T-cell Prolymphocytic Leukemia Patients Research Articles

Preclinical Evaluation of T-Cell Prolymphocytic Leukemia Demonstrates Heterogeneous BCL2-Family Dependency That May be Effectively Targeted with Small Molecule Inhibitors

T-cell prolymphocytic leukemia (T-PLL) is a rare, aggressive, mature T-cell leukemia with very few treatment options and adverse prognosis. There are currently no approved therapies for patients with relapsed T-PLL, where the median OS is less than 6 months. There are limited reports suggesting clinical activity of the BCL2 inhibitor venetoclax in patients with T-PLL. We aimed to characterize the dependencies of T-PLL on members of the BCL2-family of antiapoptotic proteins using BH3 profiling, a functional assay to assess the propensity of a cell to undergo apoptosis (priming) and the relative dependence of a cell on different antiapoptotic proteins. We then sought to experimentally exploit these dependencies with targeted therapies alone, and in combination, designed to inhibit the antiapoptotic proteins towards a therapeutic goal. Cell lines of mature T cell lymphomas/leukemias (TCL/L) including SUPT11 (T-cell leukemia with rearranged TCL1) (n=10) and bone marrow and peripheral blood samples from untreated patients with T-PLL (n=7) were analyzed by BH3 profiling. We also used a relapsed/refractory T-PLL patient sample that were able to engraft and expand in a PDX model. Finally, scRNA/ATAC seq has also been performed in a set of naïve-treated T-PLL patients. In contrast to TCL/L that demonstrated heterogeneity on BCL2 family member dependency, T-PLL samples were primed and consistently exhibited dependency on BCL2/BCL-xL and MCL1. Integration of scRNA/ATAC seq confirmed high expression of BCL2 and MCL1 in T-PLL cells from four patients supporting the premise that BCL2 and MCL1 could potentially be targeted for therapeutic benefit. Therefore, SUPT11 cells (used as a model of T-PLL) were exposed to venetoclax (25 and 50nM; BCL-2inh), fadraciclib (25 and 50nM; CDK2/9inh - indirect inhibitor of MCL-1 as it decreases mRNAs with high decay rates including MCL1 and MYC) or a combination of venetoclax and fadraciclib. We demonstrate that exposure to fadraciclib caused a rapid decline in the levels of phosphorylation on Serine 2 of RNA polymerase II C-terminal domain, as well as decline in the levels of MCL1 within 4 hours and completely depleted these proteins by 8-12 h of exposure. We also show that there was a synergistic increase both in mitochondrial dysfunction as measured by cytochrome C release by 18h and in cell death in cells exposed to the combination at 24h. These results suggest that combining venetoclax and fadraciclib might represent a potential therapeutic approach for T-PLL. In conclusion, preclinical evaluation of a T-PLL cell line and primary patient samples demonstrate BCL2-family dependency that can be effectively targeted with small molecule inhibitors of BCL2 and CDK2/9. In vivo studies in PDX models of T-PLL are underway to form the basis for clinical trials to study these combinations.

Computational gene expression analysis reveals distinct molecular subgroups of T-cell prolymphocytic leukemia.

T-cell prolymphocytic leukemia (T-PLL) is a rare blood cancer with poor prognosis. Overexpression of the proto-oncogene TCL1A and missense mutations of the tumor suppressor ATM are putative main drivers of T-PLL development, but so far only little is known about the existence of T-PLL gene expression subtypes. We performed an in-depth computational reanalysis of 68 gene expression profiles of one of the largest currently existing T-PLL patient cohorts. Hierarchical clustering combined with bootstrapping revealed three robust T-PLL gene expression subgroups. Additional comparative analyses revealed similarities and differences of these subgroups at the level of individual genes, signaling and metabolic pathways, and associated gene regulatory networks. Differences were mainly reflected at the transcriptomic level, whereas gene copy number profiles of the three subgroups were much more similar to each other, except for few characteristic differences like duplications of parts of the chromosomes 7, 8, 14, and 22. At the network level, most of the 41 predicted potential major regulators showed subgroup-specific expression levels that differed at least in comparison to one other subgroup. Functional annotations suggest that these regulators contribute to differences between the subgroups by altering processes like immune responses, angiogenesis, cellular respiration, cell proliferation, apoptosis, or migration. Most of these regulators are known from other cancers and several of them have been reported in relation to leukemia (e.g. AHSP, CXCL8, CXCR2, ELANE, FFAR2, G0S2, GIMAP2, IL1RN, LCN2, MBTD1, PPP1R15A). The existence of the three revealed T-PLL subgroups was further validated by a classification of T-PLL patients from two other smaller cohorts. Overall, our study contributes to an improved stratification of T-PLL and the observed subgroup-specific molecular characteristics could help to develop urgently needed targeted treatment strategies.

P638: THE RISK OF SECOND PRIMARY MALIGNANCIES AND CAUSE-SPECIFIC MORTALITY AMONG PATIENTS WITH T-CELL PROLYMPHOCYTIC LEUKEMIA IN THE UNITED STATES: A POPULATION-BASED STUDY.

