T-cell Lymphoma Model Research Articles

TP63 Fusions Drive Enhancer Rewiring, Lymphomagenesis, and Dependence on EZH2

Recurrent chromosomal rearrangements are a hallmark of hematologic malignancies and play critical roles in pathogenesis. The TP53 analog TP63 is rearranged in 5-10% of diverse subtypes of both aggressive T- and B-cell lymphomas, which is highly unique among chromosomal translocations. Specifically, TP63 rearrangements were found in 5-10% of ALK-negative anaplastic large cell lymphoma (ALK- ALCL), peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) and primary cutaneous ALCL, 7% of mycosis fungoides with large cell transformation (MF-LCT), and 1% of diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL). Patients with TP63-rearranged lymphomas have dismal outcomes, with 5-year overall survival rates between 0-17%, depending on cohorts. This contrasts with rearrangements of DUSP22, which are also observed in ALK- ALCLs and confer a good prognosis. The function and mechanisms of TP63 rearrangements and TP63 fusion proteins in tumorigenesis are poorly understood. As a result, attempts to treat these patients to date have been largely empiric. Thus, there is an urgent need to understand how TP63 fusions contribute to tumorigenesis and to translate the findings into novel therapeutic options for these patients. Here, we demonstrated that TP63 fusions are essential for the propagation of T-cell lymphomas (TCLs). Knockdown of TP63 fusions with specific shRNAs in TCL cell lines harboring TP63 rearrangements suppressed both cell growth in vitro and tumor growth in vivo. Retroviral expression of TBL1XR1-TP63, the most common TP63 fusion, conferred cytokine independence in Ba/F3 cells, consistent with its role as an oncogene. To investigate the role of TP63 fusions in T- and B-cell development and lymphomagenesis, we engineered a CAG-Loxp-Stop-Loxp-TBL1XR1-TP63 conditional knock-in mouse model and crossed with hCD2-Cre mice, which results in expression beginning during early lymphoid development. Transgenic mice had both cytokine and transcriptional evidence of immune activation as well as T cell repertoire narrowing, consistent with clonal selection. As observed in patients, transgenic mice developed multiple subtypes of both T- and B-cell lymphoma that mimicked ALCL, PTCL-NOS and MYC-expressing DLBCL. To define the effects and mechanisms of TP63 fusions within T cells, we performed CRISPR screening, transcriptomic, epigenomic, and proteomic analyses. We also performed a domain-focused CRISPR-Cas9 knockout scan using 452 sgRNAs tiling the entire coding regions of TBL1XR1 and TP63 to clarify essential oncogenic domains within TBL1XR1-TP63. Our data showed that domains within both the N-terminal TBL1XR1 and C-terminal TP63 portions contribute to the function of this fusion. We found that the N-terminal component of TP63 fusions (TBL1XR1, FOXK2, etc.) interacts with components of the NCOR/SMRT complex. At the same time, the C-terminal portion of TP63 fusions (which recapitulates the deltaNp63 isoform expressed in some carcinomas) interacts with the enhancer modifier KMT2D and its complex members. TBL1XR1-TP63 binds to a novel distal enhancer to drive MYC expression, and thus upregulates the expression of EZH2, which encodes the histone H3K27 methylase. Knockdown of the TP63 fusion in TCL cell lines led to complete loss of H3K27me3. Finally, we assessed whether EZH2 is a vulnerability of TP63-rearranged lymphomas. We found that knockdown of EZH2 in TP63-rearranged lines significantly impaired cell growth, as did treatment with the EZH2 inhibitor tazemetostat and the EZH2 and 1 dual inhibitor valemetostat. Valemetostat, which is now being tested in patients with lymphoma, was highly effective in three different in vivo models of TP63-rearranged TCL. Together, our results identify the TP63 fusion as a highly unique oncogenic driver in lymphomagenesis capable of recruiting multiple epigenetic modifier complexes and inducing a targetable dependence on EZH2.

