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Background: Denileukin diftitox (ONTAK) is a diphtheria/IL-2R fusion protein able to deplete regulatory T cells in peripheral blood. Regulatory T cells in the local immune microenvironment have been shown to be associated with poor prognosis in ovarian cancer. This study examined whether denileukin diftitox (ONTAK) could be safely administered intraperitoneal in patients with advanced refractory ovarian cancer and assessed its effects on regulatory T cells and tumor associated cytokines in ascites and peripheral blood., Patients and Methods: A phase I dose escalation study of intraperitoneal denileukin diftitox (ONTAK) enrolled 10 patients with advanced, refractory ovarian carcinoma at 3 doses (5 μg/kg, 15 μg/kg, and 25 μg/kg). Serial CA-125 measurements assessed clinical response. Regulatory T cells were quantified using RT-PCR and cytokine levels measured by Luminex., Results: The maximum tolerated dose was 15 μg/kg with a dose limiting toxicity observed in 1 out of 6 patients in the expansion group. The majority of adverse events were transient grades 1-2. One patient treated at the 25 μg/kg dose experienced cytokine storm with prolonged hospitalization. 3 patients had decreases in CA-125 after treatment but none met criteria for partial response. Treatment with denileukin diftitox (ONTAK) decreased regulatory T cells in peripheral blood and ascites. Treated patients did not show any significant changes in IL-8, TGF-β, sIL2Ra in ascites or peripheral blood., Conclusions: Denileukin diftitox (ONTAK) can be safely administered intraperitoneally to recurrent refractory ovarian cancer patients. Regulatory T cells were reduced in ascites and peripheral blood, but there were no significant changes in cytokine levels., Clinical Trial Registration: ClinicalTrials.gov # NCT00357448., Competing Interests: Declaration of competing interest JBL receives research funding from Merck, AstraZeneca, Precigen, ArsenalBio, Volastra, Nurix, Laekna and Aminex Therapeutics through his institution and is a consultant for Verismo Therapeutics. WRG is a consultant for Corea Therapeutics, Puma Therapeutics, and AstraZeneca. ALC declares associations with Actuate, Amgen, Seagen/Pfizer, Mirati, NuCana, and AstraZeneca. MLD has grant funding from Precigen, Veanna, Bavarian Nordic, and Aston Sci. MLD also holds shares in Epithany and is an inventor on patents held by the University of Washington. The authors declare there are no other competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

In spite of consistent progress at the level of basic research and of clinical treatment, acute myeloid leukemia (AML) still represents an unmet clinical need for adult and pediatric patients. To improve the outcomes of these patients, it is necessary to identify new therapeutic targets. IL3RA (CD123, alpha subunit of the interleukin 3 receptor) is a cell membrane protein overexpressed in several hematologic malignancies, including AML blastic plasmocytoid dendritic cell neoplasms (BPDCN). Given the higher expression of CD123 on leukemic cells compared to normal hematopoietic cells and its low/absent expression on normal hematopoietic stem cells, it appears as a suitable and attractive target for therapy. Various drugs targeting CD123 have been developed and evaluated at clinical level: interleukin-3 conjugated with diphtheria toxin; naked neutralizing anti-CD123 antibodies; drug-antibody conjugates; bispecific antibodies targeting both CD123 and CD3; and chimeric antigen receptor (CAR) T cells engineered to target CD123. Some of these agents have shown promising results at the clinical level, including tagraxofusp (CD123 conjugated with diphtheria toxin) for the treatment of BPDCN and IMGN632 (anti-CD123 drug-conjugate), and flotetuzumab (bispecific anti-CD123 and anti-CD3 monoclonal antibody) for the treatment of AML. However, the therapeutic efficacy of CD123-targeting treatments is still unsatisfactory and must be improved through new therapeutic strategies and combined treatments with other antileukemic drugs.

Denileukin Diftitox (DD) is a recombinant fusion protein of diphtheria toxin (DT) fragments and human interleukin-2 (IL-2). DD binds to IL-2 receptor (IL-2R) expressed on tumor cells and is taken up into the cells. Subsequently, DT fragments with adenosine diphosphate ribosylation enzyme inhibit protein synthesis, then ultimately trigger cell death. DD binds to both high- and intermediate-affinity IL-2Rs via IL-2 domain and inhibits growth of human T-cell lymphomas cell lines. E7777, which contains DD as an active component, has improved purity and an increased percentage of active monomer compared with the approved drug E7272 (ONTAK in the US, not approved in Japan). In the phase I clinical study in Japanese patients with relapsed or refractory peripheral T-cell lymphoma (PTCL) and cutaneous T-cell lymphoma (CTCL), the maximum tolerated dose and recommended dose of E7777 were 9 μg/kg/day (administered on Days 1-5 of each cycle) based on the evaluation of dose-limiting toxicity. In the phase II clinical study, the objective response rate was 36.1%, showing comparable efficacy to existing therapies. E7777 showed anti-tumor activity observed across the range of CD25 expression. Grade 3 or higher adverse events (AE) occurred in 94.6%, and serious AE such as capillary leak syndrome and rhabdomyolysis were reported. Therefore, safety monitoring activities have been continued along with alerting related events. Based on these results, E7777 obtained a new drug approval in Japan in March 2021 for the indication of relapsed or refractory PTCL/CTCL.

Myeloid-derived suppressor cells (MDSCs) are present in elevated numbers in tuberculosis patients and have been found to be permissive for Mycobacterium tuberculosis proliferation. To determine whether depletion of MDSCs may improve host control of tuberculosis, we used a novel diphtheria toxin-based fusion protein DABIL-4 that targets and depletes interleukin 4 (IL-4) receptor-positive cells. We show that DABIL-4 depletes both polymorphonuclear MDSCs and monocytic MDSCs, increases interferon-γ + T cells, and reduces the lung bacillary burden in a mouse tuberculosis model. These results indicate that MDSC-depleting therapies targeting the IL-4 receptor are beneficial in tuberculosis and offer an avenue towards host-directed tuberculosis therapy., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Acute graft-versus-host disease (aGVHD) is a major complication after allogeneic hematopoietic stem cell transplantation (HSCT). Corticosteroid is the first-line treatment for aGVHD, but its response rate is only approximately 50%. At present, no uniformly accepted treatment for steroid-refractory aGVHD (SR-aGVHD) is available. Blocking interleukin-2 receptors (IL-2Rs) on donor T cells using pharmaceutical antagonists alleviates SR-aGVHD. This meta-analysis aimed to compare the efficacy and safety of four commercially available IL-2R antagonists (IL-2RAs) in SR-aGVHD treatment. A total of 31 studies met the following inclusion criteria (1): patients of any race, any sex, and all ages (2); those diagnosed with SR-aGVHD after HSCT; and (3) those using IL-2RA-based therapy as the treatment for SR-aGVHD. The overall response rate (ORR) at any time after treatment with basiliximab and daclizumab was 0.81 [95% confidence interval (CI): 0.74-0.87)] and 0.71 (95% CI: 0.56-0.82), respectively, which was better than that of inolimomab 0.54 (95% CI: 0.39-0.68) and denileukin diftitox 0.56 (95% CI: 0.35-0.76). The complete response rate (CRR) at any time after treatment with basiliximab and daclizumab was 0.55 (95% CI: 0.42-0.68) and 0.42 (95%CI: 0.29-0.56), respectively, which was better than that of inolimomab 0.30 (95% CI: 0.16-0.51) and denileukin diftitox 0.37 (95% CI: 0.24-0.52). The ORR and CRR were better after 1-month treatment with basiliximab and daclizumab than after treatment with inolimomab and denileukin diftitox. The incidence of the infection was higher after inolimomab treatment than after treatment with the other IL-2RAs. In conclusion, the efficacy and safety of different IL-2RAs varied. The response rate of basiliximab was the highest, followed by that of daclizumab. Prospective, randomized controlled trials are needed to compare the efficacy and safety of different IL-2RAs., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Shen, Li, Zhang, Xu, Wang, Liu, Huang, Hong and Mo.)

