Treatment of T-cell prolymphocytic leukemia with human CD52 antibody

Morphology, immunophenotype, and suggested diagnostic criteria of TCL1 family-negative T-prolymphocytic leukemia

OBJECTIVES

We sought to investigate the morphologic and immunophenotypic characteristics of TCL1 family-negative T-cell prolymphocytic leukemia (T-PLL).

METHODS

Twenty cases of TCL1 family-negative T-PLL were studied.

RESULTS

The doubling time of leukemic cells ranged from less than 2 days to more than 5 years, with a median of 5.5 months. Leukemic cells were small to medium-sized, with round to irregular nuclei, variably condensed chromatin, and small amounts of agranular cytoplasm. A visible nucleolus was identified in 11 (55%) cases. Cytoplasmic blebs/protrusions were identified in all cases, but their occurrence was highly variable from case to case. Bone marrow biopsy showed an interstitial pattern in 90% of cases and a diffuse pattern in the remaining 10% of cases. Flow cytometric immunophenotypic analysis showed that the leukemic cells in all cases were CD4 positive; 3 (15%) also showed concurrent CD8 expression. All cases were positive for CD2 and CD5. Surface CD3 and CD7 were positive in 19 of 20 (95%) cases, and all CD3-positive cases expressed the T-cell receptor αβ. Compared with prototypic T-PLL cases, these 2 groups shared many immunophenotypic findings, except CD8 and CD26, both of which were more commonly expressed in prototypic T-PLL cases.

CONCLUSIONS

TCL1 family-negative T-PLL cases have morphologic and immunophenotypic features that are similar to prototypic T-PLL. They are characterized by neoplastic proliferation of small to medium-sized mature T cells with CD4-positive T-cell receptor αβ phenotype. Tumor cells frequently maintain pan-T antigen expression. Recognizing these morphologic and immunophenotypic features will aid in accurately diagnosing this rare subset of T-PLL.

T-Cell Prolymphocytic Leukemia: Diagnosis, Pathogenesis, and Treatment

T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive neoplasm of mature T-cells. Most patients with T-PLL present with lymphocytosis, anemia, thrombocytopenia, and hepatosplenomegaly. Correct identification of T-PLL is essential because treatment for this disease is distinct from that of other T-cell neoplasms. In 2019, the T-PLL International Study Group (TPLL-ISG) established criteria for the diagnosis, staging, and assessment of response to treatment of T-PLL with the goal of harmonizing research efforts and supporting clinical decision-making. T-PLL pathogenesis is commonly driven by T-cell leukemia 1 (TCL1) overexpression and ATM loss, genetic alterations that are incorporated into the TPLL-ISG diagnostic criteria. The cooperativity between TCL1 family members and ATM is seemingly unique to T-PLL across the spectrum of T-cell neoplasms. The role of the T-cell receptor, its downstream kinases, and JAK/STAT signaling are also emerging themes in disease pathogenesis and have obvious therapeutic implications. Despite improved understanding of disease pathogenesis, alemtuzumab remains the frontline therapy in the treatment of naïve patients with indications for treatment given its high response rate. Unfortunately, the responses achieved are rarely durable, and the majority of patients are not candidates for consolidation with hematopoietic stem cell transplantation. Improved understanding of T-PLL pathogenesis has unveiled novel therapeutic vulnerabilities that may change the natural history of this lymphoproliferative neoplasm and will be the focus of this concise review.

Advances in Cellular Therapy for T-Cell Prolymphocytic Leukemia

T-cell prolymphocytic leukemia (T-PLL) is a rare, aggressive hematologic malignancy with a poor prognosis. Alemtuzumab (Campath) remains the cornerstone for treatment, with an 80% complete response (CR). Hematopoietic stem cell transplant (HSCT) is considered the standard of care as consolidative therapy in eligible patients. However, allogeneic stem cell transplant is also complicated by increased rates of infections from chemotherapy, acute graft-versus-host disease (GVHD), and chronic GVHD. This review aims to report the available literature on the efficacy and complications of consolidative HSCT. It also discusses the importance of patient selection and pre- and post-transplant complications including atypical infections and GVHD.

The immune-related gene CD52 is a favorable biomarker for breast cancer prognosis

Background

An increasing number of studies have demonstrated a role for the tumor microenvironment in tumorigenesis, disease progression, and therapeutic response. This present study aimed to screen the significant immune-related genes and their possible role in the prognosis of breast cancer (BRCA).

Methods

The transcriptome data and clinical data of breast cancer were collected from The Cancer Genome Atlas (TCGA), and the immune scores and stromal scores were calculated by ESTIMATE algorithm. The differentially expressed genes were screened base on immune and stromal scores (high score vs. low score), than the intersected genes were used for subsequent functional enrichment analysis and protein-protein interaction (PPI) analysis. Furthermore, the key gene was identified by the intersection of the hub genes of PPI network and the prognostic genes of breast cancer. Finally, we explored the infiltration of immune cells of BRCA base on the CIBERSORT algorithm, and analysis the relationship between key gene and immune cells.

Results

High levels of CD52 expression were detected in the early stages of breast cancer and were associated with favorable prognosis. Overexpression of CD52 led to higher infiltrations of M1 macrophages, monocytes, T follicular helper cells, and resting memory CD4 T cells. Downregulation of CD52 resulted in high infiltrations of M2 macrophages. Therefore, high expression of CD52 may negatively regulate the infiltration of M2 macrophages but accelerate the infiltration of anti-cancer immune cells, and thus, high expression of CD52 may have a protective effect in breast cancer patients.

Conclusions

CD52 can increase the infiltration of anti-cancer immune cells but inhibit the infiltration of M2 macrophages, thereby improving the prognosis of breast cancer patients.

Advances and Perspectives in the Treatment of T-PLL

PURPOSE OF REVIEW

T cell prolymphocytic leukemia (T-PLL) is a rare mature T cell tumor. Available treatment options in this aggressive disease are largely inefficient and patient outcomes are highly dissatisfactory. Current therapeutic strategies mainly employ the CD52-antibody alemtuzumab as the most active single agent. However, sustained remissions after sole alemtuzumab-based induction are exceptions. Responses after available second-line strategies are even less durable. More profound disease control or rare curative outcomes can currently only be expected after a consolidating allogeneic hematopoietic stem cell transplantation (allo-HSCT) in best first response. However, only 30-50% of patients are eligible for this procedure. Major advances in the molecular characterization of T-PLL during recent years have stimulated translational studies on potential vulnerabilities of the T-PLL cell. We summarize here the current state of "classical" treatments and critically appraise novel (pre)clinical strategies.

