Clofarabine, cyclophosphamide and etoposide for the treatment of relapsed or resistant acute leukemia in pediatric patients

PAX5 alterations in an infant case of KMT2A-rearranged leukemia with lineage switch

Lineage switch is a rare event at leukemic relapse. While mostly known to occur in KMT2A-rearranged infant leukemia, the underlying mechanism is yet to be depicted. This case report describes a female infant who achieved remission of KMT2A-MLLT3-rearranged acute monocytic leukemia, but six months thereafter, relapsed as KMT2A-MLLT3-rearranged acute lymphocytic leukemia. Whole exome sequencing of the bone marrow obtained pre-post lineage switch revealed two somatic mutations of PAX5 in the relapse sample. These two PAX5 alterations were suggested to be loss of function, thus to have played the driver role in the lineage switch from AML to ALL.

Clofarabine with topotecan, vinorelbine, and thiotepa reinduction regimen for children and young adults with relapsed AML

Effective reinduction regimens are needed for children with relapsed and refractory acute myeloid leukemia (AML) as outcomes remain poor. Therapeutic options are limited in this heavily pre-treated patient population, many of whom have reached lifetime recommended doses of anthracycline chemotherapy. The development of effective non-anthracycline based salvage regimens is crucial to these patients who are at significant risk of life-threatening cardiotoxicity. We previously reported results of a phase 2 trial of a clofarabine-based regimen with topotecan, vinorelbine, and thiotepa (TVTC) in patients with relapsed acute leukemias. Here we report on an expanded bicenter cohort of 33 patients, <25 years of age, with relapsed/refractory (R/R) AML treated with up to 2 cycles of the TVTC reinduction regimen from 2007 to 2018. The overall response rate (ORR), defined as complete remission (CR) or CR with partial recovery of platelet count (CRp), was 71.4% (95%CI: 41.9 to 91.6%) for those patients in first relapse (n=14) and 47.4% ( 95%CI: 24.4 to 71.1%) for patients in 2nd or greater relapse or refractory disease. Responses were seen across multiple high risk cytogenetic and molecular subtypes, with 84% of responders successfully bridged to allogeneic stem cell transplantation. The 5-year OS for patients in first relapse was 46.2% (95%CI: 19.1 to 73.3%) and 50.0% (95%CI: 26.9 to 73.1%) for patients who responded to TVTC. For pediatric and young adult patients with R/R AML, TVTC reinduction compares favorably with currently used salvage regimens and warrants further exploration.

Clofarabine added to intensive treatment in adult patients with newly diagnosed ALL: the HOVON-100 trial

Clofarabine (CLO) is a nucleoside analogue with efficacy in relapsed/refractory acute lymphoblastic leukemia (ALL). This randomized phase III study aimed to evaluate whether CLO added to induction and consolidation would improve outcome in adults with newly diagnosed ALL. Treatment for younger (18-40 years) patients consisted of a pediatric inspired protocol and for older patients (41-70 years) of a semi-intensive protocol was used. 340 patients were randomized. After a median follow up of 70 months, 5-year EFS was 50% and 53% for arm A and B (CLO arm). For patients ≤40 years, EFS was 58% vs 65% in arm A vs B, while in patients >40 years EFS was 43% in both arms. CR rate was 89% in both arms and similar in younger and older patients. Minimal residual disease (MRD) was assessed in 200 patients (60%). Fifty-four of 76 evaluable patients (71%) were MRD negative after consolidation 1 in arm A vs 75/81 (93%) in arm B (p=0.001). Seventy (42%) patients proceeded to allogeneic hematopoietic stem cell transplantation in both arms. Five years OS was similar in both arms, 60% vs 61%. Among patients achieving CR, relapse rates were 28% and 24%, and non-relapse mortality was 16% vs 17% after CR. CLO treated patients experienced more serious adverse events, more infections, and more often went off-protocol. This was most pronounced in older patients. We conclude that, despite a higher rate of MRD-negativity, addition of CLO does not improve outcome in adults with ALL, which might be due to increased toxicity. The trial is registered at www.trialregister.nl as NTR2004.

Acute Lymphoblastic Leukemia, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

The NCCN Guidelines for Acute Lymphoblastic Leukemia (ALL) focus on the classification of ALL subtypes based on immunophenotype and cytogenetic/molecular markers; risk assessment and stratification for risk-adapted therapy; treatment strategies for Philadelphia chromosome (Ph)-positive and Ph-negative ALL for both adolescent and young adult and adult patients; and supportive care considerations. Given the complexity of ALL treatment regimens and the required supportive care measures, the NCCN ALL Panel recommends that patients be treated at a specialized cancer center with expertise in the management of ALL This portion of the Guidelines focuses on the management of Ph-positive and Ph-negative ALL in adolescents and young adults, and management in relapsed settings.

