A novel cancer drug being developed by AstraZeneca boosted the survival prospects of patients with an aggressive form of breast cancer during a late-stage clinical trial, paving the way for the pharmaceutical group to secure regulatory approval.
The drug was studied in a large Phase III trial of people with a type of breast cancer known as HER2-negative, whose tumours had already spread to other parts of the body and who had inherited a mutation in a gene known as BRCA.
Patients taking AstraZeneca's medicine, Lynparza, typically went for seven months before their cancer became worse, whereas the rate of "progression-free survival" for those on chemotherapy was just over four months.
The results of the trial were unveiled at the world's largest cancer meeting on Sunday and were included in a late-breaking session by the conference organisers because they were deemed to be scientifically important.
Lynparza is part of a new class of medicines known as parp inhibitors that work by trying to stop cancer cells from repairing themselves. They appear to help those patients who have inherited a BRCA mutation that significantly increases their chances of developing ovarian or breast cancer.
AstraZeneca's drug has been approved for some ovarian cancer patients, as have rival medicines from Clovis and Tesaro, but doctors have not yet been given a green light to use the therapies in breast cancer.
"The results in breast cancer have been spotty and not yet definitive but I think this will start to change that," said Dr Daniel Hayes, the president of the American Society of Clinical Oncology, which is hosting its annual meeting in Chicago this weekend.
Like most novel drugs, Lynparza is first being tested in the sickest patients — those who have so-called metastatic disease that has spread to other parts of the body and who often have grim survival prospects.
"This is the first time we have been able to show an improvement in outcomes for these patients with a parp inhibitor," said Dr Mark Robson, an oncologist at Memorial Sloan Kettering Cancer, who led the trial.
Breast cancer sufferers with metastatic disease account for about a quarter of patients, and only a minority of those have BRCA mutations.
But Pascal Soriot, AstraZeneca chief executive, said the trial results were a sign that the drug could help patients whose disease is not so advanced.
The company is presently running a large trial to determine whether the medicine can improve outcomes in so-called adjuvant therapy — which is given to earlier stage patients after they have undergone surgery — with results due in 2019.
"The data are important, they show there is a very significant clinical benefit, and they give us hope for the adjuvant study we have been running," Mr Soriot said.
Lynparza is one of several cancer drugs that AstraZeneca hopes to use to build a successful oncology franchise in the coming years, which could guarantee its future as an independent company.
Sales of the medicine have struggled in the US amid fierce competition in the ovarian cancer market, but a string of approvals in breast cancer would change that, Mr Soriot said.