Limited Single-agent Efficacy Research Articles

Synergy of retinoic acid and BH3 mimetics in MYC(N)-driven embryonal nervous system tumours

BackgroundCertain paediatric nervous system malignancies have dismal prognoses. Retinoic acid (RA) is used in neuroblastoma treatment, and preclinical data indicate potential benefit in selected paediatric brain tumour entities. However, limited single-agent efficacy necessitates combination treatment approaches.MethodsWe performed drug sensitivity profiling of 76 clinically relevant drugs in combination with RA in 16 models (including patient-derived tumouroids) of the most common paediatric nervous system tumours. Drug responses were assessed by viability assays, high-content imaging, and apoptosis assays and RA relevant pathways by RNAseq from treated models and patient samples obtained through the precision oncology programme INFORM (n = 2288). Immunoprecipitation detected BCL-2 family interactions, and zebrafish embryo xenografts were used for in vivo efficacy testing.ResultsGroup 3 medulloblastoma (MBG3) and neuroblastoma models were highly sensitive to RA treatment. RA induced differentiation and regulated apoptotic genes. RNAseq analysis revealed high expression of BCL2L1 in MBG3 and BCL2 in neuroblastomas. Co-treatments with RA and BCL-2/XL inhibitor navitoclax synergistically decreased viability at clinically achievable concentrations. The combination of RA with navitoclax disrupted the binding of BIM to BCL-XL in MBG3 and to BCL-2 in neuroblastoma, inducing apoptosis in vitro and in vivo.ConclusionsRA treatment primes MBG3 and NB cells for apoptosis, triggered by navitoclax cotreatment.

Phase II Study of Ulixertinib in Children and Young Adults With Tumors Harboring Activating Mitogen-Activated Protein Kinase Pathway Alterations: APEC1621J of the National Cancer Institute-Children's Oncology Group Pediatric MATCH Trial.

The National Cancer Institute-Children's Oncology Group (NCI-COG) Pediatric MATCH trial assigns patients age 1-21 years with refractory malignancies to phase II treatment arms of molecularly targeted therapies on the basis of genetic alterations detected in their tumor. Patients with activating alterations in the mitogen-activated protein kinase pathway were treated with ulixertinib, an extracellular signal-regulated kinase (ERK)1/2 inhibitor. As there were no previous pediatric data, ulixertinib was initially tested in a dose escalation cohort to establish the recommended phase II dose (RP2D) before proceeding to the phase II cohort. Ulixertinib was administered at 260 mg/m2/dose orally twice a day (dose level 1 [DL1], n = 15) or 350 mg/m2/dose orally twice a day (DL2, n = 5). The primary end point was objective response rate; secondary end points included safety/tolerability and progression-free survival (PFS). Twenty patients (median 12 years; range, 5-20) were treated, all evaluable for response. CNS tumors comprised 55% (11/20) of diagnoses, with high-grade glioma and low-grade glioma most common (n = 5 each). All CNS tumors except one harbored BRAF fusions or V600E mutations. Rhabdomyosarcoma (n = 5) was the most frequent non-CNS diagnosis. DL1 was declared the RP2D in the dose escalation cohort after dose-limiting toxicities in Cycle 1 occurred in 1/6 patients at DL1 and 2/5 patients at DL2, including fatigue, anorexia, rash, nausea, vomiting, diarrhea, dehydration, hypoalbuminemia, and hypernatremia. No objective responses were observed. Six-month PFS was 37% (95% CI, 17 to 58). Three patients with BRAF-altered CNS tumors achieved stable disease >6 months. Ulixertinib, a novel targeted agent with no previous pediatric data, was successfully evaluated in a national precision medicine basket trial. The pediatric RP2D of ulixertinib is 260 mg/m2/dose orally twice a day. Limited single-agent efficacy was observed in a biomarker-selected cohort of refractory pediatric tumors.

Response to BRAF-targeted Therapy Is Enhanced by Cotargeting VEGFRs or WNT/β-Catenin Signaling in BRAF-mutant Colorectal Cancer Models.

