AZ and Daiichi to file new breast cancer drug after trial success

In March AstraZeneca asked investors for $3.5 billion to fund a collaboration with Daiichi Sankyo over a new breast cancer drug – and it looks like the project is on track.

AZ and Daiichi announced positive top-line results from the pivotal phase 2 DESTINY-Breast01 trial of trastuzumab deruxtecan, an antibody-drug conjugate, in patients with an advanced form of breast cancer.

The trial was testing the drug in patients with HER2-positive, unresectable and/or metastatic breast cancer, who had failed to respond to Roche’s Kadcyla (trastuzumab emtansine).

As its name suggests trastuzumab deruxtecan is based on the same antibody as Kadcyla – which is the one originally used in Roche’s well-established cancer drug Herceptin.

But it tags on a different cancer cell killing agent, deruxtecan, aiming to deliver a dose to cancer cells rather than healthy tissue.

The companies said  the response rate in DESTINY-Breast01, as assessed by an independent review committee, confirms in a heavily-pretreated, global patient population the “unprecedented” clinical activity in the recently-published phase 1 trial.

There were no bad surprises in terms of safety and the companies said they plan to file the drug with the FDA in the second half of 2019.

DESTINY-Breast01 is a pivotal phase 2, open-label, global, multicentre, two-part trial of trastuzumab deruxtecan.

The optimal dose of 5.4mg/kg was previously identified in part one of the trial. These latest results from part two evaluated the efficacy and safety of that dose in patients who have failed or discontinued previous treatment with trastuzumab emtansine.

The FDA has already granted Breakthrough Therapy Designation, and Fast Track Designation for trastuzumab deruxtecan, paving the way for a faster six-month review after filing.

It is also under development for several other HER2-expressing cancers, including in patients with low expression of the biomarker.

Under the agreeement signed in March AstraZeneca paid Daiichi Sankyo $1.35bn, half of which was upon execution, with the remainder payable 12 months later.

Contingent payments of up to $5.55bn include $3.8bn for potential successful achievement of future regulatory and other milestones, as well as $1.75bn for sales-related milestones.

The companies will jointly develop and market trastuzumab deruxtecan worldwide, except in Japan where Daiichi Sankyo will maintain exclusive rights. Daiichi Sankyo will be solely responsible for manufacturing and supply.

The companies plan to present detailed data at a forthcoming medical meeting.

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