Interleukin-2 fusion protein: an investigational therapy for interleukin-2 receptor expressing malignancies

Novel therapies targeting cutaneous T cell lymphomas and their microenvironment

Cutaneous T-cell lymphomas (CTCL) are rare non-Hodgkin lymphomas with a generally indolent course managed with topical, skin-directed therapies. A small subset, however, will progress to advanced stage disease necessitating systemic therapy for disease control. Currently approved therapies have low response rates and generally short durations of response. Novel therapies, therefore, are urgently needed to address this unmet need. In this review, the mechanisms of CTCL pathogenesis and progression, including the role of the tumor microenvironment and molecular alterations, are summarized. Based on these biologic insights, novel therapies currently under investigation and those with a strong preclinical biologic rationale including T cell and macrophage checkpoint inhibitors, epigenetic regulators, targeted antibodies, tyrosine kinase inhibitors, and apoptosis modulating therapies are discussed.

Bispecific human IL2-CCR4 immunotoxin targets human cutaneous T-cell lymphoma

The majority of clinically diagnosed cutaneous T-cell lymphomas (CTCL) highly express the cell-surface markers CC chemokine receptor 4 (CCR4) and/or CD25. Recently, we have developed diphtheria toxin-based recombinant Ontak®-like human IL2 fusion toxin (IL2 fusion toxin) and anti-human CCR4 immunotoxin (CCR4 IT). In this study, we first compared the efficacy of the CCR4 IT vs IL2 fusion toxin for targeting human CD25⁺ CCR4⁺ CTCL. We demonstrated that CCR4 IT was more effective than IL2 fusion toxin. We further constructed an IL2-CCR4 bispecific IT. The bispecific IT was significantly more effective than either IL2 fusion toxin or CCR4 IT alone. The bispecific IT is a promising novel targeted therapeutic drug candidate for the treatment of refractory and recurrent human CD25⁺ and/or CCR4⁺ CTCL.

Antibody-Directed Therapies: Toward a Durable and Tolerable Treatment Platform for CTCL

Cutaneous T-cell lymphomas (CTCL) are a rare group of heterogeneous disorders characterized by cutaneous involvement of monoclonal T-lymphocytes. Although indolent at early stages, CTCL can confer significant morbidity, and mortality when advanced. There is an unmet need for tolerable and durable treatments with antibodies recently gaining promise. Here we review approved systemic therapies and discuss select antibodies in development.

Progression of Cutaneous B-Cell Pseudolymphoma to Cutaneous B-Cell Lymphoma

Background:

Debates regarding nosology and clonality surround the entity known as cutaneous pseudolymphoma and its questionable transformation to frank cutaneous lymphoma. The relevance of these arguments is important, not only from a diagnostic standpoint, but also for making inferences based upon behavior, prognosis, and treatment.

Objective:

Our goal was to demonstrate further evidence of progression from cutaneous pseudolymphoma to malignant lymphoma while at the same time advocating a comprehensive plan for evaluation, treatment, and followup of these patients.

Methods:

A retrospective review was conducted of four patients initially considered to have cutaneous B-cell pseudolymphoma (CBPL) and who were later treated for primary cutaneous B-cell lymphoma (CBCL). A review of the literature of cases suggesting progression to malignant lymphoma from precursor lesions was also performed.

Results:

Four patients initially diagnosed with CBPL by a combination of histologic, immunophenotypic, and gene rearrangement criteria had a progressive clinical course that, over a range of 17–51 months, evolved into CBCL. All patients had a comprehensive systemic workup to rule out the possibility of extracutaneous disease and were treated with local radiation therapy and close followup. There has been no evidence of extracutaneous disease with an average followup of 14 months.

Conclusion:

The potential for certain cutaneous pseudolymphomas to progress to CBCL is real. The combination of histologic and immunophenotypic criteria, along with the clinical picture, remains the best way to judge the aggressiveness of the lesion. Gene rearrangement studies, whether performed by Southern blot or polymerase chain reaction (PCR), are of limited value and should be used to support the overall clinicopathologic picture. Radiation therapy of these patients should be thought of early in the management plan and is a very successful form of treatment when combined with close followup.

Targeted toxins

Objective. Current modalities used in the treatment of cancer often cause unacceptable damage to normal tissue. Toxins targeted toward tumor cells by antibodies or growth factors have the potential to selectively kill tumor cells while leaving normal tissue intact. The purpose of this review is to provide background information on targeted toxins and current clinical studies for this new class of anti-cancer compounds.

Data sources. A MEDLINE search was conducted using the term “immunotoxins.” Relevant articles were also obtained by the systematic examination of article references.

