Development and Differentiation in Monobodies Based on the Fibronectin Type 3 Domain

As a non-antibody scaffold, monobodies based on the fibronectin type III (FN3) domain overcome antibody size and complexity while maintaining analogous binding loops. However, antibodies and their derivatives remain the gold standard for the design of new therapeutics. In response, clinical-stage therapeutic proteins based on the FN3 domain are beginning to use native fibronectin function as a point of differentiation. The small and simple structure of monomeric monobodies confers increased tissue distribution and reduced half-life, whilst the absence of disulphide bonds improves stability in cytosolic environments. Where multi-specificity is challenging with an antibody format that is prone to mis-pairing between chains, multiple FN3 domains in the fibronectin assembly already interact with a large number of molecules. As such, multiple monobodies engineered for interaction with therapeutic targets are being combined in a similar beads-on-a-string assembly which improves both efficacy and pharmacokinetics. Furthermore, full length fibronectin is able to fold into multiple conformations as part of its natural function and a greater understanding of how mechanical forces allow for the transition between states will lead to advanced applications that truly differentiate the FN3 domain as a therapeutic scaffold.

[Molecular predictors in immune oncology]

The current rapid development of novel therapeutic approaches in immune oncology (IO) and specifically in the field of immune checkpoint inhibition is accompanied by an equally dynamic development of novel biomarker approaches for the identification of responding/non-responding patients under IO treatment. In addition to the measurement of the expression of checkpoint ligands/receptors, complex molecular predictors are gaining increasing attention in certain IO treatment constellations. This includes the entity informed identification of molecularly defined biological tumor subtypes (e.g., microsatellite instable neoplasms), the measurement of tumor mutational load and immune cell effector signatures as relatively routine diagnostic compatible novel biomarker strategies. In addition, a multitude of even more complex molecular IO biomarker approaches is emerging. This development is accompanied by new patient selection strategies which are based on the simultaneous combinatorial evaluation of more than one parameter. This article provides a comprehensive overview on currently relevant aspects in the field of IO biomarkers.