Gemtuzumab ozogamicin: first clinical experiences in children with relapsed/refractory acute myeloid leukemia treated on compassionate-use basis

Pediatric acute myeloid leukemia - novel approaches

PURPOSE OF REVIEW

Despite higher remission and survival rates than observed in adults, children with acute myeloid leukemia (AML) still suffer unacceptably high rates of treatment failure and late toxicities. Ongoing work aims to improve these long-term outcomes through improvements in the utilization of current therapies, the incorporation of novel chemotherapy agents, and improved use of current or novel cellular and immunotherapeutic approaches. In this review, we highlight recent advances and contextualize them within this evolving landscape.

RECENT FINDINGS

Novel agents such as the B-cell lymphoma 2 inhibitor venetoclax and the menin inhibitors have shown promising results with implications for large portions of the pediatric AML population. Older agents are being used in novel combinations (e.g. gemtuzumab ozogamicin) or are expanding into pediatrics after longer use in adults (e.g. Fms-like tyrosine kinase 3 inhibitors). Finally, immunotherapeutic approaches offer new options for patients with high-risk or relapsed disease.

SUMMARY

Recent findings have altered the landscape of pediatric AML therapy with exciting immediate and long-term implications. Ongoing studies may soon define this as standard as well. After many years in which few new therapies have become available for children with AML, recent and upcoming advances may soon dramatically alter the therapeutic landscape.

Gemtuzumab ozogamicin for relapsed or primary refractory acute myeloid leukemia in children-the Polish Pediatric Leukemia and Lymphoma Study Group experience

Background

Gemtuzumab ozogamicin (GO), one of the first targeted drugs used in oncology, consists of an anti-cluster of differentiation 33 (CD33) monoclonal antibody bound to a derivative of cytotoxic calicheamicin. After the drug withdrawn in 2010 due to a significantly higher rate of early deaths, GO regained approval in 2017 for the treatment of newly diagnosed, refractory, or relapsed acute myeloid leukemia (AML) in adults and children over 15 years of age. The objective of the study was a retrospective analysis of clinical characteristics, treatment outcomes, and GO toxicity profile in children with primary refractory or relapsed (R/R) AML treated in Poland from 2008 to 2022.

Methods

Data were collected through the Polish Registry of Acute Myeloid Leukemia. From January 2008 to December 2022, 35 children with R/R AML were treated with GO in seven centers of the Polish Pediatric Leukemia and Lymphoma Study Group.

Results

Most of the children (30 of 35) received only one GO cycle in combination with various chemotherapy cycles (IDA-FLA, DOXO-FLA, FLA, FLAG, and others). Eighteen children (51%) achieved complete remission (CR), 14 did not respond to treatment, and three progressed. GO therapy was followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT) in 18 children in CR. The 5-year overall survival (OS) after GO therapy was 37.1% ± 8.7% for the total cohort. There was a trend toward a superior outcome in patients with strong expression of CD33 expression (over 50% positive cells) compared with that in patients with lower expression of CD33 (OS, 41.2% ± 11.9% versus 27.8% ± 13.2%; p = 0.5; 5-year event-free survival, 35.4% ± 11.6% versus 25.7% ± 12.3%; p = 0.5, respectively). Children under 15 years have better outcome (OS, 34.9% ± 10.4% versus 30% ± 14.5%, p = 0.3). The most common adverse events were bone marrow aplasia, fever of unknown origin, infections, and elevated liver enzyme elevation. Sinusoidal obstruction syndrome occurred in two children.

Conclusions

The use of GO in severely pretreated children, including those under 15 years of age, with previous failure of AML treatment is a feasible and effective bridging therapy to allo-HSCT with an acceptable toxicity profile.

Global Impact of Monoclonal Antibodies (mAbs) in Children: A Focus on Anti-GD2

Monoclonal antibodies (mAbs), as the name implies, are clonal antibodies that bind to the same antigen. mAbs are broadly used as diagnostic or therapeutic tools for neoplasms, autoimmune diseases, allergic conditions, and infections. Although most mAbs are approved for treating adult cancers, few are applicable to childhood malignancies, limited mostly to hematological cancers. As for solid tumors, only anti-disialoganglioside (GD2) mAbs are approved specifically for neuroblastoma. Inequities of drug access have continued, affecting most therapeutic mAbs globally. To understand these challenges, a deeper dive into the complex transition from basic research to the clinic, or between marketing and regulatory agencies, is timely. This review focuses on current mAbs approved or under investigation in pediatric cancer, with special attention on solid tumors and anti-GD2 mAbs, and the hurdles that limit their broad global access. Beyond understanding the mechanisms of drug resistance, the continual discovery of next generation drugs safer for children and easier to administer, the discovery of predictive biomarkers to avoid futility should ease the acceptance by patient, health care professionals and regulatory agencies, in order to expand clinical utility. With a better integration into the multimodal treatment for each disease, protocols that align with the regional clinical practice should also improve acceptance and cost-effectiveness. Communication and collaboration between academic institutions, pharmaceutical companies, and regulatory agencies should help to ensure accessible, affordable, and sustainable health care for all.

Infectious Complications of Targeted Therapies in Children with Leukemias and Lymphomas

Simple Summary

Targeted therapies in children with hematological malignancies moderate the effects of cytotoxic therapy, thus improving survival rates. They have emerged over the last decade and are used in combination with or after the failure of conventional chemotherapy and as bridging therapy prior to hematopoietic stem cell transplantation (HSCT). Nowadays, there is a growing interest in their efficacy and safety in pediatric patients with refractory or relapsed disease. The compromised immune system, even prior to therapy, requires prompt monitoring and treatment. In children with hematological malignancies, targeted therapies are associated with a comparable incidence of infectious complications to adults. The exact impact of these agents that have different mechanisms of action and are used after conventional chemotherapy or HSCT is difficult to ascertain. Clinicians should be cautious of severe infections after the use of targeted therapies, especially when used in combination with chemotherapy.

Abstract

The aim of this review is to highlight mechanisms of immunosuppression for each agent, along with pooled analyses of infectious complications from the available medical literature. Rituximab confers no increase in grade ≥3 infectious risks, except in the case of patients with advanced-stage non-Hodgkin lymphoma. Gemtuzumab ozogamicin links with high rates of grade ≥3 infections which, however, are comparable with historical cohorts. Pembrolizumab exhibits a favorable safety profile in terms of severe infections. Despite high rates of hypogammaglobulinemia (HGG) with blinatumomab, low-grade ≥3 infection rates were observed, especially in the post-reinduction therapy of relapsed B-acute lymphoblastic leukemia. Imatinib and nilotinib are generally devoid of severe infectious complications, but dasatinib may slightly increase the risk of opportunistic infections. Data on crizotinib and pan-Trk inhibitors entrectinib and larotrectinib are limited. CAR T-cell therapy with tisagenlecleucel is associated with grade ≥3 infections in children and is linked with HGG and the emergence of immune-related adverse events. Off-label therapies inotuzumab ozogamicin, brentuximab vedotin, and venetoclax demonstrate low rates of treatment-related grade ≥3 infections, while the addition of bortezomib to standard chemotherapy in T-cell malignancies seems to decrease the infection risk during induction. Prophylaxis, immune reconstitution, and vaccinations for each targeted agent are discussed, along with comparisons to adult studies.

