Electrochemotherapy Plus IL-2+IL-12 Gene Electrotransfer in Spontaneous Inoperable Stage III-IV Canine Oral Malignant Melanoma

Electrochemotherapy (ECT) is a standard of care in veterinary and human oncology. The treatment induces a well-characterized local immune response which is not able to induce a systemic response. In this retrospective cohort study, we evaluated the addition of gene electrotransfer (GET) of canine IL-2 peritumorally and IL-12 intramuscularly to enhance the immune response. Thirty canine patients with inoperable oral malignant melanoma were included. Ten patients received ECT+GET as the treatment group, while twenty patients received ECT as the control group. Intravenous bleomycin for the ECT was used in both groups. All patients had compromised lymph nodes which were surgically removed. Plasma levels of interleukins, local response rate, overall survival, and progression-free survival were evaluated. The results show that IL-2 and IL-12 expression peaked around days 7-14 after transfection. Both groups showed similar local response rates and overall survival times. However, progression-free survival resulted significantly better in the ECT+GET group, which is a better indicator than overall survival, as it is not influenced by the criterion used for performing euthanasia. We can conclude that the combination of ECT+GET using IL-2 and IL-12 improves treatment outcomes by slowing down tumoral progression in stage III-IV inoperable canine oral malignant melanoma.

Evolution of Toll-like receptor 7/8 agonist therapeutics and their delivery approaches: From antiviral formulations to vaccine adjuvants

Imidazoquinoline derivatives (IMDs) and related compounds function as synthetic agonists of Toll-like receptors 7 and 8 (TLR7/8) and one is FDA approved for topical antiviral and skin cancer treatments. Nevertheless, these innate immune system-activating drugs have potentially much broader therapeutic utility; they have been pursued as antitumor immunomodulatory agents and more recently as candidate vaccine adjuvants for cancer and infectious disease. The broad expression profiles of TLR7/8, poor pharmacokinetic properties of IMDs, and toxicities associated with systemic administration, however, are formidable barriers to successful clinical translation. Herein, we review IMD formulations that have advanced to the clinic and discuss issues related to biodistribution and toxicity that have hampered the further development of these compounds. Recent strategies aimed at enhancing safety and efficacy, particularly through the use of bioconjugates and nanoparticle formulations that alter pharmacokinetics, biodistribution, and cellular targeting, are described. Finally, key aspects of the biology of TLR7 signaling, such as TLR7 tolerance, that may need to be considered in the development of new IMD therapeutics are discussed.

Potentiation of electrochemotherapy effectiveness by immunostimulation with IL-12 gene electrotransfer in mice is dependent on tumor immune status

Electrochemotherapy (ECT) exhibits high therapeutic effectiveness in the clinic, achieving up to 80% local tumor control but without a systemic (abscopal) effect. Therefore, we designed a combination therapy consisting of ECT via intratumoral application of bleomycin, oxaliplatin or cisplatin with peritumoral gene electrotransfer of a plasmid encoding interleukin-12 (p. t. IL-12 GET). Our hypothesis was that p. t. IL-12 GET potentiates the effect of ECT on local and systemic levels and that the potentiation varies depending on tumor immune status. Therefore, the combination therapy was tested in three immunologically different murine tumor models. In poorly immunogenic B16F10 melanoma, IL-12 potentiated the antitumor effect of ECT with biologically equivalent low doses of cisplatin, oxaliplatin or bleomycin. The most pronounced potentiation was observed after ECT using cisplatin, resulting in a complete response rate of 38% and an abscopal effect. Compared to B16F10 melanoma, better responsiveness to ECT was observed in more immunogenic 4 T1 mammary carcinoma and CT26 colorectal carcinoma. In both models, p. t. IL-12 GET did not significantly improve the therapeutic outcome of ECT using any of the chemotherapeutic drugs. Collectively, the effectiveness of the combination therapy depends on tumor immune status. ECT was more effective in more immunogenic tumors, but GET exhibited greater contribution in less immunogenic tumors. Thus, the selection of the therapy, namely, either ECT alone or combination therapy with p. t. IL-12, should be predominantly based on tumor immune status.