RECENT FINDINGS

Alemtuzumab-induced first remissions, accomplished in ≈ 90% of patients, last at median ≈ 12 months. Series on allo-HSCT in T-PLL, although of very heterogeneous character, suggest a slight improvement in outcomes among transplanted patients within the past decade. Dual-action nucleosides such as bendamustine or cladribine show moderate clinical activity as single agents in the setting of relapsed or refractory disease. Induction of apoptosis via reactivation of p53 (e.g., by inhibitors of HDAC or MDM2) and targeting of its downstream pathways (i.e., BCL2 family antagonists, CDK inhibitors) are promising new approaches. Novel strategies also focus on inhibition of the JAK/STAT pathway with the first clinical data. Implementations of immune-checkpoint blockades or CAR-T cell therapy are at the stage of pre-clinical assessments of activity and feasibility. The recommended treatment strategy in T-PLL remains a successful induction by infusional alemtuzumab followed by a consolidating allo-HSCT in eligible patients. Nevertheless, long-term survivors after this "standard" comprise only 10-20%. The increasingly revealed molecular make-up of T-PLL and the tremendous expansion of approved targeted compounds in oncology represent a "never-before" opportunity to successfully tackle the voids in T-PLL. Approaches, e.g., those reinstating deficient cell death execution, show encouraging pre-clinical and first-in-human results in T-PLL, and urgently have to be transferred to systematic clinical testing.

CCR7 as a novel therapeutic target in t-cell PROLYMPHOCYTIC leukemia

T-cell prolymphocytic leukemia (T-PLL) is a poor prognostic disease with very limited options of efficient therapies. Most patients are refractory to chemotherapies and despite high response rates after alemtuzumab, virtually all patients relapse. Therefore, there is an unmet medical need for novel therapies in T-PLL. As the chemokine receptor CCR7 is a molecule expressed in a wide range of malignancies and relevant in many tumor processes, the present study addressed the biologic role of this receptor in T-PLL. Furthermore, we elucidated the mechanisms of action mediated by an anti-CCR7 monoclonal antibody (mAb) and evaluated whether its anti-tumor activity would warrant development towards clinical applications in T-PLL. Our results demonstrate that CCR7 is a prognostic biomarker for overall survival in T-PLL patients and a functional receptor involved in the migration, invasion, and survival of leukemic cells. Targeting CCR7 with a mAb inhibited ligand-mediated signaling pathways and induced tumor cell killing in primary samples. In addition, directing antibodies against CCR7 was highly effective in T-cell leukemia xenograft models. Together, these findings make CCR7 an attractive molecule for novel mAb-based therapeutic applications in T-PLL, a disease where recent drug screen efforts and studies addressing new compounds have focused on chemotherapy or small molecules.

Intrathecal alemtuzumab: a potential treatment of refractory leptomeningeal T-cell prolymphocytic leukemia

This is the first report of successful treatment of therapy-resistant leptomeningeal T-PLL with intrathecal alemtuzumab. Intrathecal alemtuzumab is a potentially safe and efficacious therapeutic alternative for treatment of leptomeningeal T-PLL.

Current understandings on T-cell prolymphocytic leukemia and its association with TCL1 proto-oncogene

T-cell prolymphocytic leukemia (T-PLL) is a rare mature T cell leukemia with aggressive clinical course, poor response to conventional therapies and high mortality rates. Classical cytogenetics and various genetic techniques have observed complex karyotypes and associated genes involved in the molecular pathogenesis of T-PLL, among which the proto-oncogene T-cell leukemia/lymphoma 1 (TCL1) as a hallmark of malignancy is hyper-activated and abnormally expressed in many T-PLL cases. Progress has been made to identify the presence of chromosomal rearrangements and subsequent changes in key molecular pathways typically involving Akt, which may hint cytogenetic mechanisms underlying the pathogenesis of T-PLL and indicate new treatment targets. In this article, we describe current insights of T-PLL with an emphasis on the potential role of TCL1 gene disorders and TCL1-Akt interactions in cell transformation and disease progression, followed by discussion on current treatment options and novel therapeutic approaches based on cytogenetics, which still remains to be explored for the effective management of T-PLL and other TCL1-driven hematological malignancies.

Consensus criteria for diagnosis, staging, and treatment response assessment of T-cell prolymphocytic leukemia

T-cell prolymphocytic leukemia (T-PLL) is a rare, mature T-cell neoplasm with a heterogeneous clinical course. With the advent of novel treatment options that will potentially change the management of patients with T-PLL, it has become necessary to produce consensus guidelines for the design and conduct of clinical trials. The T-PLL International Study group (TPLL-ISG) set out to define standardized criteria for diagnosis, treatment indication, and evaluation of response. These criteria will facilitate comparison of results from clinical trials in T-PLL, and will thus support clinical decision making, as well as the approval of new therapeutics by healthcare authorities.

B and T cell prolymphocytic leukaemia

Prolymphocytic leukaemias B-PLL and T-PLL are rare disorders, typically with an aggressive clinical course and poor prognosis. Combining morphology, immunophenotyping, cytogenetic and molecular diagnostics reliably separates B-PLL and T-PLL from one another and other disorders. In T-PLL discovery of frequent mutations in the JAK-STAT pathway have increased understanding of disease pathogenesis. Alemtuzumab (anti-CD52) produces excellent response rates but long-term remissions are only achieved in a minority following consolidation with allogeneic stem cell transplant. Molecular abnormalities in B-PLL are less understood. Disruption of TP53 is a key finding, conveying chemotherapy resistance requiring novel therapies such as B-cell receptor inhibitors (BCRi). Both conditions require improved pathobiological knowledge to identify new treatment targets and guide therapy with novel pathway inhibitors.

