The United States FDA has granted Breakthrough Therapy Designation (BTD) to raludotatug deruxtecan (R-DXd), an investigational antibody-drug conjugate, for the treatment of CDH6-expressing platinum-resistant ovarian, primary peritoneal, or fallopian tube cancers in adults who have previously received bevacizumab. 

The designation, announced on September 15, 2025 by Daiichi Sankyo and Merck also known as MSD, is designed to speed up the development and approval of R-DXd, which targets cadherin-6 (CDH6), a biomarker overexpressed in around 65% of ovarian tumours. The FDA made its judgement on preliminary clinical data from a Phase 1 trial and the current REJOICE-Ovarian01 Phase 2/3 research. 

The BTD represents demonstrated improvements in clinically relevant outcomes over existing medications for platinum-resistant ovarian cancer, a disease with few treatment choices and a dismal prognosis. Patients with platinum-resistant illness often have a median overall survival of fewer than two years after recurrence. 

Data from the Phase 1 study, which were presented at recent conferences including the European Society for Medical Oncology (ESMO) and the Society for Gynaecologic Oncology (SGO), showed promising response rates in a subset of patients with CDH6-expressing tumours. The worldwide REJOICE-Ovarian01 experiment is now testing R-DXd at various dosages in roughly 710 individuals. 

Ovarian cancer continues to be a substantial health burden, with over 324,000 new cases identified globally in 2022. Platinum resistance develops in 70-80% of individuals with severe illness, creating a huge unmet need for viable treatments. 

CDH6-directed therapy is a unique technique in cancer, as no treatments that target this biomarker are currently licensed. R-DXd employs a topoisomerase I inhibitor payload coupled to an anti-CDH6 antibody, a technique intended to deliver cytotoxic chemicals directly to cancer cells. 

The Breakthrough Designation will allow for more frequent FDA contacts and faster review processes for R-DXd. Ongoing REJOICE-Ovarian01 studies will continue to evaluate primary outcomes such as objective response rate and progression-free survival, with findings anticipated in the next years. 

Global health experts emphasise the importance of targeted medicines in increasing ovarian cancer survival rates, but availability in low-resource areas remains a concern. 

Final clearance will be based on the findings of the current Phase 3 study and subsequent regulatory scrutiny.