Pralatrexate: a comprehensive update on pharmacology, clinical activity and strategies to optimize use

Pralatrexate inhibited the replication of varicella zoster virus and vesicular stomatitis virus: An old dog with new tricks

Varicella zoster virus (VZV) is associated with herpes zoster (HZ) or herpes zoster ophthalmicus (HZO). All antiviral agents currently licensed for the management of VZV replication via modulating different mechanisms, and the resistance is on the rise. There is a need to develop new antiviral agents with distinct mechanisms of action and adequate safety profiles. Pralatrexate (PDX) is a fourth-generation anti-folate agent with an inhibitory activity on folate (FA) metabolism and has been used as an anti-tumor drug. We observed that PDX possessed potent inhibitory activity against VZV infection. In this study, we reported the antiviral effects and the underlying mechanism of PDX against VZV infection. The results showed that PDX not only inhibited VZV replication in vitro and in mice corneal tissues but also reduced the inflammatory response and apoptosis induced by viral infection. Furthermore, PDX treatment showed a similar anti-VSV inhibitory effect in both in vitro and in vivo models. Mechanistically, PDX inhibited viral replication by interrupting the substrate supply for de novo purine and thymidine synthesis. In conclusion, this study discovered the potent antiviral activity of PDX with a novel mechanism and presented a new strategy for VZV treatment that targets a cellular metabolic mechanism essential for viral replication. The present study provided a new insight into the development of broad-spectrum antiviral agents.

Past, present and future therapeutic approaches in nodal peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCL) encompass over 30 different entities and although they share post-thymic T- or NK-cell derivation, the disease biology and genomic landscape are very diverse across subtypes. In Western populations, nodal PTCL are the most frequently encountered entities in clinical practice and although important achievements have been made in deciphering the underlying biology and in therapeutic advances, there are still large gaps in disease understanding and clinical scenarios in which controversy over best practice continues. CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone)- based chemotherapy continues to be the 'standard' treatment, with the addition of brentuximab vedotin (BV) in the combination CHP (cyclosphosphamide, doxorubicin, prednisone)-BV representing a new treatment paradigm in CD30+ PTCL although its benefit is less certain in the non-anaplastic large cell lymphoma subtypes. Given the high risk of relapse, consolidative autologous stem cell transplant is considered in nodal PTCL, outside of ALK-positive anaplastic large cell lymphoma; however, in the absence of a randomized controlled trials, practices vary. Beyond CHP-BV, most study activity has focused on adding a novel agent to CHOP (i.e., CHOP + drug X). However, with high complete remission rates observed with some novel therapy combinations, these regimens are being tested in the front-line setting, with a particular rationale in follicular helper T-cell lymphomas which have a clear sensitivity to epigenetic modifying therapies. This is well exemplified in the relapsed/refractory setting in which rational combination therapies are being developed for specific subtypes or guided by underlying biology. Taken together, we have finally moved into an era of a more personalized approach to the management of nodal PTCL.

Pralatrexate in relapsed/refractory T-cell lymphoma: a retrospective multicenter study

We present a retrospective multicenter study of pralatrexate treatment outcomes in an Australian practice setting for patients with relapsed/refractory T-cell lymphoma who had failed 1+ systemic therapies, treated via a compassionate access program. Endpoints assessed included response rates, toxicities, and subsequent therapies. Progression-free survival (PFS), time to next treatment (TTNT), event-free survival (EFS), overall survival (OS), and time to best response, were assessed by Kaplan-Meier analysis. The study included 31 patients, with median age 69 years. We demonstrated ORR of 35.5% (n = 11), including 4 complete responses (13%) and 7 partial responses (23%). The predicted median OS was 10 months, with EFS of 9 months, and PFS of 9 months. Median TTNT was 8 months. Mucositis was the most commonly observed toxicity. This study - the second largest real-world cohort reported to date - underscores the importance of pralatrexate in relapsed/refractory T-cell lymphoma, as well as its acceptable toxicity profile.

Preclinical evaluation of the anti-tumor activity of pralatrexate in high-risk neuroblastoma cells

INTRODUCTION

Pralatrexate is a folate analogue inhibitor of dihydrofolate reductase exhibiting high affinity for reduced folate carrier-1 with antineoplastic and immunosuppressive activities, similar to methotrexate. Despite advances in multi-modality treatment strategies, the survival rates for children with high-risk neuroblastoma have failed to improve. Therefore, the intense research continues in order to identify the ideal novel agent or combination of chemotherapy drugs to treat high-risk neuroblastoma.

MATERIALS AND METHODS

Four human neuroblastoma cell lines were used to determine IC₅₀ values of select chemotherapy agents. Antiproliferative effects of pralatrexate were assessed by adherent and non-adherent colony formation assays. Cell cycle arrest and apoptosis were measured by flow cytometry and immunoblotting. PDX tissue culture was used to assess ex vivo efficacy.

RESULTS

Treatment with pralatrexate in all four neuroblastoma cell lines blocked cell growth in 2D and 3D culture conditions in a time-dependent manner. The potency of pralatrexate was ten-fold stronger than methotrexate, as measured by IC₅₀. Pralatrexate-induced apoptosis was confirmed by caspase-3 activation and PARP cleavage. MYCN and SLC19A1 mRNA expressions were decreased with pralatrexate in MYCN-amplified neuroblastoma cells.