The fact that 10% of colorectal cancer tumors harbor BRAF V600E mutations suggested targeting BRAF as a potential therapy. However, BRAF inhibitors have only limited single-agent efficacy in this context. The potential for combination therapy has been shown by the BEACON trial where targeting the EGF receptor with cetuximab greatly increased efficacy of BRAF inhibitors in BRAF-mutant colorectal cancer. Therefore, we explored whether efficacy of the mutant BRAF inhibitor vemurafenib could be enhanced by cotargeting of either oncogenic WNT/β-catenin signaling or VEGFR signaling. We find the WNT/β-catenin inhibitors pyrvinium, ICG-001 and PKF118-310 attenuate growth of colorectal cancer cell lines in vitro with BRAF-mutant lines being relatively more sensitive. Pyrvinium combined with vemurafenib additively or synergistically attenuated growth of colorectal cancer cell lines in vitro. The selective and potent VEGFR inhibitor axitinib was most effective against BRAF-mutant colorectal cancer cell lines in vitro, but the addition of vemurafenib did not significantly increase these effects. When tested in vivo in animal tumor models, both pyrvinium and axitinib were able to significantly increase the ability of vemurafenib to attenuate tumor growth in xenografts of BRAF-mutant colorectal cancer cells. The magnitude of these effects was comparable with that induced by a combination of vemurafenib and cetuximab. This was associated with additive effects on release from tumor cells and tumor microenvironment cell types of substances that would normally aid tumor progression. Taken together, these preclinical data indicate that the efficacy of BRAF inhibitor therapy in colorectal cancer could be increased by cotargeting either WNT/β-catenin or VEGFRs with small-molecule inhibitors.

MODL-15. High-throughput combination drug screening identifies synergism between retinoic acid treatment and BCL-XL-inhibition in MYC(N)-driven medulloblastoma and neuroblastoma models

Abstract PURPOSE: Despite remarkable improvements in childhood cancer survival, certain high-risk entities including malignancies of the nervous system still carry dismal prognoses. Retinoic acid (RA) treatment has long been administered in high-risk neuroblastoma patients and preclinical data suggest a benefit in applying retinoids in selected brain tumor entities. However, limited single-agent efficacy and developing treatment resistance provide a rationale for investigating improved combination treatments. METHODS: We assessed the RA sensitivity of 16 cell lines and patient-derived cultures of pediatric nervous system tumors from the INFORM (INdividualized Therapy FOr Relapsed Malignancies in Childhood) registry. Bulk RNA sequencing was performed for five sensitive models undergoing RA treatment. All models were screened for drug sensitivity to 76 clinically relevant drugs alone and combined with RA. Beneficial hit combinations were further investigated for synergy, as well as their effect on differentiation and apoptosis by high-content fluorescence microscopy and caspase activity assay. Results from in vivo experiments are pending. RESULTS: Group 3 medulloblastoma and high-risk neuroblastoma models were most sensitive to RA treatment leading to significant changes in gene expression of apoptotic regulation. Drug sensitivity screening revealed similar patterns of response to combination treatments in MYC-driven Group 3 medulloblastomas and MYCN-amplified neuroblastomas. Apoptosis regulating BCL-XL-inhibitors (A-1155463, navitoclax) were identified as top hits across RA sensitive models, whereas epigenetic BET family inhibitor I-BET151 and histone deacetylase inhibitor entinostat suggested entity-specific combination benefits in neuroblastoma and medulloblastoma models, respectively. In both entities, combining RA with navitoclax was synergistic and significantly increased caspase-3 activity. The combination led to a morphological shift from differentiation under RA treatment to cell death. CONCLUSION: Exploring combinations for RA treatment in pediatric nervous system tumors, we found that MYC(N)-driven medulloblastoma and neuroblastoma not only share responsiveness to RA treatment, but also demonstrate enhanced vulnerability in combination with BCL-XL-inhibition resulting in increased apoptosis.

Checkpoint Inhibitors in Multiple Myeloma: Intriguing Potential and Unfulfilled Promises.

