Daiichi Sankyo takes Seattle Genetics to court as battle over breast cancer drug escalates

Big-selling drugs often spark legal bunfights as companies squabble over who did what during the development process and what share of profits they deserve – and Daiichi Sankyo and AstraZeneca’s potential breast cancer blockbuster is no exception.

The drug involved, trastuzumab deruxtecan, is essentially a souped-up version of Roche's Herceptin (trastuzumab) antibody with a cancer-killing cytotoxic payload attached to boost its efficacy.

Sales are forecast to exceed $4.5 billion annually if it is approved and Seattle Genetics thinks it should get a share after working with Daiichi Sankyo on linking technology for antibody-drug conjugates between 2008 and 2015.

The FDA has granted a fast six-month review in HER2 positive disease for trastuzumab deruxtecan, also known as DS-8201, something it reserves for drugs that are likely to significantly improve outcomes compared with existing therapies.

AstraZeneca in March signed a deal worth up to $6.9 billion with Daiichi Sankyo, including $1.35 billion up front, for the drug that CEO Pascal Soriot said could be “transformative” for patients with this form of the disease.

Seattle’s claim against Daiichi Sankyo covers all of the Japanese firm’s antibody-drug conjugate (ADC) pipeline following the alliance between 2008 and 2015.

Daiichi paid $4 billion to gain access to Seattle’s linking technology in that alliance, and Daiichi has asked the US District Court of Delaware to make a judgement on the matter after receiving a communication from Seattle claiming “certain intellectual property rights” over its ADC-based products.

According to Daiichi such a claim is “without merit” adding that it will “vigorously defend” its position.

The ADCs it is currently developing are “distinct” from those developed in the tie-up with Seattle, Daiichi said in a statement.

In a response statement, Seattle said that the linker and “other ADC technology” in the potential drugs is “automatically assigned” to it under the terms of the agreement signed in 2008.

An AstraZeneca spokesperson said: “Daiichi Sankyo has informed us that they are in an intellectual property dispute with Seattle Genetics with respect to several Daiichi Sankyo pipeline drug candidates. This dispute includes DS-8201, an antibody-drug conjugate (ADC), which we are collaborating with Daiichi Sankyo to co-develop and co-commercialise.

“AstraZeneca is not named in or a part of the litigation and we remain committed to working with Daiichi Sankyo to ensure our teams are focused on a collaborative effort to bring this innovative potential medicine to patients as quickly as possible.”