Background: T cell prolymphocytic leukemia (T-PLL) is a rare lymphoid malignancy, compromising 2% of mature lymphocytic leukemias. The T-PLL follows an aggressive clinical course with median survival of 7.5 months with conventional chemotherpay. In the era of targeted therapy with anti-CD52 antibody for patients with T-PLL, there is data lacking on the spectrum of second primary malignancies (SPMs) and cause-specific mortality. Aims: In this current study we aim to identify the risk of SPM and cause specific mortality in patients with T-PLL in the era of targeted therapies with anti-CD52 antibodies using a national registry from the United States. Methods: The incidence of SPMs and cause-specific mortality among two-month survivors of T-PLL, was estimated using the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER)-13 registries. We included patients from 1992-2018 with ICD-O-3 code 9834/3 from the registry. We estimated the risk of SPMs using standardized incidence ratios (SIRs) and cause-specific mortality by standardized mortality ratios (SMRs) and absolute excess risk (AER)/10,000 population. Results: We included a total of 314 patients with T-PLL in this study. The median age at diagnosis was 68.5 years (range 1-85 years). The median follow-up duration was 12 months (range 0-196 months). A total of 13 (4%) patients developed 14 SPMs at the last follow-up. The SPM risk for the cohort was significantly elevated (SIR 2.54, 95% confidence interval [CI] 1.39-4.27) compared with general population. The median latency period for SPM development was 28 months (range 8-108 months). The SIR was significant among males (SIR 2.96, 95% CI 1.42-5.44), but not in females (SIR 1.88, 95% CI 0.51-4.82). The SIR according to age groups was significant in patients with age < 60 years (SIR 3.84, 95% CI 1.25-8.97), but not in age > 60 years (SIR 2.14, 95% CI 0.98-4.06). Specific SPMs with the highest risk included nasopharyngeal cancers (SIR 200.87, 95% CI 5.09-1,119.20) and multiple myeloma (SIR 33.39, 95% CI 6.89-97.58). At last follow-up, 155 (49%) patients had died, of which 89% were due to malignant neoplasms. There was statistically significant risk of mortality due to all malignant cancers combined (SMR 58.35, 95% CI 49.03-68.94), largely due to mortality from lymphocytic leukemia (SMR 2587, 95% CI 2021-3264, AER 1757), non-Hodgkin lymphoma (SMR 100, 95% CI 45.88-190.45, AER 220), stomach and duodenal ulcers (SMR 73.74, 95% CI 1.87-410.84, AER 24.43), uterine cancer (SMR 66.55, 95% CI 1.68-370.78, AER 24.39), and pneumonia and influenza (SMR 11.88, 95% CI 2.45-34.71, AER 68.04). The risk of death from lymphocytic leukemia was highest within the first year of diagnosis of T-PLL and continued to decline slowly thereafter, although it remained statistically significantly elevated more than other causes of death (SMR 1yr=3405, AER 2666; SMR 1-5 yrs=2623, AER 1715; SMR 5-10 yrs=1015, AER 516). Summary/Conclusion: Our study reveals that the risk of developing SPMs remains elevated in patients with T-PLL compared to the general population. Additionally, men are at an increased risk for SPMs compared to women. Despite therapeutic advances in T-PLL, hematologic neoplasms (including lymphocytic leukemia) have remained the leading cause of death in the last three decades. Further studies are needed to better define the healthcare needs of T-PLL patients beyond initial treatment to reduce the burden of mortality from T-PLL and other SPMs.

Advanced Pathogenetic Concepts in T-Cell Prolymphocytic Leukemia and Their Translational Impact

T-cell prolymphocytic leukemia (T-PLL) is the most common mature T-cell leukemia. It is a typically aggressively growing and chemotherapy-resistant malignancy with a poor prognosis. T-PLL cells resemble activated, post-thymic T-lymphocytes with memory-type effector functions. Constitutive transcriptional activation of genes of the T-cell leukemia 1 (TCL1) family based on genomic inversions/translocations is recognized as a key event in T-PLL’s pathogenesis. TCL1’s multiple effector pathways include the enhancement of T-cell receptor (TCR) signals. New molecular dependencies around responses to DNA damage, including repair and apoptosis regulation, as well as alterations of cytokine and non-TCR activation signaling were identified as perturbed hallmark pathways within the past years. We currently witness these vulnerabilities to be interrogated in first pre-clinical concepts and initial clinical testing in relapsed/refractory T-PLL patients. We summarize here the current knowledge on the molecular understanding of T-PLL’s pathobiology and critically assess the true translational progress around this to help appraisal by caregivers and patients. Overall, the contemporary concepts on T-PLL’s pathobiology are condensed in a comprehensive mechanistic disease model and promising interventional strategies derived from it are highlighted.

ANTI-CD52 TREATMENT EXPERIENCE IN A T-CELL PROLYMPHOCYTIC LEUKEMIA PATIENT:CASE REPORT

T-cell prolymphocytic leukemia (T-PLL) is a rare and highly aggressive T cell neoplasm with rapidly progressing clinical course. T-PLL accounts for 2% of mature lymphocytic leukemia in adults. Median overall survival with modern therapy is reported one to three years. Here we report a T-PLL patient with peritoneum involvement and progressive ascite despite anti-CD52 treatment. A 65-year-old man with diabetes mellitus was admitted to hospital due to fatigue for a few weeks. Laboratory workup revealed that white blood cell count 469 × 103/µl (90% lymphocytes), haemoglobin of 11.4 g/dl, platelets of 104 × 103/µl. Medium sized atypical lymphoid cells with partial chromatin condensation and a visible nucleolus were observed on blood smear. On physical examination, palpable inguinal lymph nodes, splenomegaly 3 cm below the rib margin and a palpable lesion on the helix of left ear were noticed. Punch biyopsy of skin lesion was reported as a mature and immature T cell infiltration which are CD3 and CD10 positive and Tdt, CD34, CD20, CD99 negative. Flow cytometric study of peripheral blood sample was revealed that T-Chronic Lymphocytic Leukemia (T-CLL). FMC protocol (fludarabine, mitoxantrone, and cyclophosphamide ) was initiated and followed by intravenous alemtuzumab at a dose of 3 mg on day 1, 10 mg on day 2 and 30 mg on day 3. However after two months of anti-CD52 treatment, his general situation dete­riorated and pleural effusion and abdominal distension developed due to massive ascites. Small, mature lymphocytic cell infiltration was shown in ascites fluid on cytological examination. He died after six months of diagnosis. T-PLL is a very aggressive disease with a median survival of less than 1 year. Not all patients diagnosed with T-PLL require treatment immediately.Currently, IV alemtuzumab (anti-CD52) is the accepted best avaliable treatment with very high response rates when given as first-line treatment. However, treatment is notcurative and a minority of T-PLL patients experience long-term disease-free survival.