Single-dose (4.5 mg/m2 ) gemtuzumab ozogamicin in combination with fludarabine, cytarabine and anthracycline as reinduction therapy in relapsed or refractory paediatric acute myeloid leukaemia

Despite major therapeutic improvements, children with relapsed/refractory Acute Myeloid Leukaemia still have poor outcomes and overall survival does not exceed 40%. New treatments are required to improve their outcome; Gemtuzumab ozogamicin (GO), an anti-CD33 immunoconjugate antibody, is a potent cytotoxic agent whose efficacy has been demonstrated mainly in adults. The main objective of this retrospective multicentre study was to assess the outcome of children treated, between February 2008 and August 2019, with GO at a single 4.5 mg/m² dose, in combination with Fludarabine, Cytarabine and antssshracyclines, in context of a first relapse (n = 26) or refractory disease (n = 3). The remission rate was 83% (24/29 children) and 20 children (69%) were allografted. With a median follow-up of 1.2 years (range: 0.1-8), the overall survival was 49% (CI95% = 33; 72). Most common adverse event was febrile neutropenia with microbiological identification in 55% of cases. Veno-occlusive disease occurred in 6 patients (21%), of which 5 subvened after bone marrow transplantation, and resolved within 2-32 days (median 10.5 days). Administration of GO in combination with FLA-anthracyclines chemotherapy appears to be a good reinduction regimen for relapsed or refractory AML with a good safety profile. These results warrant larger prospective study.

Therapeutic Targeting of Acute Myeloid Leukemia by Gemtuzumab Ozogamicin

Acute myeloid leukemia (AML) is a complex hematological malignancy characterized by genetic and clinical heterogeneity and high mortality. Despite the recent introduction of novel pharmaceutical agents in hemato-oncology, few advancements have been made in AML for decades. In the last years, the therapeutic options have rapidly changed, with the approval of innovative compounds that provide new opportunities, together with new challenges for clinicians: among them, on 1 September, 2017 the Food and Drug Administration granted approval for Gemtuzumab Ozogamicin (GO) in combination with daunorubicin and cytarabine for the treatment of adult patients affected by newly diagnosed CD33⁺ AML. Benefits of GO-based regimens were also reported in the pre- and post-transplantation settings. Moreover, several biomarkers of GO response have been suggested, including expression of CD33 and multidrug resistance genes, cytogenetic and molecular profiles, minimal residual disease and stemness signatures. Among them, elevated CD33 expression on blast cells and non-adverse cytogenetic or molecular risk represent largely validated predictors of good response.

Redirecting the Immune Microenvironment in Acute Myeloid Leukemia

Simple Summary

Despite remarkable progress in the outcome of childhood acute myeloid leukemia (AML), risk of relapse and refractory diseases remains high. Treatment of the chemo-refractory disease is restricted by dose-limiting therapy-related toxicities which necessitate alternative tolerable efficient therapeutic modalities. By disrupting its immune environment, leukemic blasts are known to gain the ability to evade immune surveillance and promote disease progression; therefore, many efforts have been made to redirect the immune system against malignant blasts. Deeper knowledge about immunologic alterations has paved the way to the discovery and development of novel targeted therapeutic concepts, which specifically override the immune evasion mechanisms to eradicate leukemic blasts. Herein, we review innovative immunotherapeutic strategies and their mechanisms of action in pediatric AML.

Abstract

Acute myeloid leukemia is a life-threatening malignant disorder arising in a complex and dysregulated microenvironment that, in part, promotes the leukemogenesis. Treatment of relapsed and refractory AML, despite the current overall success rates in management of pediatric AML, remains a challenge with limited options considering the heavy but unsuccessful pretreatments in these patients. For relapsed/refractory (R/R) patients, hematopoietic stem cell transplantation (HSCT) following ablative chemotherapy presents the only opportunity to cure AML. Even though in some cases immune-mediated graft-versus-leukemia (GvL) effect has been proven to efficiently eradicate leukemic blasts, the immune- and chemotherapy-related toxicities and adverse effects considerably restrict the feasibility and therapeutic power. Thus, immunotherapy presents a potent tool against acute leukemia but needs to be engineered to function more specifically and with decreased toxicity. To identify innovative immunotherapeutic approaches, sound knowledge concerning immune-evasive strategies of AML blasts and the clinical impact of an immune-privileged microenvironment is indispensable. Based on our knowledge to date, several promising immunotherapies are under clinical evaluation and further innovative approaches are on their way. In this review, we first focus on immunological dysregulations contributing to leukemogenesis and progression in AML. Second, we highlight the most promising therapeutic targets for redirecting the leukemic immunosuppressive microenvironment into a highly immunogenic environment again capable of anti-leukemic immune surveillance.

Invasive Fungal Diseases in Children with Hematological Malignancies Treated with Therapies That Target Cell Surface Antigens: Monoclonal Antibodies, Immune Checkpoint Inhibitors and CAR T-Cell Therapies

Since 1985 when the first agent targeting antigens on the surface of lymphocytes was approved (muromonab-CD3), a multitude of such therapies have been used in children with hematologic malignancies. A detailed literature review until January 2021 was conducted regarding pediatric patient populations treated with agents that target CD2 (alefacept), CD3 (bispecific T-cell engager [BiTE] blinatumomab), CD19 (denintuzumab mafodotin, B43, BiTEs blinatumomab and DT2219ARL, the immunotoxin combotox, and chimeric antigen receptor [CAR] T-cell therapies tisagenlecleucel and axicabtagene ciloleucel), CD20 (rituximab and biosimilars, 90Y-ibritumomab tiuxetan, ofatumumab, and obinutuzumab), CD22 (epratuzumab, inotuzumab ozogamicin, moxetumomab pasudotox, BiTE DT2219ARL, and the immunotoxin combotox), CD25 (basiliximab and inolimomab), CD30 (brentuximab vedotin and iratumumab), CD33 (gemtuzumab ozogamicin), CD38 (daratumumab and isatuximab), CD52 (alemtuzumab), CD66b (90Y-labelled BW 250/183), CD248 (ontuxizumab) and immune checkpoint inhibitors against CTLA-4 (CD152; abatacept, ipilimumab and tremelimumab) or with PD-1/PD-L1 blockade (CD279/CD274; atezolizumab, avelumab, camrelizumab, durvalumab, nivolumab and pembrolizumab). The aim of this narrative review is to describe treatment-related invasive fungal diseases (IFDs) of each category of agents. IFDs are very common in patients under blinatumomab, inotuzumab ozogamicin, basiliximab, gemtuzumab ozogamicin, alemtuzumab, and tisagenlecleucel and uncommon in patients treated with moxetumomab pasudotox, brentuximab vedotin, abatacept, ipilimumab, pembrolizumab and avelumab. Although this new era of precision medicine shows promising outcomes of targeted therapies in children with leukemia or lymphoma, the results of this review stress the necessity for ongoing surveillance and suggest the need for antifungal prophylaxis in cases where IFDs are very common complications.

Population Pharmacokinetics of Gemtuzumab Ozogamicin in Pediatric Patients with Relapsed or Refractory Acute Myeloid Leukemia

BACKGROUND AND OBJECTIVE

To date, the population pharmacokinetics (popPK) of gemtuzumab ozogamicin (GO), a CD33-directed antibody-drug conjugate consisting of hP67.6 antibody linked to N-acetyl gamma calicheamicin used in the treatment of acute myeloid leukemia (AML), has not been characterized in pediatric patients. This report describes the popPK of GO following intravenous administration in 29 pediatric patients aged ≤ 17 years with relapsed or refractory AML who were enrolled in the 0903A1-102-US phase I/II study.

