Intratumoral delivery of vector mediated IL-2 in combination with vaccine results in enhanced T cell avidity and anti-tumor activity

Combining computational and experimental biology to develop therapeutically valuable IL2 muteins

High-dose IL2, first approved in 1992, has been used in the treatment of advanced renal cell carcinoma and melanoma. In these indications, IL2 induces long lasting objective responses in 5% to 20% of patients. However, toxicity and the unexpected expansion of regulatory T cells (Tregs) have limited its practical use and therapeutic impact, respectively. At the Center of Molecular Immunology in Havana, Cuba, a project was launched in 2005 to rationally design IL2 muteins that could be deployed in the therapy of cancer. The basic goal was to uncouple the pleiotropic effect of IL2 on different immune T cells, to obtain a mutein with a therapeutic index that was better than that achieved with wild type (wt) IL2. Using a combination of computational and experimental biology approaches, we predicted and developed two novel IL2 muteins with therapeutic potential. The first, designated no-alpha mutein, is an agonist of IL2R signaling with a reduced ability to expand Treg in vivo. In mice, the no-alpha mutein IL2 has higher antitumor activity and lower toxicity than wt IL2. It represents a potential best-in-class drug that has begun phase I/II clinical trials in solid tumors. The second, designated no-gamma mutein, is an antagonist of IL2R signaling, with some preferential affinity for Tregs. This mutein has antitumor activity in mice that likely derives from its ability to reduce Treg accumulation in vivo. It represents a first-in-class drug that offers a novel strategy to inhibit Treg activity in vivo.

A combination trial of vaccine plus ipilimumab in metastatic castration-resistant prostate cancer patients: immune correlates

We recently reported the clinical results of a Phase I trial combining ipilimumab with a vaccine containing transgenes for prostate-specific antigen (PSA) and for a triad of costimulatory molecules (PROSTVAC) in patients with metastatic castration-resistant prostate cancer. Thirty patients were treated with escalating ipilimumab and a fixed dose of vaccine. Of 24 chemotherapy-naïve patients, 58 % had a PSA decline. Combination therapy did not exacerbate the immune-related adverse events associated with ipilimumab. Here, we present updated survival data and an evaluation of 36 immune cell subsets pre- and post-therapy. Peripheral blood mononuclear cells were collected before therapy, at 13 days and at 70 days post-initiation of therapy, and phenotyped by flow cytometry for the subsets of T cells, regulatory T cells, natural killer cells, and myeloid-derived suppressor cells. Associations between overall survival (OS) and immune cell subsets prior to treatment, and the change in a given immune cell subset 70 days post-initiation of therapy, were evaluated. The median OS was 2.63 years (1.77-3.45). There were trends toward associations for longer OS and certain immune cell subsets before immunotherapy: lower PD-1(+)Tim-3(NEG)CD4EM (P = 0.005, adjusted P = 0.010), higher PD-1(NEG)Tim-3(+)CD8 (P = 0.002, adjusted P = 0.004), and a higher number of CTLA-4(NEG) Tregs (P = 0.005, adjusted P = 0.010). We also found that an increase in Tim-3(+) natural killer cells post- versus pre-vaccination associated with longer OS (P = 0.0074, adjusted P = 0.015). These results should be considered as hypothesis generating and should be further evaluated in larger immunotherapy trials.

Therapeutic cancer vaccines

Therapeutic cancer vaccines have the potential of being integrated in the therapy of numerous cancer types and stages. The wide spectrum of vaccine platforms and vaccine targets is reviewed along with the potential for development of vaccines to target cancer cell "stemness," the epithelial-to-mesenchymal transition (EMT) phenotype, and drug-resistant populations. Preclinical and recent clinical studies are now revealing how vaccines can optimally be used with other immune-based therapies such as checkpoint inhibitors, and so-called nonimmune-based therapeutics, radiation, hormonal therapy, and certain small molecule targeted therapies; it is now being revealed that many of these traditional therapies can lyse tumor cells in a manner as to further potentiate the host immune response, alter the phenotype of nonlysed tumor cells to render them more susceptible to T-cell lysis, and/or shift the balance of effector:regulatory cells in a manner to enhance vaccine efficacy. The importance of the tumor microenvironment, the appropriate patient population, and clinical trial endpoints is also discussed in the context of optimizing patient benefit from vaccine-mediated therapy.

