EXECUTIVE INTERVIEW - BioCellChallenge: Optimizing the Potential of Intracellular Therapeutic Antibodies

In many human diseases, such as cancers, proteins are mutated or overexpressed, which results in aberrant physiological processes. These proteins can be cell membrane receptors, proteins involved in cell signalling or intracellular routing, proteins involved in transcription regulation, or others. Protein-protein interactions are a key component of these processes. The use of antibodies that are able to interact with specific domains of the proteins involved in these interactions is particularly important to developing future treatments against diseases. Drug Development & Delivery recently spoke with Dr. Laurent Meunier, CEO of BioCellChallenge, to discuss the development of a new liposomal formulation allowing the use of intracellular therapeutic antibodies.

Q: Why did BioCellChallenge decide to create a solution to deliver antibodies into live cells?

A: Forty years ago, Alan F. Williams showed that monoclonal antibodies could be raised against biologically interesting molecules with a very high specificity. Since then, monoclonal antibodies have become a very useful tool, not only for immunotherapies, but also as in vitro tools for diagnostic and research purposes. Antibodies are not able to pass naturally through the membranes of live cells toward potential intracellular targets. Today, all of the therapeutic antibodies used in treatment are targeting proteins located on the surface of the cell membrane, such as receptors. The market for therapeutic antibodies reached $44 billion worldwide in 2011. The concept of therapeutic antibodies has, however, led to the recent development of intrabodies. These intracellular antibodies, produced directly into the cytosol, were designed to interfere with a range of protein targets inside cells, in order to modify their functionality and fight against viral infections, cancer diseases, or other targets. However, even if a lot of progress has been made in such immunotherapies, used against intracellular targets, this approach still necessitates overcoming a number of challenges in order to envisage using it as a therapy option. An alternative approach is to directly deliver antibodies into live cells. The advantage of this is that thousands of existing monoclonal antibodies could be used and no specific engineering or selection of a specific intracellular antibody is needed. In addition, this alternative approach does not require gene therapy steps in order to express an intracellular antibody. Therefore, all the problems associated with gene therapy and the modification of our genetic material is overcome. For this reason, BioCellChallenge developed a system allowing for the intracellular delivery of antibodies.

Q: How is the drug delivery marketplace evolving, and why is it becoming more important in the fight against diseases?

A: In the past 15 years, there has been a considerable evolution in the intracellular drug delivery market. However, most of our studies were focused on gene therapy, and the delivery of nucleic acids, such as genes or siRNAs, into cells. Only a few projects that were not gene therapy related were undertaken in order to deliver non-nucleic acid molecules, including proteins, into living cells. Today, finding the way to deliver drugs efficiently, without secondary effects in the human body, is even more of a challenge than drug discovery. This is especially relevant in cancer, where very efficient molecules have been developed but have not yet been used because they couldn’t be delivered properly into the organism. If we can find the way for the drug to reach its target, there could already be efficient systems that could treat or have an effect on various pathologies. Protein transduction domains (PTDs), small membrane-permeable peptide carriers, were proposed in the mid 1990s to deliver different cargoes into the cells, including proteins and antibodies. However, their poor interaction with cargoes has necessitated chemical engineering in order to covalently link them together. Recently, several liposomal formulations have also been developed. Their main advantages are that they can interact directly with different cargoes by electrostatic and hydrophobic interactions and that chemistry preparatory steps are not needed. However, although some of these formulations are accessible on the market, their efficiency is still limited, and some new developments and optimizations have been necessary to increase their efficiency. Recently, BioCellChallenge has worked on the development of an antibody intracellular delivery reagent based on a liposomal formulation. The result is a very efficient and non-toxic antibody intracellular delivery system that is very easy to use with any antibody on the market. This system, named ImmunoCellin, functions by encapsulating the antibodies through non-covalent interactions. Because no organic chemical coupling occurs, the delivered antibodies retain their structure and function.

Q: How does ImmunoCellin function and why is it unique?

A: The antibodies are delivered into the cells in 4- to 24-hour periods, depending on cell types. They are able to find and bind their targets inside the cytosol of living cells. For example, antibodies directed against a protein of the nuclear pore complex localize to the nuclear envelope a few hours after their intracellular delivery. ImmunoCellin is very quick and simple to use. It works in the same way as a nucleic acid transfection reagent. As it is a liposomal formulation in water, adding a few microliters of the liposomes to a few micrograms of the antibody with 15 minutes of incubation will create the encapsulation of the antibodies within the liposomes. No chemical coupling is required, and both antibodies and liposomes interact together through non-covalent interactions. These complexes are then added directly into the cells. Critically, there is no inhibition due to the presence of the serum added in tissue culture media. This is particularly important for both in vivo and therapeutic approaches. Another important result we have obtained is that additives, such as BSA, which may be present in commercially available antibodies, do not interfere with ImmunoCellin and do not inhibit its activity. This allows the use of the reagent with any antibody on the market without any further purification process.

Q: What type of diseases can ImmunoCellin target? How could it contribute to the battle against these diseases?

A: Because there are antibodies against all identified proteins, ImmunoCellin can target many diseases involving the malfunction of proteins or “infectious” proteins in cells. The malfunction of proteins is responsible for a wide number of diseases, including cancers, neurodegenerative disorders (Alzheimer’s, Parkinson’s), and some infectious diseases. ImmunoCellin has been designed to block intracellular protein functions for immunotherapy purposes, but it can also be used in more “fundamental” studies. For example, siRNA intracellular delivery enables the shutting down of the expression and all the functions of the targeted protein. However, if this protein has several different functions inside cells, it is more advisable to inhibit only one function by using a specific monoclonal antibody directed against a specific domain of the protein. As it will interfere with a single cellular mechanism, a specific function of the protein can be determined with certainty. ImmunoCellin is also particularly suitable for use in kinetic studies of intracellular protein localization in response to different stimuli. It can also directly interfere with protein traffic in the cytosol or the nucleus; by targeting a localization signal, for example. ImmunoCellin is therefore a powerful tool for developing a broader understanding of the protein-protein interactions, which form the basis of cell functions.

Q: What are the future plans for BioCellChallenge?

A: This new system is aimed particularly at pharmaceutical and biotechnology industry R&D teams working on therapeutic antibodies. As a result, BioCellChallenge is keen to develop partnerships with other companies in the pharmaceutical and biotechnology industry. The ImmunoCellin system is also particularly relevant to cellular and molecular research biologists worldwide. With these future partnerships in mind, BioCellChallenge is working on some additional improvements of immunoCellin. For example, we are currently working on a specific ImmunoCellin formulation adapted for in vivo approaches. We are also working on the GMP compliance of several of our molecules.

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