Monoclonal antibodies can block cellular interactions that negatively regulate T-cell immune responses, such as CD80/CTLA-4 and PD-1/PD1-L, amplifying preexisting immunity and thereby evoking antitumor immune responses. Ibrutinib, an approved therapy for B-cell malignancies, is a covalent inhibitor of BTK, a member of the B-cell receptor (BCR) signaling pathway, which is critical to the survival of malignant B cells. Interestingly this drug also inhibits ITK, an essential enzyme in Th2 T cells and by doing so it can shift the balance between Th1 and Th2 T cells and potentially enhance antitumor immune responses. Here we report that the combination of anti-PD-L1 antibody and ibrutinib suppresses tumor growth in mouse models of lymphoma that are intrinsically insensitive to ibrutinib. The combined effect of these two agents was also documented for models of solid tumors, such as triple negative breast cancer and colon cancer. The enhanced therapeutic activity of PD-L1 blockade by ibrutinib was accompanied by enhanced antitumor T-cell immune responses. These preclinical results suggest that the combination of PD1/PD1-L blockade and ibrutinib should be tested in the clinic for the therapy not only of lymphoma but also in other hematologic malignancies and solid tumors that do not even express BTK.ibrutinib | PD-1/PD-L1 blockade | lymphoma | solid tumors

It has recently become apparent that the immune system can cure cancer. In some of these strategies the antigen targets are pre-identified and therapies are custom-made against these targets. In others, antibodies are used to remove the brakes of the immune system, allowing pre- existing T cells to attack cancer cells. We have employed another non-customized approach called in situ vaccination. Here, immune enhancing agents are injected locally into one site of tumor, thereby triggering a T cell immune response locally that then attacks cancer throughout the body. We have employed a screening strategy in which the same syngeneic tumor is implanted at two separate sites in the body. One tumor is then injected with the test agents and the resulting immune response is detected by the regression of the distant, untreated tumor. Using this assay the combination of unmethylated CG-enriched oligodeoxynucleotide (CpG) -a TLR9 ligand- and anti-OX40 antibody provided the most impressive results. TLRs are components of the innate immune system that recognize molecular patterns on pathogens. Low doses of CpG injected into a tumor induce the expression of OX40 on CD4+ T cells in the microenvironment in mouse or human tumors. An agonistic anti-OX40 antibody can then trigger a T cell immune response, which is specific to the antigens of the injected tumor. Remarkably, this combination of a TLR ligand and an anti-OX40 antibody can cure multiple types of cancer and prevent spontaneous genetically-driven cancers.

Activation of TLR9 by direct injection of unmethylated CpG nucleotides into a tumor can induce a therapeutic immune response; however, Tregs eventually inhibit the antitumor immune response and thereby limit the power of cancer immunotherapies. In tumor-bearing mice, we found that Tregs within the tumor preferentially express the cell surface markers CTLA-4 and OX40. We show that intratumoral coinjection of anti-CTLA-4 and anti-OX40 together with CpG depleted tumor-infiltrating Tregs. This in situ immunomodulation, which was performed with low doses of antibodies in a single tumor, generated a systemic antitumor immune response that eradicated disseminated disease in mice. Further, this treatment modality was effective against established CNS lymphoma with leptomeningeal metastases, sites that are usually considered to be tumor cell sanctuaries in the context of conventional systemic therapy. These results demonstrate that antitumor immune effectors elicited by local immunomodulation can eradicate tumor cells at distant sites. We propose that, rather than using mAbs to target cancer cells systemically, mAbs could be used to target the tumor infiltrative immune cells locally, thereby eliciting a systemic immune response.

Key Points• Blockade of inhibitory KIRs with MHC class I antigens on lymphoma cells by anti-KIR antibodies augments NK-cell spontaneous cytotoxicity.• In combination with anti-CD20 mAbs, anti-KIR induces enhanced NK cell-mediated, rituximab-dependent cytotoxicity against lymphoma.

. planned the research, performed experiments, analyzed data, drafted the first and subsequent drafts of the letter, and approved the final version of the letter; J.P.B. and C.C. were involved in planning components of the research, performing experiments, reviewed drafts, and approved the final version of the letter; X.Z. was involved in planning components of the research, did all the statistical analysis, reviewed drafts, and approved the final version of the letter; J.J.B. provided input and suggestions to the presentation of the data and a critical reagent (ibrutinib) essential for completion of the work, and reviewed and approved the final version of the letter; N.M. and R.L. provided input into experimental design, reviewed drafts of the manuscript, and approved the final submitted version; and A.J.J. and J.C.B. planned every aspect of the proposal, supervised the research, analyzed data, reviewed drafts, obtained funding for the research work, and approved the final version of the letter.