AstraZeneca and Daiichi's HER2 ADC hits goal in pivotal trial

José Baselga
AstraZeneca Executive Vice President José Baselga (MSKCC)

AstraZeneca and Daiichi Sankyo’s HER2-targeting antibody drug conjugate (ADC) has hit the primary endpoint in a pivotal phase 2 trial, teeing the partners up to file for FDA approval in the first half of the fiscal year.

The readout comes shortly after AstraZeneca paid $1.35 billion upfront and committed to up to $5.5 billion in milestones for a stake in Daiichi’s anti-HER2 ADC [fam-] trastuzumab deruxtecan (DS-8201). 

Now, AstraZeneca and Daiichi have revealed that a phase 2 trial of the ADC met its primary objective response rate endpoint. The partners think the data are good enough to support a filing for approval of the fast-tracked, breakthrough-designated drug later this year but are yet to share the numbers.

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Rather, AstraZeneca and Daiichi said the results were clinically meaningful and confirm the efficacy seen in phase 1. In the earlier trial, 60% of HER2+ breast cancer patients responded to the ADC, despite most of them having previously been treated with five or more anticancer regimens such as Roche’s Herceptin and Perjeta.

Phase 2 results in line with those numbers would set AstraZeneca and Daiichi up to position the ADC as an option for HER2+ breast cancer patients who progress following treatment with Roche’s drugs. Current ASCO guidance states patients should start on a combination of Herceptin and Perjeta and move onto Roche’s Kadcyla and later Novartis’ Tykerb as they progress. 

Kadcyla secured its status as the preferred second-line treatment option on the back of a clinical trial that linked it to an overall response rate (ORR) of 44%. Novartis’ Tykerb achieved an ORR of 31% when given with Xeloda in the Kadcyla trial. The study also linked Kadcyla to improved overall survival (OS) of 31 months. It is unclear how DS-8201 compares on that front, as the phase 1 was yet to reach the median OS at the time the data were published. 

The hefty upfront AstraZeneca paid for an even split of the costs and profits from DS-8201 means it may need the results to support blockbuster sales if it is to make a major return on its investment. Whether that is likely may become clearer when the partners share data at an upcoming medical meeting and take DS-8201 through the FDA submission process. 

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