Intratumoral anti-CTLA-4 therapy: enhancing efficacy while avoiding toxicity

Redox-responsive CpG-dextran conjugate enhances anti-tumour immunity following intratumoral administration

Conjugation of a therapeutic agent to a polymer for enhanced delivery into target cells followed by its intracellular triggered release has proved to be an effective drug delivery approach. This approach is applied to the delivery of the immune-stimulatory unmethylated cytosine-phosphate-guanine (CpG) oligonucleotide for an anti-tumour immune response after intratumoral administration. On average four CpG-1668 molecules were covalently linked to a 40-kDa amino-functionalised dextran polymer via either a non-reversible (CpG-dextran) or an intracellular redox-responsive disulfide linkage (CpG-SS-dextran). Dynamic light scattering analysis showed that both conjugates had a similar particle size and surface charge of 17 nm and -10 mV, respectively. Agarose gel electrophoresis analysis showed that CpG-SS-dextran was stable in the extracellular low glutathione (GSH) concentration range (i.e. 10-20 μM) and was cleaved at the higher intracellular GSH concentration (5 mM), while CpG-dextran was stable in both GSH concentrations. Uptake and activation assays on bone-marrow-derived dendritic cells showed no significant difference between free CpG, CpG-dextran and CpG-SS-dextran. In a mouse subcutaneous colorectal tumour model the CpG-SS-dextran showed a statistically significantly greater inhibition of tumour growth (p < 0.03) and prolonged survival (p < 0.001) compared to CpG-dextran or free CpG. These results demonstrate that the redox-triggered intracellular release of CpG from a dextran polymer carrier has promise for intratumoral therapeutic vaccination against cancer.

Novel technologies for applying immune checkpoint blockers

Cancer cells develop several ways to subdue the immune system among others via upregulation of inhibitory immune checkpoint (ICP) proteins. These ICPs paralyze immune effector cells and thereby enable unfettered tumor growth. Monoclonal antibodies (mAbs) that block ICPs can prevent immune exhaustion. Due to their outstanding effects, mAbs revolutionized the field of cancer immunotherapy. However, current ICP therapy regimens suffer from issues related to systemic administration of mAbs, including the onset of immune related adverse events, poor pharmacokinetics, limited tumor accessibility and immunogenicity. These drawbacks and new insights on spatiality prompted the exploration of novel administration routes for mAbs for instance peritumoral delivery. Moreover, novel ICP drug classes that are adept to novel delivery technologies were developed to circumvent the drawbacks of mAbs. We therefore review the state-of-the-art and novel delivery strategies of ICP drugs.

Alternative Routes of Administration for Therapeutic Antibodies—State of the Art

Background: For the past two decades, there has been a huge expansion in the development of therapeutic antibodies, with 6 to 10 novel entities approved each year. Around 70% of these Abs are delivered through IV injection, a mode of administration allowing rapid and systemic delivery of the drug. However, according to the evidence presented in the literature, beyond the reduction of invasiveness, a better efficacy can be achieved with local delivery. Consequently, efforts have been made toward the development of innovative methods of administration, and in the formulation and engineering of novel Abs to improve their therapeutic index. Objective: This review presents an overview of the routes of administration used to deliver Abs, different from the IV route, whether approved or in the clinical evaluation stage. We provide a description of the physical and biological fundamentals for each route of administration, highlighting their relevance with examples of clinically-relevant Abs, and discussing their strengths and limitations. Methods: We reviewed and analyzed the current literature, published as of the 1 April 2022 using MEDLINE and EMBASE databases, as well as the FDA and EMA websites. Ongoing trials were identified using clinicaltrials.gov. Publications and data were identified using a list of general keywords. Conclusions: Apart from the most commonly used IV route, topical delivery of Abs has shown clinical successes, improving drug bioavailability and efficacy while reducing side-effects. However, additional research is necessary to understand the consequences of biological barriers associated with local delivery for Ab partitioning, in order to optimize delivery methods and devices, and to adapt Ab formulation to local delivery. Novel modes of administration for Abs might in fine allow a better support to patients, especially in the context of chronic diseases, as well as a reduction of the treatment cost.

Harnessing anti-cytomegalovirus immunity for local immunotherapy against solid tumors

Tumor infiltration by T cells profoundly affects cancer progression and responses to immunotherapy. However, the tumor immunosuppressive microenvironment can impair the induction, trafficking, and local activity of antitumor T cells. Here, we investigated whether intratumoral injection of virus-derived peptide epitopes could activate preexisting antiviral T cell responses locally and promote antitumor responses or antigen spreading. We focused on a mouse model of cytomegalovirus (CMV), a highly prevalent human infection that induces vigorous and durable T cell responses. Mice persistently infected with murine CMV (MCMV) were challenged with lung (TC-1), colon (MC-38), or melanoma (B16-F10) tumor cells. Intratumoral injection of MCMV-derived T cell epitopes triggered in situ and systemic expansion of their cognate, MCMV-specific CD4⁺ or CD8⁺ T cells. The MCMV CD8⁺ T cell epitopes injected alone provoked arrest of tumor growth and some durable remissions. Intratumoral injection of MCMV CD4⁺ T cell epitopes with polyinosinic acid:polycytidylic acid (pI:C) preferentially elicited tumor antigen-specific CD8⁺ T cells, promoted tumor clearance, and conferred long-term protection against tumor rechallenge. Notably, secondary proliferation of MCMV-specific CD8⁺ T cells correlated with better tumor control. Importantly, intratumoral injection of MCMV-derived CD8⁺ T cell-peptide epitopes alone or CD4⁺ T cell-peptide epitopes with pI:C induced potent adaptive and innate immune activation of the tumor microenvironment. Thus, CMV-derived peptide epitopes, delivered intratumorally, act as cytotoxic and immunotherapeutic agents to promote immediate tumor control and long-term antitumor immunity that could be used as a stand-alone therapy. The tumor antigen-agnostic nature of this approach makes it applicable across a broad range of solid tumors regardless of their origin.

Intratumoral immunotherapy relies on B and T cell collaboration

Antitumor T cell responses are the primary mediators of cancer immunotherapy. However, many other components of the immune system are needed for efficient T cell responses to be generated. Here, we developed a combinatorial approach where a Toll-like receptor 9 agonist (CpG) and Fc-fused IL-12 protein were injected together into just one of several tumor sites in a mouse. This combination led to body-wide (abscopal) therapeutic responses in multiple cancer models. These systemic responses were dependent not only on T cells but also on B cells. B cells were activated by the treatment and were required for optimal T cell activation. This cross-talk was dependent on MHC and was tumor antigen specific. The addition of an agonistic antibody against OX40 further enhanced T cell activation and therapeutic responses. Our data suggest that the combination of CpG, anti-OX40, and IL-12Fc may have success in patients with cancer and that B and T cell collaboration is crucial for the efficacy of this combination immunotherapy.

