Daiichi Sankyo Gains FDA Approval for Enhertu in Two Early-Stage HER2-Positive Breast Cancer Indications

Daiichi Sankyo's antibody-drug conjugate fam-trastuzumab deruxtecan-nxki (T-DXd, Enhertu) now carries two distinct FDA-approved indications in early-stage HER2-positive breast cancer, a regulatory outcome that extends ADC manufacturing obligations well beyond the metastatic setting and sharpens companion diagnostic compliance requirements across treatment sites.

The FDA approved both indications on May 15, 2026. The first covers neoadjuvant treatment of adults with HER2-positive (IHC 3+ or ISH+) Stage II or III breast cancer, administered as four cycles of T-DXd followed by taxane, trastuzumab, and pertuzumab (THP). The second addresses adjuvant treatment for patients with residual invasive disease following neoadjuvant HER2-targeted therapy. Both indications require patient selection via an FDA-authorized test, and the agency simultaneously approved two companion diagnostics: the PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody and the VENTANA HER2 Dual ISH DNA Probe Cocktail. QA and laboratory operations teams will need to confirm diagnostic device qualification is in place before T-DXd can be dispensed under either indication.

Efficacy data supporting the neoadjuvant indication came from DESTINY-Breast11 (NCT05113251), a 927-patient, randomized, open-label trial. The pathological complete response (pCR) rate in the T-DXd-THP arm reached 67.3% versus 56.3% for doxorubicin/cyclophosphamide followed by THP (p=0.003). Event-free survival and overall survival endpoints were not statistically controlled in that trial; supportive evidence was drawn from the adjuvant study. The adjuvant indication rests on DESTINY-Breast05 (NCT04622319), enrolling 1,635 patients. The 3-year invasive disease-free survival (IDFS) rate was 92.4% for T-DXd versus 83.7% for trastuzumab emtansine (T-DM1), with a hazard ratio of 0.47 (95% CI: 0.34, 0.66; p<0.0001). The 3-year disease-free survival result mirrored that finding at the same hazard ratio.

The recommended dose is 5.4 mg/kg every three weeks for both indications, with the neoadjuvant course running four cycles and the adjuvant course extending to a maximum of 14 cycles. The prescribing information carries a boxed warning for interstitial lung disease (ILD) and pneumonitis, alongside warnings for neutropenia and left ventricular dysfunction. For pharmacovigilance and CAPA programs, these signals are already established from the metastatic label; the expanded patient population in earlier disease stages increases the volume of adverse event monitoring obligations under 21 CFR Part 314 post-marketing commitments.

For manufacturing and supply chain operations, dual-indication approval at the neoadjuvant and adjuvant stages substantially broadens the eligible patient pool, placing immediate pressure on Daiichi Sankyo's ADC production capacity and cold-chain distribution infrastructure to meet demand without compromising sterility assurance or product quality standards.

The 3-year IDFS benchmark of 92.4% in DESTINY-Breast05 will serve as the reference outcome against which post-approval safety and effectiveness data are measured as real-world use scales.

Source: FDA Drugs@FDA via FDA.gov What's New: Drugs RSS Feed, May 15, 2026.