Holbrook Kohrt

Predictive correlates of response to the anti-PD-L1 antibody MPDL3280A in cancer patients

The development of human cancer is a multistep process characterized by the accumulation of genetic and epigenetic alterations that drive or reflect tumour progression. These changes distinguish cancer cells from their normal counterparts, allowing tumours to be recognized as foreign by the immune system. However, tumours are rarely rejected spontaneously, reflecting their ability to maintain an immunosuppressive microenvironment. Programmed death-ligand 1 (PD-L1; also called B7-H1 or CD274), which is expressed on many cancer and immune cells, plays an important part in blocking the ‘cancer immunity cycle’ by binding programmed death-1 (PD-1) and B7.1 (CD80), both of which are negative regulators of T-lymphocyte activation. Binding of PD-L1 to its receptors suppresses T-cell migration, proliferation and secretion of cytotoxic mediators, and restricts tumour cell killing. The PD-L1–PD-1 axis protects the host from overactive T-effector cells not only in cancer but also during microbial infections. Blocking PD-L1 should therefore enhance anticancer immunity, but little is known about predictive factors of efficacy. This study was designed to evaluate the safety, activity and biomarkers of PD-L1 inhibition using the engineered humanized antibody MPDL3280A. Here we show that across multiple cancer types, responses (as evaluated by Response Evaluation Criteria in Solid Tumours, version 1.1) were observed in patients with tumours expressing high levels of PD-L1, especially when PD-L1 was expressed by tumour-infiltrating immune cells. Furthermore, responses were associated with T-helper type 1 (TH1) gene expression, CTLA4 expression and the absence of fractalkine (CX3CL1) in baseline tumour specimens. Together, these data suggest that MPDL3280A is most effective in patients in which pre-existing immunity is suppressed by PD-L1, and is re-invigorated on antibody treatment.

Anti-CD47 Antibody Synergizes with Rituximab to Promote Phagocytosis and Eradicate Non-Hodgkin Lymphoma

Monoclonal antibodies are standard therapeutics for several cancers including the anti-CD20 antibody rituximab for B cell non-Hodgkin lymphoma (NHL). Rituximab and other antibodies are not curative and must be combined with cytotoxic chemotherapy for clinical benefit. Here we report the eradication of human NHL solely with a monoclonal antibody therapy combining rituximab with a blocking anti-CD47 antibody. We identified increased expression of CD47 on human NHL cells and determined that higher CD47 expression independently predicted adverse clinical outcomes in multiple NHL subtypes. Blocking anti-CD47 antibodies preferentially enabled phagocytosis of NHL cells and synergized with rituximab. Treatment of human NHL-engrafted mice with anti-CD47 antibody reduced lymphoma burden and improved survival, while combination treatment with rituximab led to elimination of lymphoma and cure. These antibodies synergized through a mechanism combining Fc receptor (FcR)-dependent and FcR-independent stimulation of phagocytosis that might be applicable to many other cancers.

PD-1 Blockade with Pembrolizumab in Advanced Merkel-Cell Carcinoma

BACKGROUND Merkel-cell carcinoma is an aggressive skin cancer that is linked to exposure to ultraviolet light and the Merkel-cell polyomavirus (MCPyV). Advanced Merkel-cell carcinoma often responds to chemotherapy, but responses are transient. Blocking the programmed death 1 (PD-1) immune inhibitory pathway is of interest, because these tumors often express PD-L1, and MCPyV-specific T cells express PD-1. METHODS In this multicenter, phase 2, noncontrolled study, we assigned adults with advanced Merkel-cell carcinoma who had received no previous systemic therapy to receive pembrolizumab (anti-PD-1) at a dose of 2 mg per kilogram of body weight every 3 weeks. The primary end point was the objective response rate according to Response Evaluation Criteria in Solid Tumors, version 1.1. Efficacy was correlated with tumor viral status, as assessed by serologic and immunohistochemical testing. RESULTS A total of 26 patients received at least one dose of pembrolizumab. The objective response rate among the 25 patients with at least one evaluation during treatment was 56% (95% confidence interval [CI], 35 to 76); 4 patients had a complete response, and 10 had a partial response. With a median follow-up of 33 weeks (range, 7 to 53), relapses occurred in 2 of the 14 patients who had had a response (14%). The response duration ranged from at least 2.2 months to at least 9.7 months. The rate of progression-free survival at 6 months was 67% (95% CI, 49 to 86). A total of 17 of the 26 patients (65%) had virus-positive tumors. The response rate was 62% among patients with MCPyV-positive tumors (10 of 16 patients) and 44% among those with virus-negative tumors (4 of 9 patients). Drug-related grade 3 or 4 adverse events occurred in 15% of the patients. CONCLUSIONS In this study, first-line therapy with pembrolizumab in patients with advanced Merkel-cell carcinoma was associated with an objective response rate of 56%. Responses were observed in patients with virus-positive tumors and those with virus-negative tumors. (Funded by the National Cancer Institute and Merck; ClinicalTrials.gov number, NCT02267603.).

