Smac mimetic LCL161 supports neuroblastoma chemotherapy in a drug class-dependent manner and synergistically interacts with ALK inhibitor TAE684 in cells with ALK mutation F1174L

A Phase Ib Dose-Escalation Study of LCL161 Plus Oral Topotecan for Patients With Relapsed/Refractory Small Cell Lung Cancer and Select Gynecologic Malignancies

BACKGROUND

This was an open-label, multicenter, single-arm phase Ib dose-escalation study of oral LCL161 administered in combination with oral topotecan in patients with relapsed/refractory small cell lung cancer (SCLC) and select gynecological cancers.

METHODS

Cohorts of 3-6 patients initiated treatment with LCL161 and topotecan in escalating doses. LCL161 was administered orally on days 1, 8, and 15 of each 21-day cycle; topotecan was administered orally for the first 5 days of each 21-day cycle.

RESULTS

A total of 35 patients were enrolled in 6 cohorts; 30 patients were female; 4 patients had SCLC and 19 patients had ovarian cancer. Median prior lines of therapy were 3 (1-10). Median duration of treatment was 7.1 weeks (0.1-174). The most frequent grade 3/4 treatment-related adverse events were thrombocytopenia (51.43%) and anemia (31.43%). ORR was 9.7%; 58% of patients had SD. The study was stopped early before the maximum tolerated dose (MTD) and recommended phase II dose (RP2D) were determined.

CONCLUSION

The addition of LCL161 to oral topotecan caused more myelosuppression when dosed together than what was associated with either drug alone. Moreover, the drug combination did not improve outcomes. The study was terminated early (ClinicalTrials.gov Identifier: NCT02649673).

Targeting the apoptosis pathway to treat tumours of the paediatric nervous system

New, more effective therapeutics are required for the treatment of paediatric cancers. Current treatment protocols of cytotoxic treatments including chemotherapy trigger cancer-cell death by engaging the apoptosis pathway, and chemotherapy efficacy is frequently impeded by apoptosis dysregulation. Apoptosis dysregulation, through genetic or epigenetic mechanisms, is a feature of many cancer types, and contributes to reduced treatment response, disease progression and ultimately treatment resistance. Novel approaches are required to overcome dysregulated apoptosis signalling, increase the efficacy of cancer treatment and improve patient outcomes. Here, we provide an insight into current knowledge of how the apoptosis pathway is dysregulated in paediatric nervous system tumours, with a focus on TRAIL receptors, the BCL-2 proteins and the IAP family, and highlight preclinical evidence demonstrating that pharmacological manipulation of the apoptosis pathway can restore apoptosis signalling and sensitise cancer cells to treatment. Finally, we discuss the potential clinical implications of these findings.

Synthetic Heterocyclic Derivatives as Kinase Inhibitors Tested for the Treatment of Neuroblastoma

In the last few years, small molecules endowed with different heterocyclic scaffolds have been developed as kinase inhibitors. Some of them are being tested at preclinical or clinical levels for the potential treatment of neuroblastoma (NB). This disease is the most common extracranial solid tumor in childhood and is responsible for 10% to 15% of pediatric cancer deaths. Despite the availability of some treatments, including the use of very toxic cytotoxic chemotherapeutic agents, high-risk (HR)-NB patients still have a poor prognosis and a survival rate below 50%. For these reasons, new pharmacological options are urgently needed. This review focuses on synthetic heterocyclic compounds published in the last five years, which showed at least some activity on this severe disease and act as kinase inhibitors. The specific mechanism of action, selectivity, and biological activity of these drug candidates are described, when established. Moreover, the most remarkable clinical trials are reported. Importantly, kinase inhibitors approved for other diseases have shown to be active and endowed with lower toxicity compared to conventional cytotoxic agents. The data collected in this article can be particularly useful for the researchers working in this area.