Data synthesis. The toxins Pseudomonas exotoxin, diphtheria toxin, and ricin toxin are often used as targeted toxins. Deletion or mutation of the binding domains of these toxins decreased binding of the toxins to normal tissues. Antibodies or growth factors can be used as targeting moiety, and the resulting agents are called immunotoxins or fusion proteins, respectively. DNA technology and chemical modifications of the toxin as well as the antibody moiety led to smaller and less immunogenic targeted toxins. Smaller targeted toxins are less toxic and penetrate further into the tumor. The summary of several targeted toxins elicited during clinical trials in this review makes it clear that several targeted toxins are potential agents for the treatment of various cancers, although some problems still need to be overcome. These problems include toxicity, immunogenicity, cross-reactivity of the targeted toxin with life-sustaining tissue, heterogenicity of tumor cells, and limited tumor penetration.

Interleukin-2 priming chemotherapy: a strategy to improve the remission of refractory/relapsed T cell acute lymphoblastic leukemia

Regardless of the salvage therapy used, primary induction failure in acute lymphoblastic leukemia (refractory ALL) and relapse after a complete remission (CR) are associated with dismal outcomes. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) may be the best treatment option for relapsed/refractory ALL. However, the outcome of allo-HSCT is very poor when a patient is not in CR. Quiescent leukemia cells protect them from the commonly used cell cycle-specific chemotherapeutic agents. Interleukin-2 (IL-2), a very well characterized T cell growth factor, is responsible for the progression of T lymphocytes from the G0 to the S phase of the cell cycle. IL-2 receptors are present on malignant T cells. Interaction of IL-2 with the IL-2 receptor triggers T cell proliferation, but T cells must change from a resting to an activated state, which leads to the de novo synthesis of IL-2 and expression of the IL-2 receptor. Thus, exogenous IL-2 administration is pivotal for the activation of T cells. Based on the findings above mentioned, we hypothesized that IL-2 priming chemotherapy improves the remission of refractory/relapsed T cell acute lymphoblastic leukemia.

Efficacy and safety of denileukin diftitox retreatment in patients with relapsed cutaneous T-cell lymphoma

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.

Denileukin diftitox for the treatment of CD25 low-expression mycosis fungoides and Sézary syndrome

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.

Cutaneous T-cell lymphomas: a review of new discoveries and treatments

Treatment regimens of patients with CTCL vary widely based on clinician preference and patient tolerance. Skin directed therapies are recommended for patients with early stage IA and IB MF, with combinations used in refractory cases. While no regimen has been proven to prolong survival in advanced stages, immunomodulatory regimens should be used initially to reduce the need for cytotoxic therapies. In more advanced stages of disease, treatment efforts should strive for palliation and improvement of quality of life. With many new therapies and strategies on the horizon, the future looks promising for CTCL patients. Unfortunately, other than allogeneic HCT, there are no potential curative therapies for CTCL. Clinical trials are currently underway to identify new therapies to improve quality of life for patients, and researchers are hard at work to identify novel pathways and genes for prognostication and as targets for therapies. Importantly, collaborative clinical trials to enhance rates of accrual need to be conducted, and improved interpretation of data via standardizing end points and response criteria should be an emphasis. Recently, the International Society for Cutaneous Lymphomas (ISCL), the United States Cutaneous Lymphoma Consortium (USCLC), and the Cutaneous Lymphoma Task Force of the European Organisation for Research and Treatment of Cancer (EORTC) met to develop consensus guidelines to facilitate collaboration on clinical trials. These proposed guidelines consist of: recommendations for standardizing general protocol design; a scoring system for assessing tumor burden in skin, lymph nodes, blood, and viscera; definition of response in skin, nodes, blood, and viscera; a composite global response score; and a definition of end points. Although these guidelines were generated by consensus panels, they have not been prospectively or retrospectively validated through analysis of large patient cohorts.

Pilot study of denileukin diftitox alternate dosing regimen in patients with cutaneous peripheral T-cell lymphomas

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.

Phase III Placebo-Controlled Trial of Denileukin Diftitox for Patients With Cutaneous T-Cell Lymphoma

Purpose

This phase III, placebo-controlled, randomized trial was designed to investigate efficacy and safety of two doses of denileukin diftitox (DD; DAB389–interleukin-2 [IL-2]), a recombinant fusion protein targeting IL-2 receptor–expressing malignant T lymphocytes, in patients with stage IA to III, CD25 assay–positive cutaneous T-cell lymphoma (CTCL), including the mycosis fungoides and Sézary syndrome forms of the disease, who had received up to three prior therapies. The primary end point was overall response rate (ORR).

Patients and Methods

Patients (N = 144) with biopsy-confirmed, CD25 assay–positive CTCL were randomly assigned to DD 9 μg/kg/d (n = 45), DD 18 μg/kg/d (n = 55), or placebo infusions (n = 44), administered for 5 consecutive days every 3 weeks for up to eight cycles. Patients were monitored for drug efficacy, clinical benefit, and safety of DD.

