On August 19, 2024 Daiichi Sankyo and Astrazeneca reported that ENHERTU (fam-trastuzumab deruxtecan-nxki) has been granted Breakthrough Therapy Designation (BTD) in the U.S. for the treatment of unresectable or metastatic hormone receptor positive HER2 low (IHC 1+ or IHC 2+/ISH-) or HER2 ultralow (IHC >0 <1+) breast cancer patients who have received either two lines of endocrine therapy in the metastatic setting, or one line of endocrine therapy if they had demonstrated disease progression within six months of starting first-line treatment with endocrine therapy in combination with a CDK4/6 inhibitor or within 24 months of the start of adjuvant endocrine therapy (Press release, Daiichi Sankyo, AUG 19, 2024, View Source [SID1234645992]).
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ENHERTU is a specifically engineered HER2 directed DXd antibody drug conjugate (ADC) discovered by Daiichi Sankyo (TSE: 4568) and being jointly developed and commercialized by Daiichi Sankyo and AstraZeneca (LSE/STO/Nasdaq: AZN). The U.S. Food and Drug Administration (FDA) BTD is designed to accelerate the development and regulatory review of potential new medicines that are intended to treat a serious condition and address a significant unmet medical need. The medicine needs to have shown encouraging preliminary clinical results that demonstrate substantial improvement on a clinically significant endpoint over available medicines.
The FDA granted this BTD based on data from the DESTINY-Breast06 phase 3 trial presented as a late-breaking oral session at the 2024 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) (#ASCO24) Annual Meeting.
"If approved, ENHERTU could once again change the treatment paradigm for certain patients with breast cancer, pushing past old boundaries and broadening the number of people who may be eligible for a HER2 directed therapy," said Ken Takeshita, MD, Global Head, R&D, Daiichi Sankyo. "The designation also showcases Daiichi Sankyo’s commitment to pioneering cutting-edge science to deliver medicines like ENHERTU that create new standards of care for patients with cancer."
ENHERTU has received eight BTDs, including four in metastatic breast cancer. In addition to the new BTD, the three previous BTDs for breast cancer were for later-line HER2 low metastatic breast cancer, second-line HER2 positive metastatic breast cancer and later-line HER2 positive metastatic breast cancer. ENHERTU also received four additional BTDs, including for HER2 positive (IHC 3+) metastatic solid tumors, HER2 positive metastatic colorectal cancer, HER2 (ERBB2) mutant metastatic non-small cell lung cancer (NSCLC) and HER2 positive metastatic gastric cancer. The new BTD for ENHERTU also represents the eleventh BTD across Daiichi Sankyo’s oncology pipeline.
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 [IHC >0 <1+]) 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.
The primary endpoint of DESTINY-Breast06 is progression-free survival (PFS) in the HR positive, HER2 low patient population as measured by blinded independent central review (BICR). Key secondary endpoints include PFS by BICR in the overall trial population (HER2 low and HER2 ultralow), overall survival (OS) in patients in the HER2 low patient population and OS in the overall trial population. Other secondary endpoints include objective response rate, duration of response, 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) at multiple sites 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 3 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 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% percent 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 It is estimated that approximately 60% to 65% of HR positive, HER2 negative breast cancers are HER2 low and potentially an additional 25% may be HER2 ultralow.7,8 Endocrine therapies are widely given consecutively in the early lines of treatment for HR positive metastatic breast cancer. However, following two lines of endocrine therapy, further efficacy with additional endocrine treatment is often limited.
The current standard of care following endocrine therapy is chemotherapy, which is associated with poor response rates and outcomes.9,10,11,12 Prior to the approval of ENHERTU following chemotherapy in HER2 low metastatic breast cancer based on the DESTINY-Breast04 trial, there were no targeted therapies approved specifically for patients with HER2 low expression.13 There are no targeted therapies specifically approved for patients with HER2 ultralow expression.14 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 65 countries worldwide for the treatment of adult patients with unresectable or metastatic HER2 positive (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 65 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 4 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 more than 35 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 trial. Continued approval in 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 45 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. Full approval in China for this indication will depend on whether a randomized controlled confirmatory clinical trial can demonstrate clinical benefit in this population.
ENHERTU (5.4 mg/kg) is approved in 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