Cost-Effectiveness of Tisagenlecleucel in Paediatric Acute Lymphoblastic Leukaemia (pALL) and Adult Diffuse Large B-Cell Lymphoma (DLBCL) in Switzerland

INTRODUCTION

The purpose of the present analysis was to explore the cost-effectiveness of tisagenlecleucel in relapsed or refractory (r/r) paediatric acute lymphoblastic leukaemia (pALL) and r/r adult diffuse large B-cell lymphoma (DLBCL) in Switzerland against a range of historical standard-of-care treatments.

METHODS

Two cost-utility models were constructed for the two licensed indications using similar methodologies but indication-specific data. Clinical efficacy data were based on pooled analyses of clinical trials for tisagenlecleucel (pALL: ELIANA, ENSIGN, B2101J; DLBCL: JULIET, NCT02030834) and published data for comparator treatments. Treatment effects were compared based on matching-adjusted indirect comparison (MAIC) analyses. Four clinical lymphoma and leukaemia experts provided Switzerland-specific input regarding comparators, diagnostic and therapeutic procedures, clinical evidence and costs, which were used to inform the models. The base case analysis reflected the perspective of the Swiss mandatory health insurance system. Deterministic, probabilistic and scenario analyses were carried out to explore the robustness of results.

RESULTS

The base case analysis resulted in incremental costs of CHF 31,961-CHF 36,419 per quality-adjusted life year (QALY) gained for pALL across the different comparators and CHF 113,179 for DLBCL (1 CHF = 1.09 USD). Incremental costs per life-year gained ranged between CHF 33,906-CHF 97,399 across the two indications. Including productivity gains, tisagenlecleucel was shown to be dominant (more effective and less costly) over all the comparators for pALL and to result in incremental costs per life-year gained of CHF 57,324 for DLBCL.

CONCLUSION

Using hypothetical willingness-to-pay thresholds of CHF 100,000-150,000 per QALY gained, the present analysis has shown tisagenlecleucel to be a cost-effective treatment option in pALL and DLBCL.

Successful combination chemotherapy involving clofarabine, cyclophosphamide, and etoposide for pediatric relapsed acute myeloid leukemia: A case report

Limited salvage chemotherapies are available for relapsed/refractory acute myeloid leukemia. Herein, we described successful reinduction chemotherapy, involving a combination of clofarabine, cyclophosphamide, and etoposide, in a 12-year-old male with relapsed acute myeloid leukemia prior to allogeneic bone marrow transplantation from his father. Although treatment with a combination of fludarabine, cytarabine, granulocyte colony-stimulating factor, idarubicin, and gemtuzumab ozogamicin had no positive effects, the aforementioned clofarabine-based chemotherapy induced complete remission and allowed the transplantation to go ahead. The abovementioned regimen may be useful for induction chemotherapy prior to hematopoietic stem cell transplantation for refractory/relapsed acute myeloid leukemia.

Pediatric Acute Lymphoblastic Leukemia, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy. Advancements in technology that enhance our understanding of the biology of the disease, risk-adapted therapy, and enhanced supportive care have contributed to improved survival rates. However, additional clinical management is needed to improve outcomes for patients classified as high risk at presentation (eg, T-ALL, infant ALL) and who experience relapse. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for pediatric ALL provide recommendations on the workup, diagnostic evaluation, and treatment of the disease, including guidance on supportive care, hematopoietic stem cell transplantation, and pharmacogenomics. This portion of the NCCN Guidelines focuses on the frontline and relapsed/refractory management of pediatric ALL.

Cost-Effectiveness Analysis of Tisagenlecleucel for the Treatment of Pediatric and Young Adult Patients with Relapsed or Refractory B Cell Acute Lymphoblastic Leukemia in Japan