New models and online calculator for predicting non-sentinel lymph node status in sentinel lymph node positive breast cancer patients

BackgroundCurrent practice is to perform a completion axillary lymph node dissection (ALND) for breast cancer patients with tumor-involved sentinel lymph nodes (SLNs), although fewer than half will have non-sentinel node (NSLN) metastasis. Our goal was to develop new models to quantify the risk of NSLN metastasis in SLN-positive patients and to compare predictive capabilities to another widely used model.MethodsWe constructed three models to predict NSLN status: recursive partitioning with receiver operating characteristic curves (RP-ROC), boosted Classification and Regression Trees (CART), and multivariate logistic regression (MLR) informed by CART. Data were compiled from a multicenter Northern California and Oregon database of 784 patients who prospectively underwent SLN biopsy and completion ALND. We compared the predictive abilities of our best model and the Memorial Sloan-Kettering Breast Cancer Nomogram (Nomogram) in our dataset and an independent dataset from Northwestern University.Results285 patients had positive SLNs, of which 213 had known angiolymphatic invasion status and 171 had complete pathologic data including hormone receptor status. 264 (93%) patients had limited SLN disease (micrometastasis, 70%, or isolated tumor cells, 23%). 101 (35%) of all SLN-positive patients had tumor-involved NSLNs. Three variables (tumor size, angiolymphatic invasion, and SLN metastasis size) predicted risk in all our models. RP-ROC and boosted CART stratified patients into four risk levels. MLR informed by CART was most accurate. Using two composite predictors calculated from three variables, MLR informed by CART was more accurate than the Nomogram computed using eight predictors. In our dataset, area under ROC curve (AUC) was 0.83/0.85 for MLR (n = 213/n = 171) and 0.77 for Nomogram (n = 171). When applied to an independent dataset (n = 77), AUC was 0.74 for our model and 0.62 for Nomogram. The composite predictors in our model were the product of angiolymphatic invasion and size of SLN metastasis, and the product of tumor size and square of SLN metastasis size.ConclusionWe present a new model developed from a community-based SLN database that uses only three rather than eight variables to achieve higher accuracy than the Nomogram for predicting NSLN status in two different datasets.

Depleting tumor-specific Tregs at a single site eradicates disseminated tumors.

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.

Stimulation of natural killer cells with a CD137-specific antibody enhances trastuzumab efficacy in xenotransplant models of breast cancer

Trastuzumab, a monoclonal antibody targeting human epidermal growth factor receptor 2 (HER2; also known as HER-2/neu), is indicated for the treatment of women with either early stage or metastatic HER2(+) breast cancer. It kills tumor cells by several mechanisms, including antibody-dependent cellular cytotoxicity (ADCC). Strategies that enhance the activity of ADCC effectors, including NK cells, may improve the efficacy of trastuzumab. Here, we have shown that upon encountering trastuzumab-coated, HER2-overexpressing breast cancer cells, human NK cells become activated and express the costimulatory receptor CD137. CD137 activation, which was dependent on NK cell expression of the FcγRIII receptor, occurred both in vitro and in the peripheral blood of women with HER2-expressing breast cancer after trastuzumab treatment. Stimulation of trastuzumab-activated human NK cells with an agonistic mAb specific for CD137 killed breast cancer cells (including an intrinsically trastuzumab-resistant cell line) more efficiently both in vitro and in vivo in xenotransplant models of human breast cancer, including one using a human primary breast tumor. The enhanced cytotoxicity was restricted to antibody-coated tumor cells. This sequential antibody strategy, combining a tumor-targeting antibody with a second antibody that activates the host innate immune system, may improve the therapeutic effects of antibodies against breast cancer and other HER2-expressing tumors.

CD137 stimulation enhances the antilymphoma activity of anti-CD20 antibodies

Antibody-dependent cell-mediated cytotoxicity (ADCC), which is largely mediated by natural killer (NK) cells, is thought to play an important role in the efficacy of rituximab, an anti-CD20 monoclonal antibody (mAb) used to treat patients with B-cell lymphomas. CD137 is a costimulatory molecule expressed on a variety of immune cells after activation, including NK cells. In the present study, we show that an anti-CD137 agonistic mAb enhances the antilymphoma activity of rituximab by enhancing ADCC. Human NK cells up-regulate CD137 after encountering rituximab-coated tumor B cells, and subsequent stimulation of these NK cells with anti-CD137 mAb enhances rituximab-dependent cytotoxicity against the lymphoma cells. In a syngeneic murine lymphoma model and in a xenotransplanted human lymphoma model, sequential administration of anti-CD20 mAb followed by anti-CD137 mAb had potent antilymphoma activity in vivo. These results support a novel, sequential antibody approach against B-cell malignancies by targeting first the tumor and then the host immune system.

