Preemptive leucovorin administration minimizes pralatrexate toxicity without sacrificing efficacy

Safety considerations with the current treatments for peripheral T-cell lymphoma

INTRODUCTION

Peripheral T-Cell Lymphomas (PTCL) constitute a heterogeneous group of aggressive T - and natural killer (NK)-cell disorders and are associated with a poor prognosis. Frontline treatments often consist of anthracycline-based combination chemotherapy with the exception of NK-T cell lymphomas, where such combinations are ineffective due to the presence of P-glycoprotein which leads to multidrug resistance. Infectious and immune mediated side effects might be more pronounced in or unique to T-cell lymphomas due to the selection of agents which target multiple T-cell subtypes and also an immunocompromised state induced by the lymphomas themselves.

AREAS COVERED

This review provides a comprehensive overview of safety considerations of treatment regimens used for peripheral T-cell lymphomas. We cover regimens used in both frontline and relapsed settings including combination chemotherapy, single agent chemotherapies and immunotherapies.

EXPERT OPINION

Treatment of T-cell lymphomas often requires sequencing of several therapies due to lower efficacy of available treatment regimens in curing the disease compared to that seen in B-cell non-Hodgkin lymphomas. In addition, certain complications are more common in T-cell lymphomas due to their unique immunobiology. An understanding of these salient aspects is important for all providers who treat patients with this challenging disease group.

Pralatrexate injection for the treatment of patients with relapsed or refractory peripheral T-cell lymphoma

INTRODUCTION

Peripheral T cell lymphomas (PTCL) are a heterogenous group of lymphoproliferative disorders which are generally not curable with conventional chemotherapy and associated with inferior outcomes. Pralatrexate is a novel folate analog, the first FDA approved drug) for the treatment of relapsed/refractory (R/R) PTCL.

AREAS COVERED

This paper provides a comprehensive review of PubMed literature describing the use of pralatrexate in R/R peripheral T-cell lymphoma. Pharmacokinetics and mechanism of action of pralatrexate are discussed as well as its clinical efficacy and safety in comparison to other agents available in R/R PTCL.

EXPERT OPINION

Pralatrexate is an active agent in relapsed/refractory PTCL with lower response rates seen in patients with angioimmunoblastic T cell lymphomas. Mucositis is the most frequently observed adverse event and this can be mitigated by the use of leucovorin along with cyanocobalamin and folic acid.

The rapidly changing landscape in mature T-cell lymphoma (MTCL) biology and management

Historical advances in the care of patients with non-Hodgkin lymphoma (NHL) have been restricted largely to patients with B-cell lymphoma. The peripheral T-cell lymphomas (PTCLs), which are rare and heterogeneous in nature, have yet to experience the same degree of improvement in outcome over the past 20 to 30 years. It is estimated that there are approximately 80,000 and 14,000 cases, respectively, of NHL and Hodgkin lymphoma per year in the United States. As a subgroup of NHL, the PTCLs account for 6% to 10% of all cases of NHL, making them exceedingly rare. In addition, the World Health Organization 2017 classification describes 29 distinct subtypes of PTCL. This intrinsic diversity, coupled with its rarity, has stymied progress in the disease. In addition, most subtypes carry an inferior prognosis compared with their B-cell counterparts, an outcome largely attributed to the fact that most treatment paradigms for patients with PTCL have been derived from B-cell neoplasms, a radically different disease. In fact, the first drug ever approved for patients with PTCL was approved only a decade ago. The plethora of recent drug approvals in PTCL, coupled with a deeper understanding of the molecular pathogenesis of the disease, has stimulated the field to pursue new avenues of research that are now largely predicated on the development of novel, targeted small molecules, which include a host of epigenetic modifiers and biologics. There is an expectation these advances may begin to favorably challenge the chemotherapy paradigms that have been used in the T-cell malignancies.