Until recently, treatment options were relatively limited for children and young adults with relapsed or refractory (r/r) acute lymphoblastic leukemia (ALL). Tisagenlecleucel is a chimeric antigen receptor T cell (CAR-T) immunotherapy with promising efficacy and manageable safety that was approved in Japan in 2019 for the treatment of CD19-positive r/r B cell ALL (B-ALL). However, there is no publication assessing the cost-effectiveness of CAR-T in Japan. The objective of this study was to assess the cost-effectiveness of a tisagenlecleucel treatment strategy compared to a blinatumomab treatment strategy and a clofarabine combination treatment strategy (i.e., clofarabine + cyclophosphamide + etoposide) in Japan for pediatric and young adult patients up to 25 years of age with r/r B-ALL. A partitioned survival model with a lifetime horizon and monthly cycle was constructed from a Japanese public healthcare payer's perspective. Patients were distributed across the following partitioned health states: event-free survival (EFS), progressive disease, and death, which were informed by the EFS and overall survival (OS) data of respective clinical trials before year 5. For the tisagenlecleucel arm, a decision-tree structure was used to partition patients based on the infusion status; those who discontinued prior to receiving infusion were assigned efficacy and cost inputs of blinatumomab and those who received infusion were assigned efficacy and costs inputs based on tisagenlecleucel-infused patients. As trial data for blinatumomab and clofarabine ended before year 5, matching-adjusted indirect comparisons were used to extrapolate OS between the end of trial observation and up to year 5. All surviving patients followed the mortality risk of long-term ALL survivors without additional risk of disease relapse after year 5, regardless of initial treatment strategies. The model accounted for pretreatment costs, treatment costs, adverse event costs, follow-up costs, subsequent allogeneic hematopoietic stem cell transplantation costs, and terminal care costs. Incremental cost-effectiveness ratios (ICERs) per life-years (LYs) gained and ICERs per quality-adjusted life-years (QALYs) gained were evaluated using a 2% discount rate, and a threshold of ¥7.5 million was used to assess cost-effectiveness. Deterministic and probabilistic sensitivity analyses were performed. The total LYs (discounted) for tisagenlecleucel, blinatumomab, and clofarabine combination treatment strategies were 13.3, 4.0, and 2.7 years, respectively; the corresponding QALYs were 11.6, 3.1, and 2.1 years, respectively. The ICERs per QALY gained for tisagenlecleucel were ¥2,035,071 versus blinatumomab and ¥2,644,702 versus clofarabine combination therapy. Extensive sensitivity analyses supported the findings. Tisagenlecleucel is a cost-effective treatment strategy for pediatric and young adult patients with r/r B-ALL from a Japanese public healthcare payer's perspective.

Treatments for children and adolescents with AML

In recent decades, survival rates for childhood acute myeloid leukemia have remarkably improved, owing to chemotherapy intensification, allogeneic hematopoietic stem cell transplantation, and improved supportive care. Furthermore, treatment protocols have evolved and are currently better matched to prognostic factors and treatment responses. Recently, new molecular prognostic factors were discovered via leukemia genomic studies. Moreover, new tumor subtypes with independent gene expression profiles have been characterized. To broaden the therapeutic options for patients with poor prognoses, therapies that target specific candidate mutations are being identified. Additionally, new drugs are undergoing clinical trials, and immunotherapy is attracting significant interest as a treatment option for recurrent or refractory childhood acute myeloid leukemia.

CAR T-cell product performance in haematological malignancies before and after marketing authorisation

Chimeric antigen receptor (CAR) T cells represent a potent new approach to treat haematological malignancies. Two CAR T-cell therapies, tisagenlecleucel and axicabtagene ciloleucel, have been approved in Europe and the USA, as well as several other countries, for the treatment of leukaemia and lymphoma. These approvals marked a major milestone in the field of cell and gene therapies. However, the clinical development and regulatory evaluation of these innovative therapies faced several challenges that are considered important lessons learned for future similar products. Here, we examine the products' non-clinical and clinical data packages to outline the challenges encountered during the regulatory evaluation process in Europe, and to provide an update on their performance after authorisation.

Tisagenlecleucel versus historical standard therapies for pediatric relapsed/refractory acute lymphoblastic leukemia

Aim: We compared outcomes from a single-arm study of tisagenlecleucel with standard of care (SOC) regimens in pediatric and young adult patients with relapsed/refractory acute lymphoblastic leukemia (ALL). Methods: The analysis included one tisagenlecleucel study, one blinatumomab study, one clofarabine monotherapy study, three studies of clofarabine combination regimens and two studies of other salvage chemotherapy. Matching-adjusted indirect comparison analyses were conducted. Results: After adjusting for baseline characteristics, tisagenlecleucel was associated with significantly prolonged overall survival compared with blinatumomab (hazard ratio [95% CI], 0.32 [0.16-0.64]); clofarabine monotherapy (0.24 [0.13-0.42]); clofarabine combination regimens (0.26 [0.15-0.45]); two salvage therapies (0.15 [0.09-0.25] and 0.27 [0.15-0.49]). Conclusion: The analysis demonstrated tisagenlecleucel was associated with substantially greater survival benefit versus all SOC regimens.

Optimization of a clofarabine-based drug combination regimen for the preclinical evaluation of pediatric acute lymphoblastic leukemia

BACKGROUND

The aim of this study was to improve the predictive power of patient-derived xenografts (PDXs, also known as mouse avatars) to more accurately reflect outcomes of clofarabine-based treatment in pediatric acute lymphoblastic leukemia (ALL) patients.

