The use of higher dose clofarabine in adults with relapsed acute lymphoblastic leukemia

Medicinal Potential of Heterocyclic Compounds from Diverse Natural Sources for the Management of Cancer

Natural products form a significant portion of medicinal agents that are currently used for the management of cancer. All these natural products have unique structures along with diverse action mechanisms with the capacity to interact with different therapeutic targets of several complex disorders. Although plants contribute as a major source of natural products with anti-cancer potential, the marine environment and microbes have also bestowed some substantial chemotherapeutic agents. A few examples of anti-cancer agents of natural origin include vincristine, vinblastine, paclitaxel, camptothecin and topotecan obtained from plants, bryostatins, sarcodictyin and cytarabine from marine organisms and bleomycin and doxorubicin from micro-organisms (dactinomycin, bleomycin and doxorubicin). The incredible diversity in the chemical structures and biological properties of compounds obtained from million species of plants, marine organisms and microorganisms present in nature has commenced a new era of potential therapeutic anti-cancer agents.

[18F] Clofarabine for PET Imaging of Hepatocellular Carcinoma

Clinical diagnosis of hepatocellular carcinoma (HCC) relies heavily on radiological imaging. However, information pertaining to liver cancer treatment such as the proliferation status is lacking. Imaging tumor proliferation can be valuable in patient management. This study investigated ¹⁸F-labeled clofarabine ([¹⁸F]CFA) targeting deoxycytidine kinase (dCK) for PET imaging of dCK-dependent proliferation in HCC. Since clinical PET scans showed a high liver background uptake of [¹⁸F]CFA, the aim of this study was to reduce this liver background uptake. A clinically relevant animal model of spontaneously developed HCC in the woodchucks was used for imaging experiments. Several modifiers were tested and compared with the baseline PET scan: Forodesine, probenecid, and cold clofarabine, all applied before the hot [¹⁸F]CFA injection to evaluate the reduction in liver background uptake. Application of forodesine before hot [¹⁸F]CFA injection did not reduce the background uptake. Instead, it increased the background by 11.6–36.3%. Application of probenecid also increased the liver background uptake by 16.6–32.1%. Cold CFA application did reduce the liver background uptake of [¹⁸F]CFA, comparing to the baseline scan. Combining cold CFA with [¹⁸F]CFA for PET imaging of liver cancers is a promising strategy, worthy of further clinical evaluation.

Clofarabine for the treatment of adult acute lymphoid leukemia: the Group for Research on Adult Acute Lymphoblastic Leukemia intergroup

Clofarabine, a second-generation purine analog displaying potent inhibition of DNA synthesis and favorable pharmacologic profile, is approved for the treatment of acute lymphoblastic leukemia (ALL) after failure of at least two previous regimens in patients up to 21 years of age at diagnosis. Good neurologic tolerance, synergy with alkylating agents, management guidelines defined through pediatric ALL and adult acute myeloid leukemia, have also prompted its administration in more than 100 adults with Philadelphia chromosome-positive and negative B lineage and T lineage ALL, as single agent (40 mg/m(2)/ day for 5 days), or in combination. In a Group for Research on Adult Acute Lympho- blastic Leukemia (GRAALL) retrospective study of two regimens (clofarabine ± cyclophosphamide + / - etoposide (ENDEVOL) ± mitoxantrone ± asparaginase ± dexamethasone (VANDEVOL)), remission was achieved in 50% of 55 relapsed/refractory patients, and 17-35% could proceed to allogeneic stem cell. Clofarabine warrants further exploration in advanced ALL treatment and bridge-to-transplant.

Natural Products as a Vital Source for the Discovery of Cancer Chemotherapeutic and Chemopreventive Agents

Throughout history, natural products have played a dominant role in the treatment of human ailments. For example, the legendary discovery of penicillin transformed global existence. Presently, natural products comprise a large portion of current-day pharmaceutical agents, most notably in the area of cancer therapy. Examples include Taxol, vinblastine, and camptothecin. These structurally unique agents function by novel mechanisms of action; isolation from natural sources is the only plausible method that could have led to their discovery. In addition to terrestrial plants as sources for starting materials, the marine environment (e.g., ecteinascidin 743, halichondrin B, and dolastatins), microbes (e.g., bleomycin, doxorubicin, and staurosporin), and slime molds (e.g., epothilone B) have yielded remarkable cancer chemotherapeutic agents. Irrespective of these advances, cancer remains a leading cause of death worldwide. Undoubtedly, the prevention of human cancer is highly preferable to treatment. Cancer chemoprevention, the use of vaccines or pharmaceutical agents to inhibit, retard, or reverse the process of carcinogenesis, is another important approach for easing this formidable public health burden. Similar to cancer chemotherapeutic agents, natural products play an important role in this field. There are many examples, including dietary phytochemicals such as sulforaphane and phenethyl isothiocyanate (cruciferous vegetables) and resveratrol (grapes and grape products). Overall, natural product research is a powerful approach for discovering biologically active compounds with unique structures and mechanisms of action. Given the unfathomable diversity of nature, it is reasonable to suggest that chemical leads can be generated that are capable of interacting with most or possibly all therapeutic targets.