Effective and Safe Immune Checkpoint Blockade Induces Complete Responses in Murine PTCL Model of ALCL

Anaplastic large cell lymphoma (ALCL) is a rare T-cell non-Hodgkin lymphoma. In the majority of cases the disease is driven by a chromosomal translocation t(2;5)(p23;35) leading to the fusion of the anaplastic lymphoma kinase (ALK) gene with the nucleophosmin gene (NPM), constitutively activating ALK kinase. In the last decade immunotherapy turned out to be a real game-changer in cancer treatment, especially in the field of solid tumors. Regarding T-cell lymphomas (TCL), the significance of immune checkpoint inhibition is still highly debated. The outcomes in preclinical models as well as clinical trials are ranging from response to hyperprogression. Consequently, to provide a better understanding of the role and underlying mechanisms of targeting immune checkpoint axes, preclinical models of TCL are urgently needed to identify patients that benefit from immunotherapy as well as potential biomarkers. To examine disease biology and therapy effects of ALCL in vivo, we use a syngeneic retroviral bone marrow transplantation mouse model of ALK+ ALCL that closely resembles the disease in humans. In order to study the effect of blocking the PD-1/PD-L1-axis in ALCL in vivo, serial transplantations of lymphoma cells from a murine thymus were performed. We further investigated both spontaneous and immunotherapy-induced immune responses and characterized the interaction of innate and adaptive immune master players with flow cytometry, cytokine analysis, histology and transcriptome analysis. In our mouse model of ALK+ ALCL we confirmed the upregulation of PD-L1 on ALK+ lymphoma cells in vivo. Immune checkpoint inhibition of PD-L1 in vivo leads to high complete response rates, prolonged survival and significantly reduced lymphoma burden of treated animals. Flow cytometry analysis revealed that PD-L1 blockade reverses Treg-mediated immunosuppression and causes augmented circulation of CD8+ effector T-lymphocytes. Treatment with depletion antibodies of lymphocyte subpopulations unveils CD4+ T-cells and NK-cells but not CD8+ T-cells as master players of checkpoint-mediated immune response to ALK+ ALCL. Accordingly, we identified exhausted CD4+ T-cells in non-responders to checkpoint inhibition underlining the central role of CD4+ T-cells in ALCL immune surveillance and response. These results are contributing to a broader understanding of the immune surveillance and response in ALCL, with the outmost goal of better identifying patients that benefit from immunotherapy.

Antagonism of inhibitors of apoptosis proteins reveals a novel, immune response-based therapeutic approach for T-cell lymphoma

Tolinapant (ASTX660) is a potent, nonpeptidomimetic antagonist of cellular inhibitor of apoptosis proteins 1 and 2 (cIAP1/2) and X-linked IAP, which is currently being evaluated in a phase 2 study in T-cell lymphoma (TCL) patients. Tolinapant has demonstrated evidence of single-agent clinical activity in relapsed/refractory peripheral TCL and cutaneous TCL. To investigate the mechanism of action underlying the single-agent activity observed in the clinic, we have used a comprehensive translational approach integrating in vitro and in vivo models of TCL confirmed by data from human tumor biopsies. Here, we show that tolinapant acts as an efficacious immunomodulatory molecule capable of inducing complete tumor regression in a syngeneic model of TCL exclusively in the presence of an intact immune system. These findings were confirmed in samples from our ongoing clinical study showing that tolinapant treatment can induce changes in gene expression and cytokine profile consistent with immune modulation. Mechanistically, we show that tolinapant can activate both the adaptive and the innate arms of the immune system through the induction of immunogenic forms of cell death. In summary, we describe a novel role for IAP antagonists as immunomodulatory molecules capable of promoting a robust antitumor immune response in TCL.

Targeting JAK/STAT Signaling Antagonizes Resistance to Oncolytic Reovirus Therapy Driven by Prior Infection with HTLV-1 in Models of T-Cell Lymphoma.

Human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that infects at least 10 million people worldwide and is associated with the development of T-cell lymphoma (TCL). The treatment of TCL remains challenging and new treatment options are urgently needed. With the goal of developing a novel therapeutic approach for TCL, we investigated the activity of the clinical formulation of oncolytic reovirus (Reolysin, Pelareorep) in TCL models. Our studies revealed that HTLV-1-negative TCL cells were highly sensitive to Reolysin-induced cell death, but HTLV-1-positive TCL cells were resistant. Consistent with these data, reovirus displayed significant viral accumulation in HTLV-1-negative cells, but failed to efficiently replicate in HTLV-1-positive cells. Transcriptome analyses of HTLV-1-positive vs. negative cells revealed a significant increase in genes associated with retroviral infection including interleukin-13 and signal transducer and activator of transcription 5 (STAT5). To investigate the relationship between HTLV-1 status and sensitivity to Reolysin, we infected HTLV-1-negative cells with HTLV-1. The presence of HTLV-1 resulted in significantly decreased sensitivity to Reolysin. Treatment with the JAK inhibitor ruxolitinib suppressed STAT5 phosphorylation and expression of the key anti-viral response protein MX1 and enhanced the anti-TCL activity of Reolysin in both HTLV-1-positive and negative cells. Our data demonstrate that the inhibition of the JAK/STAT pathway can be used as a novel approach to antagonize the resistance of HTLV-1-positive cells to oncolytic virus therapy.