Simple SummaryMultiple myeloma (MM) is a hematological malignancy caused by aberrations in the plasma cell development, resulting in uncontrolled production of plasma cells and or monoclonal proteins. Currently, several treatments are centered around immune-based therapies including immunomodulatory agents, monoclonal antibodies, cellular therapies, and stem cell transplantation. We review the biologic rationale, efficacy, side effects, and limitations of immune-checkpoint inhibitors (ICIs), which have been successful in several solid organ malignancies such as melanoma, kidney, and lung cancers. Recent clinical trials evaluating ICIs as monotherapy and in combination with approved pharmaceutical drugs in MM, have thus far remained underwhelming due to excessive side effects and lack of efficacy in aggressive and advanced cases. There may be a role for ICIs in early forms of MM and preventing recurrence once achieving remission. Side effect mitigation and improved efficacy to combat resistance are needed prior to profoundly impacting the current MM landscape. Clinical studies to answer these questions are ongoing, and we eagerly await this data to determine if ICIs will become a permanent fixture in MM.Immune dysregulation and alteration of the bone marrow microenvironment allowing plasma cells to escape immune surveillance are well-known factors associated with the proliferation of clonal plasma cells and development of multiple myeloma (MM). Whilst immunotherapeutic approaches are now commonplace in a wide spectrum of malignancies, this aberration of myeloma development gives rise to the biological rationale for the use of immune checkpoint inhibitors (ICIs) in MM. However, the initial experience with these agents has been challenging with limited single agent efficacy, significant toxicity, and side effects. Herein, we review the biological and immunological aspects of MM and ICIs. We discuss the basic biology of immune checkpoint inhibitors, mechanisms of resistance, and drug failure patterns, review the published clinical trial data for ICIs in MM, and look towards the future of ICIs for MM treatment.

PARP1 Inhibition Radiosensitizes Models of Inflammatory Breast Cancer to Ionizing Radiation.

Sustained locoregional control of disease is a significant issue in patients with inflammatory breast cancer (IBC), with local control rates of 80% or less at 5 years. Given the unsatisfactory outcomes for these patients, there is a clear need for intensification of local therapy, including radiation. Inhibition of the DNA repair protein PARP1 has had little efficacy as a single agent in breast cancer outside of studies restricted to patients with BRCA mutations; however, PARP1 inhibition (PARPi) may lead to the radiosensitization of aggressive tumor types. Thus, this study investigates inhibition of PARP1 as a novel and promising radiosensitization strategy in IBC. In multiple existing IBC models (SUM-149, SUM-190, MDA-IBC-3), PARPi (AZD2281-olaparib and ABT-888-veliparib) had limited single-agent efficacy (IC50 > 10 μmol/L) in proliferation assays. Despite limited single-agent efficacy, submicromolar concentrations of AZD2281 in combination with RT led to significant radiosensitization (rER 1.12-1.76). This effect was partially dependent on BRCA1 mutational status. Radiosensitization was due, at least in part, to delayed resolution of double strand DNA breaks as measured by multiple assays. Using a SUM-190 xenograft model in vivo, the combination of PARPi and RT significantly delays tumor doubling and tripling times compared with PARPi or RT alone with limited toxicity. This study demonstrates that PARPi improves the effectiveness of radiotherapy in IBC models and provides the preclinical rationale for the opening phase II randomized trial of RT ± PARPi in women with IBC (SWOG 1706, NCT03598257).

Abstract 3924: PARP inhibition as a radiosensitizing strategy to improve locoregional control in inflammatory breast cancer

