ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy
Daiichi Sankyo (TSE: 4568) and AstraZeneca’s (LSE/STO/Nasdaq: AZN) ENHERTU® (fam-trastuzumab deruxtecan-nxki) has been approved in the U.S. for the treatment of adult patients with unresectable or metastatic hormone receptor (HR) positive, HER2 low (IHC 1+ or IHC 2+/ISH-) or HER2 ultralow (IHC 0 with membrane staining) breast cancer, as determined ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy by an FDA-approved test, that has progressed on one or more endocrine therapies in the metastatic setting.
ENHERTU is a specifically engineered HER2 directed DXd antibody drug conjugate (ADC) discovered by Daiichi Sankyo and being jointly developed and commercialized by Daiichi Sankyo and AstraZeneca.
This approval, which is based on results from the DESTINY-Breast06phase 3 trial presentedat the 2024 American Society of Clinical Oncology (#ASCO24) Annual Meeting and ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy published in The New England Journal of Medicine, follows Priority Review and Breakthrough Therapy Designation by the FDA for ENHERTU in this indication.
In the DESTINY-Breast06 trial, ENHERTU demonstrated a 36% reduction in the risk of disease progression or death versus chemotherapy in the overall trial population of patients with chemotherapy-naïve HR positive, HER2 low or HER2 ultralow metastatic breast cancer (n=866) (hazard ratio [HR] 0.64; 95% confidence interval [CI]: 0.54-0.76; p<0.0001). A median progression-free survival (PFS) of 13.2 months (95% CI: 12.0-15.2) was seen in patients treated with ENHERTU compared to 8.1 months (95% CI: 7.0-9.0) in patients treated with chemotherapy.
The confirmed objective response rate (ORR) ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy in the overall trial population was 62.6% (95% CI: 57.6-67.4) in the ENHERTU arm versus 34.4% (95% CI: 29.7-39.4) in the ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy chemotherapy arm as assessed by blinded independent central review (BICR). There were 10 (2.5%) complete responses (CRs) and 236 (60.1%) partial responses (PRs) seen in the ENHERTU arm compared to zero (0%) CRs and 134 (34.4%) PRs in the chemotherapy arm. The median duration of response (DOR) was 14.3 months in the ENHERTU arm (95% CI: 12.5-15.9) versus 8.6 months in the chemotherapy arm (95% CI: 6.9-11.5) as assessed by BICR.
In the HER2 low population (n=713) (HR 0.62; 95% CI: 0.52-0.75; p<0.0001), median PFS was 13.2 months (95% CI: 11.4-15.2) in the ENHERTU arm compared to 8.1 months (95% CI: 7.0-9.0) in the chemotherapy arm. Confirmed ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy ORR was 62.0% (95% CI: 56.5-67.3) versus 35.2% (95% CI: 30.0-40.7) in the chemotherapy arm. There were 9 (2.8%) CRs and 193 (59.2%) PRs seen in the ENHERTU arm compared to zero (0%) CRs and 114 (35.2%) PRs in the chemotherapy arm. ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy Median DOR was 14.1 months (95% CI: 11.9-15.9) versus 8.6 months (95% CI: 6.7-11.3) in the chemotherapy arm.
An exploratory analysis of the HER2 ultralow population (n=153) (HR 0.76; 95% CI: 0.49-1.17) showed the clinically meaningful improvement in PFS was consistent between ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy patients with HER2 low and HER2 ultralow expression, with 15.1 months (95% CI: 10.0-17.3) reported in the ENHERTU arm and 8.3 months (95% CI: 5.8-15.2) in the chemotherapy arm. Confirmed ORR was 65.7% (95% CI: 53.1-76.8) in the ENHERTU arm and 30.8% (95% CI: 19.9-43.4) in the chemotherapy arm. Median DOR was 14.3 months (95% CI: 11.8-not estimable [NE]) versus 14.1 months (95% CI: 5.9-NE) in the ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy chemotherapy arm.
“Endocrine therapy is typically used in the initial treatment of HR positive metastatic breast cancer and following progression, subsequent chemotherapy is associated with poor outcomes,” said Aditya Bardia, MD, MPH, Program Director of Breast Oncology and Director of Translational Research Integration, UCLA Health Jonsson Comprehensive Cancer Center and Investigator in the DESTINY-Breast06 trial. “With a median progression-free survival exceeding one year and a response rate of more than 60 percent, trastuzumab deruxtecan offers a potential new standard of care for patients with hormone receptor positive, HER2 low or HER2 ultralow metastatic breast cancer following endocrine therapy.”