Targeted inhibition of CD47-SIRPα requires Fc-FcγR interactions to maximize activity in T-cell lymphomas

AbstractAntibodies that bind CD47 on tumor cells and prevent interaction with SIRPα on phagocytes are active against multiple cancer types including T-cell lymphoma (TCL). Here we demonstrate that surface CD47 is heterogeneously expressed across primary TCLs, whereas major histocompatibility complex (MHC) class I, which can also suppress phagocytosis, is ubiquitous. Multiple monoclonal antibodies (mAbs) that block CD47-SIRPα interaction promoted phagocytosis of TCL cells, which was enhanced by cotreatment with antibodies targeting MHC class I. Expression levels of surface CD47 and genes that modulate CD47 pyroglutamation did not correlate with the extent of phagocytosis induced by CD47 blockade in TCL lines. In vivo treatment of multiple human TCL patient-derived xenografts or an immunocompetent murine TCL model with a short course of anti-CD47 mAb markedly reduced lymphoma burden and extended survival. Depletion of macrophages reduced efficacy in vivo, whereas depletion of neutrophils had no effect. F(ab′)2-only fragments of anti-CD47 antibodies failed to induce phagocytosis by human macrophages, indicating a requirement for Fc-Fcγ receptor interactions. In contrast, F(ab′)2-only fragments increased phagocytosis by murine macrophages independent of SLAMF7-Mac-1 interaction. Full-length anti-CD47 mAbs also induced phagocytosis by Fcγ receptor-deficient murine macrophages. An immunoglobulin G1 anti-CD47 mAb induced phagocytosis and natural killer cell-mediated cytotoxicity of TCL cells that was augmented by cotreatment with mogamulizumab, an anti-CCR4 mAb, or a mAb blocking MHC class I. These studies help explain the disparate activity of monotherapy with agents that block CD47 in murine models compared with patients. They also have direct translational implications for the deployment of anti-CD47 mAbs alone or in combination.

Biomarker-driven strategy for MCL1 inhibition in T-cell lymphomas

AbstractThere is a pressing need for more effective therapies to treat patients with T-cell lymphomas (TCLs), including first-line approaches that increase the response rate to cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP) chemotherapy. We characterized the mitochondrial apoptosis pathway in cell lines and patient-derived xenograft (PDX) models of TCL and assessed the in vitro efficacy of BH3 mimetics, including the BCL2 inhibitor venetoclax, the BCL2/BCL-xL inhibitor navitoclax, and the novel MCL1 inhibitor AZD5991. The abundance of antiapoptotic BCL2 family members based on immunoblotting or RNA transcript levels correlated poorly with the activity of BH3 mimetics. In contrast, the functional approach BH3 profiling reliably predicted sensitivity to BH3 mimetics in vitro and in vivo. We used BH3 profiling to select TCL PDX that were dependent on MCL1. Mice xenografted with these PDX and treated with AZD5991 had markedly improved survival. The combination of AZD5991 and CHOP achieved synergy based on survival improvement beyond a mathematical “sum of benefits” model. Thus, MCL1 inhibition is a promising strategy as both a single agent and in combination with chemotherapy for patients with TCL and functional dependence on MCL1.

Targeting Epigenetic Operations with HDAC Inhibitor and Hypomethylating Drugs in Combination Exhibit Synergy in Preclinical and Clinical Experiences in Drug Resistant T-Cell Lymphoma (TCL): A Translational Focus on Doublet Development

