Late Clinical Trials Research Articles

Biophysical Analysis of the Putative Heart Failure Drug Omecamtiv Mecarbil

The small molecule omecamtiv mecarbil (OM), currently in late phase-2 clinical trials for treatment of heart failure, activates force generation by cardiac myosin. How OM increases force generation is not known. Crosslinking and molecular docking studies suggest that the compound binds to the relay/SH1/converter region of myosin, hypothesized to control the actin-activated pre to post power-stroke structural transition in the myosin catalytic and light-chain domains. These transitions drive force production by myosin. We are currently using time-resolved FRET and EPR distance measurements to detect the pre- and post-power-stroke structural states of myosin. We have performed these studies on tissue-purified β-cardiac and α-skeletal myosin, and on a recombinant cys-lite myosin II catalytic domain model from Dictyostelium discoideum. In each of the myosin isoforms, we find that OM binding increases the mole fraction of the myosin post power-stroke structural state in the presence of ATP analogs. Transient time-resolved FRET experiments, mixing FRET-labeled myosin with ATP, show that drug binding also alters the structural kinetics of the myosin recovery-stroke. Ongoing studies are investigating the affect of OM on the actin-activated power-stroke. These results show that OM has a direct effect on the power-stroke structural transition that drives force generation in muscle, thus providing structural insight into the mechanism of this new potential therapy for heart failure. Our results also highlight the utility of structure-based time-resolved FRET and EPR assays for the discovery and characterization of allosteric enzyme modulators.

Structural Characterization of a Therapeutic Anti-Methamphetamine Antibody Fragment: Oligomerization and Binding of Active Metabolites

Vaccines and monoclonal antibodies (mAb) for treatment of (+)-methamphetamine (METH) abuse are in late stage preclinical and early clinical trial phases, respectively. These immunotherapies work as pharmacokinetic antagonists, sequestering METH and its metabolites away from sites of action in the brain and reduce the rewarding and toxic effects of the drug. A key aspect of these immunotherapy strategies is the understanding of the subtle molecular interactions important for generating antibodies with high affinity and specificity for METH. We previously determined crystal structures of a high affinity anti-METH therapeutic single chain antibody fragment (scFv6H4, KD = 10 nM) in complex with METH and the (+) stereoisomer of 3,4-methylenedioxymethamphetamine (MDMA, or “ecstasy”). Here we report the crystal structure of scFv6H4 in homo-trimeric unbound (apo) form (2.60Å), as well as monomeric forms in complex with two active metabolites; (+)-amphetamine (AMP, 2.38Å) and (+)-4-hydroxy methamphetamine (p-OH-METH, 2.33Å). The apo structure forms a trimer in the crystal lattice and it results in the formation of an intermolecular composite beta-sheet with a three-fold symmetry. We were also able to structurally characterize the coordination of the His-tags with Ni2+. Two of the histidine residues of each C-terminal His-tag interact with Ni2+ in an octahedral geometry. In the apo state the CDR loops of scFv6H4 form an open conformation of the binding pocket. Upon ligand binding, the CDR loops adopt a closed formation, encasing the drug almost completely. The structural information reported here elucidates key molecular interactions important in anti-methamphetamine abuse immunotherapy.

Inhibition Of LSD1 As a Therapeutic Strategy For The Treatment Of Acute Myeloid Leukemia

