AstraZeneca and Daiichi Sankyo’s Remarkable Progress in Breast Cancer Immunotherapies

October is breast cancer awareness month, a time to support and make a difference to those battling the world’s second most common type of cancer. As well as raising awareness of this devastating disease and learning the tell-tale signs, it’s also a time to celebrate progress that is being made in the development of new treatments.  

Two companies making exciting progress are AstraZeneca and Daiichi Sankyo, who entered into a global collaboration in 2020 to develop an innovative antibody drug conjugate (ADC) pipeline. In the past five years the companies have brought two groundbreaking drugs to market, Enhertu and Datroway, both of which have been approved for various different subtypes of breast cancer.  

Below we’ll explore these two immunotherapies and how they are providing additional treatment options to patients who are so desperately in need of more choices.  

AstraZeneca and Daichii Sankyo 

In 2020, AstraZeneca partnered with Daichii Sankyo to jointly develop and commercialize a promising class of cancer treatments called antibody drug conjugates (ADCs).  

These are a class of immunotherapies that involve adjoining a toxic payload of chemotherapy to a monoclonal antibody via a linker molecule. The ADC is designed to reach specific cancer cells and directly release the payload, so that healthy cells remain unharmed.  

So far, the big pharma organization has paid Daiichi a huge sum nearing $2.4 billion! Both the Enhertu and Datroway deals involved $1billion upfront payments – and a recent milestone hit this June saw another $45 million payment making its way to the Japanese pharmaceutical company.  

Even before their partnership began, the companies have been committed to developing innovative medicines and transforming outcomes for every person living with breast cancer – no matter their disease stage, subtype, who they are or where they come from.  

But now, with their forces combined, they are more likely to (one day) eliminate cancer as a cause of death.   

Enhertu  

Enhertu (trastuzumab deruxtecan) was discovered by Daiichi Sankyo and first approved in December 2019 for unresectable or metastatic HER2-positive breast cancer. 

Roughly one in five women with breast cancer have the HER2-positive subtype – and for those with previously treated metastatic disease, progression can be alarmingly fast. 

When patients are in urgent need of stopping or slowing tumor growth, Enhertu can make a remarkable difference. In fact, compared to Kadcyla – a HER2-positive breast cancer treatment that’s been around for over a decade – Enhertu more than doubled the 12-month progression-free survival rate. 

Since partnering with AstraZeneca to further develop and commercialize the drug, Enhertu received another major approval at the start of 2025. It can now also be used to treat HER2-low and even HER2-ultralow breast cancer.