METHODS

The pharmacokinetics (PK) of GO, as represented by total hP67.6 antibody, were described by a two-compartment model with two clearance components: a linear clearance (CL₁) and time-dependent clearance that includes a decay coefficient. The PK of unconjugated calicheamicin (UC; payload) were described by a two-compartment model with CL₁ and an input rate of formation based on antibody rate of elimination. Allometric scaling was included in both models, with baseline body weight as a fixed effect on CL₁ and central volume.

RESULTS AND CONCLUSIONS

PK parameters for hP67.6 and UC were not significantly affected by any of the available demographic factors and safety laboratory values tested as covariates (except baseline body weight). Simulations to compare GO dosing regimens (6, 7.5, and 9 mg/m² on days 1 and 15 versus, 3 mg/m² fractionated dosing on days 1, 4, and 7) were performed, showing that total antibody and UC trough concentrations were maintained at higher concentrations during treatment following the more frequent dosing than following the original regimen.

STUDY IDENTIFIER

0903A1-102-US.

The future of cellular immunotherapy for childhood leukemia

PURPOSE OF REVIEW

Exciting translational discoveries in recent years have brought realized promise of immunotherapy for children with high-risk leukemias. This review summarizes the current immunotherapeutic landscape with a focus on key clinical trials for patients with acute lymphoblastic leukemia or acute myeloid leukemia.

RECENT FINDINGS

Chemotherapy resistance remains a major barrier to cure in children with high-risk leukemias. Immunotherapy approaches have potential to overcome this resistance given alternative mechanisms of action. Based upon preclinical activity and/or success in adult patients, recent clinical trials have demonstrated safety and efficacy of various mAb, antibody-drug conjugate, bispecific T-cell-engaging antibody, natural killer cell, and chimeric antigen receptor-redirected T-cell immunotherapies for children with acute lymphoblastic leukemia or acute myeloid leukemia. Food and Drug Administration approval of several of these immunotherapies has increased the pediatric leukemia therapeutic portfolio and improved clinical outcomes for previously incurable patients.

SUMMARY

Several antibody-based or cellular immunotherapy modalities have demonstrated appreciable efficacy in children with relapsed or chemotherapy-refractory leukemia via early-phase clinical trials. Some studies have also identified critical biomarkers of treatment response and resistance that merit further investigation. Continued preclinical and clinical evaluation of novel immunotherapies is imperative to improve cure rates for children with high-risk leukemias.

Gemtuzumab ozogamicin in children with relapsed or refractory acute myeloid leukemia: a report by Berlin-Frankfurt-Münster study group

Despite intensified salvage treatments, children with relapsed/refractory acute myeloid leukemia (AML) have poor survival. We evaluated gemtuzumab ozogamicin (CD33-targeted drug) used on a compassionate basis in patients diagnosed from 1995 until 2014 within Acute Myeloid Leukemia Berlin-Frankfurt-Münster studies, and identified 76 patients (<18 years) with highly-advanced and pre-treated AML [refractory de novo acute myeloid leukemia (n=10), de novo AML refractory to relapse (1^st early: n=41; 1^st late: n=10; 2^nd or more: n=10), and secondary AML (n=5)]. At doses of 2.5–10 mg/m², gemtuzumab ozogamicin was administered in 1-4 cycles as single agent (47%), combined with cytarabine (47%), or others (6%). Most common grade 3/4 adverse events were infections or febrile neutropenia (78% of severe adverse events), infusion-related immunological reactions (6%), and gastrointestinal symptoms (5%). Three patients experienced veno-occlusive disease (one fatal due to exacerbation of a pre-existing cardiomyopathy). Sixty-four percent received subsequent hematopoietic stem cell transplantation. Probability of 4-year overall survival was 18±5% in all, 27±7% in patients with and 0% in patients without hematopoietic stem cell transplantation (P<0.0001). Administration of gemtuzumab ozogamicin on a patient-specific, compassionate use basis was frequently considered in our study group and proved to be effective for bridging children with very advanced AML to hematopoietic stem cell transplantation. Uniform prospective studies for these patients are urgently needed.

FDA Approval Summary: Mylotarg for Treatment of Patients with Relapsed or Refractory CD33-Positive Acute Myeloid Leukemia

On September 2, 2017, the U.S. Food and Drug Administration approved gemtuzumab ozogamicin (GO; Mylotarg; Pfizer, New York City, NY) for treatment of relapsed or refractory (R/R) CD33-positive acute myeloid leukemia (AML) in patients 2 years of age and older. GO is a CD33-directed antibody drug conjugate linked to the cytotoxic antibiotic calicheamicin. It originally received accelerated approval for treatment of older patients with relapsed CD33-positive AML in 2000, but it was withdrawn from the market in 2010 when the confirmatory trial failed to demonstrate clinical benefit among safety concerns, such as a higher rate of induction fatalities on the GO combination arm compared with chemotherapy alone. In addition, GO was associated with hepatic veno-occlusive disease (VOD), which has substantial morbidity and mortality. Pharmacokinetic analyses suggested a lower maximum concentration of GO would result in less VOD without affecting target saturation or efficacy. A meta-analysis across dose schedules of GO in patients with R/R AML showed that a lower-dose "fractionated" schedule of 3 mg/m² days 1, 4, and 7 was associated with less early mortality, hemorrhage, and VOD, without an apparent decrease in complete remission (CR) rate. MyloFrance 1 was a single-arm study evaluating response rates in patients with relapsed CD33-positive AML treated with the lower-dose fractionated GO regimen. The CR rate was 26% (95% confidence interval 16%-40%). Common adverse reactions were fever, infections, nausea, vomiting, constipation, bleeding, increased liver enzymes, and mucositis. There were no cases of VOD. These results supported the approval of GO as monotherapy for R/R CD33-positive AML using the lower-dose fractionated regimen.

IMPLICATIONS FOR PRACTICE

Gemtuzumab ozogamicin (GO) 3 mg/m² days 1, 4, and 7 is an active regimen for induction of remission when used to treat patients with relapsed or refractory CD33-positive acute myeloid leukemia without curative intent. The risks of hepatic veno-occlusive disease and early mortality with this regimen appear to be lower than reported previously for GO 9 mg/m² days 1 and 15. The data were not sufficient to enable conclusions about the safety of GO in children younger than 2 years of age.

Advances in immunotherapy for pediatric acute myeloid leukemia

INTRODUCTION

Achieving better disease control in patients diagnosed with acute myeloid leukemia (AML) has proven challenging. Overall survival has been impacted by addressing treatment related mortality with focused supportive care measures. Despite this improvement, it remains difficult to induce durable leukemia remissions despite aggressive chemotherapeutic regimens. The addition of hematopoietic stem cell transplants (HSCT) has allowed further treatment intensification and provided the benefit of graft-versus-leukemia (GVL) effect. However, HSCT carries the risk of transplant related morbidities, particularly GVHD, and anti-tumor responsiveness is still suboptimal. Thus, there is a need for alternate therapies. Immunotherapy has the potential to address this need. Areas covered: Expert opinion: The elusiveness of an ideal surface antigen target together with an immunosuppressive leukemic microenvironment add to the already difficult challenge in developing AML-targeted immunotherapies. Though many hurdles remain, recent translational discovery and progressive clinical advances anticipate exciting future developments.

AREAS COVERED

This review highlights promises and challenges to immune-based therapies for AML. It aims to summarize immunotherapeutic strategies trialed in AML patients to date, inclusive of: antibodies, vaccines, and cellular therapy. It emphasizes those being used in the pediatric population, but also includes adult clinical trials and translational science that may ultimately extend to pediatric patients.