Introduction: The TCL are chemotherapy resistant neoplasms associated with a poor outcome. Recently, mutations in a number of important genes controlling epigenetic functions have been reported, including mutations in TET2, IDH1/2 and DNMT3. As a class, HDAC inhibitors have exhibited activity leading to regulatory approval only in TCL. Collectively, these observations suggest that combinations of hypomethylating agents (HoMe) and HDAC inhibitor (HDACi) should be explored as a potential new backbone in TCL. Methods : In vitro and in vivo models of TCL were used to evaluate the preclinical merits of combining HoMe and HDACi using standard cytotoxicity assays (CellTiter Glo and Anexin V staining) and well established murine NOG models. Gene expression array (GEP) using Affymatrix were performed to identify unique gene sets perturbed by the combination. Patterns of methylation and DNA fragmentation were determined using the LINE-1 Assay and APO alert DNA fragmentation assay . A Phase 1 study in patients with relapsed/refractory (R/R) lymphoma has enrolled all cohorts. Detailed PK and PD studies were performed. Results: In vitro , all 4 HDACi inhibitors (romidepsin [R]; vorinostat [V]; belinostat [B]; panobinostat [P]) exhibited marked class synergy with HoMe agents, including decitabine and azacytidine. Cell Titer Glo and Anexin V staining confirmed that the combination was potently synergistic as determined by the relative risk ratio (RRR). The synergy was more dependent on the concentration of the HDAC inhibitor, and was most pronounced with romidepsin versus other HDACi. In vivo , the combination of belinostat and decitabine produced a marked inhibition of TCL growth that was highly statistically significant compared to the single arm treated and untreated controls. GEP and methylation profiling revealed differentially expressed genes and modulated pathways for each of the single treatment conditions and combination. 944 unique genes were modulated by the combination supporting the idea of 9molecular synergism9. There was no methylation affect seen in the HDACi treated cells. Quantitation of DNA methylation and fragmentation suggested that concentrations of AZA from > 1 nM to Conclusions: A laboratory to bench translational initiative focused on identifying novel doublet combinations in TCL has confirmed that targeting epigenetic operations in TCL is effective in both the preclinical and clinical setting. Present efforts are directed towards accruing the Phase 2 component of the study in patients with PTCL, and completing all PK and PD studies from the Phase 1. We believe this combination could form the basis of a new backbone in TCL. Disclosures O9Connor: Seattle Genetics: Consultancy; Novartis: Consultancy, Honoraria; Bristol-Myers Squibb Company: Consultancy; Celgene: Consultancy, Research Funding; Takeda Millennium: Consultancy, Honoraria, Research Funding; Spectrum Pharmaceuticals: Consultancy, Honoraria, Research Funding; Mundipharma: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria; Acetylon Pharmaceuticals, INC: Consultancy. Off Label Use: Oral Azacitadine is not approved for lymphoid malignancies. Romidepsin is not approved for B-NHL and HL.. Deng: TG Therapeutics, Inc.: Honoraria, Research Funding; Seattle Genetics: Research Funding. Sawas: Seattle Genetics: Research Funding. Colbourn: Benitec Biopharma: Equity Ownership; PDL Biopharma: Equity Ownership; Merk: Equity Ownership; Eli Lilly: Equity Ownership; Celgene: Equity Ownership; Biogen Idecc: Equity Ownership; Novartis: Equity Ownership; Seattle Genetics: Equity Ownership. Neylon: Seattle Genetics: Speakers Bureau; Celgene: Speakers Bureau; Genentech: Speakers Bureau; Gilead: Speakers Bureau. Amengual: Acetylon Pharmaceuticals, INC: Consultancy, Research Funding.

Aurora A Kinase Inhibition Selectively Synergizes with Histone Deacetylase Inhibitor through Cytokinesis Failure in T-cell Lymphoma.

Aurora A kinase (AAK) is expressed exclusively during mitosis, and plays a critical role in centrosome duplication and spindle formation. Alisertib is a highly selective AAK inhibitor that has demonstrated marked clinical activity of alisertib across a spectrum of lymphomas, though particularly in patients with T-cell lymphoma (TCL). We sought to compare and contrast the activity of alisertib in preclinical models of B-cell lymphoma (BCL) and TCL, and identify combinations worthy of clinical study. High-throughput screening of pralatrexate, the proteasome inhibitor (ixazomib), and the histone deacetylase (HDAC) inhibitor (romidepsin) revealed that only romidepsin synergized with alisertib, and only in models of TCL. We discovered that the mechanism of synergy between AAK inhibitors and HDAC inhibitors appears to be mediated through cytokinesis failure. A high-throughput screening approach was used to identify drugs that were potentially synergistic in combination with alisertib. Live-cell imaging was used to explore the mechanistic basis for the drug: drug interaction between alisertib and romidepsin. An in vivo xenograft TCL model was used to confirm in vitro results. In vitro, alisertib exhibited concentration-dependent cytotoxicity in BCL and TCL cell lines. Alisertib was synergistic with romidepsin in a T-cell-specific fashion that was confirmed in vivo. Live-cell imaging demonstrated that the combination treatment resulted in profound cytokinesis failure. These data strongly suggest that the combination of alisertib and romidepsin is highly synergistic in TCL through modulation of cytokinesis and merits clinical development.

