Tumor necrosis factor ligand superfamily member 9 (4-1BBL) (4-1BBL)

Tumor necrosis factor ligand superfamily member 9 (4-1BBL) is a type II transmembrane protein primarily expressed on activated antigen-presenting cells (APCs), including dendritic cells, B cells, and macrophages (UniProt: P41273). It serves as the endogenous ligand for the 4-1BB (CD137) receptor, which is inducibly expressed on activated T cells and natural killer (NK) cells (PMID: 29109432). The interaction between 4-1BBL and its receptor provides a critical costimulatory signal that promotes T-cell survival, expansion, and the production of pro-inflammatory cytokines like IFN-gamma (PMID: 28490530). In the tumor microenvironment, the 4-1BB/4-1BBL pathway is often under-stimulated, leading to T-cell exhaustion and immune evasion by cancer cells (PMID: 30633910). Therapeutic interventions aim to trigger this pathway using 4-1BB agonistic antibodies or 4-1BBL fusion proteins, such as RO7122290, which are designed to enhance anti-tumor immunity by mimicking the natural ligand's activity (PMID: 31142651). These agents are often developed as bispecific molecules to ensure localized activation within the tumor, thereby reducing the risk of systemic toxicity (PMID: 33033171). Clinical development of 4-1BBL-based therapies focuses on combination treatments with checkpoint inhibitors to synergistically boost the immune response against various malignancies (PMID: 31534005). However, systemic activation of the 4-1BB/4-1BBL axis has been historically associated with significant safety concerns, most notably immune-mediated hepatotoxicity and cytokine release syndrome (PMID: 31142651).

Other names

CD137LTNFSF94-1BB ligandCD137 ligand

Agonism of the 4-1BB (CD137) receptor through ligand-mimicry or direct binding to provide co-stimulatory signals to T cells and NK cells, thereby enhancing anti-tumor immunity.