Datopotamab deruxtecan (Dato-DXd) in combination with durvalumab as first-line treatment for unresectable locally advanced or metastatic triple-negative breast cancer: results from arms 7 and 8 of the phase Ib/II BEGONIA study
Schmid P., Wang HC., Lynce F., Asselah J., Jung KH., Ma CX., Park YH., Chen SC., Wysocki PJ., Baird RD., Nowecki Z., Fernandes R., O’Shaughnessy J., Lord S., Hou MF., Tseng LM., Prady C., Rao-Melacini P., Stewart R., Warzyszyńska K., Vuković P., Im SA.
Background: BEGONIA (NCT03742102) is a phase Ib/II, Simon’s 2-stage, open-label, platform study evaluating the safety and efficacy of durvalumab, an anti-programmed death ligand-1 (PD-L1) antibody, combined with novel therapies, as first-line treatment for patients with unresectable locally advanced or metastatic triple-negative breast cancer (TNBC). Arms 7 and 8 of BEGONIA assessed the combination of datopotamab deruxtecan (Dato-DXd), a TROP2-directed antibody-drug conjugate, with durvalumab. Patients and methods: Arm 7 included patients regardless of tumor PD-L1 expression level. Arm 8 then enrolled patients with PD-L1-high tumors, as determined by local immunohistochemistry-based testing. In Arms 7 and 8, patients received Dato-DXd 6 mg/kg intravenously plus durvalumab 1120 mg intravenously every 3 weeks. Primary endpoints were safety and tolerability, and investigator-assessed confirmed objective response rate (cORR). Secondary endpoints included cORR (Part 1), duration of response (DoR), progression-free survival (PFS) per RECIST 1.1 and overall survival (OS). Results: Overall, 62 and 33 patients had received Dato-DXd and durvalumab in Arms 7 and 8, respectively. At data cutoff (29 November 2024), median study follow-up was 35.0 and 10.7 months in Arms 7 and 8, respectively. In Arm 7, cORR was 79.0% [95% confidence interval (CI) 66.8-88.3], median DoR was 17.6 months (95% CI 10.5-27.3), median PFS was 14.0 months (11.0-21.1) and median OS was not reached. In Arm 8, cORR was 81.8% (95% CI 64.5-93.0). The median DoR and median PFS for Arm 8 were immature given the short median follow-up (8.3 months in censored patients). The safety profile of the combination was manageable, with no new safety signals versus prior studies. Conclusions: First-line Dato-DXd plus durvalumab demonstrated substantial and durable antitumor activity in locally advanced unresectable or metastatic TNBC, regardless of PD-L1 status.