A phase I/II study of sorafenib in combination with low dose cytarabine in elderly patients with acute myeloid leukemia or high-risk myelodysplastic syndrome from the National Cancer Institute of Canada Clinical Trials Group: trial IND.186

Phase 1 study of azacitidine in combination with quizartinib in patients with FLT3 or CBL mutated MDS and MDS/MPN

We conducted a phase 1 study evaluating 3 dose levels of quizartinib (30 mg, 40 mg or 60 mg) in combination with azacitidine for HMA-naïve or relapsed/refractory MDS or MDS/MPN with FLT3 or CBL mutations. Overall, 12 patients (HMA naïve: n=9, HMA failure: n=3) were enrolled; 7 (58 %) patients had FLT3 mutations and 5 (42 %) had CBL mutations. The maximum tolerated dose was not reached. Most common grade 3-4 treatment-emergent adverse events were thrombocytopenia (n=5, 42 %), anemia (n=4, 33 %), lung infection (n=2, 17 %), skin infection (n=2, 17 %), hyponatremia (n=2, 17 %) and sepsis (n=2, 17 %). The overall response rate was 83 % with median relapse-free and overall survivals of 15.1 months (95 % CI 0.0-38.4 months) and 17.5 months (95 % CI NC-NC), respectively. FLT3 mutation clearance was observed in 57 % (n=4) patients. These data suggest quizartinib is safe and shows encouraging activity in FLT3-mutated MDS and MDS/MPN. This study is registered at Clinicaltrials.gov as NCT04493138.

Improved Posttransplant Outcomes in Recent Years for AML Patients with FLT3-ITD and Wild-type NPM1: A Report from the EBMT Acute Leukemia Working Party

PURPOSE

Allogeneic hematopoietic cell transplantation (allo-HCT) is recommended in first complete remission (CR1) in patients with acute myeloid leukemia (AML) harboring FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD). We assessed changes over time in transplant characteristics and outcomes in patients with AML age 60 years and younger with a FLT3-ITD.

EXPERIMENTAL DESIGN

We identified 1,827 adult patients with AML (median age 49 years, range 18-60) with FLT3-ITD and intermediate karyotype, allografted between 2012 and 2021 in CR1.

RESULTS

NPM1 was mutated in 72% of patients. We compared changes over time in 688 patients transplanted between 2012 and 2016, and 1,139 patients transplanted between 2017 and 2021. For patients with wild-type NPM1, the 2-year leukemia-free survival (LFS) and overall survival (OS) significantly improved over time from 54% to 64% (HR = 0.67; P = 0.011) and from 63% to 71% (HR = 0.66; P = 0.021), respectively. Allo-HCT in recent years significantly reduced the cumulative incidence of relapse (CIR). For patients with NPM1 mutation, no significant changes over time were noted.

CONCLUSIONS

In patients with AML with FLT3-ITD and wild-type NPM1, we noticed a significant decrease over time in the CIR and improvement of LFS and OS, likely reflecting the efficacy of FLT-3 inhibitors, including when used as posttransplant maintenance, in this high-risk setting. On the contrary, no significant change over time was noticed in outcomes of patients harboring a FLT3 and NPM1 mutation.

Therapeutic Targets in Myelodysplastic Neoplasms: Beyond Hypomethylating Agents

PURPOSE OF REVIEW

To discuss novel targeted therapies under investigation for treatment of myelodysplastic neoplasms (MDS).

RECENT FINDINGS

Over the last few years, results of phase 3 trials assessing novel therapies for high-risk MDS have been largely disappointing. Pevonedistat (NEDD-8 inhibitor) and APR-246 (TP53 reactivator) both did not meet trial endpoints. However, early phase trials of BCL-2, TIM3, and CD47 inhibitors have shown exciting data and are currently under phase 3 investigation. Moreover, combination of hypomethylating agents (HMA) with novel therapies targeting the mutational (IDH, FLT3, spliceosome complex) or immune (PD-1/PDL-1, TIM-3, IRAK-4) pathways are being investigated in early phase clinical trials and have shown adequate safety and promising efficacy. Myelodysplastic neoplasms (MDS) are a group of hematopoietic neoplasms defined by cytopenias and morphological dysplasia. They are characterized by clonal proliferation of aberrant hematopoietic stem cells caused by recurrent genetic abnormalities. This leads to ineffective erythropoiesis, peripheral blood cytopenias, abnormal cell maturation, and a high risk of transformation into acute myeloid leukemia (AML). Allogeneic hematopoietic stem cell transplantation is the only curative therapy; however, it is not a suitable option for majority patients due to their age, comorbidities, and the high rate of treatment-related complications. HMAs remain the only FDA-approved treatment option for high-risk MDS. Due to intolerance, primary, and secondary resistance to HMA, there is a large unmet need to develop new safe and effective therapies for patients with MDS. In this review, we focus on the current management strategies and novel therapies in development for treatment of high-risk MDS.

Precision Medicine in Myeloid Malignancies: Hype or Hope?

PURPOSE OF REVIEW

We review how understanding the fitness and comorbidity burden of patients, and molecular landscape of underlying acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) at the time of diagnosis is now integral to treatment.

