Effective IgG1 Fc silencing : Characterisation of residual binding and functional activity

What is Fc silencing? 

Monoclonal antibodies (mAbs) are pivotal in mediating effector functions. They do this by engaging with Fc gamma receptors on immune cells and initiating the complement cascade via their Fc domains. 

For therapeutic applications where effector function is undesirable, a range of Fc ‘silencing’ techniques have been developed to mitigate or nullify complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC) responses. However, despite these efforts, residual binding and functional activity are often still detectable. 

mAbsolve’s innovation, the STR mutation, marks a significant advancement in Fc silencing. It demonstrates complete cessation of Fc binding and functional activities. Using RoukenBio’s advanced primary cell and SPR platforms, we can rigorously assess antibody constructs to ensure effective silencing. This sets a new standard in the development of safer therapeutic antibodies. 

The benefits of RoukenBio’s approach 

• Standard assay designs greatly reduce time spent in optimisation

• Control of donor material and Fc receptor stocks

• Methods are highly sensitive and physiologically relevant

• Target cell line development in-house 

• Low sample volume requirements

From SPR binding assays and primary cell functional assays, our data conclusively shows that neither employing IgG2 and IgG4 isotypes, nor the LALA mutation completely silences Fc binding and function. 

Only the STR mutation achieves complete Fc silencing. As the SPR and bioassay data demonstrates, it is necessary to conduct both binding and primary cell functional assays to fully characterize Fc activity, as well as understand the implications of any lingering activity.