Advances in the understanding and management of T-cell prolymphocytic leukemia

T-prolymphocytic leukemia (T-PLL) is a rare T-cell neoplasm with an aggressive clinical course. Leukemic T-cells exhibit a post-thymic T-cell phenotype (Tdt-, CD1a-, CD5+, CD2+ and CD7+) and are generally CD4+/CD8-, but CD4+/CD8+ or CD8+/CD4- T-PLL have also been reported. The hallmark of T-PLL is the rearrangement of chromosome 14 involving genes for the subunits of the T-cell receptor (TCR) complex, leading to overexpression of the proto-oncogene TCL1. In addition, molecular analysis shows that T-PLL exhibits substantial mutational activation of the IL2RG-JAK1-JAK3-, STAT5B axis. T-PLL patients have a poor prognosis, due to a poor response to conventional chemotherapy. Monoclonal antibody therapy with antiCD52-alemtuzumab has considerably improved outcomes, but the responses to treatment are transient; hence, patients who achieve a response to therapy are considered for stem cell transplantation (SCT). This combined approach has extended the median survival to four years or more. Nevertheless, new approaches using well-tolerated therapies that target growth and survival signals are needed for most patients unable to receive intensive chemotherapy.

CD4+ CD52lo T-cell expression contributes to the development of systemic lupus erythematosus

The cell-surface glycoprotein CD52 is widely expressed in lymphocytes. CD4⁺CD52^hi T cells are functioning suppressor CD4⁺T cells. We investigated the role of the immune regulation of CD4⁺CD52 T cells in systemic lupus erythematosus (SLE). CD4⁺CD52^lo T cells were increased in SLE patients, in positive correlation with SLEDAI, anti-ds-DNA antibody, and IgG concentration. Circulating follicular helper-like T cells (Tfh-like cells) were also increased in SLE, in positive correlation with CD4⁺CD52^lo T cells. Chemokine receptor 8 (CCR8) expression in CD4⁺CD52^lo T cells was increased. In vitro experiments using CD4 T cells of SLE patients showed that thymus and activation-regulated chemokine (TARC), a ligand of CCR8, contributed to the development of CD4⁺CD52^hi T cells into CD4⁺CD52^lo T cells. Our findings suggest that CD4+CD52lo T-cell upregulation is involved in the production of pathogens by autoantibodies, and TARC may contribute to the development of SLE through an aberrant induction of CD4⁺CD52^lo T cells.

First-in-human response of BCL-2 inhibitor venetoclax in T-cell prolymphocytic leukemia

T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive T-lymphoid malignancy usually refractory to current treatment strategies and associated with short overall survival. By applying next-generation functional testing of primary patient-derived lymphoma cells using a library of 106 US Food and Drug Administration (FDA)-approved anticancer drugs or compounds currently in clinical development, we set out to identify novel effective treatments for T-PLL patients. We found that the B-cell lymphoma 2 (BCL-2) inhibitor venetoclax (ABT-199) demonstrated the strongest T-PLL-specific response when comparing individual ex vivo drug response in 86 patients with refractory hematologic malignancies. Mechanistically, responses to venetoclax correlated with protein expression of BCL-2 but not with expression of the BCL-2 family members myeloid cell leukemia 1 (MCL-1) and BCL-XL in lymphoma cells. BCL-2 expression was inversely correlated with the expression of MCL-1. Based on the ex vivo responses, venetoclax treatment was commenced in 2 late-stage refractory T-PLL patients resulting in clinical responses. Our findings demonstrate first evidence of single-agent activity of venetoclax both ex vivo and in humans, offering a novel agent in T-PLL.

The Diagnosis, Management, and Role of Hematopoietic Stem Cell Transplantation in Aggressive Peripheral T-Cell Neoplasms

Background

Peripheral T-cell neoplasms (PTCNs) comprise a group of uncommon and heterogeneous lymphoid malignancies. They are more difficult to diagnose and treat and have a worse prognosis than B-cell lymphomas. Although PTCNs initially show a significant degree of chemosensitivity, the outcome of treatment with conventional dose chemotherapy remains poor.

Methods

We reviewed the literature on the diagnosis, treatment, and collective transplant reports regarding PTCNs.

Results

The correct diagnosis of peripheral T-cell lymphoma requires a combination of clinical presentation, morphology, immunophenotype, and molecular study. While no specific treatment other than conventional dose chemotherapy is currently available for aggressive PTCN, histone acetylase inhibitors and monoclonal antibodies such as anti-CD7 and anti-CD52 are being studied in T-cell malignancies. The role of autologous and allogeneic transplantation is being investigated for high-risk, relapsed, and refractory PTCNs with some promising results.

Conclusions

Access to hematopathology expertise in a tertiary care setting may lead to earlier and more accurate diagnoses of these diseases. PTCNs comprise a heterogeneous group of diseases with no widely accepted standard of care, and accurate determination of their histologic subtypes correlates with prognosis. Patients in first complete remission with poor risk features and patients with relapsed and refractory disease should be considered for bone marrow transplant due to the poor outcomes obtained with conventional chemotherapy.

Alemtuzumab

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Brentuximab Vedotin Therapy for Cutaneous Lesions in T-Prolymphocytic Leukemia: A Case Report

We present an 88-year-old male with simultaneous T-cell prolymphocytic leukemia and stable smoldering myeloma with excellent initial response to three months of alemtuzumab. The patient relapsed at twelve months with severe cutaneous disease. Biopsy of a representative plaque demonstrated CD30 positivity in rare malignant lymphocytes. The patient demonstrated no response to reintroduction with a full course of alemtuzumab. He was therefore treated with brentuximab vedotin, resulting in partial remission of skin involvement that persisted for three months.

Alemtuzumab (Campath-1H, Campath1) for the treatment of lymphoid malignancies: chronic lymphocytic leukemia and T-cell prolymphocytic leukemia

Objective. To provide a comprehensive review of the clinical pharmacology and toxicology of the monoclonal antibody alemtuzumab, with particular reference to its use in its approved indication, B-cell chronic lymphocytic leukemia, as well as the non-approved indication, T-cell prolymphocytic leukemia.

Data Sources. A MEDLINE search was conducted using the terms ‘alemtuzumab’ and ‘Campath.’ All data available from MEDLINE were reviewed. The reference lists from retrieved articles were reviewed and other relevant papers identified. The abstract books from the annual meetings of the American Society of Hematology were also reviewed.

Data Extraction. The aim of the review was to be comprehensive and descriptive. Studies containing information deemed to be of interest were reviewed by the author.

