A Multicentre, Randomised, Double-Blind, Placebo-Controlled, Parallel-Group Study to Evaluate the Efficacy and Safety of Sirukumab in the Treatment of Giant Cell Arteritis.

INTRODUCTION: To evaluate the efficacy and safety of sirukumab in giant cell arteritis (GCA). METHODS: In this multicentre, randomised, double-blind, placebo-controlled, two-part phase 3 trial (NCT02531633; Part A [52-week double-blind treatment]; Part B [104-week follow-up]), patients with GCA were randomised (3:3:2:2:2) to sirukumab 100 mg every 2 weeks plus 6-month or 3-month prednisone taper, sirukumab 50 mg every 4 weeks plus 6-month prednisone taper, or placebo every 2 weeks plus 6-month or 12-month prednisone taper. The primary endpoint was the proportion of patients in sustained remission at week 52. Secondary endpoints included disease flare and safety. The study was terminated early (October 2017; sponsor decision). RESULTS: Of 161 patients randomised (sirukumab: n = 107; placebo: n = 54), 28 (17.4%) completed week 52 (median treatment duration: 24-30 weeks). In a revised intent-to-treat (ITT) subgroup (completed week 52 or discontinued before study termination [n = 55]); six patients (all receiving sirukumab) achieved the primary endpoint. In the ITT population (n = 161), the proportion of patients with flares (week 2-52) was lower with sirukumab (18.4-30.8%) than placebo (37.0-40.0%). The proportion of patients with flares (week 2-12) was highest with sirukumab 100 mg every 2 weeks plus 3-month prednisone taper (23.1%). In Part A, 94.4% of patients reported ≥ 1 treatment-emergent adverse event (TEAE); 19.3% reported serious TEAEs. The proportions of patients with TEAEs were generally similar across treatment arms. No deaths occurred. CONCLUSIONS: Although data were limited due to early termination and shortened treatment duration, sirukumab treatment resulted in numerically lower proportions of patients with flare by week 52 versus placebo, with no unexpected safety findings. TRIAL REGISTRATION: Clinicaltrials.gov: NCT02531633.

Key design considerations on comparative clinical efficacy studies for biosimilars: adalimumab as an example.

The global development of a biosimilar product is a methodologically complex affair, lined with potential design pitfalls and operational missteps to be avoided. Without careful attention to experimental design and meticulous execution, a development programme may fail to demonstrate equivalence, as would be anticipated for a biosimilar product, and not receive regulatory approval based on current guidance. In order to demonstrate similarity of a biosimilar product versus the originator (ie, the branded product), based on regulatory guidance, a stepwise approach is usually taken, starting with a comprehensive structural and functional characterisation of the new biological moiety. Given the sequential nature of the review process, the extent and nature of the non-clinical in vivo studies and the clinical studies to be performed depend on the level of evidence obtained in these previous step(s). A clinical efficacy trial is often required to further demonstrate biosimilarity of the two products (biosimilar vs branded) in terms of comparative safety and effectiveness. Owing to the focus on demonstrating biosimilarity and not safety and efficacy de novo, designing an adequate phase III (potentially pivotal) clinical efficacy study of a biosimilar may present some unique challenges. Using adalimumab as an example, we highlight design elements that may deserve special attention.

Demonstrating Value for Biosimilars: A Conceptual Framework.

BACKGROUND: The value proposition for biosimilars can be characterized as a concept that moves beyond the argument of cost reduction relative to the innovator biologic drug and into a framework that incorporates the diverse needs of key healthcare stakeholders during the transition from clinical development to commercialization in the marketplace. OBJECTIVES: To identify factors that facilitate and inhibit the development, commercialization, and adoption of biosimilars, and to recommend modifications in program design that are likely to support the demonstration of the value of biosimilars for payers, providers, and patients. METHODS: The primary data sources for this article include surveys conducted by Boston Healthcare Associates with payers and clinicians in the United States and the European Union 5 markets and blinded international protocol feasibility assessments completed by Worldwide Clinical Trials. Survey methodology used either convenience or purposeful sampling as appropriate, with participants extracted from diverse audiences, representative of those who generate or evaluate clinical data shaping the economic exchange and preferential status influencing physician adoption and patient access to biosimilars. Patient characteristics and psychosocial issues influencing patients' perception of small-molecule generics were extracted from the available literature to inform exploratory hypotheses, given the relative absence of such information for biosimilars. DISCUSSION: This article reviews the current evidence and summarizes results of surveys conducted with payers, providers, and drug investigation sites in the United States. Based on a review of published literature, as well as these survey results, conflicting and convergent demands exist for gathering data related to biosimilars. The motivations and data needs for these new agents are diverse, requiring adjudication of regulatory, economic, and clinical incentives beginning at program inception and extending through commercialization of the final biosimilar agent. CONCLUSIONS: The development and commercialization of biosimilars represent an international activity that can encounter unanticipated challenges, as well as opportunities to achieve clinical and commercial success. Evolving regulatory guidance mapped in relation to payer, physician, and patient sentiments may inform the biosimilar development program designs, implementation, and positioning of the new drug.