The "Great Debate" at Immunotherapy Bridge 2021, December 1st-2nd, 2021

As part of the 2021 Immunotherapy Bridge virtual congress (December 1–2, Naples, Italy), the Great Debate sessions featured experts who were assigned counter opposing views on four important questions in immunotherapy today. The first topic was whether oncolytic viruses or other specific immunomodulators were the more promising approach for intralesional therapy. The second was whether early surrogate endpoints, such as response rate or progression-free survival, correlate with long-term overall survival was considered. Thirdly, whether vaccines can transform cold into hot tumors was discussed and, finally, broad versus deep analytic profiling approaches to gain insights into immune-oncology development were compared. As with previous Bridge congresses, presenters were invited by the meeting Chairs and positions taken during the debates may not have reflected their respective personal view. In addition, the views summarised in this article are based on available evidence but may reflect personal interpretation of these data, clinical experience and subjective opinion of the speaker.

Vectorized Treg-depleting αCTLA-4 elicits antigen cross-presentation and CD8+ T cell immunity to reject ‘cold’ tumors

Background

Immune checkpoint blockade (ICB) is a clinically proven concept to treat cancer. Still, a majority of patients with cancer including those with poorly immune infiltrated ‘cold’ tumors are resistant to currently available ICB therapies. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is one of few clinically validated targets for ICB, but toxicities linked to efficacy in approved αCTLA-4 regimens have restricted their use and precluded full therapeutic dosing. At a mechanistic level, accumulating preclinical and clinical data indicate dual mechanisms for αCTLA-4; ICB and regulatory T cell (Treg) depletion are both thought to contribute efficacy and toxicity in available, systemic, αCTLA-4 regimens. Accordingly, strategies to deliver highly effective, yet safe αCTLA-4 therapies have been lacking. Here we assess and identify spatially restricted exposure to a novel strongly Treg-depleting, checkpoint-blocking, vectorized αCTLA-4, as a highly efficacious and potentially safe strategy to target CTLA-4.

Methods

A novel human IgG1 CTLA-4 antibody (4-E03) was identified using function-first screening for monoclonal antibodies (mAbs) and targets associated with superior Treg-depleting activity. A tumor-selective oncolytic vaccinia vector was then engineered to encode this novel, strongly Treg-depleting, checkpoint-blocking, αCTLA-4 antibody or a matching surrogate antibody, and Granulocyte-macrophage colony-stimulating factor (GM-CSF) (VVGM-αCTLA-4).

Results

The identified 4-E03 antibody showed significantly stronger Treg depletion, but equipotent checkpoint blockade, compared with clinically validated αCTLA-4 ipilimumab against CTLA-4-expressing Treg cells in a humanized mouse model in vivo. Intratumoral administration of VVGM-αCTLA-4 achieved tumor-restricted CTLA-4 receptor saturation and Treg depletion, which elicited antigen cross-presentation and stronger systemic expansion of tumor-specific CD8+ T cells and antitumor immunity compared with systemic αCTLA-4 antibody therapy. Efficacy correlated with FcγR-mediated intratumoral Treg depletion. Remarkably, in a clinically relevant mouse model resistant to systemic ICB, intratumoral VVGM-αCTLA-4 synergized with αPD-1 to reject cold tumors.

Conclusion

Our findings demonstrate in vivo proof of concept for spatial restriction of Treg depletion-optimized immune checkpoint blocking, vectorized αCTLA-4 as a highly effective and safe strategy to target CTLA-4. A clinical trial evaluating intratumoral VVGM-αhCTLA-4 (BT-001) alone and in combination with αPD-1 in metastatic or advanced solid tumors has commenced.

Tumor eradicated by combination of imiquimod and OX40 agonist for in situ vaccination

Various cancer vaccines have been developed to generate and amplify antigen‐specific T cell responses against malignancy. Among them, in situ vaccination is one of the most practical types as it can trigger immune responses without previous antigen identification. Here we reported a novel in situ vaccine by intratumoral injection of imiquimod and OX40 agonist. In mice bearing hepatic carcinoma, both the injected tumor and the noninjected tumor in the distant lesion of the same mice were suppressed after vaccination. Further studies found that this in situ vaccine triggered systemic tumor‐specific responses, with one‐fold increase of effector memory T cells properties and stronger toxicity of lymphocytes in spleen. Besides, we found that imiquimod upregulated the expression of OX40 on CD4⁺ T cells and thus enhanced the effectiveness of OX40 agonist. Five immune‐positive‐related pathways were activated after vaccination. This in situ vaccine caused little harm to normal organs and provided long‐term protection against the same syngeneic tumor rechallenge. Due to its effectiveness, feasibility and safety, this strategy could potentially be applied to various types of late‐stage solid tumors and worthy of further clinical research.

Priming and Propagating Anti-tumor Immunity: Focal Hypofractionated Radiation for in Situ Vaccination and Systemic Targeted Radionuclide Theranostics for Immunomodulation of Tumor Microenvironments

Recent preclinical and clinical studies have elucidated mechanisms whereby radiation therapy influences the anti-tumor immune response. Immunogenic cell death and phenotypic changes in tumor cells surviving radiation may underlie this effect and contribute to the capacity of radiation to elicit an in situ tumor vaccine effect. In situ vaccination is a therapeutic strategy that seeks to convert a patient's own tumor into a source of enhanced antigen recognition for the purpose of augmenting a systemic anti-tumor immune response. Capitalizing on the in situ vaccine effect of radiation, several groups have demonstrated anti-tumor efficacy in preclinical models by combining radiation with immune checkpoint blockade. Local delivery of immune adjuvants and/or immune stimulatory cytokines via direct injection into the radiated tumor microenvironment may further increase the in situ vaccine capacity of radiation therapy. However, recent studies suggest that in some contexts this effect is antagonized by the presence of distant untreated sites of disease that may dampen the systemic immune response generated by in situ vaccination through a phenomenon termed concomitant immune tolerance. Concomitant immune tolerance may be overcome by delivering radiation to all sites of metastatic disease, however this is often not possible to safely achieve using external beam radiation therapy without considerable risk of lymphopenia that would negate the immune effects of in situ vaccination. For patients with widespread metastatic disease, alternative strategies may include systemic treatment with targeted radionuclide therapies alone or in combination with an external beam radiation therapy-based in situ vaccine approach.

Intratumoural administration and tumour tissue targeting of cancer immunotherapies

Immune-checkpoint inhibitors and chimeric antigen receptor (CAR) T cells are revolutionizing oncology and haematology practice. With these and other immunotherapies, however, systemic biodistribution raises safety issues, potentially requiring the use of suboptimal doses or even precluding their clinical development. Delivering or attracting immune cells or immunomodulatory factors directly to the tumour and/or draining lymph nodes might overcome these problems. Hence, intratumoural delivery and tumour tissue-targeted compounds are attractive options to increase the in situ bioavailability and, thus, the efficacy of immunotherapies. In mouse models, intratumoural administration of immunostimulatory monoclonal antibodies, pattern recognition receptor agonists, genetically engineered viruses, bacteria, cytokines or immune cells can exert powerful effects not only against the injected tumours but also often against uninjected lesions (abscopal or anenestic effects). Alternatively, or additionally, biotechnology strategies are being used to achieve higher functional concentrations of immune mediators in tumour tissues, either by targeting locally overexpressed moieties or engineering 'unmaskable' agents to be activated by elements enriched within tumour tissues. Clinical trials evaluating these strategies are ongoing, but their development faces issues relating to the administration methodology, pharmacokinetic parameters, pharmacodynamic end points, and immunobiological and clinical response assessments. Herein, we discuss these approaches in the context of their historical development and describe the current landscape of intratumoural or tumour tissue-targeted immunotherapies.

