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Two Current Drugs Shown Also to Promote Hair Growth

Test mice regrow hair

Mice receiving FDA-approved tofacitinib or ruxolitinib regrew nearly all their hair, center and right; drug was applied only to the right side of each mouse. Little to no hair growth occurred in control mice during the same time frame, left. (Columbia University Medical Center)

23 October 2015. Research originally designed to study hair loss from an autoimmune disorder, uncovered two drugs now on the market that in lab tests show they may also regrow hair. Findings of the study led by molecular dermatology professor Angela Christiano at Columbia University in New York appear in today’s issue of the journal Science Advances.

The paper reports that Columbia University filed patent applications for the discoveries developed from the research. In addition, Christiano is the founder of Vixen Pharmaceuticals Inc., a start-up company licensing and commercializing the technology.

Hair grows in humans on a cyclical basis, alternating between growth and suspended or resting phases. Hair loss and baldness of several kinds, including male pattern baldness, the most common form among men, can be traced to the inability of hair follicles that stay alive but fail to keep growing after entering the resting phase. Christiano and colleagues at Columbia first began studying a particular type of hair loss caused by alopecia areata, an autoimmune disorder where the immune system is tricked into attacking hair follicles.

Their research led to identification of small-molecule, or low molecular weight, drugs called Janus kinase or JAK inhibitors, designed to block signals from enzymes that also block signals causing the autoimmune attack, allowing some people with alopecia areata to regrow hair. JAK inhibitors are associated with a number of conditions, and already approved in the U.S. to treat rheumatoid arthritis — tofacitinib, marketed as Xeljanz by Pfizer — and ruxolitinib marketed as Jakafi by Incyte Corp. to treat some cases of a rare bone marrow disorder known as polycythemia vera.

Both tofacitinib and ruxolitinib are drugs taken orally. Christiano’s team discovered, almost by accident, that JAK inhibitors applied topically to the skin of lab mice regrew hair, even more hair than the drugs taken orally. This finding suggested to the team that JAK inhibitors could act directly on hair follicles, and not just block the autoimmune attack.

In tests with lab mice, the researchers found JAK inhibitors could activate hair follicles in their resting state and quickly begin growing hair. Mice were treated for 5 days with one of the FDA-approved JAK inhibitors, resulting in new hair beginning to grow after 7 to 10 days. Untreated mice, by comparison, grew no hair. Similar results were found with hair in human tissue grafted on mice.

“There are very few compounds that can push hair follicles into their growth cycle so quickly,” says Christiano in a university statement. The team attributes the new hair growth to JAK inhibitors stimulating dermal papilla stem cells, where blood vessels nourish hair follicles. The researchers note, however, that their tests were conducted only with normal mice and human-grafted hair follicles, not with other forms of hair loss caused by disease such as alopecia areata.

Christiano tells more about the study in the following video.

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