An Updated Review of Smac Mimetics, LCL161, Birinapant, and GDC-0152 in Cancer Treatment

Inhibitor of apoptosis proteins (IAPs) are suggested as therapeutic targets for cancer treatment. Smac/DIABLO is a natural IAP antagonist in cells; therefore, Smac mimetics have been developed for cancer treatment in the past decade. In this article, we review the anti-cancer potency and novel molecular targets of LCL161, birinapant, and GDC-0152. Preclinical studies demonstrated that Smac mimetics not only induce apoptosis but also arrest cell cycle, induce necroptosis, and induce immune storm in vitro and in vivo. The safety and tolerance of Smac mimetics are evaluated in phase 1 and phase 2 clinical trials. In addition, the combination of Smac mimetics and chemotherapeutic compounds was reported to improve anti-cancer effects. Interestingly, the novel anti-cancer molecular mechanism of action of Smac mimetics was reported in recent studies, suggesting that many unknown functions of Smac mimetics still need to be revealed. Exploring these currently unknown signaling pathways is important to provide hints for the modification and combination therapy of further compounds.

Combination therapy using Smac peptide and doxorubicin-encapsulated MUC 1-targeted polymeric nanoparticles to sensitize cancer cells to chemotherapy: An in vitro and in vivo study

Targeting inhibitors of apoptosis proteins (IAPs) family comprising high level expression in many cancer cells, could sensitize tumor cells to conventional chemotherapies. In the present study, we designed both doxorubicin and SmacN6 (an antagonist of the IAPs) encapsulated polymeric nanoparticles (NPs) and investigated their synergistic effect of combination therapy in vitro and in vivo. According to the results, NPs-SmacN6 significantly enhanced the cytotoxicity effect of NPs-DOX and reduced its IC₅₀ in MCF-7, 4T1 and C26 cancer cells. Western blot analysis confirmed mechanism of cell apoptosis via caspase activation through intrinsic and also extrinsic pathways. Moreover, 5TR1 aptamer-modified NPs could effectively deliver DOXor SmacN6 to C26 cancer cells (MUC1 positive) in comparison with the non-targeted one (p < 0.001). However, they could not be efficiently internalized into CHO cells (MUC1 negative), showing less cytotoxicity in this cell line. In vivo experiments in BALB/c mice bearing C26 tumor indicated that Apt-NPs-DOX in combination with Apt-NPs-SmacN6 had significant tumor growth inhibition in comparison with mice receiving either free DOX or Apt-NPs-DOX with p < 0.0001 and p < 0.05, respectively. Our results revealed that combination therapy of DOX and SmacN6 via Apt-modified nanoparticles can lead to improvement of therapeutic index of DOX in MUC1 positive cancer cells.

Molecular and Functional Characterization of Inhibitor of Apoptosis Proteins (IAP, BIRP) in Echinococcus granulosus

The larval stage of Echinococcus granulosus sensu lato, resulting in cystic echinococcosis, a parasitic zoonosis, causes huge economic losses to the livestock industry and poses a threat to public health. Inhibitor of apoptosis proteins (IAPs) is a class of endogenous anti-apoptotic family, which plays a significant functional role in the regulation of organism’s development. Herein, to explore potential functions of IAPs in E. granulosus, two members of IAPs from E. granulosus (Eg-IAP and Eg-BIRP) were cloned, expressed, and molecularly characterized. Eg-IAP and Eg-BIRP encoded putative 331 and 168 residue proteins, respectively. Bioinformatic analysis showed that both proteins contained a type II BIR domain-the essential functional domain of IAPs. Fluorescence immunohistochemistry revealed that both proteins were ubiquitously localized in all life-cycle stages of E. granulosus. Our fluorescent quantitative PCR (RT-qPCR) results revealed relatively higher transcription levels of two Eg-IAPs in protoscoleces (PSCs) compared to the 18-day strobilated worms. We further used different concentrations of LCL161, a Smac-mimetic pan-IAPs inhibitor, to induce the apoptosis in PSCs in vitro, and revealed that the survival rate of PSCs and transcription levels of both genes were negatively correlated with the concentration of LCL161. While the results of light microscopy, transmission electron microscopy (TEM), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay also showed a higher apoptotic rate in PSCs with the increasing concentrations of LCL161. Taken together, our findings provide the reasonable evidence that both Eg-IAP and Eg-BIRP have potential implication in critical anti-apoptotic roles during the development of E. granulosus.