TCL-445: Case of T-Cell Prolymphocytic Leukemia Successfully Treated with Fludarabine, Mitoxantrone, and Cyclophosphamide

Context T-cell prolymphocytic leukemia (T-PLL) is an extremely rare mature T-cell neoplasm associated with an aggressive clinical course, poor response to conventional chemotherapy, and a dismal prognosis. Current therapeutic strategies conventionally employ the anti-CD52 antibody alemtuzumab as the most active agent. Alemtuzumab, originally marketed for use in cancer (Mabcampath®), is currently licensed and formulated for the treatment of relapsing multiple sclerosis (Lemtrada®), causing a lack of drug availability, with potentially grave consequences for T-PLL patients’ prognosis. Design We present the case of a 68-year-old male patient diagnosed with T-PLL in December 2020, who underwent four cycles of fludarabine 25 mg/m2, mitoxantrone 8 mg/m2, and cyclophosphamide 200 mg/m2, and achieved complete remission (CR), according to the criteria established by the T-PLL International Study Group. Results A 68-year-old Caucasian male presented to our center with fatigue and weakness for several months and a history of persistent, progressive lymphocytosis for the past 18 months. A computed tomography scan revealed bilateral cervical, axillary, and intra-abdominal lymph nodes, measuring approximately 3 cm each; an enlarged spleen of 180 mm in length; and mild hepatomegaly, measuring 177 mm on the midclavicular line. Laboratory studies revealed leukocytosis (282 × 109/L) and an absolute lymphocyte count of 255 × 109/L, with no anemia or thrombocytopenia. The metabolic profile was normal, except for an elevated lactate dehydrogenase of 974 U/L. The bone marrow aspirate showed 86%–88% polymorphic lymphoid cells, while the flow cytometry analysis indicated T cells positive for CD2 and surface and cytoplasmic CD3, CD5, and CD7, 70% of which were CD4+CD8+, and 30% CD4+. The core biopsy revealed a markedly hypercellular marrow (80%), with a lymphoid infiltrate made up of small/medium-sized cells, some with cerebriform nuclei, some with prominent nucleoli, with weakly positive immunohistochemistry staining for CD52. Conclusions The patient presented in this case study was treated with conventional chemotherapy alone and achieved CR of T-PLL, maintaining the treatment response to date (3 months after completion of the therapy). Despite this, alemtuzumab remains a crucial element in the arsenal of treatment for T-PLL, and its lack of availability poses a serious challenge for clinicians.

TCL-361: Bendamustine as Front-Line Therapy in T-Cell Prolymphocytic Leukemia: A Monocentric Experience

Introduction T-cell prolymphocytic leukemia (T-PLL) is a rare T-cell-neoplasm that is characterized by uncontrolled proliferation of mature T-cell lymphocytes with a very poor prognosis. Nowadays, alemtuzumab as a single agent is the best available option for both treatment-naive and relapsed/refractory patients; however, its efficacy is hampered by various adverse events (AEs) such as infusion-associated reactions, autoimmune AEs, and opportunistic infections. Objective We conducted a monocentric, retrospective study to evaluate the safety and efficacy of bendamustine, which is a bifunctional mechlorethamine derivative with alkylating and antimetabolite activities, as first-line therapy in patients unfit for alemtuzumab. Patients and Methods We collected clinical and biological data of 7 T-PLL patients treated with bendamustine between 2014 and 2020 in our institution. Four out of seven (57%) were males, the median age at diagnosis was 73 years (65–83 years). The median time from diagnosis to treatment was 15 months. Bendamustine was administered intravenously (90 mg/m2 on days one and two, every four weeks) for up to six cycles. Results Overall response rate was 57%, 3 patients achieved complete response (43%), and one partial response (14%). One patient experienced stable disease, and two patients progressed during treatment. Five patients (71%) experienced a relapse. Median overall survival (OS) was 63.7 months (19–108); median OS for responding patients was 187 months versus 24 months for non-responding patients (p=0.093). Median progression-free survival (PFS) was 12 months (11–13). Three patients received second-line therapy: one patient was treated with gemcitabine; the others received a second bendamustine course. Two patients received a third-line therapy with combination chemotherapy: COMP (prednisone, cyclophosphamide, vincristine, myocettm) and CVP (cyclophosphamide, vincristine, prednisone). Two patients experienced infusion-associated reactions. Four patients experienced hematological toxicities: one thrombocytopenia G3, 3 neutropenia G3 requiring G-CSF administration. Four patients received co-trimoxazole prophylaxis, one received acyclovir prophylaxis. One patient experienced herpetic retinitis. Premature termination ( Conclusions Our data are consistent with scientific literature. This treatment is feasible and safe, with an acceptable toxicity profile. Although alemtuzumab remains the standard of care of this rare disease, bendamustine might be a valid option either for unfit patients or for undeferrable disease.

