Crystallographic approaches to study the interaction modes of PD-1- and CTLA-4-blocking antibodies

Area of Science:

• Immunology
• Structural Biology
• Cancer Research

Background:

• Programmed death 1 (PD-1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) are critical negative regulators of T-cell immune responses.
• Immune checkpoint inhibitors (ICIs) have revolutionized cancer immunotherapy by releasing these inhibitory signals, enhancing anti-tumor immunity.
• Understanding the atomic structure of immune checkpoint receptor/ICI complexes is vital for elucidating inhibition mechanisms and guiding biotherapeutic design.

Purpose of the Study:

• To describe efficient methods for producing milligram quantities of human immune checkpoint receptors and ICI antibody Fv fragments.
• To facilitate structural studies essential for understanding ICI mechanisms of action.
• To enable the rational design of next-generation biotherapeutics for cancer treatment.

Main Methods:

• Production of extracellular domains of human immune checkpoint receptors (PD-1, CTLA-4).
• Expression and purification of Fv fragments from therapeutic ICI antibodies (pembrolizumab, ipilimumab).
• Generation of milligram-scale protein complexes for structural analysis.

Main Results:

• Successful efficient production of milligram quantities of PD-1 and CTLA-4 extracellular domains.
• Successful efficient production of milligram quantities of pembrolizumab Fv and ipilimumab Fv fragments.
• Availability of sufficient material for detailed structural studies of receptor-antibody complexes.

Conclusions:

• The described methods provide a robust platform for producing essential components for structural biology of immune checkpoints.
• This work supports the mechanistic understanding of PD-1 and CTLA-4 inhibition by therapeutic antibodies.
• Facilitates the rational design and optimization of novel immune checkpoint inhibitors for improved cancer immunotherapy.