Despite a hefty amount of research, science still hasn't cracked the mystery of how to stimulate hair regrowth. A new study, spearheaded by researchers at the University of Manchester, has uncovered an entirely new way to promote human hair growth – and it's inspired by a side effect of a nearly 50-year-old drug.

In the early 1970s, a drug called Cyclosporine A was isolated from a species of fungus. The research work was looking for a new anti-fungal antibiotic, but the compound wasn't especially clinically effective for that use. A few years later, it was discovered that Cyclosporine A had a remarkable immunosuppressive activity.

By the 1980s, it was approved for medical use and its clinical application proved a major breakthrough to the field of organ transplantation. The drug allowed for a new immunosuppressive agent to help patients maintain new organs that otherwise would have been rejected by their bodies.

Cyclosporine A is not a harmless drug, though, and can result in a number of severe side-effects. One of the more innocuous side effects that decades of use has revealed is that it often enhances hair growth. A study investigating the mechanism behind this specific side effect has now revealed a new potential treatment that could stimulate hair growth in humans.

After performing a complete gene expression analysis on human hair follicles treated with Cyclosporine A, researchers discovered the specific mechanism in the drug that seemed to be affecting hair growth. The study found Cyclosporine A reduced the expression of SFRP1, a protein that negatively regulates a key pathway crucial for the growth of hair follicles. So, suppressing this protein seemed to explain how Cyclosporine A enhanced hair growth.

The next step was to find a way to specifically antagonize SFRP1 and the research uncovered a compound called WAY-316606. Originally developed to treat osteoporosis, it was discovered that WAY-316606 targets similar mechanisms to Cyclosporine A but without the broader immunosuppressive actions of that drug. Ex vivo tests using human scalp samples revealed WAY-316606 enhanced hair growth, suggesting external application of it, or a similar compound, could be an effective hair loss treatment.

"The fact that this new agent, which had never even been considered in a hair loss context, promotes human hair growth is exciting because of its translational potential: it could one day make a real difference to people who suffer from hair loss," explains Nathan Hawkshaw, one of the researchers on the project.

It's still early stages in the research process and Hawkshaw is realistic about the long road ahead of any new treatment reaching the market.

"Clearly though, a clinical trial is required next to tell us whether this drug or similar compounds are both effective and safe in hair loss patients," Hawkshaw adds.

The new study was published in the journal PLOS Biology.