Natural killer cell depletion confounds the antitumor mechanism of endogenous IL-12 overexpression

SENTI-101, a Preparation of Mesenchymal Stromal Cells Engineered to Express IL12 and IL21, Induces Localized and Durable Antitumor Immunity in Preclinical Models of Peritoneal Solid Tumors

Advanced peritoneal carcinomatosis including high-grade ovarian cancer has poor prognoses and a poor response rate to current checkpoint inhibitor immunotherapies; thus, there is an unmet need for effective therapeutics that would provide benefit to these patients. Here we present the preclinical development of SENTI-101, a cell preparation of bone marrow-derived mesenchymal stromal (also known as stem) cells (MSC), which are engineered to express two potent immune-modulatory cytokines, IL12 and IL21. Intraperitoneal administration of SENTI-101 results in selective tumor-homing and localized and sustained cytokine production in murine models of peritoneal cancer. SENTI-101 has extended half-life, reduced systemic distribution, and improved antitumor activity when compared with recombinant cytokines, suggesting that it is more effective and has lower risk of systemic immunotoxicities. Treatment of tumor-bearing immune-competent mice with a murine surrogate of SENTI-101 (mSENTI-101) results in a potent and localized immune response consistent with increased number and activation of antigen presenting cells, T cells and B cells, which leads to antitumor response and memory-induced long-term immunity. Consistent with this mechanism of action, co-administration of mSENTI-101 with checkpoint inhibitors leads to synergistic improvement in antitumor response. Collectively, these data warrant potential clinical development of SENTI-101 for patients with peritoneal carcinomatosis and high-grade ovarian cancer.Graphical abstract: SENTI-101 schematic and mechanism of actionSENTI-101 is a novel cell-based immunotherapeutic consisting of bone marrow-derived mesenchymal stromal cells (BM-MSC) engineered to express IL12 and IL21 intended for the treatment of peritoneal carcinomatosis including high-grade serous ovarian cancer. Upon intraperitoneal administration, SENTI-101 homes to peritoneal solid tumors and secretes IL12 and IL21 in a localized and sustained fashion. The expression of these two potent cytokines drives tumor infiltration and engagement of multiple components of the immune system: antigen-presenting cells, T cells, and B cells, resulting in durable antitumor immunity in preclinical models of cancer.

Intratumoral but not systemic delivery of CpG oligodeoxynucleotide augments the efficacy of anti-CD20 monoclonal antibody therapy against B cell lymphoma

The anti-CD20 monoclonal antibody rituximab (Rituxan) has become a mainstay in the treatment of B cell non-Hodgkin lymphomas. The mechanisms of action for rituximab include antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity, and apoptosis induction. Combination of anti-CD20 antibodies with immunostimulatory agents may improve their efficacy via enhancement of one or more of these mechanisms. Toll-like receptor 9 agonist CpG oligodeoxynucleotides administered systemically have been studied in clinical trials with and without rituximab. However, recent data suggest that intratumoral (IT) delivery of CpG has advantages in the treatment of tumors. Using a syngeneic murine B cell lymphoma line expressing human CD20, we found that IT, but not systemically administered CpG significantly improved the efficacy of rituximab against 7-day established tumors. Rituximab plus IT CpG could eradicate tumors from 42% of mice, whereas systemically administered CpG, with or without rituximab, did not achieve tumor eradication. Both natural killer cells and complement participated in the cure of tumors by rituximab plus IT CpG, apparently by increasing tumor cell sensitivity to complement and ADCC lysis, and by augmenting the cytotoxicity of ADCC effectors. No role for T cells in mediating tumor eradication was demonstrated in this model. These results suggest that previous clinical trials in B cell lymphoma combining systemic administration of CpG with rituximab may have employed suboptimal routes of CpG delivery. Future trials combining IT CpG with anti-CD20 antibodies or the antibody-mediated targeting of CpG directly to the sites of B cell lymphoma may thus be warranted.

Selective induction of tumor-associated antigens in murine pulmonary vasculature using double-targeted adenoviral vectors

Targeted therapies directed to tumor-associated antigens are being investigated for the treatment of cancer. However, there are few suitable animal models for testing the ability to target these tumor markers. Therefore, we have exploited mice transgenic for the human coxsackie and adenovirus receptor (hCAR) to establish a new model for transient expression of human tumor-associated antigens in the pulmonary vasculature. Systemic administration of Ad in hCAR mice resulted in an increase in transgene expression in the lungs compared to wild-type mice, as determined using a luciferase reporter gene. To reduce transgene expression in the liver, the predominant organ of ectopic Ad localization and transgene expression following systemic administration, we utilized the endothelial-specific flt-1 promoter, which resulted in a further increased lung-to-liver ratio of luciferase expression. Administration of an adenoviral vector encoding the tumor-associated antigen carcinoembryonic antigen (CEA) under transcriptional control of the flt-1 promoter resulted in selective expression of this antigen in the pulmonary vasculature of hCAR mice. Feasibility of targeting to expressed CEA was subsequently demonstrated using adenoviral vectors preincubated with a bifunctional adapter molecule recognizing this tumor-associated antigen, thus demonstrating utility of this transient transgenic animal model.

Activated natural killer cells from patients with acute myeloid leukemia are cytotoxic against autologous leukemic blasts in NOD/SCID mice

Natural killer (NK) cells are implicated in the surveillance of hematological malignancies. They participate in the immune response against residual acute myeloid leukemia (AML) after hematopoietic stem cell transplantation with partial HLA class I disparity. However, the role of NK cells in autologous leukemia-specific immunity remains poorly understood. We studied the function of NK cells in AML patients at diagnosis. Following isolation, CD56+CD3- cells exhibited a high proliferative potential in vitro in response to interleukin (IL)-2. The polyclonal population of activated AML-NK cells expressed normal levels of the activating receptor NKG2D and the major natural cytotoxicity receptor NKp46. AML-NK cells were highly effective with respect to interferon-gamma production, cytotoxicity against HLA class I-deficient K562 erythroleukemia cells in vitro and retardation of tumor growth in vivo in K562-bearing NOD/SCID mice. Importantly, when AML blasts were injected into NOD/SCID mice, a single dose of adoptively transferred autologous AML-NK cells significantly reduced the AML load by 8-77%. Recognition of AML blasts may be related to the observed upregulation of ligands for NKG2D and natural cytotoxicity receptors in vivo. We conclude that AML patient-derived NK cells are fully functional, in support of exploring the benefit of AML immunotherapy with IL-2-stimulated autologous NK cells.