Purpose: Immunotherapy treats some cancers, but not ovarian cancer. Regulatory T cells (Tregs) impede anti-ovarian cancer immunity but effective human Treg-directed treatments are lacking. We tested Treg depletion with denileukin diftitox (DD) ± IFNα as ovarian cancer immunotherapy., Patients and Methods: Mice with syngeneic ID8 ovarian cancer challenge were treated with DD, IFNα, or both. The phase 0/I trial tested one dose-escalated DD infusion for functional Treg reduction, safety, and tolerability. The phase II trial added IFNα2a to DD if DD alone failed clinically., Results: DD depleted Tregs, and improved antitumor immunity and survival in mice. IFNα significantly improved antitumor immunity and survival with DD. IFNα did not alter Treg numbers or function but boosted tumor-specific immunity and reduced tumor Treg function with DD by inducing dendritic cell IL6. DD alone was well tolerated, depleted functional blood Tregs and improved immunity in patients with various malignancies in phase 0/I. A patient with ovarian cancer in phase 0/I experienced partial clinical response prompting a phase II ovarian cancer trial, but DD alone failed phase II. Another phase II trial added pegylated IFNα2a to failed DD, producing immunologic and clinical benefit in two of two patients before a DD shortage halt. DD alone was well tolerated. Adding IFNα increased toxicities but was tolerable, and reduced human Treg numbers in blood, and function through dendritic cell-induced IL6 in vitro ., Conclusions: Treg depletion is clinically useful but unlikely alone to cure ovarian cancer. Rational treatment agent combinations can salvage clinical failure of Treg depletion alone, even when neither single agent provides meaningful clinical benefit., (©2021 American Association for Cancer Research.)

Epidermal growth factor receptor (EGFR) is often overexpressed in head and neck squamous cell carcinoma (HNSCC) and represents a top candidate for targeted HNSCC therapy. However, the clinical effectiveness of current Food and Drug Administration (FDA)-approved drugs targeting EGFR is moderate, and the overall survival rate for HNSCC patients remains low. Therefore, more effective treatments are urgently needed. In this study, we generated a novel diphtheria toxin-based bivalent human epidermal growth factor fusion toxin (bi-EGF-IT) to treat EGFR-expressing HNSCC. Bi-EGF-IT was tested for in vitro binding affinity, cytotoxicity, and specificity using 14 human EGFR-expressing HNSCC cell lines and three human EGFR-negative cancer cell lines. Bi-EGF-IT had increased binding affinity for EGFR-expressing HNSCC compared with the monovalent version (mono-EGF-IT), and both versions specifically depleted EGFR-positive HNSCC, but not EGFR-negative cell lines, in vitro. Bi-EGF-IT exhibited a comparable potency to that of the FDA-approved EGFR inhibitor, erlotinib, for inhibiting HNSCC tumor growth in vivo using both subcutaneous and orthotopic HNSCC xenograft mouse models. When tested in an experimental metastasis model, survival was significantly longer in the bi-EGF-IT treatment group than the erlotinib treatment group, with a significantly reduced number of metastases compared with mono-EGF-IT. In addition, in vivo off-target toxicities were significantly reduced in the bi-EGF-IT treatment group compared with the mono-EGF-IT group. These results demonstrate that bi-EGF-IT is more effective and markedly less toxic at inhibiting primary HNSCC tumor growth and metastasis than mono-EGF-IT and erlotinib. Thus, the novel bi-EGF-IT is a promising drug candidate for further development., (© 2021 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Adenoviral vectors are superior to plasmid vectors in their gene transport efficiency. The A subunit of the diphtheria toxin (DTA) gene is a popular suicide gene in cancer gene therapy. However, DTA is seldom used in adenoviral therapy due to its great toxicity. The toxicity of DTA is so great that even a single molecule of DTA is enough to kill one cell. To avoid this highly toxic effect on normal cells, DTA should be controlled by tumor-specific promoters. The survivin promoter is a widely used tumor-specific promoter. But genes driven by the survivin promoter show a low level of basal gene expression in non-cancer cells. DTA driven by the survivin promoter in adenoviral vectors may be highly toxic not only to cancer cells but also to normal cells. Therefore, DTA should be attenuated when it is used in adenoviral vectors driven by the survivin promoter. In this study, we compared the three kinds of recombinant adenoviruses that carry DTA or its attenuated forms (DTA176 and DTA197) in the treatment of human lung cancer. The results showed that in comparison with both DTA and DTA176, DTA197 is more suitable for adenoviral cancer therapy controlled by the survivin promoter. In addition, Adsur-DTA197 (DTA197 delivered by an adenoviral vector with the survivin promoter) sensitized human lung cancer cells to cisplatin both in vitro and in vivo . These results indicated that Adsur-DTA197 may be a potential chemosensitizer in cancer therapy.

T regulatory cells (Tregs) are an important T cell population for immune tolerance, prevention of autoimmune diseases and inhibition of antitumor immunity. The tumor-promoting role played by Tregs in cancer has prompted numerous approaches to develop immunotherapeutics targeting Tregs. One approach to depletion of Treg cells is retargeting the highly potent cytotoxic activity of bacterial toxins. These agents capitalize on the well-characterized bacterial toxins, diphtheria toxin and Pseudomonas aeruginosa exotoxin A-both of which harbor membrane translocation domains and enzymatic domains that catalytically halt protein synthesis within intoxicated eukaryotic cells and act at picomolar or subpicomolar concentrations. In this review, we summarize the preclinical and clinical development of several Treg-depleting cancer immunotherapies based on these two bacterial toxins.

Tagraxofusp (tagraxofusp-erzs) [Elzonris™] is an intravenously administered CD123-directed cytotoxin (composed of human interleukin-3 and a truncated diphtheria toxin payload) that was developed by Stemline Therapeutics, Inc. for the treatment of blastic plasmacytoid dendritic cell neoplasm (BPDCN). In December 2018, tagraxofusp received its first global approval in the USA for the treatment of BPDCN in adults and in paediatric patients aged 2 years and older. A centralized registration application for the use of tagraxofusp in patients with BPDCN is under review in the EU. This article summarizes the milestones in the development of tagraxofusp leading to its first global approval for the treatment of BPDCN.

