Adding low-dose gemtuzumab ozogamicin to fludarabine, Ara-C and idarubicin (MY-FLAI) may improve disease-free and overall survival in elderly patients with non-M3 acute myeloid leukaemia: results of a prospective, pilot, multi-centre trial and comparison with a historical cohort of patients

Infectious complications of targeted drugs and biotherapies in acute leukemia. Clinical practice guidelines by the European Conference on Infections in Leukemia (ECIL), a joint venture of the European Group for Blood and Marrow Transplantation (EBMT), the European Organization for Research and Treatment of Cancer (EORTC), the International Immunocompromised Host Society (ICHS) and the European Leukemia Net (ELN)

The 9th web-based European Conference on Infections in Leukemia (ECIL-9), held September 16-17, 2021, reviewed the risk of infections and febrile neutropenia associated with more recently approved immunotherapeutic agents and molecular targeted drugs for the treatment of acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Novel antibody based treatment approaches (inotuzumab ozogamicin, gemtuzumab ozogamicin, flotetuzumab), isocitrate dehydrogenases inhibitors (ivosidenib, enasidenib, olutasidenib), FLT3 kinase inhibitors (gilteritinib, midostaurin, quizartinib), a hedgehog inhibitor (glasdegib) as well as a BCL2 inhibitor (venetoclax) were reviewed with respect to their mode of action, their immunosuppressive potential, their current approval and the infectious complications and febrile neutropenia reported from clinical studies. Evidence-based recommendations for prevention and management of infectious complications and specific alerts regarding the potential for drug-drug interactions were developed and discussed in a plenary session with the panel of experts until consensus was reached. The set of recommendations was posted on the ECIL website for a month for comments from members of EBMT, EORTC, ICHS and ELN before final approval by the panelists. While a majority of these agents are not associated with a significantly increased risk when used as monotherapy, caution is required with combination therapy such as venetoclax plus hypomethylating agents, gemtuzumab ozogamicin plus cytotoxic drugs or midostaurin added to conventional AML chemotherapy.

Feasibility and Outcome of a Phase II Study of Intensive Induction Chemotherapy in 91 Elderly Patients with AML Evaluated Using a Simplified Multidimensional Geriatric Assessment

Introduction

We prospectively tested in a phase II study high-dose aracytin and idarubicin plus amifostine as induction regimen in 149 patients with acute myeloid leukaemia (AML) aged ≥ 60 years, evaluated by a simplified multidimensional geriatric assessment (MGA).

Methods

Ninety-one fully or partially fit patients (61%) were allocated to intensive chemotherapy and 58 (39%) frail patients to best supportive care (BSC). Intensively treated patients, showing early death and complete response (CR) rate respectively of 5.5% and 73.6%, received 61 consolidations, followed by autologous transplant (ASCT), stem cell transplantation (SCT) or gemtuzumab ozogamicin, depending on mobilization outcome and donor availability.

Results

The 8-year overall survival (OS) of these patients was 20.4%, with median duration of 11.4 months significantly superior to the 1.5 months of BSC arm (p < 0.001). Hyperleukocytosis and cytogenetics were predictors of survival with a relative risk of 1.8 in patients with poor karyotype without hyperleukocytosis (p = 0.02) and 3 in those with hyperleukocytosis (≥ 50,000/μl) (p = 0.002).

Conclusion

MGA allowed tailored post-consolidation in 53.8% of patients after high-dose aracytin induction, with long-term survival doubling that reported in the literature after standard-dose cytarabine regimens.

Trial Registration

The study was registered with the Umin Clinical Trial Registry (www.umin.ac.jp/ctr), number R000014052.

Electronic Supplementary Material

The online version of this article (10.1007/s12325-020-01310-4) contains supplementary material, which is available to authorized users.