Abstract Purpose: Sustained locoregional control of disease is a significant issue in patients with inflammatory breast cancer (IBC) with local control rates <70% at 5 years in these patients. Given the unsatisfactory outcomes, there is a clear need for intensification of local therapy, including radiation, for these patients. Inhibition of poly(adenosine diphosphate-ribose) polymerase 1 (PARP1), a DNA repair protein, represents a novel and promising strategy for radiosensitizing aggressive tumors. The purpose of this study was to investigate radiosensitization by PARP1 inhibition in IBC and to determine the mechanism of radiosensitization. Methods: Pharmacologic PARP1 inhibitors, olaparib and veliparib, were used at various concentrations (10-5 to 10-12 M). Proliferation assays were used to determine the IC50s of these inhibitors in three independent IBC cell lines (SUM 149, SUM 190, MDA-IBC-3). Clonogenic survival assays were used to determine the radiosensitization in cell lines after pharmacologic PARP inhibition (PARPi). DNA damage was quantified using γH2AX staining in IBC cell lines. Transcriptomic, protein and signaling pathway changes were measured using RNA-Seq and RPPA, respectively. In vivo tumor growth was also measured in CB17-SCID mice with varying control and treatment groups (16-20 tumors/group) that included radiation (RT) alone, olaparib alone, and RT+olaparib. Results: PARPi via olaparib and veliparib had limited single agent efficacy in all three independent IBC models with IC50 values >10 µM. Despite limited single agent efficacy, sub micromolar concentrations of PARPi with RT led to significant radiosensitization with radiation enhancement ratios of 1.20-1.35 in the same three models (500 nM in SUM 190, 500 nM in MDA-IBC-3, 2 nM in SUM 149). This effect was partially dependent on BRCA 1/2 mutational status. Radiosensitization was due, at least in part, to delayed resolution of double strand DNA (dsDNA) breaks at 12, 16, and 24 hours in all models. Additionally, this effect is mediated, at least in part, by a non-homologous end joining (NHEJ) mechanism and was not dependent on homologous recombination (HR). RNA-Seq and RPPA protein pathway data identify key pathways that regulate the radiosensitization in these IBC models. Additionally, xenograft studies show significant differences in tumor doubling and tripling times between treated and untreated tumors. Conclusion: Our study demonstrates that the PARP1 inhibition improves the therapeutic index of radiotherapy in IBC cell lines. Combined PARPi with RT leads to unresolved dsDNA breaks and decreased clonogen survival. These studies provide the rationale for a phase II randomized trial of RT +/- PARPi (olaparib) in women with IBC that has recently opened for accrual (SWOG 1706 - NCT03598257). This work was supported by a grant from Komen for the Cure and NIH T-32-GM007315. Citation Format: Anna Michmerhuizen, Andrea Pesch, Leah Moubadder, Meleah Cameron, Amanda Zhang, Nicole Hirsh, Meilan Liu, Kari Wilder-Romans, Lori J. Pierce, Reshma Jagsi, Corey Speers. PARP inhibition as a radiosensitizing strategy to improve locoregional control in inflammatory breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3924.

Abstract 5814: Synthetic lethal therapy to overcome resistance to AURKA inhibition in HPV-negative head and neck cancer

Abstract Head and neck squamous cell carcinomas (HNSCC) affect more than a half million people annually worldwide. Most currently available treatments, which include cisplatin and irradiation, are associated with significant morbidity, while many targeted inhibitors show limited single agent efficacy: novel therapeutic approaches which combine efficacy and limited toxicity are needed. The most common mutational event in human papillomavirus (HPV)-negative HNSCC is mutation of TP53. As control of the G1/S transition is entirely p53-dependent, cells with TP53 mutations lose the G1/S checkpoint, and evade radiation- and cisplatin-induced cellular senescence. Targeting the serine/threonine mitotic kinase Aurora-A (AURKA) emerged as a promising synthetic lethal approach in this setting. AURKA is negatively regulated by p53, which causes upregulation of AURKA in the majority of cases of HNSCC, correlating with poor prognosis and cisplatin resistance. The single agent AURKA inhibitor MLN8237 (alisertib) had a 9% monotherapy response rate in treatment-refractory HNSCC, with all responses occurring in HPV-negative or -unknown disease. In our study, we used initial high throughput screening in multiple genomically characterized HNSCC cell lines to identify synergistic combinations involving AURKA inhibitors and 20 other inhibitors of cell cycle, and cell cycle checkpoint controls. This work has identified has several effective combinations, particularly in between alisertib (targeting AURKA), danusertib (AURKA and AURKB), LY2606368/prexasertib (CHK1), and reversine (MPS1). Multiplexing analysis with measures of cell metabolism, direct visualization of mitotic nuclei, and additional assays has allowed us to dissect distinct execution points for different drug combinations. We will describe in detail mechanistic interactions between specific combinations of value for HNSCC. These drug combinations are likely to represent a new and effective modality for treating TP53-mutated cancers. Citation Format: Alexander Y. Deneka, Margret B. Einarson, Jong Woo Lee, Anna S. Nikonova, Barbara Burtness, Erica A. Golemis. Synthetic lethal therapy to overcome resistance to AURKA inhibition in HPV-negative head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5814.