Pralatrexate for Prolonged Treatment of Refractory Peripheral T-Cell Lymphoma, Not Otherwise Specified, with Prophylactic Leucovorin

Peripheral T-cell lymphomas (PTCLs) are a rare and heterogenous group of hematological malignancies involving T or NK cells. PTCLs are generally associated with an aggressive course and poor prognosis. Pralatrexate (PDX) is the first FDA-approved agent for the treatment of refractory/recurrent PTCL. It has single-agent activity against PTCLs; however, oral mucositis represents dose-limiting toxicity in clinical practice. We report on the case of a patient administered with modified THP-COP therapy (pirarubicin [tetrahydropyranyl adriamycin], cyclophosphamide, and prednisone), who had bone or bone marrow as the primary lesion, which was treated successfully with PDX for an extended period of 1 year, with prophylactic use of leucovorin for oral mucositis. The maintenance dose of PDX was 30 mg/m² IV, over 3 consecutive weeks dosing with a 1-week rest period due to bone marrow suppression. The patient also received leucovorin 5 mg PO 3 times daily from days 2 to 6 after each PDX administration. Disease activity was well controlled, stable, and no oral mucositis was observed over the course of treatment.

Effect of leucovorin administration on mucositis and skin reactions in patients with peripheral T-cell lymphoma or cutaneous T-cell lymphoma treated with pralatrexate

Peripheral T-cell lymphoma (PTCL) and cutaneous T-cell lymphoma (CTCL) are rare, heterogeneous non-Hodgkin lymphomas with poor prognoses. Pralatrexate has demonstrated efficacy in T-cell lymphomas; however, mucositis has been reported as the most common dose-modifying adverse event. Leucovorin has been shown to minimize mucositis incidence, without sacrificing pralatrexate efficacy. We retrospectively studied 34 patients (7-PTCL/27-CTCL) treated with pralatrexate alone or pralatrexate and leucovorin. Leucovorin was administered preemptively prior to any mucositis occurrence. Pralatrexate dosing ranged from 10-30 mg/m² and clinical response or disease stabilization was observed in 85.2%. The incidence of mucositis was reduced in CTCL patients to 17% and was ameliorated in all but one patient with PTCL. There was no change the incidence of skin reactions with the addition of leucovorin. The response rates were similar to those previously reported in CTCL and PTCL. The addition of leucovorin reduced the incidence of mucositis in patients with CTCL and PTCL.

Phase I/II study of pralatrexate in Japanese patients with relapsed or refractory peripheral T-cell lymphoma

Pralatrexate is a novel antifolate approved in the USA for the treatment of relapsed or refractory peripheral T‐cell lymphoma. To assess its safety, efficacy, and pharmacokinetics in Japanese patients with this disease, we undertook a phase I/II study. Pralatrexate was given i.v. weekly for 6 weeks of a 7‐week cycle. All patients received concurrent vitamin B₁₂ and folic acid. In phase I, three patients received pralatrexate 30 mg/m² and none experienced a dose‐limiting toxicity. In phase II, we treated 22 additional patients with that dose. The median number of treatment cycles was 1 (range, 1–9). Nine of 20 evaluable patients (45%) achieved an objective response by central review, including two complete responses. All responses occurred within the first treatment cycle. At the time of data cut‐off, median progression‐free survival was 150 days. Median overall survival was not reached. In the total population, the most commonly reported adverse events included mucositis (88%), thrombocytopenia (68%), liver function test abnormality (64%), anemia (60%), and lymphopenia (56%). Grade 3/4 adverse events included lymphopenia (52%), thrombocytopenia (40%), leukopenia (28%), neutropenia (24%), anemia (20%), and mucositis (20%). The pharmacokinetic profile showed no drug accumulation with repeat dosing. These results indicate that pralatrexate is generally well tolerated and effective in Japanese patients with relapsed or refractory peripheral T‐cell lymphoma. This trial was registered with ClinicalTrials.gov (NCT02013362).

Highly Diverse Efficacy of Salvage Treatment Regimens for Relapsed or Refractory Peripheral T-Cell Lymphoma: A Systematic Review

Background

The goal of this study was to perform a systematic review to examine the efficacy and safety of various salvage therapy regimens on patients with relapsed/refractory PTCL.

