Parenteral treprostinil induction for rapid attainment of therapeutic doses of oral treprostinil.

RATIONALE: Oral treprostinil slows disease progression and improves exercise capacity in pulmonary arterial hypertension; however, titration can be prolonged. Published data suggests prostacyclin-naïve patients achieve total daily oral treprostinil doses of about 6 mg by Week 16, while those on prior parenteral treprostinil reach higher doses at the same timepoint. OBJECTIVES: EXPEDITE (NCT03497689), a single-arm, multicenter study, assessed the efficacy of rapid parenteral treprostinil induction to quickly reach higher doses of oral treprostinil for the treatment of pulmonary arterial hypertension. METHODS: Parenteral treprostinil was titrated for 2-8 weeks, followed by cross-titration of oral treprostinil. The primary endpoint was percentage of patients reaching ≥12 mg daily of oral treprostinil at Week 16. Secondary endpoints included clinical changes from baseline to Week 16. RESULTS: Twenty-nine prostacyclin-naïve patients were included in efficacy analyses. At Week 16, the mean daily oral treprostinil dose was 16.4 mg; 79% of patients met the primary endpoint. From baseline to Week 16, median REVEAL Lite 2 score improved (decreased) from 6 to 3.5 (p = 0.0006). Statistically significant improvements were also seen in World Health Organization Functional Class, N-terminal-pro brain natriuretic peptide levels, 6-minute walk distance, right atrial area, Borg Dyspnea Score, and emPHasis-10 score. Favorable trends were seen in risk stratification, echocardiography parameters, disease symptoms, and treatment satisfaction. CONCLUSION: Short-course parenteral treprostinil induction resulted in oral treprostinil doses over twice those reported in de novo initiations and may be a useful approach to quickly achieve the therapeutic benefits of oral treprostinil.

Implementing the EXPEDITE parenteral induction protocol: Rapid parenteral treprostinil titration and transition to oral treprostinil.

Treprostinil is a prostacyclin analogue that targets multiple cellular receptors to treat pulmonary arterial hypertension (PAH). In certain scenarios, patients may require aggressive treprostinil titration. Several studies have demonstrated that higher doses of treprostinil lead to greater clinical benefit. Data supports successful transitions from parenteral to oral treprostinil; however, administration routes, transition duration, and transition setting vary in the real-world. The EXPEDITE clinical trial (NCT03497689) prospectively studied whether rapid parenteral treprostinil induction can be used to achieve high doses of oral treprostinil (total daily dose: ≥12 mg) in prostacyclin naïve PAH patients. Parenteral prostacyclin induction may be more appropriate for patients who need to reach therapeutic dosing more urgently than longer titration durations reported with conventional de novo oral treprostinil initiation. This summary provides strategies utilized in EXPEDITE. Parenteral treprostinil was initiated at 2 ng/kg/min intravenously or subcutaneously; clinicians determined the frequency and dose increment of up-titration. Two distinct transition schedules from parenteral to oral treprostinil were employed: rapid cross-titration in an inpatient setting (median: 2 days) or gradual cross-titration in an outpatient setting (median: 5 days). Patient status was closely monitored after transition; oral treprostinil dose was titrated to clinical effect and tolerability. Factors considered when individualizing dosing strategies included parenteral and oral treprostinil target doses, nursing support, patient education, medication counseling and adverse events management. EXPEDITE demonstrated the time to a therapeutic dose of oral treprostinil is significantly shorter when utilizing a short-term parenteral induction strategy and may be suitable for patients requiring aggressive titration of oral treprostinil.

Safety and tolerability of transition from inhaled treprostinil to oral selexipag in pulmonary arterial hypertension: Results from the TRANSIT-1 study.

