Targeting MLKL-Driven Necroptosis: A Therapeutic Target in Inflammation and Host Defense.

Necroptosis is a regulated form of programmed cell death that helps the body defend itself against infections and cellular stress, especially when apoptosis is blocked. At the center of this process is mixed lineage kinase domain-like (MLKL) protein, the final effector of necroptosis, which is activated downstream of receptor-interacting protein kinase 3 (RIPK3). Once phosphorylated, MLKL changes shape, assembles into oligomers, moves to cellular membranes, and disrupts membrane integrity, ultimately causing cell death. While this RIPK3-MLKL pathway has been well described, it is becoming increasingly clear that MLKL regulation is more complex than originally thought. Recent findings show that MLKL can be modified and activated through alternative mechanisms, even in the absence of RIPK3, and that post-translational modifications such as ubiquitination further fine-tune its activity. Notably, deleting RIPK3 or MLKL does not consistently resolve inflammatory phenotypes in experimental models, suggesting that MLKL has context-dependent functions that extend beyond its role in necroptosis. In line with this idea, MLKL has been implicated in inflammatory signaling, interferon responses, and innate immunity, and is frequently targeted by viruses seeking to evade host defenses. Beyond infections, aberrant MLKL activation contributes to a wide range of chronic diseases, including atherosclerosis, cardiometabolic disorders, liver disease, neurodegeneration, and cancer. In these settings, sustained MLKL-mediated membrane damage and release of danger signals drive ongoing inflammation and tissue injury rather than protective cell elimination. In this review, we provide an overview of MLKL structure, activation, and regulation in both necroptotic and non-necroptotic contexts. We also discuss emerging therapeutic strategies aimed at targeting MLKL activation, membrane engagement, and stability, and highlight key unanswered questions that must be addressed to translate MLKL biology into effective clinical interventions.