RECENT FINDINGS

The upfront identification of patients' fitness and molecular profile facilitates selection of targeted and novel agents, enables risk stratification, allows consideration of allogeneic hematopoietic cell transplantation in high-risk patients, and provides treatment selection for older (age ≥ 75) or otherwise unfit patients who may not tolerate conventional treatment. The use of measurable residual disease (MRD) assessment improves outcome prediction and can also guide therapeutic strategies such as chemotherapy maintenance and transplant. In recent years, several novel drugs have received FDA approval for treating patients with AML with or without specific mutations. A doublet and triplet combination of molecular targeted and other novel treatments have resulted in high response rates in early trials. Following the initial success in AML, novel drugs are undergoing clinical trials in MDS. Unprecedented advances have been made in precision medicine approaches in AML and MDS. However, lack of durable responses and long-term disease control in many patients still present significant challenges, which can only be met, to some extent, with innovative combination strategies throughout the course of treatment from induction to consolidation and maintenance.

Molecular Targeted Therapy and Immunotherapy for Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) is a heterogeneous, clonal hematological disorder characterized by ineffective hematopoiesis, cytopenia, morphologic dysplasia, and predisposition to acute myeloid leukemia (AML). Stem cell genomic instability, microenvironmental aberrations, and somatic mutations contribute to leukemic transformation. The hypomethylating agents (HMAs), azacitidine and decitabine are the standard of care for patients with higher-risk MDS. Although these agents induce responses in up to 40-60% of patients, primary or secondary drug resistance is relatively common. To improve the treatment outcome, combinational therapies comprising HMA with targeted therapy or immunotherapy are being evaluated and are under continuous development. This review provides a comprehensive update of the molecular pathogenesis and immune-dysregulations involved in MDS, mechanisms of resistance to HMA, and strategies to overcome HMA resistance.

FMS-Like Tyrosine Kinase 3 Inhibitors for the Treatment of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most common acute leukemia of adults, with a five-year survival that remains poor (approximately 25%). Knowledge and understanding of AML genomics have expanded tremendously over the past decade and are now included in AML prognostication and treatment decisions. FMS-like tyrosine kinase 3 (FLT3) is a Class III receptor tyrosine kinase (RTK) expressed primarily in the cell membranes of early hematopoietic progenitor cells, found in 28% of all patients with AML. FLT3 is the second most frequent mutation in adult AML following Nuclear-cytoplasmic shuttling phosphoprotein (NPM1), which is found in 50% of cases.¹ FLT3 inhibitors are promising new molecular therapeutics increasingly becoming standard of care for both newly diagnosed and relapsed/refractory FLT3 positive AML. This review will focus on the clinical trials/evidence, similarities, differences, clinical toxicities, and drug interactions relevant to treating clinicians as pertains to 5 FLT3-inhibitors: midostaurin, sorafenib, gilteritinib, crenolanib, and quizartinib.

Management of the Older Patient with Myelodysplastic Syndrome

No two diagnoses of myelodysplastic syndrome are genuinely alike, owing to differing and dynamic mutational topography and epigenetic aberrancy. Consequently, no two patients with myelodysplastic syndrome are identical and disease-specific and patient-specific factors are considered in formulating the optimal treatment, which includes few that are disease modifying. Age itself should not be an absolute contraindication to therapy, including intensive therapy such as allogeneic hematopoietic stem cell transplantation, which is the only curative therapy. However, age associates with an increased prevalence of frailty and comorbidities that must be considered and may preclude a path to cure. Palliative therapies are the mainstay for many patients with myelodysplastic syndrome, which is a disease of older adults with the majority of patients diagnosed at age ≥ 75 years. The older patient requires heightened attention to end organ function/reserve and drug-drug interactions as well as insurance, income, cost, and socioeconomic and psychosocial issues that influence management. Many prior studies have included relatively younger populations or have not specifically performed high-quality subgroup analyses of older patients. In this review, we discuss the available standard-of-care therapies for myelodysplastic syndrome as they specifically relate to the older population and assess the emerging therapeutics that may further the pursuit for personalized treatment and improve both the outcomes and quality of life of the older patient with myelodysplastic syndrome.

Molecular Targeted Therapy in Myelodysplastic Syndromes: New Options for Tailored Treatments

Simple Summary

Myelodysplastic syndromes (MDS) are a group of diseases in which bone marrow stem cells acquire genetic alterations and can initiate leukemia, blocking the production of mature blood cells. It is of crucial importance to identify those genetic abnormalities because some of them can be the targeted. To date only very few drugs are approved for patients manifesting this group of disorders and there is an urgent need to develop new effective therapies. This review gives an overview of the genetic of MDS and the therapeutic options available and in clinical experimentation.

Abstract

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematopoietic disorders characterized by ineffective hematopoiesis, progressive cytopenias and increased risk of transformation to acute myeloid leukemia. The improved understanding of the underlying biology and genetics of MDS has led to better disease and risk classification, paving the way for novel therapeutic opportunities. Indeed, we now have a vast pipeline of targeted agents under pre-clinical and clinical development, potentially able to modify the natural history of the diverse disease spectrum of MDS. Here, we review the latest therapeutic approaches (investigational and approved agents) for MDS treatment. A deep insight will be given to molecularly targeted therapies by reviewing new agents for individualized precision medicine.