Discovery and characterization of a cell-permeable, small-molecule c-Abl kinase activator that binds to the myristoyl binding site.

c-Abl kinase activity is regulated by a unique mechanism involving the formation of an autoinhibited conformation in which the N-terminal myristoyl group binds intramolecularly to the myristoyl binding site on the kinase domain and induces the bending of the αI helix that creates a docking surface for the SH2 domain. Here, we report a small-molecule c-Abl activator, DPH, that displays potent enzymatic and cellular activity in stimulating c-Abl activation. Structural analyses indicate that DPH binds to the myristoyl binding site and prevents the formation of the bent conformation of the αI helix through steric hindrance, a mode of action distinct from the previously identified allosteric c-Abl inhibitor, GNF-2, that also binds to the myristoyl binding site. DPH represents the first cell-permeable, small-molecule tool compound for c-Abl activation.

Postapproval Development Options in COPD: A Case Study in Value-Based Healthcare Systems.

BACKGROUND: Research and development activities in an era of globalization encounter a mosaic of providers, products, services, and intermediaries; regulatory and other government institutions; and consumers. The introduction of novel therapeutics into this environment mandates research programs that are relevant to the registration process, payers and purchasers, transparent pricing, and rule-driven business practices, while providing data relevant to marketing initiatives internationally. OBJECTIVE: To outline an example for clinical development programs that incorporate the perspective of multiple stakeholders into a portfolio of study designs to provide optimal data platforms that can resonate with diverse recipients. DISCUSSION: A contract research organization directly involved in the design, execution, and analysis of clinical trials for new drugs and devices across pharmaceutical and biotechnology companies provides a unique perspective regarding opportunities and challenges within the international clinical research environment. Drs Murphy, Antonini, and Lai, representing Worldwide Clinical Trials, utilize chronic obstructive pulmonary disease as a demonstration project exploiting its prevalence, direct and indirect costs, and the rapid infusion/diffusion of innovative therapy into practice as a rationale for focus, and illustrate methods of informing registration and technology assessments during a prototypical development process. CONCLUSION: By virtue of its chronicity, prevalence, and pattern of healthcare utilization, chronic obstructive pulmonary disease provides an ideal case for illustrating the application of clinical trial methodology that can facilitate data evaluation through the prism of multiple stakeholders. Adding an international dimension exacerbates system complexity and serves to illustrate the breadth of issues that can be addressed within this therapeutic area.

C-terminal region of USP7/HAUSP is critical for deubiquitination activity and contains a second mdm2/p53 binding site.

USP7, also known as the hepes simplex virus associated ubiquitin-specific protease (HAUSP), deubiquitinates both mdm2 and p53, and plays an important role in regulating the level and activity of p53. Here, we report that deletion of the TRAF-like domain at the N-terminus of USP7, previously reported to contain the mdm2/p53 binding site, has no effect on USP7 mediated deubiquitination of Ub(n)-mdm2 and Ub(n)-p53. Amino acids 208-1102 were identified to be the minimal length of USP7 that retains proteolytic activity, similar to full length enzyme, towards not only a truncated model substrate Ub-AFC, but also Ub(n)-mdm2, Ub(n)-p53. In contrast, the catalytic domain of USP7 (amino acids 208-560) has 50-700 fold less proteolytic activity towards different substrates. Moreover, inhibition of the catalytic domain of USP7 by Ubal is also different from the full length or TRAF-like domain deleted proteins. Using glutathione pull-down methods, we demonstrate that the C-terminal domain of USP7 contains additional binding sites, a.a. 801-1050 and a.a. 880-1050 for mdm2 and p53, respectively. The additional USP7 binding site on mdm2 is mapped to be the C-terminal RING finger domain (a.a. 425-491). We propose that the C-terminal domain of USP7 is responsible for maintaining the active conformation for catalysis and inhibitor binding, and contains the prime side of the proteolytic active site.