Tumor-Associated Macrophage and Tumor-Cell Dually Transfecting Polyplexes for Efficient Interleukin-12 Cancer Gene Therapy

Interleukin 12 (IL12) is a potent pro-inflammatory chemokine with multifunction, including promoting cytotoxic T-cell-mediated killing of cancer cells. IL12-based cancer gene therapy can overcome IL12's life-threatening adverse effects, but its clinical translation has been limited by the lack of systemic gene-delivery vectors capable of efficiently transfecting tumors to produce sufficient local IL12. Macrophages inherently excrete IL12, and tumor-associated macrophages (TAMs) are the major tumor component taking up a large fraction of the vectors arriving in the tumor. It is thus hypothesized that a gene vector efficiently transfecting both cancer cells and TAMs would make the tumor to produce sufficient IL12; however, gene transfection of TAMs is challenging due to their inherent strong degradation ability. Herein, an IL12 gene-delivery vector is designed that efficiently transfects both cancer cells and TAMs to make them as a factory for IL12 production, which efficiently activates anticancer immune responses and remodels the tumor microenvironment, for instance, increasing the M1/M2 ratio by more than fourfold. Therefore, the intravenously administered vector retards tumor growth and doubles survival in three animal models' with negligible systemic toxicities. This work reports the first nonviral IL12 gene delivery system that effectively makes use of both macrophages and tumor cells.

Pembrolizumab and tavokinogene telseplasmid electroporation in metastatic melanoma

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TAVO is a novel office-based local therapy effective in patients with advanced melanoma.

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Involves direct injection of an IL-12 plasmid into an accessible tumor by electroporation.

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Case study to assess efficacy of TAVO in patients with rheumatoid arthritis.

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Found to be a safe and effective local treatment with abscopal effect.

Introduction

Tavokinogene Telseplasmid Electroporation Therapy (TAVO) and Pembrolizumab therapy is being studied in subjects with immune checkpoint inhibitor (ICI) resistant melanoma. TAVO is a novel office-based local therapy shown to be effective in patients with advanced melanoma. The technique involves the direct injection of a plasmid encoding IL-12 into an accessible tumor driven by electroporation. The tumor cells have then been shown to express high levels of IL-12 resulting in a local inflammatory response within the tumor microenvironment.

Presentation of case

The patient with stage IIB, pT3b melanoma was treated with primary tumor resection and found to have a negative sentinel node biopsy. She subsequently developed regional recurrence and was treated with inguinal lymphadenectomy and adjuvant Nivolumab. Despite therapy, she had progression of disease with skin and subcutaneous metastases (in-transit lesions), brain and liver lesions, hilar and iliac nodal disease. She was transitioned to nivolumab + ipilimumab, and Talimogene Laherparepvec (T-VEC) therapy for the in-transit lesions, without success. Stereotactic radiosurgery was used for the brain metastasis. Groin subcutaneous and in-transit lesions were treated with TAVO and intravenous pembrolizumab. Serial physical exams and CT scans were used to assess response.

Discussion

All lesions treated with TAVO resolved. An abscopal response was also noted: hilar and mediastinal lymphadenopathy resolved. The liver mass and pelvic lymphadenopathy decreased in size, and her brain metastasis remained stable after radiation.

Conclusion

This case suggests that combination TAVO and Pembrolizumab is a safe and effective local treatment for ICI resistant metastatic melanoma in the setting of rheumatoid arthritis. An abscopal effect was also noted through control of systemic disease.

Intratumoral Immunotherapy for Early-stage Solid Tumors

The unprecedented benefits of immunotherapy in advanced malignancies have resulted in increased interests in exploiting immune stimulatory agents in earlier-stage solid tumors in the neoadjuvant setting. However, systemic delivery of immunotherapies may cause severe immune-related side-effects and hamper the development of combination treatments. Intratumoral delivery of neoadjuvant immunotherapy provides a promising strategy in harnessing the power of immunotherapy while minimizing off-target toxicities. The direct injection of immune stimulating agents into the tumor primes the local tumor-specific immunity to generate a systemic, durable clinical response. Intratumoral immunotherapy is a highly active area of investigation resulting in a plethora of agents, for example, immune receptor agonists, non-oncolytic and oncolytic viral therapies, being tested in preclinical and clinical settings. Currently, more than 20 neoadjuvant clinical trials exploring distinct intratumoral immune stimulatory agents and their combinations are ongoing. Practical considerations, including appropriate timing and optimal local delivery of immune stimulatory agents play an important role in safety and efficacy of this approach. Here, we discuss promising approaches in drug delivery technologies and opportunity for combining intratumoral immunotherapy with other cancer treatments and summarize the recent preclinical and clinical evidences that highlighted its promise as a part of routine oncologic care.