A Phase I Study of Reduced-Intensity Conditioning and Allogeneic Stem Cell Transplantation Followed by Dose Escalation of Targeted Consolidation Immunotherapy with Gemtuzumab Ozogamicin in Children and Adolescents with CD33+ Acute Myeloid Leukemia

Myeloablative conditioning and allogeneic hematopoietic stem cell transplant (alloHSCT) in children with acute myeloid leukemia (AML) in first complete remission (CR1) may be associated with significant acute toxicity and late effects. Reduced-intensity conditioning (RIC) and alloHSCT in children is safe, feasible, and may be associated with less adverse effects. Gemtuzumab ozogamicin (GO) induces a response in 30% of patients with CD33+ relapsed/refractory AML. The dose of GO is significantly lower when combined with chemotherapy. We examined the feasibility and toxicity of RIC alloHSCT followed by GO targeted immunotherapy in children with CD33+ AML in CR1/CR2. Conditioning consisted of fludarabine 30 mg/m2 × 6 days, busulfan 3.2 to 4 mg/kg × 2 days ± rabbit antithymocyte globulin 2 mg/kg × 4 days followed by alloHSCT from matched related/unrelated donors. GO was administered ≥60 days after alloHSCT in 2 doses (8 weeks apart), following a dose-escalation design (4.5, 6, 7.5, and 9 mg/m2). Fourteen patients with average risk AML received RIC alloHSCT and post-GO consolidation: median age 13.5 years at transplant (range, 1 to 21), male-to-female 8:6, and disease status at alloHSCT 11 CR1 and 3 CR2. Eleven patients received alloHSCT from 5-6/6 HLA-matched family donors: 8 received peripheral blood stem cells, 2 received bone marrow, and 1 received related cord blood transplantation. Three patients received an unrelated allograft (two 4-5/6 and one 9/10) from unrelated cord blood unit and bone marrow, respectively. Neutrophil and platelet engraftment was observed in all assessable patients (100%), achieved at median 15.5 days (range, 7 to 31) and 21 days (range, 10 to 52), respectively. Three patients received GO at dose level 1 (4.5 mg/m2 per dose), 5 at dose level 2 (6 mg/m2 per dose), 3 at dose level 3 (7.5 mg/m2 per dose), and 3 at dose level 4 (9 mg/m2 per dose). Three of 14 patients received only 1 dose of GO after alloHSCT. One patient experienced grade III transaminitis, which resolved; no grade IV transaminitis, no grade III/IV hyperbilirubinemia, or sinusoidal obstructive syndrome were observed. The second dose of GO was given at median of 143 days (range, 120 to 209) after alloHSCT. Probability of grades II to IV acute and chronic graft-versus-host disease were 21% and 33.5%, respectively. Probability of overall survival after RIC alloHSCT and GO consolidation at 1 and 5 years was 78% and 61%, respectively. Probability of 5-year event-free survival after RIC alloHSCT and GO consolidation in patients in CR1 was 78%. No dose-limiting toxicities probably or directly related to GO were observed in this cohort. This preliminary data demonstrate that RIC followed by alloHSCT and consolidation with GO appears to be safe in children and adolescents with CD33+ AML in CR1/CR2. A phase II trial is currently underway investigating this approach with a GO dose of 9 mg/m2 per dose.

Dose-related efficacy and toxicity of gemtuzumab ozogamicin in pediatric acute myeloid leukemia

Gemtuzumab ozogamicin, an anti-tumour antibiotic linked to an anti-CD33 antibody (Mylotarg®), has been well studied in AML in adults but to a lesser extent in children. No review has yet been published on the dose-related toxicity and efficacy of gemtuzumab ozogamicin in pediatric AML patients. Here we looked at 14 studies then scatterplots and linear regressions were used to estimate the relationship between the dose of gemtuzumab and its toxicity and efficacy. A non-significant increase in bilirubin level and in incidence of veno-occlusive disease was seen with higher doses of gemtuzumab ozogamicin when used as single-agent. In terms of efficacy, even a low dose of 3 mg/m(2) of gemtuzumab ozogamicin can have antileukemic effect, but available data do not allow conclusions on its dose-dependency. Data indicate that higher doses of gemtuzumab ozogamicin account for more adverse events. The data do not show that a high dose is required for anti-leukemic efficacy of gemtuzumab ozogamicin. This study also indicates that there seems to be a role for gemtuzumab ozogamicin in the treatment of pediatric AML and further studies are required to assess its optimal dose, schedule and balance between efficacy and side-effects.

Collaborative Efforts Driving Progress in Pediatric Acute Myeloid Leukemia

Diagnosis, treatment, response monitoring, and outcome of pediatric acute myeloid leukemia (AML) have made enormous progress during the past decades. Because AML is a rare type of childhood cancer, with an incidence of approximately seven occurrences per 1 million children annually, national and international collaborative efforts have evolved. This overview describes these efforts and includes a summary of the history and contributions of each of the main collaborative pediatric AML groups worldwide. The focus is on translational and clinical research, which includes past, current, and future clinical trials. Separate sections concern acute promyelocytic leukemia, myeloid leukemia of Down syndrome, and relapsed AML. A plethora of novel antileukemic agents that have emerged, including new classes of drugs, are summarized as well. Finally, an important aspect of the treatment of pediatric AML--supportive care--and late effects are discussed. The future is bright, with a wide range of emerging innovative therapies and with more and more international collaboration that ultimately aim to cure all children with AML, with fewer adverse effects and without late effects.

Gemtuzumab ozogamicin in children and adolescents with de novo acute myeloid leukemia improves event-free survival by reducing relapse risk: results from the randomized phase III Children’s Oncology Group trial AAML0531

PURPOSE

To improve survival rates in children with acute myeloid leukemia (AML), we evaluated gemtuzumab-ozogamicin (GO), a humanized immunoconjugate targeted against CD33, as an alternative to further chemotherapy dose escalation. Our primary objective was to determine whether adding GO to standard chemotherapy improved event-free survival (EFS) and overall survival (OS) in children with newly diagnosed AML. Our secondary objectives examined outcomes by risk group and method of intensification.

PATIENTS AND METHODS

Children, adolescents, and young adults ages 0 to 29 years with newly diagnosed AML were enrolled onto Children’s Oncology Group trial AAML0531 and then were randomly assigned to either standard five-course chemotherapy alone or to the same chemotherapy with two doses of GO (3 mg/m2/dose) administered once in induction course 1 and once in intensification course 2 (two of three).

RESULTS

There were 1,022 evaluable patients enrolled. GO significantly improved EFS (3 years: 53.1% v. 46.9%; hazard ratio [HzR], 0.83; 95% CI, 0.70 to 0.99; P.04) but not OS (3 years: 69.4% v. 65.4%; HzR, 0.91; 95% CI, 0.74 to 1.13; P = .39). Although remission was not improved (88% v. 85%; P = .15), posthoc analyses found relapse risk (RR) was significantly reduced among GO recipients overall (3 years: 32.8% v. 41.3%; HzR, 0.73; 95% CI, 0.58 to 0.91; P = .006). Despite an increased postremission toxic mortality (3 years: 6.6% v. 4.1%; HzR, 1.69; 95% CI, 0.93 to 3.08; P = .09), disease-free survival was better among GO recipients (3 years: 60.6% v. 54.7%; HzR, 0.82; 95% CI, 0.67 to 1.02; P = .07).