Therapeutic targeting of gastrointestinal cancer stem cells

Gastrointestinal cancers remain a tremendous burden on society. Despite advances in therapy options, including chemotherapy and radiation, cancer mortality from recurrences and metastases occur frequently. Cancer stem cells (CSCs) drive disease recurrence and metastasis, as these cells are uniquely equipped to self-renew and evade therapy. Therefore, cancer eradication requires treatment strategies that target CSCs in addition to differentiated cancer cells. This review highlights current literature on therapies targeting CSCs in gastrointestinal cancer.

Low-dose homoharringtonine and cytarabine in combination with granulocyte colony-stimulating factor for elderly patients with de novo acute myeloid leukemia

The treatment of young patient with acute myeloid leukemia (AML) has improved dramatically during the past several decades. However, management of elderly patients with AML still remains a challenge. A total of 56 elderly patients with de novo AML were treated with homoharringtonine and cytarabine in combination with granulocyte colony-stimulating factor (HCG). The overall response rate was 75% (60.7%% complete response [CR] and 14.3% partial response). Fourteen (25%) of the 56 patients showed no response. A higher CR rate was observed in patients aged < 70 years, with better-risk or intermediate-risk karyotype and with NPM1 mutations. To the date of the last follow-up, the median overall survival (OS) was 12.0±1.7 months. There were significant correlations of OS with age, initial karyotype, performance status and gene mutations (NPM1,FLT-ITD and DNMT3A) at diagnosis. The early death rate was 7.1%. Hematologic toxicity was well tolerated; and severe non-hematologic toxicity was not observed.

Gastric cancer stem cells: therapeutic targets

During the past decade, a growing body of evidence has implied that cancer stem cells (CSCs) play an important role in the development of gastric cancer (GC). The notion that CSCs give rise to GC and may be responsible for invasion, metastasis, and resistance to treatment has profound implications for anti-cancer therapy. Recent major advances in the rapidly evolving field of CSCs have opened novel exciting opportunities for developing CSC-targeted therapies. Discovery of specific markers and signaling pathways in gastric CSCs (GCSCs), with the perfecting of technologies for identification, isolation, and validation of CSCs, may provide the basis for a revolutionary cancer treatment approach based on the eradication of GCSCs. Emerging therapeutic tools based on specific properties and functions of CSCs, including activation of self-renewal signaling pathways, differences in gene expression profiles, and increased activity of telomerase or chemoresistance mechanisms, are developing in parallel with advances in nanotechnology and bioengineering. The addition of GCSC-targeted therapies to current oncological protocols and their complementary application may be the key to successfully fighting GC.

Integrating post induction WT1 quantification and flow-cytometry results improves minimal residual disease stratification in acute myeloid leukemia

Fifty uniformly treated adult AML patients were analyzed with respect to pre-treatment and post-induction risk factors. Forty-two patients achieving complete hematological remission were assessed for minimal residual disease (MRD) by WT1 gene expression; 34 by flow-cytometry (flow-MRD). Patients who were flow-MRD negative had a better 3-year disease-free (DFS; 79.5% vs. 27.3%; p=.032) compared with patients who were still positive after induction. Interestingly, DFS of flow-MRD positive patients was not related to the amount of flow-detected clone population (≥ or <1%, p=.41) but to WT1 reduction (ΔWT1, 3-year DFS; 46.2% vs. 0% if ΔWT1 was ≥ or < of 1.5 log, p=.001). In AML, combining MRD results provided by WT1 quantification and flow-cytometry improves the reliability of MRD-based prognostic stratification. Similar analyses by further larger studies should be advocated.

Fludarabine, cytarabine, and attenuated-dose idarubicin (m-FLAI) combination therapy for elderly acute myeloid leukemia patients

