ENHERTU® Reduced the Risk of Death by 30% Versus Ramucirumab Plus Paclitaxel as a Second-Line Therapy in Patients with HER2 Positive Unresectable or Metastatic Gastric Cancer in DESTINY-Gastric04 Phase 3 Trial

• Daiichi Sankyo and AstraZeneca’s ENHERTU demonstrated a median overall survival of 14.7 months
• Results reinforce second-line use of ENHERTU globally in this setting

TOKYO & BASKING RIDGE, N.J.--(BUSINESS WIRE)--Positive results from the DESTINY-Gastric04 phase 3 trial showed ENHERTU^® (trastuzumab deruxtecan) demonstrated a statistically significant and clinically meaningful improvement in overall survival (OS) compared to ramucirumab plus paclitaxel in patients with second-line HER2 positive (IHC 3+ or IHC 2+/ISH+) unresectable and/or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma. Results will be presented today as a late-breaking oral presentation (LBA #4002) at the 2025 American Society of Clinical Oncology (#ASCO25) Annual Meeting and simultaneously published in The New England Journal of Medicine.

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).

In the primary endpoint analysis of OS, ENHERTU reduced the risk of death by 30% versus ramucirumab plus paclitaxel (hazard ratio [HR]: 0.70; confidence interval [CI]: 0.55-0.90; p=0.0044). Median OS was 14.7 months with ENHERTU (n=246) versus 11.4 months with ramucirumab plus paclitaxel (n=248).

In the secondary endpoint analysis of progression-free survival (PFS), ENHERTU demonstrated a 26% reduction in the risk of disease progression or death versus ramucirumab plus paclitaxel (HR: 0.74; 95% CI: 0.59-0.92; p=0.0074) as assessed by investigator. Median PFS was 6.7 months with ENHERTU versus 5.6 months with ramucirumab plus paclitaxel. A confirmed objective response rate (ORR) of 44.3% (95% CI: 37.8-50.9) was seen in patients treated with ENHERTU with seven complete responses (CR) and 97 partial responses (PR) versus an ORR of 29.1% (95% CI: 23.4-35.3) with three CRs and 66 PRs in the ramucirumab plus paclitaxel arm (p=0.0006). Median duration of response (DOR) was 7.4 months (95% CI: 5.7-10.1) in the ENHERTU arm and 5.3 months (95% CI: 4.1-5.7) in the ramucirumab plus paclitaxel arm. Disease control rate (DCR) was 91.9% (95% CI: 87.7-95.1) with ENHERTU versus 75.9% (95% CI: 70.0-81.2) with ramucirumab plus paclitaxel. Improvements in OS and PFS with ENHERTU were consistent across subgroups.

“Gastric cancer is particularly challenging to treat, especially in the advanced stages where the five-year survival rate remains low,” said Kohei Shitara, MD, Chief, Department of Gastrointestinal Oncology, National Cancer Center Hospital East, Chiba, Japan and lead investigator in the DESTINY-Gastric04 trial. “The superior overall survival demonstrated in DESTINY-Gastric04 confirms that ENHERTU could become the global standard of care in the second-line metastatic setting of HER2 positive gastric cancer or gastroesophageal junction cancer.”

The safety profile of ENHERTU in DESTINY-Gastric04 was consistent with previous gastric cancer clinical trials with no new safety concerns identified. The most common grade 3 or higher treatment related adverse events occurring in patients treated with ENHERTU were neutropenia (28.7%), anemia (13.9%), thrombocytopenia (8.6%), leukopenia (7.4%) and fatigue (7.0%). Interstitial lung disease (ILD) or pneumonitis occurred in 13.9% of patients treated with ENHERTU and 1.3% treated in the ramucirumab plus paclitaxel arm. In the ENHERTU arm, the majority of ILD or pneumonitis events were low grade (grade 1 [n=7; 2.9%] or grade 2 [n=26; 10.7%]) except for one grade 3 ILD event (0.4%) as determined by an independent adjudication committee. In the ramucirumab plus paclitaxel arm, there were two grade 3 (0.9%) and one grade 5 (0.4%) ILD events.

