Crystal structures of CDC21-1 inteins from hyperthermophilic archaea reveal the selection mechanism for the highly conserved homing endonuclease insertion site

Self-splicing inteins are mobile genetic elements invading host genes via nested homing endonuclease (HEN) domains. All HEN domains residing within inteins are inserted at a highly conserved insertion site. A purifying selection mechanism directing the location of the HEN insertion site has not yet been identified. In this work, we solved the three-dimensional crystal structures of two inteins inserted in the cell division control protein 21 of the hyperthermophilic archaea Pyrococcus abyssi and Pyrococcus horikoshii. A comparison between the structures provides the structural basis for the thermo-stabilization mechanism of inteins that have lost the HEN domain during evolution. The presence of an entire extein domain in the intein structure from Pyrococcus horikoshii suggests the selection mechanism for the highly conserved HEN insertion point.Peer reviewe

Effective Combination Immunotherapy with Oncolytic Adenovirus and Anti-PD-1 for Treatment of Human and Murine Ovarian Cancers

Ovarian cancer (OvCa) is one of the most common gynecological cancers and has the highest mortality in this category. Tumors are often detected late, and unfortunately over 70% of OvCa patients experience relapse after first-line treatments. OvCa has shown low response rates to immune checkpoint inhibitor (ICI) treatments, thus leaving room for improvement. We have shown that oncolytic adenoviral therapy with Ad5/3-E2F-d24-hTNFa-IRES-hIL2 (aka. TILT-123) is promising for single-agent treatment of cancer, but also for sensitizing tumors for T-cell dependent immunotherapy approaches, such as ICI treatments. Therefore, this study set out to determine the effect of inhibition of the immune checkpoint inhibitors (ICI), in the context of TILT-123 therapy of OvCa. We show that simultaneous treatment of patient derived samples with TILT-123 and ICIs anti-PD-1 or anti-PD-L1 efficiently reduced overall viability. The combinations induced T cell activation, T cells expressed activation markers more often, and the treatment caused positive microenvironment changes, measured by flow cytometric assays. Furthermore, in an immunocompetent in vivo C57BL/6NHsda mouse model, tumor growth was hindered, when treated with TILT-123, ICI or both. Taken together, this study provides a rationale for using TILT-123 virotherapy in combination with TILT-123 and immune checkpoint inhibitors together in an ovarian cancer OvCa clinical trial.Peer reviewe

Effective Combination Immunotherapy with Oncolytic Adenovirus and Anti-PD-1 for Treatment of Human and Murine Ovarian Cancers

Ovarian cancer (OvCa) is one of the most common gynecological cancers and has the highest mortality in this category. Tumors are often detected late, and unfortunately over 70% of OvCa patients experience relapse after first-line treatments. OvCa has shown low response rates to immune checkpoint inhibitor (ICI) treatments, thus leaving room for improvement. We have shown that oncolytic adenoviral therapy with Ad5/3-E2F-d24-hTNFa-IRES-hIL2 (aka. TILT-123) is promising for single-agent treatment of cancer, but also for sensitizing tumors for T-cell dependent immunotherapy approaches, such as ICI treatments. Therefore, this study set out to determine the effect of inhibition of the immune checkpoint inhibitors (ICI), in the context of TILT-123 therapy of OvCa. We show that simultaneous treatment of patient derived samples with TILT-123 and ICIs anti-PD-1 or anti-PD-L1 efficiently reduced overall viability. The combinations induced T cell activation, T cells expressed activation markers more often, and the treatment caused positive microenvironment changes, measured by flow cytometric assays. Furthermore, in an immunocompetent in vivo C57BL/6NHsda mouse model, tumor growth was hindered, when treated with TILT-123, ICI or both. Taken together, this study provides a rationale for using TILT-123 virotherapy in combination with TILT-123 and immune checkpoint inhibitors together in an ovarian cancer OvCa clinical trial.Peer reviewe