Discovery of GSK1070916, a potent and selective inhibitor of Aurora B/C kinase.

The Aurora kinases play critical roles in the regulation of mitosis and are frequently overexpressed or amplified in human tumors. Selective inhibitors may provide a new therapy for the treatment of tumors with Aurora kinase amplification. Herein we describe our lead optimization efforts within a 7-azaindole-based series culminating in the identification of GSK1070916 (17k). Key to the advancement of the series was the introduction of a 2-aryl group containing a basic amine onto the azaindole leading to significantly improved cellular activity. Compound 17k is a potent and selective ATP-competitive inhibitor of Aurora B and C with K(i)* values of 0.38 +/- 0.29 and 1.5 +/- 0.4 nM, respectively, and is >250-fold selective over Aurora A. Biochemical characterization revealed that compound 17k has an extremely slow dissociation half-life from Aurora B (>480 min), distinguishing it from clinical compounds 1 and 2. In vitro treatment of A549 human lung cancer cells with compound 17k results in a potent antiproliferative effect (EC(50) = 7 nM). Intraperitoneal administration of 17k in mice bearing human tumor xenografts leads to inhibition of histone H3 phosphorylation at serine 10 in human colon cancer (Colo205) and tumor regression in human leukemia (HL-60). Compound 17k is being progressed to human clinical trials.

2,3,5-Trisubstituted pyridines as selective AKT inhibitors. Part II: Improved drug-like properties and kinase selectivity from azaindazoles.

A novel series of AKT inhibitors containing 2,3,5-trisubstituted pyridines with novel azaindazoles as hinge binding elements are described. Among these, the 4,7-diazaindazole compound 2c has improved drug-like properties and kinase selectivity than those of indazole 1, and displays greater than 80% inhibition of GSK3beta phosphorylation in a BT474 tumor xenograft model in mice.

2,3,5-Trisubstituted pyridines as selective AKT inhibitors-Part I: Substitution at 2-position of the core pyridine for ROCK1 selectivity.

2,3,5-Trisubstituted pyridines have been designed as potent AKT inhibitors that are selective against ROCK1 based on the comparison between AKT and ROCK1 structures. Substitution at the 2-position of the core pyridine is the key element to provide selectivity against ROCK1. An X-ray co-crystal structure of 9p in PKA supports the proposed rationale of ROCK1 selectivity.

Tetrasubstituted pyridines as potent and selective AKT inhibitors: Reduced CYP450 and hERG inhibition of aminopyridines.

The synthesis and evaluation of tetrasubstituted aminopyridines, bearing novel azaindazole hinge binders, as potent AKT inhibitors are described. Compound 14c was identified as a potent AKT inhibitor that demonstrated reduced CYP450 inhibition and an improved developability profile compared to those of previously described trisubstituted pyridines. It also displayed dose-dependent inhibition of both phosphorylation of GSK3beta and tumor growth in a BT474 tumor xenograft model in mice.

GSK1070916, a potent Aurora B/C kinase inhibitor with broad antitumor activity in tissue culture cells and human tumor xenograft models.

The protein kinases, Aurora A, B, and C have critical roles in the regulation of mitosis and are frequently overexpressed or amplified in human tumors. GSK1070916, is a novel ATP competitive inhibitor that is highly potent and selective for Aurora B/C kinases. Human tumor cells treated with GSK1070916 show dose-dependent inhibition of phosphorylation on serine 10 of Histone H3, a substrate specific for Aurora B kinase. Moreover, GSK1070916 inhibits the proliferation of tumor cells with EC(50) values of <10 nmol/L in over 100 cell lines spanning a broad range of tumor types. Although GSK1070916 has potent activity against proliferating cells, a dramatic shift in potency is observed in primary, nondividing, normal human vein endothelial cells, consistent with the proposed mechanism. We further determined that treated cells do not arrest in mitosis but instead fail to divide and become polyploid, ultimately leading to apoptosis. GSK1070916 shows dose-dependent inhibition of phosphorylation of an Aurora B-specific substrate in mice and consistent with its broad cellular activity, has antitumor effects in 10 human tumor xenograft models including breast, colon, lung, and two leukemia models. These results show that GSK1070916 is a potent Aurora B/C kinase inhibitor that has the potential for antitumor activity in a wide range of human cancers.