Data Summary. CD52 is a surface antigen expressed on all B- and T-lymphocytes. Because of the presence of this surface antigen on both normal and malignant lymphocytes, the use of antibody as a treatment option is then possible. Alemtuzumab (Campath-1H, Campath1) is a humanized anti- CD52 antibody that has been shown to be active against certain hematological malignancies, particularly lymphoproliferative diseases in the blood. The overall response rate for patients with chronic lymphocytic leukemia relapsed after fludarabine or alkylating therapy ranged from 33% to 70%, with most patients entering partial remission. The average duration of response is approximately 11 - 12 months. For patients with T-cell prolymphocytic leukemia failed first-line chemotherapy, overall response rate to alemtuzumab therapy ranged from 76% to 31%, with majority of patients entering complete remission. The average duration of response is approximately 7-9 months. Major adverse effects of alemtuzumab include infusion-related reactions, prolonged lymphopenia, and opportunistic infections (CMV, Herpes zoster, and PCP). Prophylactic use of acyclovir and trimethroprim/sulfamethoxazole are recommended while patient is receiving alemtuzumab and continued for 2 months after alemtuzumab therapy is completed.

Phase II Study of Alemtuzumab (CAMPATH-1) in Patients with HTLV-1-Associated Adult T-cell Leukemia/lymphoma

PURPOSE

Therapeutic regimens for adult T-cell leukemia/lymphoma (ATL) are limited with unsatisfactory results, thereby warranting development of novel therapies. This study investigated antitumor activity and toxicity of alemtuzumab with regard to response, duration of response, progression-free survival, and overall survival in patients with human T-cell lymphotropic virus-1 (HTLV-1)-associated ATL.

EXPERIMENTAL DESIGN

Twenty-nine patients with chronic, acute, and lymphomatous types of ATL were enrolled in a single-institution, nonrandomized, open-label phase II trial wherein patients received intravenous alemtuzumab 30 mg three times weekly for a maximum of 12 weeks.

RESULTS

Twenty-nine patients were evaluable for response and toxicity. The overall objective response was 15 of 29 patients [95% confidence interval (CI), 32.5%-70.6%]. The 15 patients who responded manifested a median time to response of 1.1 months. Median response duration was 1.4 months for the whole group and 14.5 months among responders. Median progression-free survival was 2.0 months. Median overall survival was 5.9 months. The most common adverse events were 2 with vasovagal episodes (7%) and 3 with hypotensive episodes (10%), leukopenia (41%) grade 3 and (17%) grade 4, lymphocytopenia (59%) grade 3, neutropenia (31%) grade 3, anemia (24%), and thrombocytopenia (10%). All patients developed cytomegalovirus antigenemia (CMV). Three were symptomatic and all responded to antiviral therapy. Grade 3 or 4 infections were reported in 4 (14%) of patients.

CONCLUSIONS

Alemtuzumab induced responses in patients with acute HTLV-1-associated ATL with acceptable toxicity, but with short duration of responses. These studies support inclusion of alemtuzumab in novel multidrug therapies for ATL. Clin Cancer Res; 23(1); 35-42. ©2016 AACR.

Mature T-cell leukemias: Molecular and Clinical Aspects

Mature T-cell leukemias are a group of uncommon lymphoid neoplasms. These disorders have widely variable clinical features, ranging from indolent, slowly progressive processes to diseases with rapidly progressive courses, leading to death. Cytogenetic aberrations have long been identified in some of these diseases, and recent studies have found recurrent genetic mutations that contribute to their pathogenesis. Conventional multiagent chemotherapy lacks significant efficacy in this group of diseases and therapies vary from immunosuppression to treatment with monoclonal antibodies, antiviral agents, and hematopoietic stem cell transplantation. The recent expansion of knowledge regarding the underlying genetic basis of these disorders raises hope that new, more targeted therapeutic approaches will be available to patients in the near future.

Characterisation of a Novel Anti-CD52 Antibody with Improved Efficacy and Reduced Immunogenicity

Anti-CD52 therapy has been shown to be effective in the treatment of a number of B cell malignancies, hematopoietic disorders and autoimmune diseases (including rheumatoid arthritis and multiple sclerosis); however the current standard of treatment, the humanized monoclonal antibody alemtuzumab, is associated with the development of anti-drug antibodies in a high proportion of patients. In order to address this problem, we have identified a novel murine anti-CD52 antibody which has been humanized using a process that avoids the inclusion within the variable domains of non-human germline MHC class II binding peptides and known CD4+ T cell epitopes, thus reducing its potential for immunogenicity in the clinic. The resultant humanized antibody, ANT1034, was shown to have superior binding to CD52 expressing cells than alemtuzumab and was more effective at directing both antibody dependent and complement dependent cell cytotoxicity. Furthermore, when in the presence of a cross-linking antibody, ANT1034 was more effective at directly inducing apoptosis than alemtuzumab. ANT1034 also showed superior activity in a SCID mouse/human CD52 tumour xenograft model where a single 1 mg/Kg dose of ANT1034 led to increased mouse survival compared to a 10 mg/Kg dose of alemtuzumab. Finally, ANT1034 was compared to alemtuzumab in in vitro T cell assays in order to evaluate its potential to stimulate proliferation of T cells in peripheral blood mononuclear cells derived from a panel of human donors: whereas alemtuzumab stimulated proliferation in a high proportion of the donor cohort, ANT1034 did not stimulate proliferation in any of the donors. Therefore we have developed a candidate therapeutic humanized antibody, ANT1034, that may have the potential to be more efficacious and less immunogenic than the current standard anti-CD52 therapy.

Impact of Alemtuzumab Therapy and Route of Administration in T-Prolymphocytic Leukemia: A Single-Center Experience

OBJECTIVE

We conducted a single-center retrospective analysis to determine the impact of the anti-CD52 monoclonal antibody alemtuzumab including route of administration compared to non-alemtuzumab-containing regimens in T-prolymphocytic leukemia (T-PLL).

PATIENTS AND METHODS

The study was a retrospective analysis of a consecutive cohort of adult patients diagnosed with T-PLL at Mayo Clinic Rochester from January 1, 1997, through September 30, 2014.

RESULTS

A total of 41 patients were diagnosed with T-PLL per the World Health Organization 2008 classification. The median age was 66 years, and 23 (56%) were male. After a median follow-up of 18 months (range, 0.4-66.1 months), 32 patients (78%) had died, with a median overall survival of 16.9 months. Approximately half the cohort was treated with alemtuzumab, almost exclusively after 2004. Median survival for patients receiving intravenous alemtuzumab-based therapy was 40.5 versus 10.3 months for all other therapies (P = .0004). A significant survival difference between intravenous versus subcutaneous alemtuzumab administration of 40.5 versus 13.7 months was noted (P = .0014). Only 4 (14%) of 28 patients aged < 70 years underwent hematopoietic stem cell transplantation, with a median survival after transplantation of 4 months.

