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Interactions between Ibrutinib and Anti-CD20 Antibodies: Competing Effects on the Outcome of Combination Therapy.

ABSTRACT: PURPOSE:Clinical trials of ibrutinib combined with anti-CD20 monoclonal antibodies (mAb) for chronic lymphocytic leukemia (CLL) report encouraging results. Paradoxically, in preclinical studies, in vitro ibrutinib was reported to decrease CD20 expression and inhibit cellular effector mechanisms. We therefore set out to investigate effects of in vivo ibrutinib treatment that could explain this paradox. EXPERIMENTAL DESIGN:Patients received single-agent ibrutinib (420 mg daily) on an investigator-initiated phase II trial. Serial blood samples were collected pretreatment and during treatment for ex vivo functional assays to examine the effects on CLL cell susceptibility to anti-CD20 mAbs. RESULTS:We demonstrate that CD20 expression on ibrutinib was rapidly and persistently downregulated (median reduction 74%, day 28, P < 0.001) compared with baseline. Concomitantly, CD20 mRNA was decreased concurrent with reduced NF-?B signaling. An NF-?B binding site in the promoter of MS4A1 (encoding CD20) and downregulation of CD20 by NF-?B inhibitors support a direct transcriptional effect. Ex vivo, tumor cells from patients on ibrutinib were less susceptible to anti-CD20 mAb-mediated complement-dependent cytotoxicity than pretreatment cells (median reduction 75%, P < 0.001); however, opsonization by the complement protein C3d, which targets cells for phagocytosis, was relatively maintained. Expression of decay-accelerating factor (CD55) decreased on ibrutinib, providing a likely mechanism for the preserved C3d opsonization. In addition, ibrutinib significantly inhibited trogocytosis, a major contributor to antigen loss and tumor escape during mAb therapy. CONCLUSIONS:Our data indicate that ibrutinib promotes both positive and negative interactions with anti-CD20 mAbs, suggesting that successfully harnessing maximal antitumor effects of such combinations requires further investigation.

SUBMITTER: Skarzynski M

PROVIDER: S-EPMC4703510 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Interactions between Ibrutinib and Anti-CD20 Antibodies: Competing Effects on the Outcome of Combination Therapy.

Skarzynski Martin M Niemann Carsten U CU Lee Yuh Shan YS Martyr Sabrina S Maric Irina I Salem Dalia D Stetler-Stevenson Maryalice M Marti Gerald E GE Calvo Katherine R KR Yuan Constance C Valdez Janet J Soto Susan S Farooqui Mohammed Z H MZ Herman Sarah E M SE Wiestner Adrian A

Clinical cancer research : an official journal of the American Association for Cancer Research 20150817 1

<h4>Purpose</h4>Clinical trials of ibrutinib combined with anti-CD20 monoclonal antibodies (mAb) for chronic lymphocytic leukemia (CLL) report encouraging results. Paradoxically, in preclinical studies, in vitro ibrutinib was reported to decrease CD20 expression and inhibit cellular effector mechanisms. We therefore set out to investigate effects of in vivo ibrutinib treatment that could explain this paradox.<h4>Experimental design</h4>Patients received single-agent ibrutinib (420 mg daily) on a ...[more]

PMID: 26283682

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Project description:BackgroundDiffuse large B cell lymphoma (DLBCL) is the most common form of lymphoma. Although durable remissions can be achieved in more than half of these patients, DLBCL remains a significant clinical challenge, with approximately 30% of patients not being cured. BCR-associated kinases (SYK, BTK, and PI3K) inhibitors have exhibited encouraging pre-clinical and clinical effects, as reported by many researchers. Early studies demonstrated that protein kinase C-β (PKCβ) inhibitors alter phosphorylation level the Bruton's tyrosine kinase (BTK), which leads to enhanced BTK signaling. Here, for the first time, we investigate whether the combination of PKCβ inhibitor enzastaurin and BTK inhibitor ibrutinib has synergistic anti-tumor effects in DLBCL.MethodsIn vitro cell proliferation was analyzed using Cell Titer-Glo Luminescent Cell Viability Assay. Induction of apoptosis and cell cycle arrest were measured by flow cytometry. Western Blotting analysis was used to detect the essential regulatory enzymes in related signaling pathways. RNA-seq was conducted to evaluate the whole transcriptome changes brought by co-treatment with low doses of enzastaurin and ibrutinib. The synergistic anti-tumor effects of enzastaurin and ibrutinib were also evaluated in vivo.ResultsCombination of enzastaurin and ibrutinib produced a lasting synergistic effect on the survival and proliferation of DLBCL cells, including reduction of proliferation, promoting apoptosis, inducting G1 phase arrest, preventing cell invasion and migration, and down-regulating activation of downstream signaling. More importantly, whole-transcriptome changes results showed that combination therapy worked synergistically to regulate whole-transcriptome expression compared with enzastaurin and ibrutinib alone. Co-treatment with low doses of enzastaurin and ibrutinib could effectively downregulate BCR, NF-κB, JAK and MAPK related signaling pathway. Furthermore, the mRNA expression analysis further indicated that co-treatment significantly decreased the mRNA levels of NOTCH1. The combination effect in inhibiting proliferation of DLBCL cells probably was realized through suppression of NOTCH1 expression. Finally, the anti-tumor activity of co-treatment also was demonstrated in vivo.ConclusionsCombination of enzastaurin and ibrutinib had synergistic anti-tumor effects in DLBCL, independent of molecular subtype. These results provided a sound foundation for an attractive therapeutic treatment, and the simultaneous suppression of BTK and PKCβ might be a new treatment strategy for DLBCL.

Dataset Information

Interactions between Ibrutinib and Anti-CD20 Antibodies: Competing Effects on the Outcome of Combination Therapy.

Publications

Interactions between Ibrutinib and Anti-CD20 Antibodies: Competing Effects on the Outcome of Combination Therapy.

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