Structural analysis of light chain-driven bispecific antibodies targeting CD47 and PD-L1.

In contrast to natural antibodies that rely mainly on the heavy chain to establish contacts with their cognate antigen, we have developed a bispecific antibody format in which the light chain (LC) drives antigen binding and specificity. To better understand epitope-paratope interactions in this context, we determined the X-ray crystallographic structures of an antigen binding fragment (Fab) in complex with human CD47 and another Fab in complex with human PD-L1. These Fabs contain a κ-LC and a λ-LC, respectively, which are paired with an identical heavy chain (HC).

Development and characterization of NILK-2301, a novel CEACAM5xCD3 κλ bispecific antibody for immunotherapy of CEACAM5-expressing cancers.

Background: T-cell retargeting to eliminate CEACAM5-expressing cancer cells via CEACAM5xCD3 bispecific antibodies (BsAbs) showed limited clinical activity so far, mostly due to insufficient T-cell activation, dose-limiting toxicities, and formation of anti-drug antibodies (ADA).

Methods: We present here the generation and preclinical development of NILK-2301, a BsAb composed of a common heavy chain and two different light chains, one kappa and one lambda, determining specificity (so-called κλ body format).

Results: NILK-2301 binds CD3ɛ on T-cells with its lambda light chain arm with an affinity of ≈100 nM, and the CEACAM5 A2 domain on tumor cells by its kappa light chain arm with an affinity of ≈5 nM.

Round optimization for improved discovery of native bispecific antibodies.

The assembly of bispecific antibodies (bsAb) that retain the structure of a standard IgG can be challenging as the correct pairing of the different heavy and light chains has to be ensured while unwanted side products kept to a minimum. The use of antibodies sharing a common chain facilitates assembly of such bsAb formats but requires additional efforts during the initial discovery phase. We have developed a native bsAb format called κλ body based on antibodies that, while being specific for different antigens, share the same heavy chain.

Dual display: phage selection driven by co-engagement of two targets by two different antibody fragments.

Antibody phage display technology has supported the emergence of numerous therapeutic antibodies. The development of bispecific antibodies, a promising new frontier in antibody therapy, could be facilitated by new phage display approaches that enable pairs of antibodies to be co-selected based on co-engagement of their respective targets. We describe such an approach, making use of two complementary leucine zipper domains that heterodimerize with high affinity.

Btn2a2, a T cell immunomodulatory molecule coregulated with MHC class II genes.

Evidence has recently emerged that butyrophilins, which are members of the extended B7 family of co-stimulatory molecules, have diverse functions in the immune system. We found that the human and mouse genes encoding butyrophilin-2A2 (BTN2A2) are regulated by the class II trans-activator and regulatory factor X, two transcription factors dedicated to major histocompatibility complex class II expression, suggesting a role in T cell immunity. To address this, we generated Btn2a2-deficient mice.