A team of scientists from the Department of Chemistry at the Jagiellonian University, led by Katarzyna Magiera-Mularz, BEng, PhD, were the first to describe the structural characteristics and biological properties of a peptide (pAC65) – which is an anti-cancer molecule. Will the discovery open up new perspectives in the immunotherapeutic treatment of cancer? What changes in the world of medicine may occur as a consequence of describing the peptide (pAC65)?
Katarzyna Magiera-Mularz, BEng, PhD – Researcher from the Department of Chemistry at the Jagiellonian University, specialising in protein biochemistry. In 2017, she was recognised and Awarded by the Biotechnology Committee of the Professor Wacław Szybalski Polish Academy of Sciences for the best original work by a young Polish researcher in the field of biotechnology. A team of scientists led by her was the first to describe the structural characterisation and biological properties of a peptide (pAC65).
Magdalena Marynowska – Editor-in-Chief of Coopernicus, student of Law and International Relations at the University of Warsaw.
Magdalena Marynowska: Where did the idea to undertake research on the BMS compound originate from?
Katarzyna Magiera-Mularz, BEng, PhD: For years, we have been interested in the research work of the most renowned pharmaceutical companies on the subject of inhibitors of PD-L1, a protein that is one of the targets of breakthrough anti-cancer therapy. The research work that initiated the development of the immunotherapy was honoured with a Nobel Prize in 2018. I was inspired to continue my research in the topic of macrocyclic peptides, i.e. short strings of amino acids linked in a ring, by my earlier work published in Angewandte Chemie. At the time I was still working in Prof Holak’s team and I described two world-first structures of peptides in complexes with the PD-L1 protein. Following the latest reports of macrocyclic peptides entering the clinical trial phase, I knew that BMS had a peptide with significantly better biological properties than those described in the first paper. This is important because this class of compounds shows advantages over standard monoclonal antibodies. Of course, in the interests of the company, clinical trials are on the one hand kept secret and on the other covered by patent protection. However, presenting this type of data to the scientific community could potentially speed up the process of inventing compounds with even better properties.
Magdalena Marynowska: What was the process of developing the aforementioned structural characteristics of the pAC65/protein complex like?
Katarzyna Magiera-Mularz, BEng, PhD: Work on structural studies of protein-inhibitor complexes always starts with two basic issues: obtaining the protein and the inhibitor. We already had an excellent method for obtaining PD-L1 protein samples, as we have been conducting research on this topic for many years. On the other hand, we obtained the sample of the inhibitor, a macrocyclic peptide, through cooperation with Prof Berlicki’s team from the Wrocław University of Technology. Having the inhibitor, initially, we performed standard tests of its ability to interact with the protein. Already thanks to the results of this initial step, we knew that, for the first time, we had such a potent inhibitor of the PD-1/PD-L1 protein complex in our hands. However, getting back to the topic of structural characterisation – the requirement for obtaining accurate information on protein-inhibitor interactions is to obtain sufficient quality crystals of such a complex. By testing hundreds of crystallisation conditions and gaining access to the best synchrotron radiation facilities in Europe, we obtained a suitable data set to characterise the interaction of pAC65 with PD-L1 at the molecular level.
Magdalena Marynowska: What kind of experimental methods were used to assess the interaction of pAC65 with PD-L1?
Katarzyna Magiera-Mularz, BEng, PhD: To study the interaction, we primarily used the technique of nuclear magnetic resonance (NMR) spectroscopy. Using a suitably prepared, labelled protein sample, we recorded its spectrum – i.e. the characteristic record of signals for that protein. Then, by titrating the protein sample with a peptide, we observed how the protein ‘reacts’ to its presence. In addition, we showed that the peptide is capable of disrupting protein interactions in the PD-1/PD-L1 complex. This is important because cancer cells use the PD-1/PD-L1 complex to avoid the immune system. However, these studies on simplified protein-inhibitor systems are not the ones that demonstrate the potential of the peptide we have described. Much more important are the results obtained on cells supervised by Łukasz Skalniak, MD, PhD – head of the team in which I currently work, and the studies conducted on cells isolated from the blood of patients, which we conducted in collaboration with Prof Siedlar’s team from Collegium Medicum UJ. The models used represent a situation which much more closely replicates conditions in the body. The results of these studies allowed us to confirm the ability of the peptide to dissociate the PD-1/PD-L1 complex in biological systems, as well as demonstrating its exceptionally high activity comparable to that observed for antibodies used in cancer immunotherapy.