Ad5/3 is able to avoid neutralization by binding to erythrocytes and lymphocytes

Oncolytic adenoviruses are promising cancer therapeutic agents. Clinical data have shown adenoviruses' ability to transduce tumors after systemic delivery in human cancer patients, despite antibodies. In the present work, we have focused on the interaction of a chimeric adenovirus Ad5/3 with human lymphocytes and human erythrocytes. Ad5/3 binding with human lymphocytes and erythrocytes was observed to occur in a reversible manner, which allowed viral transduction of tumors, and oncolytic potency of Ad5/3 in vitro and in vivo,with or without neutralizing antibodies. Immunodeficient mice bearing xenograft tumors showed enhanced tumor transduction following systemic administration, when Ad5/3 virus was bound to lymphocytes or erythrocytes (P <0.05). In conclusion, our findings reveal that chimeric Ad5/3 adenovirus reaches non-injected tumors in the presence of neutralizing antibodies: it occurs through reversible binding to lymphocytes and erythrocytes.Peer reviewe

Local therapy with an engineered oncolytic adenovirus enables antitumor response in non- injected melanoma tumors in mice treated with aPD-1

Intratumoral immunotherapies are entering clinical use but concerns remain regarding their effects on non-injected tumors. Here, we studied the impact of local treatment with an adenovirus coding for TNFa and IL-2 on systemic antitumor response in animals receiving aPD-1 (anti-programmed cell death protein 1) therapy. Using bilateral murine melanoma models, we tested systemic tumor response to combined therapy with anti-PD-1 and an adenovirus coding for TNFa and IL-2 ("virus"). Virus was given intratumorally (to one of the two tumors only) and aPD-1 monoclonal antibody systemically. We evaluated both tumors' response to treatment, overall survival, metastasis development, and immunological mechanisms involved with response. Consistent tumor control was observed in both injected and non-injected tumors, including complete response in all treated animals receiving aPD-1+ virus therapy. Mechanistically, virus injections enabled potent effector lymphocyte response locally, with systemic effects in non-injected tumors facilitated by aPD-1 treatment. Moreover, adenovirus therapy demonstrated immunological memory formation. Virus therapy was effective in preventing metastasis development. Local treatment with TNFa and IL-2 coding adenovirus enhanced systemic response to aPD-1 therapy, by re-shaping the microenvironment of both injected and non-injected tumors. Therefore, our pre-clinical data support the rationale for a trial utilizing a combination of aPD-1 plus virus for the treatment of human cancer.Peer reviewe

Adenovirus Encoding Tumor Necrosis Factor Alpha and Interleukin 2 Induces a Tertiary Lymphoid Structure Signature in Immune Checkpoint Inhibitor Refractory Head and Neck Cancer