Clinical practice recommendation on hematopoietic stem cell transplantation for acute myeloid leukemia patients with FLT3-internal tandem duplication: a position statement from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

The FMS-like tyrosine kinase 3 (FLT3) gene is mutated in 25-30% of patients with acute myeloid leukemia (AML). Because of the poor prognosis associated with FLT3-internal tandem duplication mutated AML, allogeneic hematopoietic stem-cell transplantation (SCT) was commonly performed in first complete remission. Remarkable progress has been made in frontline treatments with the incorporation of FLT3 inhibitors and the development of highly sensitive minimal/measurable residual disease assays. Similarly, recent progress in allogeneic hematopoietic SCT includes improvement of transplant techniques, the use of haploidentical donors in patients lacking an HLA matched donor, and the introduction of FLT3 inhibitors as post-transplant maintenance therapy. Nevertheless, current transplant strategies vary between centers and differ in terms of transplant indications based on the internal tandem duplication allelic ratio and concomitant nucleophos-min-1 mutation, as well as in terms of post-transplant maintenance/consolidation. This review generated by international leukemia or transplant experts, mostly from the European Society for Blood and Marrow Transplantation, attempts to develop a position statement on best approaches for allogeneic hematopoietic SCT for AML with FLT3-internal tandem duplication including indications for and modalities of such transplants and on the potential optimization of post-transplant maintenance with FLT inhibitors.

Impact of numerical variation, allele burden, mutation length and co-occurring mutations on the efficacy of tyrosine kinase inhibitors in newly diagnosed FLT3- mutant acute myeloid leukemia

FLT3-ITD mutations in newly diagnosed acute myeloid leukemia (AML) are associated with worse overall survival (OS). FLT3-ITD diversity can further influence clinical outcomes. Addition of FLT3 inhibitors to standard chemotherapy has improved OS. The aim of this study is to evaluate the prognostic impact of FLT3 diversity and identify predictors of efficacy of FLT3 inhibitors. We reviewed prospectively collected data from 395 patients with newly diagnosed FLT3-ITD mutant AML. 156 (39%) patients received FLT3 inhibitors combined with either high or low intensity chemotherapy. There was no statistically significant difference in clinical outcomes among patients treated with FLT3 inhibitors based on FLT3 numerical variation (p = 0.85), mutation length (p = 0.67). Overall, the addition of FLT3 inhibitor to intensive chemotherapy was associated with an improved OS (HR = 0.35, 95% CI: 0.24-0.5, p = 0.0005), but not in combination with lower intensity chemotherapy (HR = 0.98, 95%CI: 0.7-1.36, p = 0.85). A differential effect of FLT3 inhibitor on OS was more pronounced in younger patients with FLT3 allelic ratio ≥0.5 (HR = 0.41, 95% CI: 0.25-0.66, p < 0.001), single ITD mutation (HR = 0.55, 95% CI: 0.34-0.88, p = 0.01), diploid cytogenetics (HR = 0.52, 95% CI: 0.35-0.76, p = 0.001), NPM1 co-mutation (HR = 0.35, 95% CI: 0.19-0.67, p = 0.001). Our analysis identifies predictors of survival among diverse FLT3 related variables in patients treated with FLT3 inhibitor.

Allogeneic Stem Cell Transplantation for FLT3-Mutated Acute Myeloid Leukemia: In vivo T-Cell Depletion and Posttransplant Sorafenib Maintenance Improve Survival. A Retrospective Acute Leukemia Working Party-European Society for Blood and Marrow Transplant Study

Acute myeloid leukemia (AML) with FLT3-mutation carries a poor prognosis, and allogeneic stem cell transplantation (allo-SCT) is recommended at first complete remission (CR1). We assessed 462 adults (median age 50 years) with FLT3-mutated AML allografted between 2010 and 2015 from a matched related (40%), unrelated (49%), or haploidentical donor (11%). The median follow-up of alive patients was 39 months. Day-100 acute graft versus host disease (GVHD) grades II–IV and III–IV were encountered in 26% and 9%, whereas the 2-year incidence of chronic and extensive chronic GVHD were 34% and 16%, respectively. The 2-year incidences of relapse and nonrelapse mortality were 34% and 15%, respectively. The 2-year leukemia-free survival, overall survival (OS), and GVHD relapse-free survival (GRFS) were 51%, 59%, and 38%, respectively. In multivariate analysis, NPM1-mutation, transplantation in CR1, in vivo T-cell depletion, and posttransplant sorafenib improved OS, whereas more than one induction (late CR1) negatively affected OS. Similarly, NPM1-mutation, a haploidentical donor, T-cell depletion, and sorafenib maintenance improved GRFS, whereas late CR1 or persistent disease negatively affected it. In conclusion, FLT3-mutated AML remains a challenge even following allo-SCT. In vivo T-cell depletion and posttransplant sorafenib significantly improve OS and GRFS, and may be considered as standard of care.