Results

ORR was 44% for all participants treated with DD (n = 100; 10% complete response [CR] and 34% partial response [PR]) compared with 15.9% for placebo-treated patients (2% CR and 13.6% PR). ORR was higher in the 18 μg/kg/d group versus the 9 μg/kg/d group (49.1% v 37.8%, respectively), and both doses were significantly superior to placebo. Progression-free survival (PFS) was significantly longer (median, > 2 years) for both DD doses compared with placebo (median, 124 days; P < .001). Rates of moderately severe and severe adverse events (AEs) were slightly higher in the DD groups, whereas moderate and mild AEs were similar to placebo. No statistical differences were observed for drug-related serious AEs.

Conclusion

DD had a significant and durable effect on ORR and PFS with an acceptable safety profile in patients with early- and late-stage CTCL.

The role of protein synthesis in cell cycling and cancer

Cell cycling and protein synthesis are both key physiological tasks for cancer cells. Here we present a model for how the elongation phase of protein synthesis, governed by elongation factor 2 and elongation factor 2 kinase, both modulates and responds to cell cycling. Within this framework we also discuss survivin, a protein with both pro-mitotic and anti-apoptotic roles whose persistence in the cell is tied to protein synthesis due to its short half-life. Finally, we provide a brief overview of efforts of cancer researchers to target EF2 and EF2 kinase.

Denileukin diftitox for the treatment of cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma/mycosis fungoides (CTCL/MF) is a rare lymphoproliferative disorder which can present as an indolent or as an aggressive process involving skin, lymph nodes, and blood. In stages IA, IB and IIA, it is usually managed with topical medications and phototherapy. If there is progression despite application of these treatments, or if the patient presents with a higher stage of disease, systemic chemotherapy or retinoids, rexinoids, biologic response modifiers are often necessary. Consequently, patients are often treated with a sequence of modalities and drugs. Denileukin diftitox (DD, Ontak(R)) is a targeted immunotoxin which has biological activity against malignancies expressing the IL-2 receptor. In addition to its unique mechanism of action, DD has a toxicity profile which does not overlap with most commonly used chemotherapeutic agents. CTCL/MF has been found be particularly susceptible to treatment with this agent. This review will describe the development DD, its proposed mechanism of action, the clinical trials which identified its utility in the treatment of CTCL/MF, the common toxicities encountered with this agent, and the management of these toxicities. In addition the incorporation of DD in the sequential treatment of CTCL/MF and data suggesting potential combination therapies employing this novel agent will be discussed.

Optimizing denileukin diftitox (Ontak®) therapy

Denileukin diftitox (Ontak®) is a novel recombinant fusion protein consisting of peptide sequences for the enzymatically active and membrane translocation domain of diphtheria toxin linked to human IL-2. Denileukin diftitox specifically binds to IL-2 receptors on the cell membrane, is internalized via receptor-mediated endocytosis and inhibits protein synthesis by ADP ribosylation of elongation factor 2, resulting in cell death. This article focuses on the clinical trial that led to the US FDA approval of the drug for cutaneous T-cell lymphoma in 1999, and other investigational studies for hematologic malignancies, recurrent and refractory chronic lymphocytic leukemia, non-Hodgkin B-cell lymphoma, graft-versus-host disease and autoimmune disease, demonstrating the activity and adverse effects of the drug.

Novel Immunosuppressant Agents Targeting Activated Lymphocytes by Biocompatible MPC Polymer Conjugated with Interleukin-2

The immunopharmacological profile of novel biocompatible water-soluble interleukin-2 (IL-2)-conjugated 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer immunosuppressive agents was established. MPC-co-n- butyl methacrylate (BMA)-co-p-nitrophenylcarbonyloxyethyl methacrylate (NPMA) (PMBN) was prepared as a backbone for these novel agents. PMBN contained MPC as a biocompatible unit, BMA as a hydrophobic domain in water, and NPMA as an immobilizable unit with IL-2. This research showed that proliferation of cell lines with high-affinity IL-2 receptors derived from T cell malignancies were suppressed by the PMBN conjugated with IL-2 (PMBN-IL2 conjugate) incorporating paclitaxel (PTX) and cyclosporin A at lower concentrations than used conventionally. PMBN-IL2 conjugates incorporating PTX also inhibited the proliferation of responder cells in a human mixed lymphocyte culture at a lower concentration than unconjugated drug. However, PMBN-IL2 conjugates incorporating FK506 inhibited proliferation no more than FK506 alone. The PMBN-IL2 conjugate with PTX may therefore be useful for selectively eliminating activated lymphocytes that hyperproduce high-affinity IL-2 receptors. As an entirely human 'immunotoxin analogue' it may not be associated with the dose-limiting toxicity and immunogenicity of conventional immunotoxins.

