Targeting resistance to radiation-immunotherapy in cold HNSCCs by modulating the Treg-dendritic cell axis.

BACKGROUND: Numerous trials combining radiation therapy (RT) and immunotherapy in head and neck squamous cell carcinoma (HNSCC) are failing. Using preclinical immune cold models of HNSCC resistant to RT-immune checkpoint inhibitors, we investigate therapeutic approaches of overcoming such resistance by examining the differential microenvironmental response to RT. METHODS: We subjected two HPV-negative orthotopic mouse models of HNSCC to combination RT, regulatory T cells (Treg) depletion, and/or CD137 agonism. Tumor growth was measured and intratumorous and lymph node immune populations were compared among treatment groups. Human gene sets, genetically engineered mouse models DEREG and BATF3-/-, flow and time-of-flight cytometry, RNA-Seq, Treg adoptive transfer studies, and in vitro experiments were used to further evaluate the role of dendritic cells (DCs) and Tregs in these treatments. RESULTS: In MOC2 orthotopic tumors, we find no therapeutic benefit to targeting classically defined immunosuppressive myeloids, which increase with RT. In these radioresistant tumors, supplementing combination RT and Treg depletion with anti-CD137 agonism stimulates CD103+ DC activation in tumor-draining lymph nodes as characterized by increases in CD80+ and CCR7+ DCs, resulting in a CD8 T cell-dependent response. Simultaneously, Tregs are reprogrammed to an effector phenotype demonstrated by increases in interferonγ+, tumor necrosis factorα+, PI3K+, pAKT+ and Eomes+ populations as well as decreases in CTLA4+ and NRP-1+ populations. Tumor eradication is observed when RT is increased to an 8 Gy x 5 hypofractionated regimen and combined with anti-CD25+ anti-CD137 treatment. In a human gene set from oral squamous cell carcinoma tumors, high Treg number is associated with earlier recurrence. CONCLUSIONS: Regulating Treg functionality and DC activation status within the lymph node is critical for generating a T cell effector response in these highly radioresistant tumors. These findings underscore the plasticity of Tregs and represent a new therapeutic opportunity for reprogramming the tumor microenvironment in HNSCCs resistant to conventional radioimmunotherapy approaches.

Computational study for suppression of CD25/IL-2 interaction.

Cancer recurrence presents a huge challenge in cancer patient management. Immune escape is a key mechanism of cancer progression and metastatic dissemination. CD25 is expressed in regulatory T (Treg) cells including tumor-infiltrating Treg cells (TI-Tregs). These cells specially activate and reinforce immune escape mechanism of cancers. The suppression of CD25/IL-2 interaction would be useful against Treg cells activation and ultimately immune escape of cancer. Here, software, web servers and databases were used, at which in silico designed small interfering RNAs (siRNAs), de novo designed peptides and virtual screened small molecules against CD25 were introduced for the prospect of eliminating cancer immune escape and obtaining successful treatment. We obtained siRNAs with low off-target effects. Further, small molecules based on the binding homology search in ligand and receptor similarity were introduced. Finally, the critical amino acids on CD25 were targeted by a de novo designed peptide with disulfide bond. Hence we introduced computational-based antagonists to lay a foundation for further in vitro and in vivo studies.

Basiliximab impairs regulatory T cell (TREG) function and could affect the short-term graft acceptance in children with heart transplantation.

CD25, the alpha chain of the IL-2 receptor, is expressed on activated effector T cells that mediate immune graft damage. Induction immunosuppression is commonly used in solid organ transplantation and can include antibodies blocking CD25. However, regulatory T cells (Tregs) also rely on CD25 for their proliferation, survival, and regulatory function. Therefore, CD25-blockade may compromise Treg protective role against rejection. We analysed in vitro the effect of basiliximab (BXM) on the viability, phenotype, proliferation and cytokine production of Treg cells. We also evaluated in vivo the effect of BXM on Treg in thymectomized heart transplant children receiving BXM in comparison to patients not receiving induction therapy. Our results show that BXM reduces Treg counts and function in vitro by affecting their proliferation, Foxp3 expression, and IL-10 secretion capacity. In pediatric heart-transplant patients, we observed decreased Treg counts and a diminished Treg/Teff ratio in BXM-treated patients up to 6-month after treatment, recovering baseline values at the end of the 12-month follow up period. These results reveal that the use of BXM could produce detrimental effects on Tregs, and support the evidence suggesting that BXM induction could impair the protective role of Tregs in the period of highest incidence of acute graft rejection.