Abstract 157: Targeting distinct nodes of the PI3K/AKT/mTOR cascade in prostate cancer cells: impact on cell proliferation, apoptosis and pathway signaling

Abstract Inactivation of the PTEN gene is a common event in PCa, leading to activation of the PI3K/AKT/mTOR pathway and promoting PCa progression. Inhibitors targeting this pathway are currently being developed as anticancer agents. While recent clinical trials with mTORC1 inhibitors have shown limited single-agent efficacy in castration-resistant prostate cancer (CRPC), it is still not known whether targeting alternative nodes of the PI3K/AKT/mTOR cascade may improve response. The current study aimed to characterize the response of PCa cell lines to multiple inhibitors targeting the PI3K, AKT and mTOR nodes of the cascade and identify possible mechanisms of resistance. The impact of the different PI3K/AKT/mTOR inhibitors on cell proliferation and apoptosis was measured by WST-1 and ApoTox-Glo assays, respectively, in a broad panel of established PCa cell lines and primary cell cultures generated from patient-derived xenografts. PTEN-negative PCa cell lines showed strong response to PI3Kβ/δ, AKT and mTOR inhibition, whereas PTEN-positive cells were resistant to PI3Kβ/δ and showed variable sensitivity to mTOR inhibitors. MTORC1 inhibitor showed low IC50 but reached plateau at about 70-80% growth inhibition. In contrast, mTORC1/2 inhibitor could reach complete growth inhibition at ~1μM concentration, in sensitive cell lines. Furthermore, treatment with PI3K or AKT inhibitor in combination with androgen depletion induced apoptosis in various PTEN-negative models, which is consistent with previously reported synergistic effect of PI3K/AKT and androgen receptor co-targeting. The effect of the inhibitors on phosphorylation of PI3K downstream targets (AKT, PRAS40, GSK3, S6K1 and 4EBP1) was analyzed by phospho-specific western blotting. Perturbation of different nodes of the PI3K/AKT/mTOR cascade resulted in differential phosphorylation of downstream targets, but there was no evident correlation with in vitro growth inhibition. In conclusion, the current study validates PI3Kβ and AKT as alternative targets in PTEN-negative PCa, whereas PTEN-positive models showed preferential yet variable responses towards mTOR inhibitors. Citation Format: Rute B. Marques, Ashraf Aghai, Wendy Stam, Wytske M. van Weerden. Targeting distinct nodes of the PI3K/AKT/mTOR cascade in prostate cancer cells: impact on cell proliferation, apoptosis and pathway signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 157. doi:10.1158/1538-7445.AM2017-157

Oncogenic Receptor Tyrosine Kinases Directly Phosphorylate Focal Adhesion Kinase (FAK) as a Resistance Mechanism to FAK-Kinase Inhibitors.

