Nature heralds a new, genetic weapon in our arsenal against cancer, be it pancreatic, lung, skin or liver. This is a cancer treatment based on the cancer’s genetic makeup, not what body part has tumors:
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.
Researchers have been anticipating such marker-based approvals for roughly a decade, as the rise of molecular profiling — characterizing a tumour based on the genes and proteins that it expresses — has promised a shift in cancer treatment.
In 2015, researchers reported that about 71% of trial participants whose tumours had a defect in their ability to repair damaged DNA benefited from pembrolizumab treatment, regardless of where those tumours were located. The flaw disables a pathway that repairs mistakes made by the enzymes that copy DNA during cell division. Those mistakes create mutated proteins that can signal to the immune system that something is amiss, says James Eshleman, a pathologist at Johns Hopkins University School of Medicine in Baltimore, Maryland.
Still, the landmark approval opens doors to other companies betting on this approach. Investigators at Loxo Oncology in Stamford, Connecticut, are betting that their drug larotrectinib will also be able to override location-specific cues. Larotrectinib targets TRK-fusion proteins, which are created when two genes fuse together. The resulting proteins spur tumour growth, and Loxo has been testing its drug in any tumour with the fusions. The company will report data from its trials on 3 June at the annual meeting of the American Society of Clinical Oncology in Chicago, Illinois.