A New Target for Hodgkin Lymphoma - Camidanlumab Tesirine.

PURPOSE OF REVIEW: There are limited treatment options for relapsed/refractory classical Hodgkin lymphoma (cHL) patients who progress on brentuximab vedotin and programmed death-1 inhibitors. Camidanlumab Tesirine (Cami) is a new agent that has shown activity in multiply relapsed/refractory cHL patients. In this review, we provide a comprehensive overview of Cami. RECENT FINDINGS: In phase 1 study of Cami in relapsed/refractory cHL and non-Hodgkin lymphomas (NHL), Cami was noted to be safe with encouraging clinic activity in multiply relapsed/refractory cHL. Treatment-emergent adverse events (TEAEs) were reported in 95% (n = 73 of 77) of patients, while grade 3 TEAEs were reported in 66% (n = 51) of cHL patients. Cami was associated with immune-related adverse events (irAEs) including peripheral sensory neuropathy, Guillain-Barré syndrome (GBS)/radiculopathy, colitis, hypothyroidism, hyperthyroidism, thyroiditis, and pneumonitis. The overall response rate (ORR) and complete (CR) rate were 71%/40% in the cHL cohort (n = 75). In the interim analysis of an ongoing phase 2 study in 2020, Cami demonstrated good clinical efficacy with an ORR/CR rate of 83%/38% among the 47 evaluable cHL patients. The toxicity profile was similar to that seen in the phase 1 study, with no new safety signals.. As the phase 2 study with Cami is continuing to accrue patients and we await the final results, the preliminary results with Cami are encouraging and provide an additional therapeutic option especially for patients with multiply relapsed/refractory cHL and perhaps other hematological malignancies expression CD25.

Regulatory T Cells Maintain Selective Access to IL-2 and Immune Homeostasis despite Substantially Reduced CD25 Function.

IL-2 is a critical regulator of immune homeostasis through its impact on both regulatory T (Treg) and effector T cells. However, the precise role of IL-2 in the maintenance and function of Treg cells in the adult peripheral immune system remains unclear. In this study, we report that neutralization of IL-2 in mice abrogated all IL-2R signaling in Treg cells, but was well tolerated and only gradually impacted Treg cell function and immune homeostasis. By contrast, despite substantially reduced IL-2 sensitivity, Treg cells maintained selective IL-2 signaling and prevented immune dysregulation following treatment with the inhibitory anti-CD25 Ab PC61. Reduction of Treg cells with a depleting version of the same CD25 Ab permitted CD8+ effector T cell proliferation before progressing to more widespread immune dysregulation. Thus, despite severely curtailed CD25 expression and function, Treg cells retain selective access to IL-2 that supports their anti-inflammatory functions in vivo. Ab-mediated targeting of CD25 is being actively pursued for treatment of autoimmune disease and prevention of allograft rejection, and our findings help inform therapeutic manipulation and design for optimal patient outcomes.

Camidanlumab tesirine, an antibody-drug conjugate, in relapsed/refractory CD25-positive acute myeloid leukemia or acute lymphoblastic leukemia: A phase I study.

