Treatment Of T-cell Malignancies Research Articles

Design, Synthesis, Biological Evaluation, and Crystallographic Study of Novel Purine Nucleoside Phosphorylase Inhibitors.

Purine nucleoside phosphorylase (PNP) is a well-known molecular target with potential therapeutic applications in the treatment of T-cell malignancies and/or bacterial/parasitic infections. Here, we report the design, development of synthetic methodology, and biological evaluation of a series of 30 novel PNP inhibitors based on acyclic nucleoside phosphonates bearing a 9-deazahypoxanthine nucleobase. The strongest inhibitors exhibited IC50 values as low as 19 nM (human PNP) and 4 nM (Mycobacterium tuberculosis (Mt) PNP) and highly selective cytotoxicity toward various T-lymphoblastic cell lines with CC50 values as low as 9 nM. No cytotoxic effect was observed on other cancer cell lines (HeLa S3, HL60, HepG2) or primary PBMCs for up to 10 μM. We report the first example of the PNP inhibitor exhibiting over 60-fold selectivity for the pathogenic enzyme (MtPNP) over hPNP. The results are supported by a crystallographic study of eight enzyme-inhibitor complexes and by ADMET profiling in vitro and in vivo.

Treatment of Aggressive T Cell Lymphoblastic Lymphoma/leukemia Using Anti-CD5 CAR T Cells

While treatment for B-cell malignancies has been revolutionized through the advent of CAR immunotherapy, similar strategies for T-cell malignancies have been limited. Additionally, T-cell leukemias and lymphomas can commonly metastasize to the CNS, where outcomes are poor and treatment options are associated with severe side effects. Consequently, the development of safer and more effective alternatives for targeting malignant T cells that have invaded the CNS remains clinically important. CD5 CAR has previously been shown to effectively target various T-cell cancers in preclinical studies. As IL-15 strengthens the anti-tumor response, we have modified CD5 CAR to secrete an IL-15/IL-15sushi complex. In a Phase I clinical trial, these CD5-IL15/IL15sushi CAR T cells were tested for safety and efficacy in a patient with refractory T-LBL with CNS infiltration. CD5-IL15/IL15sushi CAR T cells were able to rapidly ablate the CNS lymphoblasts within a few weeks, resulting in the remission of the patient’s lymphoma. Despite the presence of CD5 on normal T cells, the patient only experienced a brief, transient T-cell aplasia. These results suggest that CD5-IL15/IL15sushi CAR T cells may be a safe and useful treatment of T-cell malignancies and may be particularly beneficial for patients with CNS involvement.Graphical

Interleukin-15 (IL-5) in Combination with Avelumab in Relapsed/Refractory Mature T-Cell Malignancies