Pickering emulsions with ethiodized oil and nanoparticles for slow release of intratumoral anti-CTLA4 immune checkpoint antibodies

BACKGROUND

Intratumorous immunotherapy for cancer is currently thriving. The aim of such local strategy is to improve the therapeutic index of these treatments, for higher on-target/on-tumor activity and less on-target/off-tumor adverse events. Strategies allowing for slow release of anti-CTLA4 in the tumor microenvironment could improve their clinical efficacy.The purpose of the study was to develop a radiopaque delivery platform to improve the targeting and exposure of intratumorous anti-CTLA4 antibodies for cancer immunotherapy.

METHODS

Pickering emulsions of anti-CTLA4 antibodies were formulated with radiopaque ethiodized oil and poly-lactic-co-glycolic acid (PLGA) nanoparticles. We characterized the microscopic aspect and stability of such emulsions using Turbiscan. We monitored the release of anti-CTLA4 over time from these emulsions and evaluated their structure using mass spectrometry. We then tested the functionality of the released antibodies by preforming ex vivo competitive binding assays. Finally, we assessed the in vivo efficacy of intratumorous anti-CTLA4 Pickering emulsions.

RESULTS

Pickering emulsions of ethiodized oil and PLGA nanoparticles (PEEPs) resulted in a radiopaque water-in-oil emulsion with average internal phase droplet size of 42±5 µm at day 7. Confocal microscopy showed that anti-CTLA4 antibodies were effectively encapsulated by ethiodized oil with PLGA nanoparticles located at the interface between the aqueous and the oily phase. Turbiscan analysis showed that emulsions were stable with continuous and progressive release of anti-CTLA4 antibodies reaching 70% at 3 weeks. Structural and functional analysis of the released antibodies did not show significant differences with native anti-CTLA4 antibodies. Finally, intratumorous anti-CTLA4 PEEPs were able to eradicate tumors and cure mice in a syngeneic immunocompetent preclinical tumor model.

CONCLUSION

Pickering emulsions of ethiodized oil and PLGA is an innovative radiopaque delivery platform that does not alter the functionality of anti-CTLA4 immune checkpoint antibodies. Beyond local anti-CTLA4 applications, these emulsions might be used with other therapeutic molecules for optimal intratumorous or intra-arterial delivery of novel cancer immunotherapies.

Intracerebral administration of CTLA-4 and PD-1 immune checkpoint blocking monoclonal antibodies in patients with recurrent glioblastoma: a phase I clinical trial

Background

Patients with recurrent glioblastoma (rGB) have a poor prognosis with a median overall survival (OS) of 30–39 weeks in prospective clinical trials. Intravenous administration of programmed cell death protein 1 and cytotoxic T-lymphocyte-associated antigen 4 inhibitors has low activity in patients with rGB. In this phase I clinical trial, intracerebral (IC) administration of ipilimumab (IPI) and nivolumab (NIVO) in combination with intravenous administration of NIVO was investigated.

Methods

Within 24 hours following the intravenous administration of a fixed dose (10 mg) of NIVO, patients underwent a maximal safe resection, followed by injection of IPI (10 mg; cohort-1), or IPI (5 mg) plus NIVO (10 mg; cohort-2) in the brain tissue lining the resection cavity. Intravenous administration of NIVO (10 mg) was repeated every 2 weeks (max. five administrations). Next generation sequencing and RNA gene expression profiling was performed on resected tumor tissue.

Results

Twenty-seven patients were enrolled (cohort-1: n=3; cohort-2: n=24). All patients underwent maximal safe resection and planned IC administrations and preoperative NIVO. Thirteen patients (cohort-1: n=3; cohort-2: n=10) received all five postoperative intravenous doses of NIVO. In cohort-2, 14 patients received a median of 3 (range 1–4) intravenous doses. Subacute postoperative neurological deterioration (n=2) was reversible on steroid treatment; no other central nervous system toxicity was observed. Immune-related adverse events were infrequent and mild. GB recurrence was diagnosed in 26 patients (median progression-free survival (PFS) is 11.7 weeks (range 2–152)); 21 patients have died due to progression. Median OS is 38 weeks (95% CI: 27 to 49) with a 6-month, 1-year, and 2-year OS-rate of, respectively, 74.1% (95% CI: 57 to 90), 40.7% (95% CI: 22 to 59), and 27% (95% CI: 9 to 44). OS compares favorable against a historical cohort (descriptive Log-Rank p>0.003). No significant difference was found with respect to PFS (descriptive Log-Rank test p>0.05). A higher tumor mRNA expression level of B7-H3 was associated with a significantly worse survival (multivariate Cox logistic regression, p>0.029).

Conclusion

IC administration of NIVO and IPI following maximal safe resection of rGB was feasible, safe, and associated with encouraging OS.

Trial registration

NCT03233152.

Toll-Like Receptor-Based Strategies for Cancer Immunotherapy

Toll-like receptors (TLRs) are expressed and play multiple functional roles in a variety of immune cell types involved in tumor immunity. There are plenty of data on the pharmacological targeting of TLR signaling using agonist molecules that boost the antitumor immune response. A recent body of research has also demonstrated promising strategies for improving the cell-based immunotherapy methods by inducing TLR signaling. These strategies include systemic administration of TLR antagonist along with immune cell transfer and also genetic engineering of the immune cells using TLR signaling components to improve the function of genetically engineered immune cells such as chimeric antigen receptor-modified T cells. Here, we explore the current status of the cancer immunotherapy approaches based on manipulation of TLR signaling to provide a perspective of the underlying rationales and potential clinical applications. Altogether, reviewed publications suggest that TLRs make a potential target for the immunotherapy of cancer.

Targeting Cancer Heterogeneity with Immune Responses Driven by Oncolytic Peptides

Accumulating preclinical and clinical evidence indicates that high degrees of heterogeneity among malignant cells constitute a considerable obstacle to the success of cancer therapy. This calls for the development of approaches that operate - or enable established treatments to operate - despite such intratumoral heterogeneity (ITH). In this context, oncolytic peptides stand out as promising therapeutic tools based on their ability to drive immunogenic cell death associated with robust anticancer immune responses independently of ITH. We review the main molecular and immunological pathways engaged by oncolytic peptides, and discuss potential approaches to combine these agents with modern immunotherapeutics in support of superior tumor-targeting immunity and efficacy in patients with cancer.

Toll-like receptors (TLRs) in cancer; with an extensive focus on TLR agonists and antagonists

At the forefront of the battle against pathogens or any endogenously released molecules, toll-like receptors (TLRs) play an important role as the most noble pattern recognition receptors. The ability of these receptors in distinguishing "self" and "non-self" antigens is a cornerstone in the innate immunity system; however, misregulation links inflammatory responses to the development of human cancers. It has been known for some time that aberrant expression and regulation of TLRs not only endows cancer cells an opportunity to escape from the immune system but also supports them through enhancing proliferation and angiogenesis. Over the past decades, cancer research studies have witnessed a number of preclinical and clinical breakthroughs in the field of TLR modulators and some of the agents have exceptionally performed well in advanced clinical trials. In the present review, we have provided a comprehensive review of different TLR agonists and antagonists and discuss their limitations, toxicities, and challenges to outline their future incorporation in cancer treatment strategies.