Method

The electronic searches were performed using PubMed, Cochrane Library, EMBASE, and Web of Science from inception through June 2015, with search terms related to relapsed/refractory PTCL, salvage chemotherapy regimens, and clinical trials. An eligible study met the following inclusion criteria: (1) Patients had refractory or relapsed PTCL; (2) drug regimens were used for salvage therapy; (3) the study was a clinical trial; (4) the study reported on a series of at least 10 patients of PTCL.

Results

Of 35 records identified, a total of 14 studies were eligible for systematic reviews, and 12 different salvage regimens were investigated. A total of 618 relapsed/refractory PTCL patients were identified. The ORRs ranged from 22% for those treated with lenalidomide to 86% for those with brentuximab vedotin. By the three most frequent subtypes, the ORRs ranged from 14.2% to 71.5% for patients with the PTCL-NOS subtype, 8% to 54% for AITL subtypes, and 24% to 86% for the ALCL subtype. The medians of DOR, PFS, and OS ranged from 2.5 to 16.6 months, 2.6 to 13.3 months, and 3.6 to 14.5 months, respectively. The most frequently reported grade 3 or 4 adverse events (AEs) were hematological AEs, such as neutropenia and thrombocytopenia.

Conclusion

The efficacy of salvage therapy regimens is highly diverse for patients with relapsed/refractory PTCL; this heterogeneity in therapeutic effects might be due to the diversity in mechanisms, PTCL subtype distribution, and/or numbers/profiles of prior therapy. Comparative studies with matched pair analysis are warranted for more evidence of the salvage treatment effect on relapsed or heavily pretreated patients with PTCL.

Pralatrexate Monitoring Using a Commercially Available Methotrexate Assay to Avoid Potential Drug Interactions

Pralatrexate (PDX) is a folate antagonist structurally similar to methotrexate (MTX). Unlike MTX, it is currently not known whether PDX exhibits delayed clearance and heightened toxicity in the setting of fluid overload. A specific serum assay for PDX is not commercially available. To our knowledge, we report the first case using an MTX serum assay as a surrogate for PDX concentrations to avoid a potential drug-drug interaction with pralatrexate. We describe a 76-year-old man with refractory cutaneous T-cell lymphoma who began therapy with weekly PDX 15 mg/m(2) intravenous infusions on days 1, 8, and 15 of a 28-day cycle. He subsequently developed mucositis, a moderate right-sided pleural effusion, and peripheral edema over the next 5 weeks. Aggressive diuresis with furosemide was initiated, which was then withheld the day before his next PDX dose to avoid a potential drug-drug interaction between PDX and furosemide. His baseline MTX/PDX concentration (measured prior to administration of the cycle 2, week 2 PDX dose) was less than 0.20 μmol/L (i.e., undetectable). After PDX administration, his 1-hour peak MTX/PDX concentration increased to 0.58 μmol/L. Aggressive diuresis was withheld until his MTX/PDX concentration was undetectable, 43.5 hours later. PDX is more potent than MTX and displays similar pharmacokinetic properties. PDX concentrations using the serum MTX assay reflect lower values than those reported from PDX-specific assays in clinical studies. Because PDX is approved by the U.S. Food and Drug Administration for the treatment of uncommon malignancies, it is unlikely that a specific assay will be commercially developed. We propose that the MTX serum assay has merit for use in determining when to reinstate possible interacting drug therapies such as loop diuretics.

Practical Management of CD30⁺ Lymphoproliferative Disorders

Primary cutaneous CD30⁺ lymphoproliferative disorders (LPDs) account for approximately 25% of cutaneous lymphomas. Although these LPDs are clinically heterogeneous, they can be indistinguishable histologically. Lymphomatoid papulosis rarely requires systemic treatment; however, multifocal primary cutaneous anaplastic large cell cutaneous lymphoma and large cell transformation of mycosis fungoides are typically treated systemically. As CD30⁺ LPDs are rare, there is little published evidence to support a specific treatment algorithm. Most studies are case reports, small case series, or retrospective reviews. This article discusses various treatment choices for each of the CD30⁺ disorders and offers practical pearls to aid in choosing an appropriate regimen.

