Membrane-Anchored HIV-1 N-Heptad Repeat Peptides Are Highly Potent Cell Fusion Inhibitors via an Altered Mode of Action

Peptide inhibitors derived from HIV-gp41 envelope protein play a pivotal role in deciphering the molecular mechanism of HIV-cell fusion. According to accepted models, N-heptad repeat (NHR) peptides can bind two targets in an intermediate fusion conformation, thereby inhibiting progression of the fusion process. In both cases the orientation towards the endogenous intermediate conformation should be important. To test this, we anchored NHR to the cell membrane by conjugating fatty acids with increasing lengths to the N- or C-terminus of N36, as well as to two known N36 mutants; one that cannot bind C-heptad repeat (CHR) but can bind NHR (N36 MUTe,g), and the second cannot bind to either NHR or CHR (N36 MUTa,d). Importantly, the IC50 increased up to 100-fold in a lipopeptide-dependent manner. However, no preferred directionality was observed for the wild type derived lipopeptides, suggesting a planar orientation of the peptides as well as the endogenous NHR region on the cell membrane. Furthermore, based on: (i) specialized analysis of the inhibition curves, (ii) the finding that N36 conjugates reside more on the target cells that occupy the receptors, and (iii) the finding that N36 MUTe,g acts as a monomer both in its soluble form and when anchored to the cell membrane, we suggest that anchoring N36 to the cell changes the inhibitory mode from a trimer which can target both the endogenous NHR and CHR regions, to mainly monomeric lipopetides that target primarily the internal NHR. Besides shedding light on the mode of action of HIV-cell fusion, the similarity between functional regions in the envelopes of other viruses suggests a new approach for developing potent HIV-1 inhibitors

Autothermal reforming of palm empty fruit bunch bio-oil: thermodynamic modelling

This work focuses on thermodynamic analysis of the autothermal reforming of palm empty fruit bunch (PEFB) bio-oil for the production of hydrogen and syngas. PEFB bio-oil composition was simulated using bio-oil surrogates generated from a mixture of acetic acid, phenol, levoglucosan, palmitic acid and furfural. A sensitivity analysis revealed that the hydrogen and syngas yields were not sensitive to actual bio-oil composition, but were determined by a good match of molar elemental composition between real bio-oil and surrogate mixture. The maximum hydrogen yield obtained under constant reaction enthalpy and pressure was about 12 wt% at S/C = 1 and increased to about 18 wt% at S/C = 4; both yields occurring at equivalence ratio Φ of 0.31. The possibility of generating syngas with varying H2 and CO content using autothermal reforming was analysed and application of this process to fuel cells and Fischer-Tropsch synthesis is discussed. Using a novel simple modelling methodology, reaction mechanisms were proposed which were able to account for equilibrium product distribution. It was evident that different combinations of reactions could be used to obtain the same equilibrium product concentrations. One proposed reaction mechanism, referred to as the ‘partial oxidation based mechanism’ involved the partial oxidation reaction of the bio-oil to produce hydrogen, with the extent of steam reforming and water gas shift reactions varying depending on the amount of oxygen used. Another proposed mechanism, referred to as the ‘complete oxidation based mechanism’ was represented by thermal decomposition of about 30% of bio-oil and hydrogen production obtained by decomposition, steam reforming, water gas shift and carbon gasification reactions. The importance of these mechanisms in assisting in the eventual choice of catalyst to be used in a real ATR of PEFB bio-oil process was discussed

Preventing vasospasm improves outcome after aneurysmal subarachnoid hemorrhage: rationale and design of CONSCIOUS-2 and CONSCIOUS-3 trials