Discontinuation of sorafenib can lead to the emergence of FLT3-ITD-positive acute myeloid leukemia

A 69-year-old woman who had been diagnosed with unresectable papillary thyroid cancer was referred to our hospital. We initially treated her with sorafenib, but she subsequently developed erythema multiforme, which was suspected to be a drug rush due to sorafenib; therefore, sorafenib was discontinued. At the time of discontinuation, immature blast cells were detected in her peripheral blood. Approximately two weeks later, her skin rash improved substantially, but the proportion of blasts in the peripheral blood increased. We performed a bone marrow examination, and she was diagnosed with FLT3-ITD-positive acute myeloid leukemia. FLT3-ITD expression is found in 20-25% of AML and is a known independent poor prognostic factor. To overcome the poor prognosis associated with FLT3-ITD, molecular drugs targeting FLT3-ITD are attracting much attention. Sorafenib, a multi-kinase inhibitor, also has an effect on FLT3-ITD. Although primary disease flares after tyrosine kinase inhibitor discontinuation have been reported, this is the first report to describe discontinuation of sorafenib treatment as a potential trigger of FLT3-ITD-positive acute myeloid leukemia in papillary thyroid cancer.

Sorafenib Combined with 5-azacytidine in Older Patients with Untreated FLT3-ITD Mutated Acute Myeloid Leukemia

Based on our previous study of the combination of sorafenib with 5-azacytidine (AZA) in relapsed/refractory patients with FLT3 mutated acute myeloid leukemia (AML), we hypothesized that the combination would be efficacious and well tolerated in untreated patients with FLT3 mutated AML who are unsuitable for standard chemotherapy due to advanced age or lack of fitness. Newly diagnosed patients with untreated FLT3 mutated AML who underwent frontline therapy on 2 separate protocols of AZA plus sorafenib were analyzed. The clinical trials were registered at clinicaltrials.gov (NCT02196857 and NCT01254890). Overall, 27 patients with untreated FLT3 mutated AML (median age of 74 years, range, 61-86) were enrolled. The overall response rate was 78% (7 [26%] CR, 12 [44%] CRi/CRp, and 2 [7%] PR). Patients received a median of 3 treatment cycles (1-35). The median duration of CR/CRp/CRi is 14.5 months (1.1-28.7 months). Three (11%) responding patients (1 CR, 2 CRi) proceeded to allogeneic stem cell transplant. The median follow-up for surviving patients was 4.1 months (3.0-17.3 months). The median overall survival for the entire group was 8.3 months, and 9.2 months in the 19 responders. The regimen was well tolerated in elderly patients with untreated FLT3 mutated AML with no early deaths.

Use of FLT3 inhibitors in acute myeloid leukemia remission induction or salvage therapy: systematic review and meta-analysis

Background

Previous studies showed that FLT3 inhibitors played an important role in acute myeloid leukemia (AML) therapy. However, discrepancies remain regarding the association between FLT3 inhibitors use and prognosis of AML patients in clinical trials.

Aim

The aim of this study was to evaluate the effect of FLT3 inhibitors on the treatment of AML in a systematic review and meta-analysis.

Materials and methods

PubMed, Embase, and Cochrane Library databases were searched for studies published before August 2017 that used FLT3 inhibitors in AML. Fixed- and random-effect models were used, and between-study heterogeneity was assessed.

Results

A total of 26 studies fitting our inclusion and exclusion criteria were included. The FLT3 status of patients and main treatment outcomes including overall survival (OS), event-free survival (EFS), relapse-free survival (RFS), complete remission (CR), and overall response rate (ORR) after therapy were extracted. Five studies comparing addition of FLT3 inhibitors and placebo or blank control to chemotherapy were analyzed in Part I, showing improved OS (hazard ratio [HR]=0.86, 95% confidence interval [CI]=0.75–0.99, P=0.03) in the FLT3 inhibitor group but without a significant improvement on EFS (HR=0.86, 95% CI=0.62–1.21, P=0.39) and ORR (odds ratio [OR]=1.10, 95% CI=0.89–1.35, P=0.38). Twenty-one studies evaluating the benefit of using FLT3 inhibitors in different FLT3-type AML patients were analyzed in Part II, showing that FLT3–internal tandem duplication (ITD)-positive patients were more sensitive to FLT3 inhibitor treatment and achieved better CR (OR=1.89, 95% CI=1.06–3.37, P=0.03) and ORR (OR=3.07, 95% CI=2.13–4.43, P<0.001).

Conclusion

Our study showed that combined use of FLT3 inhibitors improved OS and that the FLT3 status of AML patients could affect their sensitivity to FLT3 inhibitors in terms of CR and ORR.

Molecular targeting in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogenous disease associated with distinct genetic and molecular abnormalities. Somatic mutations result in dysregulation of intracellular signaling pathways, epigenetics, and apoptosis of the leukemia cells. Understanding the basis for the dysregulated processes provides the platform for the design of novel targeted therapy for AML patients. The effort to devise new targeted therapy has been helped by recent advances in methods for high-throughput genomic screening and the availability of computer-assisted techniques for the design of novel agents that are predicted to specifically inhibit the mutant molecules involved in these intracellular events. In this review, we will provide the scientific basis for targeting the dysregulated molecular mechanisms and discuss the agents currently being investigated, alone or in combination with chemotherapy, for treating patients with AML. Successes in molecular targeting will ultimately change the treatment paradigm for the disease.