Intratumoral Combinatorial Administration of CD1c (BDCA-1)+ Myeloid Dendritic Cells Plus Ipilimumab and Avelumab in Combination with Intravenous Low-Dose Nivolumab in Patients with Advanced Solid Tumors: A Phase IB Clinical Trial

Intratumoral (IT) myeloid dendritic cells (myDCs) play a pivotal role in re-licensing antitumor cytotoxic T lymphocytes. IT injection of the IgG₁ monoclonal antibodies ipilimumab and avelumab may induce antibody-dependent cellular cytotoxicity, thereby enhancing the release of tumor antigens that can be captured and processed by CD1c (BDCA-1)⁺ myDCs. Patients with advanced solid tumors after standard care were eligible for IT injections of ≥1 lesion with ipilimumab (10 mg) and avelumab (40 mg) and intravenous (IV) nivolumab (10 mg) on day 1, followed by IT injection of autologous CD1c (BDCA-1)⁺ myDCs on day 2. IT/IV administration of ipilimumab, avelumab, and nivolumab was repeated bi-weekly. Primary objectives were safety and feasibility. Nine patients were treated with a median of 21 × 10⁶ CD1c (BDCA-1)⁺ myDCs, and a median of 4 IT/IV administrations of ipilimumab, avelumab, and nivolumab. The treatment was safe with mainly injection-site reactions, but also immune-related pneumonitis (n = 2), colitis (n = 1), and bullous pemphigoid (n = 1). The best response was a durable partial response in a patient with stage IV melanoma who previously progressed on checkpoint inhibitors. Our combinatorial therapeutic approach, including IT injection of CD1c (BDCA-1)⁺ myDCs, is feasible and safe, and it resulted in encouraging signs of antitumor activity in patients with advanced solid tumors.

Immunomodulatory Effects of Radiotherapy

Radiation therapy (RT), an integral component of curative treatment for many malignancies, can be administered via an increasing array of techniques. In this review, we summarize the properties and application of different types of RT, specifically, conventional therapy with x-rays, stereotactic body RT, and proton and carbon particle therapies. We highlight how low-linear energy transfer (LET) radiation induces simple DNA lesions that are efficiently repaired by cells, whereas high-LET radiation causes complex DNA lesions that are difficult to repair and that ultimately enhance cancer cell killing. Additionally, we discuss the immunogenicity of radiation-induced tumor death, elucidate the molecular mechanisms by which radiation mounts innate and adaptive immune responses and explore strategies by which we can increase the efficacy of these mechanisms. Understanding the mechanisms by which RT modulates immune signaling and the key players involved in modulating the RT-mediated immune response will help to improve therapeutic efficacy and to identify novel immunomodulatory drugs that will benefit cancer patients undergoing targeted RT.

Advances in engineering local drug delivery systems for cancer immunotherapy

Cancer immunotherapy aims to leverage the immune system to suppress the growth of tumors and to inhibit metastasis. The recent promising clinical outcomes associated with cancer immunotherapy have prompted research and development efforts towards enhancing the efficacy of immune checkpoint blockade, cancer vaccines, cytokine therapy, and adoptive T cell therapy. Advancements in biomaterials, nanomedicine, and micro-/nano-technology have facilitated the development of enhanced local delivery systems for cancer immunotherapy, which can enhance treatment efficacy while minimizing toxicity. Furthermore, locally administered cancer therapies that combine immunotherapy with chemotherapy, radiotherapy, or phototherapy have the potential to achieve synergistic antitumor effects. Herein, the latest studies on local delivery systems for cancer immunotherapy are surveyed, with an emphasis on the therapeutic benefits associated with the design of biomaterials and nanomedicines. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Bronchoscopic intratumoural therapies for non-small cell lung cancer

The past decade has brought remarkable improvements in the treatment of non-small cell lung cancer (NSCLC) with novel therapies, such as immune checkpoint inhibitors, although response rates remain suboptimal. Direct intratumoural injection of therapeutic agents via bronchoscopic approaches poses the unique ability to directly target the tumour microenvironment and offers several theoretical advantages over systemic delivery including decreased toxicity. Increases in understanding of the tumour microenvironment and cancer immunology have identified many potential options for intratumoural therapy, especially combination immunotherapies. Herein, we review advances in the development of novel bronchoscopic treatments for NSCLC over the past decade with a focus on the potential of intratumoural immunotherapy alone or in combination with systemic treatments.

Modeling multi-needle injection into solid tumor

The discovery of mechanisms by which the cancer cells avoid the host immune attack (immune checkpoints) as well the capability of the monoclonal antibodies (mAbs) to blockade the checkpoint proteins on cancer and tumor-infiltrating cells (CTLA-4, PD-1, and PD-L1) promised new breakthroughs in the cure of cancer. After these mechanisms of cancer escaping the host immunity were undoubtedly confirmed in numerous experimental and clinical studies, the FDA approval of CTLA-4 and PD-1/PD-L1 mAbs for systemic treatment thought to revolutionize the outcome of cancer treatment. However, as of today, the anticipated curative effect of anti-CTLA-4 and PD-1/PD-L1 mAb treatments has been observed only in a small population of patients. In addition, systemic administration of mAbs in clinics has been found associated with new toxicity profiles, sometimes very severe. The main obstacle that hinders the mAbs therapy appears to be the inability of delivering mAbs to a sufficient number of cancer cells and tumor infiltrating cells. As an alternative to the systemic administration (or as a complement to it), local intratumoral delivery of mAbs has been anticipated to resolve that issue. However, unlike the systemic mAbs administration, for which formidable but surmountable obstacles (big size of mAbs ~150 kD, high interstitial fluid pressure in solid tumors, etc.) have been known to hamper mAbs delivery to cancer and tumor-infiltrating cells, the lack of effects of intratumoral mAbs administration remains completely incomprehensible and needs a new theoretical reconsideration that we have attempted in our analysis. It can be suggested that the limited benefits of the intratumoral mAbs administration appeared to be rooted in the same problem that hindered the effects of systemic mAbs administration: the inability to reach a sufficient number of cancer cells and tumor-infiltrating cells. We hypothesize that the core of the problem stems from the fact that the single-needle intratumoral injection forms a very localized, jet-like distribution of the drug (mAbs) that constitutes only a small fraction of the total volume of the tumor. In this light we are re-evaluating the theoretical reasonableness of the single-needle intratumoral injection approach. We propose that multi-needle injection will circumvent this limitation and for that we analyze the behavior of an injectant in tissues using different configurations of the injection needles. To accomplish this goal, we created a model of injectant distribution in a solid tissue based on the traditional technique of single-needle injection and then extended that model to a case of simultaneous multi-needle injection. To develop the model of drug delivery and transport in biological tissues, we followed a frequently used approach of modeling the diffusive transport of liquid through a porous media using the Darcy's law that relates the flow velocity, the pressure gradient, and the tissue permeability. The analysis demonstrates that a multi-needle injection setup provides a significantly more widespread and homogeneous injectant distribution within a solid tumor than that for a single needle injection for the same tumor size. Adding separate draining needles can further improve the delivery of injectant to cancer and tumor-infiltrating cells.

