Abstract
Simple SummaryCD137 is an interesting immuno-oncology target. The recent advances in CD137 targeting technologies to mitigate toxicity while maintaining potency have made this space even more attractive. In this article, our current understanding of CD137 biology is reviewed along with data from clinical trials targeting T cell co-stimulatory receptors in the TNFRSF. Next generation CD137 targeting molecules currently in early clinical development are also reviewed. Finally, the future challenges of CD137 targeting molecules are discussed.Immune checkpoint inhibitors have altered the treatment landscape significantly in several cancers, yet not enough for many cancer patients. T cell costimulatory receptors have been pursued as targets for the next generation of cancer immunotherapies, however, sufficient clinical efficacy has not yet been achieved. CD137 (TNFRSF9, 4-1BB) provides co-stimulatory signals and activates cytotoxic effects of CD8+ T cells and helps to form memory T cells. In addition, CD137 signalling can activate NK cells and dendritic cells which further supports cytotoxic T cell activation. An agonistic monoclonal antibody to CD137, urelumab, provided promising clinical efficacy signals but the responses were achieved above the maximum tolerated dose. Utomilumab is another CD137 monoclonal antibody to CD137 but is not as potent as urelumab. Recent advances in antibody engineering technologies have enabled mitigation of the hepato-toxicity that hampered clinical application of urelumab and have enabled to maintain similar potency to urelumab. Next generation CD137 targeting molecules currently in clinical trials support T cell and NK cell expansion in patient samples. CD137 targeting molecules in combination with checkpoint inhibitors or ADCC-enhancing monoclonal antibodies have been sought to improve both clinical safety and efficacy. Further investigation on patient samples will be required to provide insights to understand compensating pathways for future combination strategies involving CD137 targeting agents to optimize and maintain the T cell activation status in tumors.
Highlights
CD137, or 4-1BB/tumor necrosis factor receptor superfamily (TNFRSF9) was first reported in 1989 as an inducible gene in T cells through cDNA sequencing analysis [1].Later, it was found that CD3 stimulation could induce CD137 expression where antibodymediated cross-linking of CD137 resulted in T cell proliferation [2]
It was found that CD3 stimulation could induce CD137 expression where antibodymediated cross-linking of CD137 resulted in T cell proliferation [2]
Angiogenesis is critical for persistent tumor growth and metastasis and dysregulation of angiogenesis creates high interstitial fluid pressure (IFP) in the tumor, which results in hypoxia, low pH which inhibits immune cell activation, poor blood supply, and impairs the delivery of systemic administered therapies to tumors [87]
Summary
CD137, or 4-1BB/tumor necrosis factor receptor superfamily (TNFRSF9) was first reported in 1989 as an inducible gene in T cells through cDNA sequencing analysis [1]. Oncytokine activatedprovival, memory formation and stronger effector function for cytotoxicity and cells can deliver co-stimulatory signals to cells resulting in cell proliferation, survival, duction [10] (Figure 1). CD28, the constitutively expressed co-stimulatory attractive therapeutic preferential proliferation of CD8++T cells makes CD137 a receptor on T cells activates CD4 T cells more than CD8+ T cells [11]. Co-stimulatory receptors have minimal signaling by proliferation of CD8+ T cells makes CD137 a attractive therapeutic target for themselves but are essential to drive T cells to have respond to antigens presented on tumor anti-cancer treatment. B cell proliferation anddoes survival but class does switch not help class switch [20]
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