Treatment of Relapsed/Refractory Acute Myeloid Leukemia

OPINION STATEMENT

Approximately 40-45% of younger and 10-20% of older adults with acute myeloid leukemia (AML) will be cured with current standard chemotherapy. The outlook is particularly gloomy for patients with relapsed and/or refractory disease (cure rates no higher than 10%). Allogeneic hematopoietic stem cell transplantation (HSCT), the only realistic hope of cure for these patients, is an option for only a minority. In recent years, much has been learned about the genomic and epigenomic landscapes of AML, and the clonal architecture of both de novo and secondary AML has begun to be unraveled. These advances have paved the way for rational drug development as new "drugable" targets have emerged. Although no new drug has been approved for AML in over four decades, with the exception of gemtuzumab ozogamycin, which was subsequently withdrawn, there is progress on the horizon with the possible regulatory approval soon of agents such as CPX-351 and midostaurin, the Food and Drug Administration "breakthrough" designation granted to venetoclax, and promising agents such as the IDH inhibitors AG-221 and AG-120, the smoothened inhibitor glasdegib and the histone deacetylase inhibitor pracinostat. In our practice, we treat most patients with relapsed/refractory AML on clinical trials, taking into consideration their prior treatment history and response to the same. We utilize targeted sequencing of genes frequently mutated in AML to identify "actionable" mutations, e.g., in FLT3 or IDH1/2, and incorporate small-molecule inhibitors of these oncogenic kinases into our therapeutic regimens whenever possible. In the absence of actionable mutations, we rationally combine conventional agents with other novel therapies such as monoclonal antibodies and other targeted drugs. For fit patients up to the age of 65, we often use high-dose cytarabine-containing backbone regimens. For older or unfit patients, we prefer hypomethylating agent-based therapy. Finally, all patients with relapsed/refractory AML are evaluated for allogeneic HSCT.

Phosphoproteome Analysis Reveals Differential Mode of Action of Sorafenib in Wildtype and Mutated FLT3 Acute Myeloid Leukemia (AML) Cells

Constitutively activating internal tandem duplication (ITD) alterations of the receptor tyrosine kinase FLT3 (Fms-like tyrosine kinase 3) are common in acute myeloid leukemia (AML) and classifies FLT3 as an attractive therapeutic target. So far, applications of FLT3 small molecule inhibitors have been investigated primarily in FLT3-ITD⁺ patients. Only recently, a prolonged event-free survival has been observed in AML patients who were treated with the multikinase inhibitor sorafenib in addition to standard therapy. Here, we studied the sorafenib effect on proliferation in a panel of 13 FLT3-ITD⁻ and FLT3-ITD⁺ AML cell lines. Sorafenib IC50 values ranged from 0.001 to 5.6 μm, whereas FLT3-ITD⁺ cells (MOLM-13, MV4-11) were found to be more sensitive to sorafenib than FLT3-ITD⁻ cells. However, we identified two FLT3-ITD⁻ cell lines (MONO-MAC-1 and OCI-AML-2) which were also sorafenib sensitive. Phosphoproteome analyses revealed that the affected pathways differed in sorafenib sensitive FLT3-ITD⁻ and FLT3-ITD⁺ cells. In MV4-11 cells sorafenib suppressed mTOR signaling by direct inhibition of FLT3. In MONO-MAC-1 cells sorafenib inhibited the MEK/ERK pathway. These data suggest that the FLT3 status in AML patients might not be the only factor predicting response to treatment with sorafenib.

Emerging therapies for acute myeloid leukemia

Acute myeloid leukemia (AML) is characterized by clinical and biological heterogeneity. Despite the advances in our understanding of its pathobiology, the chemotherapy-directed management has remained largely unchanged in the past 40 years. However, various novel agents have demonstrated clinical activity, either as single agents (e.g., isocitrate dehydrogenase (IDH) inhibitors, vadastuximab) or in combination with standard induction/consolidation at diagnosis and with salvage regimens at relapse. The classes of agents described in this review include novel cytotoxic chemotherapies (CPX-351 and vosaroxin), epigenetic modifiers (guadecitabine, IDH inhibitors, histone deacetylase (HDAC) inhibitors, bromodomain and extraterminal (BET) inhibitors), FMS-like tyrosine kinase receptor 3 (FLT3) inhibitors, and antibody-drug conjugates (vadastuximab), as well as cell cycle inhibitors (volasertib), B-cell lymphoma 2 (BCL-2) inhibitors, and aminopeptidase inhibitors. These agents are actively undergoing clinical investigation alone or in combination with available chemotherapy.