There is a significant need for improved therapeutics in older patients with acute leukemia. Camidanlumab tesirine is an antibody-drug conjugate against CD25, an antigen expressed in several malignancies, including acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). This open-label, dose-escalation and -expansion study (NCT02588092) assessed the safety, activity, pharmacokinetics (PK), and immunogenicity of camidanlumab tesirine in patients with relapsed/refractory ALL/AML. A total of 35 patients (34 AML and 1 ALL) were enrolled and received camidanlumab tesirine intravenously at 3-92 µg/kg once every three weeks (Q3W, n = 26) or 30 or 37.5 µg/kg every week (QW, n = 9). One dose-limiting toxicity of maculopapular rash occurred in the 30 µg/kg QW group; the maximum tolerated dose was not reached. No additional safety concerns or adverse events (AEs) of interest were identified. The most common (>10 % of patients) Grade ≥3 treatment-emergent AEs were febrile neutropenia (25.7 %), lymphopenia, neutropenia, thrombocytopenia or fatigue (all 14.3 %), pneumonia, increased gamma-glutamyltransferase, and hypophosphatemia (each 11.4 %). No signal for serious immune-related AEs such as Guillain-Barré syndrome/polyradiculopathy was observed and there was no evidence of immunogenicity. PK showed rapid clearance with apparent half-life <2 days for conjugated and total antibody, suggesting that Q3W dosing may be insufficient for therapeutic efficacy, and prompting exploration of a QW schedule. Two patients achieved complete responses with incomplete hematologic recovery; one each at 30 and 37.5 µg/kg QW. The trial was terminated during dose escalation due to programmatic reasons other than safety. Hence, recommended dose was not determined.

Regulatory T Cells License Macrophage Pro-Resolving Functions During Atherosclerosis Regression.

RATIONALE: Regression of atherosclerosis is an important clinical goal; however, the pathways that mediate the resolution of atherosclerotic inflammation and reversal of plaques are poorly understood. Regulatory T cells (Tregs) have been shown to be atheroprotective, yet the numbers of these immunosuppressive cells decrease with disease progression, and whether they contribute to atherosclerosis regression is not known. OBJECTIVE: We investigated the roles of Tregs in the resolution of atherosclerotic inflammation, tissue remodeling, and plaque contraction during atherosclerosis regression. METHODS AND RESULTS: Using multiple independent mouse models of atherosclerosis regression, we demonstrate that an increase in plaque Tregs is a common signature of regressing plaques. Single-cell RNA-sequencing of plaque immune cells revealed that unlike Tregs from progressing plaques that expressed markers of natural Tregs derived from the thymus, Tregs in regressing plaques lacked Nrp1 expression, suggesting that they are induced in the periphery during lipid-lowering therapy. To test whether Tregs are required for resolution of atherosclerotic inflammation and plaque regression, Tregs were depleted using CD25 monoclonal antibody in atherosclerotic mice during apolipoprotein B antisense oligonucleotide-mediated lipid lowering. Morphometric analyses revealed that Treg depletion blocked plaque remodeling and contraction, and impaired hallmarks of inflammation resolution, including dampening of the T helper 1 response, alternative activation of macrophages, efferocytosis, and upregulation of specialized proresolving lipid mediators. CONCLUSIONS: Our data establish essential roles for Tregs in resolving atherosclerotic cardiovascular disease and provide mechanistic insight into the pathways governing plaque remodeling and regression of disease.

Greater T Regulatory Cells in Females Attenuate DOCA-Salt-Induced Increases in Blood Pressure Versus Males.

Hypertension is the most common risk factor for cardiovascular disease, causing over 18 million deaths a year. Although the mechanisms controlling blood pressure (BP) in either sex remain largely unknown, T cells play a critical role in the development of hypertension. Further evidence supports a role for the immune system in contributing to sex differences in hypertension. The goal of the current study was to first, determine the impact of sex on the renal T-cell profiles in DOCA-salt hypertensive males and females and second, test the hypothesis that greater numbers of T regulatory cells (Tregs) in females protect against DOCA-salt-induced increases in BP and kidney injury. Male rats displayed greater increases in BP than females following 3 weeks of DOCA-salt treatment, although increases in renal injury were comparable between the sexes. DOCA-salt treatment resulted in an increase in proinflammatory T cells in both sexes; however, females had more anti-inflammatory Tregs than males. Additional male and female DOCA-salt rats were treated with anti-CD25 to decrease Tregs. Decreasing Tregs significantly increased BP only in females, thereby abolishing the sex difference in the BP response to DOCA-salt. This data supports the hypothesis that Tregs protect against the development of hypertension and are particularly important for the control of BP in females.