Immune checkpoint inhibitors (ICI) have provided significant improvement in clinical outcomes for some patients with solid tumors. However, for patients with head and neck cancer, the response rate to ICI monotherapy remains low, leading to the exploration of combinatorial treatment strategies. In this preclinical study, we use an oncolytic adenovirus (Ad5/3) encoding hTNF alpha and hIL-2 and non-replicate adenoviruses (Ad5) encoding mTNF alpha and mIL-2 with ICI to achieve superior tumor growth control and improved survival outcomes. The in vitro effect of Ad5/3-E2F-D24-hTNFa-IRES-hIL-2 was characterized through analyses of virus replication, transgene expression and lytic activity using head and neck cancer patient derived cell lines. Mouse models of ICI naive and refractory oral cavity squamous cell carcinoma were established to evaluate the local and systemic anti-tumor immune response upon ICI treatment with or without the non-replicative adenovirus encoding mTNF alpha and mIL-2. We delineated the mechanism of action by measuring the metabolic activity and effector function of CD3(+) tumor infiltrating lymphocytes (TIL) and transcriptomic profile of the CD45(+) tumor immune compartment. Ad5/3-E2F-D24-hTNFa-IRES-hIL-2 demonstrated robust replicative capability in vitro across all head and neck cell lines screened through potent lytic activity, E1a and transgene expression. In vivo, in both ICI naive and refractory models, we observed improvement to tumor growth control and long-term survival when combining anti-PD-1 or anti-PD-L1 with the non-replicative adenovirus encoding mTNF alpha and mIL-2 compared to monotherapies. This observation was verified by striking CD3(+) TIL derived mGranzyme b and interferon gamma production complemented by increased T cell bioenergetics. Notably, interrogation of the tumor immune transcriptome revealed the upregulation of a gene signature distinctive of tertiary lymphoid structure formation upon treatment of murine anti-PD-L1 refractory tumors with non-replicative adenovirus encoding mTNF alpha and mIL-2. In addition, we detected an increase in anti-tumor antibody production and expansion of the memory T cell compartment in the secondary lymphoid organs. In summary, a non-replicative adenovirus encoding mTNF alpha and mIL-2 potentiates ICI therapy, demonstrated by improved tumor growth control and survival in head and neck tumor-bearing mice. Moreover, the data reveals a potential approach for inducing tertiary lymphoid structure formation. Altogether our results support the clinical potential of combining this adenovirotherapy with anti-PD-1 or anti-PD-L1.Peer reviewe

Adenovirus Encoding Tumor Necrosis Factor Alpha and Interleukin 2 Induces a Tertiary Lymphoid Structure Signature in Immune Checkpoint Inhibitor Refractory Head and Neck Cancer

Immune checkpoint inhibitors (ICI) have provided significant improvement in clinical outcomes for some patients with solid tumors. However, for patients with head and neck cancer, the response rate to ICI monotherapy remains low, leading to the exploration of combinatorial treatment strategies. In this preclinical study, we use an oncolytic adenovirus (Ad5/3) encoding hTNF alpha and hIL-2 and non-replicate adenoviruses (Ad5) encoding mTNF alpha and mIL-2 with ICI to achieve superior tumor growth control and improved survival outcomes. The in vitro effect of Ad5/3-E2F-D24-hTNFa-IRES-hIL-2 was characterized through analyses of virus replication, transgene expression and lytic activity using head and neck cancer patient derived cell lines. Mouse models of ICI naive and refractory oral cavity squamous cell carcinoma were established to evaluate the local and systemic anti-tumor immune response upon ICI treatment with or without the non-replicative adenovirus encoding mTNF alpha and mIL-2. We delineated the mechanism of action by measuring the metabolic activity and effector function of CD3(+) tumor infiltrating lymphocytes (TIL) and transcriptomic profile of the CD45(+) tumor immune compartment. Ad5/3-E2F-D24-hTNFa-IRES-hIL-2 demonstrated robust replicative capability in vitro across all head and neck cell lines screened through potent lytic activity, E1a and transgene expression. In vivo, in both ICI naive and refractory models, we observed improvement to tumor growth control and long-term survival when combining anti-PD-1 or anti-PD-L1 with the non-replicative adenovirus encoding mTNF alpha and mIL-2 compared to monotherapies. This observation was verified by striking CD3(+) TIL derived mGranzyme b and interferon gamma production complemented by increased T cell bioenergetics. Notably, interrogation of the tumor immune transcriptome revealed the upregulation of a gene signature distinctive of tertiary lymphoid structure formation upon treatment of murine anti-PD-L1 refractory tumors with non-replicative adenovirus encoding mTNF alpha and mIL-2. In addition, we detected an increase in anti-tumor antibody production and expansion of the memory T cell compartment in the secondary lymphoid organs. In summary, a non-replicative adenovirus encoding mTNF alpha and mIL-2 potentiates ICI therapy, demonstrated by improved tumor growth control and survival in head and neck tumor-bearing mice. Moreover, the data reveals a potential approach for inducing tertiary lymphoid structure formation. Altogether our results support the clinical potential of combining this adenovirotherapy with anti-PD-1 or anti-PD-L1.Peer reviewe