PROCEDURE

Pharmacokinetic (PK) studies were conducted using clofarabine at 3.5 to 15 mg/kg in mice. PDXs were established from relapsed/refractory ALL patients who exhibited good or poor responses to clofarabine. PDX engraftment and response to clofarabine (either as a single agent or in combinations) were assessed based on stringent objective response measures modeled after the clinical setting.

RESULTS

In naïve immune-deficient NSG mice, we determined that a clofarabine dose of 3.5 mg/kg resulted in systemic exposures equivalent to those achieved in pediatric ALL patients treated with clofarabine-based regimens. This dose was markedly lower than the doses of clofarabine used in previously reported preclinical studies (typically 30-60 mg/kg) and, when scheduled consistent with the clinical regimen (daily × 5), resulted in 34-fold lower clofarabine exposures. Using a well-tolerated clofarabine/etoposide/cyclophosphamide combination regimen, we then found that the responses of PDXs better reflected the clinical responses of the patients from whom the PDXs were derived.

CONCLUSIONS

This study has identified an in vivo clofarabine treatment regimen that reflects the clinical responses of relapsed/refractory pediatric ALL patients. This regimen could be used prospectively to identify patients who might benefit from clofarabine-based treatment. Our findings are an important step toward individualizing prospective patient selection for the use of clofarabine in relapsed/refractory pediatric ALL patients and highlight the need for detailed PK evaluation in murine PDX models.

"Feasible and effective administration of Bortezomib with Rituximab in children with relapsed/resistant B-cell precursor acute lymphoblastic leukemia (BCP-ALL): A step toward the first line"

Despite a high cure rate in childhood BCP-ALL, 20% of children still presents with relapse, mostly due to a persistent leukemic clone during the first-line treatment. In this context, obtaining a molecular remission is crucial for reaching a successful allogeneic hematopoietic stem cell transplantation. Bortezomib was effectively administered to children with resistant/relapsed (r/r) BCP-ALL. Moreover, high risk ALL is characterized by the increasing expression of CD20. For the first time we reported two children with r/r BCP-ALL who received a treatment schema including Bortezomib and Rituximab, achieving morphological and molecular remission. Children with high risk features, such as persistent minimal residual disease during induction, will benefit from this combination. Is it time to move toward the first line?

Cost-Effectiveness of Chimeric Antigen Receptor T-Cell Therapy in Pediatric Relapsed/Refractory B-Cell Acute Lymphoblastic Leukemia

BACKGROUND

Chimeric antigen receptor T-cell (CAR-T) therapy is a promising new class of cancer therapy but has a high up-front cost. We evaluated the cost-effectiveness of CAR-T therapy among pediatric patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL).

METHODS

We built a microsimulation model for pediatric patients with relapsed/refractory B-ALL receiving either CAR-T therapy or standard of care. Outcomes included costs, quality of life (health utility), complications, and survival. We measured cost-effectiveness with the incremental cost-effectiveness ratio (ICER), with ICERs under $100 000 per quality-adjusted life-year (QALY) considered cost effective. One-way and probabilistic sensitivity analyses were used to test model uncertainty.

RESULTS

Compared to standard of care, CAR-T therapy increased overall cost by $528 200 and improved effectiveness by 8.18 QALYs, resulting in an ICER of $64 600/QALY. The model was sensitive to assumptions about long-term CAR-T survival, the complete remission rate of CAR-T patients, and the health utility of long-term survivors. The base model assumed a 76.0% one-year survival with CAR-T, although if this decreased to 57.8%, then CAR-T was no longer cost effective. If the complete remission rate of CAR-T recipients decreased from 81% to 56.2%, or if the health utility of disease-free survivors decreased from 0.94 to 0.66, then CAR-T was no longer cost effective. Probabilistic sensitivity analysis found that CAR-T was cost effective in 94.8% of iterations at a willingness to pay of $100 000/QALY.

CONCLUSION

CAR-T therapy may represent a cost-effective option for pediatric relapsed/refractory B-ALL, although longer follow-up of CAR-T survivors is required to confirm validity of these findings.

FLAG/FLAG-IDA regimen for children with relapsed/refractory acute leukemia in the era of targeted novel therapies

BACKGROUND

Outcomes of relapsed/refractory childhood acute leukemia remain poor. We analyzed the safety/efficacy of fludarabine, cytarabine, and granulocyte colony stimulating factor, with/without idarubicin (FLAG ± IDA) as salvage therapy compared with recent published results of novel therapies.