Evidence for allosteric interactions of antagonist binding to the smoothened receptor.

The Smoothened receptor (Smo) mediates hedgehog (Hh) signaling critical for development, cell growth, and migration, as well as stem cell maintenance. Aberrant Hh signaling pathway activation has been implicated in a variety of cancers, and small-molecule antagonists of Smo have entered human clinical trials for the treatment of cancer. Here, we report the biochemical characterization of allosteric interactions of agonists and antagonists for Smo. Binding of two radioligands, [(3)H]3-chloro-N-[trans-4-(methylamino)cyclohexyl]-N-{[3-(4-pyridinyl)-phenyl]methyl}-1-benzothiophene-2-carboxamide (SAG-1.3) (agonist) and [(3)H]cyclopamine (antagonist), was characterized using human Smo expressed in human embryonic kidney 293F membranes. We observed full displacement of [(3)H]cyclopamine by all Smo agonist and antagonist ligands examined. N-[(1E)-(3,5-Dimethyl-1-phenyl-1H-pyrazol-4-yl)methylidene]-4-(phenylmethyl)-1-piperazinamine (SANT-1), an antagonist, did not fully inhibit the binding of [(3)H]SAG-1.3. In a functional cell-based beta-lactamase reporter gene assay, SANT-1 and N-[3-(1H-benzimidazol-2-yl)-4-chlorophenyl]-3,4,5-tris(ethyloxy)-benzamide (SANT-2) fully inhibited 3-chloro-4,7-difluoro-N-[trans-4-(methylamino)cyclohexyl]-N-{[3-(4-pyridinyl)phenyl]methyl}-1-benzothiophene-2-carboxamide (SAG-1.5)-induced Hh pathway activation. Detailed "Schild-type" radioligand binding analysis with [(3)H]SAG-1.3 revealed that two structurally distinct Smoothened receptor antagonists, SANT-1 and SANT-2, bound in a manner consistent with that of allosteric modulation. Our mechanism of action characterization of radioligand binding to Smo combined with functional data provides a better understanding of small-molecule interactions with Smo and their influence on the Hh pathway.

Biochemical characterization of GSK1070916, a potent and selective inhibitor of Aurora B and Aurora C kinases with an extremely long residence time1.

The Aurora kinases AurA, B and C are serine/threonine protein kinases that play essential roles in mitosis and cytokinesis. Among them, AurB is required for maintaining proper chromosome alignment, separation and segregation during mitosis, and regulating a number of critical processes involved in cytokinesis. AurB overexpression has been observed in a variety of cancer cell lines, and inhibition of AurB has been shown to induce tumour regression in mouse xenograft models. In the present study we report the enzymatic characterization of a potent and selective AurB/AurC inhibitor. GSK1070916 is a reversible and ATP-competitive inhibitor of the AurB-INCENP (inner centromere protein) enzyme. It selectively inhibits AurB-INCENP (K(i)*=0.38+/-0.29 nM) and AurC-INCENP (K(i)*=1.5+/-0.4 nM) over AurA-TPX2 (target protein for Xenopus kinesin-like protein 2) (K(i)=490+/-60 nM). Inhibition of AurB-INCENP and AurC-INCENP is time-dependent, with an enzyme-inhibitor dissociation half-life of >480 min and 270+/-28 min respectively. The extremely slow rate of dissociation from the AurB and AurC enzymes distinguishes GSK1070916 from two other Aurora inhibitors in the clinic, AZD1152 and VX-680 (also known as MK-0457).

Defining balanced conditions for inhibitor screening assays that target bisubstrate enzymes.