Purpose: To conduct an exploratory cost-effectiveness analysis of systemic treatment options for more advanced cutaneous T-cell lymphoma (CTCL)., Methods: A cost-effectiveness model compared systemic bexarotene, denileukin diftitox, interferon-α, methotrexate, pralatrexate, romidepsin, vorinostat, and extracorporeal photopheresis (ECP) treatment of CTCL. Treatment effectiveness data were extracted from published studies and/or US product labeling. Overall response, the primary effectiveness measure, was defined as the proportion of patients achieving complete or partial response. Costs were based on wholesale acquisition cost (medications) and Medicare reimbursement rates (ECP, medication administration, adverse drug effect treatment). The perspective of the study was from that of a payer., Results: Methotrexate was the lowest cost option [mean $436; standard deviation (SD) $284], followed by interferon-α (mean $32,174; SD $27,582), denileukin difitox (mean $40,107; SD $18,598), and ECP (mean $40,985; SD $45,633). Other treatments had costs greater than $50,000, ranging from vorinostat ($65,958; SD $40,637) to bexarotene ($239,424; SD $178,881). The incremental cost-effectiveness ratio per successfully treated patient was $396,725 (interferon) and $213,416 (ECP). Denileukin diftitox, romidepsin, and vorinostat were less effective and cost more than methotrexate., Conclusion: Methotrexate is the most cost-effective option for CTCL; however, its low cost is offset by its limited effectiveness in advanced stages of CTCL. ECP and interferon appear the next most cost-effective therapies.

Cancer immunotherapy has shown remarkable recent progress. Immune checkpoint blocking antibodies have become the most successful anti-cancer agent class ever developed, with six distinct agents approved since 2011 for a wide variety of cancers. Although age is the biggest risk factor for cancer (aside from selected early-onset pediatric cancers), these agents were tested pre-clinically in young hosts, and there is remarkably little published on the effects of host age on treatment outcomes in pre-clinical studies or human clinical trials. The three principal immune checkpoints against which blocking antibodies have been FDA-approved for human use are CTLA-4, PD-1 and PD-L1. We used a mouse model of transplantable, orthotopic B16 melanoma to test age effects of treatments with anti-CTLA-4, anti-PD-1 and anti-PD-L1 antibodies. All three agents were highly effective in treating young tumor-bearing hosts as expected. Anti-PD-L1 as a single agent had no effect on tumor growth in aged hosts, anti-CTLA-4 had detectable, modest effects and anti-PD-1 was essentially as effective in aged as in young hosts, the first single agent we have identified not to lose efficacy with age in this model. Other important differences in young versus aged hosts included lack of anti-CTLA-4-mediated depletion of intratumor regulatory T cells in aged hosts and poorer ability of all three agents to activate T cells in aged versus young hosts. Anti-CTLA-4 efficacy appeared to improve when combined with anti-PD-L1. Regulatory T cell depletion with FDA-approved denileukin diftitox did not improve treatment by any single agent. Aged mice tolerated treatments as well as young mice without obvious toxicities at equivalent doses., (Copyright © 2017. Published by Elsevier Inc.)

The homologous recombination (HR) pathway is a promising target for cancer therapy as it is frequently upregulated in tumors. One such strategy is to target tumors with cancer-specific, hyperactive promoters of HR genes including RAD51 and RAD51C. However, the promoter size and the delivery method have limited its potential clinical applications. Here we identified the ~2.1 kb promoter of XRCC2, similar to ~6.5 kb RAD51 promoter, as also hyperactivated in cancer cells. We found that XRCC2 expression is upregulated in nearly all types of cancers, to a degree comparable to RAD51 while much higher than RAD51C. Further study demonstrated that XRCC2 promoter is hyperactivated in cancer cell lines, and diphtheria toxin A (DTA) gene driven by XRCC2 promoter specifically eliminates cancer cells. Moreover, lentiviral vectors containing XRCC2 promoter driving firefly luciferase or DTA were created and applied to subcutaneous HeLa xenograft mice. We demonstrated that the pXRCC2-luciferase lentivirus is an effective tool for in vivo cancer visualization. Most importantly, pXRCC2-DTA lentivirus significantly inhibited the growth of HeLa xenografts in comparison to the control group. In summary, our results strongly indicate that virus-mediated delivery of constructs built upon the XRCC2 promoter holds great potential for tumor diagnosis and therapy.

E7777, a recombinant cytotoxic fusion protein comprising diphtheria toxin fragments A and B and human interleukin-2, shares an amino acid sequence with denileukin diftitox but has improved purity and an increased percentage of active protein monomer species. A phase I study was carried out to evaluate the tolerability, safety, pharmacokinetics, and antitumor activity of E7777 in Japanese patients with relapsed/refractory peripheral and cutaneous T-cell lymphoma. E7777 (6, 12, and expanded 9 μg/kg/day) was given to 13 patients by i.v. infusion on five consecutive days per 21-day cycle. Dose-limiting toxicities, including increased alanine aminotransferase, hyponatremia (n = 2), hypokalemia, lymphopenia, fatigue, hypoalbuminemia, rash, and increased lipase (n = 1), were observed in all three patients in the 12 μg/kg/day cohort, whereas two of six patients in the 9 μg/kg/day cohort showed decreased appetite or fatigue. The maximum tolerated and recommended dose of E7777 was 9 μg/kg/day for five consecutive days per 21-day cycle. The objective response rate was 38% (5/13) and did not appear to depend on tumor expression of CD25. E7777 was well tolerated, assuming careful management of adverse events during treatment, and preliminary but clinically meaningful antitumor activity was observed. Subsequent studies of E7777 for T-cell lymphomas are warranted. This study was registered with www.ClinicalTrials.gov (NCT1401530)., (© 2018 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)

Immunotoxins are a novel class of cancer therapeutics that contains a cytotoxic agent fused to a targeting moiety. Various toxic agents from different sources are used in immunotoxin development, including bacterial, plant and human origin cytotoxic elements. Although bacterial and plant-derived toxins are highly toxic and commonly used in immunotoxins, their immunogenicity for human restricted their application in cancer therapy. Here, we discuss the advantages and limitations of bacterial toxins such as Pseudomonas and Diphtheria toxins, plant toxins such as ricin and gelonin, and some endogenous protein of human origin such as RNases and Granzymes. This article will also review different generations of immunotoxins with special focus on immunotoxins which are under clinical trials or approved for clinical use. Finally, current deimmunization strategies for development of new less-immunogenic recombinant immunotoxins will be discussed., Abbreviations: mAbs: Monoclonal antibodies; EF2: elongation factor 2; ITs: Immunotoxins; DT: Diphtheria toxin; PE: Pseudomonas exotoxin; dgA: de-glycosylated A-chain of ricin; rGel: recombinant de-glycosylated form of gelonin; NKC: natural killer cells; HTR: human transferrin receptor; EGF: epidermal growth factor; GM-CSF: granulocyte-macrophage colony-stimulating factor; DAB389: truncated Diphtheria toxin; B-CCL: B-cell chronic lymphocytic leukemia; RCC: renal cell carcinoma; GVHD: Graft-versus-host disease; EGFR: epidermal growth factor receptor; AML: acute myeloid leukemia; Fab: fragment antigen-binding; dsFv: disulfide-stabilized fragment variable; scFv: single-chain fragment variable; B-ALL: B-lineage Acute Lymphoblastic Leukemia; Fv: fragment variable; HCL: hairy cell leukemia; IL-2R: Interleukin-2 receptor; CR: complete response; CLL: chronic lymphocytic leukemia; ATL: adult T-cell leukemia; DARPins: designed Ankyrin repeat proteins; pmol: picomolar; HAMA: human-anti mouse antibody.