Combined CD44- and CD25-Targeted Near-Infrared Photoimmunotherapy Selectively Kills Cancer and Regulatory T Cells in Syngeneic Mouse Cancer Models.

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed and selective cancer treatment that induces necrotic and immunogenic cell death and utilizes a mAb conjugated to a photo-absorber dye, IR700DX, activated by NIR light. Although CD44 is a surface cancer marker associated with drug resistance, anti-CD44-IR700 NIR-PIT results in inhibited cell growth and prolonged survival in multiple tumor types. Meanwhile, CD25-targeted NIR-PIT has been reported to achieve selective and local depletion of FOXP3+CD25+CD4+ regulatory T cells (Treg), which are primary immunosuppressive cells in the tumor microenvironment (TME), resulting in activation of local antitumor immunity. Combined NIR-PIT with CD44- and CD25-targeted agents has the potential to directly eliminate tumor cells and also amplify the immune response by removing FOXP3+CD25+CD4+ Tregs from the TME. We investigated the difference in therapeutic effects of CD44-targeted NIR-PIT alone, CD25-targeted NIR-PIT alone, and the combination of CD44- and CD25-targeted NIR-PIT in several syngeneic tumor models, including MC38-luc, LL/2, and MOC1. The combined NIR-PIT showed significant tumor growth inhibition and prolonged survival compared with CD44-targeted NIR-PIT alone in all tumor models and showed prolonged survival compared with CD25-targeted NIR-PIT alone in MC38-luc and LL/2 tumors. Combined CD44- and CD25-targeted NIR-PIT also resulted in some complete remissions. Therefore, combined NIR-PIT simultaneously targeting cancer antigens and immunosuppressive cells in the TME may be more effective than either type of NIR-PIT alone and may have potential to induce prolonged immune responses in treated tumors.

Model averaging for robust extrapolation in evidence synthesis.

Extrapolation from a source to a target, eg, from adults to children, is a promising approach to utilize external information when data are sparse. In the context of meta-analyses, one is commonly faced with a small number of studies, whereas potentially relevant additional information may also be available. Here, we describe a simple extrapolation strategy using heavy-tailed mixture priors for effect estimation in meta-analysis, which effectively results in a model-averaging technique. The described method is robust in the sense that a potential prior-data conflict, ie, a discrepancy between source and target data, is explicitly anticipated. The aim of this paper is to develop a solution for this particular application to showcase the ease of implementation by providing R code, and to demonstrate the robustness of the general approach in simulations.

CD25 and TGF-ß blockade based on predictive integrated immune ratio inhibits tumor growth in pancreatic cancer.

BACKGROUND: The prognosis of pancreatic ductal adenocarcinoma (PDAC) remains poor due to the difficulty of disease diagnosis and therapy. Immunotherapy has had robust performance against several malignancies, including PDAC. In this study, we aim to analyze the expression of CD8 and FoxP3 on T lymphocytes and TGF-ß expression in tumor tissues, and then analyze the possible clinical significance of these finding in order to find a novel effective immunotherapy target in PDAC using a murine model. METHODS: A tissue microarray using patient PDAC samples was stained and analyzed for associations with clinicopathological characteristics. A preclinical murine model administrated with various immunotherapies were analyzed by growth inhibitor, flow cytometry, enzyme-linked immuno sorbent assay and immunohistochemistry. RESULTS: The infiltrating FoxP3+ regulatory T cells (Tregs) in tumor tissues were associated with survival, while CD8+ tumor infiltrating lymphocytes (TILs) were not. Considering the drawbacks of these measure alone, the number of CD8+ and FoxP3+ T cells were combined to create a new estimated value-integrated immune ratio (IIR), which showed excellent validity in survival risk stratification. IIR was further verified as an independent prognostic factor according to multivariate analysis as well as TGF-ß expression. Association between TGF-ß expression and infiltrating Tregs was also verified. Then, in our preclinical murine model, CD25 and TGF-ß combination blockade had a higher tumor growth inhibitor value. This combination therapy significantly depleted periphery and intra-tumor FoxP3+ Tregs while increasing intra-tumor CD8+ TILs levels compared to controls or anti-TGF-ß monotherapy (p < 0.05). Anti-CD25 monotherapy alone also had the ability to deplete periphery and intra-tumor Tregs (p < 0.05). The excretion of intra-tumor IL-10, TGF-ß was notably lower but higher IFN-γ excretion in this combination immunotherapy. Such combination immunotherapy was further confirmed to synergize with anti-PD-1 monotherapy to improve tumor growth inhibition and cure rates. CONCLUSIONS: The combination of CD25, TGF-ß and PD-1 blockade plays a potentially effective role in inhibiting tumor formation and progression. Our results also provide a strong rational strategy for use of IIR in future immunotherapy clinical trials.

