An experimental therapy has slowed the growth of the most common form of skin cancer: basal cell carcinoma.

The drug, named vismodegib but still often referred to by its earlier moniker GDC-0449, was tested in 41 patients with a rare condition called basal cell nevus syndrome. Some patients with the syndrome develop thousands of basal cell carcinomas, and must endure frequent operations to remove them.

Over the course of a year, some patients who received the placebo accumulated ten or more new lesions in the course of a single month. All of those who received the drug had fewer than ten new lesions a month. The results will be reported on 3 April at the American Association for Cancer Research annual meeting in Orlando, Florida. (A webcast of the talk will eventually be posted here).

Vismodegib was the first therapy developed to block the ‘Hedgehog’ cellular pathway to enter clinical trials. That pathway is a critical player in embryonic development, but improper activation of Hedgehog signaling in mature cells can drive cancer. With some estimating that the Hedgehog pathway is altered in as many as 25% of all cancers, pharma companies are racing to bring Hedgehog inhibitors to the market.

It was not always so, says dermatologist Ervin Epstein of the Children’s Hospital of Oakland Research Institute. Epstein, who led the clinical trial, was among the first researchers to find a link between the Hedgehog pathway and basal cell nevus syndrome. At that time, no self-respecting pharma company would bother to take up a Hedgehog project, Epstein says, given the rarity of the syndrome.

But around 2004, a series of publications linked the pathway to other cancers, including prostate cancer. “After that, no self-respecting pharma company could hold their head up without having a Hedgehog inhibitor in development,” says Epstein.

For now, vismodegib’s side effects, which include hair loss, muscle cramps, and weight loss, make it unlikely to be used at the tested dose in most basal cell carcinoma patients. With a cure rate of over 98%, surgery remains the best option for those patients, says Epstein. But for the unlucky few who have basal cell nevus syndrome, the results are “a breakthrough with a capital ‘B’,” says Daniel Von Hoff of the Translational Genomics Research Institute in Phoenix, Arizona, who was not involved in the trial.

Vismodegib was discovered by Genentech, headquartered in South San Francisco and now owned by the Swiss pharma giant Roche. The drug is also in clinical trials against pancreatic, stomach, lung, and prostate cancer.