Magdalena Marynowska: Immunotherapies for cancer – what are they actually about?
Katarzyna Magiera-Mularz, BEng, PhD: These therapies are based on the rather novel concept of stimulating the immune system to destroy cancer cells. Many cancers are characterised by the fact that cancer cells, by presenting relevant proteins on their surface (including PD-L1), are no longer visible to the immune system, which should eliminate them. Immune therapies, currently only possible with antibodies, restore and enhance this natural mechanism of the human body to fight cancer cells. Importantly – immunotherapies – are currently the only strategy that can cure people with cancer at a very advanced stage. In addition, they offer truly ground-breaking results that previously could not be achieved using any of the classical methods such as radio- or chemotherapies. However, it should be emphasised that cancer is not a single disease entity. Behind this term is a collection of many different disorders that have only one thing in common – the ability to grow rapidly and uncontrollably. Immunotherapy, like any other method, is therefore not a universal strategy that will help in every case, although its therapeutic potential is indeed impressive.
Magdalena Marynowska: Are there already plans for pre-clinical and subsequently clinical trials on the pAC65 peptide in the long term?
Katarzyna Magiera-Mularz, BEng, PhD: Of course, learning about the performance profile of the peptide in more advanced systems seems very interesting. However, it is important to realise that each successive stage of research is associated with increasing costs, which can be afforded by the largest pharmaceutical companies, but not by universities. We have a preliminary plan for pre-clinical research in mind, but we reckon that once this work is published, another group with already developed methods and models for further research will be quicker to follow. And that’s a good thing! It is important for science and the development of immunotherapy that the results of such studies are available as soon as possible. Clinical trials, on the other hand, are not completely within our reach, but I think that if the profile of the peptide in preclinical studies is promising then it will definitely enter the next phases of research.
Magdalena Marynowska: What changes in the world of medicine could happen as a consequence of the description of the peptide (pAC65)?
Katarzyna Magiera-Mularz, BEng, PhD: These will certainly not be rapid changes. The whole process of preclinical testing, clinical testing and possible legalisation for medical use takes years of work. Perhaps the chemical structure of the peptide will also require additional optimisation. Then the whole research cycle will start all over again. However, if this type of peptide passes all tests successfully, it is possible that it will be a breakthrough in the availability of immunotherapy for patients. One advantage of non-protein inhibitors is that they do not have to be administered intravenously. So, it may be possible to develop a therapy with similar efficacy to those based on antibodies that is available for administration at home, for example as a nasal spray. There is also a chance that the use of a peptide could overcome some of the side effects associated with the use of antibodies, which would again improve the quality of life for the cancer patient. Although the road to the introduction of such an improved therapy today seems very long, I wish for myself and for everyone else that it becomes possible as soon as it can.
The discovery of the structural characteristics and biological properties of the pAC65 peptide by a team of scientists from the Jagiellonian University may revolutionise immunotherapeutic treatment of cancer. This discovery has the potential to develop less toxic, more effective and accessible therapies that can improve patients’ quality of life. The possibility of using the pAC65 peptide in a more convenient way, such as a nasal spray, opens up new perspectives in the fight against cancer. While the road to the introduction of this therapy may be long, it is a promising step into the future of medicine and the fight against cancer.
Magdalena Marynowska, Katarzyna Magiera-Mularz, BEng, PhD