METHODS

This retrospective study included children aged 1 to 15 years with relapsed/refractory acute leukemia who received FLAG ± IDA salvage therapy from January 2000 to December 2014. Patients with infant leukemia, mixed lineage leukemia, Philadelphia-positive acute leukemia, or secondary leukemia were excluded.

RESULT

Fifty patients were identified: 25 with acute lymphoblastic leukemia and 25 with acute myeloid leukemia. The median age at initiation of FLAG ± IDA was seven years. Site of relapse was the bone marrow in 29, isolated central nervous system in 11, and combined in 10 patients. FLAG ± IDA was used after first relapse in 68% and after multiple relapses in 32%. Complete remission was achieved in 34 (68%) patients. No variables predictive of complete remission were identified. Grade 3 or greater toxicity was observed in 96% and 6% died from toxicity. Toxicities included hematologic toxicity (96%), infection (52%), and enterocolitis (28%). Twenty-four of 50 (48%) patients achieved a sustained complete remission and survived to bone marrow transplantation. The five-year overall survival was 23.9% ± 6.9%. Patients achieving second complete remission and patients proceeding to bone marrow transplantation following second complete remission demonstrated significantly improved overall survival (p = 0.001).

CONCLUSION

Despite a 68% complete remission rate using FLAG ± IDA, only 48% of patients survived to bone marrow transplantation. The regimen was associated with 96% toxicity and only one in four patients was alive at five years. This underscores the need to find more effective lower toxicity salvage regimens.

Cost Effectiveness of Chimeric Antigen Receptor T-Cell Therapy in Relapsed or Refractory Pediatric B-Cell Acute Lymphoblastic Leukemia

PURPOSE

The anti-CD19 chimeric antigen receptor T-cell therapy tisagenlecleucel was recently approved to treat relapsed or refractory pediatric acute lymphoblastic leukemia. With a one-time infusion cost of $475,000, tisagenlecleucel is currently the most expensive oncologic therapy. We aimed to determine whether tisagenlecleucel is cost effective compared with currently available treatments.

METHODS

Markov modeling was used to evaluate tisagenlecleucel in pediatric relapsed or refractory acute lymphoblastic leukemia from a US health payer perspective over a lifetime horizon. The model was informed by recent multicenter, single-arm clinical trials. Tisagenlecleucel (under a range of plausible long-term effectiveness) was compared with blinatumomab, clofarabine combination therapy (clofarabine, etoposide, and cyclophosphamide), and clofarabine monotherapy. Scenario and probabilistic sensitivity analyses were used to explore uncertainty. Main outcomes were life-years, discounted lifetime costs, discounted quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (3% discount rate).

RESULTS

With an assumption of a 40% 5-year relapse-free survival rate, tisagenlecleucel increased life expectancies by 12.1 years and cost $61,000/QALY gained. However, at a 20% 5-year relapse-free survival rate, life-expectancies were more modest (3.8 years) and expensive ($151,000/QALY gained). At a 0% 5-year relapse-free survival rate and with use as a bridge to transplant, tisagenlecleucel increased life expectancies by 5.7 years and cost $184,000/QALY gained. Reduction of the price of tisagenlecleucel to $200,000 or $350,000 would allow it to meet a $100,000/QALY or $150,000/QALY willingness-to-pay threshold in all scenarios.

CONCLUSION

The long-term effectiveness of tisagenlecleucel is a critical but uncertain determinant of its cost effectiveness. At its current price, tisagenlecleucel represents reasonable value if it can keep a substantial fraction of patients in remission without transplantation; however, if all patients ultimately require a transplantation to remain in remission, it will not be cost effective at generally accepted thresholds. Price reductions would favorably influence cost effectiveness even if long-term clinical outcomes are modest.

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.

Severe Hypercalcemia in a Child With Acute Lymphoblastic Leukemia Relapse: Successful Management With Combination of Calcitonin and Bisphosphonate

Hypercalcemia is a rare complication of hematological malignancy in children. An 8-year-old girl with CALLA (+) Pre-B-cell ALL developed hypercalcemia during bone marrow relapse. She had nausea, vomiting, leg pain, polyuria, polydipsia, and muscle weakness. At the time of relapse, the ionized calcium level was 1.99 mmol/L. Rehydration with 0.9% saline and furosemide and methylprednisolone (MP) treatment were used for the treatment of hypercalcemia. The serum ionized calcium level increased to 2.2 mmol/L despite hydration, furosemide, and MP treatment. Then, a single-dose pamidronate (1 mg/kg/dose) was administered. Despite pamidronate treatment, the calcium level continued to rise. Next, calcitonin at a dose of 8 IU/kg/dose, 4 doses per day, was added to the treatment. After commencement of calcitonin treatment, her ionized calcium level decreased to normal reference ranges. In conclusion, because of the postponed effect of bisphosphonate treatment, pamidronate and calcitonin combination is an effective treatment option in the early resolution of malignancy-related hypercalcemia.