Eradication of spontaneous malignancy by local immunotherapy

It has recently become apparent that the immune system can cure cancer. In some of these strategies, the antigen targets are preidentified and therapies are custom-made against these targets. In others, antibodies are used to remove the brakes of the immune system, allowing preexisting T cells to attack cancer cells. We have used another noncustomized approach called in situ vaccination. Immunoenhancing agents are injected locally into one site of tumor, thereby triggering a T cell immune response locally that then attacks cancer throughout the body. We have used a screening strategy in which the same syngeneic tumor is implanted at two separate sites in the body. One tumor is then injected with the test agents, and the resulting immune response is detected by the regression of the distant, untreated tumor. Using this assay, the combination of unmethylated CG-enriched oligodeoxynucleotide (CpG)-a Toll-like receptor 9 (TLR9) ligand-and anti-OX40 antibody provided the most impressive results. TLRs are components of the innate immune system that recognize molecular patterns on pathogens. Low doses of CpG injected into a tumor induce the expression of OX40 on CD4⁺ T cells in the microenvironment in mouse or human tumors. An agonistic anti-OX40 antibody can then trigger a T cell immune response, which is specific to the antigens of the injected tumor. Remarkably, this combination of a TLR ligand and an anti-OX40 antibody can cure multiple types of cancer and prevent spontaneous genetically driven cancers.

Methods for improving the immunogenicity and efficacy of cancer vaccines

INTRODUCTION

Cancer vaccines represent one of the oldest immunotherapy strategies. A variety of tumor-associated antigens have been exploited to investigate their immunogenicity as well as multiple strategies for vaccine administration. These efforts have led to the development of several clinical trials in tumors with different histological origins to test the clinical efficacy of cancer vaccines. However, suboptimal clinical results have been reported mainly due to the lack of optimized strategies to induce strong and sustained systemic tumor antigen-specific immune responses.

AREAS COVERED

We provide an overview of different types of cancer vaccines that have been developed and used in the context of clinical studies. Moreover, we review different preclinical and clinical strategies pursued to enhance the immunogenicity, stability, and targeting at tumor site of cancer vaccines.

EXPERT OPINION

Additional and appropriate preclinical studies are warranted to optimize the immunogenicity and delivery of cancer vaccines. The appropriate choice of target antigens is challenging; however, the exploitation of neoantigens generated from somatic mutations of tumor cells represents a promising approach to target highly immunogenic tumor-specific antigens. Remarkably, the investigation of the combination of cancer vaccines with immunomodulating agents able to skew the tumor microenvironment from immunosuppressive to immunostimulating will dramatically improve their clinical efficacy.

ImmTAC/Anti-PD-1 antibody combination to enhance killing of cancer cells by reversing regulatory T-cell-mediated immunosuppression

Recently, bi-functional molecules that can redirect immune effectors to tumour cells have emerged as potentially robust mediators of tumour regression in clinical trials. Two modalities in particular, bi-specific antibodies for T-cell redirection and activation (BiTe) and immune-mobilizing monoclonal T-cell receptors against cancer (ImmTAC), are being evaluated in efficacy studies as 'off-the-shelf' reagents. Optimal therapy will require an understanding and means to address regulatory mechanisms of limiting efficacy. In light of this, we evaluated the impact of induced regulatory T (iTreg) cells on the efficacy of tumour cell killing redirected by ImmTAC and demonstrated down-regulation of T-cell proliferation and expression of CD25, CD107a, Granzyme B and Perforin by ImmTAC-redirected T cells. Significant recovery of ImmTAC potency, however, could be achieved when combined with an anti-programmed cell death protein 1 monoclonal antibody. Furthermore, we found that among lung cancer patients failing to respond to ImmTAC therapy, there was a significantly higher fraction of Treg cells in the peripheral blood mononuclear cells of lung cancer patients than in healthy donors. These results provide in vitro evidence for an iTreg cell-mediated immunosuppression of ImmTAC-redirected T-cell responses. Whilst immune checkpoint blockade can reverse the Treg cell suppression, it forms a rational basis for a combination of the blockade with ImmTAC in clinical trials.

TLR Agonists as Adjuvants for Cancer Vaccines

Toll-like receptors (TLRs) are one of the best characterised families of pattern recognition receptors (PRRs) and play a critical role in the host defence to infection. Accumulating evidence indicates that TLRs also participate in maintaining tissue homeostasis by controlling inflammation and tissue repair, as well as promoting antitumour effects via activation and modulation of adaptive immune responses. TLR agonists have successfully been exploited to ameliorate the efficacy of various cancer therapies. In this chapter, we will discuss the rationales of using TLR agonists as adjuvants to cancer treatments and summarise the recent findings of preclinical and clinical studies of TLR agonist-based cancer therapies.

Updates on immunotherapy for colorectal cancer

Despite significant advances in standard of care therapies, the 5-year survival rate for metastatic colorectal cancer (CRC) remains around 12%. Immunotherapy has not provided the stellar advances in colorectal cancer that has been seen in other malignancies. Immunotherapy appears to play a pivotal role in microsatellite unstable CRC tumors where the response rates are profound. These results have led to FDA approval of pembrolizumab for MSI-H CRC tumors. Additional research into several new immune agents including IDO inhibitors, vaccine therapy and combinatorial agents are being evaluated for CRC. This review will provide an overview of the approaches currently being investigated.

Soluble CD80 Protein Delays Tumor Growth and Promotes Tumor-Infiltrating Lymphocytes

Tumor cells use various immune-suppressive strategies to overcome antitumor immunity. One such method is tumor expression of programmed death ligand-1 (PD-L1), which triggers apoptotic death or anergy upon binding programmed death-1 (PD-1) on T cells. Our previous in vitro cellular studies with human and mouse PD-L1⁺ tumor cells demonstrated that a soluble form of the costimulatory molecule CD80 prevented PD-L1-mediated immune suppression and restored T-cell activation by binding PD-L1 and blocking interaction with PD-1. We now report that in vivo treatment of established syngeneic PD-L1⁺ CT26 colon carcinoma and B16F10 melanoma tumors with CD80-Fc delays tumor growth and promotes tumor-infiltrating T cells. Studies with PD-1^-/- and CD28^-/- mice demonstrate that soluble CD80 acts in vivo by simultaneously neutralizing PD-1 suppression and activating through CD28. We also report that soluble CD80 mediates its effects by activating transcription factors EGR1-4, NF-κB, and MAPK, downstream signaling components of the CD28 and T-cell receptor pathways. Soluble CD80 binds to CTLA-4 on activated human peripheral blood mononuclear cells. However, increasing quantities of CTLA-4 antagonist antibodies do not increase T-cell activation. These results indicate that soluble CD80 does not suppress T-cell function through CTLA-4 and suggest that CTLA-4 acts as a decoy receptor for CD80, rather than functioning as a suppressive signaling receptor. Collectively, these studies demonstrate that soluble CD80 has therapeutic efficacy in vivo in mouse tumor systems and that its effects are due to its ability to inhibit PD-1-mediated suppression while concurrently activating T cells through CD28. Cancer Immunol Res; 6(1); 59-68. ©2017 AACR.

