The Food and Drug Administration ( FDA ) has approved Enhertu ( fam-Trastuzumab Deruxtecan-nxki; Trastuzumab Deruxtecan ) for adult patients with unresectable or metastatic HER2-low ( IHC 1+ or IHC 2+/ISH‑ ) breast cancer who have received a prior chemotherapy in the metastatic setting or developed disease recurrence during or within six months of completing adjuvant chemotherapy.
Efficacy was based on DESTINY-Breast04, a randomized, multicenter, open-label clinical trial that enrolled 557 patients with unresectable or metastatic HER2-low breast cancer.
The trial included two cohorts: 494 hormone receptor-positive ( HR+ ) patients and 63 hormone receptor-negative ( HR-negative ) patients. HER2-low expression was defined as IHC 1+ or IHC 2+/ISH-, determined at a central laboratory.
Patients were randomized ( 2:1 ) to receive either Enhertu 5.4 mg/kg ( n=373 ) by intravenous infusion every 3 weeks or physician’s chemotherapy choice ( n=184, including Eribulin, Capecitabine, Gemcitabine, nab-Paclitaxel, or Paclitaxel ).
The primary efficacy measure was progression-free survival ( PFS ) in patients with HR+ breast cancer, assessed by blinded independent central review using RECIST 1.1.
Secondary efficacy measures were PFS in the overall population ( all randomized HR+ and HR-negative patients ), overall survival ( OS ) in HR+ patients, and OS in the overall population.
The median age of patients was 57 years ( range: 28 to 81 ) and 24% were 65 or older. Selected demographics were reported as follows: 99.6% female, 48% White, 40% Asian, 2% Black or African American, 3.8% Hispanic/Latino.
Median progression-free survival in the HR+ cohort was 10.1 months ( 95% CI: 9.5, 11.5 ) in the Enhertu arm and 5.4 months ( 95% CI: 4.4, 7.1 ) in the chemotherapy arm ( hazard ratio [ HR ] 0.51; 95% CI: 0.40, 0.64; p less than 0.0001 ).
Median PFS in the overall population was 9.9 months ( 95% CI: 9.0, 11.3 ) in the Enhertu arm and 5.1 months ( 95% CI: 4.2, 6.8 ) for those receiving chemotherapy ( HR=0.50; 95% CI: 0.40, 0.63; p less than 0.0001 ).
In the HR+ cohort, median overall survival was 23.9 months ( 95% CI: 20.8, 24.8 ) and 17.5 months ( 95% CI: 15.2, 22.4 ) in the Enhertu and chemotherapy arms, respectively ( HR=0.64; 95% CI: 0.48, 0.86; p=0.0028 ).
In the overall population, median overall survival was 23.4 months ( 95% CI: 20.0, 24.8 ) in the Enhertu arm versus 16.8 months ( 95% CI: 14.5, 20.0 ) in the chemotherapy arm ( HR=0.64; 95% CI: 0.49, 0.84; p=0.001 ).
The most common adverse reactions ( incidence 20% or more ) in patients receiving Enhertu in this trial were nausea, fatigue, alopecia, vomiting, anemia, constipation, decreased appetite, diarrhea, and musculoskeletal pain.
The prescribing information includes a Boxed Warning advising health professionals of the risk of interstitial lung disease and embryo-fetal toxicity.
The recommended Enhertu dose for breast cancer is 5.4 mg/kg given as an intravenous infusion once every 3 weeks ( 21-day cycle ) until disease progression or unacceptable toxicity. ( Xagena )
Source: FDA, 2022