mDKN-01, a Novel Anti-DKK1 mAb, Enhances Innate Immune Responses in the Tumor Microenvironment.

Dickkopf-1 (DKK1), a secreted modulator of Wnt signaling, is overexpressed in many cancers, is often associated with worse clinical outcomes, and has been shown to have immunosuppressive effects. DKN-01 is an IgG4 clinical stage antibody that potently and specifically neutralizes human and murine DKK1 and has recently completed a promising study in combination with pembrolizumab in patients with gastric/gastroesophageal junction cancer. The purpose of this study is to characterize a murine version of DKN-01 (mDKN-01) and to better understand its mechanism of action. We examined the efficacy of mDKN-01 in both melanoma and metastatic breast cancer models. Immune depletion experiments revealed a requirement for natural killer (NK) but not B and T cells for tumor growth inhibition. mDKN-01 treatment promotes the induction of the NK-activating cytokines IL15 and IL33 as well as an enhanced recruitment of CD45+ cells. Other treatment-related changes include a reduction of Gr-1+CD11b+ myeloid-derived suppressor cells (MDSC) in the tumor and spleen and the upregulation of PD-L1 on MDSCs. In addition, mDKN-01 has a marked effect at reducing pulmonary metastases in the mouse 4T1 breast cancer model. Finally, the mDKN-01/anti-PD-1 combination was more effective at inhibiting melanoma growth than mDKN-01 alone. Taken together, our data demonstrate that mDKN-01 has efficacy by blocking the immunosuppressive effects of DKK1 in the tumor microenvironment (TME) and provides insight into the clinical activity observed with DKN-01-based treatment. IMPLICATIONS: mDKN-01 reverses a DKK1-mediated innate immune suppression in the TME and has additive efficacy with a PD-1 inhibitor.

Natural IgM Blockade Limits Infarct Expansion and Left Ventricular Dysfunction in a Swine Myocardial Infarct Model.

BACKGROUND: Acute coronary syndrome is the leading cause of mortality worldwide. However, treatment of acute coronary occlusion inevitably results in ischemia-reperfusion injury. Circulating natural IgM has been shown to play a significant role in mouse models of ischemia-reperfusion injury. A highly conserved self-antigen, nonmuscle myosin heavy chain II, has been identified as a target of pathogenic IgM. We hypothesized that a monoclonal antibody (m21G6) directed against nonmuscle myosin heavy chain II may inhibit IgM binding and reduce injury in a preclinical model of myocardial infarction. Thus, our objective was to evaluate the efficacy of intravenous m21G6 treatment in limiting infarct expansion, troponin release, and left ventricular dysfunction in a swine myocardial infarction model. METHODS AND RESULTS: Massachusetts General Hospital miniature swine underwent occlusion of the midleft anterior descending coronary artery for 60 minutes, followed by 1 hour, 5-day, or 21-day reperfusion. Specificity and localization of m21G6 to injured myocardium were confirmed using fluorescently labeled m21G6. Treatment with m21G6 before reperfusion resulted in a 49% reduction in infarct size (P<0.005) and a 61% reduction in troponin-T levels (P<0.05) in comparison with saline controls at 5-day reperfusion. Furthermore, m21G6-treated animals recovered 85.4% of their baseline left ventricular function as measured by 2-dimensional transthoracic echocardiography in contrast to 67.1% in controls at 21-day reperfusion (P<0.05). CONCLUSIONS: Treatment with m21G6 significantly reduced infarct size and troponin-T release, and led to marked preservation of cardiac function in our study. Overall, these findings suggest that pathogenic IgM blockade represents a valid therapeutic strategy in mitigating myocardial ischemia-reperfusion injury.

Blockade of self-reactive IgM significantly reduces injury in a murine model of acute myocardial infarction.

AIMS: Coronary artery occlusion resulting in ischaemia/reperfusion (I/R) injury is a major cause of mortality in the western world. Circulating natural IgM has been shown to play a significant role in reperfusion injury, leading to the notion of a pathogenic response against self by the innate immune system. A specific self-antigen (non-muscle myosin heavy chain II) was recently identified as the major target of pathogenic natural IgM. Therefore, we hypothesized that a synthetic peptide mimetope (N2) or monoclonal antibodies directed against the self-antigen would prevent specific IgM binding to the self-antigen and reduce reperfusion injury in the heart. METHODS AND RESULTS: We find that treatment with N2 peptide reduces infarct size by 47% and serum cardiac troponin-I levels by 69% following 1 h ischaemia and 24 h reperfusion. N2 peptide or an anti-N2 F(ab')(2) (21G6) is also effective at preventing IgM and complement deposition. Additionally, N2 peptide treatment significantly reduces monocyte and neutrophil infiltration at 24 h and collagen deposition at 5 days. Finally, we show that human IgM (hIgM) also includes specificity for the highly conserved self-antigen and that myocardial injury in antibody-deficient mice reconstituted with hIgM is blocked by treatment with N2 peptide or 21G6 F(ab')(2). CONCLUSION: The findings in this study identify potential therapeutics [i.e. N2 peptide or 21G6 F(ab')(2)] that prevent specific IgM binding to ischaemic antigens in the heart, resulting in a significant reduction in cardiac I/R injury.

B cell acquisition of antigen in vivo.

The fate of B lymphocytes is dictated in large part by cognate antigen and the environment in which it is encountered. Yet we are only now beginning to understand where and how B cells acquire antigen. Recent studies identify multiple pathways by which lymph-borne antigens enter the B cell follicles of LNs. Size is a major factor as particulate antigens and large IC are bound by subcapsular sinus macrophages. By contrast, small antigens (under 70kDa) are rapidly channeled into follicles via conduits secreted by fibroblastic reticular cells (FRC). Interestingly, the conduits not only deliver antigen to follicular dendritic cells (FDC) but also provide a rich source of B cell chemokine, that is, CXCL-13. Thus, the follicular conduits provide an 'antigen highway' for B cells trafficking within the LN. These new findings provide an important discovery in understanding how B cells acquire cognate antigen.