• Meixiao Long, Kyle Beckwith, Priscilla Do, Bethany L Mundy, Amber Gordon, Amy M Lehman, Kami J Maddocks, Carolyn Cheney, Jeffrey A Jones, Joseph M Flynn, Leslie A Andritsos, Farrukh Awan, Joseph A Fraietta, Carl H June, Marcela V Maus, Jennifer A Woyach, Michael A Caligiuri, Amy J Johnson, Natarajan Muthusamy, and John C Byrd.
• Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, USA.
• J. Clin. Invest. 2017 Aug 1; 127 (8): 3052-3064.

BackgroundIbrutinib has been shown to have immunomodulatory effects by inhibiting Bruton's tyrosine kinase (BTK) and IL-2-inducible T cell kinase (ITK). The relative importance of inhibiting these 2 kinases has not been examined despite its relevance to immune-based therapies.MethodsPeripheral blood mononuclear cells from chronic lymphocytic leukemia (CLL) patients on clinical trials of ibrutinib (BTK/ITK inhibitor; n = 19) or acalabrutinib (selective BTK inhibitor; n = 13) were collected serially. T cell phenotype, immune function, and CLL cell immunosuppressive capacity were evaluated.ResultsIbrutinib markedly increased CD4+ and CD8+ T cell numbers in CLL patients. This effect was more prominent in effector/effector memory subsets and was not observed with acalabrutinib. Ex vivo studies demonstrated that this may be due to diminished activation-induced cell death through ITK inhibition. PD-1 and CTLA-4 expression was significantly markedly reduced in T cells by both agents. While the number of Treg cells remained unchanged, the ratio of these to conventional CD4+ T cells was reduced with ibrutinib, but not acalabrutinib. Both agents reduced expression of the immunosuppressive molecules CD200 and BTLA as well as IL-10 production by CLL cells.ConclusionsIbrutinib treatment increased the in vivo persistence of activated T cells, decreased the Treg/CD4+ T cell ratio, and diminished the immune-suppressive properties of CLL cells through BTK-dependent and -independent mechanisms. These features provide a strong rationale for combination immunotherapy approaches with ibrutinib in CLL and other cancers.Trial RegistrationClinicalTrials.gov NCT01589302 and NCT02029443. Samples described here were collected per OSU-0025.FundingThe National Cancer Institute.

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