Intratumoral and Combination Therapy in Melanoma and Other Skin Cancers

Skin cancer, as the most physically accessible malignancy, allows for the greatest variety in treatment innovation. The last 2 decades have seen striking increases in the life expectancies of those diagnosed with malignant melanoma. However, many cases remain in which disease prevails against standard treatment, and those patients rely on continuing ingenuity. Drugs that can be injected directly into patients' tumors have become increasingly promising, not least for the reduction in side effects observed. Intratumoral therapy encompasses a wide array of agents, from chemotherapeutic drugs to cancer vaccines. While each show some efficacy, those agents which regulate the immune system likely have the greatest potential for preventing disease progression or recurrence. Recent research has highlighted the importance of the presence of cytotoxic T cells and of keeping regulatory T cells in check. Thus, manipulating the tumor microenvironment is a need in skin cancer therapy, which intratumoral delivery can potentially address. In order to find the best approach to each person's disease, more studies are needed to test intralesional agents in combination with currently approved therapies and with each other.

Characterization of abscopal effects of intratumoral electroporation-mediated IL-12 gene therapy

Intratumoral electroporation-mediated IL-12 gene therapy (IT-pIL12/EP) has been shown to be safe and effective in clinical trials, demonstrating systemic antitumor effects with local delivery of this potent cytokine. We recently optimized our IL-12 gene delivery platform to increase transgene expression and efficacy in preclinical models. Here we analyze the immunological changes induced with the new IT-pIL12/EP platform in both electroporated and distant, non-electroporated lesions. IT-pIL12/EP-treated tumors demonstrated rapid induction of IL-12-regulated pathways, as well as other cytokines and chemokines pathways, and upregulation of antigen presentation machinery. The distant tumors showed an increase in infiltrating lymphocytes and gene expression changes indicative of a de novo immune response in these untreated lesions. Flow cytometric analyses revealed a KLRG1hi CD8+ effector T-cell population uniquely present in mice treated with IT-pIL12/EP. Despite being highly activated, this population expressed diminished levels of PD-1 when re-exposed to antigen in the PD-L1-rich tumor. Other T-cell exhaustion markers appeared to be downregulated in concert, suggesting an orchestrated "armoring" of these effector T cells against T-cell checkpoints when primed in the presence of IL-12 in situ. These cells may represent an important mechanism by which local IL-12 gene therapy can induce a systemic antitumor immune response without the associated toxicity of systemic IL-12 exposure.

Advances in the development of intralesional therapies for melanoma

Advances in immune therapy have changed the landscape of advanced melanoma treatment. Intralesional therapy is an important type of immune therapy due to its efficacy and safety, especially in the setting of locoregional metastases. These therapies induce frequent responses in injected lesions as well as distant nontreated lesions through a 'bystander' effect of priming an antitumor immune response. The culmination of nearly a century of innovation has led to the approval of the first US FDA approved intralesional therapy for melanoma in talimogene laherparepvec. Numerous efforts to combine intralesional therapies with systemic immune checkpoint inhibitors are ongoing, whereby a synergistic effect may continue to improve outcomes for patients.

Intralesional treatment for advanced melanoma: what's on the horizon?

Advances in treatment of melanoma with systemic immunotherapies continue, with promising findings for anti-PD-1 agents combined with ipilimumab. Still, an unmet need persists because of populations ineligible for systemic immunotherapies, incomplete cure/response rates, toxicities and extreme costs. Also, potential for effective use of intralesional therapies remains, especially for local regional disease, but also for benefits of local ablation and adjuvant systemic host tumor-specific responses. Clinical trials of T-VEC, PV-10, CAVATAK and electroporation with plasmid IL-12 have demonstrated favorable, durable responses. Initial experience combining T-VEC, the agent furthest along in testing, with ipilimumab revealed higher complete and overall response rates than with either agent alone. Intralesional therapies may offer a treatment tool in the growing therapeutic armamentarium against this lethal disease.