CONCLUSION

GO added to chemotherapy improved EFS through a reduction in RR for children and adolescents with AML.

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.

Novel targeted drug therapies for the treatment of childhood acute leukemia

The cure rates for childhood acute leukemia have dramatically improved to approximately 70% overal, with treatments that include intensive cytotoxic chemotherapy and, in some cases, hematopoietic stem cell transplantation. However, many children still die of their disease or of treatment-related toxicities. Even in patients that are cured, there can be significant and, not uncommonly debilitating, acute and late complications of treatment. Improved understanding of the molecular and cellular biology of leukemia and the increasing availability of high-throughput genomic techniques have facilitated the development of molecularly targeted therapies that have the potential to be more effective and less toxic than the standard approaches. In this article, we review the progress to date with agents that are showing promise in the treatment of childhood acute leukemia, including monoclonal antibodies, inhibitors of kinases and other signaling molecules (e.g., BCR-ABL, FLT3, farnesyltransferase, mTOR and γ-secretase), agents that target epigenetic regulation of gene expression (DNA methyltransferase inhibitors and histone deacetylase inhibitors) and proteasome inhibitors. For the specific agents in each of these classes, we summarize the published preclinical data and the clinical trials that have been completed, are in progress or are being planned for children with acute leukemia. Finally, we discuss potential challenges to the success of molecularly targeted therapy, including proper target identification, adequate targeting of leukemia stem cells, developing synergistic and tolerable combinations of agents and designing adequately powered clinical trials to test efficacy in molecularly defined subsets of patients.

New targets in pediatric Acute Myeloid Leukemia

In the last few years the improvements of chemotherapy regimens and supportive care has progressively ameliorated the prognosis of children suffering from Acute Myeloid Leukemia (AML). However, a still high percentage of children do not respond to first line treatments or relapse and need to undergo further treatments. The need to explore new agents other than chemotherapy has been highlighted in the last years in order to overcome drug related resistance and toxicity. Recently, novel therapies have been studied within early phases pediatric trials and seem to show encouraging results. In fact, the knowledge of molecular abnormalities related to AML pathogenesis has permitted to identify selective drugs that may represent an important tool for the development of patient-tailored treatments. Nowadays, FLT3, Aurora Kinases, mTORS's and proteasome inhibitors represents the most promising drugs that are being used in pediatric AML studies.

Novel therapies for children with acute myeloid leukaemia

Significant improvements in survival for children with acute myeloid leukaemia (AML) have been made over the past three decades, with overall survival rates now approximately 60-70%. However, these gains can be largely attributed to more intensive use of conventional cytotoxics made possible by advances in supportive care, and although over 90% of children achieve remission with frontline therapy, approximately one third in current protocols relapse. Furthermore, late effects of therapy cause significant morbidity for many survivors. Novel therapies are therefore desperately needed. Early-phase paediatric trials of several new agents such as clofarabine, sorafenib and gemtuzumab ozogamicin have shown encouraging results in recent years. Due to the relatively low incidence of AML in childhood, the success of paediatric early-phase clinical trials is largely dependent upon collaborative clinical trial design by international cooperative study groups. Successfully incorporating novel therapies into frontline therapy remains a challenge, but the potential for significant improvement in the duration and quality of survival for children with AML is high.

The future role of monoclonal antibody therapy in childhood acute leukaemias

Leukaemia is the single most common childhood malignancy. With modern treatment regimens, survival in acute lymphoblastic leukaemia (ALL) approaches 90%. Only about 70% of children with acute myeloid leukaemia (AML) achieve long term survival. Patients who relapse have a dismal prognosis. Novel therapeutic approaches are needed to improve treatment outcomes in newly-diagnosed patients with a poor prognosis and for patients with relapsed/refractory disease that have limited treatment options. One promising approach in treating haematological malignancies has been the use of monoclonal antibodies to target cell surface antigens expressed on malignant cells. Most success with monoclonal antibody therapy in the treatment of haematological malignancies has come in the setting of adult B-cell non-Hodgkin lymphoma with the addition of the anti-CD20 monoclonal antibody rituximab to standard treatment regimens. In order to further advance treatment of haematological malignancies, novel monoclonal antibodies continue to be developed that target a variety of cell surface antigens. Several antibodies continue to be investigated in childhood leukaemias. This review will discuss the development of monoclonal antibodies that target a variety of cell surface antigens for the treatment of childhood ALL and the use of the anti-CD33 antibody gemtuzumab ozogamicin in the treatment of childhood AML.

Diagnosis and management of acute myeloid leukemia in children and adolescents: recommendations from an international expert panel

Despite major improvements in outcome over the past decades, acute myeloid leukemia (AML) remains a life-threatening malignancy in children, with current survival rates of ∼70%. State-of-the-art recommendations in adult AML have recently been published in this journal by Döhner et al. The primary goal of an international expert panel of the International BFM Study Group AML Committee was to set standards for the management, diagnosis, response assessment, and treatment in childhood AML. This paper aims to discuss differences between childhood and adult AML, and to highlight recommendations that are specific to children. The particular relevance of new diagnostic and prognostic molecular markers in pediatric AML is presented. The general management of pediatric AML, the management of specific pediatric AML cohorts (such as infants) or subtypes of the disease occurring in children (such as Down syndrome related AML), as well as new therapeutic approaches, and the role of supportive care are discussed.

Gemtuzumab ozogamicin as postconsolidation therapy does not prevent relapse in children with AML: results from NOPHO-AML 2004

There are no data on the role of postconsolidation therapy with gemtuzumab ozogamicin (GO; Mylotarg) in children with acute myeloid leukemia (AML). The NOPHO-AML 2004 protocol studied postconsolidation randomization to GO or no further therapy. GO was administered at 5 mg/m(2) and repeated after 3 weeks. We randomized 120 patients; 59 to receive GO. Survival was analyzed on an intention-to-treat basis. The median follow-up for patients who were alive was 4.2 years. Children who received GO showed modest elevation of transaminase and bilirubin without signs of veno-occlusive disease. Severe neutropenia followed 95% and febrile neutropenia 40% of the GO courses. Only a moderate decline in platelet count and a minor decrease in hemoglobin occurred. Relapse occurred in 24 and 25 of those randomized to GO or no further therapy. The median time to relapse was 16 months versus 10 months (nonsignificant). The 5-year event-free survival and overall survival was 55% versus 51% and 74% versus 80% in those randomized to receive GO or no further therapy, respectively. Results were similar in all subgroups. In conclusion, GO therapy postconsolidation as given in this trial was well tolerated, showed a nonsignificant delay in time to relapse, but did not change the rate of relapse or survival (clinicaltrials.gov identifier NCT00476541).

Correlation of CD33 expression level with disease characteristics and response to gemtuzumab ozogamicin containing chemotherapy in childhood AML

CD33 is expressed on the majority of acute myeloid leukemia (AML) leukemic blasts and is the target for gemtuzumab ozogamicin (GO), a toxin-conjugated anti-CD33 mAb. In the present study, we quantified the CD33 mean fluorescent intensity of leukemic blasts prospectively in 619 de novo pediatric AML patients enrolled in Children's Oncology Group GO-containing clinical trials and determined its correlation with disease characteristics and clinical outcome. CD33 expression varied more than 2-log fold; a median mean fluorescent intensity of 129 (range, 3-1550.07) was observed. Patients were divided into 4 quartiles, quartiles 1-4 (Q1-4) based on expression and disease characteristics and clinical response defined across quartiles. High CD33 expression was associated with high-risk FLT3/ITD mutations (P < .001) and was inversely associated with low-risk disease (P < .001). Complete remission (CR) rates were similar, but patients in Q4 had significantly lower overall survival (57% ± 16% vs 77% ± 7%, P = .002) and disease-free survival from CR (44% ± 16% vs 62% ± 8%, P = .022). In a multivariate model, high CD33 expression remained a significant predictor of overall survival (P = .011) and disease-free survival (P = .038) from CR. Our findings suggest that CD33 expression is heterogeneous within de novo pediatric AML. High expression is associated with adverse disease features and is an independent predictor of inferior outcome. The correlation between CD33 expression and GO response is under investigation. These studies are registered at www.clinicaltrials.gov as NCT00070174 and NCT00372593.