Lysine specific demethylase 1 (LSD1) is a histone H3K4me1/2 demethylase found in various transcriptional co-repressor complexes. These complexes include Histone Deacetylases (HDAC1/2) and Co-Repressor for Element-1-Silencing Transcription factor (CoREST). LSD1 mediated H3K4 demethylation can result in a repressive chromatin environment that silences gene expression. LSD1 has been shown to play a role in development in various contexts. LSD1 can interact with pluripotency factors in human embryonic stem cells and is important for decommissioning enhancers in stem cell differentiation. Beyond embryonic settings, LSD1 is also critical for hematopoietic differentiation. LSD1 is overexpressed in multiple cancer types and recent studies suggest inhibition of LSD1 reactivates the all-trans retinoic acid receptor pathway in acute myeloid leukemia (AML). These studies implicate LSD1 as a key regulator of the epigenome that modulates gene expression through post-translational modification of histones and through its presence in transcriptional complexes.The current study describes the anti-tumor effects of a novel LSD1 inhibitor (GSK2879552) in AML. GSK2879552 is a potent, selective, mechanism-based, irreversible inhibitor of LSD1. Screening of over 150 cancer cell lines revealed that AML cells have a unique requirement for LSD1. While LSD1 inhibition did not affect the global levels of H3K4me1 or H3K4me2, local changes in these histone marks were observed near transcriptional start sites of putative LSD1 target genes. This increase in the transcriptionally activating histone modification correlated with a dose dependent increase in gene expression. Treatment with GSK2879552 promoted the expression of cell surface markers, including CD11b and CD86, associated with a differentiated immunophenotype in 12 of 13 AML cell lines. For example, in SKM-1 cells, increases in cell surface expression of CD86 and CD11b occurred after as early as one day of treatment with EC50 values of 13 and 7 nM respectively. In a separate study using an MV-4-11 engraftment model, increases in CD86 and CD11b were observed as early as 8 hours post dosing.GSK2879552 treatment resulted in a potent anti-proliferative growth effect in 19 of 25 AML cell lines (average EC50 = 38 nM), representing a range of AML subtypes. Potent growth inhibition was also observed on AML blast colony forming ability in 4 out of 5 bone marrow samples derived from primary AML patient samples (average EC50 = 205 nM). The effects of LSD1 inhibition were further characterized in an in vivo mouse model of AML induced by transduction of mouse hematopoietic progenitor cells with a retrovirus encoding MLL-AF9 and GFP. Primary AML cells were transplanted into a cohort of secondary recipient mice and upon engraftment, the mice were treated for 17 days. After 17 days of treatment, control treated mice had 80% GFP+ cells in the bone marrow whereas treated mice possessed 2.8% GFP positive cells (p<0.012). The percentage of GFP+ cells continued to decrease to 1.8% by 1-week post therapy. Remarkably, in a preliminary assessment for survival, control-treated mice succumbed to AML by 28 days post transplant, while treated mice showed prolonged survival.Together, these data demonstrate that pharmacological inhibition of LSD1 may provide a promising treatment for AML by promoting differentiation and subsequent growth inhibition of AML blasts. GSK2879552 is currently in late preclinical development and clinical trials are anticipated to start in 2014.All studies were conducted in accordance with the GSK Policy on the Care, Welfare and Treatment of Laboratory Animals and were reviewed the Institutional Animal Care and Use Committee either at GSK or by the ethical review process at the institution where the work was performed. Disclosures:Kruger:GlaxoSmithKline Pharmaceuticals: Employment. Mohammad:GlaxoSmithKline Pharmaceuticals: Employment. Smitheman:GlaxoSmithKline Pharmaceuticals: Employment. Liu:GlaxoSmithKline Pharmaceuticals: Employment. Pappalardi:GlaxoSmithKline Pharmaceuticals: Employment. Federowicz:GlaxoSmithKline Pharmaceuticals: Employment. Van Aller:GlaxoSmithKline Pharmaceuticals: Employment. Kasparec:GlaxoSmithKline Pharmaceuticals: Employment. Tian:GlaxoSmithKline Pharmaceuticals: Employment. Suarez:GlaxoSmithKline Pharmaceuticals: Employment. Rouse:GlaxoSmithKline Pharmaceuticals: Employment. Schneck:GlaxoSmithKline Pharmaceuticals: Employment. Carson:GlaxoSmithKline Pharmaceuticals: Employment. McDevitt:GlaxoSmithKline Pharmaceuticals: Employment. Ho:GlaxoSmithKline Pharmaceuticals: Employment. McHugh:GlaxoSmithKline Pharmaceuticals: Employment. Miller:GlaxoSmithKline Pharmaceuticals: Employment. Johnson:GlaxoSmithKline Pharmaceuticals: Employment. Armstrong:Epizyme Inc.: Has consulted for Epizyme Inc. Other. Tummino:GlaxoSmithKline Pharmaceuticals: Employment.