CDK9 Inhibition with LDC526 Is an Effective Treatment for T-Cell Prolymphocytic Leukemia (T-PLL) in Vitro

▪IntroductionT-cell prolymphocytic leukemia (T-PLL) is a rare leukemia with an aggressive disease course, characterized by chemotherapy resistance and a median overall survival of less than two years. Apart from defects in DNA damage response genes like ATM and genes of JAK/STAT signaling, overexpression of MYC, often caused by gain of chromosomal material, is frequently observed in T-PLL. Intravenous application of the anti-CD52 antibody Alemtuzumab has been demonstrated to improve progression-free survival and is currently considered the standard of care. In younger patients remissions can be consolidated by allogeneic stem cell transplantation, which results in long-term remission in a small subgroup of patients. The prognosis in the majority of patients relapsing from their disease is dismal and thus novel treatment options are urgently needed. Cyclin-dependent kinase 9 (CDK9), a serine/ threonine kinase which is ubiquitously expressed, is the catalytic unit of the positive transcription elongation factor (P-TEFb). In the presence of cyclin T, p-TEFb stimulates transcription elongation by phosphorylation of the carboxy-terminal domain (CTD) of RNA polymerase II (RNA Pol II). CDK9 inhibition by LDC526, a specific CDK9 inhibitor, leads to reduced phosphorylation of CTD-Ser2, Ser5 and Ser7 of RNA Pol II and subsequently to the downregulation of MYC and MCL-1.Methods</spanCD3+CD4+ tumor cells from cryopreserved peripheral blood samples of 11 T-PLL patients were enriched to a purity of >95% by fluorescence-activated cell sorting (FACS) or magnetic activated cell separation (MACS). RNA and DNA were isolated using the RNeasy Mini Kit® or the QIAamp DNA blood midi kit® (Qiagen, Hilden, Germany), respectively. To determine IC50 values, we performed cell viability assays for T-PLL cells of 11 patients treated with LDC526 and a panel of reference compounds compared to DMSO controls (CellTiter-Glo Luminescent Cell Viability Assay; Promega, Fitchburg, WI, USA). Gene expression profiling was performed in primary T-PLL cells treated with the CDK9 inhibitor LDC526 in a concentration of 10µM compared to DMSO (n=3) on Clariom S Pico Assays (Affymetrix, Santa Clara, CA, USA) and analyzed by gene set enrichment analysis (GSEA) and GeneTrail analysis. Gene expression measurement was performed with quantitative real-time PCR (qPCR) for MYC (Taqman, Thermo Fisher Scientific, Waltham, MA, USA). Protein expression was analyzed for pCTD Ser2, Ser5 and Ser7, MYC, p-STAT3 and MCL-1 by Western Blot (n=4) after LDC526-treatment in three different concentrations (10, 30 and 100 µM).ResultsLDC526 inhibited T-PLL cell survival in vitro in a dose-dependent manner. The median IC50 was 1.7 µM (range: 0.9 -3.5) which compared favourably to a panel of reference compounds including fludarabine, clofarabine, methotrexate, cytarabine and ruxolitinib (median IC50 values 6.4, 6.2, 29.9, 8.3, and 29.2, respectively). Similar experiments with BAY1143572, a structurally closely related CDK9 inhibitor, which is currently investigated in phase I studies of acute myeloid leukemia, revealed an even lower median IC50 of 0.9 µM (range: 0.5 - 1.7). Of note, the purine analogues fludarabine and clofarabine were only active in some of the patients tested, whereas both CDK9 inhibitors showed activity in all samples analyzed.Gene expression profiles of LDC526 treated T-PLL cells compared to DMSO controls revealed an enrichment of genes in gene sets associated with interferon and TNFA signatures, MYC targets as well as JAK/STAT genes, which were subsequently confirmed by qPCR experiments. At the protein level LDC526 dose-dependently reduced phosphorylation of CTD-Ser2, Ser7 and to a lesser extent of Ser5 compared to DMSO controls resulting in efficient down-regulation of MYC, MCL-1 and p-STAT3.ConclusionsOur experiments identify CDK9 as a novel therapeutic target in T-PLL which can be efficiently inhibited by LDC526 and BAY1143572 at clinically meaningful concentrations. CDK9 inhibition resulted in both reduced T-PLL cell survival and down-regulation of MYC and JAK/STAT signaling, which have a key role in the molecular pathogenesis of T-PLL. DisclosuresDürig:Lead Discovery Center: Research Funding.

Development of HDAC Inhibitors Exhibiting Therapeutic Potential in T-Cell Prolymphocytic Leukemia.

Epigenetic targeting has emerged as an efficacious therapy for hematological cancers. The rare and incurable T-cell prolymphocytic leukemia (T-PLL) is known for its aggressive clinical course. Current epigenetic agents such as histone deacetylase (HDAC) inhibitors are increasingly used for targeted therapy. Through a structure–activity relationship (SAR) study, we developed an HDAC6 inhibitor KT-531, which exhibited higher potency in T-PLL compared to other hematological cancers. KT-531 displayed strong HDAC6 inhibitory potency and selectivity, on-target biological activity, and a safe therapeutic window in nontransformed cell lines. In primary T-PLL patient cells, where HDAC6 was found to be overexpressed, KT-531 exhibited strong biological responses, and safety in healthy donor samples. Notably, combination studies in T-PLL patient samples demonstrated KT-531 synergizes with approved cancer drugs, bendamustine, idasanutlin, and venetoclax. Our work suggests HDAC inhibition in T-PLL could afford sufficient therapeutic windows to achieve durable remission either as stand-alone or in combination with targeted drugs.

Epigenetic alteration contributes to the transcriptional reprogramming in T-cell prolymphocytic leukemia

T cell prolymphocytic leukemia (T-PLL) is a rare disease with aggressive clinical course. Cytogenetic analysis, whole-exome and whole-genome sequencing have identified primary structural alterations in T-PLL, including inversion, translocation and copy number variation. Recurrent somatic mutations were also identified in genes encoding chromatin regulators and those in the JAK-STAT signaling pathway. Epigenetic alterations are the hallmark of many cancers. However, genome-wide epigenomic profiles have not been reported in T-PLL, limiting the mechanistic study of its carcinogenesis. We hypothesize epigenetic mechanisms also play a key role in T-PLL pathogenesis. To systematically test this hypothesis, we generated genome-wide maps of regulatory regions using H3K4me3 and H3K27ac ChIP-seq, as well as RNA-seq data in both T-PLL patients and healthy individuals. We found that genes down-regulated in T-PLL are mainly associated with defense response, immune system or adaptive immune response, while up-regulated genes are enriched in developmental process, as well as WNT signaling pathway with crucial roles in cell fate decision. In particular, our analysis revealed a global alteration of regulatory landscape in T-PLL, with differential peaks highly enriched for binding motifs of immune related transcription factors, supporting the epigenetic regulation of oncogenes and genes involved in DNA damage response and T-cell activation. Together, our work reveals a causal role of epigenetic dysregulation in T-PLL.

