AstraZeneca and Daiichi get Q2 2020 PDUFA date for breast cancer ADC

The FDA is set to decide whether to approve AstraZeneca and Daiichi Sankyo’s HER2-targeting antibody-drug conjugate (ADC) in the second quarter of next year. AstraZeneca landed the PDUFA date for [fam-] trastuzumab deruxtecan after the FDA accepted its approval submission for priority review.

[Fam-] trastuzumab deruxtecan arrives at the FDA on the back of a phase 2 trial that hit its primary endpoint. AstraZeneca and its partner Daiichi are yet to share a detailed look at the results, stating only that they are clinically meaningful and confirm the efficacy seen in phase 1, when the ADC achieved a 60% response rate in heavily pretreated HER2+ breast cancer patients. 

The phase 1 data led AstraZeneca to pay $1.35 billion and commit to $5.5 billion in milestones for the chance to jointly develop [fam-] trastuzumab deruxtecan with Daiichi. The size of the upfront means AstraZeneca may need excellent safety and efficacy data to make the deal a financial success. 

If approved, [fam-] trastuzumab deruxtecan will initially be used some way down the HER2+ breast cancer treatment pathway. Subjects enrolled in the phase 2 had previously taken two other drugs against HER2: Roche’s aging blockbuster Herceptin and Kadcyla, the currently preferred second-line treatment option. Kadcyla, like [fam-] trastuzumab deruxtecan, is a HER2 ADC.

To justify the size of the deal, AstraZeneca will likely need to establish [fam-] trastuzumab deruxtecan higher up the treatment pathway. That could be achievable if the efficacy results seen in phase 1 are replicated and the data are free from safety red flags. 

Roche established Kadcyla as a second-line treatment by achieving a response rate of 41% but was unable to generate strong enough data to supplant Herceptin in first-line use, causing sales to fail to live up to analysts' expectations.