Ovarian cancer clinical trial endpoints: Society of Gynecologic Oncology white paper

ObjectiveTo explore the value of multiple clinical endpoints in the unique setting of ovarian cancer. MethodsA clinical trial workgroup was established by the Society of Gynecologic Oncology to develop a consensus statement via multiple conference calls, meetings and white paper drafts. ResultsClinical trial endpoints have profound effects on late phase clinical trial design, result interpretation, drug development, and regulatory approval of therapeutics. Selection of the optimal clinical trial endpoint is particularly provocative in ovarian cancer where long overall survival (OS) is observed. The lack of new regulatory approvals and the lack of harmony between regulatory bodies globally for ovarian cancer therapeutics are of concern. The advantages and disadvantages of the numerous endpoints available are herein discussed within the unique context of ovarian cancer where both crossover and post-progression therapies potentially uncouple surrogacy between progression-free survival (PFS) and OS, the two most widely supported and utilized endpoints. The roles of patient reported outcomes (PRO) and health related quality of life (HRQoL) are discussed, but even these widely supported parameters are affected by the unique characteristics of ovarian cancer where a significant percentage of patients may be asymptomatic. Original data regarding the endpoint preferences of ovarian cancer advocates is presented. ConclusionsEndpoint selection in ovarian cancer clinical trials should reflect the impact on disease burden and unique characteristics of the treatment cohort while reflecting true patient benefit. Both OS and PFS have led to regulatory approvals and are clinically important. OS remains the most objective and accepted endpoint because it is least vulnerable to bias; however, the feasibility of OS in ovarian cancer is compromised by the requirement for large trial size, prolonged time-line for final analysis, and potential for unintended loss of treatment effect from active post-progression therapies. A large magnitude of effect in PFS improvement should establish benefit, and further communication with regulatory authorities to clarify acceptable endpoints should be undertaken.

Current status and perspectives on stem cell-based therapies undergoing clinical trials for regenerative medicine: case studies

Apart from haematopoietic stem cell transplantation for haematological disorders many stem cell-based therapies are experimental. However, with only 12 years between human embryonic stem cell isolation and the first clinical trial, development of stem cell products for regenerative medicine has been rapid and numerous clinical trials have begun to investigate their therapeutic potential. This review summarizes key clinical trial data, current and future perspectives on stem cell-based products undergoing clinical trials, based on literature search and author research. It is widely recognized that the ability to stimulate stem cell differentiation into specialized cells for use as cellular therapies will revolutionize health care and offer major hope for numerous diseases for which there are limited or no therapeutic options. Stem cell-based products are unique and cover a large range of disorders to be treated; therefore, there is significant potential for variation in cell source, type, processing manipulation, the bioprocessing approach and scalability, the cost and purity of manufacture, final product quality and mode of action. As such there are gaps in regulatory and manufacturing frameworks and technologies, only a small number of products are currently within late phase clinical trials and few products have achieved commercialization. Recent developments are encouraging acceleration through the difficulties encountered en route to clinical trials and commercialization of stem cell therapies. The field is growing year on year with the first clinical trial using induced pluripotent stem cells anticipated by end 2013.

The consensus studysquamous cell carcinoma of the oropharynx: late phase clinical trials; core outcomes

Background Contemporary treatments for Oropharyngeal cancer (OPSCC) are associated with a number of debilitating side-effects. Whilst these have a significant impact on the patient’s quality of life, they are often not measured in clinical trials of new treatments. In fact, patients and those involved in their care are rarely involved in such outcome selection. As a result, the outcomes chosen are often not relevant to patients or may have little clinical application, and important outcomes may not be measured at all. Furthermore, there is no standardisation of outcome selection and reporting, even amongst trials of comparable interventions. This reduces the data available for meta-analyses leading to difficulties in interpreting a treatment’s effectiveness and in making evidence based healthcare decisions. Outcome reporting bias has also been highlighted as a significant problem in the healthcare literature. Objectives