Host-directed therapies that augment host immune effector mechanisms may serve as important adjunctive therapies for tuberculosis treatment. We evaluated the activity of denileukin diftitox in an acute mouse model of tuberculosis (TB) infection and analyzed the cellular composition and bacterial burden in lungs and spleens. These in vivo studies show that denileukin diftitox potentiates standard TB treatment in the mouse model, an effect which may be due to depletion of T-regulatory and myeloid-derived suppressor cells during TB infection. Our results indicate that denileukin diftitox and other suppressor cell-depleting therapies may be useful adjunctive, host-directed therapies for TB., (© The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

CD19 is expressed on normal and neoplastic B cells and is a promising target for immunotherapy. However, there is still an unmet need to further develop novel therapeutic drugs for the treatment of the refractory/relapsing human CD19 + tumors. We have developed a diphtheria toxin-based anti-human CD19 immunotoxin for targeting human CD19 + tumors. We have constructed three isoforms of the CD19 immunotoxin: monovalent, bivalent, and foldback diabody. In vitro binding affinity and efficacy analysis demonstrated that the bivalent isoform had the highest binding affinity and in vitro efficacy. The in vivo efficacy of the CD19 immunotoxins was assessed using human CD19 + JeKo-1 tumor-bearing NOD/SCID IL-2 receptor γ -/- (NSG) mouse model. In these animals, CD19 immunotoxins significantly prolonged the median survival from 31 days in controls to 34, 36, and 40 days in animals receiving the monovalent isoform, foldback diabody isoform, and bivalent isoform, respectively. The bivalent CD19 immunotoxin is a promising therapeutic drug candidate for targeting relapsing/refractory human CD19 + tumors., (© 2017 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.)

Through years of evolutionary selection pressures, organisms have developed potent toxins that coincidentally have marked antineoplastic activity. These natural products have been vital for the development of multiagent treatment regimens currently employed in cancer chemotherapy, and are used in the treatment of a variety of malignancies. Therefore, this review catalogs recent advances in natural product-based drug discovery via the examination of mechanisms of action and available clinical data to highlight the utility of these novel compounds in the burgeoning age of precision medicine. The review also highlights the recent development of antibody-drug conjugates and other immunotoxins, which are capable of delivering highly cytotoxic agents previously deemed too toxic to elicit therapeutic benefit preferentially to neoplastic cells. Finally, the review examines natural products not currently used in the clinic that have novel mechanisms of action, and may serve to supplement current chemotherapeutic protocols.

Use of monoclonal antibodies (mAbs) has revolutionized cancer therapy. Approaches targeting specific cellular targets on the malignant cells and in tumor microenvironment have been proved to be successful in hematologic malignancies, including cutaneous lymphomas. mAb-based therapy for cutaneous T-cell lymphoma has demonstrated high response rates and a favorable toxicity profile in clinical trials. Several antibodies and antibody-based conjugates are approved for use in clinical practice, and many more are in ongoing and planned clinical trials. In addition, these safe and effective drugs can be used as pillars for sequential therapies in a rational stepwise manner., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: The novel bispecific ligand-directed toxin (BLT) DT2219 consists of a recombinant fusion between the catalytic and translocation enhancing domain of diphtheria toxin (DT) and bispecific single-chain variable fragments (scFV) of antibodies targeting human CD19 and CD22. We conducted a phase I dose-escalation study to assess the safety, maximum tolerated dose, and preliminary efficacy of DT2219 in patients with relapsed/refractory B-cell lymphoma or leukemia., Experimental Design: DT2219 was administered intravenously over 2 hours every other day for 4 total doses. Dose was escalated from 0.5 μg/kg/day to 80 μg/kg/day in nine dose cohorts until a dose-limiting toxicity (DLT) was observed., Results: Twenty-five patients with mature or precursor B-cell lymphoid malignancies expressing CD19 and/or CD22 enrolled to the study. Patients received median 3 prior lines of chemotherapy and 8 failed hematopoietic transplantation. All patients received a single course of DT2219; one patient was retreated. The most common adverse events, including weight gain, low albumin, transaminitis, and fever were transient grade 1-2 and occurred in patients in higher dose cohorts (≥40 μg/kg/day). Two subjects experienced DLT at dose levels 40 and 60 μg/kg. Durable objective responses occurred in 2 patients; one was complete remission after 2 cycles. Correlative studies showed a surprisingly low incidence of neutralizing antibody (30%)., Conclusions: We have determined the safety of a novel immunotoxin DT2219 and established its biologically active dose between 40 and 80 μg/kg/day ×4. A phase II study exploring repetitive courses of DT2219 is planned., (©2015 American Association for Cancer Research.)

Peripheral T-cell lymphomas (PTCLs) are an uncommon group of lymphoproliferative disorders accounting for approximately 10-15 % of all non-Hodgkin lymphomas (NHL) in Western countries. Although PTCLs are associated with poor prognosis, outcomes vary with disease subtype. The standard of care has been anthracycline-based induction combination chemotherapy, however, with the exception of low-risk ALK-positive anaplastic large cell lymphoma, relapse rates are high. Therefore, consolidation with autologous stem cell transplantation is usually recommended for patients deemed candidates, and with aggressive subtypes. In recent years, a number of novel agents including pralatrexate, histone deacetylase inhibitors, immunotoxins, proteasome inhibitors, aurora kinase inhibitors and the CD30 antibody-drug conjugate brentuximab vedotin, have shown promise in the treatment of PTCLs. Studies are underway to explore the activity of these newer agents used in the frontline setting.