Local delivery of interleukin 7 with an oncolytic adenovirus activates tumor-infiltrating lymphocytes and causes tumor regression

Cytokines have proven to be effective for cancer therapy, however whilst low-dose monotherapy with cytokines provides limited therapeutic benefit, high-dose treatment can lead to a number of adverse events. Interleukin 7 has shown promising results in clinical trials, but anti-cancer effect was limited, in part due to a low concentration of the cytokine within the tumor. We hypothesized that arming an oncolytic adenovirus with Interleukin 7, enabling high expression localized to the tumor microenvironment, would overcome systemic delivery issues and improve therapeutic efficacy. We evaluated the effects of Ad5/3-E2F-d24-hIL7 (TILT-517) on tumor growth, immune cell activation and cytokine profiles in the tumor microenvironment using three clinically relevant animal models and ex vivo tumor cultures. Our data showed that local treatment of tumor bearing animals with Ad5/3- E2F-d24-hIL7 significantly decreased cancer growth and increased frequency of tumor-infiltrating cells. Ad5/3-E2F-d24-hIL7 promoted notable upregulation of pro-inflammatory cytokines, and concomitant activation and migration of CD4+ and CD8 + T cells. Interleukin 7 expression within the tumor was positively correlated with increased number of cytotoxic CD4+ cells and IFNg-producing CD4+ and CD8+ cells. These findings offer an approach to overcome the current limitations of conventional IL7 therapy and could therefore be translated to the clinic.Peer reviewe

An oncolytic adenovirus coding for a variant interleukin 2 cytokine improves response to chemotherapy through enhancement of effector lymphocyte cytotoxicity, fibroblast compartment modulation and mitotic slippage

Pancreatic ductal adenocarcinoma (PDAC) is a highly treatment-resistant cancer. Currently, the only curative treatment for PDAC is surgery, but most patients are diagnosed with metastatic disease and thus outside the scope of surgery. The majority of metastatic patients receive chemotherapy, but responses are limited. New therapeutics are thus urgently needed for PDAC. One major limitation in treating PDAC has been the highly immunosuppressive tumor microenvironment (TME) which inhibits anti-cancer immune responses. We have constructed an oncolytic adenovirus coding for a variant the interleukin 2 molecule, Ad5/3-E2F-d24-vIL2 (also known as TILT-452, and “vIL-2 virus”), with preferential binding to IL-2 receptors on the surface of effector lymphocytes over T regulatory cells (T regs). In the present study this virus was evaluated in combination with nab-paclitaxel and gemcitabine chemotherapy in Panc02 mouse model. Ad5/3-E2F-d24-vIL2 showed marked PDAC cell killing in vitro, alongside induction of mitotic slippage and immunogenic cell death in PDAC cell lines, when combined with chemotherapy. Increased survival was seen in vivo with 80% of animals surviving long term, when compared to chemotherapy alone. Moreover, combination therapy mediated enhanced tumor growth control, without observable toxicities in internal organs or external features. Survival and tumor control benefits were associated with activation of tumor infiltrating immune cells, downregulation of inhibitory signals, change in fibroblast populations in the tumors and changes in intratumoral cytokines, with increased chemokine amounts (CCL2, CCL3, CCL4) and anti-tumor cytokines (IFN-γ and TNFα). Furthermore, vIL-2 virus in combination with chemotherapy efficiently induced tumor protection upon rechallenge, that was extended to a previously non-encountered cancer cell line. In conclusion, Ad5/3-E2F-d24-vIL2 is a promising immunotherapy candidate when combined with nab-paclitaxel and gemcitabine

Oncolytic Adenovirus Coding for a Variant Interleukin 2 (vIL-2) Cytokine Re-Programs the Tumor Microenvironment and Confers Enhanced Tumor Control

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