Synthesis, crystallographic characterization and electrochemical property of a copper(II) complex of the anticancer agent elesclomol

Elesclomol is a novel anticancer agent that has been evaluated in a number of late stage clinical trials. A new and convenient synthesis of elesclomol and its copper complex is described. X-ray crystallographic characterization and the electrochemical properties of the elesclomol copper(II) complex are discussed. The copper(II) cation is coordinated in a highly distorted square-planar geometry to each of the sulphur and amide nitrogen atoms of elesclomol. Electrochemical measurements demonstrate that the complex undergoes a reversible one-electron reduction at biologically accessible potentials. In contrast the free elesclomol is found electrochemically inactive. This evidence is in strong support of the mechanism of action we proposed for the anticancer activity of elesclomol.

Abstract IA19: Exploiting DNA repair deficiencies in breast cancer using PARP inhibitors

Abstract Epithelial cancers arise through acquisition of mutation in multiple genes causing either gain or loss of functions that give a phenotypic advantage to the affected cell and acquisition of key features of malignancy commonly described as the “hallmarks of cancer”. This acquisition of sufficient mutational burden to acquire these “hallmarks” may be accelerated by deficiency in one or more of number of partially redundant DNA repair mechanisms that have evolved to maintain genome stability. Many forms of chemotherapy and radiation therapy have long exploited tumor's relative deficiencies in the DNA damage response and in DNA repair specifically. Recently more specific inhibitors of DNA repair and DNA damage response effectors have been developed and tested in preclinical models and early phase clinical trials. These have shown proof of concept for the principle of tumor specific “synthetic lethality” where the synergistic combination of a therapeutically induced deficiency in one form of genome stability mechanism with a tumor specific constitutive defect in a mutually dependant from DNA repair leads to high specific tumor cell killing. This principle has been found to apply to the combination of small molecule induced inhibition of PARP1 and PARP2 in combination with tumor cell intrinsic defects in the homologous recombination (HR) DNA repair mechanism. A number of genes involved in HR, including BRCA1, BRCA2, ATM and PALB2 lead to elevated risk of breast cancer when mutated in the germline. The tumors that develop in these contexts have, as a result, functional defects in HR. Recent evidence has also suggested that a significant proportion of breast cancers show distinctive patterns of genome instability and changes in DNA damage induced repair protein expression phenotypes that indicate loss of function of HR DNA repair. Recent correlative biology studies in breast cancer and ovarian cancer trials show correlation between these emerging biomarkers with efficacy of platinum based chemotherapy, also known to target deficiency in HR. The further investigation of PARP inhibitors in breast cancer has been slowed by an initial focus of interest in the larger sporadic breast cancer population and the difficulties in identifying a likely maximum effect population in this wider population without robust assays for defects in the DNA damage response. Progress has also been hampered by the difficulty of finding tolerable combinations of these agents with chemotherapy. Differences have been uncovered between PARP inhibitor agents both in terms of potency and mechanisms of action related to presence or absence of trapping of PARP in complex with DNA that may differentially effect efficacy in targeting HR DNA repair defects or potentiation of DNA damaging chemotherapeutics. The small molecule Iniparib has been found to have no significant PARP inhibitory effect and in consequence the results with this agent in breast cancer should not be regarded as having tested any role for PARP inhibition in this context. Focus in late phase clinical trials of PARP inhibitors in breast cancer is currently returning to potent PARP inhibitors and the original proof of concept germline mutation carrier population. Here crucial questions may still remain around prevalence of mechanisms of acquired resistance demonstrated to occur in preclinical models through somatic reversion of mutations in BRCA1 and BRCA2, selection for loss of function of genes such as 53BP1 that stimulate alternative use of Non-homologous end-joining (NHEJ) repair and overexpression of the P-glycoprotein drug efflux transporter. In this lecture I will review the preclinical and emerging biomarker data described above and their relevance to current and imminent clinical trials exploring PARP inhibition in breast cancer. Citation Format: Andrew Tutt. Exploiting DNA repair deficiencies in breast cancer using PARP inhibitors. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr IA19.

