“Antibody Therapeutics and Immunotargeting (ATI)” team
The recent successes of therapeutic antibodies called immune checkpoint inhibitors (ICIs) blocking the inhibitory receptors found on tumor-infiltrated immune cells have revolutionized the therapy of several cancers, to the point that immunotherapy is now considered the fourth pillar of cancer therapy together with surgery, radio and chemotherapy. Still, only a minority of treated patients benefit from those treatments, and there is an urgent need to expand the arsenal of ICIs. Beside the classically targeted T cells, natural killer (NK) cells are reportedly important actors of the anti-tumor immune response, through the killing of tumor cells, but also and most importantly through the secretion of several cytokines and chemokines that can recruit and activate cells of the innate and adaptive immune systems.
The main interest of our lab is to use antibody engineering solutions to generate innovative molecules able to efficiently modulate the anti-tumor immune response through the recruitment and activation of innate immune cells.
Our team has developed a solid expertise in the generation and use of nanobodies for cancer therapy and diagnostic using in vitro selection methods such as phage display. Nanobodies are constituted by a single Ig domain, corresponding to the variable domain of antibodies naturally devoid of light chain found in camelids. While being one tenth of the size of a conventional mAbs (15 vs. 150 kDa), they bind to their antigen with nanomolar affinities, and often with exquisite specificities. Being so small, they also represent efficient modular blocks that can be used to generate small multivalent or multispecific constructs. A small size has multiple advantages. It allows a deeper penetration into tissues and tumors, unlike large mAbs usually unable to reach the tumor cores. A second benefit is a better access to the immune synapse, this very narrow interface (15 nm, roughly the size of an IgG), where activating and inhibitory interactions between tumor cells and immune effector cells take place. Importantly for therapeutic approaches, the serum half life of small nanobody-based constructs can efficiently be extended by a simple fusion to a nanobody targeting the human serum albumin. We are exploring the possibilities offered by this technology for two main goals.
1 / A new generation of Immunomodulators
In the context of immunotherapy, our team is exploring the possibility to modulate the anti tumor activities of NK cells by two main approaches:
i) We are exploring the potential of using small bispecific antibodies for the (re) activation of immuno-surveillance mechanisms through the stimulation of innate immune cells in a target-dependent manner. Recruitment, tumor infiltration and activation of immune cells are investigated by in vitro 2D and 3D culture cell models and in vivo mice models. Synergism with clinically validated mAb or other bispecific formats is also explored to increase their therapeutic potential.
ii) Nanobodies have a natural tendency to bind cavities and often target receptor/ligand interfaces. As such they are a rich source of blocking reagents. Also, the fusion of two non-blocking binders by very short linkers can also lead to extremely efficient biparatopic blocking reagents able to trap their targets in a non functional conformation. Importantly, it has the obvious potential of simultaneously blocking two receptors within the same immune synapse, possibly allowing efficient synergy effects. We are exploring the potential of this approach by targeting inhibitory receptors expressed on exhausted NK and T cells.
2 / Characterizing tumors using innovative nanosensors
The availability of a panel of nanobodies directed against tumor or immune cell exhaustion markers is also an opportunity to better characterize tumors in terms of antigen expression and immune cell infiltration, as a step toward personalized immunotherapy. We are generating very bright nanosensors consisting of quantum dot-nanobody conjugates that can be used to efficiently detect tumor cells in tissues by multiplexed immunofluorescence. We are also using the high selectivity of nanobodies to create conformational sensors able to distinguish active and inactive conformation of some tumor markers such as EGFR. Finally, once labeled by a radio-isotope using a site-directed enzymatic procedure, these nanobodies are ideal tools for non invasive in vivo imaging. Their high affinity and natural short half-life rapidly generate very high tumor to bold that can be advantageously used to detect tumors and follow their progression during therapy.
The team leader
Patrick Chames obtained an INSA Engineer diploma (Toulouse, France) in 1993 and a PhD in (Marseille, France) in 1997 in the field of antibody engineering. From 1997 to 2001, he worked in the laboratory of phage display pioneer Hennie R. Hoogenboom, Maastricht, NL where he isolated by phage display the first human antibody fragment specifically binding to a cancer related class I MHC complex (TCR-like antibodies). From 2001 to 2005, he worked for the french CAR T-cell company (Cellectis SA, Paris). Since 2005 he is working for the French National center for research (CNRS). Since 2012, he is leader of the “Antibody therapeutics and Immunotargeting team” of the Cancer Research Center of Marseille (CRCM).