Phase II trial of denileukin diftitox for relapsed/refractory T-cell non-Hodgkin lymphoma

This phase II study evaluated the safety and efficacy of denileukin diftitox, an interleukin-2-diphtheria toxin fusion protein, in relapsed/refractory T-cell non-Hodgkin lymphoma (T-NHL), excluding cutaneous T-cell lymphoma. Eligible patients received denileukin diftitox 18 microg/kg/d x 5 d every 3 weeks for up to eight cycles. Tumour staging was performed every two cycles and the primary endpoint was the objective response rate [complete response (CR) + partial response (PR)]. For 27 patients enrolled, median age: 55 years (range 26-80 years), 70.4% male, and mean prior therapies: 2.5 (range 1-6). Objective responses (six CRs, seven PRs) were achieved in 13 patients (48.1%), stable disease in eight (29.6%) and six (22.2%) had progressive disease. An objective response was achieved in eight of 13 patients (61.5%) with CD25(+) tumours (four CR/four PR) and five of 11 patients (45.5%) with CD25(-) tumours (two CR/three PR). Median progression-free survival was 6 months (range, 1-38+ months). Most adverse reactions were grade 1/2 and transient. No grade 4-5 toxicities were reported. Denileukin diftitox had significant activity and was well tolerated in relapsed/refractory T-NHL, with responses observed in both CD25(+) and CD25(-) tumours. Further studies of denileukin diftitox in combination with other agents are warranted in previously untreated and relapsed/refractory T-NHL.

What's new in the management of cutaneous T-cell lymphoma?

The aetiology and clinical management of primary cutaneous T-cell lymphoma (CTCL) and specifically of mycosis fungoides and Sezary syndrome are poorly defined. Interesting new insights into CTCL disease biology as well as a number of emerging of novel therapeutic interventions make this an increasingly interesting area for dermatologists and oncologists involved in the treatment of CTCL. This review article covers much of this new information including new drugs, such as denileukin diftitox (Ontak) a targeted cytotoxic biological agent, Bexarotene an RXR selective retinoid, anti-CD4 monoclonal antibodies (mAb), new cytotoxics agents and vaccines.

Pilot study of etanercept in patients with relapsed cutaneous T-cell lymphomas

BACKGROUND

Tumor necrosis factor (TNF)-alpha has been implicated in the pathogenesis of cutaneous T-cell lymphoma (CTCL).

OBJECTIVE

To assess the toxicity, safety, and efficacy of etanercept (soluble TNF receptor) in patients with relapsed CTCL.

METHODS

Etanercept was administered twice weekly at a dose of 25 mg subcutaneously. Patients with improvement after two months could be continued on treatment.

RESULTS

Twelve out of the 13 patients enrolled on study were evaluable (Stage I-IIA, 3 patients; Stage IIB-IV disease, 9 patients). The median number of previous therapies was 7 (range, 3-12). Etanercept induced partial remission in one patient (8%) and minor response in one patient (8%), both of whom had Stage IB disease. Most patients experienced no side effects.

CONCLUSION

This pilot study suggests that etanercept is safe and generally well tolerated in patients with CTCL. The effect of etanercept in a larger cohort of patients with early disease merits investigation.

Binding and cytotoxicity of conjugated and recombinant fusion proteins targeted to the gonadotropin-releasing hormone receptor

Pokeweed antiviral protein (PAP) is a plant-derived, highly potent ribosome inactivating protein that causes inhibition of protein translation and rapid cell death. We and others have delivered this protein to various cell types, including cancer cells, using hormones to specifically target cells bearing the hormone receptor. Here, we compare binding and cytotoxicity of GnRH-PAP hormonotoxins prepared either by protein conjugation (GnRH-PAP conjugate) or through recombinant DNA technology (GnRH-PAP fusion). Although GnRH-PAP conjugate protein bound specifically to and caused cell death in cells bearing the gonadotropin-releasing hormone (GnRH) receptor, we could not detect binding or cytotoxicity using two different versions of the fusion protein in receptor-positive cells. We conclude that generation of an active GnRH-PAP fusion protein may not be feasible either because both ends of the GnRH molecule are required for receptor binding, but only the NH(2) terminus is free in the fusion protein and/or that more potent analogues of GnRH (inclusion of which is not feasible in the fusion protein) are needed for efficient targeting. In contrast, the GnRH-PAP conjugate shows promise as a novel anticancer agent, capable of targeting cancer cells expressing the GnRH receptor such as prostate, breast, ovarian, endometrial, and pancreatic cells. It may also be useful as a therapeutic agent to eliminate pituitary gonadotrophs, eliminating the need for chronic GnRH analogue administration to treat hormone-sensitive diseases.

The use of cytokines, fusion proteins and antibodies to treat cutaneous T-cell lymphoma

It has long been known that certain immune augmenting therapeutics, particularly interferon alpha, can exert profound salutary effects on the clinical progress of patients with cutaneous T-cell lymphoma. Emerging evidence that the host immune response may play an important role in the control of this disorder has led to the clinical application of other cytokines including interleukin-12 and interferon gamma. In this review, the authors will summarize current knowledge regarding the use of cytokines, fusion proteins and antibodies for the treatment of cutaneous T-cell lymphoma.