We performed a phase II trial to evaluate the efficacy and safety of the modified fludarabine, cytarabine, and attenuated-dose idarubicin (m-FLAI) regimen in elderly acute myeloid leukemia (AML) patients. Elderly (≥60 years) AML patients who had not previously received chemotherapy were enrolled in the study. Patients received two consecutive cycles of m-FLAI chemotherapy as an induction. The m-FLAI regimen comprised fludarabine (25 mg/m(2) , days 1-4), cytarabine (1,000 mg/m(2) , days 1-4), and attenuated-dose idarubicin (5 mg/m(2) , days 1-3). The primary end point was complete remission (CR) rate. Secondary end points were overall survival (OS), event-free survival (EFS), and treatment-related mortality (TRM). There were 108 patients (median age 68.4 years, M:F = 64:44) enrolled in the study. CR was achieved in 56.5% of patients, and the TRM rate was 21.3%. Median OS and median EFS were 10.2 and 6.6 months, respectively. The mortality at 30 and 60 days was 15 and 21%, respectively. Performance status and comorbidity did not have prognostic value in this patient cohort. Bone marrow expression of CD117 was associated with increased EFS and OS. m-FLAI is an effective induction regimen for previously untreated AML in elderly patients. In addition, bone-marrow CD117 expression is an independent favorable prognostic factor in elderly AML patients. (ClinicalTrials.gov number, NCT01247493).

Antibody-drug conjugates of calicheamicin derivative: gemtuzumab ozogamicin and inotuzumab ozogamicin

Antibody-drug conjugates (ADC) are an attractive approach for the treatment of acute myeloid leukemia and non-Hodgkin lymphomas, which in most cases, are inherently sensitive to cytotoxic agents. CD33 and CD22 are specific markers of myeloid leukemias and B-cell malignancies, respectively. These endocytic receptors are ideal for an ADC strategy because they can effectively carry the cytotoxic payload into the cell. Gemtuzumab ozogamicin (GO, Mylotarg) and inotuzumab ozogamicin consist of a derivative of calicheamicin (a potent DNA-binding cytotoxic antibiotic) linked to a humanized monoclonal IgG4 antibody directed against CD33 or CD22, respectively. Both of these ADCs have a target-mediated pharmacokinetic disposition. GO was the first drug to prove the ADC concept in the clinic, specifically in phase II studies that included substantial proportions of older patients with relapsed acute myeloid leukemia. In contrast, in phase III studies, it has thus far failed to show clinical benefit in first-line treatment in combination with standard chemotherapy. Inotuzumab ozogamicin has shown remarkable clinical activity in relapsed/refractory B-cell non-Hodgkin lymphoma, and it has started phase III evaluation. The safety profile of these ADCs includes reversible myelosuppression (especially neutropenia and thrombocytopenia), elevated hepatic transaminases, and hyperbilirubinemia. There have been postmarketing reports of hepatotoxicity, especially veno-occlusive disease, associated with GO. The incidence is ~2%, but patients who undergo hematopoietic stem cell transplantation have an increased risk. As we steadily move toward the goal of personalized medicine, these kinds of agents will provide a unique opportunity to treat selected patient subpopulations based on the expression of their specific tumor targets.

Gemtuzumab ozogamicin in non-acute promyelocytic acute myeloid leukemia

INTRODUCTION

Gemtuzumab ozogamicin (GO) has been used in relapsed, refractory and newly diagnosed acute myeloid leukemia (AML) as a single agent and in combination with intensive chemotherapy. Results of recent Phase III trials have led to its withdrawal in the USA although a beneficial effect of GO in genetically defined AML subgroups was evident.

AREAS COVERED

This review examines the use of GO as a single agent or in combination with intensive chemotherapy in non-acute promyelocytic AML. The literature search was based on publications on GO indexed in the PubMed electronic database and selected meeting abstracts. GO has shown moderate activity as a single agent but promising activity in combination with intensive chemotherapy in refractory or relapsed AML. Relapsed AML defined molecularly by mutant nucleophosmin-1 without concurrent fms-related tyrosine kinase 3 (FLT3) internal tandem duplication seems to benefit most from GO. In newly diagnosed AML two up-front randomized Phase III trials evaluating GO in induction therapy failed to demonstrate an improvement in response and survival. Again, genetically defined subgroups may benefit.

EXPERT OPINION

Future challenges of personalized therapy in AML will be to integrate the signals from current subgroup analyses underlining the role of GO in genetically defined AML entities.