High-throughput screening (HTS) is a common mechanism for identifying lead compounds for drug discovery efforts. Small molecules can inhibit enzymes by a variety of mechanisms, such as competitive, noncompetitive, and uncompetitive with respect to the substrate(s) of the catalytic reaction. To optimize the chances of finding the broadest diversity of inhibitor modalities during screening, one must run assays under ;;balanced'' conditions where the potency of inhibitors with various modes of action falls within a similar range. When an enzyme reaction involves more than one substrate, the definition and assessment of the apparent potency of inhibitors (IC(50)), in relation to their true potency (K(i)), can be nontrivial. This article provides a theoretical analysis, on the basis of the Cheng-Prusoff derivation, of the IC(50)/K( i) relationship of bisubstrate enzyme reactions following various sequential kinetic mechanisms, as well as the application and limitations of this information for defining optimal screening conditions for such enzymes.

The catalytic role of INCENP in Aurora B activation and the kinetic mechanism of Aurora B/INCENP.

Aurora kinases are a family of serine/threonine protein kinases that play essential roles in mitosis and cytokinesis. AurB (Aurora B kinase) has shown a clear link to cancer and is being pursued as an attractive cancer target. Multiple small molecules targeting AurB have entered the clinic for the treatment of cancer. A protein cofactor, INCENP (inner centromere protein), regulates the cellular localization and activation of AurB. In the present study, we examined the effect of INCENP on the activation kinetics of AurB and also elucidated the kinetic mechanism of AurB-catalysed substrate phosphorylation. We have concluded that: (i) substoichoimetric concentrations of INCENP are sufficient for AurB autophosphorylation at the activation loop residue Thr(232), and hence INCENP plays a catalytic role in AurB autophosphorylation; (ii) AurB/INCENP-catalysed phosphorylation of a peptide substrate proceeds through a rapid equilibrium random Bi Bi kinetic mechanism; and (iii) INCENP has relatively minor effects on the specific activity of AurB using a peptide substrate when compared with its role in AurB autoactivation. These results indicate that the effects of INCENP, and probably accessory proteins in general, may differ when enzymes are acting on different downstream targets.

Identification of 4-(2-(4-amino-1,2,5-oxadiazol-3-yl)-1-ethyl-7-{[(3S)-3-piperidinylmethyl]oxy}-1H-imidazo[4,5-c]pyridin-4-yl)-2-methyl-3-butyn-2-ol (GSK690693), a novel inhibitor of AKT kinase.

Overexpression of AKT has an antiapoptotic effect in many cell types, and expression of dominant negative AKT blocks the ability of a variety of growth factors to promote survival. Therefore, inhibitors of AKT kinase activity might be useful as monotherapy for the treatment of tumors with activated AKT. Herein, we describe our lead optimization studies culminating in the discovery of compound 3g (GSK690693). Compound 3g is a novel ATP competitive, pan-AKT kinase inhibitor with IC 50 values of 2, 13, and 9 nM against AKT1, 2, and 3, respectively. An X-ray cocrystal structure was solved with 3g and the kinase domain of AKT2, confirming that 3g bound in the ATP binding pocket. Compound 3g potently inhibits intracellular AKT activity as measured by the inhibition of the phosphorylation levels of GSK3beta. Intraperitoneal administration of 3g in immunocompromised mice results in the inhibition of GSK3beta phosphorylation and tumor growth in human breast carcinoma (BT474) xenografts.

Modulation of kinase-inhibitor interactions by auxiliary protein binding: crystallography studies on Aurora A interactions with VX-680 and with TPX2.

VX-680, also known as MK-0457, is an ATP-competitive small molecule inhibitor of the Aurora kinases that has entered phase II clinical trials for the treatment of cancer. We have solved the cocrystal structure of AurA/TPX2/VX-680 at 2.3 A resolution. In the crystal structure, VX-680 binds to the active conformation of AurA. The glycine-rich loop in AurA adopts a unique bent conformation, forming a pi-pi interaction with the phenyl group of VX-680. In contrast, in the published AurA/VX-680 structure, VX-680 binds to AurA in the inactive conformation, interacting with a hydrophobic pocket only present in the inactive conformation. These data suggest that TPX2, a protein cofactor, can alter the binding mode of VX-680 with AurA. More generally, the presence of physiologically relevant cofactor proteins can alter the kinetics, binding interactions, and inhibition of enzymes, and studies with these multiprotein complexes may be beneficial to the discovery and optimization of enzyme inhibitors as therapeutic agents.