Cutaneous Presentation of T-Cell Prolymphocytic Leukemia Mimicking Dermatomyositis

T-cell prolymphocytic leukemia (TPLL) is a rare form of leukemia by T lymphocytes at a post-thymic intermediate stage of development with an α/β immunophenotype. Facial involvement is common in TPLL and displays significant heterogeneity of the lesions' description and location. TPLL also contains a wide array of histology findings, cell cytology, and molecular studies. Here, we describe a TPLL patient who presented with an ill-defined erythematous patch involving the right axilla progressing to the left axilla, upper back, and face that resembled dermatomyositis. The diagnosis of TPLL was established using flow cytometry of bone marrow and peripheral blood, and histopathology of the involved skin. Dermatologists should be aware of these unique features.

Mutations in PIGA cause a CD52-/GPI-anchor-deficient phenotype complicating alemtuzumab treatment in T-cell prolymphocytic leukemia.

Infusional alemtuzumab followed by consolidating allogeneic hematopoietic stem cell transplantation in eligible patients is considered a standard of care in T-cell prolymphocytic leukemia (T-PLL). Antibody selection against CD52 has been associated with the development of CD52-negative leukemic T cells at time of relapse. Clinical implications and molecular mechanisms underlying this phenotypic switch are unknown. We performed flow cytometry and real-time-PCR for CD52-expression and next generation sequencing for PIGA mutational analyses. We identified loss of CD52 expression after alemtuzumab treatment in two of 21 T-PLL patients resulting from loss of GPI-anchor expression caused by inactivating mutations of the PIGA gene. One patient with relapsed T-PLL exhibited a single PIGA mutation, causing a CD52-negative escape variant of the initial leukemic cell clone, preventing alemtuzumab-retreatment. The second patient with continued complete remission after alemtuzumab treatment harbored three different PIGA mutations that affected either the non-neoplastic T cell or the mononuclear cell compartment and resulted in symptomatic paroxysmal nocturnal hemoglobinuria. Next generation sequencing of T-PLL cells collected before the initiation of treatment revealed PIGA wild-type sequence reads in all 16 patients with samples available for testing. These data indicate that PIGA mutations were acquired during or after completion of alemtuzumab treatment.

Characterizing the Anti-Apoptotic Dependencies of T-Cell Prolymphocytic Leukemia Identifies HDAC and JAK/STAT Pathway Inhibitors As Promising Combination Partners to Augment Bcl-2 Targeted Killing By Venetoclax

Characterizing the Anti-Apoptotic Dependencies of T-Cell Prolymphocytic Leukemia Identifies HDAC and JAK/STAT Pathway Inhibitors As Promising Combination Partners to Augment Bcl-2 Targeted Killing By Venetoclax

No Improvement in Survival for T-PLL Patients over the Last Two Decades

BACKGROUND: T-cell prolymphocytic leukemia (T-PLL) is a rare, aggressive, post thymic lymphoid malignancy, with an incidence of approximately 0.1/100,000 people. T-PLL accounts for ~2% of all mature lymphocytic leukaemias in adults &amp;gt;30 years. Median overall survival (OS) ~20 months and long term remissions are infrequent. Intravenous alemtuzumab, a monoclonal antibody directed against CD52 remains the most effective treatment in T-PLL. At the Royal Marsden Hospital (RMH) we have been using alemtuzumab for T-PLL since the early 1990s. We describe our experience over the last 3 decades. METHODS: We included 174 T-PLL patients that were diagnosed or treated at RMH between 1989-2019. Immunophenotyping data was available through our hematological malignancy diagnostic service (HMDS) from 1998 onwards. Kaplan-Meier analysis was used for OS and disease free interval (DFI) RESULTS: There were 174 patients in total. Mean age at diagnosis was 61 years old (range 32-88) and M: F ratio was ~2:1 (113:61). 90 patients had reliable information on complete blood count (CBC) at diagnosis with median white blood cell count of 74 x 109/L (range 10-918), median hemoglobin 126 g/L (range 59-175) and median platelet count 116 x 109/L (range 7-513). Sufficient immunophenotyping data was available for analysis in 135/174 patients. The results showed predictably high expression of CD2, CD3, CD5, CD7, CD52 and TCRαβ. CD25 was positive in 67/135 (50%) of cases which is higher than the 18-35% seen in the current literature. CD4+/CD8- cases comprised 83/135 (61%) with CD4-/CD8+ 19/135 (14%), CD4+/CD8+ 32/135 (23%) and CD4-/CD8- 2/135 (2%). These results are summarized in table 1. Karyotyping/FISH (fluorescent in-situ hybridization) records showed a clonal result in 84 patients and of these 65/84 (77%) had an aberration of chromosome 14. These comprised 48/65 with inv(14), 6/65 t(14;14), 2/65 t(X;14), 1/65 TCL1 gene rearrangement by FISH and 8/65 with TRA/TRD involvement by FISH. Other frequent abnormalities seen were i(8)(q10) in 31/84 (39%) and complex karyotypic abnormality in 40/84 (48%). Lower frequency abnormalities seen were monosomy 11 in 8/84 (9%), monosomy 12 in 8/84 (9%), trisomy 8 in 6/84 (7%), 17p loss in 5/84 (6%) and mononsomy 13 in 4/84 (5%). Alemtuzumab was used in 116 patients, 69/116 (59%) receiving it as frontline treatment and 47/116 (41%) as salvage therapy. In 50/116 (43%) alemtuzumab was used as single agent, the remaining 66/116 (57%) receiving combination therapy, mostly pentostatin. Mean time from diagnosis to receiving alemtuzumab was 6.8 months (range 0-53 months). Overall response rate (ORR) to alemtuzumab was 94/116 (81%) with complete remission (CR) 69/116 (59%), partial remission (PR) 25/116 (22%) and no response (NR) 20/116 (17%). Alemtuzumab produced better response rates when used as frontline therapy. Table 2 summarizes these results and OS and DFI are shown in figures B and C. Allogeneic stem cell transplant (allo-SCT) was performed in 34 patients. Median OS post allo-SCT was 22 months and median DFI 31 months. Relapse rate post allo-SCT was 47%, non-relapse mortality 38% and transplant related mortality 29%. Figures D and E show OS and DFI post allo-SCT. Although relapse rates are high post allo-SCT there is a small cohort of patients who are achieving long term remission. We analysed OS by decade of diagnosis covering 3 decades 1990-1999, 2000-2009 and 2010-2019. The median OS for the whole cohort was 20.6 months with median OS of 21 months, 23 months and 19 months for each decade respectively. Results are shown in figure A. There was no statistically significant difference between the curves by log-rank analysis. DISCUSSION: Immunophenotyping results were similar to previous published data on T-PLL except for an increase in CD25 expression at 50%. Our data shows that outcomes in T-PLL have remained unchanged since the first decade of alemtuzumab usage, with no improvement in OS in the last 20 years. Despite improvements in diagnostic techniques and supportive care median OS is static at approximately 20 months. These results highlight the need for novel therapies in T-PLL. Given the rarity of T-PLL, international, multi-center, randomised trials are needed to improve outcomes. Disclosures Cross: Royal Marsden Cancer Charity: Other: MD Residency, Research Funding. Iyengar:Abbvie: Honoraria; Janssen: Honoraria. Dearden:Janssen: Honoraria; Genentech: Honoraria; Abbvie: Honoraria; Sanofi: Honoraria.

