TROPION-Urothelial03: A phase 2/3 study of datopotamab deruxtecan (Dato-DXd) + platinum chemotherapy (CT) vs gemcitabine + platinum CT in participants with locally advanced or metastatic urothelial carcinoma (la/mUC) with progression on or after enfortumab vedotin (EV) + pembrolizumab (pembro).

TPS890 Background: Although first-line (1L) EV + pembrolizumab has improved outcomes for patients with la/mUC, most experience disease progression, highlighting an unmet need for novel therapies. TROP2 is a glycoprotein highly expressed in several epithelial tumors, including UC. Dato-DXd is a TROP2-directed antibody–drug conjugate comprising an anti-TROP2 monoclonal antibody, a tetrapeptide-based cleavable linker, and a topoisomerase I inhibitor payload (DXd), designed to induce selective tumor-cell death and reduce systemic exposure to the payload. Dato-DXd has demonstrated durable efficacy and a manageable safety profile in patients with la/mUC both as monotherapy (TROPION-PanTumor01 [NCT03401385]) and in combination with immunotherapy (TROPION-PanTumor03 [NCT05489211]). We describe a phase 2/3 trial comparing the efficacy and safety of Dato-DXd + platinum CT (carboplatin or cisplatin) vs gemcitabine + platinum CT in participants with la/mUC with disease progression on or after EV + pembrolizumab. Methods: TROPION-Urothelial03 (NCT07129993) is a global, multicenter, randomized, open-label, phase 2/3 trial. In part A (phase 2), ~60 participants will be randomized 1:1 to receive Dato-DXd 4 or 6 mg/kg + platinum CT. In part B (phase 3), ~570 participants will be randomized 1:1 to receive Dato-DXd at the recommended phase 3 dose (determined using part A data) + platinum CT vs gemcitabine + platinum CT. Randomization in part A is stratified by assignment of platinum CT (carboplatin vs cisplatin), and in part B, by assignment of platinum CT, presence vs absence of liver metastasis at screening, and time to progression on 1L EV + pembrolizumab ( < 6 vs ≥6 months). Study treatment continues until disease progression, unacceptable toxicity, withdrawal of consent, death, loss to follow-up, or other reasons per protocol. Radiographic tumor assessments occur every 6 weeks for 54 weeks, then every 12 weeks. The primary endpoint of part A is objective response rate (ORR) by investigator per Response Evaluation Criteria in Solid Tumours, version 1.1 (RECIST 1.1). The dual primary endpoints of part B are progression-free survival (PFS) by blinded independent central review (BICR) per RECIST 1.1 and overall survival (OS). Secondary endpoints include duration of response by investigator per RECIST 1.1 (part A), and PFS by investigator per RECIST 1.1 and ORR by BICR and investigator per RECIST 1.1 (part B). In part A, ORR will be summarized with 2-sided 95% exact confidence intervals using the Clopper–Pearson method by trial group. In part B, PFS and OS will be compared between trial groups using a log-rank test stratified by randomization stratification factors, with hazard ratios from the stratified Cox regression model. Clinical trial information: NCT07129993 .