Drug repositioning framework by incorporating functional information

As a shortcut for drug development, drug repositioning draws more and more attention in pharmaceutical industry to identify new indications for marketed drugs or drugs failed in late clinical trial phase. At the same time, the abundant high-throughput data pushes the computationally repositioning drugs a hot topic in the area of systems biology. Here, the authors propose a general framework for repositioning drug by incorporating various functional information. The framework starts with the identification of differentially expressed gene sets under disease state and drug treatment. Then the disease and drug are associated by the overlap of these two gene sets via biological function. The authors provide two strategies to assess the functional overlap. In the first strategy, functional relevance are evaluated by leveraging genes' lethality information to reveal drug's potential of curing diseases. In the second strategy, biological process perturbation profiles are identified by mapping differentially expressed genes into pathways and gene ontology (GO) terms. Their associations are assessed and used to rank drugs' potential of curing diseases. The preliminary results on prostate cancer demonstrate that our new framework improves the drug repositioning efficiency and various function information could complement each other. Importantly, the new framework will enhance the biological interpretation and rationale of drug repositioning and provide insights into drug action mechanisms.

T.I.2 Exon skipping and PRO044 in Duchenne muscular dystrophy: Extending the program

Patients with Duchenne muscular dystrophy (DMD) suffer from progressive muscle degeneration due to DMD gene mutations and resulting absence of dystrophin. Antisense oligonucleotides (AONs) have potential to modulate premRNA splicing so that a specific exon is skipped and the disrupted dystrophin reading frame restored. This allows production of internally deleted, partially functional dystrophins like those produced in Becker muscular dystrophy, which may lead to improvements in DMD skeletal muscle function through improved membrane stability and cell signaling. The first AON, currently in late phase clinical trials, is drisapersen (PRO051; GSK), a 2′-O-methyl phosphorothioate (2OMePS) RNA molecule inducing specific exon 51 skipping. Recently, a second AON was developed to target a different DMD patient population. PRO044, also a 2OMePS RNA molecule, applies to 6% of the DMD population and induces specific exon 44 skipping in dystrophin premRNA and dystrophin expression in cultured muscle cells of DMD patients. A Phase 1/2 open-label study of systemic PRO044 in 18 boys with DMD (5–15 years) is close to completion, exploring safety pharmacokinetics and molecular efficacy at different dose levels with five once-weekly sc administrations (0.5, 1.5, 5, 8, 12 mg/kg). Nine of these boys have also received 5 additional weekly doses at different dose levels by iv infusion (1.5, 5, 12 mg/kg). Preliminary data are encouraging. No clinical response was expected after 5 weeks’ treatment; however, the safety profile is consistent with the class of compound and a molecular response has been observed. Due to high degrees of spontaneous skipping, giving rise to revertant fibers in this DMD population, a new and robust, reproducible dystrophin detection methodology has been developed. Data will be presented to show effects on safety and plasma/tissue drug levels, putative biomarkers and muscle dystrophin expression, which will be used to support subsequent long-term PRO044 studies.

194th ENMC international workshop. 3rd ENMC workshop on exon skipping: Towards clinical application of antisense-mediated exon skipping for Duchenne muscular dystrophy 8–10 December 2012, Naarden, The Netherlands

194th ENMC international workshop. 3rd ENMC workshop on exon skipping: Towards clinical application of antisense-mediated exon skipping for Duchenne muscular dystrophy 8–10 December 2012, Naarden, The Netherlands