Antibody-drug conjugates (ADCs), drugs developed by conjugation of an anticancer agent to a monoclonal antibody (mAb), have lately attracted attention in cancer therapy because ADCs can directly bind cancer cells and kill them. Although mAbs for ADCs must be internalized by the target cells, few methods are available for screening mAbs for their ability to be internalized by cells. We have developed a recombinant protein, termed DT3C, which consists of diphtheria toxin (DT) lacking the receptor-binding domain but containing the C1, C2, and C3 domains of Streptococcus protein G (3C). When a mAb-DT3C conjugate, which functions in vitro like an ADC, reduces the viability of cancer cells, the mAb being tested must have been internalized by the target cells. DT3C can thus be a tool to identify efficiently and easily mAbs that can be internalized by cells, thereby enhancing the development of promising ADCs., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Peripheral T-cell lymphoma (PTCL) represents a relatively rare group of heterogeneous non-Hodgkin lymphomas with a very poor prognosis. Current therapies, based on historical regimens for aggressive B-cell lymphomas, have resulted in insufficient patient outcomes. The majority of patients relapse rapidly, and current 5-year overall survival rates are only 10-30%. It is evident that new approaches to treat patients with PTCL are required. In recent years, prospective studies in PTCL have been initiated, mainly in patients with relapsed/refractory disease. In some of these, selected histologic subtypes have been evaluated in detail. As a consequence, numerous new therapies have been developed and shown activity in PTCL, including: agents targeting the immune system (e.g. brentuximab vedotin, alemtuzumab, lenalidomide); histone deacetylase inhibitors (romidepsin, belinostat); antifolates (pralatrexate); fusion proteins (denileukin diftitox); nucleoside analogs (pentostatin, gemcitabine); and other agents (e.g. alisertib, plitidepsin, bendamustine, bortezomib). A variety of interesting novel combinations is also emerging. It is hoped that these innovative approaches, coupled with a greater understanding of the clinicopathologic features, pathogenesis, molecular biology, and natural history of PTCL will advance the field and improve outcomes in this challenging group of diseases. This review summarizes the currently available clinical evidence on the various approaches to treating relapsed/refractory PTCL, including the role of stem cell transplantation, with an emphasis on potential new drug therapies., (Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This is the first prospective study of treatment of patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive hematologic malignancy derived from plasmacytoid dendritic cells that typically involves the skin and rapidly progresses to a leukemia phase. Despite being initially responsive to intensive combination chemotherapy, most patients relapse and succumb to their disease. Because BPDCN blasts overexpress the interleukin-3 receptor (IL3R), the activity of SL-401, diptheria toxin (DT)388IL3 composed of the catalytic and translocation domains of DT fused to IL3, was evaluated in BPDCN patients in a phase 1-2 study. Eleven patients were treated with a single course of SL-401 at 12.5 μg/kg intravenously over 15 minutes daily for up to 5 doses; 3 patients who had initial responses to SL-401 received a second course in relapse. The most common adverse events including fever, chills, hypotension, edema, hypoalbuminemia, thrombocytopenia, and transaminasemia were transient. Seven of 9 evaluable (78%) BPDCN patients had major responses including 5 complete responses and 2 partial responses after a single course of SL-401. The median duration of responses was 5 months (range, 1-20+ months). Further studies of SL-401 in BPDCN including those involving multiple sequential courses, alternate schedules, and combinations with other therapeutics are warranted. This trial is registered at clinicaltrials.gov as #NCT00397579., (© 2014 by The American Society of Hematology.)

In this issue of Blood, Bachanova et al describe how modulation of the inhibitory tumor environment may enhance natural killer (NK) cell clinical activity and produce encouraging results in the treatment of refractory acute myeloid leukemia (AML). NK cells are highly proliferative, early responders of the innate immune response that in preclinical models can exert potent activity against a wide range of malignancies, including AML, and across HLA barriers. Considerable efforts have been made to exploit this activity in clinical trials but with only modest success.

Haploidentical natural killer (NK) cell infusions can induce remissions in some patients with acute myeloid leukemia (AML) but regulatory T-cell (Treg) suppression may reduce efficacy. We treated 57 refractory AML patients with lymphodepleting cyclophosphamide and fludarabine followed by NK cell infusion and interleukin (IL)-2 administration. In 42 patients, donor NK cell expansion was detected in 10%, whereas in 15 patients receiving host Treg depletion with the IL-2-diphtheria fusion protein (IL2DT), the rate was 27%, with a median absolute count of 1000 NK cells/μL blood. IL2DT was associated with improved complete remission rates at day 28 (53% vs 21%; P = .02) and disease-free survival at 6 months (33% vs 5%; P < .01). In the IL2DT cohort, NK cell expansion correlated with higher postchemotherapy serum IL-15 levels (P = .002), effective peripheral blood Treg depletion (<5%) at day 7 (P < .01), and decreased IL-35 levels at day 14 (P = .02). In vitro assays demonstrated that Tregs cocultured with NK cells inhibit their proliferation by competition for IL-2 but not for IL-15. Together with our clinical observations, this supports the need to optimize the in vivo cytokine milieu where adoptively transferred NK cells compete with other lymphocytes to improve clinical efficacy in patients with refractory AML. This study is registered at clinicaltrials.gov, identifiers: NCT00274846 and NCT01106950., (© 2014 by The American Society of Hematology.)

We report herein that neuroinvasion by vesicular stomatitis virus (VSV) activates microglia and induces a peripheral dendritic cell (DC)-dependent inflammatory response in the central nervous system (CNS). VSV neuroinvasion rapidly induces multiple brain chemokine and proinflammatory cytokine mRNAs that display bimodal kinetics. Peripheral DC ablation or T cell depletion suppresses the second wave of this response demonstrating that infiltrating T cells are primarily responsible for the bimodal characteristics of this response. The robust infiltrate associated with VSV encephalitis likely depends on sustained production of brain CCL19 and CCR7 expression on infiltrating inflammatory cells., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Cytoreductive surgery and chemotherapy continue to be the mainstay of ovarian cancer treatment. However, as mortality from advanced ovarian cancer remains very high, novel therapies are required to be integrated into existing treatment regimens. Immunotherapy represents an alternative and rational therapeutic approach for ovarian cancer based on a body of evidence supporting a protective role of the immune system against these cancers, and on the clinical success of immunotherapy in other malignancies. Whether or not immunotherapy will have a role in the future management of ovarian cancer is too early to tell, but research in this field is active. This review will discuss recent clinical developments of selected immunotherapies for ovarian cancer which fulfil the following criteria: (i) they are antibody-based, (ii) target a distinct immunological pathway, and (iii) have reached the clinical trial stage. Specifically, the focus is on Catumaxomab (anti-EpCAM×anti-CD3), Abagovomab, Oregovomab (anti-CA125), Daclizumab (anti-CD25), Ipilimumab (anti-CTLA-4), and MXD-1105 (anti-PD-L1). Catumaxomab has reached phase III clinical trials and exhibits promise with reports, showing that it can cause a significant and sustained reduction in ascites. Phase I-III clinical trials continue to be conducted on the other antibodies, some of which have had encouraging reports. We will also provide our perspective on the future of immunotherapy for ovarian cancer, and how it may be best employed in treatment regimens.

In multiple sclerosis (MS) and its rodent model, experimental autoimmune encephalomyelitis (EAE), activated CD4(+) T cells with upregulated IL-2R mediate inflammation and demyelination in the central nervous system (CNS). DAB(389)IL-2, a chimeric fusion protein of IL-2 and diphtheria toxin, inhibits human and rodent IL-2 activated T cells that express the high affinity interleukin-2 receptor. In the present study, DAB(389)IL-2 was used to treat rats with EAE. We wanted to investigate the possibility that DAB(389)IL-2 could prevent tissue destruction within the CNS. We used a suboptimal dose of DAB(389)IL-2 that allowed substantial transmigration of inflammatory cells across the blood-brain barrier. DAB(389)IL-2 inhibited infiltration of CD4(+), CD8(+), CD25(+) and TCR αβ(+) associated mononuclear cells and inflammatory macrophages in the spinal cord on day 13 post-immunization, at the peak of disease. Gene expression study showed that DAB(389)IL-2 treatment suppressed TNF-α and IFN-γ as well as IL-10 cytokine gene expression in the spinal cord of rats with EAE on day 13. DAB(389)IL-2 in vitro treatment suppressed cytotoxicity of MBP-activated T cells from rats with EAE against oligodendrocytes in culture by 66%. Astrocytes were less targeted by MBP activated T cells in vitro. This study suggests that DAB(389)IL-2 directly targets CD4(+) and CD25(+) (IL-2R) T cells and effector T cell function and also indirectly suppresses the activation of macrophage CD169(+) (ED3(+)) and microglia CD11b/c (OX42(+)) populations in the CNS., (© 2013.)

