Drugs developed to fight cancer and rheumatoid arthritis might work as creams to stimulate hair growth —offering a potential baldness cure, researchers reported Friday.

While cancer treatments are usually associated with hair loss, some specialized drugs called JAK inhibitors can actually help hair grow.

Angela Christiano and colleagues at Columbia University have been testing them as treatments for a rare form of hair loss called alopecia areata. This condition is caused by the immune system's mistaken attack on hair follicles, and the drugs work by suppressing inappropriate immune responses — that's why they help rheumatoid arthritis and some forms of blood cancer that involve immune cells.

"The surprise was when we started using the drugs on alopecia areata patients, when we used them topically the hair grew back much faster and more robustly than it did orally," Christiano told NBC News

"That really got us thinking how that can be. It's a little counter-intuitive."

What they found was the drugs were affecting the hair follicles directly. JAK, the compound that the drugs suppress, puts hairs into a "resting" stage. "It's actually promoting the resting state of the hair follicle. The inhibitors … allow the hair to enter the hair cycle," Christiano said.

When they rubbed the compound onto the skin of bald mice for five days, new hair sprouted within 10 days, the team reported in the journal Science Advances.

"The hair that came in came in beautifully and in a few weeks and very thickly," Christiano said.

"There are very few compounds that can push hair follicles into their growth cycle so quickly," she added. "Some topical agents induce tufts of hair here and there after a few weeks, but very few have such a potent and rapid-acting effect."

There are several Food and Drug Administration-approved JAK inhibitors, including ruxolitinib, or Jakafi and tofacitinib, sold under the brand name Xeljanz.

Because they suppress the immune system, leaving patients vulnerable to infections, it would be dangerous to use them to correct something cosmetic like male pattern baldness.

But applying such drugs topically would be far safer, Christiano said.


"Male pattern hair loss follicles are stuck in the same state where these drugs seem to work," she said.

Delivering it on the skin also seems to get more of the drug into the hair follicles, she said.

The Columbia team won't be testing the drug to treat male pattern baldness, but a drug company might, Christiano said.

"One of the reasons it's so difficult to develop drugs for hair is we can't grow hair in the petri dish," she said.

"Also, there isn't a good rat or mouse model of male pattern baldness." Drugs on the market to grow hair were all discovered by accident — Propecia was found to grow hair as a side-effect of treating enlarged prostates, and Latisse, sold to grow eyelashes, was discovered as a side-effect of a glaucoma treatment.