Transmembrane proteins effector monoclonal antibodies


Transmembrane proteins are probably the most complex and challenging antigens to target with monoclonal antibodies. Indeed, despite their strong presence in the animal kingdom and their implications in many cellular mechanisms, they remain very difficult to access due to intrinsic properties.

Challenges of transmembrane antigens

Membrane receptors present the following challenges:

  • Low exposure of epitopic regions,
  • Structurally complex antigens with many loops, multiple areas of interaction with the ligand and highly dependent on the direct environment since transmembrane proteins are embedded in the lipid bilayer of membranes,
  • Low immunogenicity when injected into animals,
  • Traditionally low expressed, and toxic when over-expressed
  • Highly conserved throughout the animal kingdom.


Technical solutions for monoclonal antibody generation against membrane targets


Many companies have developed different methodologies to express membrane antigens.


But due to their hydrophobic domain and multi-units structure, transmembrane proteins remain highly difficult to purify and are easily denatured during the Down-Stream Process. Moreover, due to the use of detergents, heterologous membrane antigen expression don't guarantee the maintenance of a native conformation of the expressed membrane protein.


The solution is to develop whole-cell antigen and several entities now offer CHO and HEK cell lines expressing different GPCRs. However, these cells do not offer a high density of the antigen of interest on the cell surface (resulting in low immunogenicity) and generate numerous non-specific monoclonal antibodies which pose major problems during the screening phase (high background of irrelevant proteins). 


SYnAbs has so developed its own vector (SYnDNA) allowing the :

  • expression of the appropriate surface density of the target GPCR or other transmembrane protein 
  • correct folding and post-translational processing of mammalian target receptors

on a rat or mouse cell lines (SYnCell), for a combined DNA immunization and whole-cell syngeneic/autologous immunization in rat-LOU (SYnAbs proprietary species) and mice species.


The application of such technologies have led to the generation of SYnAbs anti-CD2 rat monoclonal Siplizumab (licensed to MedImmune, MEDI-507), and numerous other functional therapeutic antibodies like our LO-CD2b or LO-TACT anti-CD25 and other anti-GPCR drug candidates.