Daiichi Sankyo Company, Limited (hereafter, Daiichi Sankyo) and AstraZeneca announced positive topline results from the pivotal phase 2 DESTINY-Gastric01 trial of DS-8201, a HER2 directed antibody drug conjugate (ADC), 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, achieving a statistically significant and clinically meaningful improvement in objective response rate (ORR), as assessed by an independent review committee, in patients treated with DS-8201 versus investigator's choice of chemotherapy (irinotecan or paclitaxel monotherapy). DS-8201 also showed a statistically significant and clinically meaningful improvement in overall survival (OS), a key secondary endpoint.

The safety profile observed for DS-8201 in DESTINY-Gastric01 was consistent with previous clinical trials. These results confirm activity seen in the non-randomized phase 1 study of DS-8201 in patients with HER2 positive advanced gastric cancer published in The Lancet Oncology.1 Data from DESTINY-Gastric01 will be presented at an upcoming medical meeting. Daiichi Sankyo will initiate discussions with the Japan Ministry of Health, Labour and Welfare (MHLW) to determine next steps for a regulatory submission based on the results of DESTINY-Gastric01.

Both companies also plan to discuss the data with other health authorities. DS-8201 is being jointly developed and commercialized worldwide with AstraZeneca except in Japan where Daiichi Sankyo maintains exclusive rights. The overall safety and tolerability profile of DS-8201 in DESTINY-Gastric01 was consistent with that seen in the published phase 1 trial in which the most common adverse events (=30%, any grade) were hematologic and gastrointestinal including neutrophil count decrease, anemia, nausea and decreased appetite There were cases of drug-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 1 trial or in the DESTINY-Gastric01 trial.