SUMMARY: The HER or erbB family of receptors consist of HER1, HER2, HER3 and HER4. Approximately 15-20% of invasive breast cancers as well as advanced Gastric and GastroEsophageal (GE) junction cancers overexpress or have amplification of the HER2 oncogene. These patients often receive first line treatment with a combination of chemotherapy plus anti-HER2 antibody. Several other cancer types including gynecologic and urothelial cancers overexpress HER oncogene.
ENHERTU® (Trastuzumab Deruxtecan) is an Antibody-Drug Conjugate (ADC) composed of a humanized monoclonal antibody specifically targeting HER2, with the amino acid sequence similar to Trastuzumab, a cleavable tetrapeptide-based linker, and a potent cytotoxic Topoisomerase I inhibitor as the cytotoxic drug (payload). ENHERTU® has a favorable pharmacokinetic profile and the tetrapeptide-based linker is stable in the plasma and is selectively cleaved by cathepsins that are up-regulated in tumor cells. Unlike KADCYLA® (ado-Trastuzumab emtansine), another ADC targeting HER2, ENHERTU® has a higher drug-to-antibody ratio (8 versus 4), released payload easily crosses the cell membrane with resulting potent cytotoxic effect on neighboring tumor cells regardless of target expression, and the released cytotoxic agent (payload) has a short half-life, thus minimizing systemic exposure.
ENHERTU® is approved by the FDA for use in unresectable or metastatic HER2-positive breast cancer, HER2-low breast cancer, HER2-mutant non–small cell lung cancer, and locally advanced or metastatic HER2-positive gastric cancer. ENHERTU® in a Phase I trial, demonstrated clinically meaningful activity in multiple advanced solid tumors expressing HER2 oncogene.
DESTINY-PanTumor-02 is an international, open-label Phase II study conducted to evaluate the effectiveness of ENHERTU® in patients with HER2-expressing biliary tract, bladder, cervical, endometrial, ovarian, pancreatic, or other tumors. This study involved 267 patients (N=267) across 7 different cohorts, including 6 tumor-specific cohorts (urothelial bladder, biliary tract, cervical, endometrial, ovarian, and pancreatic cancers) as well as a rare tumor cohort that included several other tumor types for which ENHERTU® is currently either not available or not being investigated (including head and neck cancers and intestinal adenocarcinoma). Patients with breast, gastric, colorectal and non-small cell lung cancers were excluded. Patients in this study had HER2-expressing (IHC 3+ or IHC 2+) locally advanced or metastatic disease that progressed after at least one systemic treatment or that had no treatment options. Among those studied 75 patients were IHC 3+ and 125 were IHC 2+ by central testing. Study patients were treated with at least one dose of ENHERTU® 5.4 mg/kg IV every 3 weeks and efficacy and safety were analyzed in all patients who received one or more doses of ENHERTU®. The Primary endpoint was investigator-assessed confirmed Objective Response Rate (ORR). Secondary endpoints included Duration of Response (DOR), Disease Control Rate, Progression Free Survival (PFS), Overall Survival, and Safety.
At data cutoff and after a median follow-up, 9.7 months, the ORR among all patients was 37.1% with a median DOR of 11.8 months. In patients with IHC 3+ expression, the ORR was 61.3% and the median DOR was 22.1 months whereas among those patients with IHC 2+ expression, the ORR was 27.2% and the median DOR was 9.8 months.
Treatment with ENHERTU resulted in the following Objective Response Rates across different tumor types:
• Endometrial cancer: 57.5% for all patients, 84.6% for IHC 3+, and 47.1% for IHC 2+
• Cervical cancer: 50% for all patients, 75% for IHC 3+, 40% for IHC 2+
• Ovarian cancer: 45% for all patients, 63.6% for IHC 3+, 36.8% for IHC 2+
• Urothelial cancer: 39% for all patients, 56.3% for IHC 3+, 35% for IHC 2+
• Biliary tract cancer: 22% for all patients, 56.3% for IHC 3+, 0% for IHC 2+
• Pancreatic cancer: 4% for all patients, 0% for IHC 3+, 5.3% for IHC 2+
The most common treatment-related side effects were nausea, fatigue, and cytopenias and there were no new safety signals.
It was concluded from this study results that ENHERTU® is a potential new treatment option for patients with HER2-expressing solid tumors, based on the encouraging Objective Response Rate, durable clinical benefit, and a manageable safety profile, in this heavily pretreated population. The authors added that this is the first tumor-agnostic global study of ENHERTU® in a broad range of HER2-expressing solid tumors.
Efficacy and safety of trastuzumab deruxtecan (T-DXd) in patients (pts) with HER2-expressing solid tumors: DESTINY-PanTumor02 (DP-02) interim results. Meric-Bernstam F, Makker V, Oaknin A, et al. J Clin Oncol 41, 2023 (suppl 17; abstr LBA3000)