Crosstalk between HER2 signaling and angiogenesis in breast cancer

Angiogenesis is an essential hallmark of cancer. Targeting angiogenesis has proven its efficacy in the modern therapeutic paradigm. HER2 positive breast cancer, in particular, is a challenging disease in which resistance to standard therapy has been attributed to parallel and downstream signaling cascades including angiogenesis. This review explores the molecular mechanisms underlying crosstalk between HER2 signaling and angiogenesis. It highlights the role of angiogenesis in the emerging resistance to anti-HER2 therapy. It surveys the current repertoire of clinical trials involving use of combination of anti-HER2 and antiangiogenic therapies. Finally, it entertains the hopes and challenges posed by this novel therapeutic approach. HER2 signaling upregulates angiogenesis at different levels and by different mechanisms. A large number of clinical trials were conducted in attempt to exploit the potential benefit of the combination. Results of early phase trials were promising. However, in the late phase clinical trials, the AVEREL trial did not demonstrate a consistent benefit for bevacizumab in the HER2 positive breast cancer patient population. The BETH trial is ongoing and recruiting patients. Safety issues regarding cardiovascular toxicity of the combination have been already raised. Negative experience of dual EGFR and VEGF targeting in colon cancer cannot be overlooked. Angiogenesis and HER2 signaling are closely related at the molecular level. Appraisal of efficacy of antiangiogenic therapies requires revisit of the current literature as well as following the results of ongoing trials.

ICH E14 Q & A (R1) document: perspectives on the updated recommendations on thorough QT studies.

The International Conference on Harmonization (ICH) guidance ICH E14 provides recommendations, focusing on a clinical 'thorough QT/QTc (TQT) study', to evaluate the QT liability of a drug during its development. An Implementation Working Group (IWG) was also established to assist the sponsors with any uncertainties and clarify any ambiguities. In April 2012, the IWG updated its June 2008 version of the Questions and Answers document to address additional issues. These include the gender of the study population, a reasonable approach to evaluating QTc changes in late stage clinical development and the recommended approach to correcting the measured QT interval. This commentary provides our observations and, when appropriate, recommendations, on these issues. We review briefly evidence that suggests that (i) the greater QT effect observed in females is not entirely related to differences in drug exposure and (ii) the Fridericia correction of measured QT interval is adequate for a majority of TQT studies. Until further evidence suggests otherwise, we recommend balanced gender representation in TQT studies, unless warranted otherwise, and for positive studies, subgroup analysis of key data by common demographic variables including the gender and ethnicity. We provide a general scheme for ECG monitoring in late phase clinical trials and consider that while intensive monitoring and centralized reading of ECGs in late phase clinical trials is the norm when a TQT study is positive, there are other circumstances that also call for high quality ECG reading. Therefore, locally read ECGs should only be acceptable as long as accurate high quality ECG data can be guaranteed.

Integration of stochastic simulation with multivariate analysis: Short-term facility fit prediction

This article describes a decision-support tool to help pinpoint the potential root causes of sub-optimal short-term facility fit issues in biopharmaceutical facilities. This was achieved by creating a tool that integrated stochastic simulation with advanced multivariate statistical analysis. Process fluctuations in product titers in cell culture, step yields, and chromatography eluate volumes were mimicked using Monte Carlo simulation data derived using a stochastic discrete-event simulation model. The resulting stochastic datasets, with the computed consequences on key metrics such as product mass loss and cost of goods, were examined using advanced multivariate statistical techniques. Principal component analysis combined with clustering algorithms was used to analyze the complex datasets from complete industrial batch processes for biopharmaceuticals. The challenge of visualizing the multidimensional nature of the dataset was addressed using hierarchical and k-means clustering as well as stacked parallel co-ordinate plots to help identify process fingerprints and characteristics of clusters leading to sub-optimal facility fit issues. Industrially-relevant case studies are presented that focus on technology transfer challenges for therapeutic antibodies moving from early phase to late phase clinical trials. The case study details how sub-optimal facility fit can be alleviated by allocating alternative product pool tanks. The impact of this operational change is then assessed by reviewing an updated process fingerprint.

