On April 10, ScienceDaily published a short story on ‘Enoblituzumab’. A molecule that might be effective against cancer throughout the whole body. An interesting story involving several technologies that allowed scientists to announce the birth of a functional new anti-cancer molecule. It is nice to have a closer look at therapeutic antibodies.
First: that unpronounceable name...
Antibodies in therapy tend to have names that are, to say the least, a bit mysterious. Where do these names come from? If we are applying antibodies, we are using modified proteins that our immune system also makes. These molecules in our immune system form part of our specific defence system against all sorts of invaders (bacteria for instance). Over the last forty years, scientists have realized the potential of these molecules to be used in diagnostics and therapy. We literally can target them to any molecule that we want. Nowadays there are many on the market that are used in cancer or in the treatment of other diseases. A few examples of antibodies out there: Aducanumab, Certolizumab, Enfortumab, Caplacizumab. Common denominator is the end of the name: ‘mab’. If you are not familiar with antibodies: mab means monoclonal antibody, which means that we are not talking about a mixture of antibodies aiming at the same target. That would be a ‘polyclonal’ antibody. A monoclonal molecule is a unique molecule derived from a single ‘clone’ (or origin). For the rest of the name there is a system in place describing the letters that have been used. A nomenclature for antibodies. A few interesting items: li stands for immune system, tu for tumor, ci for cardiovascular, nu for neural and u for human. If the antibody was made in a mouse, then it had to be ‘humanized’ technologically before use in humans. Zu stands for that process. Now we understand better the name enoblituzumab: a monoclonal antibody acting on the immune system, used against tumours and humanized. The first part, enob, is not that clear. Upon asking the company that humanized the antibody, MacroGenics (Rockville, Maryland), they said this part is at the company’s request. It might very well refer to names of investigators, departments or activity of the antibody (maybe ‘enhancer of binding’?). So, for the first part there are no strict rules. Along the same lines, we can also make sense of Caplacizumab (a humanized monoclonal antibody used in a particular cardiovascular condition), Certolizumab (a humanized monoclonal antibody acting on the immune system) and Aducanumab (an antibody used in a neural disease, in this case Alzheimer’s disease). Well, if you want to know more about the working mechanism or therapeutic effects, you will have to search the web and literature because that part is not covered by the name.
The technologies behind the development of antibodies are very interesting and Nobel prizes have been awarded to the investigators that worked on them. In 1975, César Milstein and Georges Köhler published their method to produce antibodies in large amounts. They made a ‘hybrid’ cell that was the result of a fast and infinitely growing tumour cell and an antibody producing spleen cell (a so-called B-cell). The method, hybridoma technology, was revolutionary and marked the beginning of producing large amounts of antibodies for diagnostic and therapeutic purposes. Today, a lot of these antibodies are in use by investigators or applied in therapies. Another great technology to produce new antibodies makes use of bacteriophage (these are ‘viruses’ that are parasitic to bacteria): by technologically altering the phage, investigators can select very specific antibodies in a rapid way from a complete ‘library’ of phage. The fact that they are parasitic to bacteria is a great advantage, since bacteria replicate very fast and therefore produce interesting phage readily. These libraries consist of up to 1012 phage all carrying a different antibody on their surface ready to be selected to any molecule of interest. It would go too far to describe the exact procedures here, but the technique is very powerful and allows for selection of antibodies to basically any target of interest. To the people that developed the technology the Nobel prize in Chemistry was awarded in 2018 (George Smith and Greg Winter). And, talking about antibodies: the most interesting ones these days do not come from our own system, but from sharks, camels and llamas! Read more on this very interesting topic in the text by Hayley Bennett (May 2022).
Let us go back to Enoblituzumab.
Now that we know about technology: this antibody has been made in a classical way, that is, by classic hybridoma technology (Raven Technologies), though on a more sophisticated platform. So, it was produced by cells that can grow infinitely. The next step was to humanize it. This was done by MacroGenics (that acquired Raven Technologies in 2008), using their ‘Fc platform’ technology. What does that mean? The Fc part is the constant part of the molecule. This part is not involved in recognizing a target (a bacterium or a tumour cell). It is there to stabilize the molecule and, more importantly, to interact with other molecules or cells of the immune system. The Fc part differs in mice from the Fc in our system. A mouse antibody in a human body can raise an undesired immune response. Therefore, investigators optimize the Fc region to make it look like the Fc of our own antibodies. A smart way to fool the immune system! The antibody recognizes a B7-H3 protein that is on the outside of tumour cells. When it binds, an immune response is raised against the tumour cell and the result is the killing of that cell. It has now been established that B7-H3 (found in 2020), is also present in other cancers like brain tumours. Thus, the expectations are high for this antibody.
At this moment, the antibody has been tested in groups of patients with prostate cancer. This is a so-called phase 2 clinical trial. Phase 1 is performed with healthy volunteers, phase 2 includes up to a few hundreds of patients having the disease and phase 3 includes large groups of patients. The people that investigated the efficacy of this drug did a ‘single arm’ trial. No problem with arms here: it means that all patients treated received the same substance. So, there were no drug 1/drug 2 groups to compare effects: only the effect of this molecule was tested.
This is only one of many examples of development of therapeutic molecules in biomedical and biopharmaceutical research. But it is representative of the path that many new molecular medicines follow before entering the market. And it can be a very long way from the initial biochemical design to the ultimate pill described by the physician or infusion used in the hospital. A tough road that may take decades of research and brainpower.
Ivo Horn (Picamed, April 2023)
Hayley Bennett, 2022
Barderas, R and Benito-Peña, E, 2019, Analytical and Bioanalytical Chemistry. The 2018 Nobel prize in chemistry: phage display of peptides and antibodies.
Shenderov, E and colleagues, 2023, Nature Medicine. Adjuvant enoblituzumab in localized prostate cancer: a single-arm, phase 2 trial.
Loo, DT and Mather, J, 2008. Current opinion in Pharmacology. Antibody-based identification of cell surface antigens: targets for cancer therapy.