Early success of Enhertu bodes well for class of medicines that could replace chemotherapy
New data on a breast cancer treatment from AstraZeneca and the Japanese drug maker Daiichi Sankyo brought a standing ovation from cancer doctors attending their annual meeting in Chicago on Sunday. And with good reason.
Enhertu is what’s known as an antibody-drug conjugate, because it uses an antibody to home in on a tumour cell before releasing a payload of toxic chemotherapy to kill it. This drug’s antibody zeroes in on a protein called HER2, a growth signal that in some breast cancers becomes too amped up. The US Food and Drug Administration approved Enhertu in late 2019 for some so-called “HER2 positive” cancers, or tumours that on a diagnostic test show a certain threshold of that signal.
Other HER2-targeted drugs have been studied in patients whose tumours express low levels of the protein, but none have helped. Oncologists have a few theories about what makes Enhertu different. The design of the drug itself could also matter. Daiichi Sankyo, which discovered the drug before striking a deal to develop it with AstraZeneca in 2019, seems to have ironed out many of the kinks that limited the success of earlier antibody-drug conjugates. Enhertu uses a different, more powerful chemo payload and a bigger one, too. Whereas most antibody-drug conjugates carry two to four chemo molecules, Enhertu delivers eight.