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It probably won’t be long before a new treatment for metastatic breast cancer becomes available to patients. That is good news for patients. However, unfortunately, women affected with metastatic breast cancer will not be cured. But the new treatment option can prolong their lives while maintaining a tolerable quality of life. The therapy trastuzumab duocarmazine (SYD985) was developed by the pharmaceutical company Byondis in the Dutch city of Nijmegen.

International Breast Cancer Day

On October 13, worldwide attention is drawn to the importance of research into advanced and metastatic breast cancer. On that day, the Byondis building will be colored green, pink and turquoise. These are the colors that internationally symbolize metastatic breast cancer. Iconic buildings all over the world are lit up on this day.


Byondis has the Dutch premiere of being the first to complete a successful registration study with a treatment that uses an antibody drug conjugate (ADC). ADCs are revolutionizing the development of medicines. They are a kind of remote-controlled ‘missiles’ that can attack a tumor in a very targeted way. This is also referred to as precision medicine.

Once inside the cell, the DNA of the cancer cell is damaged and the cell is then destroyed,” Jan Schellens.

Attacking inside the cell

Jan Schellens, Chief Medical Officer of Byondis explains: “An ADC is made up of an antibody that has a cell-killing agent (cytotoxin) attached to it. The antibody is designed to bind to receptors that are characteristic of a tumor cell. The agent recognizes the cancer cell and which then absorbs the ADC. Once inside the cell, the cytotoxin is activated and damages the DNA of the cancer cell and then destroys the cell.”

ADC technology

The findings of the latest stages of Byondis’ research were recently presented at a major European oncology congress (the ESMO congress). ADC technology opens up the world for innovative treatments. ADCs (may) be suitable for targeting tumors in a variety of places in the body. For example, SYD985 is also being studied in patients with endometrial cancer (uterine cancer). ADCs are already used in patients, including in the treatment of lymphomas. Meanwhile, dozens of cancer drugs based on the ADC technology are under development around the world.

All hands on deck

Byondis is elated that after more than a decade of research and development, a new effective treatment may now become available for patients with HER2-positive metastatic breast cancer. At the moment all hands are on deck to gain approval from the American regulator FDA. Europe will be next. The company is also currently looking for a pharmaceutical company to help bring the medicine to the market. It is not yet clear exactly when the drug will become available to patients. “After submitting the registration dossier, it takes about ten months for the dossier to be assessed,” a Byondis spokesperson says.

Earlier stages

HER2-positive metastatic breast cancer is an aggressive form of breast cancer with a poor prognosis. On average, this form of cancer is more common in pre-menopausal women. Schellens: “We are also researching the treatment at an earlier stage, in women who have just been diagnosed with breast cancer. Here, we are looking at whether the treatment is able to shrink the tumor. Obviously, it would be great if you could treat patients much earlier in a targeted way with ADCs.”

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Jan Schellens, CMO Byondis

15,000 diagnoses

There were 15,000 breast cancer diagnoses in the Netherlands in 2019. About 3,000 people die each year in the Netherlands from breast cancer. Research into Byondis’ trastuzumab duocarmazine will continue for now, also for those patients with HER2-positive metastatic breast cancer. ” Unfortunately, patients are not cured, but the progression of their disease is slowed down,” Schellens says. ” We will continue to follow patients during this period. That way, we can also learn more about how long the drug continues to do its job.”

Also interesting: New drug for patients with metastatic breast cancer


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