Improved outcome of patients with low- and intermediate-risk cytogenetics acute myeloid leukemia (AML) in first relapse with gemtuzumab and cytarabine versus cytarabine: results of a retrospective comparative study

BACKGROUND

Acute myeloid leukemia (AML) in first relapse is associated with a poor outcome even when treated with intermediate- to high-dose cytarabine (IHDAraC). Gemtuzumab ozogamycin (GO) used as a single agent has clinical activity in relapsed and refractory AML. Various combination regimens of GO have been developed, but few data are available regarding their efficacy compared with IHDAraC-based regimens.

METHODS

The authors performed a retrospective analysis of response and survival in 90 AML patients in first relapse treated with either IHDAraC (n = 56) or IHDAraC + GO (n = 34). Patient characteristics of the two groups were comparable.

RESULTS

Median follow-up was 37 months. Compared with IHDAraC, IHDAraC + GO induction was associated with a better response rate (68% vs 45%, P = .04), a better overall survival (median, 35 months vs 6 months, P = .001), and a better event-free survival (24 months vs 6 months, P = .002). This effect was limited to patients with low-risk and intermediate-risk cytogenetics. In multivariate analysis, age, cytogenetic risk, first complete remission duration, and the use of IHDAraC + GO were independently associated with better results.

CONCLUSIONS

This study showed that the addition of GO to IHDAraC is associated with a better efficacy for patients in first relapse of AML with low- or intermediate-risk cytogenetics. Prospective controlled studies of GO in this population are warranted. Patients with high-risk cytogenetics should be offered investigational new drugs.

The Role of Monoclonal Antibodies in the Management of Leukemia

This article will review the monoclonal antibodies more commonly used in leukemias. In the last three decades, scientists have made considerable progress understanding the structure and the functions of various surface antigens, such as CD20, CD33. The introduction of rituximab, an anti CD20 monoclonal antibody, had a great impact in the treatment of lymphoproliferative disorders. Gemtuzumab, an anti CD 33 conjugated monoclonal antibody has activity in acute mylegenous leukemia (AML). As this field is undergoing a rapid growth, the years will see an increasing use of monoclonal antibodies in hematological malignancies.

Sequence of administration and methylation of SOCS3 may govern response to gemtuzumab ozogamicin in combination with conventional chemotherapy in patients with refractory or relapsed acute myelogenous leukemia (AML)

In older patients suffering from acute myelogenous leukemia (AML), aggressive chemotherapy is accompanied with high treatment-related morbidity and mortality. Gemtuzumab ozogamicin (GO), a humanized monoclonal anti-CD33 antibody, represents a well tolerated treatment option, but optimal treatment schedules are still unknown. Additionally, Suppressor of cytokine signaling 3 (SOCS3) inhibits the CD33-induced block on cytokine-induced proliferation. Consequently, a variable response of AML cells to anti-CD33-targeted therapy may be caused by modulation of SOCS3 expression. Twenty-four patients with refractory or relapsed CD33-positive AML received GO as a single agent before or after conventional chemotherapy. The methylation status of the SOCS3 CpG island was assessed by methylation-specific polymerase chain reaction. Response (RR) and overall survival (OS) were significantly higher in 16 patients receiving chemotherapy before GO (RR 81%, OS 14.8 months) compared to three patients who received GO single agent therapy (RR 33%, OS 7.2 months) or 16 with GO before chemotherapy (RR 0% OS 2.2 months, P = 0.01 for RR and P < 0.001 for OS). Methylation of the SOCS3 CpG island was found in 8/24 patients. There was a trend towards a higher RR and longer OS in patients with SOCS3 hypermethylation (RR 86%, OS 25.1 months) compared to unmethylated SOCS3 (RR 56%, OS 10.3 months, P = 0.09). Administration of GO a few days after chemotherapy seems to provide better response and survival compared to administration of GO directly before chemotherapy. The potential role of SOCS3 hypermethylation as a biomarker should be further investigated in patients undergoing GO containing therapies.