Interleukin-2 receptor–directed therapies for cutaneous lymphomas

Our emerging understanding of the IL-2/IL-2R system opens the possibility for more specific immunotherapy of CTCL. This understanding, taken in conjunction with the ability to produce humanized antibodies to the IL-2R subunit by genetic engineering; to arm these antibodies, as well as IL-2 itself with toxins or with alpha- and beta-emitting radionuclides; and to modulate IL-2R subunits to optimize targeting of these agents provides a rational therapeutic strategy for the treatment of IL-2R-expressing CTCL. Although most of these studies were conducted in HTLV-1-associated T-cell lymphomas or CTCL, it is likely that these agents may be applicable to other T-cell lymphomas, including the anaplastic large cell lymphomas, peripheral T-cell lymphomas, and the natural killer lymphomas, because these cells express the IL-2 receptor.

Fusion of interleukin-2 to subunit antigens increase their antigenicity in vitro due to an interleukin-2 receptor beta-mediated antigen uptake mechanism

Subunit vaccines, based on one or more epitopes, offer advantages over whole vaccines in terms of safety but are less antigenic. We investigated whether fusion of the cytokine interleukin-2 (IL-2) to influenza-derived subunit antigens could increase their antigenicity. The fusion of IL-2 to the subunit antigens increased their antigenicity in vitro. Encapsulation of the subunit antigen in liposomes also increased its antigenicity in vitro, yet encapsulation of the subunit IL-2 fusion did not. The use of anti-IL-2 receptor beta (IL-2Rbeta) antibody to block the receptor subunit on macrophages suggested that the adjuvancy exerted by IL-2 in our in vitro system is due to, at least in part, a previously unreported IL-2Rbeta-mediated antigen uptake mechanism.

Lymphoma of the skin

This chapter describes the various ways in which the non-Hodgkin's lymphomas can involve the skin, how these diseases should be assessed, standard treatments available in 2002, and new directions in research. The goal of the session is to succinctly review recent developments in lymphoma classification and treatment as they apply to the unique aspects of lymphoma when manifest in the skin. In Section I, Dr. Eric Hsi reviews the special characteristics of the lymphomas seen when they proliferate in the skin and the application of the new World Health Organization classification system to the cutaneous lymphomas, emphasizing the unique challenges of recognizing and correctly classifying these diseases. He summarizes the evidence in favor of including the skin lymphomas in the overall lymphoma classification scheme and concludes with a practical description of the specific skin lymphoma entities. In Section II, Dr. Joseph Connors describes the current optimal treatment of the B-cell lymphomas when they present in or metastasize to the skin. Building on the classification scheme described by Dr. Hsi, Dr. Connors outlines a treatment approach based on current understanding of pathophysiology of these diseases and application of each of the effective modalities available for cutaneous lymphoma including radiation, chemotherapy, and immunotherapy. In Section III, Dr. Francine Foss concludes the session with a discussion of the different T-cell lymphomas that start in or spread to the skin concentrating on mycosis fungoides, cutaneous anaplastic large cell lymphoma and peripheral T-cell lymphoma. She includes comments on the newer anti-T-cell chemo- and immuno-therapeutics focusing on agents and techniques specific for cutaneous T-cell lymphomas.

Production of genetically engineered biotinylated interleukin-2 and its application in a rapid nonradioactive assay for T-cell activation

The development of reliable assay systems that can measure lymphocyte activation in vitro has been a major goal of immunodiagnostics. Traditionally, tritiated thymidine incorporation has been used to monitor T-cell activation. Other methods include enzyme-linked immunosorbent assay (ELISA), enzyme-linked immunospot assay, and colorimetric assays. We have established a lymphocyte activation assay that utilizes fluorescein isothiocyanate (FITC)-streptavidin bound to recombinant biotinylated human interleukin-2 (IL-2). Utilizing recombinant DNA technology, a unique monobiotinylated human IL-2 has been created and isolated using the Promega PinPoint vector system. ELISA has been used to demonstrate streptavidin binding and recognition by a human IL-2-specific antibody. IL-2 function has been demonstrated using a murine IL-2-dependent T-cell line, CTLL-2, responsive to human IL-2. Recombinant biotinylated human IL-2 conjugated to streptavidin-FITC or streptavidin-horseradish peroxidase has been used to monitor T-cell activation in the presence of antigen as well as mitogen. The sensitivity and convenience of this method make this lymphocyte activation assay an attractive alternative to tritiated thymidine incorporation as a method for monitoring T-cell activation. In addition, the availability of a recombinant biotinylated human IL-2 will permit the production of a uniform product suitable for diagnostic and clinical application.