CONCLUSION

In this large series of T-PLL patients treated at a single tertiary-care center, we confirmed the prior observation of the superiority of intravenous alemtuzumab over other therapies. Hematopoietic stem cell transplantation was feasible in a minority of potentially eligible patients. Early transplant referral should be considered for all eligible patients.

A pediatric case of T-cell prolymphocytic leukemia

T-cell Prolymphocytic Leukemia (T-PLL) is a rare entity, and to date has never been reported in children. Here, we describe the first pediatric case of T-PLL in a 16-year old male and review his clinical course through treatment. He underwent therapy with alemtuzumab and pentostatin, which was successful in inducing initial remission. He then underwent an allogeneic matched sibling stem cell transplant following a myeloablative conditioning regimen and remains disease-free 1.5 years after diagnosis.

A γ/δ T-cell receptor prolymphocytic leukemia and CD4-/CD8- double-negative immunophenotype in a pediatric patient

T-cell prolymphocytic leukemia is a very rare neoplasm, peaking in the seventh decade. An extensive search failed to find any report of this malignancy in the pediatric population. The malignant cell is morphologically characterized by a high nucleocytopasmic ratio, condensed chromatin, a single nucleolus, and nongranular basophilic cytoplasm. Cells are usually positive for the α/β and only rarely to the γ/δ T-cell receptors. Most patients follow an aggressive clinical course, only some respond to anti-CD52. We present a 6-year-old boy with T-cell prolymphocytic leukemia. The malignant cells expressed a postthymic immunophenotype (CD4/CD8) and positivity for the γ/δ T-cell receptors. The child died after 8 months despite aggressive chemotherapy, anti-CD52, and an allogeneic bone marrow transplant.

T-cell prolymphocytic leukemia with extensive cardiovascular infiltrate leading to multiple myocardial infarctions and cardiac death

Lymphocytic neoplasm involving the heart is not common and usually presents with pericardial effusion or focal myocardial infiltration. Myocardial infarctions due to leukemic infiltration of the coronary arteries are rarely reported. We present the case of a 52-year-old Guatemalan man with a one-year history of untreated T-cell prolymphocytic leukemia. He was admitted to our hospital for chemotherapy and evaluation of a pulmonary cavitary lesion by wedge resection. During sedation, the patient experienced acute respiratory failure and hypovolemic shock, from which he could not be resuscitated. Autopsy revealed that leukemic cells extensively infiltrated the aorta, myocardium, and coronary arteries. The lumina of the 3 major coronary artery branches showed 70% to 95% stenosis, with multifocal remote myocardial infarctions. Tumor cells were also detected in the lungs and other organs. The acute cardiorespiratory insufficiency secondary to leukemia-particularly the extensive infiltration of the coronary arteries and myocardium, and the multiple myocardial infarctions-eventually resulted in cardiac death.

Differential reconstitution of T cell subsets following immunodepleting treatment with alemtuzumab (anti-CD52 monoclonal antibody) in patients with relapsing-remitting multiple sclerosis

Alemtuzumab (anti-CD52 mAb) provides long-lasting disease activity suppression in relapsing-remitting multiple sclerosis (RRMS). The objective of this study was to characterize the immunological reconstitution of T cell subsets and its contribution to the prolonged RRMS suppression following alemtuzumab-induced lymphocyte depletion. The study was performed on blood samples from RRMS patients enrolled in the CARE-MS II clinical trial, which was recently completed and led to the submission of alemtuzumab for U.S. Food and Drug Administration approval as a treatment for RRMS. Alemtuzumab-treated patients exhibited a nearly complete depletion of circulating CD4(+) lymphocytes at day 7. During the immunological reconstitution, CD4(+)CD25(+)CD127(low) regulatory T cells preferentially expanded within the CD4(+) lymphocytes, reaching their peak expansion at month 1. The increase in the percentage of TGF-β1-, IL-10-, and IL-4-producing CD4(+) cells reached a maximum at month 3, whereas a significant decrease in the percentages of Th1 and Th17 cells was detected at months 12 and 24 in comparison with the baseline. A gradual increase in serum IL-7 and IL-4 and a decrease in IL-17A, IL-17F, IL-21, IL-22, and IFN-γ levels were detected following treatment. In vitro studies have demonstrated that IL-7 induced an expansion of CD4(+)CD25(+)CD127(low) regulatory T cells and a decrease in the percentages of Th17 and Th1 cells. In conclusion, our results indicate that differential reconstitution of T cell subsets and selectively delayed CD4(+) T cell repopulation following alemtuzumab-induced lymphopenia may contribute to its long-lasting suppression of disease activity.

T-cell prolymphocytic leukaemia (T-PLL): a rare disease with a grave prognosis

T-cell prolymphocytic leukaemia (T-PLL) is an extremely uncommon haematological malignancy that has an aggressive course and a grave prognosis. We describe a patient who presented with lymphocytosis, scalp erythema, ascites and splenomegaly and was diagnosed with T-PLL. He was treated with alemtuzumab with a good response and was referred for allogeneic stem cell transplantation.

Sequential chemoimmunotherapy of fludarabine, mitoxantrone, and cyclophosphamide induction followed by alemtuzumab consolidation is effective in T-cell prolymphocytic leukemia

BACKGROUND

Scarce systematic trial data have prevented uniform therapeutic guidelines for T-cell prolymphocytic leukemia (T-PLL). A central need in this historically refractory tumor is the controlled evaluation of multiagent chemotherapy and its combination with the currently most active single agent, alemtuzumab.

METHODS

This prospective multicenter phase 2 trial assessed response, survival, and toxicity of a novel regimen in previously treated (n = 9) and treatment-naive (n = 16) patients with T-PLL. Induction by fludarabine, mitoxantrone, and cyclophosphamide (FMC), for up to 4 cycles, was followed by alemtuzumab (A) consolidation, up to 12 weeks.

RESULTS

Of the 25 patients treated with FMC, 21 subsequently received alemtuzumab. Overall response rate to FMC was 68%, comprising 6 complete remissions (all bone-marrow confirmed) and 11 partial remissions. Alemtuzumab consolidation increased the intent-to-treat overall response rate to 92% (12 complete remissions; 11 partial remissions). Median overall survival after FMC-A was 17.1 months and median progression-free survival was 11.9 months. Progression-free survival tended to be shorter for patients with high-level T-cell leukemia 1 oncoprotein expression. Hematologic toxicities were the most frequent grade 3/4 side effects under FMC-A. Exclusively in the 21 alemtuzumab-consolidated patients, 13 cytomegalovirus reactivations were observed; 9 of these 13 represented a clinically relevant infection.