Characterization of an Akt kinase inhibitor with potent pharmacodynamic and antitumor activity.

Akt kinases 1, 2, and 3 are important regulators of cell survival and have been shown to be constitutively active in a variety of human tumors. GSK690693 is a novel ATP-competitive, low-nanomolar pan-Akt kinase inhibitor. It is selective for the Akt isoforms versus the majority of kinases in other families; however, it does inhibit additional members of the AGC kinase family. It causes dose-dependent reductions in the phosphorylation state of multiple proteins downstream of Akt, including GSK3 beta, PRAS40, and Forkhead. GSK690693 inhibited proliferation and induced apoptosis in a subset of tumor cells with potency consistent with intracellular inhibition of Akt kinase activity. In immune-compromised mice implanted with human BT474 breast carcinoma xenografts, a single i.p. administration of GSK690693 inhibited GSK3 beta phosphorylation in a dose- and time-dependent manner. After a single dose of GSK690693, >3 micromol/L drug concentration in BT474 tumor xenografts correlated with a sustained decrease in GSK3 beta phosphorylation. Consistent with the role of Akt in insulin signaling, treatment with GSK690693 resulted in acute and transient increases in blood glucose level. Daily administration of GSK690693 produced significant antitumor activity in mice bearing established human SKOV-3 ovarian, LNCaP prostate, and BT474 and HCC-1954 breast carcinoma xenografts. Immunohistochemical analysis of tumor xenografts after repeat dosing with GSK690693 showed reductions in phosphorylated Akt substrates in vivo. These results support further evaluation of GSK690693 as an anticancer agent.

Binding of TPX2 to Aurora A alters substrate and inhibitor interactions.

The Aurora kinases are a family of serine/threonine kinases involved in mitosis. The expression of AurA is ubiquitous and cell cycle regulated. It is overexpressed in many tumor types, including breast, colon, and ovarian. TPX2 is a binding partner and activator of AurA. A fragment of TPX2 (residues 1-43) has been shown to be sufficient for binding, kinase activation, and protection from dephosphorylation. We have shown that the addition of TPX2(1-43) increases the catalytic efficiency of AurA. While TPX2 binding has no effect on the turnover number of AurA and does not change the reaction mechanism (characterized here to be a rapid equilibrium random mechanism), it increases the binding affinity of both ATP and a peptide substrate. We have also demonstrated differences in the inhibitor structure-activity relationship (SAR) in the presence or absence of TPX2(1-43). To better understand the differential SAR, we carried out computer modeling studies to gain insight into the effect of TPX2 on the binding interactions between AurA and inhibitors. Our working hypothesis is that TPX2 binding decreases the size and accessibility of a hydrophobic pocket, adjacent to the ATP site, to inhibitors.

A second p53 binding site in the central domain of Mdm2 is essential for p53 ubiquitination.

Mdm2 negatively regulates p53 by inhibiting its transcriptional activity and promoting its degradation by functioning as an E3 ubiquitin ligase. The primary p53 binding site on mdm2 is located in its N-terminal domain. Through binding to p53 at its N-terminal transactivation domain, mdm2 directly blocks the transcriptional activation function of p53. We discovered that truncated mdm2 protein constructs without the N-terminal p53 binding domain are at least as active as full-length mdm2 in catalyzing p53 ubiquitination. Furthermore, the deletion of the central acidic domain significantly reduces the E3 ligase activity of mdm2 toward p53. We have also performed GST pull-down experiments to probe the direct binding of various mdm2 domain constructs toward full length p53 and found that mdm2 constructs without the N-terminal p53 binding domain retain the ability to bind to p53. Our kinetic and binding data localize the second p53 binding site between amino acids 211 and 361, including the acidic domain and the zinc finger region. Our work, consistent with other reports, suggests that the p53 tetramer interacts with at least two sites on mdm2. Although the interaction between the N-termini of mdm2 and p53 blocks the transactivation activity of p53, the interaction between the central domain of mdm2 and the core domain of p53 is critical for the ubiquitination and degradation of p53. This second mdm2-p53 interaction site represents an alternative target for small molecule modulators of the mdm2-p53 pathway.