Challenges in treating older patients with acute myeloid leukemia

Whereas in younger patients diagnosed with acute myeloid leukemia (AML) treatment is straightforward and the goal is cure, the optimal treatment decision for older adults remains highly controversial. Physicians need to determine whether palliation, “something” beyond palliation, intensive therapy, or an investigational therapy is the most appropriate treatment option. This requires understanding of the biology and risk profile of the AML, clinical judgment in evaluating the functional status of the patient, communication skills in understanding the patient's wishes and social background, and medical expertise in available therapies. The physician has to accurately inform the patient about (a) the unique biological considerations of his leukemia and his prognosis; (b) the risks and benefits of all available treatment options; (c) novel therapeutic approaches and how the patient can get access to these treatments. Last but not least, he has to recommend a treatment. This paper tries to discuss each of these issues.

Immunotherapy prospects for acute myeloid leukaemia

While chemotherapy is successful at inducing remission of acute myeloid leukaemia (AML), the disease has a high probability of relapse. Strategies to prevent relapse involve consolidation chemotherapy, stem cell transplantation and immunotherapy. Evidence for immunosurveillance of AML and susceptibility of leukaemia cells to both T cell and natural killer (NK) cell attack and justifies the application of immune strategies to control residual AML persisting after remission induction. Immune therapy for AML includes allogeneic stem cell transplantation, adoptive transfer of allogeneic or autologous T cells or NK cells, vaccination with leukaemia cells, dendritic cells, cell lysates, peptides and DNA vaccines and treatment with cytokines, antibodies and immunomodulatory agents. Here we describe what is known about the immunological features of AML at presentation and in remission, the current status of immunotherapy and strategies combining treatment approaches with a view to achieving leukaemia cure.

Intracellular activation of SGN-35, a potent anti-CD30 antibody-drug conjugate

PURPOSE

SGN-35 is an antibody-drug conjugate (ADC) containing the potent antimitotic drug, monomethylauristatin E (MMAE), linked to the anti-CD30 monoclonal antibody, cAC10. As previously shown, SGN-35 treatment regresses and cures established Hodgkin lymphoma and anaplastic large cell lymphoma xenografts. Recently, the ADC has been shown to possess pronounced activity in clinical trials. Here, we investigate the molecular basis for the activities of SGN-35 by determining the extent of targeted intracellular drug release and retention, and bystander activities.

EXPERIMENTAL DESIGN

SGN-35 was prepared with (14)C-labeled MMAE. Intracellular ADC activation on CD30(+) and negative cell lines was determined using a combination of radiometric and liquid chromatograhpy/mass spectrometry-based assays. The bystander activity of SGN-35 was determined using mixed tumor cell cultures consisting of CD30(+) and CD30(-) lines.

RESULTS

SGN-35 treatment of CD30(+) cells leads to efficient intracellular release of chemically unmodified MMAE, with intracellular concentrations of MMAE in the range of 500 nmol/L. This was due to specific ADC binding, uptake, MMAE retention, and receptor recycling or resynthesis. MMAE accounts for the total detectable released drug from CD30(+) cells, and has a half-life of retention of 15 to 20 h. Cytotoxicity studies with mixtures of CD30(+) and CD30(-) cell lines indicated that diffusible released MMAE from CD30(+) cells was able to kill cocultivated CD30(-) cells.

CONCLUSIONS

MMAE is efficiently released from SGN-35 within CD30(+) cancer cells and, due to its membrane permeability, is able to exert cytotoxic activity on bystander cells. This provides mechanistic insight into the pronounced preclinical and clinical antitumor activities observed with SGN-35.

Low-dose cytarabine and aclarubicin in combination with granulocyte colony-stimulating factor for elderly patients with previously untreated acute myeloid leukemia

We evaluated the efficacy of low-dose cytarabine and aclarubicin combined with granulocyte colony-stimulating factor (CAG) in elderly patients with previously untreated acute myeloid leukemia. Patients aged between 60 and 70 years who were not eligible for standard chemotherapy protocols and patients aged over 70 years were all registered. Thirty-three of 68 patients (49%) achieved remission. Median disease-free survival was 10 months and overall survival was nine months. Performance status after chemotherapy in patients who achieved remission was generally favorable. The present study demonstrates that CAG therapy is efficacious and well tolerated in the majority of elderly patients.

