Ewa Lech-Marańda

Current Status of Older and New Purine Nucleoside Analogues in the Treatment of Lymphoproliferative Diseases

For the past few years more and more new cytotoxic agents active in the treatment of hematological malignancies have been synthesized and become available for either in vitro studies or clinical trials. Among them the class of antineoplastic drugs belonging to the purine nucleoside analogues group (PNAs) plays an important role. Three of them: pentostatin (DCF), cladribine (2-CdA) and fludarabine (FA) were approved by Food and Drug Administration (FDA) for the treatment of hematological malignancies. Recently three novel PNAs: clofarabine (CAFdA), nelarabine (ara-G) and forodesine (immucillin H, BCX-1777) have been synthesized and introduced into preclinical studies and clinical trials. These agents seem to be useful mainly for the treatment of human T-cell proliferative disorders and they are currently undergoing clinical trials in lymphoid malignancies. However, there are also several studies suggesting the role of these drugs in B-cell malignancies. This review will summarize current knowledge concerning the mechanism of action, pharmacologic properties, clinical activity and toxicity of PNAs accepted for use in clinical practice, as well as new agents available for clinical trials.

Toll-like receptors and their role in carcinogenesis and anti-tumor treatment

Toll-like receptors (TLRs) have been described as major components of the innate immune system, recognizing the conserved molecular structures found in the large groups of pathogens called pathogen-associated molecular patterns (PAMPs). TLR expression is ubiquitous, from epithelial to immunocompetent cells. TLR ligation triggers several adapter proteins and downstream kinases, leading to the induction of key pro-inflammatory mediators but also anti-inflammatory and anti-tumor cytokines. The result of this activation goes beyond innate immunity to shape the adaptive responses against pathogens and tumor cells, and maintains host homeostasis via cell debris utilization. TLRs have already become potent targets in infectious disease treatment and vaccine therapy and in neoplastic disease treatment, due to their ability to enhance antigen presentation. However, some studies show the dual effect of TLR stimulation on malignant cells: they can be proapoptotic or promote survival under different conditions. It is therefore crucial to design further studies assessing the biology of these receptors in normal and transformed cells. The established role of TLRs in human disease therapy is based on TLR7 and TLR4 agonists, respectively for the novel treatment of some types of skin cancer and for the anti-hepatitis B virus vaccine. Some clinical trials involving TLR agonists as potent enhancers of the anti-tumor response in solid tumors have begun.

Brentuximab Vedotin with Chemotherapy for Stage III or IV Hodgkin’s Lymphoma

BACKGROUND Brentuximab vedotin is an anti‐CD30 antibody–drug conjugate that has been approved for relapsed and refractory Hodgkins lymphoma. METHODS We conducted an open‐label, multicenter, randomized phase 3 trial involving patients with previously untreated stage III or IV classic Hodgkins lymphoma, in which 664 were assigned to receive brentuximab vedotin, doxorubicin, vinblastine, and dacarbazine (A+AVD) and 670 were assigned to receive doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD). The primary end point was modified progression‐free survival (the time to progression, death, or noncomplete response and use of subsequent anticancer therapy) as adjudicated by an independent review committee. The key secondary end point was overall survival. RESULTS At a median follow‐up of 24.9 months, 2‐year modified progression‐free survival rates in the A+AVD and ABVD groups were 82.1% (95% confidence interval [CI], 78.7 to 85.0) and 77.2% (95% CI, 73.7 to 80.4), respectively, a difference of 4.9 percentage points (hazard ratio for an event of progression, death, or modified progression, 0.77; 95% CI, 0.60 to 0.98; P=0.03). There were 28 deaths with A+AVD and 39 with ABVD (hazard ratio for interim overall survival, 0.72 [95% CI, 0.44 to 1.17]; P=0.19). All secondary efficacy end points trended in favor of A+AVD. Neutropenia occurred in 58% of the patients receiving A+AVD and in 45% of those receiving ABVD; in the A+AVD group, the rate of febrile neutropenia was lower among the 83 patients who received primary prophylaxis with granulocyte colony‐stimulating factor than among those who did not (11% vs. 21%). Peripheral neuropathy occurred in 67% of patients in the A+AVD group and in 43% of patients in the ABVD group; 67% of patients in the A+AVD group who had peripheral neuropathy had resolution or improvement at the last follow‐up visit. Pulmonary toxicity of grade 3 or higher was reported in less than 1% of patients receiving A+AVD and in 3% of those receiving ABVD. Among the deaths that occurred during treatment, 7 of 9 in the A+AVD group were associated with neutropenia and 11 of 13 in the ABVD group were associated with pulmonary‐related toxicity. CONCLUSIONS A+AVD had superior efficacy to ABVD in the treatment of patients with advanced‐stage Hodgkins lymphoma, with a 4.9 percentage‐point lower combined risk of progression, death, or noncomplete response and use of subsequent anticancer therapy at 2 years. (Funded by Millennium Pharmaceuticals and Seattle Genetics; ECHELON‐1 ClinicalTrials.gov number, NCT01712490; EudraCT number, 2011‐005450‐60.)