Background: Programmed death-ligand 1 (PD-L1) is expressed in many T-cell malignancies, including 75-100% of advanced cutaneous T-cell lymphomas, 75% of ALK-negaive anaplastic large cell lymphoma (ALCL), and 28% of peripheral T-cell lymphoma not otherwise specified (PTCL-NOS). In 27% of patients with adult T-cell leukemia/lymphoma (ATLL) expression of PD-L1 is upregulated through 3'-UTR disruption; however, immune checkpoint inhibition has been associated with hyperprogression in three patients with indolent ATLL. In T-cell malignancies, PD-L1 expression was associated with worse outcomes. Avelumab is a fully human IgG1 anti-PD-L1 antibody which inhibits PD-1/PD-L1 interactions; unlike other approved immune checkpoint inhibitors, it also induces lysis of tumor cells in vitro via antibody-dependent cell-mediated cytotoxicity (ADCC). As ADCC is mediated by natural killer (NK) cells, agents which increase NK cell number and activity may act sinergistically with avelumab. Administration of recombinant human (rh)IL-15 by continuous intravenous infusion (CIV) into adult cancer patients has produced a 15-75-fold expansion in the number of circulating NK cells at well-tolerated doses. Preclinical syngeneic and xenograft murine lymphoid malignancy models have shown increased efficacy with combined administration of IL-15 and anti-tumor antibodies compared to either alone. We therefore hypothesized that rhIL-15 may increase the efficacy of avelumab in PD-L1 expressing T-cell malignancies, and are testing the combination in a phase I trial. Primary objective: determine the safety, toxicity profile and the maximum tolerated dose of CIV IL- 15 administration in combination with with a fixed dose of avelumab. Secondary objectives: 1) determine the efficacy of combined CIV rhIL-15 and avelumab treatment to patients with T-cell lymphomas other than ATL (overal response, duration of response, progression-free survival, event-free survival, and overall survival), 2) correlate response with level of PD-L1 expression in tumor cells (<50% and ≥50%) 3) better understand the in vivo biological effects of avelumab and rhIL-15 treatment by analyzing changes in peripheral blood lymphocyte subsets, quantify ADCC performed ex vivo on PBMCs obtained from the patients, and examine treatment-related changes in tumor deposits by immunohistochemical and molecular analysis of core biopsies obtained before and during treatment. Exploratory objectives: 1) assess the role of circulating tumor DNA (ctDNA) in T-cell malignancies, 2) assess the role of exosomes in T-cell malignancies, 3) identify other potential biomarkers of response, such as cytokine levels and T-cell clonality. Eligibility criteria: 1) age ≥18 years, 2) histologically proven PTCL-NOS, ALK-negative ALCL, or mycosis fungoides/Sézary syndrome that is refractory to at least one line of systemic treatment, 3) ECOG ≤1, 4) WBC count ≥ 3 ⨉ 109/L, with absolute neutrophil count ≥ 1.0 ⨉ 109/L, lymphocyte count ≥ 0.5 x 109/L, platelet count ≥ 100 ⨉ 109/L, and hemoglobin ≥ 9 gm/dL (may have been transfused), 5) no prior treatment with drugs targeting PD-1/PD-L1, or receipt of any organ transplantation including allogeneic stem cell transplantation. Study design: Open-label, single-center, non-randomized Phase 1 study with a 3+3 phase dose escalation design enrolling up to 30 patients. IL-15 will be administered by continuous intravenous infusion with a dose of 1 mcg/kg/day (DL1), 2 mcg/kg/day (DL2), 3 mcg/kg/day (DL3), or 4 mcg/kg/day (DL4) on days 1-5 of each cycle. Avelumab 10 mg/kg IV over 1 hour)will be administered on days 8 and 22 of the cycle. Treatment will continue for a maximum of 6 cycles, or until toxicity or progressive disease. Correlative studies: tumor (skin or lymph node) biopsy at baseline and before the second dose of avelumab (C1D22); lymphocyte subset testing, ADCC capacity of ex vivo NK cells, ctDNA, exosomes, cell and plasma banking (days 1 and 8 of each cycle). One patients has been treated so far at DL1. Enrollment is ongoing. Figure Disclosures Waldmann: Bioniz: Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Avelumab off-label use for treatment of T-cell malignancies.

Abstract 2988: Loss of Rbm38 cooperates with mutant p53 to promote lymphomagenesis through downregulation of Pten

Abstract The tumor suppressor TP53 is the most commonly mutated gene in human cancers and mutant p53 has a gain of function by promoting tumor progression, metastasis, and resistance to anticancer therapy. Interestingly, the RNA binding protein Rbm38, a critical regulator of mutant p53 translation, is frequently lost in tumors with mutant p53. To determine the role of the Rbm38-mutant p53 axis in tumorigenesis, we showed that loss of Rbm38 significantly alters the cancer susceptibility of mutant p53 knockin mice by shortening the lifespan, altering the tumor incidence, and promoting T-cell lymphomagenesis. To understand how Rbm38 deficiency promotes mutant p53 gain of function, we showed that loss of Rbm38 not only enhances mutant p53 expression but also decreases expression of tumor suppressor Pten, a critical regulator of T-cell development. Furthermore, we showed that Rbm38 is required for Pten expression by stabilizing Pten mRNA through an AU-rich element in its 3'UTR. Thus, we have uncovered a novel mechanism by which Pten is regulated by Rbm38 via mRNA stability. Our data also suggest that Rbm38 controls T-cell lymphomagenesis by concomitantly modulating mutant p53 and Pten, which may be explored as a therapeutic strategy for the treatment of T-cell malignancies. Citation Format: Jin Zhang, Heejung yang, Yanhong Zhang, Mingyi Chen, Xinbin Chen. Loss of Rbm38 cooperates with mutant p53 to promote lymphomagenesis through downregulation of Pten [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2988.

