Daiichi Sankyo has discontinued the development of its next-generation cancer therapy, DS-9606, signaling another challenge for its antibody-drug conjugate (ADC) program.
“We’ve decided to discontinue its in-house development following a strategic portfolio review,” said Yuki Abe, Daiichi Sankyo’s head of research and development, during the company’s third-quarter 2025 earnings call. Abe addressed investors in Japanese, with his comments translated for international participants.
Abe noted that while the company had validated DS-9606’s potential in germ cell tumors, “there is room for making more development in that area.” He added, “given the portfolio perspective, we decided not to continue the in-house development in this field.”
DS-9606 is a claudin-6-directed ADC that utilizes Daiichi Sankyo’s modified pyrrolobenzodiazepine (mPBD) payload. This chemical agent targets and disrupts tumor cell DNA. The company had planned multiple ADCs featuring mPBDs, with DS-9606 intended as the first in this line.
Despite ending work on DS-9606, Abe stated that Daiichi Sankyo still sees value in the mPBD platform. He said “clinical programs will continue,” focusing on other targets and carrier antibodies.
Additionally, Daiichi Sankyo announced a delay in data release from its Phase III Avanzar study. This trial tests the breast cancer ADC Datroway together with AstraZeneca’s PD-L1 blocker Imfinzi as a first-line treatment for non-small cell lung cancer (NSCLC). Originally scheduled for release in late 2025, results are now expected later this year.
Datroway has encountered several setbacks over recent years. In May 2024, it failed to show significant improvement over docetaxel in a late-stage NSCLC trial. Subsequently, after launching a TROP2-based AI biomarker to identify NSCLC patients most likely to benefit from Datroway—a move described by David Fredrickson of AstraZeneca—the drug failed another Phase III trial for breast cancer patients later that year.
Following these outcomes, Daiichi Sankyo and AstraZeneca withdrew their application for Datroway’s use in advanced or metastatic nonsquamous NSCLC and instead submitted a new application targeting EGFR-mutated NSCLC patients who had undergone prior treatments. The U.S. Food and Drug Administration approved this indication in June last year. Datroway also holds approval for certain types of breast cancer.