Inefficiencies and Patient Burdens in the Development of the Targeted Cancer Drug Sorafenib: A Systematic Review

Failure in cancer drug development exacts heavy burdens on patients and research systems. To investigate inefficiencies and burdens in targeted drug development in cancer, we conducted a systematic review of all prelicensure trials for the anticancer drug, sorafenib (Bayer/Onyx Pharmaceuticals). We searched Embase and MEDLINE databases on October 14, 2014, for prelicensure clinical trials testing sorafenib against cancers. We measured risk by serious adverse event rates, benefit by objective response rates and survival, and trial success by prespecified primary endpoint attainment with acceptable toxicity. The first two clinically useful applications of sorafenib were discovered in the first 2 efficacy trials, after five drug-related deaths (4.6% of 108 total) and 93 total patient-years of involvement (2.4% of 3,928 total). Thereafter, sorafenib was tested in 26 indications and 67 drug combinations, leading to one additional licensure. Drug developers tested 5 indications in over 5 trials each, comprising 56 drug-related deaths (51.8% of 108 total) and 1,155 patient-years (29.4% of 3,928 total) of burden in unsuccessful attempts to discover utility against these malignancies. Overall, 32 Phase II trials (26% of Phase II activity) were duplicative, lacked appropriate follow-up, or were uninformative because of accrual failure, constituting 1,773 patients (15.6% of 11,355 total) participating in prelicensure sorafenib trials. The clinical utility of sorafenib was established early in development, with low burden on patients and resources. However, these early successes were followed by rapid and exhaustive testing against various malignancies and combination regimens, leading to excess patient burden. Our evaluation of sorafenib development suggests many opportunities for reducing costs and unnecessary patient burden in cancer drug development.

Management of Newly Diagnosed Acute Myeloid Leukemia in the Elderly: Current Strategies and Future Directions

The incidence of acute myeloid leukemia (AML) increases with age, and the majority of cases occur in adults aged >55 years. The prognosis of AML in older adults is generally poor; however, AML is a heterogeneous disease regardless of age, and prognosis depends on cytogenetic changes, genetic mutations, and patient characteristics. Several lines of evidence support offering treatment to the vast majority of older patients, and the survival benefit associated with this approach generally outweighs the risk of toxicity. Response and long-term survival using intensive induction regimens are significantly lower in older patients, although a small proportion of patients can achieve durable remissions. Selection of patients for intensive induction therapy requires comprehensive assessment of disease characteristics, performance status, and comorbidities. In unfit patients, options for treatment include hypomethylating agents, low-dose ara-C, or consideration of a clinical trial if available. The incorporation of novel therapies into treatment, such as FLT3 inhibitors and antibody-drug conjugates, offers significant promise in older patients, although, thus far, increased responses using novel agents have often not translated to improved survival outcomes. The development of reduced-intensity conditioning regimens and improvements in supportive care has increased the use of allogeneic stem cell transplant (ASCT) in older patients. Selection of patients for ASCT requires an estimation of the trade-off between toxicity and risk of relapse.

Linifanib (ABT-869) Potentiates the Efficacy of Chemotherapeutic Agents through the Suppression of Receptor Tyrosine Kinase-Mediated AKT/mTOR Signaling Pathways in Gastric Cancer

Gastric cancer, highly dependent on tumor angiogenesis, causes uncontrolled lethality, in part due to chemoresistance. Here, we demonstrate that linifanib (ABT-869), a novel multi-targeted receptor tyrosine kinase inhibitor, markedly augments cytotoxicity of chemotherapies in human gastric cancer. ABT-869 and chemotherapeutic agents exhibited a strong synergy to inhibit the viability of several gastric cancer cell lines, with combination index values ranging from 0.017 to 0.589. Additionally, the combination of ABT-869 and chemotherapeutic agents led to remarkable suppression of vascular endothelial growth factor (VEGF)-induced angiogenesis in vitro and in vivo. Importantly, in a preclinical gastric cancer xenograft mouse model, drug co-treatments led to increased mouse survival as well as a synergistic reduction in tumor size and the inhibition of tumor angiogenesis. Mechanistic studies further revealed that all of the co-treatments containing ABT-869 resulted in decreased activation of the VEGF receptor, the epidermal growth factor receptor and the insulin growth factor receptor. Inhibition of these receptor tyrosine kinases consequently attenuated the activation of the downstream AKT/mTOR signaling pathway both in cultured gastric cancer cells and in gastric cancer xenografts. Collectively, our findings suggest that the addition of ABT-869 to traditional chemotherapies may be a promising strategy for the treatment of human gastric cancer.

Decitabine and Sorafenib Therapy in FLT-3 ITD-Mutant Acute Myeloid Leukemia

BACKGROUND

Acute myeloid leukemia (AML) characterized by Feline McDonough Sarcoma-like tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations have poor outcomes. Treatment options are limited, because these mutations confer resistance to conventional chemotherapy. FLT-3 inhibitors such as sorafenib have been studied as a single agent and in combination with conventional chemotherapy or azacytidine with fair responses.

PATIENTS AND METHODS

Here we describe our preclinical and clinical experience with the combination of the DNA hypomethylating agent, decitabine and sorafenib for the treatment of FLT-3 ITD-mutant AML.

RESULTS

In vitro treatment of the human FLT-3 ITD-mutant AML cell line, MV4-11, with both drugs significantly improved growth inhibition over single-agent therapy and resulted in synergistic antitumor effects (combination index < 1). A case series of 6 patients treated with off protocol combination of decitabine and sorafenib demonstrated overall responses in 5 patients (83%) with a median survival of 155 days. Four of the 5 patients (80%) with relapsed/refractory AML achieved complete responses with incomplete count recovery. The combination was also well tolerated.

