Drug improves survival in triple-negative breast cancer

A targeted therapy has improved survival compared with chemotherapy in patients with triple-negative breast cancer who cannot receive immunotherapy.

The drug, an antibody-drug conjugate (a treatment that delivers chemotherapy directly to cancer cells), slowed tumour progression and extended survival compared with standard chemotherapy in triple-negative breast cancer – an aggressive form lacking three common receptors found in other breast cancers.

AstraZeneca and Daiichi Sankyo’s Datroway succeeded in a Phase 3 trial involving patients whose tumours were either metastatic (spread to other parts of the body) or locally recurrent and inoperable. These patients were ineligible for a commonly used immunotherapy.

The companies said Datroway treatment led to a “statistically significant and clinically meaningful” improvement in both progression-free survival and overall survival, adding that the benefit in slowing tumour progression was “highly significant.”

They said it was the first time a survival benefit had been seen compared with chemotherapy in people unable to receive immunotherapy.

Ken Takeshita, Daiichi’s global head of research and development, said these “landmark” results have encouraged the companies to continue advancing Datroway programmes for triple-negative breast cancer and other tumour types.

They said full study details will be presented at an upcoming medical meeting and submitted to global regulators “as soon as possible.”

Datroway is one of several antibody-drug conjugates (ADCs) being developed by AstraZeneca and Daiichi Sankyo in the hope of replacing chemotherapy in many tumour types.

The drug targets a protein called TROP2, which is overexpressed in multiple cancers.

The companies have high expectations for Datroway following the clinical and commercial success of Enhertu, another ADC they co-developed that has helped transform treatment for certain breast cancers.

However, Datroway’s benefits have so far been less clear, leading to a narrower approval in lung cancer and lower commercial expectations in some advanced breast tumours.

In triple-negative tumours, Datroway could face competition from Gilead’s Trodelvy, another antibody-drug conjugate that targets TROP2.

Earlier this year, Gilead said Trodelvy kept tumours in check longer than chemotherapy in a trial also involving people ineligible for immunotherapy, although that study had not yet shown a survival benefit.

According to AstraZeneca, about 70 per cent of people with triple-negative breast cancer cannot receive immunotherapy, leaving chemotherapy as the first-line standard of care.

“We expect today’s results will mark an inflection point in the treatment of these patients who have the poorest prognosis of any type of breast cancer and urgently need better options,” said Susan Galbraith, who leads AstraZeneca’s cancer and blood disease R&D.

AstraZeneca shares rose by over 1 per cent in Monday morning trading, while Daiichi’s climbed by about 4 per cent.