Salvage therapy with ARA-C and gemtuzumab ozogamicin in AML patients relapsing after stem cell transplantation

Treatment of AML Relapse After Allo-HCT

With advances in allogeneic hematopoietic stem cell transplant (allo-HCT), disease relapse has replaced transplant-related mortality as the primary cause of treatment failure for patients with acute myeloid leukemia (AML). The efficacy of allo-HCT in AML is a consequence of a graft-versus-leukemia (GVL) effect that is mediated by T lymphocytes, and unique mechanisms of immune evasion underlying post-allo-HCT AML relapses have recently been characterized. Relapsed AML following allo-HCT presents a particularly vexing clinical challenge because transplant-related toxicities, such as graft-versus-host (GVHD) and infections, increase the risk of treatment-related morbidity and mortality. In general, the prognosis of relapsed AML following allo-HCT is poor with most patients failing to achieve a subsequent remission and 2-year survival consistently <15%. The two factors that have been found to predict a better prognosis are a longer duration of post-transplant remission prior to relapse and a lower disease burden at the time of relapse. When considered in combination with a patient's age; co-morbidities; and performance status, these factors can help to inform the appropriate therapy for the treatment of post-transplant relapse. This review discusses the options for the treatment of post-transplant AML relapse with a focus on the options to achieve a subsequent remission and consolidation with cellular immunotherapy, such as a second transplant or donor lymphocyte infusion (DLI). While intensive reinduction therapy and less intensive approaches with hypomethylating agents have long represented the two primary options for the initial treatment of post-transplant relapse, molecularly targeted therapies and immunotherapy are emerging as potential alternative options to achieve remission. Herein, we highlight response and survival outcomes achieved specifically in the post-transplant setting using each of these approaches and discuss how some therapies may overcome the immunologic mechanisms that have been implicated in post-transplant relapse. As long-term survival in post-transplant relapse necessarily involves consolidation with cellular immunotherapy, we present data on the efficacy and toxicity of both DLI and second allo-HCT including when such therapies are integrated with reinduction. Finally, we provide our general approach to the treatment of post-transplant relapse, integrating both novel therapies and our improved understanding of the mechanisms underlying post-transplant relapse.

The promising role of antibody drug conjugate in cancer therapy: Combining targeting ability with cytotoxicity effectively

Introduction

Traditional cancer therapy has many disadvantages such as low selectivity and high toxicity of chemotherapy, as well as insufficient efficacy of targeted therapy. To enhance the cytotoxic effect and targeting ability, while reducing the toxicity of antitumor drugs, an antibody drug conjugate (ADC) was developed to deliver small molecular cytotoxic payloads directly to tumor cells by binding to specific antibodies via linkers.

Method

By reviewing published literature and the current progress of ADCs, we aimed to summarize the basic characteristics, clinical progress, and challenges of ADCs to provide a reference for clinical practice and further research.

Results

ADC is a conjugate composed of three fundamental components, including monoclonal antibodies, cytotoxic payloads, and stable linkers. The mechanisms of ADC including the classical internalization pathway, antitumor activity of antibodies, bystander effect, and non‐internalizing mechanism. With the development of new drugs and advances in technology, various ADCs have achieved clinical efficacy. To date, nine ADCs have received US Food and Drug Administration (FDA) approval in the field of hematologic tumors and solid tumors, which have become routine clinical treatments.

Conclusion

ADC has changed traditional treatment patterns for cancer patients, which enable the same treatment for pancreatic cancer patients and promote individualized precision treatment. Further exploration of indications could focus on early‐stage cancer patients and combined therapy settings. Besides, the mechanisms of drug resistance, manufacturing techniques, optimized treatment regimens, and appropriate patient selection remain the major topics.

Novel agents targeting leukemia cells and immune microenvironment for prevention and treatment of relapse of acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

Relapse remains the worst life-threatening complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with acute myeloid leukemia (AML), whose prognosis has been historically dismal. Given the rapid development of genomics and immunotherapies, the interference strategies for AML recurrence have been changing these years. More and more novel targeting agents that have received the U.S. Food and Drug Administration (FDA) approval for de novo AML treatment have been administrated in the salvage or maintenance therapy of post-HSCT relapse. Targeted strategies that regulate the immune microenvironment of and optimize the graft versus leukemia (GVL) effect of immune cells are gradually improved. Such agents not only have been proven to achieve clinical benefits from a single drug, but if combined with classic therapies, can significantly improve the poor prognosis of AML patients who relapse after allo-HSCT. This review will focus on currently available and promising upcoming agents and also discuss the challenges and limitations of targeted therapies in the allogeneic hematopoietic stem cell transplantation community.