Trial watch: Immune checkpoint blockers for cancer therapy

Immune checkpoint blockers (ICBs) are literally revolutionizing the clinical management of an ever more diversified panel of oncological indications. Although considerable attention persists around the inhibition of cytotoxic T lymphocyte-associated protein 4 (CTLA4) and programmed cell death 1 (PDCD1, best known as PD-1) signaling, several other co-inhibitory T-cell receptors are being evaluated as potential targets for the development of novel ICBs. Moreover, substantial efforts are being devoted to the identification of biomarkers that reliably predict the likelihood of each patient to obtain clinical benefits from ICBs in the absence of severe toxicity. Tailoring the delivery of specific ICBs or combinations thereof to selected patient populations in the context of precision medicine programs constitutes indeed a major objective of the future of ICB-based immunotherapy. Here, we discuss recent preclinical and clinical advances on the development of ICBs for oncological indications.

Trial Watch: Immunostimulatory monoclonal antibodies for oncological indications

The goal of cancer immunotherapy is to establish new or boost pre-existing anticancer immune responses that eradicate malignant cells while generating immunological memory to prevent disease relapse. Over the past few years, immunomodulatory monoclonal antibodies (mAbs) that block co-inhibitory receptors on immune effectors cells - such as cytotoxic T lymphocyte-associated protein 4 (CTLA4), programmed cell death 1 (PDCD1, best known as PD-1) - or their ligands - such as CD274 (best known as PD-L1) - have proven very successful in this sense. As a consequence, many of such immune checkpoint blockers (ICBs) have already entered the clinical practice for various oncological indications. Considerable attention is currently being attracted by a second group of immunomodulatory mAbs, which are conceived to activate co-stimulatory receptors on immune effector cells. Here, we discuss the mechanisms of action of these immunostimulatory mAbs and summarize recent progress in their preclinical and clinical development.

Intratumoral Immunization by p19Arf and Interferon-β Gene Transfer in a Heterotopic Mouse Model of Lung Carcinoma

Therapeutic strategies that act by eliciting and enhancing antitumor immunity have been clinically validated as an effective treatment modality but may benefit from the induction of both cell death and immune activation as primary stimuli. Using our AdRGD-PG adenovector platform, we show here for the first time that in situ gene transfer of p19Arf and interferon-β (IFNβ) in the LLC1 mouse model of lung carcinoma acts as an immunotherapy. Although p19Arf is sufficient to induce cell death, only its pairing with IFNβ significantly induced markers of immunogenic cell death. In situ gene therapy with IFNβ, either alone or in combination with p19Arf, could retard tumor progression, but only the combined treatment was associated with a protective immune response. Specifically in the case of combined intratumoral gene transfer, we identified 167 differentially expressed genes when using microarray to evaluate tumors that were treated in vivo and confirmed the activation of CCL3, CXCL3, IL1α, IL1β, CD274, and OSM, involved in immune response and chemotaxis. Histologic evaluation revealed significant tumor infiltration by neutrophils, whereas functional depletion of granulocytes ablated the antitumor effect of our approach. The association of in situ gene therapy with cisplatin resulted in synergistic elimination of tumor progression. In all, in situ gene transfer with p19Arf and IFNβ acts as an immunotherapy involving recruitment of neutrophils, a desirable but previously untested outcome, and this approach may be allied with chemotherapy, thus providing significant antitumor activity and warranting further development for the treatment of lung carcinoma.

Vectorization in an oncolytic vaccinia virus of an antibody, a Fab and a scFv against programmed cell death -1 (PD-1) allows their intratumoral delivery and an improved tumor-growth inhibition

We report here the successful vectorization of a hamster monoclonal IgG (namely J43) recognizing the murine Programmed cell death-1 (mPD-1) in Western Reserve (WR) oncolytic vaccinia virus. Three forms of mPD-1 binders have been inserted into the virus: whole antibody (mAb), Fragment antigen-binding (Fab) or single-chain variable fragment (scFv). MAb, Fab and scFv were produced and assembled with the expected patterns in supernatants of cells infected by the recombinant viruses. The three purified mPD-1 binders were able to block the binding of mPD-1 ligand to mPD-1 in vitro. Moreover, mAb was detected in tumor and in serum of C57BL/6 mice when the recombinant WR-mAb was injected intratumorally (IT) in B16F10 and MCA 205 tumors. The concentration of circulating mAb detected after IT injection was up to 1,900-fold higher than the level obtained after a subcutaneous (SC) injection (i.e., without tumor) confirming the virus tropism for tumoral cells and/or microenvironment. Moreover, the overall tumoral accumulation of the mAb was higher and lasted longer after IT injection of WR-mAb1, than after IT administration of 10 µg of J43. The IT injection of viruses induced a massive infiltration of immune cells including activated lymphocytes (CD8⁺ and CD4⁺). Interestingly, in the MCA 205 tumor model, WR-mAb1 and WR-scFv induced a therapeutic control of tumor growth similar to unarmed WR combined to systemically administered J43 and superior to that obtained with an unarmed WR. These results pave the way for next generation of oncolytic vaccinia armed with immunomodulatory therapeutic proteins such as mAbs.

Naloxone/alum mixture a potent adjuvant for HIV-1 vaccine: induction of cellular and poly-isotypic humoral immune responses

In the present study we used a fusion peptide from HIV-1 p24 and Nef as vaccine model and adjuvant activity of Naloxone/alum mixture was evaluated in a peptide vaccine model. HIV-1 p24-Nef fusion peptide was synthesized. Female BALB/c mice were divided into five groups. The first group immunized subcutaneously with the p24-Nef fusion peptide adjuvanted with Naloxone/alum mixture and boosted with same protocol. The second was immunized with fusion peptide adjuvanted in alum. The control groups were injected with NLX (Group 3), Alum (Group 4), or PBS (Groups 5) under the same conditions. To determine the type of induced immune response, sera and splenocytes were analyzed by commercial ELISA method for total IgG and isotypes and cytokine secretion (IL-4 & IFN-γ), respectively. We have also used the ELISPOT assay to monitor changes in the frequency of IFN-γ-producing T cells. The proliferation of T cells was assessed using Brdu method and T-cell cytotoxicity was assessed with CFSE method. Immunization of mice with HIV-1 p24-Nef fusion peptide formulated in Naloxone/alum mixture significantly increased lymphocyte proliferation and shifted cytokine responses toward Th1 profile compared to all other groups. Analysis of humoral immune responses revealed that administration of HIV-1 p24-Nef fusion peptide with Naloxone/alum mixture significantly increased specific IgG responses and also increased IgG1,IgG2a, IgG2b, IgG3, and IgM vs. alum-adjuvanted vaccine groups. Naloxone/alum mixture as an adjuvant could improve cellular and humoral immune response for HIV vaccine model and this adjuvant maybe useful for HIV vaccine model in human clinical trial.