Nelarabine in the treatment of pediatric and adult patients with T-cell acute lymphoblastic leukemia and lymphoma

ABSTRACTIntroduction: T-cell acute lymphoblastic leukemia (ALL) and lymphoma (LBL) are aggressive hematologic neoplasms that are treated with combination chemotherapy in the frontline, but have limited options in the relapsed or refractory setting. Based on observations in patients with purine nucleoside phosphorylase (PNP) deficiency, a guanosine nucleoside analogue, arabinosylguanine (ara-G) was developed that provided T-cell specificity. Nelarabine was developed as the water-soluble, clinically useful-prodrug of ara-G and based on its activity was approved for the treatment of relapsed or refractory T-ALL/LBL.Areas covered: In this narrative review, we will summarize the preclinical studies, early dose-finding studies, and efficacy studies that led to approval of nelarabine. The review will succinctly cover response rates and safety signals reported during clinical development. We will also cover more recent work with nelarabine, including combination studies, modified dosing schedules, and frontline treatment approaches.Expert commentary: Based on evidence from the literature review and our own experience with nelarabine, we conclude that it is an effective agent in the treatment of T-cell malignancies. Understanding the factors that modulate the risk of dose-limiting neurotoxicity, how to mitigate this toxicity, and how to safely combine it with other active agents will continue to broaden its use.

Targeting T-Cell Receptor β-Constant Domain for Immunotherapy of T-Cell Malignancies

T-cell lymphomas and leukemias are aggressive, treatment-resistant cancers with poor prognosis. Immunotherapeutic approaches have been limited by a lack of target antigens discriminating malignant from healthy T-cells. While treatment of B-cell cancers has been enhanced by targeting pan B-cell antigens, an equivalent approach is not possible for T-cell malignancies since profound T-cell depletion, unlike B-cell depletion, would be prohibitively toxic. We propose an immunotherapeutic strategy for targeting a pan T-cell antigen without causing severe depletion of normal T-cells.The α/β T-cell receptor (TCR) is a pan T-cell antigen, expressed on >90% of T-cell lymphomas and all normal T-cells. An overlooked feature of the TCR is that the β-constant region comprises 2 functionally identical genes: TRBC1 and TRBC2. Each T-cell expresses only one of these. Hence, normal T-cells will be a mixture of individual cells expressing either TRBC1 or 2, while a clonal T-cell cancer will express TRBC1 or 2 in its entirety.Despite almost identical amino acid sequences, we identified an antibody with unique TRBC1 specificity. Flow cytometry (FACS) of T-cells in normal donors (n = 27) and patients with T-cell cancers (n = 18) revealed all subjects had TRBC1 and 2 cells in both CD4 and CD8 compartments, with median TRBC1 expression of 35% (range 25-47%). In addition, we examined viral-specific T-cells in healthy volunteers, by generation of Epstein