Mathematical Models of the Impact of IL2 Modulation Therapies on T Cell Dynamics

Several reports in the literature have drawn a complex picture of the effect of treatments aiming to modulate IL2 activity in vivo. They seem to promote either immunity or tolerance, probably depending on the specific context, dose, and timing of their application. Such complexity might derive from the pleiotropic role of IL2 in T cell dynamics. To theoretically address the latter possibility, our group has developed several mathematical models for Helper, Regulatory, and Memory T cell population dynamics, which account for most well-known facts concerning their relationship with IL2. We have simulated the effect of several types of therapies, including the injection of: IL2; antibodies anti-IL2; IL2/anti-IL2 immune-complexes; and mutant variants of IL2. We studied the qualitative and quantitative conditions of dose and timing for these treatments which allow them to potentiate either immunity or tolerance. Our results provide reasonable explanations for the existent pre-clinical and clinical data, predict some novel treatments, and further provide interesting practical guidelines to optimize the future application of these types of treatments.

Phase I study of intraprostatic vaccine administration in men with locally recurrent or progressive prostate cancer

The primary end point of this study was to determine the safety and feasibility of intraprostatic administration of PSA-TRICOM vaccine [encoding transgenes for prostate-specific antigen (PSA) and 3 costimulatory molecules] in patients with locally recurrent or progressive prostate cancer. This trial was a standard 3 + 3 dose escalation with 6 patients each in cohorts 4 and 5 to gather more immunologic data. Nineteen of 21 patients enrolled had locally recurrent prostate cancer after definitive radiation therapy, and 2 had no local therapy. All cohorts received initial subcutaneous vaccination with recombinant vaccinia (rV)-PSA-TRICOM and intraprostatic booster vaccinations with recombinant fowlpox (rF)-PSA-TRICOM. Cohorts 3-5 also received intraprostatic rF-GM-CSF. Cohort 5 received additional subcutaneous boosters with rF-PSA-TRICOM and rF-GM-CSF. Patients had pre- and post-treatment prostate biopsies, and analyses of peripheral and intraprostatic immune cells were performed. There were no dose-limiting toxicities, and the maximum tolerated dose was not reached. The most common grade 2 adverse events were fever (38%) and subcutaneous injection site reactions (33%); the single grade 3 toxicity was transient fever. Overall, 19 of 21 patients on trial had stable (10) or improved (9) PSA values. There was a marked increase in CD4+ (p = 0.0002) and CD8+ (p = 0.0002) tumor infiltrates in post- versus pre-treatment tumor biopsies. Four of 9 patients evaluated had peripheral immune responses to PSA or NGEP. Intraprostatic administration of PSA-TRICOM is safe and feasible and can generate a significant immunologic response. Improved serum PSA kinetics and intense post-vaccination inflammatory infiltrates were seen in the majority of patients. Clinical trials examining clinical end points are warranted.

Viral vector-based therapeutic cancer vaccines

Most viruses are naturally immunogenic and can be engineered to express tumor antigen transgenes. Moreover, many types of recombinant viruses have been shown to infect professional antigen-presenting cells, specifically dendritic cells, and express their transgenes. This enhanced presentation of tumor antigens to the immune system has led to an increase in the frequency and avidity of cytotoxic T lymphocytes that target tumor cells expressing the tumor antigen(s) encoded in the vaccine vector. Logistically, recombinant viruses can be produced, administered, and quality controlled more easily compared with other immunotherapy strategies. The intrinsic properties of each virus have distinct advantages and disadvantages, which can determine their applicability in a particular therapeutic setting. The disadvantage of some vectors is the development of host-induced neutralizing antibodies to the vector itself, thus limiting its continued use. The "off-the-shelf" nature of viral vaccine platforms renders them exceptionally suitable for multicenter randomized trials. This review described and discussed the strategies used and results using viral-based vaccines, with emphasis on phases II and III clinical trials. Future directions will involve the evaluation of viral-based vaccines in the adjuvant and neoadjuvant settings, in patients with low burden metastatic disease, and in combination with other forms of therapy including immunotherapy.