Hydrogel dual delivered celecoxib and anti-PD-1 synergistically improve antitumor immunity

Two major challenges facing cancer immunotherapy are the relatively low therapeutic efficacy and the potential side effects. New drug delivery system and efficient drug combination are required to overcome these challenges. We utilize an alginate hydrogel system to locally deliver 2 FDA-approved drugs, celecoxib and programmed death 1 (PD-1) monoclonal antibody (mAb), to treat tumor-bearing mice. In two cancer models, B16-F10 melanoma and 4T1 metastatic breast cancer, the alginate hydrogel delivery system significantly improves the antitumor activities of celecoxib (CXB), PD-1 mAb, or both combined. These effects are associated with the sustained high concentrations of the drugs in peripheral circulation and within tumor regions. Strikingly, the simultaneous dual local delivery of celecoxib and PD-1 from this hydrogel system synergistically enhanced the presence of CD4+inteferon (IFN)-γ+ and CD8+IFN-γ+ T cells within the tumor as well as in the immune system. These effects are accompanied with reduced CD4+FoxP3+ regulatory T cells (Tregs) and myeloid derived suppressor cells (MDSCs) in the tumor, reflecting a weakened immuosuppressive response. Furthermore, this combinatorial therapy increases the expression of two anti-angiogenic chemokines C-X-C motif ligand (CXCL) 9 and CXCL10, and suppresses the intratumoral production of interleukin (IL)-1, IL-6, and cycloxygenase-2 (COX2), suggesting a dampened pro-tumor angiogenic and inflammatory microenvironment. This alginate-hydrogel-mediated, combinatorial therapy of celecoxib and PD-1 mAb provides a potential valuable regimen for treating human cancer.

Radiotherapy and toll-like receptor agonists

The clinical successes of CTLA4 and PD-1 immune checkpoint blockade in aggressive malignancies such as metastatic melanoma and non-small cell lung carcinoma inaugurate a new era in oncology. Indeed, as opposed to tumor-targeted therapies, it is now clear that immune-targeted therapies designed to enhance the antitumor immune response are a relevant strategy to obtain long-term tumor responses. Interestingly, the study of tumor cell death biology has recently revealed that part of radiotherapy efficacy relies on its ability to trigger an immune response against tumor cells. This "immunogenic cell death" partly relies on the generation of damage-associated molecular patterns, which can stimulate immune sensors such as toll-like receptors. Tumor radiation therapy can therefore be envisioned as a strategy to perform an in situ immunization because it can initiate the release of tumor-associated antigens, deplete immune suppressors, and stimulate antigen-presenting cells via endogenous release of toll-like receptor agonists. Moreover, combinations of radiotherapy with immune checkpoint antibodies are synergistic in preclinical models. The translation of these observations in the clinic is ongoing in early phase I/II trials.

Intratumoral immunotherapy for melanoma

Selection of suitable tumor-associated antigens is a major challenge in the development of effective cancer vaccines. Intratumoral (i.t.) immunotherapy empowers the immune system to mount T cell responses against tumor-associated antigens which are most immunogenic. To mediate systemic tumor regression, i.t. immunotherapy must generate systemic T cell responses that can target distant metastases beyond the initially treated tumor mass. Now that promising preclinical results and some initial success in clinical trials have been obtained, we here review i.t. immunotherapy-related preclinical and clinical studies, their mechanisms of action and future prospects.

Introduction to the role of the immune system in melanoma

The concept of immunosurveillance of cancer has been widely accepted for many years, but only recently have the precise mechanisms of tumor-host immune interactions been revealed. Inflammatory and immune reactions play a role in melanomagenesis, and may contribute to the eradication of tumor as well as potentiating its growth and proliferation. Studies of the role of tumor-immune system interactions are providing insights into the pathogenesis and opportunities for highly effective therapeutic strategies. Some patients, even with advanced disease, are now cured with immunotherapy, and increasing numbers of such cures are likely in future.

Targeted localized use of therapeutic antibodies: a review of non-systemic, topical and oral applications

Therapeutic antibodies provide important tools in the "medicine chest" of today's clinician for the treatment of a range of disorders. Typically monoclonal or polyclonal antibodies are administered in large doses, either directly or indirectly into the circulation, via a systemic route which is well suited for disseminated ailments. Diseases confined within a specific localized tissue, however, may be treated more effectively and at reduced cost by a delivery system which targets directly the affected area. To explore the advantages of the local administration of antibodies, we reviewed current alternative, non-systemic delivery approaches which are in clinical use, being trialed or developed. These less conventional approaches comprise: (a) local injections, (b) topical and (c) peroral administration routes. Local delivery includes intra-ocular injections into the vitreal humor (i.e. Ranibizumab for age-related macular degeneration), subconjunctival injections (e.g. Bevacizumab for corneal neovascularization), intra-articular joint injections (i.e. anti-TNF alpha antibody for persistent inflammatory monoarthritis) and intratumoral or peritumoral injections (e.g. Ipilimumab for cancer). A range of other strategies, such as the local use of antibacterial antibodies, are also presented. Local injections of antibodies utilize doses which range from 1/10th to 1/100th of the required systemic dose therefore reducing both side-effects and treatment costs. In addition, any therapeutic antibody escaping from the local site of disease into the systemic circulation is immediately diluted within the large blood volume, further lowering the potential for unwanted effects. Needle-free topical application routes become an option when the condition is restricted locally to an external surface. The topical route may potentially be utilized in the form of eye drops for infections or corneal neovascularization or be applied to diseased skin for psoriasis, dermatitis, pyoderma gangrenosum, antibiotic resistant bacterial infections or ulcerated wounds. Diseases confined to the gastrointestinal tract can be targeted directly by applying antibody via the injection-free peroral route. The gastrointestinal tract is unusual in that its natural immuno-tolerant nature ensures the long-term safety of repeatedly ingesting heterologous antiserum or antibody materials. Without the stringent regulatory, purity and clean room requirements of manufacturing parenteral (injectable) antibodies, production costs are minimal, with the potential for more direct low-cost targeting of gastrointestinal diseases, especially with those caused by problematic antibiotic resistant or toxigenic bacteria (e.g. Clostridium difficile, Helicobacter pylori), viruses (e.g. rotavirus, norovirus) or inflammatory bowel disease (e.g. ulcerative colitis, Crohn's disease). Use of the oral route has previously been hindered by excessive antibody digestion within the gastrointestinal tract; however, this limitation may be overcome by intelligently applying one or more strategies (i.e. decoy proteins, masking therapeutic antibody cleavage sites, pH modulation, enzyme inhibition or encapsulation). These aspects are additionally discussed in this review and novel insights also provided. With the development of new applications via local injections, topical and peroral routes, it is envisaged that an extended range of ailments will increasingly fall within the clinical scope of therapeutic antibodies further expanding this market.

Curing mice with large tumors by locally delivering combinations of immunomodulatory antibodies

PURPOSE

Immunomodulatory mAbs can treat cancer, but cures are rare except for small tumors. Our objective was to explore whether the therapeutic window increases by combining mAbs with different modes of action and injecting them into tumors.