Barr virus-specific primary cytotoxic T-cell lines (3 donors) or by identification of cytomegalovirus-specific (3 donors) or adenovirus-specific (5 donors) T-cells by peptide stimulation. We demonstrated similar TRBC1: 2 ratios in viral-specific cells, suggesting that depletion of either subset would not remove viral immunity. Next, using FACS and immunohistochemistry, we showed that TCR+ cell lines (n = 8) and primary T-cell lymphomas and leukemias (n = 55) across a wide range of histological subtypes were entirely restricted to one compartment (34% TRBC1).As proof of concept for TRBC-selective therapy, we developed anti-TRBC1 chimeric antigen receptor (CAR) T-cells. After retroviral transduction of healthy donor T-cells, comprising mixed TRBC1/2 populations, 90% of T-cells expressed CAR on the cell surface. No detectable TRBC1 T-cells remained in the culture, suggesting selective depletion of this population. Anti-TRBC1 CAR T-cells secreted interferon-γ in response to TRBC1-expressing target cell lines (p<0.001) or autologous normal TRBC1+ cells (p<0.001), and not TRBC2 cell lines or autologous normal TRBC2 cells. Anti-TRBC1 CAR killed multiple TRBC1 cell lines (p<0.001) and autologous normal TRBC1 cells (p<0.001), and not TRBC2 cell lines or autologous normal TRBC2 cells. These cell-line based findings were confirmed using primary cells from two patients with TRBC1+ adult T-cell leukaemia/lymphoma. We demonstrated specific tumour kill by allogeneic or autologous T-cells in vitro, despite partial downregulation of surface TCR by tumour cells. We developed a xenograft murine model of disseminated T-cell leukemia by engrafting engineered firefly luciferase+ TRBC1+ Jurkat cells in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice. Bioluminescent imaging and FACS of marrow at 5 days following IV T-cell injection showed that while mice treated with untransduced T-cells progressed, mice receving anti-TRBC1 CAR T-cells had disease clearance (p<0.0001). In a further model, mice were engrafted with equal proportions of TRBC1-Jurkat and TRBC2-Jurkat cells. FACS analysis of bone marrow at 5 days following T-cell injection demonstrated specific eradication of TRBC1 and not TRBC2 tumour by anti-TRBC1 CAR (p<0.001).In summary, we have demonstrated a novel approach to investigation and targeting of T-cell malignancies by distinguishing between two possible TCR β-chain constant regions. Using CART-cells targeting TRBC1 we have demonstrated proof of concept for anti-TRBC immunotherapy. Unlike non-selective approaches targeting the entire T-cell population, TRBC targeting could eradicate a T-cell tumour while preserving sufficient normal T-cells to maintain cellular immunity. DisclosuresMaciocia:Autolus: Equity Ownership, Patents & Royalties: TRBC1 and 2 Targeting for the Diagnosis and Treatment of T-cell Malignancies. Philip:Autolus: Equity Ownership. Onuoha:Autolus: Employment, Equity Ownership. Pule:Amgen: Honoraria; Roche: Honoraria; UCL Business: Patents & Royalties; Autolus Ltd: Employment, Equity Ownership, Research Funding.