A Phase I Study of Clofarabine With Multiagent Chemotherapy in Childhood High Risk Relapse of Acute Lymphoblastic Leukemia (VANDEVOL Study of the French SFCE Acute Leukemia Committee)

BACKGROUND

Current outcome of very early relapse of acute lymphoblastic leukemia (ALL) in children remains poor. As a single agent, clofarabine provided a response rate of 26% in childhood ALL second relapse and, in combination with cyclophosphamide and etoposide, a 44% complete remission and complete remission without platelet recovery (CR+CRp) rate. Further multi-drug combinations need to be investigated. We used the VANDA regimen as a template, cytarabine being replaced by clofarabine.

PATIENTS AND METHODS

A phase I study combining escalating doses of clofarabine (25% increments from 20 to 40 mg/m(2)/d) with fixed doses of mitoxantrone, etoposide, asparaginase, and dexamethasone was undertaken in children presenting with very early or second or post-transplant ALL relapse.

RESULTS

Twenty patients were enrolled, 19 were evaluable. Four patients had previously been allografted. Dose-limiting toxicity (DLT) appeared at dose level 3 (32 mg/m(2)), one out of six patients experienced a liver DLT. At dose level 4 (40 mg/m(2)), four DLT occurred (two fungal infection and two liver DLT). The maximum tolerated dose (MTD) of clofarabine was thus determined to be 32 mg/m(2). There was no toxic death. Eleven (57.9%) patients achieved a CR. Six patients proceeded to allogeneic stem cell transplantation.

CONCLUSION

Clofarabine MTD was 32 mg/m(2)/d in this combination which appeared feasible and effective in this population.

Refractory acute lymphoblastic leukemia in Chinese children: bridging to stem cell transplantation with clofarabine, cyclophosphamide and etoposide

Refractory or relapsed acute lymphoblastic leukemia (r/r ALL) represents the leading cause of cancer mortality in children. Clofarabine is effective in inducing remission thus enabling bridging to hematopoietic stem cell transplantation (HSCT). We report the results in treating Hong Kong Chinese pediatric patients with r/rALL by clofarabine/cyclophosphamide/etoposide (CLO-218) combination therapy. A retrospective review of patients treated between January 2009 and December 2014 in the two tertiary referral pediatric oncology units in Hong Kong. Thirteen patients were identified. All were Chinese and seven were male. Median age at clofarabine treatment was 8 years and the median duration of follow-up was 10 months. Nine patients had B-ALL and four had T-ALL. All were refractory to the preceding regimen(s). The median number of prior treatment regimens was 2; two patients had previous HSCT. Complete remission (CR) was achieved in five patients, Complete remission with incomplete counts (CRi) in two, PR in two, and non-remission (NR) in two. All four patients with T-ALL responded with three patients achieving CR. Eight out of nine patients who responded could be bridged to HSCT. Among those who were transplanted, four remained alive and in remission, three relapsed post-HSCT, and one died from transplant-related mortality. Treatment toxicities were common including febrile neutropenia in all subjects and culture-proven bacteremia in five patients. Hepatotoxicity was mild and reversible with no case of veno-occlusive disease. The clofarabine-based regimen is a promising strategy to induce disease remission in r/rALL and bridge to HSCT. Septic complications are, however, frequent necessitating prompt management with adequate supportive care in specialized centers.

Potentiation of temozolomide antitumor effect by purine receptor ligands able to restrain the in vitro growth of human glioblastoma stem cells

Glioblastoma multiforme (GBM), the most common and aggressive brain tumor in humans, comprises a population of stem-like cells (GSCs) that are currently investigated as potential target for GBM therapy. Here, we used GSCs isolated from three different GBM surgical specimens to examine the antitumor activity of purines. Cultured GSCs expressed either metabotropic adenosine P1 and ATP P2Y receptors or ionotropic P2X7 receptors. GSC exposure for 48 h to 10-150 μM ATP, P2R ligand, or to ADPβS or MRS2365, P2Y1R agonists, enhanced cell expansion. This effect was counteracted by the PY1R antagonist MRS2500. In contrast, 48-h treatment with higher doses of ATP or UTP, which binds to P2Y2/4R, or 2'(3')-O-(4-benzoylbenzoyl)-ATP (Bz-ATP), P2X7R agonist, decreased GSC proliferation. Such a reduction was due to apoptotic or necrotic cell death but mostly to growth arrest. Accordingly, cell regrowth and secondary neurosphere formation were observed 2 weeks after the end of treatment. Suramin, nonselective P2R antagonist, MRS1220 or AZ11645373, selective A3R or P2X7R antagonists, respectively, counteracted ATP antiproliferative effects. AZ11645373 also abolished the inhibitory effect of Bz-ATP low doses on GSC growth. These findings provide important clues on the anticancer potential of ligands for A3R, P2Y1R, and P2X7R, which are involved in the GSC growth control. Interestingly, ATP and BzATP potentiated the cytotoxicity of temozolomide (TMZ), currently used for GBM therapy, enabling it to cause a greater and long-lasting inhibitory effect on GSC duplication when readded to cells previously treated with purine nucleotides plus TMZ. These are the first findings identifying purine nucleotides as able to enhance TMZ antitumor efficacy and might have an immediate translational impact.