Recovery from acute lung injury can be regulated via modulation of regulatory T cells and Th17 cells.

Acute lung injury (ALI) is a severe inflammatory disease, for which no specific treatment exists. The decreased ratio of regulatory T cells (CD4+ CD25+ FoxP3 Tregs) and Th17 cells is implicated in ALI and inflammation. We here investigated whether maintaining the balance of CD4+ CD25+ Foxp3+ Tregs and Th17 cells can alleviate lung injury. For CD4+ CD25+ FoxP3 Treg depletion, 200 µg of an anti-CD25 antibody was administered intraperitoneally per mouse on days -3 and -1 before lipopolysaccharide (LPS) instillation. And 150 µg of TGF-ß was administered intraperitoneally per mouse on day 0 after LPS instillation. To down-regulate of Th17 cells, 200 µg per mouse of isotype, IL-17 or IL-22 antibodies were injected intraperitoneally into mice at days 0 after LPS instillation. We detected lung morphology; lung wet-to-dry weight ratio; protein concentration, the count of total cells, neutrophils and macrophages, and cytokines in bronchoalveolar lavage fluid (BALF). And we also evaluated the percentage of CD4+ CD25+ Foxp3+ Tregs in lung, and Th17 cells in lung. CD4+ CD25+ Foxp3+ Tregs depletion via anti-CD25 treatment or TGF-ß neutralization delayed recovery of ALI. The prolonged inflammation was mainly dominated by neutrophils, macrophages and Th17 cells. Furthermore, inhibition of Th17 cells via monoclonal antibodies against IL-17 and IL-22 alleviated ALI inflammation by inhibiting the recruitment of neutrophils and macrophages, increasing the number of CD4+ CD25+ Foxp3+ Tregs. Our findings support a critical role for CD4+ CD25+ Foxp3+ Tregs in regulating from ALI pathophysiology, and a potential therapeutic role for the inhibition of Th17 cells in ALI treatment. These findings provide a rationale for treating patients with ALI by modulating CD4+ CD25+ Foxp3+ Tregs and Th17 cells.

CMV-specific Cell-mediated Immunity at 3-month Prophylaxis Withdrawal Discriminates D+/R+ Kidney Transplants at Risk of Late-onset CMV Infection Regardless the Type of Induction Therapy.

BACKGROUND: Whether cytomegalovirus (CMV)-specific cell-mediated immunity (CMI) at prophylaxis cessation predicts D+/R+ kidney transplants at risk of late-onset CMV infection after receiving distinct induction therapies is still not well characterized. METHODS: We prospectively assessed CMV-specific CMI predicting late-onset CMV infection at prophylaxis withdrawal and at earlier time-points, in 96 consecutive D+/R+ patients receiving either anti-interleukin 2-receptor antibody (anti-IL2RA; n = 50) or rabbit antithymoglobulin (n = 46). CMV-specific CMI was evaluated against CMV antigens (IE-1, pp65) using an IFN-γ ELISpot assay. RESULTS: Fourteen (14.6%) of 96 patients developed late-onset CMV infection and 2 (2.1%) of 96 displayed disease. At 3 months, CMV-specific CMI frequencies were significantly lower in patients developing late-onset CMV infection (P < 0.001 for IE-1, P = 0.030 for pp65), regardless the type of induction therapy. Receiver operating characteristic curve analyses showed accurate CMV-specific CMI cutoffs (25 and 130 IFN-γ spots for IE-1 and pp65, respectively) classifying patients into high risk, intermediate risk, or low risk (log-rank = 0.006; hazard ratio, 4.084; 95% confidence interval, 1.431-11.651; P = 0.009), being IE-1 CMI the strongest predictor (odds ratio, 5.554; 95% confidence interval, 1.486-20.766; P = 0.011). Although the profound posttransplant CMV-specific CMI inhibition among rabbit antithymocyte globulin-treated patients precludes its use for risk stratification both before and early after kidney transplant, a similar proportion of at-risk patients could be identified before month 3 within anti-interleukin 2-receptor antibody-treated patients. CONCLUSIONS: Monitoring CMV-specific CMI at 3-month prophylaxis cessation discriminates kidney transplant recipient at risk of late-onset CMV infection, regardless the type of induction therapy.