Real-World Use of Pomalidomide and Dexamethasone in Double Refractory Multiple Myeloma: A Multicentre UK Experience

Introduction. The outlook for myeloma patients who relapse after or become refractory to bortezomib and IMiDs is poor, with limited therapeutic options and a median survival (OS) of 9 months. In the phase 3 MM-003 study, pomalidomide plus low-dose dexamethasone resulted in a significant PFS (median 4 vs 1.9 months) and OS (median 13.1 vs 8.1 months) benefit, compared to high-dose dexamethasone. Information on real-world outcomes of pomalidomide therapy is limited. We carried out a retrospective analysis of patients receiving pomalidomide in the UK, to compare outcomes and tolerability with published clinical trial data, and focus on high risk subgroups.Methods. All patients treated with pomalidomide at 5 major UK centres between August 2013 and March 2016 were identified from chemotherapy records, and clinical data including toxicity and survival from patient records. Disease response and adverse FISH were defined as per IMWG. Survival was estimated using Kaplan-Meier, and correlations made using log-rank methods. Key subgroups: eGFR <45ml/min, adverse genetics, and older age were assessed.Results. A total of 85 patients were identified. Of these, 70 (82%) had measurable disease (IMWG criteria) and received ≥1 cycle so were included in response analyses. Baseline patient characteristics are reported in Table 1.96.5% of patients were refractory to one or more IMiDs, and 72.9% were refractory to both IMiDs and bortezomib. 92.9% were refractory to their last treatment. The median dose of pomalidomide was 4mg (2-4). Grade 3-4 non-haematological toxicities occurred in 42.4%: pneumonia (16.5%), neutropenic sepsis (8.2%), and acute kidney injury (7.1%), were most common. Grade 3-4 neutropenia occurred in 38% and thrombocytopenia in 24%. Seven patients died on treatment, 6 during the first cycle (2 PD and sepsis, 2 neutropenic sepsis, 1 PD and AKI, 2 pneumonia).In the 70 patients assessable for response, ORR was 52.9% (5.7% VGPR, 47.1% PR, 38.6% SD). Median duration of response (DoR) was 4 months. With median follow-up of 13 months, median PFS was 5 months (95%CI 3.6-6.4), and median OS 13 months (95%CI 10.8-15.2).Patients with renal failure (eGFR <45ml/min) had PFS and OS that were similar to those with eGFR ≥45ml/min ((HR=0.95, 95%CI 0.49-1.82, and HR=1.22, 0.59-2.53). Patients with adverse FISH (44%) had similar outcomes to those with standard FISH (ORR 45.8 vs 50%, median PFS 6 vs 5 months (HR=0.86, 95%CI 0.44-1.67, and median OS 10 vs 8 months, HR=1.223, 0.55-2.68). Patients aged >65yrs had similar outcomes to younger patients,(ORR 54.1 vs 51.5%, median PFS and OS comparable between groups). Rates of toxicity were also not influenced by renal impairment, adverse genetics, or older age.The most important predictors of PFS and OS were depth and durability of response. PFS was 6 months for patients achieving PR, 4 months for SD and 1 month for PD, while OS was 18 months in patients achieving PR, 13 months for SD and 3 months for PD. For patients with DoR >4 months, PFS was 11 months and OS 23 months. In contrast, in patients whose DoR was < 4 months or who did not respond, OS was 9 months.Conclusions. Our real-world data on the characteristics and outcomes of patients receiving pomalidomide for relapsed/refractory myeloma in the UK reflect results of published clinical trials. The ORR of 52.9% in our cohort is higher than in MM-003 and MM-010, but PFS (5 months) and OS (13 months) were remarkably similar. Rates of haematological toxicity and infections are low, confirming the good tolerability of pomalidomide in this patient group.Depth and sustainability of response were important predictors of survival: achievement of PR was associated with improved PFS and OS, while patients who achieved SD still derived a survival benefit. Patients who maintained a response for at least 4 months had an estimated survival of nearly 2 years. No difference in response, survival or tolerability was seen in key subgroups, including those with moderate renal impairment, adverse cytogenetics and older age. Our findings confirm the efficacy of pomalidomide in these heavily pre-treated patients and add to the evidence for the benefit of pomalidomide in high risk patient groups. [Display omitted] [Display omitted] DisclosuresMaciocia:Autolus: Equity Ownership, Patents & Royalties: TRBC1 and 2 Targeting for the Diagnosis and Treatment of T-cell Malignancies. Ramasamy:Celgene: Honoraria, Research Funding. Jenner:Novartis: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Other: Travel support; Amgen: Consultancy, Honoraria, Other: Travel support; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Other: Travel support, Research Funding. Schey:Celgene, Takeda: Honoraria; Celgene, Johnson & Johnson: Speakers Bureau; Celgene: Consultancy. Yong:Autolus Ltd: Equity Ownership, Patents & Royalties: APRIL based chimeric antigen receptor; Janssen: Research Funding.

Factors Influencing Outcomes of Relapse from Front-Line Autologous Stem Cell Transplant (ASCT) over a 14 Year Period: A Single Centre Experience