Outcome of children with relapsed acute myeloid leukemia following initial therapy under the AML99 protocol

The outcomes of children with relapsed acute myeloid leukemia (AML) are known to be poor, but remain obscure. We retrospectively analyzed 71 patients who had relapsed following first-line treatment under the AML99 protocol. We investigated the time and site of recurrence, response to re-induction therapy, and performance of hematopoietic stem cell transplantation (HSCT) in relapsed cases, and performed a multivariate analysis to identify prognostic factors. The 5-year overall-survival (OS) rate after relapse was 37 %. Of 71 patients, three died without any anti-leukemic therapy and two underwent allogeneic HSCT. The remaining 66 patients received re-induction chemotherapy, and 33 (50 %) achieved second CR (CR2). Twenty-two of 25 (88 %) late relapse patients and 11 of 41 (27 %) early relapse patients achieved CR2 (P < 0.001). Twenty-nine CR2 cases and 35 non-CR2 cases underwent allogeneic HSCT. The 5-year OS rate was significantly higher in patients who underwent HSCT in CR2 than those in non-CR2 (66 vs. 17 %, P < 0.000001). Multivariate analysis indicated that early relapse (P < 0.05) and the positivity of the FMS-like tyrosine kinase 3--internal tandem duplication (P < 0.05) were adverse prognostic factors for survival. In conclusion, the etiology of relapsed pediatric AML needs to be elucidated and effective chemotherapy should be administered to obtain CR2.

Relapsed and refractory pediatric acute myeloid leukemia: current and emerging treatments

Survival rates for children with acute myeloid leukemia (AML) exceed 60 % when modern, intensified chemotherapeutic regimens and enhanced supportive care measures are employed. Despite well-recognized improvements in outcomes, primary refractory or relapsed pediatric AML yields significant morbidity and mortality, and improved understanding of this obstinate population along with refined treatment protocols are urgently needed. Although a significant number of patients with refractory or relapsed disease will achieve remission, long-term survival rates remain poor, and efforts to identify therapies which will improve OS are under continuous investigation. The current fundamental goal of such investigation is the achievement of as complete a remission as possible without dose-limiting toxicities, and the progression to hematopoietic stem cell transplantation thereafter. In this review the scope of the problem of relapsed and refractory AML as well as current and emerging chemotherapy options will be discussed.

Phase II trial of clofarabine with topotecan, vinorelbine, and thiotepa in pediatric patients with relapsed or refractory acute leukemia

BACKGROUND

Outcomes for children with relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL) and acute myelogenous leukemia (AML) are dismal. In an effort to improve outcomes, we performed a phase I/II study of a novel clofarabine based combination regimen called TVTC. Herein, we report the response rates of patients in the phase II portion of the study.

PROCEDURE

Seventeen patients with R/R ALL, AML, or biphenotypic leukemia were enrolled. Sixteen patients were evaluable for response. Patients were treated at the maximum tolerated dose (MTD) from the phase I portion of the study (clofarabine 40 mg/m(2) /day IV × 5 days, topotecan 1 mg/m(2) /day IV continuous infusion × 5 days, vinorelbine 20 mg/m(2) /week IV × 3 weeks, thiotepa 15 mg/m(2)/day IV × 1 day). The primary endpoint was overall response rate (ORR), defined as CR or CR without platelet recovery (CRp).

RESULTS

The ORR was 69% (10 CR, 1 CRp). Among the 11 responders, 9 (82%) proceeded to hematopoietic stem cell transplantation. The most common grade 3+ non-hematologic toxicities were febrile neutropenia (82%) and transient transaminase elevation (47%).

CONCLUSIONS

TVTC demonstrates significant activity in patients with R/R acute leukemia. The activity in R/R AML patients was very encouraging, with 8 of 12 (67%) patients achieving a CR/CRp. Patients with high risk de novo AML may benefit from incorporation of TVTC therapy into frontline treatment regimens. This regimen warrants further exploration in a larger cohort of patients with R/R leukemia.