Focal adhesion kinase (FAK) is a major drug target in cancer and current inhibitors targeted to the ATP-binding pocket of the kinase domain have entered clinical trials. However, preliminary results have shown limited single-agent efficacy in patients. Despite these unfavorable data, the molecular mechanisms that drive intrinsic and acquired resistance to FAK-kinase inhibitors are largely unknown. We have demonstrated that receptor tyrosine kinases (RTK) can directly bypass FAK-kinase inhibition in cancer cells through phosphorylation of FAK's critical tyrosine 397 (Y397). We also showed that HER2 forms a direct protein-protein interaction with the FAK-FERM-F1 lobe, promoting direct phosphorylation of Y397. In addition, FAK-kinase inhibition induced two forms of compensatory RTK reprogramming: (i) the rapid phosphorylation and activation of RTK signaling pathways in RTKHigh cells and (ii) the long-term acquisition of RTKs novel to the parental cell line in RTKLow cells. Finally, HER2 +: cancer cells displayed resistance to FAK-kinase inhibition in 3D growth assays using a HER2 isogenic system and HER2+ cancer cell lines. Our data indicate a novel drug resistance mechanism to FAK-kinase inhibitors whereby HER2 and other RTKs can rescue and maintain FAK activation (pY397) even in the presence of FAK-kinase inhibition. These data may have important ramifications for existing clinical trials of FAK inhibitors and suggest that individual tumor stratification by RTK expression would be important to predict patient response to FAK-kinase inhibitors. Mol Cancer Ther; 15(12); 3028-39. ©2016 AACR.

Decitabine and sorafenib therapy in FLT3-ITD mutant acute myeloid leukemia- A case series

216 DECITABINE AND SORAFENIB THERAPY IN FLT3-ITD MUTANT ACUTE MYELOID LEUKEMIAA CASE SERIES Monica R. Muppidi1, Elizabeth A. Griffiths1, James E. Thompson1, Laurie A. Ford1, Craig W. Freyer2, Meir Wetzler1, Eunice S. Wang1 1Department of Medicine, 2Department of Pharmacy, Roswell Park Cancer Institute, Buffalo, NY Introduction: Patients with acute myeloid leukemia (AML) characterized by FMS-like tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations have poor outcomes, especially in the relapsed setting. Although small molecule inhibitors of FLT3 have been explored for these patients, many have demonstrated limited single-agent efficacy with short response durations. Sorafenib, a multi-kinase inhibitor with activity against FLT-3, has previously been evaluated alone and in combination with induction chemotherapy or azacytidine in AML patients. Here we describe our experience with the combination of the DNA hypomethylating agent, decitabine (D), and sorafenib (S) for the treatment of FLT-3 ITD mutant AML. Methods: We retrospectively reviewed records of patients with FLT-3 ITD mutant AML who were treated off protocol with D and S from 2011-present. Descriptive statistics, treatment response, and overall survival were recorded. Results: Six patients were identified. Mean age was 56 (range 34-70) years. Two-thirds (4/6) were female. All patients received at least 1-2 cycles of concurrent D 20 mg/m2 for 10 days and S 200-400 mg twice a day for 28 days. Five patients had relapsed/refractory AML (RR-AML) following 1-3 prior therapies. One patient had de novo AML in complete remission with incomplete count recovery (CRi) and received DS as consolidation. Overall response rate was 83%. Eighty percent (4/5) of patients with RR-AML attained CRi. One patient receiving DS consolidation attained complete remission (CR). Two patients received subsequent allogeneic stem cell transplantation. FLT3-ITD allelic ratio (available on 3 patients) decreased after DS therapy and correlated with CRi. Median overall survival was 111 days (range 62-348) from the initiation of DS to death from any cause or last known follow-up. Two patients developed treatment-related neutropenic sepsis and elevated liver enzymes which did not require dose adjustment. One patient developed heart failure of uncertain etiology. Conclusions: In this single institute case series, we demonstrated that the combination of D(10 days) and S was well tolerated, resulted in high CR/CRi rates (80%), and prolonged overall survival in patients with heavily pretreated relapsed/refractory FLT-3 ITD mutant AML. Further investigation of this regimen in clinical trials is warranted.

Decitabine and Sorafenib Therapy in Patients with FLT3-ITD Mutant Acute Myeloid Leukemia Is Associated with High Response Rates—a Single Institute Experience