BACKGROUND: A long-term trial showed that the oral prostacyclin (PGl2) receptor (IP) agonist, selexipag, delayed disease progression in patients with pulmonary arterial hypertension (PAH). Transition to selexipag in patients treated with more burdensome inhaled therapies that target the prostacyclin pathway may be considered by patients and physicians. The Phase 3b, prospective, open-label TRANSIT-1 (Tolerability and Safety of the Transition From Inhaled Treprostinil to Oral Selexipag in Patients With Pulmonary Arterial Hypertension) study evaluated the safety and tolerability of transition from inhaled treprostinil to oral selexipag. METHODS: Patients receiving non-prostanoid oral PAH therapy and inhaled treprostinil at stable doses, in World Health Organization Functional Class II/III, with 6-minute walk distance ≥ 300 meters were enrolled. The 16-week main treatment period included downtitration of inhaled treprostinil over 8 weeks and parallel uptitration of selexipag over 12 weeks. Sustained treatment transition at Week 16 was defined as (1) receiving selexipag at Week 16; (2) no selexipag interruption(s) totaling ≥ 8 days; and (3) no inhaled treprostinil or other prostanoids after Week 8. Clinical parameters and patient-reported treatment satisfaction outcomes were assessed at Week 16. RESULTS: All 34 enrolled patients completed the study. At Week 16, 32 patients (94.1%) had stopped inhaled treprostinil and were receiving selexipag. Twenty-eight patients (82.4%) met all criteria for sustained treatment transition. During the study, 3 patients discontinued selexipag due to adverse events. Overall, most adverse events were typical of prostanoid therapies and started during the uptitration phase. In general, patients remained clinically stable throughout treatment and reported improved convenience. CONCLUSIONS: Transition to oral selexipag from inhaled treprostinil in PAH patients was successful and well tolerated in most patients, and associated with greater convenience. CLINICAL TRIAL NUMBER: NCT02471183.

Psychometric Validation of the Pulmonary Arterial Hypertension-Symptoms and Impact (PAH-SYMPACT) Questionnaire: Results of the SYMPHONY Trial.

BACKGROUND: Disease-specific patient-reported outcome (PRO) instruments are important in assessing the impact of disease and treatment. The Pulmonary Arterial Hypertension-Symptoms and Impact Questionnaire is the first instrument for quantifying pulmonary arterial hypertension (PAH) symptoms and impacts developed according to the 2009 US Food and Drug Administration PRO guidance; previous qualitative research in patients with PAH supported its initial content validity. METHODS: Content finalization and psychometric validation were conducted by using data from A Study of Macitentan in Pulmonary Arterial Hypertension to Validate the PAH-SYMPACT (SYMPHONY), a single-arm, 16-week trial with macitentan 10 mg in US patients with PAH. Item performance, Rasch analysis, and factor analyses were used to select the final item content of the PRO and to define its domain structure. Internal consistency, test-retest reliability, known-group and construct validity, sensitivity to change, and influence of oxygen on item performance were evaluated. RESULTS: Data from 278 patients (79% female; mean age: 60 years) were analyzed. Following removal of redundant/misfitting items, the final questionnaire has 11 symptom items across two domains (cardiopulmonary and cardiovascular symptoms) and 11 impact items across two domains (physical and cognitive/emotional impacts). Differential item function analysis confirmed that PRO scoring is unaffected by oxygen use. For all four domains, internal consistency reliability was high (Cronbach's alpha > 0.80), and scores were highly reproducible in stable patients (intraclass correlation coefficient: 0.84-0.94). Correlations with the Cambridge Pulmonary Hypertension Outcome Review questionnaire and the 36-item Medical Outcomes Study Short Form Survey were moderate to high ([r] = 0.34-0.80). The questionnaire differentiated well between patients with varying disease severity levels and was sensitive to improvements in clinician- and patient-reported disease severity. CONCLUSIONS: The Pulmonary Arterial Hypertension-Symptoms and Impact Questionnaire is a brief, disease-specific PRO instrument possessing good psychometric properties that can be administered in clinical practice and clinical studies. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01841762; URL: www.clinicaltrials.gov.

Equilibrium or quenched: fundamental differences between lipid monolayers, supported bilayers, and membranes.

