FDA-Approved Drugs Boost Hair Regrowth In Mice

Although the idea of going bald typically conjures images of aging men, hair loss affects people of all genders and ages: Hair can fall out prematurely because of genetic predisposition, drug side effects, or autoimmune disorders. A recent test of two FDA-approved drugs—ruxolitinib and tofacitinib—now suggests that a general treatment for hair loss might be on the way (Sci. Adv. 2015, DOI: 10.1126/sciadv.1500973).

A team of researchers at Columbia University had observed that these drugs—approved for the treatment of myelofibrosis and rheumatoid arthritis, respectively—promoted hair growth when fed to mice but also impaired the animals’ immune systems. So the scientists thought the compounds might work ­better when rubbed onto skin.

The team shaved mice when their fur was in telogen, the resting stage of a hair follicle’s growth cycle. In this stage, hair usually takes more than a month to begin growing back. But treated areas of a mouse’s skin fully grew back in less than three weeks. Team leader Angela M. Christiano says the drugs are “basically accelerating what would normally happen several weeks later. They’re inducing new hair to begin to grow.”

The Columbia team got similar results on human skin grafted onto mice. However, in this experiment, tofacitinib was more effective.

The mechanism by which these drugs spur hair growth—at least in mice—appears to be very different from standard topical hair loss treatments such as Rogaine. A therapy for male-pattern baldness, Rogaine uses minoxidil, a vasodilator, to stimulate blood flow to hair follicles and thereby prevent hair from falling out. The new topical treatments inhibit JAK-STAT signaling, a pathway involving Janus kinases that triggers cells to begin transcribing DNA. Researchers believe this signaling pathway is most active when hair follicles, a type of stem cell, are at rest. When drugs block the pathway, the follicles “wake up” and enter a new growth phase.

“The big news of this new paper is that JAK inhibitors are even more versatile in function than previously thought,” says Amy McMichael, professor of dermatology at Wake Forest Baptist Medical Center, who was not involved in the study.

Christiano’s team hopes the drugs may curb hair loss from a variety of causes, such as the autoimmune disease alopecia areata and chemotherapy. “For any clinical setting where the hairs are stuck in resting phase,” Christiano says, “this would be a way to think about coaxing them back into the hair cycle.”