New lessons learned in T-PLL: results from a prospective phase-II trial with fludarabine–mitoxantrone–cyclophosphamide–alemtuzumab induction followed by alemtuzumab maintenance

Clinical trials in T-cell prolymphocytic leukemia (T-PLL) are scarce. Based on a precursor study testing fludarabine, mitoxantrone, and cyclophosphamide followed by alemtuzumab (FMC-A), we aimed to improve this regimen by upfront combining subcutaneous (s.c.) alemtuzumab with FMC for four cycles followed by an alemtuzumab-maintenance (FMCA + A). This prospective multicenter phase-II trial assessed response, survival, and toxicity of that regimen administered to pretreated (n = 4) and treatment-naïve (n = 12) T-PLL patients. The best overall response rate after FMCA was 68.8% (n = 11) including five CRs (31.3%) and six PRs (37.5%). Six patients entered the alemtuzumab-maintenance. Median overall and progression-free survival was 16.7 and 11.2 months, respectively. Hematologic toxicities were the most frequent grade 3/4 side effects. A reduced incidence of CMV-reactivations was attributed to the prophylactic administration of valganciclovir. Overall, FMCA + A did not improve the efficacy of the FMC-A-regimen or of single i.v. alemtuzumab. It suggests that a chemotherapy backbone prevents efficient alemtuzumab dosing and confirms that intravenous alemtuzumab is to be preferred over its s.c. route in T-PLL.Trial registration: ClinicalTrials.gov identifier: NCT01186640.

Patient-Customized Drug Combination Prediction and Testing for T-cell Prolymphocytic Leukemia Patients

The molecular pathways that drive cancer progression and treatment resistance are highly redundant and variable between individual patients with the same cancer type. To tackle this complex rewiring of pathway cross-talk, personalized combination treatments targeting multiple cancer growth and survival pathways are required. Here we implemented a computational-experimental drug combination prediction and testing (DCPT) platform for efficient in silico prioritization and ex vivo testing in patient-derived samples to identify customized synergistic combinations for individual cancer patients. DCPT used drug-target interaction networks to traverse the massive combinatorial search spaces among 218 compounds (a total of 23,653 pairwise combinations) and identified cancer-selective synergies by using differential single-compound sensitivity profiles between patient cells and healthy controls, hence reducing the likelihood of toxic combination effects. A polypharmacology-based machine learning modeling and network visualization made use of baseline genomic and molecular profiles to guide patient-specific combination testing and clinical translation phases. Using T-cell prolymphocytic leukemia (T-PLL) as a first case study, we show how the DCPT platform successfully predicted distinct synergistic combinations for each of the three T-PLL patients, each presenting with different resistance patterns and synergy mechanisms. In total, 10 of 24 (42%) of selective combination predictions were experimentally confirmed to show synergy in patient-derived samples ex vivo The identified selective synergies among approved drugs, including tacrolimus and temsirolimus combined with BCL-2 inhibitor venetoclax, may offer novel drug repurposing opportunities for treating T-PLL.Significance: An integrated use of functional drug screening combined with genomic and molecular profiling enables patient-customized prediction and testing of drug combination synergies for T-PLL patients. Cancer Res; 78(9); 2407-18. ©2018 AACR.

Discovery of novel drug sensitivities in T-PLL by high-throughput ex vivo drug testing and mutation profiling.

