Discovery, total chemical synthesis, and validation of “mirror-image” D-Nanobodies

The central role of molecularly-targeted therapeutics and imaging probes in translational research entails the development of an ever-growing arsenal of “chemical biologics” endowed with optimal in vivo properties. In this regard, mAbs and their derivatives (e.g.

ADCs) still suffer from unsettled drawbacks involving difficulties in production and characterization, leading to heterogeneous conjugates in terms of size, potency and toxicity.

Chemical modifications on mAbs are highly unreliable due to their complex structure: a central problem in this discipline, where heterogeneous drug-to-antibody ratio (DAR) and conjugation site represent significative limitations.

Immunogenicity is a major drawback which affects humanized, as well as fully-human mAbs, and is exacerbated by long half-lives.

Cases of unwanted activation of the immune system reportedly degenerated to life-threatening conditions such as acute anaphylaxis, serum sickness and cytokine release syndrome. Their bulky size (≈150 kDa) hinders their extravasation, impairing their efficiency to enter tumors.

Nanobodies (Nbs) are the smallest naturally-derived antibody fragments (≈13-14 kDa) that retain antigen-binding affinities in the same range of mAbs (nM to pM affinity range) while having extremely reduced half-lives ( ≈ 15 min.) when not bound to their target, thanks to a fast renal excretion.

MirrorBody intends to push the boundaries of targeted “chemical biologics” via an interdisciplinary approach that exploits both immunology and synthetic chemistry techniques for the generation of synthetic D-nanobodies that bind natural L-targets with high affinity.

Such unprecedented synthetic D-Nbs will be endowed with improved biocompatibility, and will enable “plug-and-play” approaches for the controlled conjugation of diverse moieties.