“ENHERTU continues to deliver impressive results with these new data from DESTINY-Gastric04, which represent the first time a HER2 directed medicine has demonstrated a survival benefit in a randomized phase 3 trial in the second-line HER2 positive metastatic gastric cancer setting,” said Ken Takeshita, MD, Global Head, R&D, Daiichi Sankyo. “Similar to our strategy in other tumor types, we continue to pursue the development of ENHERTU in earlier stages of gastric cancer and have recently initiated phase 3 trials evaluating ENHERTU as part of a combination regimen as a first-line treatment in patients HER2 positive metastatic disease.”

“Patients with HER2 positive metastatic gastric cancer who experience progression after first-line treatment have historically faced poor outcomes,” said Cristian Massacesi, MD, Chief Medical Officer and Oncology Chief Development Officer, AstraZeneca. “These results showed that ENHERTU reduced the risk of death by nearly one-third in patients with previously treated HER2 positive metastatic gastric cancer, reinforcing the benefit of ENHERTU in this setting.”

ENHERTU is currently approved in more than 70 countries in the second-line or third-line metastatic setting of HER2 positive gastric cancer based on DESTINY-Gastric01, a randomized phase 2 trial, and DESTINY-Gastric02 and DESTINY-Gastric06, two single-arm phase 2 trials.

Daiichi Sankyo and AstraZeneca are currently evaluating ENHERTU in the first-line metastatic setting through the DESTINY-Gastric05 and ARETEMIDE-Gastric01 phase 3 trials.

The majority of patients in the DESTINY-Gastric04 trial had received no prior treatment with an immune checkpoint inhibitor (84.1% in the ENHERTU arm and 84.7% in the ramucirumab plus paclitaxel arm) and had two or more metastatic sites (70.3% in the ENHERTU arm and 69.8% in the ramucirumab plus paclitaxel arm). Median duration of follow-up was 16.8 months in the ENHERTU arm and 14.4 months in the ramucirumab plus paclitaxel arm. Median treatment duration was 5.4 months (range: 0.7-30.3) with ENHERTU and 4.6 months (range: 0.9-34.9) with ramucirumab plus paclitaxel. Of the patients that discontinued treatment from the ramucirumab plus paclitaxel arm, 52 (21.0%) proceeded to receive ENHERTU and 12 (4.8%) disitamab vedotin post-trial. As of the data cut-off of October 24, 2024, 18.9% of patients receiving ENHERTU and 18.5% receiving ramucirumab plus paclitaxel remained on study treatment.

Summary of DESTINY-Gastric04 Primary Analysis Results

About DESTINY-Gastric04
DESTINY-Gastric04 is a global, randomized, open-label, phase 3 trial evaluating the efficacy and safety of ENHERTU (6.4 mg/kg) versus ramucirumab and paclitaxel in patients with HER2 positive (IHC 3+ or IHC 2+/ISH+) unresectable and/or metastatic gastric or GEJ adenocarcinoma with disease progression on or after a trastuzumab-containing regimen.

The primary endpoint is OS. Secondary endpoints include investigator-assessed progression-free survival, objective response rate, duration of response, disease control rate and safety.

In March 2025, an Independent Data Monitoring Committee recommended unblinding DESTINY-Gastric04 based on the superior efficacy of ENHERTU seen at a planned interim analysis.

DESTINY-Gastric04 enrolled 494 patients in Asia, Europe and South America. For more information about the trial, visit ClinicalTrials.gov.

About HER2 Positive Gastric Cancer
Gastric (stomach) cancer is the fifth most common cancer worldwide and the fifth leading cause of cancer-related death.¹ Approximately one million cases of gastric cancer were diagnosed in 2022.¹ Gastric cancer is associated with a poor prognosis, particularly in advanced stages of the disease where the five-year survival rate is 5% to 10%.²

HER2 is a tyrosine kinase receptor growth-promoting protein expressed on the surface of many types of tumors, including gastric cancer.³ Approximately one in five gastric cancers are considered HER2 positive.^3,4

Prior to the results of the DESTINY-Gastric04 trial of ENHERTU, no other HER2 directed medicine has demonstrated a survival benefit in the second-line metastatic setting in a randomized clinical trial.⁵

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 80 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 80 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 more than 30 countries 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 a locally or regionally 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 60 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 70 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, Saudi Arabia, Taiwan, U.K. 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 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 as a monotherapy or in combination or sequentially with other anti-cancer therapies across multiple HER2 targetable cancers.