Introduction: Patients with acute myeloid leukemia (AML) characterized by FMS-like tyrosine kinase-3 (FLT-3) internal tandem duplication (ITD) mutations have poor outcomes, especially in the relapsed setting. Although small molecule inhibitors of FLT-3 have been explored for these patients, many inhibitors have demonstrated limited single-agent efficacy with short response durations. Sorafenib, a multi-kinase inhibitor with activity against FLT-3, has previously been evaluated alone and in combination with induction chemotherapy or azacytidine in AML patients. Here we describe our experience with the combination of the DNA hypomethylating agent, decitabine (D), and sorafenib (S) for the treatment of FLT-3 ITD mutant AML.Methods: We retrospectively reviewed records of patients with FLT-3 ITD mutant AML who were treated off protocol with decitabine and sorafenib from 2011-present. Descriptive statistics, treatment response, and overall survival were recorded.Results: A total of six patients were identified. Mean age was 56 (range 34-70) years. Two-thirds (4/6) were female. All patients were confirmed to have recurrence of de novo AML characterized by FLT-3 ITD mutations prior to therapy. Patients received at least 1-2 cycles of concurrent decitabine 20 mg/m2 for 10 days and sorafenib 200-400 mg twice a day for 28 days. Five patients had relapsed/refractory AML (RR-AML) following 1-3 prior therapies. One patient had de novo AML in complete remission with incomplete count recovery (CRi) and received DS as consolidation. The overall response rate was 83%. Eighty percent (4/5) of patients with RR-AML attained CRi. One patient receiving DS consolidation attained complete remission (CR). Two patients received subsequent allogeneic stem cell transplantation with one individual still alive after 348 days. FLT3 ITD allelic ratio (available on 3 patients) decreased after DS therapy and correlated with CRi. Median overall survival was 111 days (range 59-348) from the initiation of DS to death from any cause or last known follow-up. Two patients developed treatment-related neutropenic fever/sepsis and elevated liver enzymes, respectively, which did not require dose adjustment. One patient developed heart failure of uncertain etiology.Conclusions: In this single institute case series, we demonstrated that the combination of decitabine (10 days) and sorafenib was well tolerated, resulted in high CR/CRi rates (80%), and prolonged overall survival in patients with heavily pretreated relapsed/refractory FLT-3 ITD mutant AML. Further investigation of this regimen in clinical trials is warranted.Table 1:Case seriesPatientAge(years)SexNo. of Prior therapiesPriorAlloSCT *Blasts Prior to DS (%)No. of DSCyclesResponseto therapyOverall survival (Days)154Female3NBM 70%1CRi141270Female1NPB 53%2CRi82364Male1NBM 68%2CRi62460Male1NBM 2%1CR198534Female3YPB 48%1NR348658Female3YNA2CRi59 [Display omitted] *Allogeneic stem cell transplantation DisclosuresOff Label Use: We are going to discuss the use of decitabine and sorafenib combination in relapsed/refractory FLT3 mutant AML. Decitabine is a DNA hypomethylating agent and sorafenib is a multikinase inhibitor, both of which have been evaluated individually in AML patients..

Targeting the PI3K/Akt/mTOR Pathway in Malignancy: Rationale and Clinical Outlook

The phosphatidylinositol 3-kinase (PI3K) pathway, including major downstream effectors Akt and mammalian target of rapamycin (mTOR), plays a critical role in malignant transformation and subsequent processes of growth, proliferation, and metastases. Not surprisingly, the PI3K/Akt/mTOR pathway has emerged as an attractive drug target and numerous agents directed against various elements of the pathway are currently in clinical development. While early clinical trials with the first generations of these agents have shown limited single-agent efficacy, efforts are now focused on the development of more specific inhibitors, patient selection strategies, and combinational approaches. In this review, we discuss the PI3K/Akt/mTOR pathway in cancer, the rationale for its emergence as a therapeutic target, and progress thus far in the clinical development of inhibitors targeting its various elements.