Institutional experience with clofarabine and cytarabine in relapsed pediatric acute myeloid leukemia

Cytarabine (1000 mg/m/d intravenous for 5 d) and clofarabine (40 mg/m/d intravenous for 5 d) were given every 28 days to 9 children with relapsed acute myeloid leukemia at our institution. Among 19 courses, there were 18 infectious episodes. Median hospitalization time was 13 days (7.7 to 30.5 d) per cycle. Hepatobiliary abnormalities included alanine aminotransferase/aspartate aminotransferase elevation and hyperbilirubinemia. Four patients achieved complete remission (one after an earlier allogeneic Haematopoietic Progenitor Cell Transplant). Four patients are alive disease free. In summary, a proportion of children responded and was able to receive allogeneic Haematopoietic Progenitor Cell Transplant. Side effects were tolerable, although hospitalization time was prolonged.

Treatment of acute myeloid leukemia in children: experience from a tertiary care hematology centre in India

OBJECTIVE

To assess the treatment and outcome of children with acute myeloid leukemia. The Primary objectives were to assess remission rates, treatment related toxicity and disease free survival. Secondary objective was to assess prognostic factors associated with poor outcome.

METHODS

A retrospective analysis of all treated patients with acute myeloid leukemia, less than 18 year of age from Sept 2005 to Aug 2009 was done. Clinical laboratory, treatment and follow up records retrieved to calculate remission rate, treatment related toxicity, disease free survival and poor prognostic factors.

RESULTS

This analysis included thirty five patients (male : female; 23:12), twenty seven (77.1%) achieved remission after one 3 + 7 induction and seven required two inductions. High dose cytosine arabinoside consolidation was given in thirty one patients while one underwent allogenic stem cell transplantation. Two patients died during chemotherapy (TRM- 5.7%), two did not complete the therapy, seventeen relapsed (48.5%) with 80% of relapses occurring within first year of remission and no relapse occurred after 2 years. Fourteen patients are in remission (40%, follow up 5-54 months) and cumulative median disease free survival is of 13 months.

CONCLUSIONS

The present data suggests that 3 + 7 induction, followed by high dose cytarabine consolidation has low treatment related toxicity and resource utilization; however, relapse free survival is inferior to more intensive regimens, highlighting the need to intensify chemotherapy regimen once the treatment related mortality has been minimized.

Treating refractory leukemias in childhood, role of clofarabine

Approximately 4000 children and adolescents under the age of 20 years develop acute leukemia per year in the US. Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. Despite impressive improvements in outcome, relapsed ALL is the fourth most common pediatric malignancy. Therapy for relapsed ALL remains unsatisfactory, and the majority of relapse patients still succumb to leukemia. Between one-third and one-half of patients with acute myelogenous leukemia (AML) relapse, and no standard therapy is recognized for patients with relapsed and/or refractory AML. Novel therapeutic agents are needed to improve the cure rate for relapsed ALL and AML. Clofarabine is a next-generation nucleoside analog, designed to incorporate the best features and improve the therapeutic index of cladribine and fludarabine. Clofarabine inhibits both DNA polymerase and ribonucleotide reductase, leading to impaired DNA synthesis and repair, and directly induces apoptosis. Phase I and II single-agent trials in children have shown that clofarabine is safe and active in both myeloid and lymphoid relapsed/refractory acute leukemias. Clofarabine has been approved by the FDA for pediatric patients with relapsed/refractory ALL after at least 2 prior therapeutic attempts. Rational combinations of clofarabine with other active agents in refractory leukemias are currently under investigation.

Upfront use of gemtuzumab ozogamicin in young children with CD33-positive AML

Gemtuzumab ozogamicin (GO) is a humanized anti-CD33 antibody used for treating patients with CD33+ acute myeloid leukemia (AML). We report three young children (two infants and one toddler) with AML treated with GO 9 mg/m(2). Two received two doses at diagnosis alone with conventional chemotherapy and one received one dose after relapse. GO was well tolerated and all three achieved remission. All were transplanted: one relapsed after 5 months and died of disease, one died a toxic death in remission due to pulmonary fibrosis, and one survived (41 months from diagnosis). In conclusion, GO was well tolerated in these young patients with evidence for efficacy.

Acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous group of leukemias that result from clonal transformation of hematopoietic precursors through the acquisition of chromosomal rearrangements and multiple gene mutations. As a result of highly collaborative clinical research by pediatric cooperative cancer groups worldwide, disease-free survival has improved significantly during the past 3 decades. Further improvements in outcomes of children who have AML probably will reflect continued progress in understanding the biology of AML and the concomitant development of new molecularly targeted agents for use in combination with conventional chemotherapy drugs.

Salvage treatment for children with refractory first or second relapse of acute myeloid leukaemia with gemtuzumab ozogamicin: results of a phase II study

The prognosis of children with relapsed/refractory acute myeloid leukaemia (AML) is poor, and new therapies are needed. Gemtuzumab ozogamicin (GO) is an anti-CD33 antibody linked to the antitumor antibiotic calicheamicin. We conducted an investigator-initiated phase II study with GO to assess its efficacy and safety, administering two dosages of 7.5 mg/m(2) with a 14 d-interval. Thirty children who were refractory to re-induction at first relapse or suffered from second relapse of AML received a total of 64 infusions of GO. The response rate [complete remission (CR) and CR with insufficient platelet recovery] was 37%. Nine patients were subsequently transplanted (median time to transplant, 4 weeks, range 3-21 weeks), and three of these patients are currently in continuous CR with a median follow-up of >3 years, and can considered to be cured. This resulted in a statistically significant survival advantage for children who responded to GO versus those who did not [27% (standard error 13%) vs. 0%, respectively, P = 0.001]. All other children died, mainly from progressive disease. The treatment was generally well tolerated by most patients. The frequency of transient transaminatis was low. All but one patient received defibrotide prophylaxis during the transplant procedure, and no cases of veno-occlusive disease were noted. This study showed a favourable safety/efficacy profile of single-agent GO in children with refractory first or second relapse of AML.