Combination Regimen of Cladribine (2-Chlorodeoxyadenosine), Cytarabine and G-CSF (CLAG) as Induction Therapy for Patients with Relapsed or Refractory Acute Myeloid Leukemia

The aim of the study was efficacy and toxicity evaluation of combination of 2-Chlorodeoxya-denosine (2-CdA) with cytarabine (Ara-C) and G-CSF (CLAG regimen) as reinduction therapy in patients with refractory or relapsed acute myeloid leukemia (AML). The protocol stipulated an infusion of 5 mg/m2 of 2-CdA over 2 hours daily for 5 consecutive days. A 4-hour infusion of Ara-C (2 g/m) was started 2 hours after each infusion of 2-CdA. G-CSF at a dose 300 μg s.c was given 24 hours before the first dose of 2-CdA for 6 days. In case of WBC>20×109/1 G-CSF was started simultaneously with 2-CdA. In the case of complete response (CR) consolidation treatment with 2-CdA containing regimens was started. In case of partial response a second identical course of CLAG was given. Response criteria were established according to those developed by the NCI Sponsored Workshop. Among 20 patients accrued all but 2 received at least one course of CLAG induction therapy in the planned doses. 10/20 (50%) (95% CI 27-73%) patients achieved a CR with a median duration of 22.5 weeks (range 3.5-53 weeks). Two (10%) patients had a PR and 8 were non-responders. One patient underwent peripheral blood stem cell transplantation. Overall 4 patients are in continuous CR with a median duration of 16.2 weeks (range 3.5-36.5). Among non-responders two patients did not receive the full dose of treatment because of complications during the cycle, both of them died; 3 died early after complete induction therapy before recovery of the bone marrow and 3 were resistant to CLAG. All 20 patients but one experienced granulocytopenia <0.2×109/1 and thrombocytopenia <20×109/1. Median time to reach PMN>0.5×109 G/1 was 18.7 days and platelets>50×109/1 was 27.2 days. In conclusion, the CLAG regimen had significant antileukemic activity and acceptable toxicity as reinduction treatment in refractory or relapsed AML patients.

A multicenter, open, non-comparative, phase II study of the combination of cladribine (2-chlorodeoxyadenosine), cytarabine, and G-CSF as induction therapy in refractory acute myeloid leukemia - a report of the Polish Adult Leukemia Group (PALG).

Objectives: To evaluate the efficacy and toxicity of cladribine (2‐chlorodeoxyadenosine, 2‐CdA), cytarabine (Ara‐C), and granulocyte‐colony stimulating factor (G‐CSF) (CLAG) regimen in refractory acute myeloid leukemia (AML) in the multicenter phase II study.

Cladribine in combination with mitoxantrone and cyclophosphamide (CMC) in the treatment of heavily pre-treated patients with advanced indolent lymphoid malignancies

Abstract: The aim of our study was to determine the effectiveness and toxicity of combined chemotherapy consisting of cladribine (2‐chloro‐deoxyadenosine, 2‐CdA), mitoxantrone and cyclophosphamide (CMC regimen) in the treatment of refractory or relapsed indolent lymphoproliferative disorders. The treatment course consisted of 2‐CdA given at a dose of 0.12 mg/kg/24 h in a 2‐h intravenous infusion for 5 (CMC5) or 3 (CMC3) consecutive days, mitoxantrone 10 mg/m2 on day 1 and cyclophosphamide 650 mg/m2/iv on day 1. Thirty‐three patients (19 with B‐CLL and 14 with LG‐NHL) entered the study and all of them were eligible. Twenty patients (60.6%) were recurrent after prior therapy and 13 (39.4%) had refractory disease. All patients received 5 or more cycles of chemotherapy before CMC treatment. Twenty‐one patients were treated with CMC5 regimen and 12 with CMC3 regimen. The overall response rate, including CR and PR, was 48.6% (95% CI 32–66). There were no differences in the frequency of responses between the CMC3 and CMC5 treated groups (p>0.05). One patient with B‐CLL and three patients with lymphocytic lymphoma achieved CR (12.1%). Among 12 patients (36.4%) who achieved PR there were 6 CLL patients, and 6 lymphoma patients. The major toxicity was myelosuppression. Severe neutropenia was seen in 11/33 (33.3%) patients, more frequently in patients who received CMC5 than in the patients who received CMC3, both in the CLL (50.0% and 28.5%, respectively) and in the LG‐NHL group (22.2% and 0%, respectively). The rate of thrombocytopenia was similar in both groups. Infections and fever of unknown origin complicated the treatment with CMC5 more often than with CMC3: five episodes were seen in 3 patients treated with CMC3 when compared to 15 episodes in 12 patients treated with CMC5. In conclusion, the CMC programme is an active combined regimen in heavily pre‐treated CLL and LG‐NHL patients. However, its toxicity is significant and we suggest a shortening of 2‐CdA infusion from 5 to 3 d in further studies. Whether a combination of 2‐CdA with cyclophosphamide and mitoxantrone would result in improved outcome as compared to 2‐CdA alone, is being investigated in a prospective, randomised trial.

