Structural Analysis of Tilvestamab in Complex with AXL.

Area of Science:

• Biochemistry
• Structural Biology
• Oncology

Background:

• AXL receptor tyrosine kinase (RTK) plays a key role in cancer cell signaling.
• Growth arrest-specific protein 6 (GAS6) is the ligand for AXL.
• Tilvestamab (BGB149) is a novel therapeutic antibody targeting AXL.

Purpose of the Study:

• To structurally characterize the complex formed between AXL and the anti-AXL antibody, tilvestamab.
• To provide a foundation for optimizing high-resolution structural studies and drug design.

Main Methods:

• Negative-stain and cryogenic transmission electron microscopy (cryo-EM).
• Synchrotron small-angle X-ray scattering (SAXS).
• Utilized monomeric soluble AXL extracellular domain, tilvestamab Fab fragment, and anti-Fab nanobody for homogeneous sample preparation.

Main Results:

• Confirmed successful complex formation between AXL and tilvestamab using SAXS and cryo-EM.
• Generated a low-resolution 3D model of the tilvestamab-AXL complex.
• Identified methods for creating homogeneous samples suitable for structural biology.

Conclusions:

• Structural insights into the AXL-tilvestamab complex were obtained.
• The study facilitates optimization for high-resolution structural determination.
• Findings support the rational design of mutations to modulate antibody binding affinity and specificity for AXL.