Background. Chemotherapy followed by ASCT is standard of care in fit transplant-eligible newly diagnosed patients with Multiple Myeloma (MM). Most patients, however, will relapse and require further treatment. With increasing choice of therapies at relapse, we need to understand the determinants of treatment outcomes for these patients, to aid management decisions and patient counselling.Methods. This was a retrospective analysis of sequential patients who relapsed from upfront ASCT carried out between 2000-2014. PFS1 was defined as time from ASCT to 1st progression or death; PFS2, time from ASCT to 2nd progression or death and 2nd PFS, time from start of salvage regimen to 2nd progression or death. Post relapse survival (PRS) was measured from progression date and overall survival (OS) from ASCT date. Disease response, and adverse FISH were assigned according to IMWG. Survival was estimated using Kaplan- Meier curves and correlative analysis by Cox regression models.Results. Of 474 patients undergoing ASCT (2000-2014), 277 relapsed with a median age of 58 years (range 29-70).The M:F ratio was 1.85:1. Isotypes identified were: IgG 57.0%, IgA 22.7%, light chain 15.9%. Median PFS1 from ASCT was 20 months (0.47-128.3). ORR pre-ASCT was 91.3% (sCR/CR 4.4%, VGPR 25.4%) and post ASCT was 95.3% (sCR/CR 14.5%, VGPR 52.2%). At relapse, median age was 60 years (30-73) and 36.5% of patients had ISS stage2-3 disease. For the 277 patients who relapsed, median OS from ASCT was 67 months (CI 57-73) and median PRS was 40 months (35-44). PFS1 had a strong influence on OS, HR 0.97 (95%CI: 0.96-0.97, p<0.001), and PRS HR 0.99 (0.98-0.996, p=0.004).Patients relapsing before 2008 (prior to bortezomib funding) had shorter OS compared to those relapsing thereafter: median 61 vs 69 months, HR 1.38 (1.01-1.87, p=0.04). Depth of response (CR/VGPR) pre and post-ASCT were associated with longer PFS1- HR 0.70 (0.54-0.92, p=0.01), and HR 0.68(0.51-0.89, p=0.005) respectively, but not OS or PRS.248 patients (89.5%) received systemic salvage therapy at relapse;106 patients (38.3%) experienced biochemical IMWG progression rather than clinical relapse, with median time to treatment of 5 months (2-64). Salvage regimens included: proteasome inhibitors(PIs) (64.5%), immunomodulatory agents (IMiDs, 29.8%, thalidomide-63.5%, lenalidomide-36.5%) and chemotherapy 5.2%; 26.6% of patients entered clinical trials and 13.7% underwent salvage ASCT. ORR was 70.4% (sCR/CR 10.9%, VGPR 31.6%). Median 2nd PFS was 17 months (16-20) and median PFS2 overall was 39 months (35-41). Achieving a deeper response to salvage treatment (CR/VGPR) was associated with a longer 2nd PFS (21 vs 17 months for PR, HR 0.65, 0.46-0.91, p=0.01), with a trend for PRS, HR 0.89(0.59-1.34, p=0.58) and OS, HR 0.77(0.51-1.17, p=0.22).Novel agents induced deeper responses, CR/VGPR with PI regimens 51.3%, with IMiDs 30%, and with chemotherapy 8%. Patients treated with PIs compared to all other systemic treatment regimens had a significantly longer OS of 80 vs 48 months, HR 0.60(0.43-0.85, p= 0.004). Patients entered into clinical trials (66) had deeper responses, ≥VGPR 61% compared to 31% in non-trial patients, and longer PRS, 64 vs 35 months, HR 0.54 (0.36-0.81, p= 0.003) and OS 90 vs 57 months, HR 0.50 (0.33-0.76, p=0.001).Risk factors at relapse influenced outcomes. Higher ISS was associated with shorter PRS, ISS 2/3 27 vs 50 months for ISS1, HR 2.52(1.74-3.66, p<0.0001) and OS, 46 vs 82 months, HR 2.42(1.67-3.50, p<0.0001). Presence of adverse FISH at relapse (54.1% of 133 patients) also predicted shorter PRS (restricted mean survival time 40 vs 72 months, p<0.001) and OS, 59 vs 97 months for standard FISH, HR 0.46 (0.28-0.73, p=0.0011). Adverse FISH at diagnosis (25.5% of 157) also predicted poorer outcomes.Conclusions. This real-world series shows that timing of relapse, period of relapse (pre-2008), ISS Stage, adverse FISH, and response to salvage regimen influence survival after relapse from frontline ASCT. Use of novel regimens, particularly PIs as salvage therapy post ASCT is associated with longer OS. Our data confirm the importance of entering patients into clinical trials. Multivariable linear regression analyses will be presented. Lastly, the inferior outcomes for patients with high-risk features highlights the need to develop different treatment strategies in this patient subgroup. DisclosuresMaciocia:Autolus: Equity Ownership, Patents & Royalties: TRBC1 and 2 Targeting for the Diagnosis and Treatment of T-cell Malignancies. Yong:Janssen: Research Funding; Autolus Ltd: Equity Ownership, Patents & Royalties: APRIL based chimeric antigen receptor.