In this work, we establish fundamental differences between the structure and packing of lipids in monolayers, supported bilayers, and multilayer films. High resolution grazing incidence X-ray diffraction reveals that monolayer structure is largely retained upon deposition onto substrates with the area per molecule controlled by deposition pressure. Such structural changes are consistent with a quenched rather than equilibrated supported membrane structure. Supported bilayers formed by vesicle fusion exhibit structural similarity to bilayers deposited at 38 mN/m, whereas packing in lipid multilayers more closely resembled bilayers deposited below 30 mN/m. At the molecular level, coupling between opposing lipid acyl chains is observed for all deposition pressures with the outer leaflet templating on the inner leaflet. Leaflet coupling induces a small condensation in the area per lipid molecule and a surprising increase in acyl chain tilt. Moreover, supported lipid bilayers exhibit preferential acyl chain alignment: the system cannot be modeled with freely rotating acyl chains as in free-standing lipid monolayers. Such acyl chain alignment is consistent with orientational texture of lipid tilt directors at larger length scales. These findings clearly demonstrate that supported, gel-phase bilayer membrane structure can be controlled and maintained by deposition onto solid supports and that increasing surface pressure induces preferential alignment of the acyl chains both within and between membrane leaflets.

Use of X-ray diffraction, molecular simulations, and spectroscopy to determine the molecular packing in a polymer-fullerene bimolecular crystal.

The molecular packing in a polymer: fullerene bimolecular crystal is determined using X-ray diffraction (XRD), molecular mechanics (MM) and molecular dynamics (MD) simulations, 2D solid-state NMR spectroscopy, and IR absorption spectroscopy. The conformation of the electron-donating polymer is significantly disrupted by the incorporation of the electron-accepting fullerene molecules, which introduce twists and bends along the polymer backbone and 1D electron-conducting fullerene channels.

Molecular structure of interfacial human meibum films.

Meibum is the primary component of the tear film lipid layer. Thought to play a role in tear film stabilization, understanding the physical properties of meibum and how they change with disease will be valuable in identifying dry eye treatment targets. Grazing incidence X-ray diffraction and X-ray reflectivity were applied to meibum films at an air-water interface to identify molecular organization. At room temperature, interfacial meibum films formed two coexisting scattering phases with rectangular lattices and next-nearest neighbor tilts, similar to the Ov phase previously identified in fatty acids. The intensity of the diffraction peaks increased with compression, although the lattice spacing and molecular tilt angle remained constant. Reflectivity measurements at surface pressures of 18 mN/m and above revealed multilayers with d-spacings of 50 Å, suggesting that vertical organization rather than lateral was predominantly affected by meibum-film compression.

Molecular packing and solar cell performance in blends of polymers with a bisadduct fullerene.

We compare the solar cell performance of several polymers with the conventional electron acceptor phenyl-C61-butyric acid methyl ester (PCBM) to fullerenes with one to three indene adducts. We find that the multiadduct fullerenes with lower electron affinity improve the efficiency of the solar cells only when they do not intercalate between the polymer side chains. When they intercalate between the side chains, the multiadduct fullerenes substantially reduce solar cell photocurrent. We use X-ray diffraction to determine how the fullerenes are arranged within crystals of poly-(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) and suggest that poor electron transport in the molecularly mixed domains may account for the reduced solar cell performance of blends with fullerene intercalation.

Insertion mechanism of a poly(ethylene oxide)-poly(butylene oxide) block copolymer into a DPPC monolayer.

Interactions between amphiphilic block copolymers and lipids are of medical interest for applications such as drug delivery and the restoration of damaged cell membranes. A series of monodisperse poly(ethylene oxide)-poly(butylene oxide) (EOBO) block copolymers were obtained with two ratios of hydrophilic/hydrophobic block lengths. We have explored the surface activity of EOBO at a clean interface and under 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers as a simple cell membrane model. At the same subphase concentration, EOBO achieved higher equilibrium surface pressures under DPPC compared to a bare interface, and the surface activity was improved with longer poly(butylene oxide) blocks. Further investigation of the DPPC/EOBO monolayers showed that combined films exhibited similar surface rheology compared to pure DPPC at the same surface pressures. DPPC/EOBO phase separation was observed in fluorescently doped monolayers, and within the liquid-expanded liquid-condensed coexistence region for DPPC, EOBO did not drastically alter the liquid-condensed domain shapes. Grazing incidence X-ray diffraction (GIXD) and X-ray reflectivity (XRR) quantitatively confirmed that the lattice spacings and tilt of DPPC in lipid-rich regions of the monolayer were nearly equivalent to those of a pure DPPC monolayer at the same surface pressures.