T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive neoplasm of mature T-cells with an urgent need for rationally designed therapies to address its notoriously chemo-refractory behavior. The median survival of T-PLL patients is <2 years and clinical trials are difficult to execute. Here we systematically explored the diversity of drug responses in T-PLL patient samples using an ex vivo drug sensitivity and resistance testing platform and correlated the findings with somatic mutations and gene expression profiles. Intriguingly, all T-PLL samples were sensitive to the cyclin-dependent kinase inhibitor SNS-032, which overcame stromal-cell-mediated protection and elicited robust p53-activation and apoptosis. Across all patients, the most effective classes of compounds were histone deacetylase, phosphoinositide-3 kinase/AKT/mammalian target of rapamycin, heat-shock protein 90 and BH3-family protein inhibitors as well as p53 activators, indicating previously unexplored, novel targeted approaches for treating T-PLL. Although Janus-activated kinase-signal transducer and activator of transcription factor (JAK-STAT) pathway mutations were common in T-PLL (71% of patients), JAK-STAT inhibitor responses were not directly linked to those or other T-PLL-specific lesions. Overall, we found that genetic markers do not readily translate into novel effective therapeutic vulnerabilities. In conclusion, novel classes of compounds with high efficacy in T-PLL were discovered with the comprehensive ex vivo drug screening platform warranting further studies of synergisms and clinical testing.

Prognostic significance of cytogenetic abnormalities in T-cell prolymphocytic leukemia.

T-cell prolymphocytic leukemia (T-PLL) is an aggressive mature T-cell neoplasm. The most common cytogenetic abnormality associated with T-PLL is inv(14)(q11.2q32) involving TCL1, but other abnormalities also have been reported. In this study, we correlated cytogenetic abnormalities with clinical outcome in 97 T-PLL patients, including 66 men and 31 women with a median age of 63 years (range, 34-81). Twenty-seven patients had a normal karyotype (NK), one had two chromosomal aberrations, and 69 had a complex karyotype (CK). Patients with a CK had poorer overall survival (OS) than patients with a NK (P = .0016). In the CK group, the most common aberrations involved 14q (n = 45) and 8q (n = 38). Additional deletions of chromosomes 17p, 11q, 6q, 12p, 13q were observed frequently. No individual cytogenetic abnormality impacted OS. Patients with ≥5 aberrations had an OS of 11 months versus 22 months in patients with <5 aberrations (P = 0.0132). Fluorescence in situ hybridization for TCL1 successfully performed in 27 cases showed rearrangement in 8/10 (80%) NK versus 16/17 (94%) CK cases. OS of patients with TCL1 rearrangement and/or 14q aberrations was not significantly different from patients without TCL1 rearrangement and 14q aberrations (P = .3467). Patients with refractory disease showed worse OS in both the NK and CK groups (P = .0014 and P < .0001, respectively), compared with patients who achieved remission but then relapsed. Stem cell transplantation did not appear to improve OS regardless of karyotype complexity. In conclusion, patients with T-PLL often have a CK which is a poor prognostic factor, particularly in patients with ≥5 cytogenetic aberrations.

Novel Mutations in NOTCH and Altered Wnt/β-Catenin Pathway Indicate a Role of Embryonic Signals in the Pathogenesis of T-Cell Prolymphocytic Leukemia

Background:Recurrent mutations in ATM, JAK1/3 and STAT5B genes have been identified in T-cell prolymphocytic leukemia (T-PLL), a mature T cell leukemia with poor survival. However, much remains to be understood regarding the dysregulated pathways involved in the pathogenesis of this aggressive disease. Here, we integrated the analyses of whole exome sequencing (WES) and transcriptomes of a cohort of 12 T-PLL samples to gain further insights into molecular mechanisms of this malignancy.Methods: Leukemic cells were isolated from peripheral blood or bone marrow samples of T-PLL patients. Tumor DNA and RNA, and germline DNA were extracted from purified leukemic T cells and bone marrow derived stromal cells, respectively. WES (n=12) and transcriptome analysis (n=10) were performed and data analyzed with published standard methods (Robinson et al. 2010 and DePristo et al. 2011)Results: 7 paired tumor and germline DNA and 5 tumor-only DNA samples were used for WES analysis. Mutations in ATM and TET2 were detected in 4 (33%) and 1 (8%) patients, respectively. JAK3 (p.M511I, p.Q501H and p.Q503H) or STAT5B (2 p.T628S and 1 p.N642H) mutations each occurred in 3 (25%) cases and were mutually exclusive, consistent with prior reports. Importantly, we found several novel mutations in genes with regulatory roles in the NOTCH signaling pathway. Specifically, 2 somatic mutations p.A3V and p.A3S in NOTCH2 and 2 other mutations (p.S244L and p.A1414V) in NOTCH4 were identified in 4 (33%) patients. One mutation was in the EGF- like and another one in the NODP domain critical for NOTCH-mediated cellular differentiation. Two (16.7%) novel missense mutations (p.G174D and p.V836I) were found in MAML2. Three missense mutations (2 p.S583N and 1 p.R190H) occurred in MAML1. Both MAML2 and MAML1 are essential cofactors of the NOTCH signaling pathway. In addition, a somatic mutation in the NOTCH signal regulator DTX2 (p.G268D) was detected. Altogether 7 (58.3%) patients harbored mutations in genes with a regulatory role in the NOTCH pathway. Among the epigenetic modifiers, we found deletions and point mutations in KDM6B and KDM6A in 4 (30%) patients including 2 codon deletions in KDM6B (p.X751Val) and 1 missense mutation each in KDM6B (p.R1016Q) and KDM6A (p.V510G). KDM6A and KDM6B are histone H3 lysine 27 demethylases known to be involved in regulation of DNA repair and play an important role in embryonic differentiation.Transcriptome analyses of 10 T-PLL cases versus normal CD3+ T cells from 5 healthy donors revealed 706 up-regulated and 655 down-regulated genes. Consistent with prior data, TCL1A and TCL1B were significantly overexpressed (23.7 and 13.1 fold, respectively). Using Ingenuity Pathway Analysis, we found PTEN Signaling, glutamate receptor, and axonal guidance signaling to be among the top 3 upregulated pathways. The top upstream regulators implicated for the up-regulated signals were FGF, Wnt/β-catenin and TNF. The top 3 down-regulated pathways were granulocyte adhesion and diapedesis, IL-17A in psoriasis and IL-10 signaling. The top regulators for the down-regulated pathways were LPS, TNF and IFNg. Wnt/β-catenin and Human embryonic stem cell pluripotency signaling were among the top 20 up-regulated pathways. Many genes involved in the regulation of Wnt signal pathway were included in the above pathways, including Wnt ligands (Wnt9A, Wnt4), transmembrane receptors (CDH1, LRP5, FZD6, FZD7, SMO), cytoplasmic factor (AXIN2), and nuclear factors (MYC, SOX12, SOX8, SOX18, CCND1).Summary: Our study identified recurrent mutations in the NOTCH signaling pathway as well as dysregulated embryonic developmental pathway, e.g. Wnt/NOTCH as newly implicated molecular mechanisms in T-PLL pathogenesis for further functional studies. Additionally, novel (KDM6A and KDM6B) and known mutations (ATM, TET2) in chromatin regulatory genes underscore the importance of epigenetic dysregulation in the tumorigenesis of T-PLL. DisclosuresParikh:Pharmacyclics: Honoraria, Research Funding. Mustjoki:Ariad: Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Ding:Merck: Research Funding.

