Heidi Ledford in The New York Times:
The US Food and Drug Administration (FDA) has issued its first approval of a cancer drug that targets tumours with specific mutations, regardless of where in the body the tumour first took root. This deviates from the agency’s previous approach: although a drug’s use may have been linked to the presence of a particular molecular marker, the FDA still required individual approvals to deploy that drug based on the tumour's location. The announcement on 23 May expands the use of pembrolizumab, manufactured by pharmaceutical giant Merck & Co. of Kenilworth, New Jersey. The drug boosts the body’s ability to attack tumours by blocking a protein called PD-1, which normally holds the immune system in check. The FDA had previously approved pembrolizumab for use in several cancers, including lung and skin cancer. But physicians can now use it in any solid tumour that has a particular defect in its ability to repair damaged DNA.
Yet achieving this milestone has been more difficult than many cancer researchers initially expected. Despite early enthusiasm for the approach, researchers have come to respect the influence of a tumour’s location on its response to treatment, says cancer researcher René Bernards of the Netherlands Cancer Institute in Amsterdam. “It was a case of irrational exuberance,” he says. “When push comes to shove, the clinical responses were not that impressive.” Bernards speaks from experience. In 2010, researchers reported a successful trial of a drug called vemurafenib, which targets a mutated form of the protein B-RAF1. Subsequent studies found that the drug worked in 48% of melanomas with that mutation2. The results came as cancer genome sequencing efforts were gathering steam, building massive catalogues of mutations found across different cancers. The vemurafenib success fuelled hopes that the drug would work in other cancers with the same B-RAF mutation.