Efficacy of fractionated gemtuzumab ozogamicin combined with cytarabine in advanced childhood myeloid leukaemia

Gemtuzumab ozogamicin (GO) monotherapy is reported to yield a 20-30% response rate in advanced acute myeloid leukaemia (AML). This study examined the efficacy and tolerability of GO combined with cytarabine (GOCYT) in children with refractory/relapsed CD33(+) AML. Seventeen children received GO 3 mg/m(2) on days 1, 4 and 7 plus cytarabine 100 mg/m(2)/d for 7 d on a compassionate-use basis. Seven patients then received GO-based consolidation. At the outset of GOCYT, two patients were refractory; eight patients were in refractory first relapse; six patients had relapsed after stem cell transplantation (SCT); and one patient [del(5q) therapy-related AML (t-AML)] had not yet been treated. Mean follow-up was 17 months (8-33 months). Ten responses were obtained after GOCYT induction, including complete remission (CR) or CR without complete recovery of platelets (CRp) in six patients (35%). The responses improved in three children who received GOCYT consolidation, increasing the CR + CRp rate to 53%. SCT was subsequently performed in eight responders. Grade 3-4 adverse events consisted of haematological disorders (n = 17, 100%) and documented infections (n = 5, 29%). No cases of sinusoidal obstructive syndrome occurred. Three patients were alive at the cut-off date for this analysis, all of whom had responded to GOCYT. GOCYT combination therapy yielded a high response rate (53%) and showed acceptable toxicity in heavily pretreated children with refractory/relapsed AML. These results warrant a larger prospective study.

Safety and efficacy of gemtuzumab ozogamicin in combination with chemotherapy for pediatric acute myeloid leukemia: a report from the Children's Oncology Group

PURPOSE

While gemtuzumab ozogamicin (GTMZ) is commonly used in the treatment of acute myeloid leukemia (AML) in combination with standard chemotherapy agents, the pediatric maximum-tolerated dose (MTD) of GMTZ in combination with chemotherapy has not been determined.

PATIENTS AND METHODS

The Children's Oncology Group AAML00P2 trial sought to define the MTD of GMTZ in combination with cytarabine and mitoxantrone and cytarabine and l-asparaginase chemotherapy regimens.

RESULTS

The MTD for GMTZ in combination with cytarabine and mitoxantrone was 3 mg/m(2) while the MTD in combination with cytarabine and l-asparaginase was 2 mg/m(2). Toxicities observed in both treatment regimens were typical of those seen in the relapsed AML setting and consisted primarily of infectious complications. The overall remission response rate (mean +/- SE) was 45% +/- 15% and the 1 year event-free survival and overall survival estimates were 38% +/- 14% and 53% +/- 15%, respectively.

CONCLUSION

This trial determined the pediatric MTD for GMTZ with two commonly used AML chemotherapy combinations. Based on these results, an ongoing phase III trial conducted within the Children's Oncology Group is evaluating the effect of GMTZ when added to standard AML therapy.

Integration of monoclonal antibodies and immunoconjugates into the treatment of acute myeloid leukemia

PURPOSE OF REVIEW

This review addresses use of monoclonal antibodies and immunoconjugates to treat acute myeloid leukemia.

RECENT FINDINGS

Monoclonal antibodies used in acute myeloid leukemia have been directed against the antigens CD33, CD45, and CD66. Unconjugated monoclonal antibodies such as lintuzumab have modest activity against overt acute myeloid leukemia but can eliminate minimal residual disease in acute promyelocytic leukemia. Most experience with immunoconjugates is with gemtuzumab ozogamicin, an anti-CD33 monoclonal antibody linked to the potent antitumor antibiotic calicheamicin. Gemtuzumab ozogamicin has shown activity both singly, particularly in acute promyelocytic leukemia, and combined with conventional cytotoxic chemotherapy. Radiolabeled monoclonal antibodies against CD45 and CD66 have also been used to intensify the conditioning regimen before stem cell transplantation. The most promising results were obtained with radiolabeled anti-CD45 antibodies. Antibodies reactive with CD66 have been used to deliver targeted radiation to hematopoietic tissues in patients with advanced myeloid malignancies.

SUMMARY

Both unlabeled monoclonal antibodies and immunoconjugates appear to have a limited role if used as single agents to treat acute myeloid leukemia. These agents hold promise as potentially useful additions to conventional therapy, but the optimal dosing and timing remain to be defined.

Acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous group of leukemias that result from clonal transformation of hematopoietic precursors through the acquisition of chromosomal rearrangements and multiple gene mutations. As a result of highly collaborative clinical research by pediatric cooperative cancer groups worldwide, disease-free survival has improved significantly during the past 3 decades. Further improvements in outcomes of children who have AML probably will reflect continued progress in understanding the biology of AML and the concomitant development of new molecularly targeted agents for use in combination with conventional chemotherapy drugs.

Gemtuzumab ozogamicin in the treatment of acute myeloid leukemia

Gemtuzumab ozogamicin (GO) is a chemotherapeutic agent that consists of a humanized anti-CD33 antibody (hP67.6) linked to N-acetyl-calicheamicin 1,2-dimethyl hydrazine dichloride, a potent enediyne antitumor antibiotic. GO was approved conditionally by the Federal Drug Administration in May 2000 as single-agent therapy for first recurrence of acute myeloid leukemia (AML) in patients over the age of 60 years who are unfit for conventional cytotoxic therapy. In this setting, it produces a complete response (CR) rate of 13%, with another 13% achieving CR with inadequate platelet recovery (CRp). The most common adverse effects associated with GO are infusion-related reactions and myelosuppression. GO monotherapy at the dose of 9 mg/m(2) is complicated with hepatic veno-occlusive disease in approximately 5% of cases, particularly prior to or following stem cell transplantation. Attenuated doses of GO or fractionated doses appear to be equally effective and better tolerated. GO has shown remarkable activity in acute promyelocytic leukemia, particularly for the elimination of minimal residual disease. Combinations of GO with chemotherapy as induction or post-remission therapy are promising, and phase III trials are ongoing.

Gemtuzumab ozogamicin, cytosine arabinoside, G-CSF combination (G-AraMy) in the treatment of elderly patients with poor-prognosis acute myeloid leukemia

BACKGROUND

Gemtuzumab ozogamicin (GO) is effective as single agent in the treatment of acute myeloid leukemia (AML). We evaluated efficacy and safety of a chemotherapy including growth factors, cytarabine, and GO (G-AraMy) in the treatment of poor-prognosis AML in elderly patients.

PATIENTS AND METHODS

In three Italian hematology departments from September 2003 to September 2006, 53 elderly patients [median age 69 years (range 65-77)] with untreated or primary refractory/relapsed AML were enrolled on the combination G-AraMy administered according to two consecutive schedules (G-AraMy1 and G-AraMy2), with intensified consolidation in the second. Twenty-three of 53 patients had a secondary acute myeloid leukemia (sAML).

RESULTS

The overall response rate was 57%. The most common adverse event was myelosuppression. Seven patients died in induction (13%). No differences for response rate and toxicity profile were observed between untreated and primary resistant/relapsed patients, de novo AML and sAML, and in the two treatment trials. Median disease-free survival and overall survival were 8 months (range 2-23+) and 9 months (range 2-24+).

CONCLUSIONS

G-AraMy therapy may be considered an useful treatment approach for poor-risk elderly AML patients, with a complete remission rate comparable to literature data with reduced side-effects, also in a poor-prognosis population.

The role of Gemtuzumab Ozogamicin in the treatment of acute myeloid leukemia patients

Gemtuzumab Ozogamicin (GO) is an antibody-targeted chemotherapy agent consisting of the humanized murine CD33 antibody (clone P67.6) to which the calicheamicin-g1 derivative is attached via a hydrolysable bifunctional linker. GO is able to induce apoptosis in vitro in CD33-expressing cells and it has been approved in USA and in Europe as monotherapy for the treatment of elderly patients (older than 60 years) with relapsed acute myeloid leukemia (AML). GO administered as a single agent has resulted in overall response rates of about 30% in previously relapsed adults AML patients (including also with incomplete platelet recovery). Preliminary data indicate a potential role for GO also as a component of induction or consolidation regimens in adults and children. As for adverse events, veno-occlusive syndrome characterizes its tolerability profile, but GO is comparatively well tolerated by most patients.