Pegylated arginase I: a potential therapeutic approach in T-ALL

AbstractAdult patients with acute lymphoblastic T cell leukemia (T-ALL) have a very poor prognosis and few effective therapeutic options. Therefore, novel therapies that increase the efficacy of the treatments and that prolong T-ALL patient survival are needed. Malignant T cells require high concentrations of nutrients to sustain their increased rate of proliferation. In this study, we determined whether L-Arginine depletion by the pegylated form of the L-Arginine-metabolizing enzyme arginase I (peg-Arg I) impairs the proliferation of malignant T cells. Our results show that peg-Arg I depleted L-Arginine levels in vitro and in vivo. In addition, treatment of malignant T-cell lines with peg-Arg I significantly impaired their proliferation, which correlated with a decreased progression into the cell cycle, followed by the induction of apoptosis. Furthermore, peg-Arg I impaired the expression of cyclin D3, a fundamental protein in T-ALL proliferation, through a global arrest in protein synthesis. Injection of peg-Arg I plus chemotherapy agent Cytarabine prolonged survival in mice bearing T-ALL tumors. This antitumoral effect correlated with an inhibition of T-ALL proliferation in vivo, a decreased expression of cyclin D3, and T-ALL apoptosis. The results suggest the potential benefit of L-Arginine depletion by peg-Arg I in the treatment of T-cell malignancies.

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.

A Role for the Fas/FasL System in Modulating Genetic Susceptibility to T-Cell Lymphoblastic Lymphomas

The Fas/FasL system mediates induced apoptosis of immature thymocytes and peripheral T lymphocytes, but little is known about its implication in genetic susceptibility to T-cell malignancies. In this article, we report that the expression of FasL increases early in all mice after gamma-radiation treatments, maintaining such high levels for a long time in mice that resisted tumor induction. However, its expression is practically absent in T-cell lymphoblastic lymphomas. Interestingly, there exist significant differences in the level of expression between two mice strains exhibiting extremely distinct susceptibilities that can be attributed to promoter functional polymorphisms. In addition, several functional nucleotide changes in the coding sequences of both Fas and FasL genes significantly affect their biological activity. These results lead us to propose that germ-line functional polymorphisms affecting either the levels of expression or the biological activity of both Fas and FasL genes could be contributing to the genetic risk to develop T-cell lymphoblastic lymphomas and support the use of radiotherapy as an adequate procedure to choose in the treatment of T-cell malignancies.

Plasma and cerebrospinal fluid pharmacokinetics of nelarabine in nonhuman primates

Nelarabine is a water-soluble prodrug of the cytotoxic deoxyguanosine analog ara-G, to which it is rapidly converted in vivo by adenosine deaminase. Nelarabine has shown activity in the treatment of T-cell malignancies, especially T-cell acute lymphoblastic leukemia. Preliminary data suggested that nelarabine might penetrate into the CSF. We therefore studied the CSF penetration of nelarabine and ara-G in a nonhuman primate model that has been highly predictive of anticancer drug distribution in humans. Nelarabine (35 mg/kg, approximately 700 mg/m2) was administered over 1 h through a surgically implanted central venous catheter to four nonhuman primates. Blood (four animals) and ventricular CSF (three animals) samples were obtained at intervals for 24 h for determination of nelarabine concentrations, which were measured by HPLC-mass spectrometry. The nelarabine plasma AUC (median+/-s.d.) was 2,820+/-1,140 microM min and the ara-G plasma AUC was 20,000+/-8,100 microM min. The terminal half-life of nelarabine in plasma was 25+/-5.2 min and clearance was 42+/-61 ml/min/kg. The terminal half-life of ara-G in plasma was 182+/-45 min. In CSF the terminal half-life of nelarabine was 77+/-28 min and of ara-G was 232+/-79 min. The AUCcsf:AUCplasma was 29+/-11% for nelarabine and 23+/-12% for ara-G. The excellent CSF penetration of nelarabine and ara-G supports further study of the contribution of nelarabine to the prevention and treatment of CNS leukemia.