Chimeric protein toxins that act selectively on cells expressing a designated receptor may serve as investigational probes and/or antitumor agents. Here, we report use of the enzyme sortase A (SrtA) to create four chimeric toxins designed to selectively kill cells bearing the tumor marker HER2. We first expressed and purified: (i) a receptor recognition-deficient form of diphtheria toxin that lacks its receptor-binding domain and (ii) a mutated, receptor-binding-deficient form of anthrax-protective antigen. Both proteins carried at the C terminus the sortase recognition sequence LPETGG and a H₆ affinity tag. Each toxin protein was mixed with SrtA plus either of two HER2-recognition proteins--a single-chain antibody fragment or an Affibody--both carrying an N-terminal G₅ tag. With wild-type SrtA, the fusion reaction between the toxin and receptor-recognition proteins approached completion only after several hours, whereas with an evolved form of the enzyme, SrtA*, the reaction was virtually complete within 5 minutes. The four fusion toxins were purified and shown to kill HER2-positive cells in culture with high specificity. Sortase-mediated ligation of binary combinations of diverse natively folded proteins offers a facile way to produce large sets of chimeric proteins for research and medicine., (©2013 AACR.)

Denileukin diftitox (DD), a diphtheria toxin fragment IL-2 fusion protein, is thought to target and kill CD25(+) cells. It is approved for the treatment of cutaneous T-cell lymphoma and is used experimentally for the depletion of regulatory T cells (Treg) in cancer trials. Curiously enough, clinical effects of DD did not strictly correlate with CD25 expression, and Treg depletion was not confirmed unambiguously. Here, we report that patients with melanoma receiving DD immediately before a dendritic cell (DC) vaccine failed to develop a tumor-antigen-specific CD4 and CD8 T-cell immune response even after repeated vaccinations. Analyzing the underlying mechanism, so far we found unknown effects of DD. First, DD modulated DCs toward tolerance by downregulating costimulatory receptors such as CD83 and CD25 while upregulating tolerance-associated proteins/pathways including Stat-3, β-catenin, and class II transactivator-dependent antigen presentation. Second, DD blocked Stat3 phosphorylation in maturing DCs. Third, only activated, but not resting, Treg internalized DD and were killed. Conversely, resting Treg showed increased survival because of DD-mediated antiapoptotic IL-2 signaling. We conclude that DD exerts functions beyond CD25(+) cell killing that may affect their clinical use and could be tested for novel indications.

Targeted toxins (TT) are molecules that bind cell surface antigens or receptors such as the transferrin or interleukin-13 receptor that are overexpressed in cancer. After internalization, the toxin component kills the cell. These recombinant proteins consist of an antibody or carrier ligand coupled to a modified plant or bacterial toxin such as diphtheria toxin (DT). These fusion proteins are very effective against brain cancer cells that are resistant to radiation therapy and chemotherapy. TT have shown an acceptable profile for toxicity and safety in animal studies and early clinical trials have demonstrated a therapeutic response. This review summarizes the characteristics of DT-based TT, the animal studies in malignant brain tumors and early clinical trial results. Obstacles to the successful treatment of brain tumors include poor penetration into tumor, the immune response to DT and cancer heterogeneity.

Background: We aimed to determine duration of response in patients with CTCL treated using DD who experienced partial response, complete clinical response, or complete response., Patients and Methods: Data from 3 phase III studies were pooled. Patients received up to 8 courses of 9 or 18 μg/kg intravenous DD daily for 5 days every 21 days, or placebo. Data on DD-treated patients were analyzed by dose and CD25 status. Kaplan-Meier product limit estimates and 95% confidence intervals were calculated for duration of response and time to response., Results: The pooled population comprised 263 DD-treated and 44 placebo-treated patients, and 100 and 7, respectively, had at least a partial response. Median duration of response using DD was 277 days vs. 81 days using placebo. Overall response vs. placebo (n = 7; 16%) as (n = 25; 31%) for DD 9 μg/kg (P = .05), (n = 56; 47%) for DD 18 μg/kg (P = .004), (n = 8; 28%) for re-treated patients (DD 18 μg/kg; P = .21), and (n = 11; 31%) for CD25 low-expression patients (DD 18 μg/kg; P = .14). Overall response rates were similar between patients who did (n = 95; 36%) and did not (n = 105; 40%) develop capillary leak syndrome (CLS); median duration of response was longer in patients who developed CLS, but was not significant (619 vs. 267 days, respectively; P = .28). Adverse events occurred in 98% of DD-treated patients; most frequent were nausea, pyrexia, fatigue, CLS, and rigors., Conclusion: These data indicate a durable response with DD in CTCL, even in heavily pretreated patients and those with CD25 low-expression disease., (Copyright © 2013 Elsevier Inc. All rights reserved.)

This open-label phase III trial, a companion to an earlier placebo-controlled trial, evaluated safety and efficacy of denileukin diftitox (DD) in patients with cutaneous T-cell lymphoma (CTCL) who relapsed after responding to DD primary treatment in the earlier trial. Twenty relapsed patients (stages IA-III) received DD 18 μg/kg/day intravenously on days 1-5 of a 21-day cycle, for ≤ 8 cycles. Efficacy was assessed monthly during the first year then every 3 months. The overall response rate was 40%, mostly partial responses. Nine patients (all baseline stages ≤ IIA) experienced progression. Intent-to-treat median progression-free survival was 205 days, and median duration of response was 274 days. The most common adverse events were nausea, upper respiratory tract infections, fatigue and rigors. Three patients withdrew because of toxicity. This study showed that DD may provide clinically meaningful benefit in patients with CTCL who relapsed after initial response to DD.