A case of metastatic urachal adenocarcinoma treated with several

Urachal cancer is a rare form of bladder cancer that arises fromthe urachus, a vestigial musculofibrous band that extends from thedome of the bladder to the umbilicus. Urachal cancer often presentsat an advanced stage and has a dismal prognosis. We presenta case of a young woman with urachal cancer that recurred rapidlypost-partial cystectomy. The patient was treated with up to 6 different chemotherapy regimens, including an oral antiangiogenic drug as part of a clinical trial. Our case illustrates the aggressive nature of this disease, the difficulty in accessing drugs for the treatment of rare cancers and the lack of late stage clinical trials to help guide therapeutic decisions.

Industry Update: the Latest Developments in Therapeutic Delivery

The present industry update covers the period 16 October–15 November 2012, with information sourced from mainly company press releases, regulatory and patent agencies. This month saw Novo Nordsk’s long-acting insulin product (degludec) gain approval from the US FDA. There were mixed fortunes for companies in the clinical trial area with Antares, Lilly and Biogen all reporting positive late clinical stage trials but Clovis reporting disappointing results for its lipid-conjugated metastatic pancreatic cancer product, CO-101. On the merger and acquisitions front Immune and EpiCyte agreed to merge and Reddy’s indicated that it wishes to acquire the Dutch company OctoPlus. Alnylam announced that it had finally resolved all on-going litigation over its lipid nanoparticle technology for RNAi therapeutics by agreeing to pay US$30 million to Tekmira to secure rights to manufacture its own lipid nanoparticle-based products.

Drug‐induced QT interval prolongation: does ethnicity of the thorough QT study population matter?

Inter-ethnic differences in drug responses have been well documented. Drug-induced QT interval prolongation is a major safety concern and therefore, regulatory authorities recommend a clinical thorough QT study (TQT) to investigate new drugs for their QT-prolonging potential. A positive study, determined by breach of a preset regulatory threshold, significantly influences late phase clinical trials by requiring intense ECG monitoring. A few studies that are currently available, although not statistically conclusive at present, question the assumption that ethnicity of the study population may not influence the outcome of a TQT study. Collective consideration of available pharmacogenetic and clinical information suggests that there may be inter-ethnic differences in QT-prolonging effects of drugs and that Caucasians may be more sensitive than other populations. The information also suggest s that (a) these differences may depend on the QT-prolonging potency of the drug and (b) exposure-response (E-R) analysis may be more sensitive than simple changes in QT(c) interval in unmasking this difference. If the QT response in Caucasians is generally found to be more intense than in non-Caucasians, there may be significant regulatory implications for domestic acceptance of data from a TQT study conducted in foreign populations. However, each drug will warrant an individual consideration when extrapolating the results of a TQT study from one ethnic population to another and the ultimate clinical relevance of any difference. Further adequately designed and powered studies, investigating the pharmacologic properties and E-R relationships of additional drugs with different potencies, are needed in Caucasians, Oriental/Asian and African populations before firm conclusions can be drawn.

Designing an adaptive phase II/III trial to evaluate efficacy, safety and immune correlates of new TB vaccines in young adults and adolescents

This article summarises the consensus arrived at a meeting of South African and international stakeholders on specific late phase clinical trial design issues integrating the investigation of immune correlates as an integral part of a phase III protocol for a preventative TB vaccine in an adolescent/adult population. The challenge ahead is to optimize the planning for phase 3 TB vaccine preventative trials, under resource constraints, given that there are no known correlates of protection to shorten and increase the efficiencies of efficacy trials. An adaptive, multi-arm, group sequentially designed trial protocol is proposed incorporating design features that address uncertainties arising from both advances in the field and dynamic study populations and disease states. Such a design allows modifications that protect research subjects, save time, and maximize the impact of scarce financial resources. Further, the protocol underwent joint review by regulators from several African nations at a meeting of the African Vaccine Regulatory Forum (AVAREF), a regional regulatory harmonization initiative, and recommendations are included.