CONCLUSIONS

FMC-A is a safe and efficient protocol in T-PLL, which compares favorably to published data.

Novel treatment avenues for peripheral T-cell lymphomas

INTRODUCTION

Peripheral T-cell lymphomas (PTCLs) and natural killer (NK) or T-cell non-Hodgkin's lymphomas (NHLs) are a rare and heterogeneous class of diseases with generally poor prognosis. This work intends to provide a focused primer on clinical diagnosis, current treatment regimens, and novel therapeutic approaches. The recent WHO classification has defined 18 different subtypes of PTCL and NK T-cell lymphomas. Diagnosis is mainly based on histology, flow-cytometric analysis of surface molecules in the blood and bone marrow, cytogenetics/fluorescence in situ hybridization (FISH), and T-cell receptor (TCR) rearrangement. Staging as well as follow-up diagnostic procedures rely on imaging techniques such as computerized tomography (CT) and positron emission tomography (PET). Current chemotherapeutic regimens such as CHOP result in a 60 - 70% response rate; however, 5-year survival is only around 30%. Therefore, new treatment strategies are urgently needed. Currently, different drug classes are under scrutiny.

AREAS COVERED

The authors discuss substances that directly target the tumor cells. The article includes such substances as antimetabolites, antibodies, histone deacetylase inhibitors, tyrosine kinase inhibitors, and immunomodulatory substances such as lenalidomide.

EXPERT OPINION

In the future a close collaboration of geneticists, biochemists, and clinicians together with new technologies such as deep sequencing will allow the refinement of treatment strategies in many diseases including PTCLs and NHLs. This refinement will allow treatments to be prepared according to the need of the individual patient.

Human peripheral blood mononuclear cells exhibit heterogeneous CD52 expression levels and show differential sensitivity to alemtuzumab mediated cytolysis

Alemtuzumab is a monoclonal antibody that targets cell surface CD52 and is effective in depleting lymphocytes by cytolytic effects in vivo. Although the cytolytic effects of alemtuzumab are dependent on the density of CD52 antigen on cells, there is scant information regarding the expression levels of CD52 on different cell types. In this study, CD52 expression was assessed on phenotypically distinct subsets of lymphoid and myeloid cells in peripheral blood mononuclear cells (PBMCs) from normal donors. Results demonstrate that subsets of PBMCs express differing levels of CD52. Quantitative analysis showed that memory B cells and myeloid dendritic cells (mDCs) display the highest number while natural killer (NK) cells, plasmacytoid dendritic cells (pDCs) and basophils have the lowest number of CD52 molecules per cell amongst lymphoid and myeloid cell populations respectively. Results of complement dependent cytolysis (CDC) studies indicated that alemtuzumab mediated profound cytolytic effects on B and T cells with minimal effect on NK cells, basophils and pDCs, correlating with the density of CD52 on these cells. Interestingly, despite high CD52 levels, mDCs and monocytes were less susceptible to alemtuzumab-mediated CDC indicating that antigen density alone does not define susceptibility. Additional studies indicated that higher expression levels of complement inhibitory proteins (CIPs) on these cells partially contributes to their resistance to alemtuzumab mediated CDC. These results indicate that alemtuzumab is most effective in depleting cells of the adaptive immune system while leaving innate immune cells relatively intact.

How I treat prolymphocytic leukemia

T- and B-cell subtypes of prolymphocytic leukemia (PLL) are rare, aggressive lymphoid malignancies with characteristic morphologic, immunophenotypic, cytogenetic, and molecular features. Recent studies have highlighted the role of specific oncogenes, such as TCL-1, MTCP-1, and ATM in the case of T-cell and TP53 mutations in the case of B-cell prolymphocytic leukemia. Despite the advances in the understanding of the biology of these conditions, the prognosis for these patients remains poor with short survival and no curative therapy. The advent of monoclonal antibodies has improved treatment options. Currently, the best treatment for T-PLL is intravenous alemtuzumab, which has resulted in very high response rates of more than 90% when given as first-line treatment and a significant improvement in survival. Consolidation of remissions with autologous or allogeneic stem cell transplantation further prolongs survival, and the latter may offer potential cure. In B-PLL, rituximab-based combination chemo-immunotherapy is effective in fitter patients. TP53 abnormalities are common and, as for chronic lymphocytic leukemia, these patients should be managed using an alemtuzumab-based therapy. The role of allogeneic transplant with nonmyeloablative conditioning needs to be explored further in both T- and B-cell PLL to broaden the patient eligibility for what may be a curative treatment.

Alemtuzumab therapy in T-cell prolymphocytic leukemia: comparing efficacy in a series treated intravenously and a study piloting the subcutaneous route

Intravenous alemtuzumab is an effective and well-tolerated treatment for T-cell prolymphocytic leukemia (T-PLL). Alemtuzumab given intravenously as first-line treatment in 32 patients resulted in an overall response rate of 91% with 81% complete responses. Studies in B-cell chronic lymphocytic leukemia have shown subcutaneous alemtuzumab to be equally as effective as intravenous alemtuzumab. The UKCLL05 pilot study examined the efficacy and toxicity of this more convenient method of administration in 9 previously untreated patients with T-PLL. Only 3 of 9 patients (33%) responded to treatment. Furthermore, 2 of 9 patients (22%) died while on treatment. Recruitment was terminated because of these poor results. After rescue therapy with intravenous alemtuzumab and/or pentostatin, median progression-free survival and overall survival were similar to the intravenous group. Alemtuzumab delivered intravenously, but not subcutaneously, remains the treatment of choice for previously untreated T-PLL.