Development of Therapeutic Combinations Targeting Major Cancer Signaling Pathways

Signaling networks play key homeostatic processes in living organisms but are commonly hijacked in oncogenesis. Prominent examples include genetically altered receptor tyrosine kinases and dysregulated intracellular signaling molecules. The discovery and development of targeted therapies against such oncogenic proteins has imparted clinical benefit. Nevertheless, concerns remain about the limited single-agent efficacy and narrow therapeutic indices of many of these antitumor agents. Moreover, it is apparent that oncogenic proteins comprise complex signaling networks that interact through crosstalk and feedback loops, which modify therapeutic vulnerability. These complexities mandate the study of drug combinations, which will also become necessary to reverse tumor drug resistance. Here, we outline the challenges associated with rational drug codevelopment strategies, with a focus on the importance of analytically validated biomarkers for patient selection and pharmacokinetic-pharmacodynamic (PK-PD) studies. Overall, the most informative clinical studies of novel combinations will have the following characteristics: robust scientific hypotheses leading to their selection; supportive preclinical data from contextually appropriate preclinical model systems; sufficient preclinical PK data to inform on the risk of drug-drug interactions; and detailed PD studies to determine the biologically active dose range for each agent. Toward this end, several novel clinical trial designs may be envisioned to accelerate successful drug combination development while minimizing the risk of late drug combination attrition. Although considerable challenges remain, these efforts may enable important steps to be taken toward more durable therapeutic control of many cancers.

The Vascular Disrupting Agent STA-9584 Exhibits Potent Antitumor Activity by Selectively Targeting Microvasculature at Both the Center and Periphery of Tumors

Vascular disrupting agents (VDAs) are an emerging class of therapeutics targeting the existing vascular network of solid tumors. However, their clinical progression has been hampered because of limited single-agent efficacy, primarily caused by the persistence of surviving cells at the well perfused "viable rim" of tumors, which allows rapid tumor regrowth to occur. In addition, off-target adverse events, including cardiovascular toxicities, underscore a need for compounds with improved safety profiles. Here, we characterize the mechanism of action, antitumor efficacy, and cardiovascular safety profile of (S)-2-amino-N-(2-methoxy-5-(5-(3,4,5-trimethoxyphenyl)isoxazol-4-yl)phenyl)-3-phenylpropanamide hydrochloride (STA-9584), a novel tubulin-binding VDA. In vitro, 2-methoxy-5-(5-(3,4,5-trimethoxyphenyl)isoxazol-4-yl)aniline (STA-9122) (active metabolite of STA-9584) displayed increased potency relative to other tubulin-binding agents and was highly cytotoxic to tumor cells. STA-9584 induced significant tumor regressions in prostate and breast xenograft models in vivo and, in an aggressive syngeneic model, demonstrated superior tumor growth inhibition and a positive therapeutic index relative to combretastatin A-4 phosphate (CA4P). It is noteworthy that histological analysis revealed that STA-9584 disrupted microvasculature at both the center and periphery of tumors. Compared with CA4P, STA-9584 induced a 73% increase in central necrotic area, 77% decrease in microvasculature, and 7-fold increase in tumor cell apoptosis in the remaining viable rim 24 h post-treatment. Ultrasound imaging confirmed that STA-9584 rapidly and efficiently blocked blood flow in highly perfused tumor regions. Moreover, cardiovascular effects were evaluated in the Langendorff assay and telemetered dogs, and cardiovascular toxicity was not predicted to be dose-limiting. This bioactivity profile distinguishes STA-9584 from the combretastatin class and identifies the compound as a promising new therapeutic VDA candidate.

Treatment of acute myeloid leukemia in older patients

Acute myeloid leukemia carries a dismal prognosis in patients over 60 years of age and, despite many clinical trials of both novel and conventional agents, there has been no significant improvement in overall survival during the last 30 years. Combinations of anthracyclines and cytarabine remain the cornerstone of therapy and produce complete remission in 45–55% of older patients, with a median survival of only 8–12 months. These statistics become even worse in patients over 70 years and those with unfavorable cytogenetics and/or poor performance status. Deciding which older acute myeloid leukemia patients would benefit from intensive chemotherapy is difficult and efforts are underway to improve existing risk-assessment tools. Many new agents are under development, including signal transduction inhibitors, farnesyl transferase inhibitors, antibodies and novel chemotherapeutics. To date, small-molecule inhibitors and targeted therapies have had limited single-agent efficacy and have required combination with chemotherapy. The role of hematopoietic stem cell transplantation in older patients is under investigation. All patients over 60 years of age with acute myeloid leukemia should be encouraged to participate in a clinical trial if possible.