The SMAC mimetic LCL-161 displays antitumor activity in preclinical models of rituximab-resistant B-cell lymphoma

Clinical observations suggest the existence of shared resistance pathways between rituximab and chemotherapy agents. To explore the mechanisms of rituximab resistance, our group created rituximab-resistant cell lines (RRCLs), which display altered expression of several inhibitor of apoptosis (IAP) family proteins. Here, we provide evidence to support pharmacologically targeting IAPs in lymphoma with LCL-161, a small molecule mimetic of the second mitochondria-derived activator of caspases (SMAC). The antitumor effect of LCL-161 was determined using luminescent adenosine triphosphate assays, flow cytometry, SCID mouse xenografts, and ex vivo patient biopsy sample studies. In vitro exposure to LCL-161 also resulted in a dose-dependent decrease in IAP levels, along with synergistic enhancement of the antitumor effect of cytotoxic chemotherapy, in rituximab-sensitive cell lines and RRCLs. In addition, LCL-161 increased the cytotoxic effect of the proteasome inhibitor carfilzomib in ex vivo lymphoma patient samples. The combination of LCL-161 with the chemotherapy regimen rituximab, gemcitabine, and vinorelbine (RGV) improved in vivo survival compared with RGV alone in severe combined immunodeficient mice implanted with RRCLs but not in animals implanted with rituximab-sensitive cell lines. In summary, LCL-161 exhibits synergistic antitumor activity in both in vitro and in vivo models of resistant lymphoma. Our data support further preclinical investigation of LCL-161 as a novel antilymphoma agent.

In Search of Panacea-Review of Recent Studies Concerning Nature-Derived Anticancer Agents

Cancers are one of the leading causes of deaths affecting millions of people around the world, therefore they are currently a major public health problem. The treatment of cancer is based on surgical resection, radiotherapy, chemotherapy or immunotherapy, much of which is often insufficient and cause serious, burdensome and undesirable side effects. For many years, assorted secondary metabolites derived from plants have been used as antitumor agents. Recently, researchers have discovered a large number of new natural substances which can effectively interfere with cancer cells’ metabolism. The most famous groups of these compounds are topoisomerase and mitotic inhibitors. The aim of the latest research is to characterize natural compounds found in many common foods, especially by means of their abilities to regulate cell cycle, growth and differentiation, as well as epigenetic modulation. In this paper, we focus on a review of recent discoveries regarding nature-derived anticancer agents.

Vincristine resistance in relapsed neuroblastoma can be efficiently overcome by Smac mimetic LCL161 treatment

PURPOSE

In spite of good initial therapy response neuroblastomas often spread to distant organs or relapse after periods of remission. Dysregulation of apoptosis, a hallmark of cancer, is often effected by elevated levels of antiapoptotic signals leading to resistance against chemotherapeutic drugs. Inhibitors of apoptosis proteins (IAPs) are crucial cellular apoptosis regulators. Targeting IAPs with Smac mimetics has been demonstrated as a promising strategy for treatment of neuroblastoma and other tumors.

METHODS

In paired neuroblastoma cell lines, obtained from the same patient at time of diagnosis (CHLA-15) and postchemotherapy during progressive disease (CHLA-20), expression of crucial IAPs was determined. Furthermore, effects of vincristine on viability, cytotoxicity, apoptosis induction and caspase-3/7 activation were determined.

RESULTS

Cellular IAP-1 (cIAP-1) and X-linked IAP (XIAP) expression was increased in cell line CHLA-20. Moreover, biological effects of vincristine were significantly lower in these cells. Treatment of cells with Smac mimetic LCL161 increased the effects of vincristine in CHLA-15 cells and more importantly was able to overcome vincristine resistance in CHLA-20 cells.

CONCLUSIONS

These findings demonstrate the potential of Smac mimetics for the development of novel therapeutic approaches for the treatment of relapsed/resistant neuroblastoma.

Inhibitors of apoptosis: clinical implications in cancer

Inhibitor of apoptosis (IAP) family comprises a group of endogenous proteins that function as main regulators of caspase activity and cell death. They are considered the main culprits in evasion of apoptosis, which is a fundamental hallmark of carcinogenesis. Overexpression of IAP proteins has been documented in various solid and hematological malignancies, rendering them resistant to standard chemotherapeutics and radiation therapy and conferring poor prognosis. This observation has urged their exploitation as therapeutic targets in cancer with promising pre-clinical outcomes. This review describes the structural and functional features of IAP proteins to elucidate the mechanism of their anti-apoptotic activity. We also provide an update on patterns of IAP expression in different tumors, their impact on treatment response and prognosis, as well as the emerging investigational drugs targeting them. This aims at shedding the light on the advances in IAP targeting achieved to date, and encourage further development of clinically applicable therapeutic approaches.

