Scientific excellence and innovative training network in one
Bastienne Wentzel

Targeted anti-cancer therapies are the future of cancer treatment. Immunotherapy is booming, and antibody-drug conjugates (ADC) are a fast growing class of therapeutics. These consist of a cytotoxic drug connected to an antibody that targets a tumor marker. Although much research is aimed at elements of ADCs such as the drug payload or constructing nanobodies, the international research program TACT is bringing all aspects of this research together, from fundamental chemistry to the initial stages of biological assessment. ICI-partner WUR is involved.
The EU-project TACT combines state-of-the-art research in antibody-drug conjugates with extensive training of new researchers. (Image: TACT)

"It's one of the best collaborative programs I have been involved in," says Christopher Scott.
A professor of Pharmaceutical Biosciences at the Queen's University Belfast (QUB, Northern Ireland, UK). Scott, like ICI-researcher Bauke Albada at WUR, leads one of the research groups collaborating in the EU-project TACT: Targeted Anti-Cancer Therapies.
A Horizon 2020 program involving nine research institutes and three pharmaceutical companies, the scientific goal of TACT is to "push the boundaries of antibody-drug conjugates" as Scott puts it. "This is a rapidly expanding area of cancer therapeutics. We do cutting edge research that companies would find too risky. We demonstrate that these technologies are worth investing in. Ultimately it will bring new cancer therapeutics."

Expanding the academic circle
TACT relies heavily on the collaboration between the twelve organisations. Each academic institute hosts one or two PhD students, eleven in total. All projects have one or more assigned secondment partners where the PhD student will spend several months doing research outside their own lab.
Within TACT, Scott focuses on targeting systems; the development and bioassessment of nanobodies (nanoparticles functionalised with antibodies) to target pancreatic cancer cells, specialising in immunology. Albada on the other hand, is specialised in the fundamental chemical principles that can be used to couple small synthetic molecules to biomolecules. In a close collaboration exemplary for TACT, Irene Shajan working as a PhD in the group of Bauke Albada at WUR spent a few months in the group of Scott in Belfast. Shajan prepared bispecific antibodies (see box) and brought them to QUB for testing in bioassays. During the exchange, Shajan had the chance to learn about cell biology and toxicity and the QUB students in turn learned about what is possible with the molecules she makes.
"The results were better than we expected," says Scott. "The constructs that Bauke makes are exceptionally potent. This could cause toxicity issues, but we didn't see any of that. Also, with this kind of chemical biology you can relatively easily modulate the activity. It really surprised me how good they are."
Albada adds: "It has been great to be able to test the constructs we make ourselves. We don't have access to these methods nor the biological samples that are needed. By collaborating with Scott we gain an insight in the way the molecules we make work. That helps us for example to design even better constructs and propose new research."

Better prepared
As important as the scientific part of TACT are the various training elements for students. The program is funded within the Marie Skłodowska-Curie Innovative Training Networks. It is a 'collaborative European Training Network' (ETN) and therefore provides funding for extensive training for the early stage researchers, the PhDs. This training program resembles the ICI PhD training program and includes seven large themed meetings on entrepreneurship, careers and legal affairs as well as scientific topics. In addition, the institutions organise trainings on topics such as development or IP.
Scott feels this helps the students a lot: "The students within TACT have opportunities that others have not. There is funding to send them abroad on courses and meetings everywhere. They have daily contact outside their group and form close bonds. They help each other out and learn to collaborate. As a result, their scientific work is faster and better."
With still a year to go, the program has been a success in all respects, Scott says: "The collaborations within TACT brought me to places I'd never been to and introduced me to people I would never have met because they were outside my academic circle. We are working towards a common goal and this creates a level of trust as well. We are working as a team."

The Albada lab
TACT's scientific focus is on developing antibody-drug conjugates (ADCs) for new therapeutical principles specifically aimed at the tumor. Bauke Albada at ICI-partner WUR takes this concept various steps further in his part of the TACT program. He explains: "An ADC is a drug bound to an antibody which delivers the drug locally to the tumor cell by recognising and binding to it. A bispecific antibody is a similar construct, but it also contains a protein which binds to a T-cell from the immune system. In this way, it brings together the tumor cell and the T-cell and helps the immune system to clean up the cancer cells."
Albada's group is specialised in so-called click-chemistry. They used this method to synthesise the bispecific antibodies. "The magic word here is bio-orthogonal," says Albada. "That means we designed a chemical reaction that does not attack the rest of the biological molecule. For example a reaction between a small molecule like a drug and the antibody." This way they can covalently bind different functional parts to the antibody.
Many different click-reactions are known, but Albada and his colleagues designed and patented a biogenic click reaction that utilises a conserved tyrosine residue on the antibody. "The reaction between the small molecule and the tyrosine residue is much quicker than any other reaction on other parts of the antibody. Therefore it occurs almost exclusively. There is no time for other reactions to take place." The company Synaffix founded by ICI researcher Floris van Delft holds the license to the tyrosine click-reaction patent and offers the method for custom-made protein conjugates.
To prove the concept of this bispecific antibody, Irene Shajan, Albada's PhD student working on this project, created a bispecific antibody with trastuzumab as the part that binds to a tumor cell. Trastuzumab is used to treat breast cancer, among others. She succeeded in binding two antigen-binding regions that bind to T-cells to trastuzumab. In activity tests done at Queen's University Belfast, they proved that the antibodies bind to the targeted cells and that the T-cells are indeed activated at very low picomolar levels. Just adding the separate components did not result in any binding to cells, which shows that the click chemistry that is used to link them is required. Next, they made a construct with one T-cell binding and two tumor-binding antibodies, instead of two to two. "The activity of the T-cells is a bit more subtle in the 2:1 construct. If the activity is too high, healthy cells are destroyed as well, potentially causing unwanted side-effects," Albada explains.
Albada is very happy with the results: "The best part of this research is when we got the positive results of the biological activity studies. After a few years of learning how the chemistry works and producing enough material for tests, that is beautiful to see."

This article was published in ICI Bulletin 16, december 2023.