Novel treatments for T-cell lymphoma

T-cell lymphomas are a biologically and clinically diverse collection of diseases that collectively account for 10% to 15% of non-Hodgkin lymphomas. Unlike B-cell lymphomas, the response of T-cell lymphomas to standard anthracycline-containing chemotherapy regimens is suboptimal and the prognosis of patients is accordingly poor. To address these shortcomings, there has been a proliferation in biologic agents with novel mechanisms of action that target surface antigens, signaling pathways, or cellular processes. Given the large number of candidate molecules showing preclinical promise and the rarity of these diseases, drug development for peripheral T-cell lymphoma is challenging. We provide an overview of agents that have recently been approved for relapsed/refractory T-cell lymphoma and highlight efforts to introduce these agents into front-line treatment protocols in combination with chemotherapy. We discuss biologic doublets currently being evaluated as "chemotherapy-free" salvage regimens and highlight some of the most promising investigational agents in early clinical development.

Leucovorin rescue allows effective high-dose pralatrexate treatment and an increase in therapeutic index in mesothelioma xenografts

Purpose

To investigate the ability of leucovorin (LV) to abrogate dose-limiting toxicities of pralatrexate (PDX) while maintaining efficacy, in vivo.

Methods

H2052 mesothelioma cells were treated with the antifolates methotrexate (MTX), PDX and pemetrexed, with and without LV rescue 24 h later. Cell killing was evaluated 48 h later. Female nude mice bearing H2052 xenografts were treated with varying doses and schedules of the antifolate PDX and LV.

Results

In vitro, H2052 cells were more sensitive to PDX as compared to MTX and pemetrexed. Administration of LV 24 h after antifolate treatment reduced efficacy of antifolates MTX and pemetrexed, but not PDX. In vivo, LV was found to reduce toxicity of PDX at the maximum tolerated dose without sacrificing efficacy. Lethal doses of PDX were rescued by LV, and mice bearing the H2052 tumor demonstrated prolonged and enhanced tumor regression.

Conclusions

High-dose PDX with subsequent LV rescue may be a viable treatment strategy in mesothelioma and other cancers. The inclusion of LV rescue into new and existing PDX treatment protocols should be explored as a way to expand the tolerability and effectiveness of PDX in the clinic.

The impact of 5-formyltetrahydrofolate on the anti-tumor activity of pralatrexate, as compared to methotrexate, in HeLa cells in vitro

PURPOSE

To investigate the impact of 5-formyltetrahydrofolate on the activities of pralatrexate, as compared to methotrexate (MTX), in vitro.

METHODS

Cells were exposed to (6S)5-formyltetrahydrofolate (5-formylTHF) for 24 h, before or after a 6-h exposure to antifolates following which the cellular accumulation and activities of the drugs were evaluated in HeLa cells.

RESULTS

A 24-h delay between a 6-h exposure to antifolates and a subsequent 24-h exposure to 4 μM 5-formylTHF sustained the full activities of both antifolates. A 72-h interval was required between a single exposure of up to 4 μM 5-formylTHF and subsequent exposure to drugs to sustain activities of the antifolates. When cells were incubated with 4 μM 5-formylTHF for 24 h weekly, for 4 weeks, there was no significant increase in the IC50 for pralatrexate, but the MTX IC50 increased 2.5-fold as compared to cells growing continuously in 25 nM 5-formylTHF. This cyclical exposure to 5-formylTHF increased the cell folate pool by 16 %, had no significant effect on the intracellular pralatrexate level, but decreased intracellular MTX by 15 %. An extracellular concentration of MTX 50-fold higher than that of pralatrexate was required to achieve an intracellular level, and growth inhibition, comparable to that of pralatrexate.

CONCLUSIONS

Cyclical exposures to 5-formylTHF at levels in excess of what is achieved in most clinical "rescue" regimens do not affect pralatrexate accumulation nor antitumor activity in HeLa cells, in contrast to MTX. An important element in preserving pralatrexate activity is achieving a sufficient interval between exposure to 5-formylTHF and the next dose of antifolate.