Integrins LFA-1 and VLA-4 (allosteric activation)

Class

Oral small-molecule integrin allosteric activator (immune agonist)

Pathway

Selectively activates LFA-1/VLA-4 to enhance immune-cell trafficking, antigen presentation, and T-cell activation, aiming to resensitize anti-PD-1-resistant tumors

LFA-1 and VLA-4 are integrins, a family of cell-surface adhesion receptors expressed on immune cells such as T lymphocytes. They mediate the physical attachment of immune cells to blood vessel walls and to other cells, including antigen-presenting cells and tumor cells, through partner proteins such as ICAM-1 and VCAM-1. This adhesion step is required for immune cells to leave the bloodstream, enter tissue, and form stable contacts needed for antigen presentation and T-cell activation. Most integrin-targeted drugs are antagonists that block this adhesion to dampen unwanted immune trafficking in autoimmune or inflammatory disease. This mechanism instead uses a small molecule that allosterically activates LFA-1 and VLA-4, shifting them toward their high-affinity, adhesion-competent shape rather than blocking them. The rationale is that some tumors evade immune attack partly because T cells fail to adhere efficiently, infiltrate the tumor, or form durable synapses with antigen-presenting cells, which can blunt the benefit of checkpoint inhibitors like anti-PD-1 antibodies. By promoting integrin-mediated adhesion and trafficking, this approach aims to restore immune-cell infiltration and antigen presentation, potentially making resistant tumors more responsive to checkpoint blockade.