The human T-cell lymphoma/leukemia viruses

The primate T-cell lymphoma/leukemia viruses belong to an oncogenic genus of complex retroviruses. Members of this genus have been shown to be pathogenic in man. The human T-cell lymphoma/leukemia virus (HTLV) type I has been linked in the etiology of T-cell malignancies and "autoimmune-like" neurologic and rheumatic disorders; a related virus, HTLV-II, is becoming increasingly associated with similar disorders. Cell transformation is thought to be caused predominantly by the effects of the viral regulatory protein, Tax. An additional induced host cell molecule, adult T-cell lymphoma-derived factor, may contribute to cell immortalization. Like the DNA tumor viruses, HTLV activates transcription of cellular proto-oncogenes and inhibits cellular mechanisms of tumor suppression, cell cycle arrest, and apoptosis. However, individuals who are able to mount a strong cell-mediated immune response and limit viral entry into uninfected cells do not develop associated malignancies. Unfortunately, HTLV-induced malignancies are difficult to treat with conventional chemotherapy, and disease progression is often rapid with a median survival of less than 2 years. There are, however, some novel approaches that have yet to be fully tested that may have greater efficacy in the treatment of HTLV-induced diseases. In the future, better screening and detection methods, along with new vaccines and therapies, may contribute to the increased prevention and control of HTLV infection and its associated diseases.

New biologic agents for the treatment of cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is typically a skin-infiltrating malignancy of clonally derived CD4+ T lymphocytes. Because the host antitumor response appears to play an important role in disease control, systemic therapeutic agents are used in such a manner as to preserve the integrity of the host antitumor response while selectively targeting the malignant cells. The new biologic response-modifying treatment options currently used to treat CTCL are reviewed.

Arginine butyrate increases the cytotoxicity of DAB(389)IL-2 in leukemia and lymphoma cells by upregulation of IL-2Rbeta gene

DAB(389)IL-2 (ONTAK) is a fusion protein consisting of the ADP-ribosyltransferase and membrane translocating domains of native diphtheria toxin and the full-length sequence for interleukin-2 (IL-2) gene. In vitro data demonstrates that DAB(389)IL-2 is cytotoxic to cells expressing the high affinity IL-2 receptor (IL-2R). In Phases I and II clinical trials of patients whose tumor cells express a component of the IL-2R, the response rates were 18% for B-cell non-Hodgkin lymphoma (NHL) and 30% for cutaneous T-cell lymphoma (CTCL). In this study, we examined the effects of arginine butyrate on IL-2R expression and susceptibility of leukemia cells to intoxication by DAB(389)IL-2. We demonstrate that the p75 subunit of the IL-2R (IL-2Rbeta) is upregulated in the presence of low concentrations of arginine butyrate (0.06mM) which had no direct growth inhibitory effect on the cells. To explore mechanisms of this upregulation, we examined the effect of 0.06mM arginine butyrate on relevant transcriptional elements and on histone deacetylase and found activation of cAMP response element (CRE) but not NFAT or NFKB, as well as inhibition of histone deacetylase (HDAC). Our results suggest that the effects of physiologically achievable concentrations of butyrate on IL-2R expression could be exploited to enhance the susceptibility of intermediate and low-affinity IL-2R expressing leukemia cells to DAB(389)IL-2.

Cutaneous T-cell lymphoma. New immunomodulators

During the most recent decades, much knowledge has been gained concerning the immunologic and pathologic mechanisms of CTCL. The development of immunomodulators aimed at correcting aberrations in immunology and cellular growth and differentiation reflects this increased understanding. This review of the currently available immune-response modifying drugs shows that recombinant forms of natural cytokines and retinoids can be developed with tolerable toxicity profiles and substantial efficacy. Although milestone drugs such as bexarotene have been approved by the FDA- for treatment of CTCL, other agents such as IL-12 may also have a place in treatment of the disease. Even though unapproved, IFN-alpha may be the most active single immunomodulating agent against CTCL. It seems that further delineation of CTCL cytokine profile changes and immunologic aberrations are key in developing effective immunomodulators that are able to reverse these alterations.

Rituximab: perspective on single agent experience, and future directions in combination trials

The chimeric anti-CD20 antibody rituximab is the first monoclonal antibody to gain regulatory approval for the treatment of any malignancy. As such, its development represents a major milestone in cancer therapy. It is an effective single agent for patients with CD20-positive B-cell malignancies, using a well-tolerated and brief (weekly x 4) schedule that has become the accepted standard. Since this weekly x 4 schedule is not a maximum tolerated dose, additional research is being done on different doses and schedules of rituximab. Researchers are also exploring the use of rituximab in conjunction with cytokines or chemotherapy. Further developments in the use of rituximab and other targeted therapy approaches can be expected as we learn more about the mechanisms of action of, and resistance to, rituximab.

Therapeutic advances in biological response modifiers in the treatment of cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is most often a skin-infiltrating malignancy of clonal CD4+ T-cells. Therapy is based on staging and the likelihood of progression. Biological response modifiers and chemotherapeutic agents are used to preserve the integrity of the host antitumour response while selectively targeting the malignant cells. The biological response-modifying treatment options currently used to treat CTCL are bexarotene, denileukin diftitox, interferon-alpha, interferon-gamma and interleukin-12, as well as extracorporeal photopheresis and phototherapy. A combination therapy approach maximises response in patients with advanced CTCL. Biological response modifiers in combination with photopheresis are used for patients with the leukaemic phase of the disease. Among the majority of patients with advanced stage disease so treated, immune response augmentation appears to prolong survival. Future areas of research should assess not only survival and optimal treatment combinations, but also quality of life during the treatment period.

