On January 15, 2021, the U.S. Food and Drug Administration (FDA) approved fam-trastuzumab deruxtecan-nxki (Enhertu®) for adult patients with locally advanced or metastatic HER2-positive gastric or gastroesophageal (GEJ) adenocarcinoma who have received a prior trastuzumab-based regimen.
Efficacy was evaluated in a multicenter, open-label, randomized trial (DESTINY-Gastric01; NCT03329690) of 188 patients with HER2-positive locally advanced or metastatic gastric or GEJ adenocarcinoma who had progressed on at least two prior regimens, including trastuzumab, a fluoropyrimidine- and platinum-containing chemotherapy. Patients were randomized 2:1 to receive either fam-trastuzumab deruxtecan-nxki 6.4 mg/kg via IV infusion every three weeks or the physician’s choice of either irinotecan or paclitaxel monotherapy.
The main efficacy outcome measures were overall survival (OS) and objective response rate (ORR) assessed by independent central review (Response Evaluation Criteria in Solid Tumors 1.1) in the intent-to-treat population. Additional efficacy outcome measures were progression-free survival (PFS) and duration of response (DOR).
OS was 12.5 months (95% CI = 9.6, 14.3) in the fam-trastuzumab deruxtecan-nxki arm compared to 8.4 months (95% CI = 6.9, 10.7) in the irinotecan or paclitaxel arm (hazard ratio = 0.59; 95% CI = 0.39, 0.88, p = 0.0097). Confirmed ORR was 40.5% (95% CI = 31.8, 49.6) in the fam-trastuzumab deruxtecan-nxki arm compared to 11.3% (95% CI = 4.7, 21.9) for those receiving irinotecan or paclitaxel. Median PFS was 5.6 months (95% CI = 4.3, 6.9) in the fam-trastuzumab deruxtecan-nxki arm compared to 3.5 months (95% CI = 2.0, 4.3) in the irinotecan or paclitaxel arm. Median DOR was 11.3 months (95% CI = 5.6, not reached) versus 3.9 months (95% CI = 3.0, 4.9), respectively.
The most common adverse reactions (≥ 20%), including laboratory abnormalities, were anemia, leukopenia, neutropenia, lymphocytopenia, thrombocytopenia, nausea, decreased appetite, increased aspartate aminotransferase, fatigue, increased blood alkaline phosphatase, increased alanine aminotransferase, diarrhea, hypokalemia, vomiting, constipation, increased blood bilirubin, pyrexia, and alopecia. The prescribing information includes a boxed warning to advise healthcare professionals of the risks of interstitial lung disease and embryofetal toxicity.
The recommended fam-trastuzumab deruxtecan-nxki dose for gastric cancer is 6.4 mg/kg administered via IV infusion once every three weeks (21-day cycle) until patients experience disease progression or unacceptable toxicity.
The review used Assessment Aid, a voluntary submission from the applicant to facilitate FDA’s assessment. FDA approved the application approximately six weeks ahead of its goal date.
FDA granted the application priority review. Fam-trastuzumab deruxtecan-nxki was granted breakthrough therapy and orphan drug designations in gastric cancer. A description of FDA expedited programs is in the Guidance for Industry—Expedited Programs for Serious Conditions—Drugs and Biologics.
Healthcare professionals should report all serious adverse events suspected to be associated with the use of any medicine and device to FDA’s MedWatch Reporting System or by calling 800-FDA-1088.