BASKING RIDGE, N.J. and RAHWAY, N.J., September 15, 2025 – Daiichi Sankyo and Merck (known as MSD outside the U.S. and Canada) today announced that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation (BTD) for raludotatug deruxtecan (R-DXd) in adult patients with platinum-resistant ovarian, primary peritoneal, or fallopian tube cancers expressing CDH6, who have received prior treatment with bevacizumab.
The designation marks the first Breakthrough Therapy for raludotatug deruxtecan and the second since the inception of the Daiichi Sankyo–Merck collaboration, underscoring the momentum of their joint oncology pipeline.
Science Significance
Raludotatug deruxtecan is a specifically engineered, potential first-in-class CDH6-directed antibody-drug conjugate (ADC) leveraging Daiichi Sankyo’s DXd ADC technology. Unlike traditional chemotherapies, R-DXd selectively targets cadherin-6 (CDH6), a protein overexpressed in up to 65% of ovarian tumors, delivering a potent topoisomerase I inhibitor payload directly into tumor cells.
Early clinical evidence, including subgroup analyses from a Phase 1 study and the ongoing REJOICE-Ovarian01 Phase 2/3 trial, suggests that R-DXd could offer substantial improvements over current therapies in objective response rate, progression-free survival, and disease control rate.
If validated in larger trials, R-DXd could represent a paradigm shift in how platinum-resistant ovarian cancers are treated, moving beyond nonspecific chemotherapies to precision-engineered ADCs.
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Regulatory Significance
The FDA’s Breakthrough Therapy Designation is intended to accelerate the development and review of medicines showing preliminary evidence of substantial clinical benefit over existing options for serious conditions.
By granting this status, the FDA recognizes both the urgency of treating platinum-resistant ovarian cancer, a setting with poor prognosis, and the promise of CDH6-directed therapy. This designation enables closer guidance from the FDA, eligibility for rolling submissions, and priority review upon Biologics License Application (BLA) submission.
The regulatory milestone adds raludotatug deruxtecan to Daiichi Sankyo’s growing portfolio of 15 BTDs across oncology, strengthening its position as a global leader in ADC innovation.
Business Significance
For Daiichi Sankyo and Merck, this designation reinforces the strategic and financial value of their ADC collaboration. The partnership now spans multiple assets, including HER3-DXd, I-DXd, gocatamig, and R-DXd, positioning the companies at the forefront of precision oncology.
The platinum-resistant ovarian cancer market represents a significant unmet need and commercial opportunity. In the U.S. alone, over 330,000 women are living with ovarian cancer, and the majority eventually develop platinum resistance. Analysts project ADCs to drive a multi-billion-dollar oncology segment by 2030, with R-DXd expected to capture meaningful share if approved.
The BTD designation signals strong market potential and investor confidence in the Daiichi Sankyo–Merck alliance.
Patients’ Significance
For patients, platinum resistance often marks a devastating turn, with median survival dropping to as little as two years. Current options—mainly chemotherapy—deliver modest benefits with substantial toxicity.
By preventing CD11c+ immune cell infiltration into the brain, R-DXd addresses a novel biologic pathway of neuroinflammation and tumor progression. If approved, it could provide patients with a therapy that not only extends survival but also preserves quality of life through more targeted action.
This designation brings new hope to thousands of women and families impacted by one of the deadliest gynecological cancers.
Policy Significance
The FDA’s action reflects a broader regulatory emphasis on accelerating innovation in women’s health and oncology. With ovarian cancer ranking as the fifth leading cause of cancer death among women worldwide, public health policy increasingly supports initiatives to expand access to cutting-edge therapies.
The BTD designation aligns with U.S. government goals to reduce cancer mortality, as outlined in the Cancer Moonshot Initiative, and highlights the importance of public–private partnerships in speeding delivery of promising medicines.
Such designations not only streamline drug development but also set policy precedents for future approvals of precision medicines.
Transaction Highlights
The U.S. FDA has granted Breakthrough Therapy Designation (BTD) to raludotatug deruxtecan (R-DXd), a first-in-class, CDH6-directed antibody-drug conjugate (ADC) jointly developed by Daiichi Sankyo and Merck, for the treatment of adult patients with platinum-resistant ovarian, primary peritoneal, or fallopian tube cancers expressing CDH6 who have previously received bevacizumab. This marks the first BTD for raludotatug deruxtecan and the second BTD since the launch of the Daiichi Sankyo–Merck collaboration, reinforcing the strategic importance of their partnership. The FDA’s decision is based on encouraging results from a phase 1 trial and ongoing phase 2/3 REJOICE-Ovarian01 trial, which demonstrated promising safety and efficacy signals in this high-need population. With this designation, raludotatug deruxtecan becomes part of Daiichi Sankyo’s expanding ADC pipeline, now accounting for 15 Breakthrough Therapy Designations across its oncology portfolio, underscoring its leadership in next-generation ADC development.
Source: Merck & Co., Inc. Press Release