Although significant strides have been made in understanding the biology of graft-versus-host disease (GVHD) and its prevention over the last 4 decades, little is known about the different populations of lymphocytes and the changes in response to treatment for this condition. BMT-CTN 0302 was a randomized phase II clinical trial in the Blood and Marrow Transplant Clinical Trials Network that assessed the efficacy of combination therapy with steroids plus pentostatin, mycophenolate mofetil, etanercept, or denileukin diftitox in patients with acute GVHD. Patients enrolled in the study underwent blood analysis by flow cytometry on days 0, 14, and 28 of therapy to enumerate the number of total lymphocytes, T cells, B cells, and lymphocytes expressing activation markers. Baseline total lymphocyte counts and subpopulations were similar in the 4 treatment arms. Responding patients had a smaller decrease in total CD45(+) cell count (P = .005) compared with nonresponding patients at day 28. On univariate analysis, those who developed chronic GVHD had significantly higher CD8(+) cell counts at day 14 compared with those without it (P = .005). There was no significant association between baseline lymphocyte count and survival. On univariate analysis, among the patients with higher lymphocyte counts at days 14 and 28, there was a trend toward better survival at day 180, although this trend did not reach the predetermined threshold for significance. We found no significant differences in lymphocyte total or subpopulation counts among the 4 treatment arms, and no notable influence on outcomes., (Copyright © 2013 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Background: Diphtheria toxin (DT) has shown anticancer activity in both experimental models and humans but its adverse effects stopped further developments. Cross-reacting Material 197 (CRM197) is the product of a single missense mutation (Gly52 to Glu) within fragment A of DT. It has been shown to induce weak toxicity in some cell strains, but it shares immunological properties with native DT. CRM197 commonly acts as an immunological adjuvant, or as an inhibitor of heparin-binding epidermal growth factor. Recently, CRM197 was shown to have promising antitumor activity. To better-define this property, we planned a phase I-II study., Patients and Methods: Twenty-nine patients bearing advanced melanoma (18 cases), and other solid tumors (two ovarian cancer, two sarcoma, two gastrointestinal cancers, one urinary bladder carcinoma, one glioblastoma, one neuroblastoma, one ocular melanoma and one primitive neuroectodermal embriogenic tumor (PNET) were evaluated and 19 of them, sub-divided in cohorts, received the following levels of CRM197: Level 1, 0.3 mg; level 2, 1.0 mg; level 3, 2.5 mg; level 4, 3.5 mg; level 5, 5.0 mg; level 6, 7.5 mg. The drug was given once every two days for 4 times and then, after a 2-week rest period, once every 2 days for 4 times. CRM197 was administered subcutaneously in the abdominal wall., Results: grade 1-2 common toxicities included fever, chills, fatigue, dizziness, nausea, vomiting and headache, neutrophilia and skin painful reactions appeared regularly at levels 3 and 4 (2.5 mg and 3.5 mg). Vomiting and abdominal pain, skin reaction tachycardia and hypotension appeared in two patients at level 5. At 7.5 mg, we observed a severe grade 3 reaction with hypotension, dyspnea and grade 4 myalgia. This was considered the dose-limiting toxicity. Eleven patients (seven with melanoma and four with other tumors) were treated to evaluate anticancer effects at the maximum tolerated dose (5 mg). Only one patient reported a minor response, lasting eight weeks. Ten patients reported progressive disease., Conclusion: CRM197, injected subcutaneously at 5 mg, elicited a generic inflammatory response causing toxicity, and did not exert a significant degree of antitumor activity in patients with advanced melanoma and solid tumour.

Natural regulatory T cells (Tregs) participate in responses to various chronic infections including HIV. HIV infection is associated with a progressive CD4 lymphopenia and defective HIV-specific CD8 responses known to play a key role in the control of viral replication. Persistent immune activation is a hallmark of HIV infection and is involved in disease progression independent of viral load. The consequences of Treg expansion, observed in HIV infection, could be either beneficial, by suppressing generalized T-cell activation, or detrimental, by weakening HIV-specific responses and thus contributing to viral persistence. The resulting balance between Tregs contrasting outcomes might have critical implications in pathogenesis. Topics covered in this review include HIV-induced alterations of Tregs, Treg cell dynamics in blood and tissues, Treg-suppressive function, and the relationship between Tregs and immune activation. This review also provides a focus on the role of CD39(+) Tregs and other regulatory cell subsets. All these issues will be explored in different situations including acute and chronic infection, antiretroviral treatment-mediated viral control, and spontaneous viral control. Results must be interpreted with regard to both the Treg definition used in context and to the setting of the disease in an attempt to draw clearer conclusions from the apparently conflicting results.

In a placebo-controlled study, denileukin diftitox (DD) was effective against cutaneous T-cell lymphoma (CTCL) expressing CD25. An open-label companion study examined the efficacy and safety of DD in 36 patients with skin biopsies containing < 20% CD25 cells by immunohistochemistry staining (CD25 low expression). Patients received DD 18 μg/kg/day for 5 consecutive days every 3 weeks for up to eight courses. The primary endpoint, overall response rate, was 30.6% (95% confidence interval: 16.3, 48.1), 33.3% for stage IIA or lower disease, and 26.7% for stage IIB or greater disease. Median progression-free survival (PFS) was > 487 days, and median time to treatment failure was 68.5 days. No difference in PFS by disease stage was observed. The safety profile of DD in CD25 low-expression disease was similar to that in CD25+ disease. These findings suggest that CD25 low expression does not preclude a meaningful clinical response to DD in patients with CTCL.

Background: Spontaneous remission is recognized in mycosis fungoides (MF) and Sézary syndrome (SS)., Objective: We analyzed the outcome of 44 patients with previously treated CD25-positive (CD25+), recurrent/persistent MF/SS randomly assigned to receive placebo as part of a phase III trial., Methods: This trial investigated the efficacy and safety of two doses of denileukin diftitox in patients with MF/SS who had received up to 3 prior therapies. The primary end point was overall response rate. Multivariate regression analyses were used to assess the relationship between baseline covariates and clinical outcomes., Results: The overall response rate was 15.9% for placebo recipients (complete response: 2.3%; partial response: 13.6%), reflecting the baseline rate of disease remission that can be expected in a clinical trial. The median progression-free survival (PFS) in the placebo arm was moderately short at 4.4 months compared with the active-agent arm but important to consider in the context of recent single-arm phase II studies of other therapies for MF/SS that report PFS of approximately 6 months. Multivariate analyses identified no significant effects of any baseline factors on either overall response rate or PFS, although there was a trend toward poorer PFS with advanced age. Because sepsis occurred significantly more often in the placebo arm versus the active-treatment arm, the role of antibiotics in causing remission cannot be discounted (6.8% vs 0%; P < .05)., Limitations: This study had a relatively small sample size, yielding a wide 95% confidence interval., Conclusion: The results may serve as a useful comparator for other active-treatment studies of MF/SS that lack a placebo-control arm., (Copyright © 2011 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Cutaneous T-cell lymphoma (CTCL) is a rare non-Hodgkin lymphoma with predominant skin manifestations and a relatively indolent course at early stages, but it can be fatal in advanced settings. In the absence of cure, the goal of therapy for CTCL is to induce long-term remissions without further compromising a patient's immune system or quality of life. Denileukin diftitox (DD) is a fusion protein chemotherapeutic agent used for the treatment of persistent or recurrent CTCL. It binds selectively to the high- and intermediate-affinity interleukin-2 receptor (CD25+) on lymphocytes and is internalized by these cells. Inside the cells, the diphtheria toxin portion of fusion protein is cleaved by proteolytic enzymes, causing cell death. DD produces durable responses and may forestall disease progression. This article reviews DD phase III clinical trial data and summarizes one institution's clinical experience in the management of the most frequent and clinically significant adverse effects of DD (e.g., acute infusion reactions, capillary leak syndrome, hypoalbuminemia, visual changes, constitutional symptoms, rash, hepatobiliary disorders). Many DD-associated adverse effects can be managed effectively without dose reduction or interruption of treatment with prudent use of supportive care measures.