The combination of hypomethylating agents and histone deacetylase inhibitors produce marked synergy in preclinical models of T-cell lymphoma.

T-cell lymphomas (TCL) are aggressive lymphomas usually treated with CHOP (cyclophsophamide, doxorubicin, vincristine, prednisolone)-like regimens upfront. Recent data suggest that TCL are driven by epigenetic defects, potentially rendering them sensitive to epigenetic therapies. We explored the therapeutic merits of a combined epigenetic platform using histone deacetylase inhibitors (HDACIs) and DNA methyltransferase inhibitors (DNMT) in invitro and invivo models of TCL. The 50% inhibitory concentration (IC50 ) values revealed romidepsin was the most potent HDACI, with an IC50 in the low nanomolar range. The combination with a hypomethylating agent produced synergy across all cell lines, which was confirmed in cytotoxicity and apoptosis assays. An invivo xenograft study demonstrated inhibition of tumour growth in the combination cohort compared to the single agent. Gene expression array and global methylation profiling revealed differentially expressed genes and modulated pathways for each of the single treatment conditions and the combination. Most of the effects induced by the single agent treatment were maintained in the combination group. In total, 944 unique genes were modulated by the combination treatment, supporting the hypothesis of molecular synergism. These data suggest combinations of hypomethylating agents and HDACIs are synergistic in models of TCL, which is supported at the molecular level.

Preclinical pharmacologic evaluation of pralatrexate and romidepsin confirms potent synergy of the combination in a murine model of human T-cell lymphoma.

T-cell lymphomas (TCL) are aggressive diseases, which carry a poor prognosis. The emergence of new drugs for TCL has created a need to survey these agents in a rapid and reproducible fashion, to prioritize combinations which should be prioritized for clinical study. Mouse models of TCL that can be used for screening novel agents and their combinations are lacking. Developments in noninvasive imaging modalities, such as surface bioluminescence (SBL) and three-dimensional ultrasound (3D-US), are challenging conventional approaches in xenograft modeling relying on caliper measurements. The recent approval of pralatrexate and romidepsin creates an obvious combination that could produce meaningful activity in TCL, which is yet to be studied in combination. High-throughput screening and multimodality imaging approach of SBL and 3D-US in a xenograft NOG mouse model of TCL were used to explore the in vitro and in vivo activity of pralatrexate and romidepsin in combination. Corresponding mass spectrometry-based pharmacokinetic and immunohistochemistry-based pharmacodynamic analyses of xenograft tumors were performed to better understand a mechanistic basis for the drug:drug interaction. In vitro, pralatrexate and romidepsin exhibited concentration-dependent synergism in combination against a panel of TCL cell lines. In a NOG murine model of TCL, the combination of pralatrexate and romidepsin exhibited enhanced efficacy compared with either drug alone across a spectrum of tumors using complementary imaging modalities, such as SBL and 3D-US. Collectively, these data strongly suggest that the combination of pralatrexate and romidepsin merits clinical study in patients with TCLs.

The Combination Of Hypomethylating Agents and Histone Deacetylase Inhibitors(HDACi) Are Synergistically Cytotoxic and Reverse The Malignant Phenotype In Preclinical Models Of T-Cell Lymphoma

