The human formyl peptide receptor 2 (FPR2) plays a crucial role in host defense and inflammation, and has been considered as a drug target for chronic inflammatory diseases. A variety of peptides with different structures and origins have been characterized as FPR2 ligands. However, the ligand-binding modes of FPR2 remain elusive, thereby limiting the development of potential drugs. Here we report the crystal structure of FPR2 bound to the potent peptide agonist WKYMVm at 2.8 Å resolution. The structure adopts an active conformation and exhibits a deep ligand-binding pocket. Combined with mutagenesis, ligand binding and signaling studies, key interactions between the agonist and FPR2 that govern ligand recognition and receptor activation are identified. Furthermore, molecular docking and functional assays reveal key factors that may define binding affinity and agonist potency of formyl peptides. These findings deepen our understanding about ligand recognition and selectivity mechanisms of the formyl peptide receptor family.

Cancer immunotherapy is impaired by the intrinsic and adaptive immune resistance. Herein, a bispecific prodrug nanoparticle was engineered for circumventing immune evasion of the tumor cells by targeting multiple immune resistance mechanisms. A disulfide bond-linked bispecific prodrug of NLG919 and JQ1 (namely NJ) was synthesized and self-assembled into a prodrug nanoparticle, which was subsequently coated with a photosensitizer-modified and tumor acidity-activatable diblock copolymer PHP for tumor-specific delivery of NJ. Upon tumor accumulation via passive tumor targeting, the polymeric shell was detached for facilitating intracellular uptake of the bispecific prodrug. NJ was then activated inside the tumor cells for releasing JQ1 and NLG919 via glutathione-mediated cleavage of the disulfide bond. JQ1 is a bromodomain-containing protein 4 inhibitor for abolishing interferon gamma-triggered expression of programmed death ligand 1. In contrast, NLG919 suppresses indoleamine-2,3-dioxygenase 1-mediated tryptophan consumption in the tumor microenvironment, which thus restores robust antitumor immune responses. Photodynamic therapy (PDT) was performed to elicit antitumor immunogenicity by triggering immunogenic cell death of the tumor cells. The combination of PDT and the bispecific prodrug nanoparticle might represent a novel strategy for blockading multiple immune evasion pathways and improving cancer immunotherapy.

Cyclic GMP-AMP synthase (cGAS), a key mediator of the cGAS-STING DNA sensing pathway that triggers type-I interferon responses, plays a crucial role in innate immunity and has been implicated in the pathogenesis of various disease. Despite advances in the development of cGAS inhibitors, none have reached the market and there remains an unmet need for divergent chemical scaffolds with high selectivity, potency across species, and target-adaptive mechanisms of action to explore cGAS’s potential as a therapeutic target. Here we report the structural, biochemical, cellular, and mechanistic characterization of the XL series of allosteric inhibitors, designed to engage an innovative allosteric site near the activation loop of cGAS. Among them, XL-3156 and XL-3158 emerge as potent, selective, cross-species cGAS inhibitors that simultaneously occupy allosteric and orthosteric sites, stabilizing the activation loop in a closed, inactive conformation and thereby attenuating the cGAS-DNA interactions. Moreover, these allosteric inhibitors, also known as protein condensation inhibitors (PCIs), significantly suppress cGAS-DNA condensate formation, triggering a morphological transition from liquid-solid phase separation (LSPS) to liquid-liquid phase separation (LLPS) at the molecular level while eliminating LLPS in cells. The distinct mechanism of action enables PCIs to achieve synergistic effects in combination with orthosteric inhibitors. These results establish a mechanism-driven pharmacological strategy to inhibit cGAS through PCIs that modulate phase separation primarily by engagement of the allosteric site.

The essential role of RIPK3 in necroptosis makes its inhibition a promising therapeutic strategy. However, the development of RIPK3 inhibitors has been hampered by on-target apoptosis and limited kinase selectivity. Inspired by the R69H mutation, which prevents on-target apoptosis by disrupting RIPK3 dimerization, we design LK-series inhibitors that effectively inhibit RIPK3 in biochemical assays and block TNF-α-induced necroptosis in both mouse L929 and human HT29 cells without inducing apoptosis. The representative compound, LK01003, shows high selectivity across a panel of 379 kinases. Our structural studies reveal that LK compounds act as Type I^1/2 inhibitors, engaging a unique hydrophobic site and stabilizing an inactive conformation of RIPK3. Moreover, several type II inhibitors are also revealed to maintain RIPK3 in the inactive conformation and do not induce on-target apoptosis. These findings suggest a promising strategy for rational design of safe and selective inhibitors by locking the inactive conformation of RIPK3.