Phase 1 dose-escalation trial of clofarabine followed by escalating dose of fractionated cyclophosphamide in adults with relapsed or refractory acute leukaemias

The prognosis of patients with relapsed and refractory acute leukaemia (RRAL) is very poor. Forty patients with RRAL were enroled [28 acute myeloid leukaemia (AML), 12 acute lymphoblastic leukaemia (ALL)] in this Phase 1 dose-escalation trial of daily-infused clofarabine (CLO) followed by cyclophosphamide (CY) for four consecutive days (CLO-CYx4). The median age was 48·5 years. The median number of prior regimens was 2 (range 1-5), and 6/40 patients (15%) had prior allogeneic haematopoietic stem cell transplant. 28/40 patients (70%) had adverse genetic features. 6/40 patients (15%) died within 60 d of induction (two infections, four progressive disease). The average time to neutrophil recovery (absolute neutrophil count ≥0·5 × 10(9) /l was 34 d, (range, 17-78). The overall response rate (ORR) was 33% (13/40), with seven complete remissions (18%), four complete remissions with incomplete recovery of blood counts (10%), and two partial remissions (5%). ORR was 25% (7/28), and 50% (6/12), for AML and ALL respectively. Notably, the clinical responses were independent of dose level. 7/17 patients (41%) exhibited CLO-mediated enhancement of CY-induced DNA, which was associated with, but not necessary for, improved clinical outcomes. In summary, the CLO-CYx4 regimen was well tolerated and had activity in patients with RRAL, especially relapsed ALL. Therefore, CLO-CYx4 can be considered a salvage therapy for adults with RRALs, and warrants further investigations.

Phase I trial and pharmacokinetic study of high-dose clofarabine and busulfan and allogeneic stem cell transplantation in adults with high-risk and refractory acute leukemia

We conducted a phase I trial to determine the maximum tolerated dose (MTD) of clofarabine with high-dose busulfan followed by allogeneic stem cell transplantation (SCT) in patients with high-risk and refractory acute leukemia. Patients received intravenous busulfan 0.8 mg/kg every 6 h on days -6 to -3 and clofarabine 30-60 mg/m(2) per day on days -6 to -2. Graft-versus-host disease prophylaxis included sirolimus plus tacrolimus (days -2 to +180). A total of 15 patients, median age 48 (30-58) years, with acute leukemia that was relapsed and refractory (n=8), primary refractory (n=6), or in CR2 (n=1), were treated at four clofarabine dose levels: 30 (n=3), 40 (n=3), 50 (n=3) and 60 mg/m(2) per day (n=6) with busulfan. All engrafted, and the MTD was not reached. Grades 3-4 non-hematological toxicities included vomiting (n=3), mucositis (n=9), hand-foot syndrome (n=1), acute renal failure (n=1) and reversible elevation of aspartate aminotransferase/alanine aminotransferase (n=10). The 1-year event-free survival was 53% (95% confidence interval: 33-86%), and the 1-year overall survival was 60% (95% confidence interval: 40-91%). Given the good tolerability and promising results, we recommend clofarabine 60 mg/m(2) per day × 5 days as a phase II dose in combination with busulfan (12.8 mg per kg total dose) for further study as a myeloablative regimen for allogeneic SCT for high-risk acute leukemia.

A phase I trial of high-dose clofarabine, etoposide, and cyclophosphamide and autologous peripheral blood stem cell transplantation in patients with primary refractory and relapsed and refractory non-Hodgkin lymphoma

