A novel tumor necrosis factor-alpha-targeting protein degrader for the treatment of acute liver failure.

BACKGROUND AND AIMS: Tumor necrosis factor-α (TNF-α) is a well-characterized causal mediator in the pathogenesis of acute liver failure (ALF). Despite the efficacy of TNF-α inhibitors (e.g., antibodies and Fc-fused receptor proteins) in animal models, clinic translation has not been successful so far, largely due to sustained repression of TNF-α signaling and Fc-mediated deleterious immune responses. To address these obstacles, we aim to develop a new modality targeting TNF-α by employing lysosome-targeting protein degradation technology. METHODS: Murine Niemann-Pick type C 2 (NPC2) or a mutated form of human insulin-like growth factor 2 (IGF2) (Y27L, IGF2m) was fused to the C-terminus of a TNF-α-targeting nanobody (Nb) via a peptide linker. The ability of Nb-NPC2 and Nb-IGF2m to deliver TNF-α into the lysosomal compartment for degradation, thereby inhibiting TNF-α-induced apoptosis, was examined in IGF2R-expressing cell lines. ALF models induced by co-injection of D-Galactosamine (GalN) with human TNF-α or LPS were used to evaluate the protective efficacy of the fusion proteins. RESULTS: Nb-NPC2 potently suppressed TNF-α-induced cellular apoptosis via the interaction between mannose-6-phosphate (M6P)-bearing NPC2 and IGF2R. Mechanistically, the fusion protein actively hijacked TNF-α to be transported into the lysosome for degradation. Nb-NPC2 administration protected mice from ALF-induced lethality and tissue damage by rapidly clearing TNF-α in circulation. Furthermore, a non-glycosylated version (i.e., Nb-IGF2m) exhibited comparable effects in vitro and in vivo. CONCLUSIONS: Nb-NPC2 (IGF2m) represents a novel avenue with therapeutic potential for ALF, primarily via lysosome-targeting degradation of TNF-α. IMPACT AND IMPLICATIONS: Acute liver failure is a life-threatening inflammatory disease in which TNF-α serves as a central mediator to trigger hepatocyte death, thereby causing vascular dysfunction and liver injury. However, attempts to block TNF-α using antibodies or Fc-fusion proteins in ALF patients have provided no survival benefit to date, largely attributable to sustained suppression of TNF-α as well as Fc-mediated deleterious immune reactions. Our study proposed a novel modality by employing a lysosome-targeting degradation strategy that rapidly cleared TNF-α in circulation and consequently exhibited protective efficacy in ALF mouse models. Given the huge unmet medical need for ALF therapy, the therapeutic potential of this avenue deserves further validation.