AstraZeneca and Daiichi's Datroway Shows Promise in Hard-to-Treat Breast Cancer

AstraZeneca and Daiichi Sankyo's antibody-drug conjugate, Datroway, has demonstrated significant efficacy in a large clinical trial focused on aggressive, hard-to-treat breast cancer. The drug extended overall survival and progression-free survival in patients with inoperable metastatic triple-negative breast cancer for whom immunotherapy is not an option.

Trial Results and Clinical Significance

The Phase 3 TROPION-Breast02 study, involving nearly 650 participants, showed that Datroway extended median overall survival to 23.7 months compared to 18.7 months for patients receiving chemotherapy. Additionally, the drug almost doubled the time without disease progression, with median progression-free survival reaching 10.8 months for Datroway-treated patients versus 5.6 months in the chemotherapy arm.

Mohit Manrao, head of AstraZeneca's U.S. oncology division, emphasized the importance of these results, stating, "For triple negative patients, whose disease moves very progressively every day, every week, every month, [this data] is a huge hope that science is delivering for them."

The study met both its primary endpoints, demonstrating a 43% reduction in patients' risk of disease progression or death. Tumor shrinkage was observed in 63% of participants given Datroway, compared to 29% of those on chemotherapy. The risk of death was also lowered by 21% with Datroway treatment.

Safety Profile and Regulatory Implications

While Datroway showed improved efficacy, researchers observed Grade 3 or higher treatment-related adverse events in 33% of the drug arm compared to 29% in the chemotherapy arm. Common side effects included mouth inflammation, fatigue, anemia, and low white blood cell counts. One participant in the Datroway group died from interstitial lung disease, which an independent committee concluded was related to the drug.

AstraZeneca plans to share the study results with global regulators to determine the next steps toward approval. Datroway is already approved for use in patients with previously treated metastatic HR-positive/HER2-negative breast cancer and certain types of advanced lung cancer.

Competitive Landscape

Datroway's success positions it to compete directly with Gilead's Trodelvy, another antibody-drug conjugate targeting TROP2. Trodelvy is currently approved for use in triple-negative breast cancer patients who have tried at least two systemic therapies. Recent data from a Phase 3 study presented at ESMO showed Trodelvy's superiority as a first-line treatment compared to chemotherapy, with a median progression-free survival of 9.7 months versus 6.9 months.

While analysts from Leerink noted the nuanced differences between the trials, they believe Datroway showed "a slightly better clinical profile" compared to Trodelvy, which "may ultimately command greater commercial share." However, the analysts emphasized that the differences in trial designs prevent a definitive determination of a superior product.