Profile of immune cells in axillary lymph nodes predicts disease-free survival in breast cancer.

Background While lymph node metastasis is among the strongest predictors of disease-free and overall survival for patients with breast cancer, the immunological nature of tumor-draining lymph nodes is often ignored, and may provide additional prognostic information on clinical outcome. Methods and Findings We performed immunohistochemical analysis of 47 sentinel and 104 axillary (nonsentinel) nodes from 77 breast cancer patients with 5 y of follow-up to determine if alterations in CD4, CD8, and CD1a cell populations predict nodal metastasis or disease-free survival. Sentinel and axillary node CD4 and CD8 T cells were decreased in breast cancer patients compared to control nodes. CD1a dendritic cells were also diminished in sentinel and tumor-involved axillary nodes, but increased in tumor-free axillary nodes. Axillary node, but not sentinel node, CD4 T cell and dendritic cell populations were highly correlated with disease-free survival, independent of axillary metastasis. Immune profiling of ALN from a test set of 48 patients, applying CD4 T cell and CD1a dendritic cell population thresholds of CD4 ≥ 7.0% and CD1a ≥ 0.6%, determined from analysis of a learning set of 29 patients, provided significant risk stratification into favorable and unfavorable prognostic groups superior to clinicopathologic characteristics including tumor size, extent or size of nodal metastasis (CD4, p < 0.001 and CD1a, p < 0.001). Moreover, axillary node CD4 T cell and CD1a dendritic cell populations allowed more significant stratification of disease-free survival of patients with T1 (primary tumor size 2 cm or less) and T2 (5 cm or larger) tumors than all other patient characteristics. Finally, sentinel node immune profiles correlated primarily with the presence of infiltrating tumor cells, while axillary node immune profiles appeared largely independent of nodal metastases, raising the possibility that, within axillary lymph nodes, immune profile changes and nodal metastases represent independent processes. Conclusion These findings demonstrate that the immune profile of tumor-draining lymph nodes is of novel biologic and clinical importance for patients with early stage breast cancer.

TLI and ATG conditioning with low risk of graft-versus-host disease retains antitumor reactions after allogeneic hematopoietic cell transplantation from related and unrelated donors

A hematopoietic cell transplantation regimen was adapted from a preclinical model that used reduced-intensity conditioning (RIC) and protected against graft-versus-host disease (GVHD) by skewing residual host T-cell subsets to favor regulatory natural killer T cells. One hundred eleven patients with lymphoid (64) and myeloid (47) malignancies received RIC using total lymphoid irradiation (TLI) and antithymocyte globulin (ATG) followed by the infusion of granulocyte colony-stimulating factor-mobilized grafts. Included were 34 patients at least 60 years of age, 32 patients at high risk of lymphoma relapse after disease recurrence following prior autologous transplantation, and 51 patients at high risk of developing GVHD due to lack of a fully human leukocyte antigen (HLA)-matched related donor. Durable chimerism was achieved in 97% of patients. Cumulative probabilities of acute GVHD (grades II-IV) were 2 and 10% of patients receiving related and unrelated donor grafts. Nonrelapse mortality (NRM) at 1 year was less than 4%. Cumulative incidence of chronic GVHD was 27%. The 36-month probability of overall and event-free survival was 60% and 40%, respectively. Disease status at start of conditioning and the level of chimerism achieved after transplantation significantly impacted clinical outcome. The high incidence of sustained remission among patients with active disease at time of transplantation suggests retained graft-versus-tumor reactions. Active trial registration currently at clinicaltrials.gov under IDs of NCT00185640 and NCT00186615.

Therapeutic antitumor immunity by checkpoint blockade is enhanced by ibrutinib, an inhibitor of both BTK and ITK

Significance Antibodies that block the negative signals between PD1-Ligand on tumor cells and PD-1 on T cells are effective therapies against several types of cancer. Ibrutinib, a covalent inhibitor of BTK is an approved therapy for B-cell leukemia and lymphoma. But ibrutinib also inactivates ITK, an enzyme required for certain subsets of T lymphocytes (Th2 T cells). We found that the combination of anti–PD-L1 antibodies and ibrutinib led to impressive therapeutic effects not only in animal models of lymphoma but, surprisingly, also in models of breast cancer and colon cancer. Based on these preclinical results, we suggest that the combination of PD-1/PD-L1 blockade and ibrutinib be tested broadly in patients with lymphoma and also in other hematologic malignancies and solid tumors. 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.