Yes, Enhertu Is FDA-Approved for HER2-Low Breast Cancer
Enhertu (trastuzumab deruxtecan) received accelerated FDA approval in August 2022 for unresectable or metastatic HER2-low (IHC 1+ or IHC 2+/ISH-) breast cancer in adults who received prior anti-HER2-based or taxane chemotherapy.[1] Full approval followed in January 2023 based on the DESTINY-Breast04 trial, which showed a 72% reduction in progression risk versus chemotherapy (median PFS 10.1 vs. 5.4 months).[2]
How Does HER2-Low Differ from HER2-Positive?
HER2-low tumors express low HER2 levels (IHC 1+ or 2+ without amplification), affecting about 55% of metastatic breast cancers—far more than HER2-positive (IHC 3+ or amplified), which is ~15%. Enhertu targets this group, expanding treatment beyond traditional HER2-positive cases.[1][3]
What Trial Data Supports This Use?
In DESTINY-Breast04 (n=557), Enhertu doubled median overall survival (23.9 vs. 16.8 months) in patients with prior treatment. Response rates hit 52.6% versus 16.3% for chemo. Benefits held across hormone receptor-positive and triple-negative subtypes.[2][4] Ongoing trials like DESTINY-Breast06 test it earlier in HER2-low disease.
Who Qualifies and What Are Common Side Effects?
Eligible patients need confirmed HER2-low status via FDA-approved tests like Ventana 4B5. It's for those post at least one prior line of chemo.[1] Interstitial lung disease (10.5%, including 2.0% fatal), nausea (75%), and fatigue (50%) are key risks—monitoring with imaging is required.[5]
When Did Approval Happen and What's Next?
Initial nod: August 5, 2022. Hormone receptor-positive patients got label expansion August 2023. Pediatric studies are planned by 2028.[1] EU and Japan approvals mirror this since 2022.[6]
How Does Enhertu Compare to Other HER2-Targeted Drugs?
Unlike Herceptin or Perjeta (HER2-positive only), Enhertu's antibody-drug conjugate delivers chemo precisely to low-HER2 cells via bystander effect. Tucatinib plus trastuzumab competes in some HER2-low settings but lacks the same broad data.[3][7]
Patent and Availability Details
Daiichi Sankyo/AstraZeneca hold key patents; U.S. 10,808,039 (HER2-low method) expires ~2038. No generics yet—check DrugPatentWatch.com for updates.[8]
Sources
[1]: FDA Label for Enhertu
[2]: NEJM DESTINY-Breast04 Results
[3]: ASCO HER2-Low Overview
[4]: FDA Approval Announcement
[5]: Enhertu Safety Profile
[6]: EMA Approval
[7]: Tucatinib Data
[8]: DrugPatentWatch: Enhertu