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH) is a frequent but unpredictable complication associated with poor outcome. Current vasospasm therapies are suboptimal; new therapies are needed. Clazosentan, an endothelin receptor antagonist, has shown promise in phase 2 studies, and two randomized, double-blind, placebo-controlled phase 3 trials (CONSCIOUS-2 and CONSCIOUS-3) are underway to further investigate its impact on vasospasm-related outcome after aSAH. Here we describe the design of these studies, which was challenging with respect to defining endpoints and standardizing endpoint interpretation and patient care. Main inclusion criteria are: age 18–75 years; SAH due to ruptured saccular aneurysm secured by surgical clipping (CONSCIOUS-2) or endovascular coiling (CONSCIOUS-3); substantial subarachnoid clot; and World Federation of Neurosurgical Societies grades I-IV prior to aneurysm-securing procedure. In CONSCIOUS-2, patients are randomized 2:1 to clazosentan (5mg/h) or placebo. In CONSCIOUS-3, patients are randomized 1:1:1 to clazosentan 5mg/h, 15mg/h or placebo. Treatment is initiated within 56 h of aSAH and continued until 14 days after aSAH. Primary endpoint is a composite of mortality and vasospasm-related morbidity within 6 weeks of aSAH (all-cause mortality, vasospasm-related new cerebral infarction, vasospasm-related delayed ischemic neurological deficit, neurological signs or symptoms in the presence of angiographic vasospasm leading to rescue therapy initiation). Main secondary endpoint is extended Glasgow Outcome Scale (GOSE) at week 12. A critical events committee assesses all data centrally to ensure consistency in interpretation, and patient management guidelines are used to standardize care. Results are expected at the end of 2010 and 2011 for CONSCIOUS-2 and CONSCIOUS-3, respectively. Introduction Advances have been made in the management of patients with aneurysmal subarachnoid hemorrhage (aSAH). Mortality among those who reach hospital alive has decreased 0.9% per year since 1980 [1]. Nevertheless, case fatality is still 40% and half of all survivors suffer some form of physical, emotional or cognitive impairment [2–4]. The causes of morbidity and mortality are mainly initial effects of the aSAH and delayed ischemic neurological deficit (DIND), which is usually due to cerebral vasospasm [5]. Indeed, vasospasm is considered to be one of the main preventable causes of morbidity and mortality [6]. Angiographic vasospasm (vasospasm that is visible on an angiogram) occurs in up to 70% of patients after aSAH [6]; DIND has been estimated to account for 50% of deaths in people surviving the initial SAH [7]. Current management options for the prevention and treatment of vasospasm and DIND include hemodynamic therapy, nimodipine, fasudil (in Japan), intra-arterial vasodilators and angioplasty, but none are very effective [7–12]. Clazosentan is an endothelin receptor antagonist under investigation for the prevention of vasospasm and subsequent morbidity and mortality. A phase 2a proof-of-principle trial administered 0.2 mg/kg/h clazosentan (corresponding to 15 mg/h for an individual weighing 75 kg) beginning within 48 h of the aneurysm securing procedure and continuing until Day 14 after aSAH. Clazosentan reduced moderate/severe angiographic vasospasm by 55% relative to placebo (angiographic vasospasm was observed in 88% and 40% of placebo- and clazosentan-treated patients, respectively, P = 0.008) [13]. These results supported conduct of a dose-finding safety trial (Clazosentan to Overcome Neurological iSChemia and Infarct OccUrring after Subarachnoid hemorrhage CONSCIOUS-1; phase 2b]). The primary outcome was angiographic vasospasm. The sample size was estimated from the effect on angiographic vasospasm in the phase 2a trial and the doses selected based on the phase 2a trial and also phase 1 clinical trials administering clazosentan to healthy volunteers and observing clinical and cardiovascular effects [13,14]. CONSCIOUS-1 recruited 413 patients from 11 countries [15]. Patients were randomized to intravenous clazosentan (1, 5 or 15 mg/h) or placebo, beginning within 56 h of aSAH and continuing until Day 14 after aneurysm rupture. Clazosentan significantly and dose-dependently reduced moderate/severe angiographic vasospasm relative to placebo; the highest dose (15 mg/h) led to a 65% risk reduction (P < 0.0001) [15]. CONSCIOUS-1 was not powered to detect a change in morbidity, mortality or patient-centered clinical outcome, but has been repeatedly and incorrectly cited as evidence that angiographic vasospasm does not contribute to poor outcome after aSAH [16]. This idea was put forth at least 35 years ago, but the basis remains as speculative now as it was then [17]. Post hoc, central analysis of all-cause mortality and vasospasm-related morbidity in CONSCIOUS-1 found a trend towards improved outcomes with clazosentan [15]. Two large, multinational phase 3 studies, CONSCIOUS-2 and CONSCIOUS-3, have now been initiated, based on the results of the CONSCIOUS-1 trial, to further investigate the effect of clazosentan on outcome after aSAH. This manuscript describes the rationale for the design and methodology of these studies. Methods Study design CONSCIOUS-2 and CONSCIOUS-3 are prospective, multinational, double-blind, placebo-controlled studies. The primary objective is to determine if clazosentan decreases vasospasm-related morbidity and all-cause mortality in patients with aSAH. Patients are randomized within 56 h of aSAH to intravenous clazosentan (5 mg/h in CONSCIOUS-2; 5 or 15 mg/h in CONSCIOUS-3) or placebo administered until Day 14 after aSAH, with a post-aSAH follow-up period of up to 12 weeks (Figure 1). Randomization is by an independent contract research organization using an interactive web response system, which assigns a randomization number according to a predefined randomization scheme. Randomization is stratified by site. In both studies, patients are managed according to procedures for aSAH at the study center (i.e., study drug is added to usual care) although patient management guidelines have been implemented (see below) to standardize care between centers. Drugs or procedures that are not standard care are forbidden including intravenous magnesium or statins when prescribed for the prevention of cerebral vasospasm, thrombolytics and antifibrinolytics, hypertonic saline without hyponatremia or increased intracranial pressure, calcineurin inhibitors, and endothelin receptor antagonists other than the study drug. Oral nimodipine is permitted, but not intravenous nimodipine or intravenous nicardipine. The study protocols are approved by local institutional review boards. The trials are registered on clinicaltrials.gov: registration numbers: NCT00558311 (CONSCIOUS-2) and NCT00940095 (CONSCIOUS-3). CONSCIOUS-2 enrolled 1157 patients in 102 centers in 27 countries; CONSCIOUS-3 is expected to enroll more than 1400 patients in approximately 150 centers in more than 25 countries. The rationale for separate studies of clipped and coiled patients was based on CONSCIOUS-1 analyses, indicating differences in endpoint occurrence when patients were stratified by securing procedure. Specifically, in CONSCIOUS-1 patients secured by clipping, the incidence of the composite endpoint in the placebo group was 45% compared with 46%, 25% and 40% in 1 mg/h, 5 mg/h and 15 mg/h groups, respectively. In contrast, in patients secured by coiling, the incidence of the composite endpoint in the placebo group was lower at 34% compared with 31%, 32% and 20% in 1 mg/h, 5 mg/h and 15 mg/h groups, respectively. Furthermore, an exploratory, retrospective analysis of CONSCIOUS-1 data showed that, relative to coiled patients, clipped patients had significantly higher rates of angiographic vasospasm (36% vs. 55%, respectively) and DIND (15% and 23%, respectively) [18]. Together these observations supported the conduct of separate trials for clipped and coiled patients and suggested that while the 5 mg/h dose might be most appropriate for clipped patients a potentially higher dose was additionally worth investigating in coiled patients