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AstraZeneca meets primary endpoint for Enhertu phase II trial

High-level results from the positive registrational Phase II trial DESTINY-Gastric01 showed AstraZeneca (LON:AZN) and Daiichi Sankyo Company, Limited’s Enhertu, achieved a statistically significant and clinically meaningful improvement in objective response rate and overall survival in patients with HER2-positive unresectable or metastatic gastric or gastroesophageal junction cancer that had progressed following two or more treatment regimens including trastuzumab and chemotherapy.

The trial met its primary endpoint of an improvement in ORR, as assessed by an independent review committee, in patients treated with Enhertu compared to investigator’s choice of chemotherapy (irinotecan or paclitaxel monotherapy). Enhertu also showed a statistically significant and clinically meaningful improvement in OS, a key secondary endpoint.

José Baselga, Executive Vice President, Oncology R&D, said: “Gastric cancer is usually diagnosed in the advanced stage and patients face markedly high mortality rates, making the need for new therapies especially urgent. Given the previous results seen in our HER2-positive development programme and now in HER2-positive metastatic gastric cancer, we believe this antibody drug conjugate has the potential to redefine the treatment of patients with HER2-expressing cancers.”

Gilles Gallant, Senior Vice President, Global Head, Oncology Development, Oncology R&D, Daiichi Sankyo, said: “We are excited to report positive top-line results from this trial. Our development plan remains on track in gastric cancer, including an initial regulatory application in Japan where gastric cancer is highly prevalent, and where SAKIGAKE designation has been granted for this indication. We are strongly committed to bringing this therapy as rapidly as possible to patients in need.”

The overall safety and tolerability profile of Enhertu in DESTINY-Gastric01 was consistent with that seen in the published Phase I trial in which the most common adverse events (≥30 percent, any grade) were haematologic and gastrointestinal including neutrophil count decrease, anaemia, nausea and decreased appetite. There were cases of treatment-related interstitial lung disease (ILD) and pneumonitis, the majority of which were Grade 1 and 2 with two Grade 3 and one Grade 4. No ILD-related deaths (Grade 5) occurred in gastric patients in the Phase I trial or in the DESTINY-Gastric01 trial.

These results confirm activity seen in the non-randomised Phase I trial of Enhertu in patients with HER2-positive advanced gastric cancer published in The Lancet Oncology.1 Data from DESTINY-Gastric01 will be presented at a forthcoming medical meeting.

In addition to the planned discussion with the Japan Ministry of Health, Labour and Welfare (MHLW), both companies plan to discuss the data with other health authorities. Enhertu recently received Accelerated Approval in the US for HER2-positive unresectable or metastatic breast cancer following two or more prior anti-HER2 based treatment regimens and additional global regulatory submissions in HER2-positive metastatic breast cancer are underway.

Enhertu is being jointly developed and commercialised worldwide with AstraZeneca except in Japan where Daiichi Sankyo maintains exclusive rights.

HER2

HER2 is a tyrosine kinase receptor growth-promoting protein expressed on the surface of many types of tumours including gastric, breast and lung cancers. HER2 overexpression is often associated with aggressive disease and poorer prognosis.2 When a patient is diagnosed with gastric cancer, guidelines recommend evaluating HER2-expression levels by an immunohistochemistry (IHC) test.3 A finding of IHC 3+ is considered positive. A result of IHC 2+ is considered equivocal, in which case an additional testing method of in situ hybridisation (ISH) is recommended to confirm HER2 status.

Gastric cancer

Gastric (stomach) cancer is the fifth most common cancer worldwide and the third leading cause of cancer mortality; there were approximately one million new cases reported in 2018 and 783,000 deaths.4 Incidence rates for gastric cancer are markedly higher in eastern Asia, where approximately half of all cases occur.4 South Korea and Japan have the first and third highest incidence rates of gastric cancer worldwide, respectively; in 2018, the age-standardised rate in Japan was 27.5 per 100,000 and in South Korea it was 39.6 per 100,000.5

Approximately one in five gastric cancers are HER2 positive.6 Gastric cancer is usually diagnosed in the advanced stage, but even when diagnosed in earlier stages of the disease the survival rate remains modest.7 Recommended 1st-line treatment for HER2-positive advanced or metastatic gastric cancer is combination chemotherapy plus trastuzumab, an anti-HER2 medicine, which has been shown to improve survival outcomes when added to chemotherapy.8 For gastric cancer that progresses on trastuzumab, there are no other approved HER2-targeting medicines and subsequent treatment options are limited.9

DESTINY-Gastric01

DESTINY-Gastric01 is a registrational Phase II, open-label, multi-centre trial assessing the safety and efficacy of Enhertu in 189 patients from Japan and South Korea with HER2-expressing advanced gastric cancer or gastroesophageal junction adenocarcinoma (defined as IHC3+ or IHC2+/ISH+) who have progressed on two or more prior treatment regimens including fluoropyrimidine (5-FU) and platinum chemotherapy and trastuzumab. Patients were randomised 2:1 to receive Enhertu or investigator’s choice of chemotherapy (paclitaxel or irinotecan monotherapy). Patients were treated with Enhertu 6.4mg/kg once every three weeks or chemotherapy given on the same schedule. The primary endpoint of the trial is ORR. Secondary endpoints include OS, progression-free survival, duration of response, disease control rate and time to treatment failure as well as pharmacokinetic and safety endpoints.

Enhertu

Enhertu (fam-trastuzumab deruxtecan-nxki in the US only; trastuzumab deruxtecan outside the US) is a HER2-directed antibody drug conjugate (ADC) and is the lead product in the ADC Franchise of the Daiichi Sankyo Cancer Enterprise and the most advanced programme in AstraZeneca’s ADC scientific platform. ADCs are targeted cancer medicines that deliver cytotoxic chemotherapy (“payload”) to cancer cells via a linker attached to a monoclonal antibody that binds to a specific target expressed on cancer cells.

Enhertu clinical development

A comprehensive development programme is underway globally with five registrational trials in HER2-expressing metastatic breast and gastric cancers including a trial in patients with metastatic breast cancer and low levels of HER2 expression. Phase II trials are underway for HER2-expressing advanced colorectal cancer, as well as metastatic non-squamous HER2-overexpressing or HER2-mutated non-small cell lung cancer. Trials in combination with other anticancer treatments, such as immunotherapy, are also underway.

Collaboration between AstraZeneca and Daiichi Sankyo

In March 2019, AstraZeneca and Daiichi Sankyo entered into a global collaboration to jointly develop and commercialise Enhertu worldwide, except in Japan where Daiichi Sankyo maintains exclusive rights. Daiichi Sankyo is solely responsible for manufacturing and supply.

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