CONCLUSION

Further investigation is warranted to confirm these responses.

Molecular therapy for acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous disease that is, in general, associated with a very poor prognosis. Multiple cytogenetic and molecular abnormalities that characterize different forms of AML have been used to better prognosticate patients and inform treatment decisions. Indeed, risk status in patients with this disease has classically been based on cytogenetic findings; however, additional molecular characteristics have been shown to inform risk assessment, including FLT3, NPM1, KIT, and CEBPA mutation status. Advances in sequencing technology have led to the discovery of novel somatic mutations in tissue samples from patients with AML, providing deeper insight into the mutational landscape of the disease. The majority of patients with AML (>97%) are found to have a clonal somatic abnormality on mutational profiling. Nevertheless, our understanding of the utility of mutation profiling in clinical practice remains incomplete and is continually evolving, and evidence-based approaches to application of these data are needed. In this Review, we discuss the evidence-base for integrating mutational data into treatment decisions for patients with AML, and propose novel therapeutic algorithms in the era of molecular medicine.

A phase I/II study of sunitinib and intensive chemotherapy in patients over 60 years of age with acute myeloid leukaemia and activating FLT3 mutations

Acute myeloid leukaemia (AML) with FLT3 mutation has a dismal prognosis in elderly patients. Treatment with a combination of FLT3 inhibitors and standard chemotherapy has not been extensively studied. Therefore, we instigated a phase I/II clinical trial of chemotherapy with cytosine arabinoside (Ara-C)/daunorubicin induction (7+3) followed by three cycles of intermediate-dose Ara-C consolidation in 22 AML patients with activating FLT3 mutations. Sunitinib was added at predefined dose levels and as maintenance therapy for 2 years. At dose level 1, sunitinib 25 mg daily continuously from day 1 onwards resulted in two cases with dose-limiting toxicity (DLT), prolonged haemotoxicity and hand-foot syndrome. At dose level -1, sunitinib 25 mg was restricted to days 1-7 of each chemotherapy cycle. One DLT was observed in six evaluable patients. Six additional patients were treated in an extension phase. Thirteen of 22 patients (59%; 8/14 with FLT3-internal tandem duplication and 5/8 with FLT3-tyrosine kinase domain) achieved a complete remission/complete remission with incomplete blood count recovery. For the 17 patients included at the lower dose level, median overall, relapse-free and event-free survival were 1·6, 1·0 and 0·4 years, respectively. Four out of five analysed patients with relapse during maintenance therapy lost their initial FLT3 mutation, suggesting outgrowth of FLT3 wild-type subclones.

Sorafenib Maintenance Appears Safe and Improves Clinical Outcomes in FLT3-ITD Acute Myeloid Leukemia After Allogeneic Hematopoietic Cell Transplantation

BACKGROUND

The FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) gene is one of the most frequently observed genetic alterations in acute myeloid leukemia (AML), with an incidence of about 20% to 30%. FLT3-ITD is significantly associated with a poor outcome, and offering an allogeneic hematopoietic cell transplantation (allo-HCT) is recommended for patients harboring this mutation. Sorafenib is a tyrosine kinase inhibitor active against RAF, VEGF, and FLT3-ITD. It has been used in an off-label fashion in FLT3-ITD AML.

PATIENTS AND METHODS

We retrospectively assessed the successful use of sorafenib after allo-HCT in patients with FLT3-ITD AML. Six FLT3-ITD AML patients received sorafenib as posttransplantation maintenance therapy (n = 5) or as salvage therapy after a post-allo-HCT relapse (n = 1) and continued afterward.

RESULTS

One patient developed myocardial infarction 100 days after initiation of sorafenib. Interestingly, skin graft versus host disease (grade II) was observed in 5 of 6 patients and generally occurred within few days after initiation of sorafenib, but it responded promptly to corticosteroid therapy in all patients. All 6 patients were alive and in complete remission at a median follow-up of 16 months (range, 10-29 months) since first induction and at a median follow-up of 12 months (range, 4-20 months) since initiation of sorafenib. Remarkably, the disease of all patients was in molecular remission.

CONCLUSION

Sorafenib appears to be an effective maintenance therapy after allo-HCT in FLT3-ITD AML, with achievement of durable complete responses. This suggests an immunomodulatory effect of sorafenib in the posttransplantation setting and warrants a broader clinical evaluation of the use of maintenance sorafenib in FLT3-ITD AML.