Molecular mechanisms and therapeutic targets in neuroblastoma

Neuroblastoma is the most common extracranical tumor of childhood and the most deadly tumor of infancy. It is characterized by early age onset and high frequencies of metastatic disease but also the capacity to spontaneously regress. Despite intensive therapy, the survival for patients with high-risk neuroblastoma and those with recurrent or relapsed disease is low. Hence, there is an urgent need to develop new therapies for these patient groups. The molecular pathogenesis based on high-throughput omics technologies of neuroblastoma is beginning to be resolved which have given the opportunity to develop personalized therapies for high-risk patients. Here we discuss the potential of developing targeted therapies against aberrantly expressed molecules detected in sub-populations of neuroblastoma patients and how these selected targets can be drugged in order to overcome treatment resistance, improve survival and quality of life for these patients and also the possibilities to transfer preclinical research into clinical testing.

Sensitization of neuroblastoma for vincristine-induced apoptosis by Smac mimetic LCL161 is attended by G2 cell cycle arrest but is independent of NFκB, RIP1 and TNF-α

We demonstrated sensitization for chemotherapy by Smac mimetic (SM) LCL161, a potent antagonist of inhibitor of apoptosis proteins (IAP), in neuroblastoma (NB). Vinca alkaloids, particularly vincristine (VCR), displayed the strongest impact on inhibition of proliferation and apoptosis induction in combination with LCL161. The underlying signaling pathways remain elusive, though. LCL161 induces a quick degradation of cellular IAP 1 (cIAP-1). Combination of LCL161 with VCR had only marginal effects on X-linked IAP (XIAP) protein expression. Cell death is accompanied by activation of intrinsic (caspase-9 and MMP) and extrinsic (caspase-8) pathways of apoptosis, repression of migratory potential and cell cycle arrest in G2 phase.

LCL161-induced cIAP degradation leads to activation of non-canonical and blockade of canonical NF-κB pathways but not induction of apoptosis. Surprisingly NF-κB and TNF-α signaling is negligible for VCR- and VCR/LCL161-induced apoptosis since chemical inhibition of NF-κB using BAY-7085 and PBS-1086, as well as application of TNF-α blocking antibody Humira (adalimumab) has no relevant effect on cell death. Recently formation of a TNF-α-independent complex (ripoptosome) consisting of RIP1, FADD and caspase-8 following IAP inhibition by SM has been described. However, targeting of RIP1 by Necrostatin was not sufficient to influence apoptosis induced by VCR/LCL161.

IAP antagonists induce anti-tumor immunity in multiple myeloma

The cellular inhibitors of apoptosis (cIAP) 1 and 2 are amplified in about 3% of cancers and have been identified in multiple malignancies as being potential therapeutic targets as a result of their role in the evasion of apoptosis. Consequently, small-molecule IAP antagonists, such as LCL161, have entered clinical trials for their ability to induce tumor necrosis factor (TNF)-mediated apoptosis of cancer cells. However, cIAP1 and cIAP2 are recurrently homozygously deleted in multiple myeloma (MM), resulting in constitutive activation of the noncanonical nuclear factor (NF)-κB pathway. To our surprise, we observed robust in vivo anti-myeloma activity of LCL161 in a transgenic myeloma mouse model and in patients with relapsed-refractory MM, where the addition of cyclophosphamide resulted in a median progression-free-survival of 10 months. This effect was not a result of direct induction of tumor cell death, but rather of upregulation of tumor-cell-autonomous type I interferon (IFN) signaling and a strong inflammatory response that resulted in the activation of macrophages and dendritic cells, leading to phagocytosis of tumor cells. Treatment of a MM mouse model with LCL161 established long-term anti-tumor protection and induced regression in a fraction of the mice. Notably, combination of LCL161 with the immune-checkpoint inhibitor anti-PD1 was curative in all of the treated mice.