“We are excited to see more treatment options for these patients which enable more personalized care,” said Krissa Smith, Vice President, Education, Susan G. Komen. “It is critical for patients to understand the HER2 status of their metastatic breast cancer to help them make informed treatment decisions. Patients with tumors that are HER2 low or HER2 ultralow ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy now have more options to consider with their healthcare team.”
ENHERTU is approved with Boxed WARNINGS for ENHERTU® Approved in U.S. for HER2-Low Metastatic Breast Cancer Post-Endocrine Therapy interstitial lung disease (ILD)/pneumonitis and Embryo-Fetal toxicity. The safety of ENHERTU was evaluated in 434 patients with unresectable or metastatic HER2 low (IHC 1+ or IHC 2+/ISH-) or HER2 ultralow (IHC 0 with membrane staining) breast cancer who received ENHERTU (5.4 mg/kg) in DESTINY-Breast06. The most common (≥20%) adverse reactions, including laboratory abnormalities, were decreased white blood cell count, decreased neutrophil count, nausea, decreased hemoglobin, decreased lymphocyte count, fatigue, decreased platelet count, alopecia, increased alanine aminotransferase, increased blood alkaline phosphatase, increased aspartate aminotransferase, decreased blood potassium, diarrhea, vomiting, constipation, decreased appetite, COVID-19 and musculoskeletal pain. Serious adverse reactions occurred in 20% of patients receiving ENHERTU. Serious adverse reactions in >1% of patients who received ENHERTU were ILD/pneumonitis, COVID-19, febrile neutropenia and hypokalemia. Fatalities due to adverse reactions occurred in 2.8% of patients.
“ENHERTU continues to redefine the classification and treatment of HR positive metastatic breast cancer with important new data across the spectrum of HER2 expression,” said Ken Keller, Global Head of Oncology Business, and President and CEO, Daiichi Sankyo, Inc. “Today’s approval underscores our ongoing commitment to realizing the full potential of this innovative antibody drug conjugate and represents another paradigm shift in how certain breast cancers can be treated.”
“Building on the practice-changing previous approvals for ENHERTU, this new approval brings this important medicine to an earlier treatment setting and a broader patient population with HER2 expressing metastatic breast cancer,” said Dave Fredrickson, Executive Vice President, Oncology Hematology Business Unit, AstraZeneca. “The approval also highlights the importance of testing metastatic breast cancer tumors for detectable staining with a standard IHC test to identify those who may be eligible for treatment with ENHERTU following endocrine therapy.”
Daiichi Sankyo and AstraZeneca are committed to ensuring that patients in the U.S. who are prescribed ENHERTU can access the medication and receive necessary financial support. Provider and patient support, reimbursement and distribution for ENHERTU in the U.S. will be accessible by visiting www.ENHERTU4U.comor calling 1-833-ENHERTU (1-833-364-3788).
Please visit www.ENHERTU.comfor full Prescribing Information, including Boxed WARNINGS, and Medication Guide.
Financial Considerations
Following this approval in the U.S., an amount of $175 million is due from AstraZeneca to Daiichi Sankyo as a milestone payment for the HER2 low and HER2 ultralow chemotherapy-naïve breast cancer indication. Sales of ENHERTU in the U.S. are recognized by Daiichi Sankyo. For further details on the financial arrangements, please consult the collaboration agreement from March 2019.
About DESTINY-Breast06
DESTINY-Breast06 is a global, randomized, open-label, phase 3 trial evaluating the efficacy and safety of ENHERTU (5.4 mg/kg) versus investigator’s choice of chemotherapy (capecitabine, paclitaxel or nab paclitaxel) in patients with HR positive, HER2 low (IHC 1+ or IHC 2+/ISH-) or HER2 ultralow (defined as IHC 0 with membrane staining) advanced or metastatic breast cancer. Patients in the trial had no prior chemotherapy for advanced or metastatic disease and received at least two lines of prior endocrine therapy in the metastatic setting. Patients also were eligible if they had received one prior line of endocrine therapy combined with a CDK4/6 inhibitor in the metastatic setting and experienced disease progression within six months of starting first-line treatment or received endocrine therapy as an adjuvant treatment and experienced disease recurrence within 24 months.