Phase I trial of maintenance sorafenib after allogeneic hematopoietic stem cell transplantation for fms-like tyrosine kinase 3 internal tandem duplication acute myeloid leukemia

The fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutation is associated with a high relapse rate for patients with acute myeloid leukemia (AML) even after allogeneic hematopoietic stem cell transplantation (HSCT). Sorafenib is a tyrosine kinase inhibitor, which inhibits the FLT3 tyrosine kinase and has shown encouraging activity in FLT3-ITD AML. We conducted a phase I trial of maintenance sorafenib after HSCT in patients with FLT3-ITD AML (ClinicalTrials.govNCT01398501). Patients received a variety of conditioning regimens and graft sources. A dose escalation 3 + 3 cohort design was used to define the maximum tolerated dose (MTD), with an additional 10 patients treated at the MTD. Sorafenib was initiated between days 45 and 120 after HSCT and continued for 12 28-day cycles. Twenty-two patients were enrolled (status at HSCT: first complete remission [CR1], n = 16; second complete remission [CR2], n = 3; refractory, n = 3). The MTD was established at 400 mg twice daily with 1 dose-limiting toxicity (DLT) observed (pericardial effusion). Two patients died of transplantation-related causes, both unrelated to sorafenib. Two patients stopped sorafenib after relapse and 5 stopped because of attributable toxicities after the DLT period. Median follow-up for surviving patients is 16.7 months after HSCT (range, 8.1 to 35.0). There was 1 case of grade II acute graft-versus-host disease (GVHD) after starting sorafenib and the 12-month cumulative incidence of chronic GVHD was 38% (90% confidence interval [CI], 21% to 56%). For all patients, 1-year progression-free survival (PFS) was 85% (90% CI, 66% to 94%) and 1-year overall survival (OS) was 95% (90% CI, 79% to 99%) after HSCT. For patients in CR1/CR2 before HSCT (n = 19), 1-year PFS was 95% (90% CI, 76% to 99%) and 1-year OS was 100%, with only 1 patient who relapsed. Sorafenib is safe after HSCT for FLT3-ITD AML and merits further investigation for the prevention of relapse.

Sorafenib: targeting multiple tyrosine kinases in cancer

Sorafenib (BAY 43-9006, Nexavar®) is an oral multiple tyrosine kinase inhibitor. Main targets are receptor tyrosine kinase pathways frequently deregulated in cancer such as the Raf-Ras pathway, vascular endothelial growth factor (VEGF) pathway, and FMS-like tyrosine kinase 3 (FLT3). Sorafenib was approved by the FDA in fast track for advanced renal cell cancer and hepatocellular cancer and shows good clinical activity in thyroid cancer. Multiple clinical trials are undertaken to further investigate the role of sorafenib alone or in combination for the treatment of various tumor entities.

Rapid induction of complete molecular remission by sequential therapy with LDAC and sorafenib in FLT3-ITD-positive patients unfit for intensive treatment: two cases and review of the literature

Treatment of acute myeloid leukemia remains a therapeutic challenge. Even in younger patients with a low rate of co-morbidities less than 50% of patients can be cured. For older patients or patients with significant co-morbidities, the situation appears even worse. In patients not eligible for intensive treatment approaches - e.g. due to underlying medical conditions - therapeutic approaches remain almost exclusively palliative. However, even with less intense treatment approaches, temporary remission can be achieved and this contributes to prolonged survival and improved quality of life of the respective patient. Targeted therapies have been widely used as palliative treatment in- and outside clinical trials as single agents. Combination with low-dose cytarabine (LDAC) potentially improves remission rates and can be safely administered in an outpatient setting.Previous studies showed that additive hematologic toxicity of combinatory therapeutic approaches may arise from simultaneous treatment (e.g. chemotherapy plus targeted therapies). However, sequential therapies have already proven their feasibility in clinical trials. Here, we report two cases of rapid induction of complete molecular remission by sequential therapy with LDAC and sorafenib in patients unfit for intensive chemotherapy without significant long-term toxicity.

FLT3 inhibitors for acute myeloid leukemia: a review of their efficacy and mechanisms of resistance

Since the Food and Drug Administration approval of imatinib for treatment of chronic myeloid leukemia in 2001, tyrosine kinase inhibitors (TKIs) have become a mainstay in the care of many malignancies. In acute myeloid leukemia (AML), activating mutations in the FMS-like tyrosine kinase 3 (FLT3) gene result in survival and proliferation of leukemic blasts and are associated with adverse prognosis. Therefore, the FLT3 receptor is an appealing target for inhibition. Multiple small molecule TKIs are currently in development for FLT3-mutated AML, and agents are beginning to show promising efficacy. In other malignancies, the development of resistance to TKIs during the course of therapy has proven to be a challenge, and thus far, in clinical trials of FLT3 TKIs, resistance to inhibition represents a significant barrier to successful FLT3 inhibition. Understanding the mechanisms of resistance and overcoming these obstacles to target inhibition will be central to the success of these agents.

High-risk acute myelogenous leukemia: treatment today ... and tomorrow

High-risk acute myelogenous leukemia (AML) constitutes a distinct subset of disease based on clinical and biological characteristics and comprises a significant percentage of all cases of adult AML. Biologic features such as distinct clonal cytogenetic and molecular abnormalities identify a subgroup of AML patients characterized by poor response to induction chemotherapy and poor long-term survival after treatment with consolidation chemotherapy. Clinical variables that predict for poor response include AML relapsed after less than 1 year of remission and AML characterized by resistance to conventional agents. We review here our understanding of the defining biologic subtypes of AML and discuss how adequate initial evaluation can be used to inform the choice of treatment. By defining high-risk biologic and clinical variables, a strong case can be made for treating patients with investigational agents, with treatment directed at distinct cytogenetic or molecular abnormalities. Allogeneic transplantation is the only form of therapy available outside of the setting of a clinical trial that may offer a chance for long-term survival for patients with high-risk AML.