AstraZeneca and Daiichi Sankyo are challenging Gilead Sciences for dominance in one of the toughest-to-treat breast cancers, with new data from Europe’s biggest oncology meeting signaling a high-stakes race for patients — and profits.
Late-stage results presented Sunday showed that both drugs — Astra and Daiichi’s Datroway and Gilead’s Trodelvy — improved outcomes in patients receiving first-line treatment for metastatic triple-negative breast cancer ineligible for immunotherapy.
Datroway extended overall survival by about five months compared with chemotherapy, reducing the risk of disease progression or death by 43%. Trodelvy cut that risk by 38%, though data on overall survival isn’t yet complete.
Both sets of findings could change clinical practice, said Ana C. Garrido-Castro, an oncologist at Dana-Farber Cancer Institute, who wasn’t involved in the trials. “About 25 to 30% of patients do not survive past six months with chemotherapy alone,” she said.
Both drugs belong to a newer class known as antibody-drug conjugates — therapies that combine an antibody designed to home in on cancer cells with a potent chemotherapy compound meant to kill them once attached.
Triple-negative breast cancer accounts for about 10% to 15% of all cases and has a five-year survival rate of roughly 77% — below the 91% average for breast cancer. Because it lacks the hormone and HER2 receptors that other therapies target, patients have few options once the disease spreads. Even modest survival gains are therefore seen as meaningful.
Doctors at the European Society for Medical Oncology meeting in Berlin cautioned that the crossover design in Gilead’s trial — allowing patients in the control arm to switch to Trodelvy once their cancer worsened — makes a direct comparison difficult. Gilead said the design was chosen to prioritize patient welfare.
“It’s always more difficult to show an overall survival benefit when you allowed for crossover,” Gilead’s Chief Medical Officer Dietmar Berger said in an interview. “We allow for crossover in the study because we felt it was the right decision for patients.”
Analysts estimate the potential market for the new treatment exceeds $1 billion, a prospect AstraZeneca sees as a major commercial opportunity.
“It’s a blockbuster — if not a blockbuster-plus opportunity for Datroway,” said Dave Fredrickson, executive vice president of Astra’s oncology business, in an interview.
If both medicines win approval for these patients, doctors say the choice of therapy will likely hinge on individual circumstances and side-effect profiles.
Patients concerned about diarrhea, a known side effect of Gilead’s Trodelvy, may be steered toward other options, while those with existing eye conditions might avoid Astra and Daiichi’s Datroway, which can affect vision, said Paul-Henri Cottu, an oncologist at Paris’s Institut Curie.
Bloomberg’s Robert Langreth contributed.