Unlabelled: Better treatment and survival outcomes are needed for the rare primary cutaneous peripheral T-cell lymphomas.Five (62.5%) of 8 patients with peripheral T-cell lymphomas enrolled in a pilot study of denileukin diftitoxat 18 μg/kg per day for 5 days followed by once weekly for 24 weeks responded, including 2 complete responses, one of which is ongoing at 8 years., Purpose: To evaluate the safety and efficacy of an alternate dosing regimen in rare primary cutaneous peripheral T-cell lymphoma variants., Methods: This is a prospective, single center, pilot study of denileukin diftitox (Dd) in patients with persistent or recurrent cutaneous peripheral T-cell lymphomas and mycosis fungoides (MF) variants, excluding Sézary syndrome (SS). Dd was administered at 18 μg/kg per day for 5 days and once weekly for 24 weeks, with response by modified skin weighed assessment tool., Results: Eight patients, with a median age of 76 years (range, 44-88 years), were treated between December 2003 and July 2008. Five (62.5%) of 8 patients responded, including 3 patients with CD30(+) anaplastic large-cell lymphoma (ALCL) with 2 complete responses, one ongoing at 8 years. One patient with CD8(+) and 1 patient with natural killer T cell lymphoma (NK-T) had partial responses. Progressive disease occurred in 1 patient positive for human T-cell lymphotropic virus and 1 patient with ALCL. Vascular leak syndrome (VLS) occurred in 6 (75%) of 8 patients during or just after cycle 1. Three were grade 3, and 2 of these resulted in study withdrawal. Other adverse effects included nausea or vomiting (n = 3), fatigue (n = 1), back pain (n = 1), transaminase elevations (n = 3), and elevated creatinine (n = 1)., Conclusions: Dd with an alternate dosing schedule was active in this small study of primary cutaneous T-cell lymphomas., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Although cancer tends to affect the elderly, most preclinical studies are carried out in young subjects. In this study, we developed a melanoma-specific cancer immunotherapy that shows efficacy in aged but not young hosts by mitigating age-specific tumor-associated immune dysfunction. Both young and aged CD4(+)CD25(hi) regulatory T cells (Treg) exhibited equivalent in vitro T-cell suppression and tumor-associated augmentation in numbers. However, denileukin diftitox (DT)-mediated Treg depletion improved tumor-specific immunity and was clinically effective only in young mice. DT-mediated Treg depletion significantly increased myeloid-derived suppressor cell (MDSC) numbers in aged but not young mice, and MDSC depletion improved tumor-specific immunity and reduced tumor growth in aged mice. Combining Treg depletion with anti-Gr-1 antibody was immunologically and clinically more efficacious than anti-Gr-1 antibody alone in aged B16-bearing mice, similar to Treg depletion alone in young mice. In contrast, DT increased MDSCs in young and aged mice following MC-38 tumor challenge, although effects were greater in aged mice. Anti-Gr-1 boosted DT effects in young but not aged mice. Aged antitumor immune effector cells are therefore competent to combat tumor when underlying tumor-associated immune dysfunction is appropriately mitigated, but this dysfunction varies with tumor, thus also varying responses to immunotherapy. By tailoring immunotherapy to account for age-related tumor-associated immune dysfunctions, cancer immunotherapy for aged patients with specific tumors can be remarkably improved.

Denileukin Diftitox (ONTAK(®), DAB(389) IL-2) is a recombinant DNA-derived fusion protein depleting cells that express high-affinity IL-2 receptor. Important cell targets are CD4(+)CD25(+)Foxp3(+) regulatory T cells (T(reg)). Elimination of immunosuppressive T(reg) by Denileukin Diftitox may provide a way to modulate immune tolerance following stem cell transplantation. Here, we combined T(reg) depletion with a vaccination approach to induce donor-specific immune reactions. To investigate this approach we chose the mixed chimerism canine stem cell transplantation model which represents a high state of tolerance between two hematopoietic systems. The aim was therefore to induce a graft versus hematopoiesis effect thereby converting mixed to full donor chimerism. Dog leukocyte antigen identical siblings that had developed a stable mixed chimerism after non-myeloablative stem cell transplantation received a single dose of Denileukin Diftitox (18μg/kg, i.v.) followed by several cell-lysate vaccinations. Host peripheral blood mononuclear cell lysates combined with CpG-ODN, and Montanide(®) ISA 51 were locally applied. In vitro studies demonstrated that canine T(reg) are a target of Denileukin Diftitox. The suppression of T-cell proliferation by T(reg) was abolished by addition of Denileukin Diftitox (10nM). An increase of proliferation of median 300% (range: 200%-425%) was observed. No change in donor chimerism was observed after administration of Denileukin Diftitox and vaccination. This study highlights that application of Denileukin Diftitox resulted in a depletion of T(reg) followed by an increase of immune response in vitro. This effect could not be confirmed in vivo even if the immune system was stimulated by vaccinations., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Sézary syndrome (SS) represents 3% of cutaneous T-cell lymphomas (CTCL). It is an aggressive epidermotropic CTCL with a 5-year survival rate of 24%. According to EORTC (European organization for research and treatment of cancer), SS is defined by erythroderma, diffuse lymphadenopathy, atypical T lymphocytes (>1000/mm(3)), and the presence of a major blood, cutaneous and nodal T cell clone. A specific marker for atypical tumoral T lymphocytes known as Sézary cells was identified in 2001, namely KIR3DL2 (CD158k) receptor, which allows more specific diagnosis of SS; levels of this marker are highly correlated with the clinical course of the disease. In therapeutic terms, clinical trials are being conducted on new molecules that point towards an improved prognosis for this disease. We propose a review of Sézary syndrome, which is currently the subject of scientific papers concerning both physiopathology and therapeutics, with new prospects of targeted therapy., (Copyright © 2011 Elsevier Masson SAS. All rights reserved.)

Background: We previously found that administration of an interleukin 2/diphtheria toxin conjugate (DAB/IL2; Denileukin Diftitox; ONTAK) to stage IV melanoma patients depleted CD4(+)CD25(HI)Foxp3(+) regulatory T cells and expanded melanoma-specific CD8(+) T cells. The goal of this study was to assess the clinical efficacy of DAB/IL2 in an expanded cohort of stage IV melanoma patients., Methods: In a single-center, phase II trial, DAB/IL2 (12 μg/kg; 4 daily doses; 21 day cycles) was administered to 60 unresectable stage IV melanoma patients and response rates were assessed using a combination of 2-[(18)F]-fluoro-2-deoxy-glucose (FDG)-positron emission tomography (PET) and computed tomography (CT) imaging., Results: After DAB/IL2 administration, 16.7% of the 60 patients had partial responses, 5% stable disease and 15% mixed responses. Importantly, 45.5% of the chemo/immuno-naïve sub-population (11/60 patients) experienced partial responses. One year survival was markedly higher in partial responders (80 ± 11.9%) relative to patients with progressive disease (23.7 ± 6.5%; p value < 0.001) and 40 ± 6.2% of the total DAB/IL2-treated population were alive at 1 year., Conclusions: These data support the development of multi-center, randomized trials of DAB/IL2 as a monotherapy and in combination with other immunotherapeutic agents for the treatment of stage IV melanoma., Trial Registration: NCT00299689.

Background: Angioimmunoblastic T-cell lymphoma (AITL) accounts for 18% of peripheral T-cell lymphomas worldwide. Skin involvement occurs in up to 50% of patients but poses a diagnostic dilemma because of the limited number of reported cases and subsequent lack of established diagnostic criteria., Objective: The purpose of this review is to examine common clinical, histologic, and molecular findings in cases of AITL with the hope of improving the diagnostic accuracy of this challenging condition., Methods: We present a case of AITL and conducted a review of the literature., Results: The common clinical and histologic features in cases of AITL are nonspecific. However, newer immunohistochemical stains and gene rearrangement studies appear very promising at improving diagnostic capabilities., Limitations: There was a paucity of reported cases of AITL in the literature, and this review is retrospective., Conclusion: AITL presents with nonspecific clinical and histologic findings, but immunohistochemical stains and gene rearrangements can help establish the diagnosis., (Copyright © 2010 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)