Structure and thermodynamics of lipid bilayers on polyethylene glycol cushions: fact and fiction of PEG cushioned membranes.

In developing well hydrated polymer cushioned membranes, structural studies are often neglected. In this work, neutron and X-ray reflectivity studies reveal that hybrid bilayer/polyethylene glycol (PEG) systems created from mixtures of phospholipids and PEG conjugated lipopolymers do not yield a hydrated cushion beneath the bilayer unless the terminal ends of the lipopolymers are functionalized with reactive end groups and can covalently bind (tether) to the underlying support surface. While reactive PEG tethered systems yielded bilayers with near complete surface coverage, a bimodal distribution of heights with sub-micrometer lateral dimensions was observed consisting of cushioned membrane domains and uncushioned regions in close proximity to the support. The membrane fraction cushioned by the hydrated polymer could be controlled by adjusting the molar ratio of lipopolymer in the bilayer. A general phase diagram based on the free energy of the various configurations is derived that qualitatively predicts the observed behavior and the resulting structure of such systems a priori. As further evidenced by ellipsometry, atomic force and fluorescence microscopy, the tethered system provides a simple means for fabricating small cushioned domains within a membrane.

pH responsive polymer cushions for probing membrane environment interactions.

A robust and straightforward method for the preparation of lipid membranes upon dynamically responsive polymer cushions is reported. Structural characterization demonstrates that complete, well-packed membranes with tunable mobility can be constructed on the polymeric cushion. With this system, membrane conformational changes induced by cellular cytoskeleton interactions can be modeled. The membrane can be tailored to screen the cushion from changes in pH or allow rapid response to the pH environment by incorporation of protein ion channels. This elementary system offers a means to replicate the conformational changes that occur with the cellular cytoskeleton and has great potential for fundamental biophysical studies of membrane properties and membrane-protein interactions decoupled from the underlying solid support.

Tuning the properties of polymer bulk heterojunction solar cells by adjusting fullerene size to control intercalation.

We demonstrate that intercalation of fullerene derivatives between the side chains of conjugated polymers can be controlled by adjusting the fullerene size and compare the properties of intercalated and nonintercalated poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (pBTTT):fullerene blends. The intercalated blends, which exhibit optimal solar-cell performance at 1:4 polymer:fullerene by weight, have better photoluminescence quenching and lower absorption than the nonintercalated blends, which optimize at 1:1. Understanding how intercalation affects performance will enable more effective design of polymer:fullerene solar cells.

X-ray diffraction and reflectivity validation of the depletion attraction in the competitive adsorption of lung surfactant and albumin.

Lung surfactant (LS) and albumin compete for the air-water interface when both are present in solution. Equilibrium favors LS because it has a lower equilibrium surface pressure, but the smaller albumin is kinetically favored by faster diffusion. Albumin at the interface creates an energy barrier to subsequent LS adsorption that can be overcome by the depletion attraction induced by polyethylene glycol (PEG) in solution. A combination of grazing incidence x-ray diffraction (GIXD), x-ray reflectivity (XR), and pressure-area isotherms provides molecular-resolution information on the location and configuration of LS, albumin, and polymer. XR shows an average electron density similar to that of albumin at low surface pressures, whereas GIXD shows a heterogeneous interface with coexisting LS and albumin domains at higher surface pressures. Albumin induces a slightly larger lattice spacing and greater molecular tilt, similar in effect to a small decrease in the surface pressure. XR shows that adding PEG to the LS-albumin subphase restores the characteristic LS electron density profile at the interface, and confirms that PEG is depleted near the interface. GIXD shows the same LS Bragg peaks and Bragg rods as on a pristine interface, but with a more compact lattice corresponding to a small increase in the surface pressure. These results confirm that albumin adsorption creates a physical barrier that inhibits LS adsorption, and that PEG in the subphase generates a depletion attraction between the LS aggregates and the interface that enhances LS adsorption without substantially altering the structure or properties of the LS monolayer.