Both HDAC inhibitors (HDACIs) and DNA methyltransferase inhibitors (DNMTIs) are known to influence global expression patterns in hematologic malignancies. Little is known about the combination of these two drug classes in lymphoid malignancies. HDACIs have marked single agent activity in the T- cell lymphomas (TCL), although the mechanism of action is not well defined. DNMTIs affect cytosine methylation of genomic DNA and have activity mainly restricted to the myeloid derived hematologic malignancies. The single agent efficacy and synergistic interaction of a panel of HDACIs (panobinostat, belinostat, romidepsin and vorinostat) and DNMTIs (decitabine (DEC), 5-azacytadine (5-AZA)) was evaluated in models of TCL. The molecular basis for the synergistic effect of HDACIs and DNMTIs was evaluated by gene expression profiling (GEP) and CpG methylation CTCL.Single agent concentration and time effect relationships were generated for 2 CTCL (HH, H9) and 2 T-ALL (P12, PF382) cell lines. Romidepsin and belinostat were the most potent HDACIs with the mean 48 hour IC50 of 8.8 nM (range 1.7-2.7 nM) and 85 nM (range 36-136 nM), respectively. Cell viability was not affected by treatment with DEC or 5-AZA at 24 and 48 hours at concentrations as high as 20 μM. Reduction in viability was first demonstrated after 72 hours of exposure to DEC, with the mean IC50 of 14.8 μM (range 0.4 μM- >20uM). Simultaneous exposure of combinations of DEC plus romidepsin or DEC plus belinostat at their IC10, IC20, and IC50 produced marked synergy in all TCL derived cell lines. Simultaneous exposure of DEC plus romidepsin demonstrated the deepest synergy at 72 hours with synergy coefficients in the range of 0.3. Cells treated with the combination of DEC plus romidepsin also demonstrated significant induction of apoptosis as evaluated by annexinV/propridium iodide via FACS analysis and an increase in acetylated histone 3 by immunoblot.The in vivo activity of the combination of DEC plus belinostat was investigated in a xenograft model of CTCL using HH, the most resistant TCL derived cell line. Mice were treated with DEC 1.5 mg/kg (day 29, 33, 35, 37, 39, 41, 43) and/or belinostat 100 mg/kg (day 29-day 47). The combination mouse cohort demonstrated statistically significant tumor growth delay compared to DEC alone (p=0.002) and belinostat alone (p=0.001).The interaction of DEC and romidepsin was analyzed by GEP and methylation array. Interestingly, the baseline malignant phenotype seen in the CTCL cell-lines was reversed. A significant down-regulation of genes involved in biosynthetic pathways including protein and lipid synthesis, and a significant up-regulation of genes responsible for cell cycle arrest were seen. The vast majority (114/138; 92%) of genes modulated by the single agents were similarly modulated by the combination. However, the latter induced a further significant change in the transcriptome, affecting an additional 390 genes. Similarly, methylation array data was analyzed following treatment of these drugs alone and in combination. DEC induced de-methylation of 190 different gene regions corresponding to 175 genes and an additional 335 loci. Interestingly, when combined with romidepsin the number of demethylated gene regions decreased to 85 corresponding to 79 genes, 78 of which were common with DEC and 148 additional loci. The comparison of gene expression and methylation demonstrated a significant inverse relationship (R2 = 0.657) with genes found to be differentially expressed in GEP and methylation analysis. (Figure 1) [Display omitted] These data support the observation that DNMTIs in combination with HDACIs produces significant synergistic activity in models of TCL. Further evaluation of the mechanism of action with DNMTIs in combination with HDACIs is ongoing, and a clinical trial of the combination is now open. Disclosures:O'Connor:Celgene Pharmaceuticals: Consultancy; Spectrum Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Allos Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Off Label Use: Hypomethylating Agents in T-cell lymphoma. Amengual:Acetylon Pharmacueticals, INC: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Pralatrexate: an emerging new agent with activity in T-cell lymphomas

T-cell lymphomas (TCL) represent a particularly poor prognosis subgroup of lymphomas. The goal of this review is to provide emerging information on one agent demonstrating activity in these challenging diseases. Pralatrexate is a novel antifolate designed to have high affinity for the reduced folate carrier type 1 (RFC-1). Preclinical and clinical studies have demonstrated that pralatrexate has significant activity against TCL. The high affinity of pralatrexate for RFC-1 significantly improves its internalization into cells. Preclinical studies in models of B-cell lymphomas and TCL have demonstrated that pralatrexate demonstrates activity superior to traditional antifolates. Phase I studies have shown the dose-limiting toxicity to be stomatitis, which can be abrogated with folic acid and vitamin B12 supplementation. Early phase studies have shown marked activity across a diverse panoply of TCL. Pralatrexate is an antifolate designed to be internalized more rapidly than other traditional antifolates. Preclinical studies have demonstrated its superiority to methotrexate, and early phase I and II studies have shown marked activity across many poor-risk subtypes of TCL. Future studies are directed towards understanding the pharmacokinetic features of the drug, and expanding the population of patients with TCL and B-cell lymphomas.