheath continues all the way up to the gland. An erector pili muscle attaches below the gland to a fibrous layer around the outer sheath. When this muscle contracts, it causes the hair to stand up.

The primary component of the hair fiber is keratin. Keratins are proteins, long chains (polymers) of amino acids. The hair shaft contains three layers of keratin. The inner layer, which is called the medulla, may not be present. The next layer is the cortex, which makes up the majority of the hair shaft. The outer layer is the cuticle, which is formed by tightly packed scales in an overlapping structure similar to roof shingles. Most hair conditioning products attempt to affect the cuticle. Pigment cells are distributed throughout the cortex and medulla giving the hair its characteristic color.

The term “eyebrow” refers to an area of coarse skin hairs above the eye that follows the shape of the brow ridges. The main function of the eyebrow is to prevent moisture, mostly salty sweat and rain, from flowing into the eye, an organ critical to sight. The typical curved shape of the eyebrow (with a slant on the side) and the direction in which eyebrow hairs are pointed, make sure that moisture has a tendency to flow sideways around the eyes, along the side of the head and along the nose. Eyebrows also prevent debris such as dandruff and other small objects from falling into the eyes, as well as providing a more sensitive sense for detecting objects being near the eye, like small insects. Eyebrows also have an important facilitative function in communication, strengthening facial expressions such as surprise, confusion, or anger.

The terms “eyelash” and “lash” are used interchangeably to refer to one of the hairs that grow at the edge of the eyelid. Eyelashes protect the eye from debris and provide a warning that an object (such as an insect or dust mite) is near the eye (which then is closed reflexively).

The inside of the nose contains small hairs called cilia. These cilia and nasal mucus clean the air drawn into the nose of the microscopic particles we inhale, including dust, pollen, and pollutants, for ultimate passage to the lungs.

Hair Biology

There are three stages of hair growth: catagen, telogen, and anagen.

Anagen is the active growth phase of the hair during which the cells in the root of the hair are dividing rapidly. Anagen hairs are anchored deeply into the subcutaneous fat and cannot be pulled out easily. When a new hair is formed, it pushes the club hair up the follicle and eventually out. During this phase the hair grows about 1 cm every 28 days. Scalp hair stays in this active phase of growth for 2-6 years. Human subjects that have difficulty growing their hair beyond a certain length have a short active phase of growth. Human subjects that have very long hair have a long active phase of growth. The hair on the arms, legs, eyelashes, and eyebrows have a very short active growth phase of about 30-45 days, which is why they are so much shorter than scalp hair.

The anagen phase is followed by a catagen phase. The catagen phase is a transitional stage that lasts for about 2-3 weeks. About 3% of all hairs are in this phase at any time. During this time growth stops and the outer root sheath shrinks and attaches to the root of the hair. This is the formation of what is known as a club hair.

After catagen, the hair goes into a telogen phase. Telogen is the resting phase, which accounts for 10-15% of all hairs. It lasts for about 100 days for hairs on the scalp and much longer for hairs on the eyebrow, eyelash, arm and leg. During this phase the hair follicle is completely at rest and the club hair is completely formed. As compared with anagen hair, telogen hair is located higher in the skin and can be pulled out relatively easily. Pulling out a hair in this phase will reveal a solid, hard, dry, white material at the root. Normally, about 25-100 telogen hairs are shed each day.

In the normal scalp, approximately 80 to 90 percent of follicles are growing (anagen), about 5 to 10 percent are resting (telogen), and 1 to 3 percent are undergoing involution (catagen). Each day up to 75 hairs in telogen are shed from the scalp and about the same number of follicles enter anagen.

The term “alopecia” is a medical term for the absence or loss of hair including eyelashes, eyebrows, and scalp hair, as a result of illness, functional disorder, or hereditary disposition. For example, the term “Alopecia adnata” refers to underdevelopment of the eyelashes. Alopecia frequently occurs in patients undergoing treatment for cancer or suffering from other diseases, such as AIDS, where cell-killing, or cytotoxic, drugs are used.