Improved survival after LTx-associated acute GVHD with mAb therapy targeting IL2RAb and soluble TNFAb: Single-center experience and systematic review.

Acute graft-versus-host disease (GVHD) after liver transplant (LTx) is a rare complication with a high mortality rate. Recently, monoclonal antibody (mAb) treatment, specifically with anti-interleukin 2 receptor antibodies (IL2RAb) and anti-tumor necrosis factor-α antibodies (TNFAb), has gained increasing interest. However, evidence is mostly limited to case reports and the efficacy remains unclear. Here, we describe 5 patients with LTx-associated GVHD from our center and provide the results of our systematic literature review to evaluate the potential therapeutic benefit of IL2RAb/TNFAb treatment. Of the combined population of 155 patients (5 in our center and 150 through systematic search), 24 were given mAb (15.5%)-4 with TNFAb (2.6%) and 17 with IL2RAb (11%) ("mAb group")-and compared with patients who received other treatments (referred to as "no-mAb group"). Two-sided Fisher exact tests revealed a better survival when comparing treatment with mAb versus no-mAb (11/24 vs 27/131; P = .018), TNFAb versus no-mAb (3/4 vs 27/131; P = .034), and IL2RAb versus no-mAb (8/17 vs 27/131; P = .029). This systematic review suggests a beneficial effect of mAb treatment and a promising role for TNFAb and IL2RAb as a first-line strategy to treat LTx-associated acute GVHD.

Daclizumab in multiple sclerosis. / Daclizumab en la esclerosis multiple.

INTRODUCTION: Daclizumab is a monoclonal antibody directed against the CD25 subunit of the interleukin-2 receptor, investigated as a disease-modifying therapy in relapsing-remitting multiple sclerosis. The present review addresses how the drug was developed, the known mechanism of action of the drug and the up-to-date data of efficacy and safety. DEVELOPMENT: Daclizumab has shown superiority in prevention of relapses against placebo and low-dose interferon beta-1a at a level that puts it on par with the rest of current first-line drugs. The effect on the progression of the disease and on neurodegeneration parameters, however, is not clear. On the other hand, it presents safety problems (mainly risk of autoimmunity phenomena including fulminant hepatopathy and encephalitis) that have supposed eventually its withdrawn from marketing. Daclizumab introduces a new mechanism of action through the blocking of a key interleukin in immune regulation and its effect on a population of cells with regulatory ability, such as the NK CD56(bright) cells. CONCLUSIONS: Daclizumab has shown efficacy in slowing the inflammatory process of multiple sclerosis, although the appearance of potentially serious side effects has not allowed its use to significantly impact current clinical practice. The development of new drugs in multiple sclerosis must be contingent on maintaining or improving the risk-benefit profile with respect to those already in use.

