AZ and Daiichi Sankyo's breast cancer drug delays progression in advanced disease

AstraZeneca had to ask shareholders for $3.5 billion in extra cash to finance an R&D tie-up with Daiichi Sankyo for an experimental breast cancer drug – and so far it looks like money well spent.

The latest study results from trastuzumab deruxtecan, also known as DS-8201, showed that women who had not responded to around six prior treatment courses saw no further progression for a median of 16.4 months.

According to AstraZeneca’s head of oncology R&D, Jose Baselga, this patient group would normally encounter further cancer deterioration after about six months.

Results are from the phase 2 single arm DESTINY-Breast01 trial of the HER-2 targeting antibody-drug conjugate, in patients with HER2-positive metastatic breast cancer who received two or more previous HER-targeted regimens.

Other results showed a primary endpoint of objective response rate (ORR), confirmed by independent central review, was 60.9% with trastuzumab deruxtecan monotherapy.

The results that will be presented at the 2019 San Antonio Breast Cancer Symposium also showed an estimated overall survival after 12 months of 86%.

The group of patients had a median of six prior therapies for metastatic disease, including Roche’s cancer drugs Herceptin (trastuzumab), Kadcyla (trastuzumab emtansine) and Perjeta (pertuzumab).

In all the collaboration has committed the UK pharma to paying up to $6.9 billion to Daiichi Sankyo, and the FDA has agreed a faster Priority Review for trastuzumab deruxtecan.

There is one potential speed bump, however – Seattle Genetics and Japan’s Daiichi are in a dispute over intellectual property rights to the drug.

The US pharma had worked with Daiichi on development of antibody-drug conjugates before the deal with AZ and claims that the Japanese firm has borrowed its ideas to develop trastuzumab deruxtecan.

Daiichi had tried to take Seattle Genetics to court to settle the dispute, but the latter has asked a court to dismiss the case and for it to be resolved using an arbitration process.

A spokesperson for Seattle said: “We asked the court to dismiss Daiichi Sankyo’s lawsuit because it is improper.

“Daiichi Sankyo cannot proceed with its complaint against Seattle Genetics except in arbitration, as required in the parties’ 2008 collaboration agreement.

“We look forward to establishing in the correct forum that Seattle Genetics is entitled under the parties’ collaboration agreement to the intellectual property rights at issue.”