Gene expression profiling identifies FLT3 mutation-like cases in wild-type FLT3 acute myeloid leukemia

Precision medicine in AML: overcoming resistance

The development of molecularly targeted therapy for acute myeloid leukemia is progressing at an accelerated pace. Therapies targeting FLT3, IDH1, IDH2, and BCL2 have been approved in the last 5 years. As we exploit these biological vulnerabilities, various mechanisms of resistance arise. Emergence of competing clones with different genetic drivers and acquisition of constitutional mutations in the target renders therapies ineffective, and enzymatic isoform changes can lead to reappearance of the disease phenotype. Understanding the timing and circumstances of resistance origination will allow clinicians to develop combinatorial and sequential therapeutic approaches to deepen responses and improve survival. The objective of this review is to illustrate the biological underpinnings of each therapy and the landscape of resistance mechanisms and discuss strategies to overcome on- and off-target resistance.

Therapeutic biomarkers in acute myeloid leukemia: functional and genomic approaches

Acute myeloid leukemia (AML) is clinically and genetically a heterogeneous disease characterized by clonal expansion of abnormal hematopoietic progenitors. Genomic approaches to precision medicine have been implemented to direct targeted therapy for subgroups of AML patients, for instance, IDH inhibitors for IDH1/2 mutated patients, and FLT3 inhibitors with FLT3 mutated patients. While next generation sequencing for genetic mutations has improved treatment outcomes, only a fraction of AML patients benefit due to the low prevalence of actionable targets. In recent years, the adoption of newer functional technologies for quantitative phenotypic analysis and patient-derived avatar models has strengthened the potential for generalized functional precision medicine approach. However, functional approach requires robust standardization for multiple variables such as functional parameters, time of drug exposure and drug concentration for making in vitro predictions. In this review, we first summarize genomic and functional therapeutic biomarkers adopted for AML therapy, followed by challenges associated with these approaches, and finally, the future strategies to enhance the implementation of precision medicine.

Advances in the pharmacological management of acute myeloid leukemia in adults

INTRODUCTION

With advances in molecular medicine and precision approaches, there has been significant improvement in the treatment of acute myeloid leukemia (AML) in recent years. This reflects better understanding of molecular and metabolic pathways in leukemia cells, including BCL2 upregulation that prevents apoptosis, FLT3 tyrosine kinase activating mutations that allow uncontrolled proliferation, and IDH mutations that result in differentiation block.

AREAS COVERED

We performed a compressive review of important pre-clinical studies in AML that involve major molecular and metabolic pathways in AML, and we discussed standard therapeutic modalities and ongoing clinical trials for patients with AML, as well as an overall update of recent efforts in this area.

EXPERT OPINION

Targeting these pathways has resulted in improvement in the overall survival of some groups of AML patients. Secondary AML and TP53 mutated AML remain challenging subtypes of AML with limited treatment options and represent areas of unmet research need. Ongoing work with menin inhibitors in MLL rearranged leukemia, which comprise a large portion of secondary AML cases, the development of CAR T cell products and targeting the CD47 receptor on macrophages in myeloid neoplasms including in TP53 mutated AML have provided hope for these challenging subtypes of AML.

Role of Biomarkers in FLT3 AML

Simple Summary

Genetically heterogeneous disorder acute myeloid leukemia (AML) is marked by recurring mutations in FLT3. Current FLT3 inhibitors and other emerging inhibitors have helped in the improvement of the quality of standard of care therapies; however, the overall survival of the patients remains static. This is due to numerous mutations in FLT3, which causes resistance against these FLT3 inhibitors. For effective treatment of AML patients, alternative approaches are required to overcome this resistance. Here, we will summarize the biomarkers for FLT3 inhibitors in AML, as well as the alternative measures to overcome resistance to the current therapies.

Abstract

Acute myeloid leukemia is a disease characterized by uncontrolled proliferation of clonal myeloid blast cells that are incapable of maturation to leukocytes. AML is the most common leukemia in adults and remains a highly fatal disease with a five-year survival rate of 24%. More than 50% of AML patients have mutations in the FLT3 gene, rendering FLT3 an attractive target for small-molecule inhibition. Currently, there are several FLT3 inhibitors in the clinic, and others remain in clinical trials. However, these inhibitors face challenges due to lack of efficacy against several FLT3 mutants. Therefore, the identification of biomarkers is vital to stratify AML patients and target AML patient population with a particular FLT3 mutation. Additionally, there is an unmet need to identify alternative approaches to combat the resistance to FLT3 inhibitors. Here, we summarize the current knowledge on the utilization of diagnostic, prognostic, predictive, and pharmacodynamic biomarkers for FLT3-mutated AML. The resistance mechanisms to various FLT3 inhibitors and alternative approaches to combat this resistance are also discussed and presented.