TITLE: Daclizumab en la esclerosis multiple.Introduccion. El daclizumab es un anticuerpo monoclonal dirigido contra la subunidad CD25 del receptor de la interleucina-2, investigado como terapia modificadora de la evolucion de la enfermedad en la esclerosis multiple. La presente revision aborda como se desarrollo el farmaco, cual es su mecanismo de accion conocido y los datos que se han obtenido hasta la fecha acerca de su eficacia y seguridad. Desarrollo. El daclizumab ha mostrado superioridad en prevencion de brotes frente a placebo e interferon beta-1a de baja dosis en un nivel que lo situa a la par del resto de farmacos de primera linea actuales. El efecto sobre la progresion de la enfermedad y sobre parametros de neurodegeneracion, no obstante, no esta aclarado. Por otro lado, presenta problemas de seguridad (riesgo de reacciones autoinmunes que incluyen hepatopatia fulminante y encefalitis) que han supuesto finalmente su retirada del mercado. El daclizumab introduce un nuevo mecanismo de accion a traves del bloqueo de una interleucina clave en la regulacion inmune y por su efecto sobre una poblacion de celulas con capacidad reguladora, como son las celulas NK CD56(bright). Conclusiones. El daclizumab ha demostrado eficacia para frenar el proceso inflamatorio de la esclerosis multiple, aunque la aparicion de efectos secundarios potencialmente graves no ha permitido que su uso impacte de manera significativa en la practica clinica actual. El desarrollo de nuevos farmacos en la esclerosis multiple debe estar supeditado a mantener o mejorar el perfil riesgo-beneficio respecto a los ya en uso.

Improving the In Vivo Efficacy of an Anti-Tac (CD25) Immunotoxin by Pseudomonas Exotoxin A Domain II Engineering.

Tac (CD25) is expressed on multiple hematologic malignancies and is a target for cancer therapies. LMB-2 is an extremely active anti-Tac recombinant immunotoxin composed of an Fv that binds to Tac and a 38-kDa fragment of Pseudomonas exotoxin A (PE38). Although LMB-2 has shown high cytotoxicity toward Tac-expressing cancer cells in clinical trials, its efficacy was hampered by the formation of anti-drug antibodies against the immunogenic bacterial toxin and by dose-limiting off-target toxicity. To reduce toxin immunogenicity and nonspecific toxicity, we introduced six point mutations into domain III that were previously shown to reduce T-cell immunogenicity and deleted domain II from the toxin, leaving only the 11aa furin cleavage site, which is required for cytotoxic activity. Although this strategy has been successfully implemented for mesothelin and CD22-targeting immunotoxins, we found that removal of domain II significantly lowered the cytotoxic activity of anti-Tac immunotoxins. To restore cytotoxic activity in the absence of PE domain II, we implemented a combined rational design and screening approach to isolate highly active domain II-deleted toxin variants. The domain II-deleted variant with the highest activity contained an engineered disulfide-bridged furin cleavage site designed to mimic its native conformation within domain II. We found that this approach restored 5-fold of the cytotoxic activity and dramatically improved the MTD. Both of these improvements led to significantly increased antitumor efficacy in vivo We conclude that the next-generation anti-Tac immunotoxin is an improved candidate for targeting Tac-expressing malignancies. Mol Cancer Ther; 17(7); 1486-93. ©2018 AACR.

Regulatory T cells: a potential target in cancer immunotherapy.

Cancer immunotherapy involving blockade of immune checkpoint molecules, such as CTLA-4 and PD-1, has shown remarkable clinical success across several types of malignancies. However, a fraction of patients experience disease progression after treatment; thus, exploring resistant mechanisms for immune checkpoint inhibitors and improving their treatment outcome with additional modalities are of great importance. CD4+ regulatory T (Treg ) cells characterized by expression of the master regulatory transcription factor FOXP3 are a highly immune-suppressive subset of CD4+ T cells that maintain immune homeostasis. Several preclinical and clinical studies suggest that Treg cells hamper immune surveillance against cancer in healthy individuals, prevent the development of effective antitumor immunity in tumor-bearing patients, and promote tumor progression. Therefore, targeting Treg cells should be crucial to improving the treatment outcomes of cancer immunotherapy. Several clinical studies directly or indirectly targeting Treg cells in combination with immune checkpoint inhibitors are ongoing or being planned. Understanding the characteristics and roles of Treg cells in cancer settings could make disease-specific Treg -targeted therapy more efficacious and reduce the incidence of immune-related adverse effects mediated by Treg cell inhibition.

