Hundreds of thousands of people with alopecia areata can benefit from a drug that can cure baldness in months.
A study of the twice-daily pill found that four out of 10 patients with the condition were able to regrow almost full hair within half a year.
The chief scientist behind the drug is not expected to work for the millions of men who lose their hair as they age, however.
Alopecia is the general medical term for hair loss. Alopecia areata – one type of hair loss – is caused by the body attacking its own healthy hair follicles.
Made by the US drug company Concert Pharmaceuticals, the new therapy works by weakening the immune response, preventing it from spoiling.
There is currently no cure for alopecia areata – although other drug companies are also trying drugs to help reverse the hair loss. Steroids and other medications can help trigger hair growth, however.
About 100,000 people in the UK and 6.8 million in the US have the condition. It can rob people of their hair in a matter of weeks.
Due to the rapid rate of hair loss, the disease can cause low self-esteem, depression and anxiety.
Notable sufferers include actress Jada Pinkett Smith. Her husband Will Smith got into a controversy at this year’s Oscars in March after he slapped comedian Chris Rock on the cheek for joking about his wife’s baldness.
Researchers at Yale University, Connecticut, have found that the experimental drug CTP-543 from Concert Pharmaceuticals has helped patients with alopecia areata grow back almost full head of hair. Pictured: Patient in previous Phase 2 clinical trials at the beginning (left) and end (right) of the 24-week study
The newest three-trial phase looked at 706 adults with alopecia aged 18 to 65 in the United States, Canada and Europe over 24 weeks.
Patients on average had only 16 percent of their hair at the start of the trial, and no more than half of their hair.
They were spit into three groups who received a placebo, an 8mg twice daily pill or a 12mg twice daily dose.
Both the 8mg and 12mg groups saw statistically significantly more growth than the placebo group, researchers said.
A total of 41.5 percent given the strongest dose saw more than 80 percent of their hair grow back before the end of the study.
Among those in the 8mg group, 29.6 percent experienced the same level of regrowth.
Only 0.8 percent of the placebo group saw a resurgence to more than 80 percent of the scalp.
Side effects occurred in less than 5 percent of patients, with the most common reactions including headaches, acne, and infections.
The drug works by inhibiting a particular enzyme activated during an immune response, called JAK1 and JAK2.
These enzymes make up a group called janus kinases, and too many of them can lead to inflammatory immune reactions that cause alopecia.
But suppressing them can also lead to weaker immunity in general, resulting in more infections.
Concert Pharma is expected to seek approval from the U.S. Food and Drug Administration (FDA) for the drug next year after a second Phase 3 trial that will repeat the study of 517 participants.
Approval will depend on positive results of the second test and could last up to 10 months.
Dr James Casella, chief development officer at Concert Pharmaceuticals, said: “With these compelling Phase 3 data, we believe that CTP-543 has the potential to be the best in the class treatment for patients with alopecia areata, a disease which has long been ignored.
‘We are extremely grateful to the patients and teams of clinical research professionals who are participating in our trials.
“We are working to change the medical landscape and hope that CTP-543 will be one of the first medical options approved by the FDA for this serious disease.”
Alopecia areata currently does not have any cure and doctors cannot predict how much hair someone is likely to lose after small spots begin to fall out.
But there is a 60 to 80 percent chance that hair will grow back naturally in the small areas when it falls out.
Among the most famous people with the disease include actress Jada Pinkett Smith
Her husband Will Smith got into controversy at this year’s Oscars in March after he slapped comedian Chris Rock on the cheek for joking about his wife’s baldness.
If hair grows back, it can last for months or years and usually begins as sparse white hair in the bald spots that can eventually thicken and regain its color.
Growth is less likely if everyone’s hair falls out.
Current treatments include corticosteroid injections, which are potent anti-inflammatory drugs that can suppress the immune system.
These can work in up to 62 percent of patients but also increase the risk of skin atrophy – thinning of the skin – by encouraging interest in new medications.
Dr. Brett King, a dermatologist at Yale University School of Medicine who led the study, said: “Today marks an important milestone in advancing new treatments for alopecia areata, and I am so happy to see such positive results Phase 3 trial with CTP-543.
“There is a great need for treatments for this difficult disease, and the results of the THRIVE-AA1 trial suggest that CTP-543 may be able to provide important therapy for treating alopecia areata.”