Monoclonal antibodies and immunoconjugates in acute myeloid leukemia

The use of monoclonal antibodies for patients with acute myeloid leukemia is based on targeting cell-surface antigens preferentially expressed on leukemic blasts while sparing normal cells and tissues. The majority of studies performed to date have used antibodies reactive with the CD33 antigen. Phase II studies have demonstrated antileukemic responses with all agents, although less so with unlabeled antibodies. The most promising results have been obtained in the treatment of minimal residual disease in patients with acute promyelocytc leukemia. Antibody-targeted chemotherapy with gemtuzumab ozogamicin has also shown significant activity in patients with relapsed acute myeloid leukemia. Radioimmunotherapy with beta-particle emitters may be most effective for the treatment of bulky disease or as part of a conditioning regimen for hematopoietic stem-cell transplantation, whereas radioimmunotherapy with alpha-particle emitters may be better suited to the treatment of small-volume or minimal residual leukemia. Whether or not monoclonal antibody therapy will improve disease outcome compared with conventional treatment regimens remains to be demonstrated by well-designed clinical trials.

Gemtuzumab ozogamicin-associated sinusoidal obstructive syndrome (SOS): an overview from the research on adverse drug events and reports (RADAR) project

Gemtuzumab ozogamicin (GO) was approved for marketing in 2000 by the United States Food and Drug Administration (FDA) for older patients with relapsed acute myeloid leukemia (AML). Four months later, 14 phase II clinical trial participants who received novel GO-containing combination chemotherapy regimens developed an unexpected hepatic toxicity termed sinusoidal obstructive syndrome (SOS) or hepatic veno-occlusive disease (VOD). Investigators associated with the Research on Adverse Drug Events and Reports (RADAR) project reviewed safety reports for GO included in reports of clinical trials and observational studies, interim reports from an FDA mandated Prospective Observational Registry, and the Food and Drug Administration's Adverse Event Reporting System. Medline searches provided incidence estimates of GO-associated SOS and comparative rates of SOS without GO. SOS is characterized by hyperbilirubinemia, painful hepatomegaly, ascites, and sudden weight gain developing at a median of 10 days following GO administration for patients who did not undergo an allogeneic SCT procedure and 13 days following an allogeneic SCT for patients who had previously received GO. Among adult AML patients who received GO in clinical trials, SOS incidence was 3% at doses < or =6 mg/m(2) if administered as monotherapy or in combination with non-hepatotoxic agents versus 28% if administered with thioguanine and 15% when administered as monotherapy at a dose of 9 mg/m(2). Observational studies identified SOS rates between 15% and 40% if an SCT is performed within 3 months of GO administration. The FDA mandated Prospective Observational Registry of patients who receive care at 60 medical centers has identified GO-associated SOS rates of 14% if an SCT is performed and 9% otherwise. Caution is advised when administering GO in routine clinical practice, particularly if administered with other hepatotoxic agents, at doses and schedules more intensive than those approved by the FDA, or within 3 months of a SCT procedure.

Efficacy and tolerability of gemtuzumab ozogamicin (anti-CD33 monoclonal antibody, CMA-676, Mylotarg) in children with relapsed/refractory myeloid leukemia

BACKGROUND

Gemtuzumab ozogamicin (GO) is a cytotoxic anti-CD33 monoclonal antibody that has given promising preliminary results in adult myeloid CD33+ AML. We conducted a retrospective multicenter study of 12 children treated with GO on a compassionate basis (median age 5.5 y). Three patients (2 MDS/AML, 1 JMML) were refractory to first-line treatment, 8 patients with de novo AML were in refractory first relapse, and one patient with de novo AML was in 2nd relapse after stem cell transplantation (SCT). CD33 expression exceeded 20% in all cases.

METHODS

GO was administered alone, at a unit dose of 3-9 mg/m2, once (3 patients), twice (3 patients), three (5 patients) or five times (1 patient). Mean follow-up was 128 days (8-585 d).

RESULTS

There were three complete responses (25%) leading to further curative treatment (SCT). Treatment failed in the other nine patients, and only one patient was alive at the end of follow-up. NCI-CTC grade III/IV adverse events comprised hematological toxicity (n = 12), hypertransaminasemia (n = 2), allergy and hyperbilirubinemia (1 case each). There was only one major adverse event (grade IV allergy). No case of sinusoidal obstruction syndrome occurred.

CONCLUSION

These results warrant a prospective trial of GO in a larger population of children with AML.

The role of gemtuzumab ozogamicin in acute leukaemia therapy

Gemtuzumab ozogamicin (GO) is an immunoconjugate that binds to CD33 on the surface of acute myeloid leukaemia (AML) blasts and, after internalisation, releases a cytotoxic drug, calicheamicin. GO is approved by the US Food and Drug Administration for the treatment of CD33-positive AML at first relapse in patients 60 years and older who are not candidates for other cytotoxic therapy. GO as a single agent has low antileukaemic activity. When given to patients meeting the criteria noted above, it produces a complete response (CR) rate of only 12%, with another 12% achieving CR with inadequate platelet recovery (CRp). The median survival of patients treated with GO monotherapy is 11.2 months. GO therapy at 9 mg/m(2) is complicated with hepatic veno-occlusive disease in 5-10% of patients, particularly prior to or following stem cell transplantation. GO at lower doses combined with chemotherapy as induction or postremission therapy is promising, however, and phase III trials are ongoing. GO is probably most active in acute promyelocytic leukaemia (APL). It is used for induction regimens in high-risk APL and for the elimination of minimal residual APL. Case reports suggest that GO also has activity in CD33-positive acute lymphoblastic leukaemia. In conclusion, single agent GO can induce responses in patients with CD33-positive AML in first recurrence. The future of GO is its use in combination with other cytotoxic agents. Ongoing clinical trials may better define the role of GO combinations, particularly in untreated AML.

Treatment of childhood acute myeloid leukemia

Childhood acute myeloid leukemia is rare, but accounts for a significant number of malignancy-related deaths in this age group. However, the prognosis has improved over past decades, and survival rates of 60% and above have been reported. Still, this implies that more than a third of children and adolescents die from this disease. Moreover, treatment is intensive, and quality of life and late effects are worrying issues. Therefore, there is a need for further improved treatment of pediatric acute myeloid leukemia. This review describes several important developments in this respect, such as improved diagnostics, prognostic factors, subgroup-directed and tailored treatment, and targeted therapy. In addition, background information is provided and current treatment strategies are described, as well as the late effects of treatment. Most groups now have risk-group adapted protocols, with allogeneic stem cell transplantation often being reserved for the higher risk group. Even in these cases, the benefit of stem cell transplantation has not been demonstrated beyond reasonable doubt with current high-intensive chemotherapy. Similarly, the use of cranial irradiation for CNS prophylaxis and maintenance treatment does not seem to be indicated in general. Subgroup-directed treatment has become a reality for acute myeloid leukemia in young children with Down's syndrome and in acute promyelocytic leukemia. In addition to tailoring therapy according to biologic features and especially monitoring treatment by measurements of minimal residual disease, targeted therapy for subgroups with activating mutations in receptor tyrosine kinases will further optimize the treatment of pediatric acute myeloid leukemia. Together with the development of many novel agents that have different mechanisms of action than the currently available anticancer agents, and improved supportive care, it is realistic that the prognosis of acute myeloid leukemia in children and adolescents will improve further in the next 5-10 years.