Toll-Like Receptors and their Role in Hematologic Malignancies

Toll-like receptors (TLR) constitute one of the components of the innate immunity, based on the recognition of conserved molecular structures found in large groups of pathogens. A total of 11 Toll-like receptors have now been described in humans. Toll-like receptors are expressed on virtually every type of cell, including immunocompetent cells. Ligand binding triggers signaling cascade that leads to the induction of key proinflammatory mediators that contribute to an immune response. Additionally, TLR induction results in the activation and shaping of the adaptive immune reaction. TLRs have also been identified as potential therapeutic targets. Their capability to augment antigen presentation or induce the expression of target molecules has rendered them plausible therapeutic agents. Recently, synthetic ligands have been described and some of them have already been established in the treatment of skin cancer (TLR7 agonist) and as anti-hepatitis B virus vaccine adjuvants (TLR4 agonists). Furthermore, many clinical trials on TLR agonists as potent enhancers of anti-tumor response in solid tumors are currently on going. Considering that TLRs are widely expressed on transformed cells of the immune system (from blasts to memory cells), they may become a promising candidate for developing effective therapeutic options in hematologic malignancies as many in vitro studies have shown the intact functionality of TLRs in transformed cells. Moreover, a few clinical trials investigating the safety of synthetic TLR agonists are currently ongoing. Therefore, it is necessary to conduct further studies in order to assess the clinical relevance of the applicability of TLR-aimed therapy in the treatment of hematologic malignancies.

Novel Purine Nucleoside Analogues for Hematological Malignancies

Recently, the search for more effective and safer antineoplastic agents has led to synthesis and introduction into preclinical and clinical studies of a few new purine nucleoside analogues (PNA). Three of them: clofarabine (CAFdA), nelarabine, and forodesine (immucillin H, BCX-1777), despite belonging to the same group of drugs such as PNA, have shown some differences concerning their active forms, metabolic properties and mechanism of action. However, all these drugs have demonstrated promising activity in patients with relapsed and refractory acute lymphoblastic leukemia (ALL). CAFdA was approved for the therapy of relapsed or refractory ALL in the third line of treatment. It has proved promising in pediatric patients as well as in some patients who are able to proceed to allogenic hematopietic stem cell transplantation (HSCT). Moreover, the drug exhibits an efficacy in acute myeloid leukemia (AML), blast crisis of chronic myelogenous leukemia (CML-BP) and myelodysplastic syndrome (MDS). Nelarabine is recommended for T-ALL and T-cell lymphoblastic lymphoma (T-LBL) with the overall response rates ranging from 11 to 60%. However, the use of the drug is limited by potentially severe neurotoxicity. Forodesine is a purine nucleoside phosphorylase (PNP) inhibitor and it has shown activity in relapsed and refractory T- and B-cells leukemias as well as in cutaneous T-cell lymphoma (CTCL). Recently patented, a few of inventions in the field of pharmaceutical preparation of new PNA have also been published. Great hopes are currently set on the use of these drugs in the treatment of lymphoid and myeloid malignancies in adult and in pediatric patients, however ongoing studies will help to define their role in the standard therapy.

Depsipeptide (FK228) as a Novel Histone Deacetylase Inhibitor: Mechanism of Action and Anticancer Activity

Depsipeptide (FK228), a new histone deacetylase inhibitor, has been recently introduced into clinical trials. This agent shows interesting metabolic properties, novel mechanism of action, and is undergoing phase I-II clinical studies in hematopoietic malignancies and solid tumors. Mechanism of action, pharmacokinetics and anticancer activity of depsipeptide is the subject of this review.

Pharmacological and Clinical Studies on Purine Nucleoside Analogs- New Anticancer Agents

More recently, three novel purine nucleoside analogs, including clofarabine, nelarabine and immucillin H, have been introduced into clinical trials. These agents have different metabolic properties, novel mechanism of action, and are undergoing phase I-II clinical studies for the treatment of hematopoietic malignancies. Pharmacology and anticancer activity of PNA are the subjects of this review.