About the Daiichi Sankyo and AstraZeneca Collaboration
Daiichi Sankyo and AstraZeneca entered into a global collaboration to jointly develop and commercialize ENHERTU in March 2019 and DATROWAY^® in July 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.

ENHERTU U.S. Important Safety Information

Indications
ENHERTU is a HER2-directed antibody and topoisomerase inhibitor conjugate indicated for the treatment of adult patients with:

• Unresectable or metastatic HER2-positive (IHC 3+ or ISH positive) 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

• 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
  • HER2-low (IHC 1+ or IHC 2+/ISH-) breast cancer, as determined by an FDA-approved test, who have received a prior chemotherapy in the metastatic setting or developed disease recurrence during or within 6 months of completing adjuvant chemotherapy

• Unresectable or metastatic non-small cell lung cancer (NSCLC) whose tumors have activating HER2 (ERBB2) mutations, as detected by an FDA-approved test, and who have received a prior systemic therapy
  
  This indication is approved under accelerated approval based on objective response rate and duration of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

• Locally advanced or metastatic HER2-positive (IHC 3+ or IHC 2+/ISH positive) gastric or gastroesophageal junction (GEJ) adenocarcinoma who have received a prior trastuzumab-based regimen

• Unresectable or metastatic HER2-positive (IHC 3+) solid tumors who have received prior systemic treatment and have no satisfactory alternative treatment options
  
  This indication is approved under accelerated approval based on objective response rate and duration of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

Contraindications
None.

Warnings and Precautions
Interstitial Lung Disease / Pneumonitis
Severe, life-threatening, or fatal interstitial lung disease (ILD), including pneumonitis, can occur in patients treated with ENHERTU. A higher incidence of Grade 1 and 2 ILD/pneumonitis has been observed in patients with moderate renal impairment. Advise patients to immediately report cough, dyspnea, fever, and/or any new or worsening respiratory symptoms. Monitor patients for signs and symptoms of ILD. Promptly investigate evidence of ILD. Evaluate patients with suspected ILD by radiographic imaging. Consider consultation with a pulmonologist. For asymptomatic ILD/pneumonitis (Grade 1), interrupt ENHERTU until resolved to Grade 0, then if resolved in ≤28 days from date of onset, maintain dose. If resolved in >28 days from date of onset, reduce dose 1 level. Consider corticosteroid treatment as soon as ILD/pneumonitis is suspected (e.g., ≥0.5 mg/kg/day prednisolone or equivalent). For symptomatic ILD/pneumonitis (Grade 2 or greater), permanently discontinue ENHERTU. Promptly initiate systemic corticosteroid treatment as soon as ILD/pneumonitis is suspected (e.g., ≥1 mg/kg/day prednisolone or equivalent) and continue for at least 14 days followed by gradual taper for at least 4 weeks.

HER2-Positive, HER2-Low, and HER2-Ultralow Metastatic Breast Cancer, HER2-Mutant NSCLC, and Solid Tumors (Including IHC 3+) (5.4 mg/kg)
In patients with metastatic breast cancer, HER2-mutant NSCLC, and other solid tumors treated with ENHERTU 5.4 mg/kg, ILD occurred in 12% of patients. Median time to first onset was 5.5 months (range: 0.9 to 31.5). Fatal outcomes due to ILD and/or pneumonitis occurred in 0.9% of patients treated with ENHERTU.

HER2-Positive Locally Advanced or Metastatic Gastric Cancer (6.4 mg/kg)
In patients with locally advanced or metastatic HER2-positive gastric or GEJ adenocarcinoma treated with ENHERTU 6.4 mg/kg, ILD occurred in 10% of patients. Median time to first onset was 2.8 months (range: 1.2 to 21).

Neutropenia
Severe neutropenia, including febrile neutropenia, can occur in patients treated with ENHERTU. Monitor complete blood counts prior to initiation of ENHERTU and prior to each dose, and as clinically indicated. For Grade 3 neutropenia (Absolute Neutrophil Count [ANC] <1.0 to 0.5 x 10⁹/L), interrupt ENHERTU until resolved to Grade 2 or less, then maintain dose. For Grade 4 neutropenia (ANC <0.5 x 10⁹/L), interrupt ENHERTU until resolved to Grade 2 or less, then reduce dose by 1 level. For febrile neutropenia (ANC <1.0 x 10⁹/L and temperature >38.3º C or a sustained temperature of ≥38º C for more than 1 hour), interrupt ENHERTU until resolved, then reduce dose by 1 level.