EXPERIMENTAL DESIGN

Combinations of mAbs to CD137/PD-1/CTLA-4 or CD137/PD-1/CTLA-4/CD19 were administrated intratumorally to mice with syngeneic tumors (B16 and SW1 melanoma, TC1 lung carcinoma), including tumors with a mean surface of approximately 80 mm(2). Survival and tumor growth were assessed. Immunologic responses were evaluated using flow cytometry and qRT-PCR.

RESULTS

More than 50% of tumor-bearing mice had complete regression and long-term survival after tumor injection with mAbs recognizing CD137/PD-1/CTLA-4/CD19 with similar responses in three models. Intratumoral injection was more efficacious than intraperitoneal injection in causing rejection also of untreated tumors in the same mice. The three-mAb combination could also induce regression, but was less efficacious. There were few side effects, and therapy-resistant tumors were not observed. Transplanted tumor cells rapidly caused a Th2 response with increased CD19 cells. Successful therapy shifted this response to the Th1 phenotype with decreased CD19 cells and increased numbers of long-term memory CD8 effector cells and T cells making IFNγ and TNFα.

CONCLUSIONS

Intratumoral injection of mAbs recognizing CD137/PD-1/CTLA-4/CD19 can eradicate established tumors and reverse a Th2 response with tumor-associated CD19 cells to Th1 immunity, whereas a combination lacking anti-CD19 is less effective. There are several human cancers for which a similar approach may provide clinical benefit.

Rapid rebound of the Treg compartment in DEREG mice limits the impact of Treg depletion on mycobacterial burden, but prevents autoimmunity

The development of an effective vaccine against tuberculosis (Tb) represents one of the major medical challenges of this century. Mycobacterium bovis Bacille Calmette-Guerin (BCG), the only vaccine available at present, is mostly effective at preventing disseminated Tb in children, but shows variable protection against pulmonary Tb, the most common form in adults. The reasons for this poor efficacy are not completely understood, but there is evidence that T regulatory cells (Tregs) might be involved. Similarly, Tregs have been associated with the immunosuppression observed in patients infected with Tb and are therefore believed to play a role in pathogen persistence. Thus, Treg depletion has been postulated as a novel strategy to potentiate M. bovis BCG vaccination on one side, while on the other, employed as a therapeutic approach during chronic Tb infection. Yet since Tregs are critically involved in controlling autoimmune inflammation, elimination of Tregs may therefore also incur the danger of an excessive inflammatory immune response. Thus, understanding the dynamics and function of Tregs during mycobacterial infection is crucial to evaluate the potential of Treg depletion as a medical option. To address this, we depleted Tregs after infection with M. bovis BCG or Mycobacterium tuberculosis (Mtb) using DEREG mice, which express the diphtheria toxin (DT) receptor under the control of the FoxP3 locus, thereby allowing the selective depletion of FoxP3⁺ Tregs. Our results show that after depletion, the Treg niche is rapidly refilled by a population of DT-insensitive Tregs (diTregs) and bacterial load remains unchanged. On the contrary, impaired rebound of Tregs in DEREG × FoxP3^GFP mice improves pathogen burden, but is accompanied by detrimental autoimmune inflammation. Therefore, our study provides the proof-of-principle that, although a high degree of Treg depletion may contribute to the control of mycobacterial infection, it carries the risk of autoimmunity.

Poly (γ-glutamic acid) based combination of water-insoluble paclitaxel and TLR7 agonist for chemo-immunotherapy

Advanced anti-cancer regimens are being introduced for more effective cancer treatment with improved life expectancy. In this research, immuno-stimulating agent toll-like receptor-7 (TLR-7) agonist-imiquimod and low dose chemotherapeutic agent-paclitaxel were synergized to demonstrate tumor therapy along with anti-tumor memory effect. Both therapeutic agents being water insoluble were dispersed in water with the help of water soluble polymer: poly (γ-glutamic acid) (γ-PGA) using a co-solvent systems leading to formation of micro-dispersions of drugs. Paclitaxel and imiquimod formed crystalline microstructures in the size range of 2-3 μm and were stably dispersed in γ-PGA matrix for more than 6 months. Paclitaxel and combination of paclitaxel and imiquimod had significant tumor killing effect in-vitro on various tumor cell lines, while antigen presenting cells (dendritic cells-DCs) treated with the same concentration of imiquimod along with the combination led to enhanced proliferation (250%). In DCs, enhanced secretion of pro-inflammatory and Th1 cytokines was observed in cells co-treated with paclitaxel and imiquimod dispersed in γ-PGA. When administered by intra-tumoral injection in mouse melanoma tumor model, the treatment with combination exemplified drastic inhibition of tumor growth leading to 70% survival as compared to individual components with 0% survival at day 41. The anti-tumor response generated was also found to have systemic memory response since the vaccinated mice significantly deferred secondary tumor development at distant site 6 weeks after treatment. The relative number and activation status of DCs in-vivo was found to be dramatically increased in case of mice treated with combination. The dramatic inhibition of tumor treated with combination is expected to be mediated by both chemotherapeutic killing of tumor cells followed by uptake of released antigen by the DCs and due to enhanced proliferation and activation of the DCs.

Local CTLA4 blockade effectively restrains experimental pancreatic adenocarcinoma growth in vivo

Antibody-mediated blockade of CTLA4 has been shown to be effective in treating a select group of patients with late-stage melanoma. The precise mechanism underlying the clinical activity of CTLA4 immunotherapy is poorly understood, although recent experimental findings indicate that antibody-mediated depletion of regulatory T cells (Tregs) in the tumor microenvironment plays a key role in efficacious antitumor responses. In the current study, we used an experimental model of pancreatic adenocarcinoma to compare the antitumor efficacy of peritumoral low-dose anti-CTLA4 monoclonal antibody (mAb) administration to that of a commonly utilized systemic high-dose anti-CTLA4 regimen. We selected pancreatic adenocarcinoma as it presents a particular challenge to clinicians due to its aggressive behavior, metastatic spread and limited treatment options. Furthermore, Fc gamma receptor (FcγR)-dense myeloid cells commonly infiltrate pancreatic tumors, such that these tumor types exhibit increased susceptibility to CTLA4 antibody-targeted Treg depletion via antibody-dependent cell-mediated cytotoxicity (ADCC). Locally administered anti-CTLA4 mAb effectively reduced tumor growth at a low dose and no additional anti-tumor effects were apparent when increasing the dose or number of injections. No significant difference in overall survival was seen when comparing locally administered low-dose with standard systemic high-dose CTLA4 blockade therapy, and both delivery routes led to increased tumor-infiltrating effector T cells and reduced Treg cells. As opposed to low-dose peritumoral treatment, high-dose systemic therapy stimulated the accumulation of Tregs in secondary lymphoid organs, an effect that could potentially counteract the antitumor immunotherapeutic benefit of CTLA4 blockade. Our study confirms previous findings that local administration of low-dose anti-CTLA4 antibody generates sustained antitumor effects and provides rationale to devise ultrasound-guided intratumoral anti-CTLA4 antibody injection regimens to treat patients with pancreatic adenocarcinoma and other types of solid tumors. In support, clinical relevancy could include reduced immune-related adverse events by limiting systemic antibody spread to immune cell-dense organs.