Highly Potent Th1-Type NKT Cell Agonists as Immunotherapeutic Agents via Conformational Restriction Design

Th1-selective natural killer T (NKT) cell agonists are promising immunotherapeutic agents due to their ability to promote cellular immunity against tumors and intracellular pathogens. However, the development of potent Th1-biased NKT cell agonists has remained slow despite decades of structural modification of the prototypical Th0-type agonist α-galactosylceramide (αGalCer). In this work, we used a distinct conformational restriction strategy to design a series of αGalCer branched analogs based on the spatial architecture of the CD1d binding groove, rather than through residue-focused modifications in previous αGalCer derivatizations. The linear acyl chain of αGalCer was replaced with branched motifs to restrict flexibility and enhance binding stability. Two optimized candidates GCB-27a and GCB-27b induced strong Th1-biased responses in vivo, with over 10-fold higher IFN-γ and limited IL-4 levels compared to αGalCer, establishing them among the most potent Th1-biased NKT cell agonists. They also demonstrated superior antitumor efficacy in mice. Importantly, these agonists retained significant activity in human NKT cells, highlighting their translational potential as promising immunotherapeutic agents.

NKT cell agonist; branched chain; conformational restriction; glycolipid; immunotherapy; α-galactosylceramide.