Cancer immunotherapy

Cancer immunotherapy consists of approaches that modify the host immune system, and/or the utilization of components of the immune system, as cancer treatment. During the past 25 years, 17 immunologic products have received regulatory approval based on anticancer activity as single agents and/or in combination with chemotherapy. These include the nonspecific immune stimulants BCG and levamisole; the cytokines interferon-α and interleukin-2; the monoclonal antibodies rituximab, ofatumumab, alemtuzumab, trastuzumab, bevacizumab, cetuximab, and panitumumab; the radiolabeled antibodies Y-90 ibritumomab tiuxetan and I-131 tositumomab; the immunotoxins denileukin diftitox and gemtuzumab ozogamicin; nonmyeloablative allogeneic transplants with donor lymphocyte infusions; and the anti-prostate cancer cell-based therapy sipuleucel-T. All but two of these products are still regularly used to treat various B- and T-cell malignancies, and numerous solid tumors, including breast, lung, colorectal, prostate, melanoma, kidney, glioblastoma, bladder, and head and neck. Positive randomized trials have recently been reported for idiotype vaccines in lymphoma and a peptide vaccine in melanoma. The anti-CTLA-4 monoclonal antibody ipilumumab, which blocks regulatory T-cells, is expected to receive regulatory approval in the near future, based on a randomized trial in melanoma. As the fourth modality of cancer treatment, biotherapy/immunotherapy is an increasingly important component of the anticancer armamentarium.

CD52 as a molecular target for immunotherapy to treat acute myeloid leukemia with high EVI1 expression

Ecotropic viral integration site 1 (EVI1) is an oncogenic transcription factor in human acute myeloid leukemia (AML) with chromosomal alterations at 3q26. Because a high expression of EVI1 protein in AML cells predicts resistance to chemotherapy with a poor outcome, we have searched for molecular targets that will treat these patients with AML. In this study, we determined that CD52, which is mainly expressed on lymphocytes, is highly expressed in most cases of AML with a high EVI1 expression (EVI1(High)). CAMPATH-1H, a humanized monoclonal antibody against CD52, has been used to prevent graft-versus-host disease and treat CD52-positive lymphoproliferative disorders. Here, we investigated the antitumor effect of CAMPATH-1H on EVI1(High) AML cells. CAMPATH-1H significantly inhibited cell growth and induced apoptosis in CD52-positive EVI1(High) leukemia cells. Furthermore, CAMPATH-1H induced complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity against CD52-positive EVI1(High) leukemia cells. After an intravenous injection of CAMPATH-1H into NOD/Shi-scid/IL-2Rγ;null mice with subcutaneous engraftment of EVI1(High) leukemia cells, tumor growth rates were significantly reduced, and the mice survived longer than those in the phosphate-buffered saline-injected control group. Thus, CAMPATH-1H is a potential therapeutic antibody for the treatment of patients with EVI1(High) leukemia.

Intensified alemtuzumab-CHOP therapy for peripheral T-cell lymphoma

BACKGROUND

The prognosis of T-cell lymphoma is poor. To explore the addition of the monoclonal antibody alemtuzumab, we studied the efficacy and tolerability of an intensified alemtuzumab-chemotherapy combination for aggressive T-cell lymphoma in a phase II study by Dutch-Belgian Hemato-Oncology Group (HOVON).

PATIENTS AND METHODS

Patients (≤65 years) with newly diagnosed T-cell lymphoma received eight CHOP cycles (cyclophosphamide, doxorubicin, vincristine, prednisone) 2-weekly, each cycle with three doses of 30 mg alemtuzumab. Prophylaxis consisted of cotrimoxazole, fluconazole and valaciclovir. Cytomegalovirus (CMV) monitoring took place at least every fortnight.

RESULTS

Twenty patients from 10 centers, median age 50 years, were included. Eighty-five percent received six or more cycles. The overall response was 90% [12 complete remissions (CRs), 1 CR unconfirmed, 5 partial remissions]. Median duration of follow-up of patients still alive was 29 months (range 19-41 months). Median overall survival (OS) and event-free survival (EFS) were 27 and 10 months, with 55%/27% OS/EFS at 2 years. Adverse events consisted of neutropenic fever (n = 8) and CMV reactivation (n = 7), with one CMV disease. Three patients developed secondary Epstein-Barr virus (EBV)-related lymphoma, all after end of treatment.

CONCLUSIONS

Although intensified alemtuzumab-CHOP induces high responses, many patients relapse, and the scheme is associated with serious infection-related adverse events. EBV monitoring after end of treatment is required.

T-cell prolymphocytic leukemia: A rare disease in an elderly female

PURPOSE

To present a case report of an 83-year-old female with underlying dementia and a 1-2 month history of left upper quadrant pain. This report includes a review of the morphology of T-cell prolymphocytic leukemia (PLL), diagnosis, and the treatment options considered.

DATA SOURCES

T-cell PLL is a rare blood disorder that represents a very small number of all chronic leukemias. An extensive review of scientific literature related to the cell morphology and pathology of this disease, as well as clinical trials of treatment options provided the background for this case report.

CONCLUSION

A diagnosis of T-cell PLL was made after a computed tomography scan of the abdomen confirmed splenomegaly and a bone marrow biopsy showed a hypercellular marrow infiltrated with numerous small lymphocytes, consistent with this disease. Currently, there is no optimal treatment for T-cell PLL, but alemtuzumab has shown success with extending survival 1-3 years.

IMPLICATIONS FOR PRACTICE

This case presented several ethical and practical challenges for this patient and her family in making a decision for chemotherapy treatment. This case underscores the need for the physicians and nurse practitioners to establish a collaborative relationship with patient, family, and other care providers when advocating for or against treatment.

Involvement of neutrophils and natural killer cells in the anti-tumor activity of alemtuzumab in xenograft tumor models

Alemtuzumab is a recombinant humanized IgG1 monoclonal antibody directed against CD52, an antigen expressed on the surface of normal and malignant B and T lymphocytes. Alemtuzumab is approved for the treatment of B-cell chronic lymphocytic leukemia (B-CLL), but the exact mechanism by which the antibody depletes malignant lymphocytes in vivo is not clearly defined. To address this issue, the anti-tumor activity of alemtuzumab was studied in disseminated and subcutaneous xenograft tumor models. The density of CD52 target antigen on the surface of tumor cells appeared to correlate with the anti-tumor activity of alemtuzumab. Deglycosylation of alemtuzumab resulted in a loss of cytotoxicity in vitro and was found to abolish anti-tumor activity in vivo. Individual inactivation of effector mechanisms in tumor-bearing mice indicated that the protective activity of alemtuzumab in vivo was primarily dependent on ADCC mediated by neutrophils and to a lesser extent NK cells. Increasing the number of circulating neutrophils by treatment with G-CSF enhanced the anti-tumor activity of the antibody, thus providing further evidence for the involvement of neutrophils as effector cells in the activity of alemtuzumab.

