A translational biologist and laboratory researcher, Ashworth's research focuses on understanding breast cancer genetics to improve the treatment and care of patients. He was a key part of the team that identified the BRCA2 breast cancer susceptibility gene that is linked to an increased risk for some types of cancer. Ten years later, he discovered how to kill BRCA1- and 2-related tumor cells by treating them with PARP inhibitors which are drugs that increase the damage caused by the broken DNA repair machinery in those cells. This exemplifies the principle of synthetic lethality as cancer therapy. Three different PARP inhibitors are now approved by the FDA.