Stress response pathways, toxicity pathways and adverse outcome pathways

The aim of this editorial is to address ambiguities and misconceptions regarding the terms stress response pathways, toxicity pathways and adverse outcome pathways. A large number of tightly regulated stress response pathways have evolved to allow cells to cope with and manage different types of cell stress. The purpose of these pathways is to maintain or reinstate homoeostasis in the face of perturbations of particular cellular processes. Here, I give a few well-characterised examples [for an in-depth review of these and other stress response pathways see (Jennings et al. 2012)]. The granddaddy of stress response pathways is the p53 pathway. It is considered a gatekeeper of DNA integrity, preventing cells with compromised DNA from proliferating further and thus can be considered a DNA damage stress response. Its activation induces the transcription of genes which, depending on the context lead to cell cycle arrest, senescence or apoptosis. Failure of the p53 pathway to engage correctly allows the propagation of cells with unstable DNA and is one of the major initiators of cancer development. The Nrf2 pathway is the main oxidative stress response and thus also of high importance to the field of toxicology. The activation of this pathway induces the transcription of genes involved in glutathione synthesis, glutathione recycling and detoxification. The lack of appropriate Nrf2 activation would result in a rapid depletion of glutathione leading to cell death at ordinarily tolerable concentrations of oxidant. This is illustrated in Nrf2 knockout mice, which are far more sensitive to acetaminophen than wild type mice (Enomoto et al. 2001). Harnessing the Nrf2 pathway also has therapeutic potential. Indeed, activation of Nrf2 via modification of its inhibitor KEAP-1 with bardoxolone methyl is in late clinical trials for the treatment of chronic renal disease progression (Crunkhorn 2012). The unfolded protein response (UPR) is activated by perturbations in the endoplasmic reticulum (ER) environment or due to protein overloading, collectively termed ER stress. The pathway temporarily shuts down protein translation and activates three transcriptional master regulators, ATF4, ATF6 and XBP1. These transcription factors have specific roles in the restoration of translation, increasing molecular chaperones and induction of both amino acid utilisation and aminoacyl tRNA synthetases. Several other stress response pathways have been identified, including the hypoxic stress response (regulated by hypoxia inducible factor) and the heavy metal stress response (regulated by metal responsive transcription factor). In the context of toxicology, it is important to remember that these stress response pathways are not the perturbation but the response to the perturbation. A toxicity pathway was defined in the National Research Council’s (NRC), Toxicity testing in the 21st century: a vision and a strategy, as ‘‘cellular response pathways that, when sufficiently perturbed in an intact animal, are expected to result in adverse health effects’’ (NRC 2007). This would by definition exclude stress response pathways as (1) their activation is a normal biological response to a specific stimulus not a perturbation and (2) they function to protect the cell or the tissue. However, I am certain the authors did not mean to exclude stress response pathways, especially since in a follow-up review the Nrf2 pathway was used to illustrate the toxicity pathway concept (Krewski et al. 2010). Adverse outcome pathways (AOPs) were first described in the field of ecotoxicology as ‘‘a P. Jennings (&) Division of Physiology, Department of Physiology and Medical Physics, Innsbruck Medical University, Fritz-Pregl Strasse 3/1, 6020 Innsbruck, Austria e-mail: paul.jennings@i-med.ac.at; paul.other@gmail.com URL: http://physiologie.i-med.ac.at/jennings

Viruses in cancer treatment

Soon after the discovery that viruses cause human disease, started the idea of using viruses to treat cancer. After the initial indiscriminate use, crude preparations of each novel virus in the early twentieth century, a second wave of virotherapy blossomed in the 60s with purified and selected viruses. Responses were rare and short-lived. Immune rejection of the oncolytic viruses was identified as the major problem and virotherapy was abandoned. During the past two decades virotherapy has re-emerged with engineered viruses, with a trend towards using them as tumor-debulking immunostimulatory agents combined with radio or chemotherapy. Currently, oncolytic Reovirus, Herpes, and Vaccinia virus are in late phase clinical trials. Despite the renewed hope, efficacy will require improving systemic tumor targeting, overcoming stroma barriers for virus spread, and selectively stimulating immune responses against tumor antigens but not against the virus. Virotherapy history, viruses, considerations for clinical trials, and hurdles are briefly overviewed.