HER2 IHC status was confirmed by a central laboratory and determined based on the most recent evaluable HER2 IHC sample prior to randomization. In tumor samples from patients screened for trial eligibility, nearly two-thirds of tumors previously assessed as IHC 0 at a local laboratory were re-classified as HER2 low or HER2 ultralow upon central analysis of the archival tumor sample. It was also observed that approximately 85% to 90% patients with HR positive, HER2 negative metastatic breast cancer may have actionable levels of HER2 expression.
The primary endpoint of DESTINY-Breast06 is PFS in the HR positive, HER2 low patient population as measured by BICR. Key secondary endpoints include PFS by BICR in the overall trial population (HER2 low and HER2 ultralow), OS in patients in the HER2 low patient population and OS in the overall trial population. Other secondary endpoints include ORR, DOR, time to first subsequent treatment or death, time to second subsequent treatment or death and safety. Analysis of the HER2 ultralow subgroup was not powered to demonstrate statistical significance.
DESTINY-Breast06 enrolled 866 patients (n=713 for HER2 low and n=153 for HER2 ultralow) in Asia, Europe, North America, Oceania and South America. For more information about the trial, visit ClinicalTrials.gov.
About Breast Cancer and HER2 Expression
Breast cancer is the second most common cancer and one of the leading causes of cancer-related deaths worldwide.1 More than two million breast cancer cases were diagnosed in 2022 with more than 665,000 deaths globally.1 In the U.S., more than 300,000 cases of breast cancer are diagnosed annually.2 While survival rates are high for those diagnosed with early breast cancer, only about 30% of patients diagnosed with or who progress to metastatic disease are expected to live five years following diagnosis.3
HR positive, HER2 negative is the most common breast cancer subtype, accounting for approximately 70% of all breast cancers.3 HER2 is a tyrosine kinase receptor growth-promoting protein expressed on the surface of many types of tumors, including breast cancer.4 Patients with high levels of HER2 expression (IHC 3+ or IHC2+/ISH+) are classified as HER2 positive and treated with HER2 targeted therapies, representing approximately 15% to 20% of all breast cancers.5 Historically, tumors that were not classified as HER2 positive were classified as HER2 negative, despite the fact that many of these tumors still carry some level of HER2 expression.6
Endocrine therapy is widely given consecutively in the early lines of treatment for HR positive metastatic breast cancer. However, after initial therapy, further efficacy with additional endocrine treatment is often limited.7 The current standard of care following endocrine therapy is chemotherapy, which is associated with poor response rates and outcomes.7,8,9,10
Prior to the approvals of ENHERTU in HER2 low and HER2 ultralow metastatic breast cancer based on the DESTINY-Breast04and DESTINY-Breast06trials, there were no targeted therapies approved specifically for these patient populations.11,12
About ENHERTU
ENHERTU (trastuzumab deruxtecan; fam-trastuzumab deruxtecan-nxki in the U.S. only) is a HER2 directed ADC. Designed using Daiichi Sankyo’s proprietary DXd ADC Technology, ENHERTU is the lead ADC in the oncology portfolio of Daiichi Sankyo and the most advanced program in AstraZeneca’s ADC scientific platform. ENHERTU consists of a HER2 monoclonal antibody attached to a number of topoisomerase I inhibitor payloads (an exatecan derivative, DXd) via tetrapeptide-based cleavable linkers.
ENHERTU (5.4 mg/kg) is approved in more than 75 countries worldwide for the treatment of adult patients with unresectable or metastatic HER2 positive (immunohistochemistry [IHC] 3+ or in-situ hybridization (ISH)+) breast cancer who have received a prior anti-HER2-based regimen, either in the metastatic setting or in the neoadjuvant or adjuvant setting, and have developed disease recurrence during or within six months of completing therapy based on the results from the DESTINY-Breast03 trial.