Nelarabine in the treatment of refractory T-cell malignant diseases

T-cell haematological malignancies are uncommon, difficult to treat and, with the exception of T-cell acute lymphoblastic leukaemia, often associated with a poor prognosis. Nelarabine (2-amino-9-β-d-arabinosyl-6-methoxy-9H-guanine), a synthesised guanosine nucleoside and water-soluble prodrug of ara-G (9-β-d-arabinofuranosylguanine), has recently been approved by the FDA for the treatment of relapsed/refractory T-cell acute lymphoblastic leukaemia and T-cell lymphoblastic lymphoma in adults and children. Similar to other nucleoside analogues, nelarabine acts by inhibiting DNA synthesis and inducing apoptosis in susceptible cells. Ara-G itself is a water-insoluble molecule, making its clinical use difficult. However, nelarabine is water soluble and rapidly converted to ara-G in vivo. Interestingly, it has been demonstrated that ara-GTP accumulates more readily in T-cells than in B-cells, and this discovery created interest in the development of nelarabine for the treatment of T-cell malignancies. The results of early-phase clinical trials evaluating the use of nelarabine in adults and children with refractory T-cell malignancies have been promising. This article describes the development, pharmacology, toxicity and clinical activity of nelarabine, as well as discusses its potential role in the treatment of T-cell haematological malignancies.

The role of pentostatin in the treatment of T-cell malignancies: analysis of response rate in 145 patients according to disease subtype.

To assess the results of treatment with the purine analog 2'deoxycoformycin (pentostatin [DCF]) in patients with postthymic T-cell malignancies. One hundred forty-five patients with postthymic T-cell malignancies were given DCF intravenously at 4 mg/m2/wk for the first 4 weeks and then every 2 weeks until maximal response; the last 30 patients received weekly injections until maximal response. The overall response rate was 32% (complete responses [CRs] plus partial responses [PRs]), with marked variation according to diagnosis. The best responses occurred in patients with Sézary syndrome (62%) and T-prolymphocytic leukemia (T-PLL) (45%), with CRs in three of 16 Sézary syndrome and five of 55 T-PLL patients. In contrast, no responses (NRs) were documented in 13 patients with other types of cutaneous T-cell lymphoma, including five mycosis fungoides. Two of five patients with large granular lymphocyte (LGL) leukemia had a CR and two of four with Sézary cell leukaemia had a PR. A low response rate was observed in 27 patients with peripheral T-non-Hodgkin's lymphoma (T-NHL) (19%) and in 25 with adult T-cell leukemia/lymphoma (ATLL) (12%). The latter included two CRs and one PR. Toxicity was low and DCF was generally well tolerated. No significant differences were observed when results were analyzed according to previous treatment. Disease subtype was the most important factor to influence results. We conclude that DCF is effective as a single agent in T-PLL, Sézary syndrome, and LGL leukemia, but has low activity in other T-cell disorders.

Human T-Cell Antigens Defined by Monoclonal Antibodies. Absence of T65 on Committed Myeloid and Erythroid Progenitors

The complement-dependent cytotoxicity of monoclonal T-cell antibody (T101) for normal and abnormal hemopoietic progenitors was assessed. T101 demonstrated toxicity for normal T-colony-forming cells from peripheral blood and bone marrow. Cytotoxicity was absent for normal peripheral blood and bone marrow granulocytes/macrophage (CFU-C) and erythroid (BFU-E) progenitors. The antibody was also not toxic for peripheral blood blast progenitors from patients with acute myelogenous leukemia (AML). These studies indicate the absence of the antigen defined by T101 (T65) from normal progenitor cells and from blast progenitors in patients with AML. T101 may be used in the treatment of T-cell malignancies and in the prevention of graft-versus-host disease (GVHD) without damage to normal progenitor cells.

Human T-cell antigens defined by monoclonal antibodies. Absence of T65 on committed myeloid and erythroid progenitors

The complement-dependent cytotoxicity of monoclonal T-cell antibody (T101) for normal and abnormal hemopoietic progenitors was assessed. T101 demonstrated toxicity for normal T-colony-forming cells from peripheral blood and bone marrow. Cytotoxicity was absent for normal peripheral blood and bone marrow granulocytes/macrophage (CFU-C) and erythroid (BFU-E) progenitors. The antibody was also not toxic for peripheral blood blast progenitors from patients with acute myelogenous leukemia (AML). These studies indicate the absence of the antigen defined by T101 (T65) from normal progenitor cells and from blast progenitors in patients with AML. T101 may be used in the treatment of T-cell malignancies and in the prevention of graft-versus-host disease (GVHD) without damage to normal progenitor cells.