Modeling the role of IL2 in the interplay between CD4+ helper and regulatory T cells: studying the impact of IL2 modulation therapies

Several reports in the literature have drawn a complex picture of the effect of treatments aiming to modulate IL2 activity in vivo. They seem to promote indistinctly immunity or tolerance, probably depending on the specific context, dose and timing of their application. Such complexity might derives from the dual role of IL2 on T-cell dynamics. To theoretically address the latter possibility, we develop a mathematical model for helper, regulatory and memory T-cells dynamics, which account for most well-known facts relative to their relationship with IL2. We simulate the effect of three types of therapies: IL2 injections, IL2 depletion using anti-IL2 antibodies and IL2/anti-IL2 immune complexes injection. We focus in the qualitative and quantitative conditions of dose and timing for these treatments which allow them to potentate either immunity or tolerance. Our results provide reasonable explanations for the existent pre-clinical and clinical data and further provide interesting practical guidelines to optimize the future application of these types of treatments. Particularly, our results predict that: (i) Immune complexes IL2/anti-IL2 mAbs, using mAbs which block the interaction of IL2 and CD25 (the alpha chain of IL2 receptor), is the best option to potentate immunity alone or in combination with vaccines. These complexes are optimal when a 1:2 molar ratio of mAb:IL2 is used and the mAbs have the largest possible affinity; (ii) Immune complexes IL2/anti-IL2 mAbs, using mAbs which block the interaction of IL2 and CD122 (the beta chain of IL2 receptor), are the best option to reinforce preexistent natural tolerance, for instance to prevent allograft rejection. These complexes are optimal when a 1:2 molar ratio of mAb:IL2 is used and the mAbs have intermediate affinities; (iii) mAbs anti-IL2 can be successfully used alone to treat an ongoing autoimmune disorder, promoting the re-induction of tolerance. The best strategy in this therapy is to start treatment with an initially high dose of the mAbs (one capable to induce some immune suppression) and then scales down slowly the dose of mAb in subsequent applications.

Cytokine-armed vaccinia virus infects the mesothelioma tumor microenvironment to overcome immune tolerance and mediate tumor resolution

Intratumoral (i.t.) administration of cytokine genes expressed by viral vectors represents a rational approach that induces cytokine secretion at the site they are needed, and i.t. vaccinia virus (VV) has shown promise in mesothelioma patients. However, we and others have shown that the mesothelioma tumor microenvironment includes macrophages, dendritic cells (DCs), and T cells. Therefore, we investigated which of these cell types are infected after exposure to VV or Fowlpox virus (FPV)-cytokine gene constructs. In vitro studies showed that mesothelioma tumor cells were resistant to FPV infection yet highly permissive to infection by VV vectors resulting in significant cytokine production and impaired proliferation. Macrophages secreted low levels of cytokine suggestive of resistance to overt infection. DCs transiently secreted virally derived cytokines, but did not mature during VV infection. VV inhibition of T cell proliferation was rescued by the interleukin (IL)-2 and IL-12 VV constructs. In vivo studies of murine mesotheliomas showed that i.t. injection of the parent VV could not hinder tumor progression. In contrast, the VV-cytokine constructs induced profound tumor regression. These data suggest that i.t. VV-cytokine gene constructs retard tumor growth by infecting mesothelioma cells and targeting the immune system through tumor-infiltrating DC and T cells.

Modeling the role of IL-2 in the interplay between CD4+ helper and regulatory T cells: assessing general dynamical properties

Mathematical models accounting for well-known evidences relating to the dynamics of interleukin 2, helper and regulatory T cells are presented. These models extend an existent model (the so-called cross-regulation model of immunity), by assuming IL-2 as the growth factor produced by helper cells, but used by both helper and regulatory cells to proliferate and survive. Two model variants, motivated by current literature, are explored. The first variant assumes that regulatory cells suppress helper cells by limiting IL-2 production and consuming the available IL-2; i.e. they just trigger competition for IL-2. The second model variant adds to the latter competitive mechanism the direct inhibition of helper cells activation by regulatory cells. The extended models retain key dynamical features of the cross-regulation model. But such reasonable behavior depends on parameter constraints, which happen to be realistic and lead to interesting biological discussions. Furthermore, the introduction of IL-2 in these models breaks the local/specific character of interactions, providing new properties to them. In the extended models, but not in the cross-regulation model, the response triggered by an antigen affects the response to other antigens in the same lymph node. The first model variant predicts an unrealistic coupling of the immune reactions to all the antigens in the lymph node. In contrast, the second model variant allows the coexistent of concomitant tolerant and immune responses to different antigens. The IL-2 derived from an ongoing immune reaction reinforces tolerance to other antigens in the same lymph node. Overall the models introduced here are useful extensions of the cross-regulation formalism. In particular, they might allow future studies of the effect of different IL-2 modulation therapies on CD4+ T cell dynamics.