Identification of Targeted Therapies for Rare Adult Mature T-Cell Leukemia Using Functional Ex Vivo Screening of Primary Patient Samples

Introduction: T-cell prolymphocytic leukemia (T-PLL) is an aggressive lymphoproliferative disorder and accounts for ~2% of cases of mature lymphocytic leukemia in adults. The sparsity of patients with this disease poses a challenge to effectively develop targeted treatments. Recent studies suggest chromosome 14 abnormalities are most common in T-PLL (75% of patients), resulting in overexpression of the proto-oncogene TCL1 and activation of protein kinase B (Stengel, Anna, et al. 2016). Presently alemtuzumab is the only effective, available therapeutic option, with almost all patients relapsing within months after completion of therapy. With the aim of identifying new therapeutics for T-PLL, we assessed the sensitivity of primary patient samples to various targeted agents using an ex vivo functional screening platform.Methods: We have previously screened over 1000 primary specimens from patients with various hematologic malignancies against a panel of 143 single-agent small-molecular inhibitors, including kinase inhibitors, bromodomain inhibitors, BHM mimetics, proteasome inhibitors, IDH1/2 inhibitors, and several other drug classes. Primary patient specimens were cultured in the presence of each drug in a 7-point dose series. Sensitivity was assessed by a tetrazolium-based viability assay on day 3. An IC50 value was then calculated for each inhibitor and compared with the median of the IC50 values for the full patient sample cohort screened to date. Inhibitors for which the IC50 value was < 20% of the cohort median were considered effective. T-PLL primary patient samples were assessed for sensitivities using this historical drug sensitivity data and we ranked all drugs by their IC50.Results: Our database identified 5 adults (3 male, 2 female) with T-PLL who had analyzable data obtained within 1 month of diagnosis (Table 1). Median age was 65 years (range, 49-88 years). At diagnosis, the median white blood cell count was 56.2 K/cu mm (16-243.65 K/cu mm) and all patients had detectable 14q11 abnormalities and TCR gene rearrangements. All patients were treated with standard first-line therapy with IV alemtuzumab (30 mg 3x/week) for an average of 11.6 weeks (8.59 -14.75 weeks). Their median progression free survival (PFS) was 9.3 months (5.4-20 months) and duration of response was 5.6 months (2.9 -16.8 months). Three patients received second-line therapy after alemtuzumab failure with a PFS of 6.9 months (1.1- 9.8 months). Three patients went on to an allogeneic stem cell transplants with PFS of 6.7 months (4.5-7.7 months). The median overall survival was 19.1 months (2.07-11.6 months).Our ex vivo assay showed that 9 (6.2%) of 143 small-molecular inhibitors were considered effective (20% of median IC50) in the majority of subjects. This included 6 FDA approved tyrosine kinase inhibitors (axitinib, dasatinib, sunitinib, sorafenib, pazopanib, and ponatinib), midostaurin, an NF-kB activation inhibitor, and CSF1R inhibitors. Sensitivity of T-PLL patients to these drugs is shown in the log plot (Figure 1). Patient 4 had no strong targets identified. Dasatinib showed the most efficacy in 4 of the 5 patients, with an average IC50 of 0.003 ± 0.0007 µm, followed by CSFIRJ inhibitor with an average IC50 of 0.02 ± 0.015 µm.Conclusions: Our functional ex vivo screen of primary patient samples allowed us to evaluate the effectiveness of several FDA approved and investigational therapeutic agents targeting multiple oncogenic pathways in T-PLL, a rare disease with limited existing therapies. Our approach indicates that several existing inhibitors may be effective in this aggressive leukemia and can be tested in prospective clinical trials. [Display omitted] [Display omitted] DisclosuresDruker:Agios: Honoraria; Ambit BioSciences: Consultancy; ARIAD: Patents & Royalties, Research Funding; Array: Patents & Royalties; AstraZeneca: Consultancy; Blueprint Medicines: Consultancy, Equity Ownership, Other: travel, accommodations, expenses ; BMS: Research Funding; CTI: Equity Ownership; Curis: Patents & Royalties; Cylene: Consultancy, Equity Ownership; D3 Oncology Solutions: Consultancy; Gilead Sciences: Consultancy, Other: travel, accommodations, expenses ; Lorus: Consultancy, Equity Ownership; MolecularMD: Consultancy, Equity Ownership, Patents & Royalties; Novartis: Research Funding; Oncotide Pharmaceuticals: Research Funding; Pfizer: Patents & Royalties; Roche: Consultancy.