Pediatric relapsed or refractory leukemia: new pharmacotherapeutic developments and future directions

Over the past 50 years, numerous advances in treatment have produced dramatic increases in the cure rates of pediatric leukemias. Despite this progress, the majority of children with relapsed leukemia are not expected to survive. With current chemotherapy regimens, approximately 15 % of children with acute lymphoblastic leukemia and 45 % of children with acute myeloid leukemia will have refractory disease or experience a relapse. Advances in the treatment of pediatric relapsed leukemia have not mirrored the successes of upfront therapy, and newer treatments are desperately needed in order to improve survival in these challenging patients. Recent improvements in our knowledge of cancer biology have revealed an extensive number of targets that have the potential to be exploited for anticancer therapy. These advances have led to the development of a number of new treatments that are now being explored in children with relapsed or refractory leukemia. Novel agents seek to exploit the same molecular aberrations that contribute to leukemia development and resistance to therapy. Newer classes of drugs, including monoclonal antibodies, tyrosine kinase inhibitors and epigenetic modifiers are transforming the treatment of patients who are not cured with conventional therapies. As the side effects of many new agents are distinct from those seen with conventional chemotherapy, these treatments are often explored in combination with each other or combined with conventional treatment regimens. This review discusses the biological rationale for the most promising new agents and the results of recent studies conducted in pediatric patients with relapsed leukemia.

Older and new purine nucleoside analogs for patients with acute leukemias

Purine nucleoside analogs (PNAs) compose a class of cytotoxic drugs that have played an important role in the treatment of hematological neoplasms, especially lymphoid and myeloid malignancies. All PNA drugs have a chemical structure similar to adenosine or guanosine, and they have similar mechanisms of action. They have many intracellular targets: they act as antimetabolites, competing with natural nucleosides during DNA or RNA synthesis, and as inhibitors of key cell enzymes. In contrast to other antineoplastic drugs, PNAs act cytotoxically, both in the mitotic and quiescent cell cycle phases. In the last few years, three PNAs have been approved for the treatment of lymphoid malignancies and other hematological disorders: 2-chlorodeoxyadenosine (2-CdA), fludarabine and pentostatin. 2-CdA and fludarabine are also active in the treatment of acute myeloid leukemia (AML). These drugs, in combination with cytarabine and other agents, are commonly used as salvage regimens in relapsed or refractory AML. Moreover, the addition of 2-CdA to the standard induction regimen is associated with an increased rate of complete remission and improved survival of adult patients with AML. More recently three novel PNAs have been synthesized and introduced into clinical trials: clofarabine, nelarabine and forodesine. Clofarabine is the most promising PNA in current clinical trials in pediatric and adult patients with acute leukemias. Nelarabine is more cytotoxic in T-lineage than in B-lineage leukemias. Clofarabine and nelarabine have been approved for the treatment of refractory patients with acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma. Clofarabine is also an active drug in AML treatment when administered either alone or in combination regimens as front-line treatment and in relapsed or refractory patients. Unlike other PNA, forodesine is not incorporated into DNA but displays a highly selective purine nucleoside phosphorylase inhibitory action. Forodesine is undergoing clinical trials for the treatment of T-cell malignancies, including T-cell ALL. This article summarizes recent achievements in the mechanism of action, pharmacological properties and clinical activity and toxicity of PNAs, as well as their emerging role in lymphoid and myeloid acute leukemias.

High-dose etoposide in allogeneic stem cell transplantation

The anti-leukemic effect of etoposide is well documented. High-dose etoposide 60 mg/kg in combination with fractionated total body irradiation (TBI), usually single fractions of 1.2 Gy up to a total of 13.2 Gy, is used as conditioning therapy for allogeneic stem cell transplantation. Most studies of this conditioning regimen have included patients with acute leukemia receiving bone marrow or mobilized stem cell grafts derived from family or matched unrelated donors, and the treatment is then effective even in patients with high-risk disease. The most common adverse effects are fever with hypotension and rash, nausea and vomiting, sialoadenitis, neuropathy and metabolic acidosis. A small minority of patients develop severe allergic reactions. Etoposide has also been tested in a wide range of combination regimens, but for many of these combinations, relatively few patients are included, and some combinations have only been tested in patients who have undergone autologous transplants. However, the general conclusion is that many of these combinations are effective in patients with high-risk malignancies and the toxicity often seems acceptable. Thus, etoposide-based conditioning therapy should be further evaluated in patients having allogeneic transplants, but randomized trials are needed and the design of future trials should be based on the well-characterized TBI + high-dose etoposide regimen.