A GMCSF-Neuroantigen Tolerogenic Vaccine Elicits Systemic Lymphocytosis of CD4+ CD25high FOXP3+ Regulatory T Cells in Myelin-Specific TCR Transgenic Mice Contingent Upon Low-Efficiency T Cell Antigen Receptor Recognition.

Previous studies showed that single-chain fusion proteins comprised of GM-CSF and major encephalitogenic peptides of myelin, when injected subcutaneously in saline, were potent tolerogenic vaccines that suppressed experimental autoimmune encephalomyelitis (EAE) in rats and mice. These tolerogenic vaccines exhibited dominant suppressive activity in inflammatory environments even when emulsified in Complete Freund's Adjuvant (CFA). The current study provides evidence that the mechanism of tolerance was dependent upon vaccine-induced regulatory CD25+ T cells (Tregs), because treatment of mice with the Treg-depleting anti-CD25 mAb PC61 reversed tolerance. To assess tolerogenic mechanisms, we focused on 2D2-FIG mice, which have a transgenic T cell repertoire that recognizes myelin oligodendrocyte glycoprotein peptide MOG35-55 as a low-affinity ligand and the neurofilament medium peptide NFM13-37 as a high-affinity ligand. Notably, a single subcutaneous vaccination of GMCSF-MOG in saline elicited a major population of FOXP3+ Tregs that appeared within 3 days, was sustained over several weeks, expressed canonical Treg markers, and was present systemically at high frequencies in the blood, spleen, and lymph nodes. Subcutaneous and intravenous injections of GMCSF-MOG were equally effective for induction of FOXP3+ Tregs. Repeated booster vaccinations with GMCSF-MOG elicited FOXP3 expression in over 40% of all circulating T cells. Covalent linkage of GM-CSF with MOG35-55 was required for Treg induction whereas vaccination with GM-CSF and MOG35-55 as separate molecules lacked Treg-inductive activity. GMCSF-MOG elicited high levels of Tregs even when administered in immunogenic adjuvants such as CFA or Alum. Conversely, incorporation of GM-CSF and MOG35-55 as separate molecules in CFA did not support Treg induction. The ability of the vaccine to induce Tregs was dependent upon the efficiency of T cell antigen recognition, because vaccination of 2D2-FIG or OTII-FIG mice with the high-affinity ligands GMCSF-NFM or GMCSF-OVA (Ovalbumin323-339), respectively, did not elicit Tregs. Comparison of 2D2-FIG and 2D2-FIG-Rag1-/- strains revealed that GMCSF-MOG may predominantly drive Treg expansion because the kinetics of vaccine-induced Treg emergence was a function of pre-existing Treg levels. In conclusion, these findings indicate that the antigenic domain of the GMCSF-NAg tolerogenic vaccine is critical in setting the balance between regulatory and conventional T cell responses in both quiescent and inflammatory environments.

Daclizumab for the treatment of adults with relapsing forms of multiple sclerosis.

INTRODUCTION: The goal of the article is to review the mechanism of action and the use of daclizumab, a humanized monoclonal antibody (mAb) against the alpha subunit of the high affinity interleukin-2 (IL-2) receptor, in the treatment of Multiple Sclerosis (MS). Areas covered: PubMed was searched for the terms 'daclizumab' and 'multiple sclerosis'. The mechanisms of action, pharmacokinetics and pharmacodynamics, major studies, side effects and drug interactions of daclizumab in MS are discussed. Expert commentary: Monthly daclizumab-beta [DAC-beta, formerly daclizumab high yield process (DAC HYP), approved as ZINBRYTA®, which has a different form and structure than an earlier form of daclizumab], is an effective and convenient treatment option for patients with relapsing forms of MS who have failed other treatment, or as a first-line option in highly active MS patients. IL-2 signaling modulation by daclizumab constitutes a novel mechanism of action which may also underlie the adverse and serious adverse events and risk profile of the drug that requires appropriate patient selection, monitoring and risk-mitigation programs.