Gemtuzumab ozogamicin for the treatment of acute myeloid leukemia in adults

INTRODUCTION

Treatment of acute myeloid leukemia (AML) has changed dramatically in the past ten years with the approval of targeted agents, the first of which was the anti-CD33 antibody-drug conjugate gemtuzumab ozogamicin (GO). Despite withdrawal from the market after accelerated approval, GO was reapproved and now has a well-established role in treating select AML patients. CD33 has proven to be an important target for drug development in AML as evidenced by the improvement in survival with GO treatment.

AREAS COVERED

The review summarizes the development of GO, its mechanism of action, initial studies and approval, withdrawal from the market, and subsequent reapproval after the results of several large randomized studies became available. We also provide an overview of its current role in the treatment landscape of AML.

EXPERT OPINION

Multiple phase 3 trials with GO have established a significant benefit with GO in induction therapy for favorable risk AML. Additional studies support the use of GO in relapsed/refractory AML and APL. Despite the withdrawal of GO from the market after initial approval, GO has proven to improve survival of select AML patients when added to induction chemotherapy and in relapsed disease.

Gemtuzumab ozogamicin and novel antibody-drug conjugates in clinical trials for acute myeloid leukemia

Targeted agents are increasingly used for the therapy of acute myeloid leukemia (AML). Gemtuzumab ozogamicin (GO) is the first antibody-drug conjugate (ADC) approved for induction therapy of AML. When used in fractionated doses, GO combined with the conventional cytarabine/anthracycline-based induction chemotherapy significantly improves the outcome of previously untreated AML patients. Single-agent GO is effective and safe for AML patient ineligible for intensive chemotherapy. Multiple combination regimens incorporating GO have also been recommended as potential alternative options. In addition, several novel ADCs targeting CD33, CD123 and CLL-1 are currently undergoing preclinical or early clinical investigations. In this review, we summarized the efficacy and limitations of GO as well as novel ADCs for adult AML patients.

Risk Factors Influencing Outcome of Acute Leukemia Patients Who Experience Relapse After Allogeneic Hematopoietic Stem-Cell Transplantation

BACKGROUND

Prognosis of acute leukemia patients who experience relapse after hematopoietic stem-cell transplantation (HSCT) remains poor. Identifying risk factors influencing outcome of these patients is essential.

PATIENTS AND METHODS

Follow-up of 234 acute leukemia patients who underwent allogeneic HSCT from matched related donor was performed for occurrence of posttransplantation relapse. Statuses of remission and survival were assessed at 6 months after treatment of relapse. Analysis of risk factors influencing postrelapse overall survival (prOS), complete remission (CR), and nonrelapse mortality (NRM) was carried out.

RESULTS

Posttransplantation relapse occurred in 43 patients (17.9%). After treatment, 11 patients (25.6%) experienced postrelapse remission, the prOS rate was 20.9% (9 patients), and the NRM rate was 25.6% (11 patients). Older age (P = .007) and failure to experience remission after relapse treatment (P = .027) were associated with lower prOS in multivariate analysis. Female sex (P = .027), posttransplantation extramedullary relapse (P = .001), and absence of postrelapse graft-versus-host disease P = .025) were associated with lower CR rate. Also, presence of extramedullary relapse (P = .011) was associated with lower risk of NRM whereas treatment of posttransplantation relapse with donor lymphocyte infusion with or without chemotherapy (P = .002) and occurrence of postrelapse graft-versus-host disease (P = .025) were associated with higher risk of NRM.

CONCLUSION

Survival of acute leukemia patients who experience relapse after allogeneic HSCT is poor, especially in elderly patients and those who do not experience remission after relapse treatment.

Gene expression profiling in myelodysplastic syndrome after SPARC overexpression associated with Ara-C

Secreted protein acidic and rich in cysteine (SPARC) is involved in many biological processes, including erythropoiesis and cell proliferation. However, the role of SPARC in myelodysplastic syndrome (MDS) remains to be elucidated. Pyrimidine analogue cytosine arabinoside (Ara-C) is among the most effective agents used in the treatment of acute leukemia. The aim of the present study was to determine whether the chemotherapeutic activity of Ara-C was enhanced by the overexpression of SPARC. DNA microarray technology and RNA sequencing were employed to examine differential gene expression in the apoptosis signaling pathway after gene change occurred in cells following drug treatment. The results showed that upregulation of the expression of SPARC induced SKM-1 cell death and inhibited proliferation. Additionally, the apoptotic rate of SPARC overexpression combined with Ara-C increased significantly. Transcription factors CPBP and ZNF333 regulated the 69 genes and long non-coding RNA (lncRNA). Moreover, the mRNA and protein expression of apoptosis-related genes in the DNA microarray results were increased. These results suggest that SPARC expression changes with Ara-C, revealing a possible application in the treatment of MDS.