Applications of monoclonal antibodies for the treatment of hematological malignancies

BACKGROUND

The introduction of mAbs has changed the clinical approach to patients with lymphoma and leukemia.

OBJECTIVE

To summarize the most significant applications of mAb-based regimens in the treatment of hematological malignancies and explore their possible role in the future management of these patients.

RESULTS

Rituximab (anti-CD20) was the first mAb developed for the treatment of B-cell lymphomas. Several randomized studies have demonstrated its efficacy in lymphomas and low toxicity profile; rituximab also has significant activity in chronic lymphocytic leukemia (CLL). Alemtuzumab (anti-CD52) has shown efficacy in previously untreated or refractory CLL patients, while gemtuzumab ozogamicin (anti-CD33) appears to have significant activity in acute myeloid leukemias and myelodysplastic syndromes.

CONCLUSIONS

In the next few years, investigations will be concentrated on the improvement of the older mAbs, and the development of new mAbs, targeting molecules important for malignant cell cycle and survival in an attempt to further improve patient survival.

Targeted treatment of acute myeloid leukemia in older adults: role of gemtuzumab ozogamicin

As the overall prognosis and treatment response rate to standard chemotherapy for acute myeloid leukemia (AML) remains poor in the older adult population, there is a need for more effective therapeutic agents with lower toxicity profiles that can be offered to these patients. Gemtuzumab ozogamicin (GO) is an anti-CD33 monoclonal antibody that was approved by the US Food and Drug Administration for use as monotherapy in patients 60 years of age and older with relapsed AML. GO consists of a humanized anti-CD33 antibody (hP67.6) which is linked to N-acetyl-gamma calicheamicin 1,2-dimethyl hydrazine dichloride. Once the antibody attaches to the surface antigen, it is rapidly internalized. Calicheamicin, a potent enediyne, is subsequently released and acts as a cytotoxic anti-tumor agent. In this population, GO has an acceptable toxicity and yields response rates approaching 30%. The efficacy of GO as monotherapy and in combination therapy for treatment of both de novo and relapsed AML continues to be investigated.

Antibody therapy for acute myeloid leukemia

Due to the high rate of relapse in younger patients and the overall poor outcome in older patients, novel therapies are needed for the treatment of acute myeloid leukemia (AML). Monoclonal antibodies have become an important treatment modality in cancer therapy. Gemtuzumab ozogamicin (GO), an anti-CD33 immunoconjugate, was approved by the US Food and Drug Administration (FDA) for the treatment of elderly patients with relapsed AML who are not candidates for standard chemotherapy. Single-agent GO and combinations with standard chemotherapeutics have been explored extensively in this disease. Hepatotoxicity and delayed myelosuppression have been dose-limiting. Its toxicity profile is reduced with decreased doses of GO and even by administering only a single infusion. In patients with acute promyelocytic leukemia (APL), the addition of GO can produce molecular remissions and is well tolerated. Targeted immunotherapy with GO for treatment of AML has produced remissions. In order to reduce toxicity and improve efficacy, its optimal dose and schedule and pairing with other standard chemotherapeutic agents need to be defined better in large clinical trials.

Gemtuzumab-ozogamicin in combination with fludarabine, cytarabine, idarubicin (FLAI-GO) as induction therapy in CD33-positive AML patients younger than 65 years

INTRODUCTION

The addition of gemtuzumab-ozogamicin (GO) to an induction regimen including synergistic drugs, such as intermediate dose of cytarabine (Ara-C), idarubicin and fludarabine (FLAI), could reduce treatment failure in acute myeloid leukemia (AML) patients. Nevertheless, the role and safety of this antibody target-therapy in first-line chemotherapy in patients younger than 65 years has not yet been defined.