HER2-Positive, HER2-Low, and HER2-Ultralow Metastatic Breast Cancer, HER2-Mutant NSCLC, and Solid Tumors (Including IHC 3+) (5.4 mg/kg)
In patients with metastatic breast cancer, HER2-mutant NSCLC, and other solid tumors treated with ENHERTU 5.4 mg/kg, a decrease in neutrophil count was reported in 65% of patients. Nineteen percent had Grade 3 or 4 decreased neutrophil count. Median time to first onset of decreased neutrophil count was 22 days (range: 2 to 939). Febrile neutropenia was reported in 1.2% of patients.

HER2-Positive Locally Advanced or Metastatic Gastric Cancer (6.4 mg/kg)
In patients with locally advanced or metastatic HER2-positive gastric or GEJ adenocarcinoma treated with ENHERTU 6.4 mg/kg, a decrease in neutrophil count was reported in 72% of patients. Fifty-one percent had Grade 3 or 4 decreased neutrophil count. Median time to first onset of decreased neutrophil count was 16 days (range: 4 to 187). Febrile neutropenia was reported in 4.8% of patients.

Left Ventricular Dysfunction
Patients treated with ENHERTU may be at increased risk of developing left ventricular dysfunction. Left ventricular ejection fraction (LVEF) decrease has been observed with anti-HER2 therapies, including ENHERTU. Assess LVEF prior to initiation of ENHERTU and at regular intervals during treatment as clinically indicated. Manage LVEF decrease through treatment interruption. When LVEF is >45% and absolute decrease from baseline is 10-20%, continue treatment with ENHERTU. When LVEF is 40-45% and absolute decrease from baseline is 20%, interrupt ENHERTU and repeat LVEF assessment within 3 weeks. If LVEF of 20% is confirmed, permanently discontinue ENHERTU. Permanently discontinue ENHERTU in patients with symptomatic congestive heart failure. Treatment with ENHERTU has not been studied in patients with a history of clinically significant cardiac disease or LVEF <50% prior to initiation of treatment.

HER2-Positive, HER2-Low, and HER2-Ultralow Metastatic Breast Cancer, HER2-Mutant NSCLC, and Solid Tumors (Including IHC 3+) (5.4 mg/kg)
In patients with metastatic breast cancer, HER2-mutant NSCLC, and other solid tumors treated with ENHERTU 5.4 mg/kg, LVEF decrease was reported in 4.6% of patients, of which 0.6% were Grade 3 or 4.

HER2-Positive Locally Advanced or Metastatic Gastric Cancer (6.4 mg/kg)
In patients with locally advanced or metastatic HER2-positive gastric or GEJ adenocarcinoma treated with ENHERTU 6.4 mg/kg, no clinical adverse events of heart failure were reported; however, on echocardiography, 8% were found to have asymptomatic Grade 2 decrease in LVEF.

Embryo-Fetal Toxicity
ENHERTU can cause fetal harm when administered to a pregnant woman. Advise patients of the potential risks to a fetus. Verify the pregnancy status of females of reproductive potential prior to the initiation of ENHERTU. Advise females of reproductive potential to use effective contraception during treatment and for 7 months after the last dose of ENHERTU. Advise male patients with female partners of reproductive potential to use effective contraception during treatment with ENHERTU and for 4 months after the last dose of ENHERTU.

Additional Dose Modifications
Thrombocytopenia
For Grade 3 thrombocytopenia (platelets <50 to 25 x 10⁹/L) interrupt ENHERTU until resolved to Grade 1 or less, then maintain dose. For Grade 4 thrombocytopenia (platelets <25 x 10⁹/L) interrupt ENHERTU until resolved to Grade 1 or less, then reduce dose by 1 level.

Media Contacts:

Global/US:
Jennifer Brennan
Daiichi Sankyo
jennifer.brennan@daiichisankyo.com
+1 908 900 3183 (mobile)

Japan:
Daiichi Sankyo Co., Ltd.
DS-PR_jp@daiichisankyo.com

Investor Relations Contact:
DaiichiSankyoIR_jp@daiichisankyo.com