Primary cutaneous T-cell lymphoma: review and current concepts

PURPOSE

Primary cutaneous T-cell lymphomas (CTCLs) encompass a wide variety of lymphomas that are characterized by the localization of the malignant lymphocytes to the skin at presentation. Advances in molecular biologic techniques, including immunophenotyping and gene rearrangement studies to determine clonality, have led to more frequent diagnosis of CTCL as well as more consistent subclassification of these entities. However, there continues to be confusion in the classification, prognosis, and management of patients with CTCL. The purpose of this review is to present a summary of the diagnosis, prognosis, and treatment of CTCL, with specific emphasis on mycosis fungoides (MF) and Sézary syndrome (SS). We also present a detailed discussion of the entities that make up the differential diagnosis of CTCL.

DESIGN

We reviewed the medical literature on CTCL and other diseases that make up the differential diagnosis of CTCL.

RESULTS AND CONCLUSION

MF and SS are the most common forms of CTCL. The etiology of this disease is still unknown. Patients may go for months to years with skin abnormalities before being diagnosed. MF/SS is an indolent disease and patients with T1 disease have a normal life expectancy. Patients who undergo transformation to large-cell lymphoma (8% to 23% of patients) have a poor prognosis, with mean survival ranging from 2 to 19 months. Treatment for MF/SS continues to be palliative. There are many new therapies that are currently being investigated in clinical trials, and the DAB(389)IL-2 fusion protein was recently approved for the treatment of refractory MF/SS.

Targeting activated lymphocytes with an entirely human immunotoxin analogue: human pancreatic RNase1-human IL-2 fusion

A hybrid human protein was produced in E. coli by fusing the genes encoding human pancreatic RNase1 (hpRNase1) and human IL-2 (hIL-2). The recombinant hpRNase1-hIL-2 inhibited protein synthesis in HTLV-1-infected, malignant T cells, which hyperproduce high affinity IL-2 receptors, with an IC(50)of 2x10(-8) M, whereas no inhibition was detectable in control cells with lower affinity receptors. HpRNase1 alone had an IC(50)of almost 10(-3) M. A molar excess of hIL-2 blocked the protein synthesis inhibition dose-dependently. In a human mixed lymphocyte culture, hpRNase1-hIL-2 inhibited the proliferation of responder cells with potency comparable to that of cyclosporine, while non-effective doses of FK506 importantly improved its potency. Despite its short half-life in animals, hpRNase1-hIL-2 rapidly enters cells in a few minutes and arrests the protein translation in less than 10 h. Thus, hpRNase1-hIL-2 may be useful to selectively eliminate activated lymphocytes hyperproducing high affinity IL-2 receptors, as in allograft rejection, graft-versus-host disease, autoimmune disorders, adult T cell leukaemia and other lymphoproliferative or retroviral malignancies including HIV infection, without inducing general immunosuppression. As an entirely human "immunotoxin analogue" it may alleviate the dose limiting toxicity and immunogenicity of conventional immunotoxins.

Cutaneous T-cell lymphoma/leukemia

Effective treatment for cutaneous T-cell lymphomas (CTCL) requires an accurate and specific diagnosis based on the clinical presentation combined with evaluation of the histopathology, immunophenotyping, and gene rearrangement studies. Careful clinical and pathologic evaluation in centers familiar with the diverse forms of CTCL is most valuable for determining treatment options. The goals of treatment in mycosis fungoides (MF), which afflicts more than 50% of patients with CTCL, are the relief of symptoms and improvement in cosmetics. Despite some uncontrolled clinical trial results that have been reported to suggest "cures" in this disease, the general perception remains that this disease is not curable with standard therapies available today. Treatment is divided into topical (skin-directed) and systemic therapy. The most active systemic agent for the treatment of MF remains interferon-alpha, although many new modalities have recently been approved for the treatment of CTCL.

Emerging new therapies for cutaneous T-cell lymphoma

Improved therapy for CTCL will depend on a better understanding of the pathogenesis of this disease at a molecular level. It is clear that the T cells in MF and CTCL do not undergo normal programmed cell death and have prolonged lifespans. Skin flora or other antigens may stimulate the initial proliferation, offering another approach to change the course of the disease. There has been tremendous interest in biological response modifiers, and the first targeted fusion toxin to activated T cells has been approved for CTCL. New retinoids with increased selectivity and decreased side effects are being tested for this disease. In summary, the treatment of CTCL should continue to improve and should be focused on strategies that preserve the immune function in these patients.