PATIENTS AND METHODS

The primary goal of this prospective phase II pilot study was to evaluate the efficacy and the safety profile of FLAI plus GO as induction regimen. Thirty consecutive AML patients were included. All patients were younger than 65 with a median age of 53 years and CD33 expression exceeded 20% in all cases. The M/F ratio was 16/14 and 21/30 (70%) of patients were poor-risk at diagnosis. The induction regimen (FLAI-GO) included fludarabine (30mg/m(2)) and Ara-C (2g/m(2)) on days 1-5, idarubicin (10mg/m(2)) on days 1, 3, and 5 and GO (3mg/m(2)) on day 6. Hematopoietic stem cell transplant (HSCT) was planned for all high risk AML patients in first complete remission (CR) after consolidation with intermediate doses of Ara-C and idarubicin (IDAC-IDA). Cytogenetic, multidrug-resistance phenotype, FLT3 mutation status, and WT1 quantitative expression analyses were performed at diagnosis in all patients. WT1 expression and cytogenetic (in positive cases) analyses were performed after induction to detect and follow minimal residual disease.

RESULTS

Patients were evaluated for response rate, treatment-related adverse events, overall survival and relapse free survival. After induction with FLAI-GO, CR rate was 90% (26 of 29 evaluable pts); one patient achieved partial remission and two were resistant. There was only one case of death during induction (DDI). After FLAI-GO, the mean value of WT1 dropped from 4200+/-2777 copies/10(4)ABL to 192+/-399 copies/10(4)ABL. The toxicity of FLAI-GO was acceptable; 57% of patients experienced transient and reversible GO infusion-related adverse events (especially fever and chills), but no cases of veno-occlusive disease occurred during CHT or after HSCT. After a median follow-up of 16 months (range 2-25), 24/30 (80%) patients are alive (24/24 in CR). The probability of 1-year OS and RFS was 90 and 85%, respectively. Allogeneic and autologus HSCT was performed in 19 (63%) and 4 (13%) patients, respectively.

CONCLUSIONS

These preliminary results suggest that FLAI-GO is an effective and well tolerated induction regimen for CD33 positive AML patients younger than 65 years, with a high complete response rate, favourable safety profile, low DDI. These results encourage the testing of this regimen in a multicenter prospective trial.

CD133/prominin-1 is a potential therapeutic target for antibody-drug conjugates in hepatocellular and gastric cancers

CD133/prominin-1 is a pentaspan transmembrane glycoprotein overexpressed in various solid tumours including colorectal and glioblastomas. CD133 was found here to be highly expressed in ⩾50% of pancreatic, gastric and intrahepatic cholangiocarcinomas. Quantitative flow cytometric analysis showed that a panel of established hepatocellular, pancreatic and gastric cancer cell lines expressed CD133 at levels higher than normal epithelial cells or bone marrow progenitor cells. A murine anti-human CD133 antibody (AC133) conjugated to a potent cytotoxic drug, monomethyl auristatin F (MMAF), effectively inhibited the growth of Hep3B hepatocellular and KATO III gastric cancer cells in vitro with IC₅₀ values of 2–7 ng ml⁻¹. MMAF induced apoptosis in the cancer cells as measured by caspase activation. The anti-CD133-drug conjugate (AC133-vcMMAF) was shown to internalise and colocalised with the lysosomal marker CD107a in the sensitive cell lines. In contrast, in the resistant cell line Su.86.86, the conjugate internalised and colocalised with the caveolae marker, Cav-1. Addition of ammonium chloride, an inhibitor of lysosomal trafficking and processing, suppressed the cytotoxic effect of AC133-vcMMAF in both Hep3B and KATO III. Anti-CD133-drug conjugate treatment resulted in significant delay of Hep3B tumour growth in SCID mice. Anti-CD133 antibody-drug conjugates warrant further evaluation as a therapeutic strategy to eradicate CD133+ tumours.

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.