CONCLUSIONS

Pralatrexate demonstrated effective inhibition of cell growth and viability. The higher potency of pralatrexate compared to methotrexate, a drug with high levels of toxicity, suggests pralatrexate may be a safer alternative to methotrexate as an effective chemotherapeutic agent in the treatment of patients with high-risk neuroblastoma.

Targeting dihydrofolate reductase: Design, synthesis and biological evaluation of novel 6-substituted pyrrolo[2,3-d]pyrimidines as nonclassical antifolates and as potential antitumor agents

A novel series of 6-substituted pyrrolo[2,3-d]pyrimidines with reversed amide moieties from the lead compound 1a were designed and synthesized as nonclassical antifolates and as potential antitumor agents. Target compounds 1-9 were successfully obtained through two sequential condensation reactions from the key intermediate 2-amino-6-(2-aminoethyl)-3,7-dihydro-4H-pyrrolo[2,3-d]pyrimidin-4-one. In preliminary antiproliferation assay, all compounds demonstrated submicromolar to nanomolar inhibitory effects against KB tumor cells, whereas compounds 1-3 also exhibited nanomolar antiproliferative activities toward SW620 and A549 cells. In particular, compounds 1-3 were significantly more potent than the positive control methotrexate (MTX) and pemetrexed (PMX) to A549 cells. The growth inhibition induced cell cycle arrest at G1-phase with S-phase suppression. Along with the results of nucleoside protection assays, inhibition assays of dihydrofolate reductase (DHFR) clearly elucidated that the intracellular target of the designed compounds was DHFR. Molecular modeling studies suggested two binding modes of the target compounds with DHFR.

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.

Development of new agents for peripheral T-cell lymphoma

INTRODUCTION

Peripheral T-cell lymphoma (PTCL) is a relatively rare, heterogeneous group of mature T-cell neoplasms generally associated with poor prognosis, partly because of refractoriness against conventional cytotoxic chemotherapies. To improve the outcome of patients with PTCL, the clinical development of several novel agents is currently under investigation.

AREAS COVERED

Since the first approval of pralatrexate (dihydrofolate reductase inhibitor) by the US Food and Drug Administration, belinostat, romidepsin (histone deacetylase inhibitors), and brentuximab vedotin (anti-CD30 antibody-drug conjugate) have been approved in the US, and many other countries. In addition, mogamulizumab (anti-CC chemokine receptor 4 antibody), chidamide (histone deacetylase inhibitor), and forodesine (purine nucleoside phosphorylase inhibitor) have been approved in Asian countries, including China, and Japan. In this review, we have summarized the available data regarding these approved agents and new agents currently under development for PTCL.

EXPERT OPINION

Novel agents will be a promising therapeutic option in selected patients with relapsed/refractory PTCL and will change the daily clinical practice in the treatment of PTCL. However, these are not a curative option when used as a single agent. Further clinical developments are expected, comprising 1) combination therapies of new agents with cytotoxic chemotherapies; 2) 'novel-novel' combinations; 3) immune therapies, including chimeric antigen receptor T-cell therapy; and 4) predictive marker analysis.

Therapeutic potential of pteridine derivatives: A comprehensive review

Pteridines are aromatic compounds formed by fused pyrazine and pyrimidine rings. Many living organisms synthesize pteridines, where they act as pigments, enzymatic cofactors, or immune system activation molecules. This variety of biological functions has motivated the synthesis of a huge number of pteridine derivatives with the aim of studying their therapeutic potential. This review gathers the state-of-the-art of pteridine derivatives, describing their biological activities and molecular targets. The antitumor activity of pteridine-based compounds is one of the most studied and advanced therapeutic potentials, for which several molecular targets have been identified. Nevertheless, pteridines are also considered as very promising therapeutics for the treatment of chronic inflammation-related diseases. On the other hand, many pteridine derivatives have been tested for antimicrobial activities but, although some of them resulted to be active in preliminary assays, a deeper research is needed in this area. Moreover, pteridines may be of use in the treatment of many other diseases, such as diabetes, osteoporosis, ischemia, or neurodegeneration, among others. Thus, the diversity of the biological activities shown by these compounds highlights the promising therapeutic use of pteridine derivatives. Indeed, methotrexate, pralatrexate, and triamterene are Food and Drug Administration approved pteridines, while many others are currently under study in clinical trials.

Systemic Treatment Options for Advanced-Stage Mycosis Fungoides and Sézary Syndrome

PURPOSE OF REVIEW

Cutaneous T-cell lymphoma (CTCL) is a rare form of non-Hodgkin lymphoma. Globally, the most common subtypes of CTCL are mycosis fungoides and Sézary syndrome. CTCL can confer significant morbidity and even mortality in advanced disease. Here we review the current and potential future treatments for advanced-stage CTCL.

RECENT FINDINGS

Heterogeneity of treatment choice has been demonstrated both in US and non-US centers. Systemic treatment choice is currently guided by prognostic features, incorporating stage, immunophenotypic and molecular findings, and patient-specific factors such as age and comorbidities. Randomized controlled studies are uncommon, and the literature is composed predominantly of retrospective, cohort, and early-phase studies. International consensus guidelines are available; however, the lack of comparative trials means that there is no clear algorithmic approach to treatment. This review article reports on the systemic treatment options in current use for advanced CTCL, and on the possible future therapies, acknowledging that an algorithmic approach is not yet forthcoming to guide treatment prioritization.