Surface membrane biotinylation efficiently mediates the endocytosis of avidin bioconjugates into nucleated cells

Here we demonstrate that biotin covalently attached to cell surface obligates existing receptors to endocytose avidin bioconjugates into nucleated cells. Incubation of fluorescein-labeled avidin with biotinylated cell lines resulted in uniform and rapid surface attachment and endocytosis compared with no detectable association of the avidin-conjugated dye with unbiotinylated cells. Uptake was detected within minutes with efficiencies approaching 100% in cell lines and freshly obtained peripheral blood mononuclear cells. After 24 h, avidin was barely detectable on the surface of the nucleated cells. In marked contrast, fluorescent avidin remained exclusively on the external membrane of erythrocytes after 24 h. To investigate biotin-mediated endocytosis for the delivery of DNA, we prepared polyethylenimine-avidin (PEI-avidin) conjugates. Surface biotinylation significantly increased the transfection efficiencies of PEI-avidin condensed plasmid DNA coding green fluorescent protein (GFP) to the level of transferrin-receptor targeted gene delivery (15-20% GFP positive cells in culture after 48 h). The increase in transfection efficiency was blocked by the addition of free avidin or biotin to the culture medium. Biotin covalently bound to cell surface membrane proteins efficiently mediates the entry of avidin bioconjugates into nucleated cells.

An IL-2-toxin, DAB389IL-2, inhibits delayed-type hypersensitivity but enhances IgE antibody production

BACKGROUND

Expression of high-affinity IL-2 receptor (IL-2R) on T lymphocytes, key cells in chronic inflammation, is a T-cell activation marker.

OBJECTIVE

We sought to evaluate the effect of the fusion protein DAB389IL-2, which kills cells bearing IL-2R, on delayed-type hypersensitivity and antibody production in Brown Norway rats sensitized with trimellitic anhydride (TMA).

METHODS

DAB389IL-2 (25 micrograms/kg/day) or placebo was administered intraperitoneally for 8 days over the period of sensitization, starting 2 days before sensitization.

RESULTS

The administration of DAB389IL-2 resulted in a one-third reduction in the number of IL-2R-bearing cells and significant weight loss of animals. Delayed-type hypersensitivity, evaluated at 5 weeks after sensitization, was significantly inhibited by treatment with DAB389IL-2. In contrast, production of IgE anti-TMA antibodies after sensitization was increased by treatment with DAB389IL-2. DAB389IL-2 affected neither IgG anti-TMA antibody nor total IgE levels.

CONCLUSION

These data imply that systemic administration of DAB389IL-2 in Brown Norway rats influences cells that have regulatory effects on the immune system, resulting in a switch from a TH1 to a TH2 type of immune response.

Monoclonal antibody therapy for B cell non-Hodgkin's lymphomas: emerging concepts of a tumour-targeted strategy

Although much progress has been made in the understanding of the pathobiology of malignant lymphomas in recent years, progress in the treatment of patients with this diagnosis has been limited. Monoclonal antibody therapy is an innovative and promising concept in the treatment of malignant lymphoma, and the current status of this treatment is reviewed here. Phase I/II clinical trials have proven the high antilymphoma activity of antibody-based therapeutic strategies. Radioimmunoconjugates with myeloablative activity have induced response rates of between 80 and 100% in heavily pretreated patients. The chimeric monoclonal antibody IDEC-C2B8 has shown high antilymphoma activity in patients with relapsed follicular lymphoma with an overall response rate of up to 50%. The combination of the IDEC-C2B8 antibody with standard chemotherapy has shown encouraging results with no increase in toxicity compared with chemotherapy alone. The introduction of antibody therapy promises to open new perspectives in the treatment of patients with malignant lymphoma. Prospective randomised clinical trials will define the patient who will gain maximal benefit from antibody-based therapy.

DAB389IL2 diphtheria fusion toxin produces clinical responses in tumor stage cutaneous T cell lymphoma

Four patients with late stage cutaneous T cell lymphoma (IB-IVA) who had failed at least two previous therapies were treated with DAB389IL2 at 9 or 18 microg/kg as 15-min intravenous infusions daily for 5 days every 3 weeks for eight cycles. Mild vascular leak syndrome (VLS) with transient edema, hypoalbuminemia, weight gain, and myalgias was observed in two of the patients lasting 7-10 days and only occurring on the first cycle. One stage IB patient had a pathologic complete remission (CR) lasting 11+ months from treatment initiation, one stage IIB patient had a complete clinical remission (CCR) lasting >6 months with complete clearing of a large tumor lasting >18 months, and one stage IIB and the one stage IVA patient had partial remissions (80-99% reduction in tumor masses) lasting 5 months. While IL2 receptor (IL2R) was expressed on 20-50% of tumor cells prior to therapy, recurrent tumor was IL2R negative in three of the patients. DAB389IL2 at tolerable doses decreased tumor burden in each of these four standard treatment refractory CTCL patients and may offer an important alternative to standard palliative chemotherapy regimens.