Allogeneic hematopoietic cell transplant for prolymphocytic leukemia

The poor prognosis of patients with prolymphocytic leukemia (PLL) has led some clinicians to recommend allogeneic hematopoietic cell transplant (HCT). However, the data to support this approach is limited to case-reports and small case series. We reviewed the database of the Center for International Blood and Marrow Transplant Research (CIBMTR) to determine outcomes after allotransplant for patients with PLL. We identified 47 patients with a median age of 54 years (range: 30-75 years). With a median follow-up of 13 months, progression-free survival (PFS) was 33% (95% confidence interval [CI] 20%-47%) at 1 year. The most common cause of death was relapse or progression in 49%. The cumulative incidence of treatment-related mortality (TRM) at 1-year posttransplant was 28%. The small patient population prohibited prognostic factor analysis, but these data support consideration of allotransplant for PLL. Further study of a larger population of patients is needed to determine which patients are more likely to benefit.

Antibody-based therapy of leukaemia

Over the past decade, monoclonal antibodies have dramatically impacted the treatment of haematological malignancies, as evidenced by the effect of rituximab on the response rate and survival of patients with follicular and diffuse large B cell non-Hodgkin's lymphoma. Currently, only two monoclonal antibodies - the anti-CD33 immunotoxin gemtuzumab ozogamicin and the CD52-directed antibody alemtuzumab - are approved for treatment of relapsed acute myeloid leukaemia in older patients and B cell chronic lymphocytic leukaemia, respectively. Although not approved for such treatment, alemtuzumab is also active against T cell prolymphocytic leukaemia, cutaneous T cell lymphoma and Sézary syndrome, and adult T cell leukaemia and lymphoma. In addition, rituximab has demonstrated activity against B cell chronic lymphocytic and hairy cell leukaemia. Monoclonal antibodies targeting CD4, CD19, CD20, CD22, CD23, CD25, CD45, CD66 and CD122 are now being studied in the clinic for the treatment of leukaemia. Here, we discuss how these new antibodies have been engineered to reduce immunogenicity and improve antibody targeting and binding. Improved interactions with Fc receptors on immune effector cells can enhance destruction of target cells through antibody-dependent cellular cytotoxicity and complement-mediated cell lysis. The antibodies can also be armed with cellular toxins or radionuclides to enhance the destruction of leukaemia cells.

Maintenance Therapy with a Monthly Injection of Alemtuzumab Prolongs Response Duration in Patients with Refractory B-cell Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (B-CLL/SLL)

Alemtuzumab, the monoclonal anti-CD52 antibody, has clinical activity in B-cell and T-cell malignancies at the dose of 30 mg three times weekly for 9-12 weeks. This standard regimen induced responses usually shorter than 6 months. To prolong time to progression, we initialized a phase II study with an identical initial scheme until partial response, followed by a maintenance therapy lasting at least 4 months. Eleven heavily pretreated patients (8 with B-chronic lymhocytic leukemia (B-CLL) and 3 with small lymphoctyic lymphoma (SLL)) have been treated with this maintenance regimen (MR patients) and were retrospectively compared to 5 patients (3 B-CLL and 2 SLL) treated with the standard regimen (SR patients). Patients characteristics before treatment were identical in both groups. Objective response was reached by 9 (82%) MR patients and 3 (60%) SR patients (p NS). After the treatment, 8 (73%) MR patients and all SR patients progressed with a median time at 12.2 months and 3 months respectively. Survival time from alemtuzumab was significatively different (P < 0.005). None of the patients died in the MR group with a median follow-up at 16 months. In the SR group, the median survival from alemtuzumab was 5.9 months. We did not observe any differences in terms of hematological toxicites and infections between the two groups. In conclusion, maintenance alemtuzumab therapy seems to increase the time to progression and the survival, without adding hematological toxicities and infectious complications. More patients are needed to confirm this observation.

Applications of monoclonal antibodies for the treatment of hematological malignancies

BACKGROUND

The introduction of mAbs has changed the clinical approach to patients with lymphoma and leukemia.

OBJECTIVE

To summarize the most significant applications of mAb-based regimens in the treatment of hematological malignancies and explore their possible role in the future management of these patients.

RESULTS

Rituximab (anti-CD20) was the first mAb developed for the treatment of B-cell lymphomas. Several randomized studies have demonstrated its efficacy in lymphomas and low toxicity profile; rituximab also has significant activity in chronic lymphocytic leukemia (CLL). Alemtuzumab (anti-CD52) has shown efficacy in previously untreated or refractory CLL patients, while gemtuzumab ozogamicin (anti-CD33) appears to have significant activity in acute myeloid leukemias and myelodysplastic syndromes.

CONCLUSIONS

In the next few years, investigations will be concentrated on the improvement of the older mAbs, and the development of new mAbs, targeting molecules important for malignant cell cycle and survival in an attempt to further improve patient survival.

Variable CD52 expression in mature T cell and NK cell malignancies: implications for alemtuzumab therapy

The anti-CD52 antibody alemtuzumab has been explored as a novel targeted therapy in T cell malignancies. To assess the suitability of alemtuzumab therapy, we carried out a comprehensive study of CD52 expression using flow cytometry (FC) in 78 untreated patients diagnosed with mature T/natural killer (NK) cell neoplasms, including 34 adult T cell leukaemia/lymphomas (ATLL), two anaplastic large cell lymphomas (ALCL), three angioimmunoblastic T cell lymphomas (AITL), 16 cutaneous T cell lymphomas (CTCL), four extra-nodal T/NK cell lymphomas (ENT/NKCL), four hepatosplenic T cell lymphomas (HSTCL), 13 peripheral T cell lymphomas, not otherwise specified (PTCL-NOS) and two T-prolymphocytic leukaemia (T-PLL). The level of CD52 expression was quantified using QuantiBRITE standard beads. The level of CD52 expression varied widely within each diagnostic category. All AITL, HSTCL and T-PLL cases were CD52-positive and the frequency of CD52 expression was high in PTCL-NOS (92.3%), ATLL (94.1%) and CTCL (87.5%), implying a rational role for alemtuzumab in the treatment of these diseases; however, CD52 expression was low in ALCL (50%) and ENT/NKCL (25%). FC testing for cell surface expression of CD52 is indicated in patients with T/NK cell malignancies being considered for alemtuzumab therapy. Further studies are necessary to determine if the level of CD52 expression correlates with response to therapy.