Clofarabine has significant single-agent activity in patients with indolent and aggressive non-Hodgkin lymphoma and synergizes with DNA-damaging drugs. Treatment, however, may be associated with severe and prolonged myelosuppression. We conducted a phase I trial to determine the maximum tolerated dose (MTD) of clofarabine in combination with high-dose etoposide and cyclophosphamide followed by autologous peripheral blood stem cell transplantation in patients with refractory non-Hodgkin lymphoma (NHL). Patients received clofarabine at 30-70 mg/m(2)/day on days -6 to -2 in successive cohorts, in combination with etoposide 60 mg/kg (day -8), and cyclophosphamide 100 mg/kg (day -6), followed by filgrastim-mobilized PBSC on day 0. Sixteen patients of median age 57 (range: 32-67) years with diffuse large B cell (n = 8), follicular (n = 5), or mantle cell (n = 3) lymphoma that was either primary refractory (n = 2) or relapsed and refractory (n = 14) were treated at 5 clofarabine dose levels: 30 (n = 3), 40 (n = 3), 50 (n = 3), 60 (n = 3), and 70 mg/m(2)/day (n = 4) in combination with etoposide and cyclophosphamide. All patients had grade 4 neutropenia and thrombocytopenia. Grade 3-4 nonhematologic toxicity was evenly distributed across all 5 dose levels, and included diarrhea (n = 3), mucositis (n = 1), nausea (n = 1), reversible elevation of alanine aminotranferease/aspartate aminotransferase (AST/ALT) (n = 1) or bilirubin (n = 1), and hemorrhagic cystitis (n = 1); all resolved by day +30 following transplantation. The MTD was not reached. No treatment-related deaths occurred. At day +30, 13 patients achieved a complete remission (CR) or unconfirmed CR (CR(U)), and 2 patients achieved a partial response, for an overall response rate of 94%. After a median follow-up of 691 days, the 1-year progression-free survival (PFS) and overall survival (OS) were 63% (95% confidence interval [CI]: 43%-91%) and 68% (95% CI: 49%-96%), respectively. We recommend clofarabine 70 mg/m(2)/day × 5 days as a phase II dose in combination with high-dose etoposide and cyclophosphamide for further testing as a preparative regimen in NHL patients undergoing autologous PBSC transplantation.

Emerging therapy for the treatment of acute lymphoblastic leukemia

IMPORTANCE OF THE FIELD

Over the last few decades, advances in acute lymphoblastic leukemia (ALL) therapy have led to long-term survival rates of > 80% in children; however, comparable rates have yet to be achieved in adults, and a large majority of patients relapse from their disease.

AREAS COVERED IN THIS REVIEW

The review describes historical therapy and advancements in ALL treatment over the past few decades, while providing a concise review of the future direction of ALL therapy. Literature was collected through peer reviewed journals and the Pharmaprojects drug profile for ALL.

WHAT THE READER WILL GAIN

Current information regarding prognostic factors for relapse, salvage therapy options and emerging drugs are provided in the review.

TAKE HOME MESSAGE

Development of new drugs with novel mechanisms, unique formulations of existing medications, as well as manipulation of current combinations of drugs remain vital to the success in adult ALL.

Apoptotic effects of mahanine on human leukemic cells are mediated through crosstalk between Apo-1/Fas signaling and the Bid protein and via mitochondrial pathways

Apo-1 (Fas/CD95), a cell surface receptor, triggers apoptosis after binding to its physiological ligand, Apo-1L (FasL/CD95L). This study reports that mahanine, purified from the leaves of Murraya koenigii, has a dose- and time-dependent anti-proliferative activity in acute lymphoid (MOLT-3) and chronic myeloid (K562) leukemic cell lines and in the primary cells of leukemic and myeloid patients, with minimal effect on normal immune cells including CD34(+) cells. Leukemic cells underwent phosphatidylserine externalization and DNA fragmentation, indicating mahanine-induced apoptosis. An increase in reactive oxygen species suggests that the mahanine-induced apoptosis was mediated by oxidative stress. A significant drop in the Bcl2/Bax ratio, the loss of mitochondrial transmembrane potential as well as cytochrome c release from the mitochondria to the cytosol suggested involvement of the mitochondrial pathway of apoptosis. Cytochrome c release was followed by the activation of caspase-9, caspase-3 and caspase-7, and cleavage of PARP in both MOLT-3 and K562 cells. In MOLT-3 cells, formation of the Fas-FasL-FADD-caspase-8 heterotetramer occurred, leading to the cleavage of Bid to its truncated form, which consequently resulted in formation of the mitochondrial transmembrane pore. The incubation of MOLT-3 cells with mahanine in the presence of caspase-8 inhibitor or FasL-neutralizing NOK-2 antibody resulted in the decrease of mahanine-induced cell death. Mahanine was also a potent inhibitor of K562 xenograft growth, which was evident in an athymic nude mice model. In summary, these results provide evidence for involvement of the death receptor-mediated extrinsic pathway of apoptosis in the mahanine-induced anticancer activity in MOLT-3 cells, but not in K562 cells, which are deficient in Fas/FasL.