ENHERTU (5.4 mg/kg) is approved in more than 75 countries worldwide for the treatment of adult patients with unresectable or metastatic HER2 low (IHC 1+ or IHC 2+/ISH-) breast cancer who have received a prior systemic therapy in the metastatic setting or developed disease recurrence during or within six months of completing adjuvant chemotherapy based on the results from the DESTINY-Breast04 trial.
ENHERTU (5.4 mg/kg) is approved in the U.S. for the treatment of adult patients with unresectable or metastatic hormone receptor (HR) positive, HER2 low (IHC 1+ or IHC 2+/ISH-) or HER2 ultralow (IHC 0 with membrane staining) breast cancer, as determined by an FDA-approved test, that has progressed on one or more endocrine therapies in the metastatic setting based on the results from the DESTINY-Breast06 trial.
ENHERTU (5.4 mg/kg) is approved in more than 50 countries worldwide for the treatment of adult patients with unresectable or metastatic NSCLC whose tumors have activating HER2 (ERBB2) mutations, as detected by a locally or regionally approved test, and who have received a prior systemic therapy based on the results from the DESTINY-Lung02 and/or DESTINY-Lung05 trials. Continued approval in China and the U.S. for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.
ENHERTU (6.4 mg/kg) is approved in more than 65 countries worldwide for the treatment of adult patients with locally advanced or metastatic HER2 positive (IHC 3+ or IHC 2+/ISH+) gastric or gastroesophageal junction (GEJ) adenocarcinoma who have received a prior trastuzumab-based regimen based on the results from the DESTINY-Gastric01, DESTINY-Gastric02 and/or DESTINY-Gastric06 trials. Continued approval in China for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.
ENHERTU (5.4 mg/kg) is approved in Brazil, Israel, Russia and the U.S. for the treatment of adult patients with unresectable or metastatic HER2 positive (IHC 3+) solid tumors who have received prior systemic treatment and have no satisfactory alternative treatment options based on efficacy results from the DESTINY-PanTumor02, DESTINY-Lung01 and DESTINY-CRC02 trials. Continued approval for this indication in the U.S. may be contingent upon verification and description of clinical benefit in a confirmatory trial.
About the ENHERTU Clinical Development Program
A comprehensive global clinical development program is underway evaluating the efficacy and safety of ENHERTU monotherapy across multiple HER2 targetable cancers. Trials in combination with other anticancer treatments, such as immunotherapy, also are underway.
About the Daiichi Sankyo and AstraZeneca Collaboration
Daiichi Sankyo and AstraZeneca entered into a global collaboration to jointly develop and commercialize ENHERTU in March 2019and DATROWAY® inJuly 2020, except in Japan where Daiichi Sankyo maintains exclusive rights for each ADC. Daiichi Sankyo is responsible for the manufacturing and supply of ENHERTU and DATROWAY.
About the ADC Portfolio of Daiichi Sankyo
The Daiichi Sankyo ADC portfolio consists of seven ADCs in clinical development crafted from two distinct ADC technology platforms discovered in-house by Daiichi Sankyo.
The ADC platform furthest in clinical development is Daiichi Sankyo’s DXd ADC Technology where each ADC consists of a monoclonal antibody attached to a number of topoisomerase I inhibitor payloads (an exatecan derivative, DXd) via tetrapeptide-based cleavable linkers. The DXd ADC portfolio currently consists of ENHERTU, a HER2 directed ADC, and DATROWAY, a TROP2 directed ADC, which are being jointly developed and commercialized globally with AstraZeneca. Patritumab deruxtecan (HER3-DXd), a HER3 directed ADC, ifinatamab deruxtecan (I-DXd), a B7-H3 directed ADC, and raludotatug deruxtecan (R-DXd), a CDH6 directed ADC, are being jointly developed and commercialized globally with Merck & Co., Inc, Rahway, NJ, USA. DS-3939, a TA-MUC1 directed ADC, is being developed by Daiichi Sankyo.
The second Daiichi Sankyo ADC platform consists of a monoclonal antibody attached to a modified pyrrolobenzodiazepine (PBD) payload. DS-9606, a CLDN6 directed PBD ADC, is the first of several planned ADCs in clinical development utilizing this platform.
Ifinatamab deruxtecan, patritumab deruxtecan, raludotatug deruxtecan, DS-3939 and DS-9606 are investigational medicines that have not been approved for any indication in any country. Safety and efficacy have not been established.
