Ensovibep, a SARS-CoV-2 antiviral designed ankyrin repeat protein, is safe and well tolerated in healthy volunteers: Results of a first-in-human, ascending single-dose Phase 1 study.

AIMS: This study aimed to assess safety, tolerability, pharmacokinetic (PK) and pharmacodynamic (PD) effects of ensovibep, a designed ankyrin repeat protein antiviral being evaluated as a COVID-19 treatment, in healthy volunteers in a first-in-human ascending single-dose study. METHODS: Subjects were dosed intravenously, in a randomized double-blinded manner, with either ensovibep at 3, 9 or 20 mg/kg or with placebo, and followed until Day 100. PK and safety were assessed throughout the study duration. Immunogenicity and PD via viral neutralization in serum were also assessed. RESULTS: All adverse events were of mild to moderate severity, and no serious adverse events were observed. One subject who received the 20-mg/kg dose presented with moderate hypersensitivity vasculitis 3 weeks after infusion, which fully resolved using standard procedures. In most subjects ensovibep showed expected mono-exponential decline with a half-life of around 2 weeks. Anti-drug antibodies were detected in 15 of 17 subjects, with the earliest onset detected on Day 29. Viral neutralization assays on subject serum showed effective viral neutralization over the first 3 weeks following dosing with titre values in a dose dependent manner. CONCLUSION: Ensovibep proved safe in this first-in-human safety study and exhibited PK and PD parameters consistent with the expected treatment period required for acute COVID-19 infection.

Alfapump® system vs. large volume paracentesis for refractory ascites: A multicenter randomized controlled study.

BACKGROUND AND AIMS: Patients with refractory ascites (RA) require repeated large volume paracenteses (LVP), which involves frequent hospital visits and is associated with a poor quality-of-life. This study assessed safety and efficacy of an automated, low-flow pump (alfapump® [AP]) compared with LVP standard of care [SoC]. METHODS: A randomized controlled trial, in seven centers, with six month patient observation was conducted. Primary outcome was time to first LVP. Secondary outcomes included paracentesis requirement, safety, health-related quality-of-life (HRQoL), and survival. Nutrition, hemodynamics, and renal injury biomarkers were assessed in a sub-study at three months. RESULTS: Sixty patients were randomized and 58 were analyzed (27 AP, 31 SoC, mean age 61.9years, mean MELD 11.7). Eighteen patients were included in the sub-study. Compared with SoC, median time to first LVP was not reached after six months in the AP group, meaning a significant reduction in LVP requirement for the AP patients (AP, median not reached; SoC, 15.0days (HR 0.13; 95%CI 13.0-22.0; p<0.001), and AP patients also showed significantly improved Chronic Liver Disease Questionnaire (CLDQ) scores compared with SoC patients (p<0.05 between treatment arms). Improvements in nutritional parameters were observed for hand-grip strength (p=0.044) and body mass index (p<0.001) in the sub-study. Compared with SoC, more AP patients reported adverse events (AEs; 96.3% vs. 77.4%, p=0.057) and serious AEs (85.2 vs. 45.2%, p=0.002). AEs consisted predominantly of acute kidney injury in the immediate post-operative period, and re-intervention for pump related issues, and were treatable in most cases. Survival was similar in AP and SoC. CONCLUSIONS: The AP system is effective for reducing the need for paracentesis and improving quality of life in cirrhotic patients with RA. Although the frequency of SAEs (and by inference hospitalizations) was significantly higher in the AP group, they were generally limited and did not impact survival. Lay summary: The alfapump® moves abdominal fluid into the bladder from where it is then removed by urination. Compared with standard treatment, the alfapump reduces the need for large volume paracentesis (manual fluid removal by needle) in patients with medically untreatable ascites. This can improve life quality for these patients. www.clinicaltrials.gov#NCT01528410.

A combined NMR and computational approach to investigate peptide binding to a designed Armadillo repeat protein.

The specific recognition of peptide sequences by proteins plays an important role both in biology and in diagnostic applications. Here we characterize the relatively weak binding of the peptide neurotensin (NT) to the previously developed Armadillo repeat protein VG_328 by a multidisciplinary approach based on solution NMR spectroscopy, mutational studies, and molecular dynamics (MD) simulations, totaling 20µs for all MD runs. We describe assignment challenges arising from the repetitive nature of the protein sequence, and we present novel approaches to address them. Partial assignments obtained for VG_328 in combination with chemical shift perturbations allowed us to identify the repeats not involved in binding. Their subsequent elimination resulted in a reduced-size binder with very similar affinity for NT, for which near-complete backbone assignments were achieved. A binding mode suggested by automatic docking and further validated by explicit solvent MD simulations is consistent with paramagnetic relaxation enhancement data collected using spin-labeled NT. Favorable intermolecular interactions are observed in the MD simulations for the residues that were previously shown to contribute to binding in an Ala scan of NT. We further characterized the role of residues within the N-cap for protein stability and peptide binding. Our multidisciplinary approach demonstrates that an initial low-resolution picture for a low-micromolar-peptide binder can be refined through the combination of NMR, protein design, docking, and MD simulations to establish its binding mode, even in the absence of crystallographic data, thereby providing valuable information for further design.

Spontaneous self-assembly of engineered armadillo repeat protein fragments into a folded structure.

Repeat proteins are built of modules, each of which constitutes a structural motif. We have investigated whether fragments of a designed consensus armadillo repeat protein (ArmRP) recognize each other. We examined a split ArmRP consisting of an N-capping repeat (denoted Y), three internal repeats (M), and a C-capping repeat (A). We demonstrate that the C-terminal MA fragment adopts a fold similar to the corresponding part of the entire protein. In contrast, the N-terminal YM2 fragment constitutes a molten globule. The two fragments form a 1:1 YM2:MA complex with a nanomolar dissociation constant essentially identical to the crystal structure of the continuous YM3A protein. Molecular dynamics simulations show that the complex is structurally stable over a 1 µs timescale and reveal the importance of hydrophobic contacts across the interface. We propose that the existence of a stable complex recapitulates possible intermediates in the early evolution of these repeat proteins.

Insights into RNA unwinding and ATP hydrolysis by the flavivirus NS3 protein.

Together with the NS5 polymerase, the NS3 helicase has a pivotal function in flavivirus RNA replication and constitutes an important drug target. We captured the dengue virus NS3 helicase at several stages along the catalytic pathway including bound to single-stranded (ss) RNA, to an ATP analogue, to a transition-state analogue and to ATP hydrolysis products. RNA recognition appears largely sequence independent in a way remarkably similar to eukaryotic DEAD box proteins Vasa and eIF4AIII. On ssRNA binding, the NS3 enzyme switches to a catalytic-competent state imparted by an inward movement of the P-loop, interdomain closure and a change in the divalent metal coordination shell, providing a structural basis for RNA-stimulated ATP hydrolysis. These structures demonstrate for the first time large quaternary changes in the flaviviridae helicase, identify the catalytic water molecule and point to a beta-hairpin that protrudes from subdomain 2, as a critical element for dsRNA unwinding. They also suggest how NS3 could exert an effect as an RNA-anchoring device and thus participate both in flavivirus RNA replication and assembly.

Three-dimensional structure and ligand binding properties of trichosurin, a metatherian lipocalin from the milk whey of the common brushtail possum Trichosurus vulpecula.

Lipocalins are extracellular proteins (17-25 kDa) that bind and transport small lipophilic molecules. The three-dimensional structure of the first lipocalin from a metatherian has been determined at different values of pH both with and without bound ligands. Trichosurin, a protein from the milk whey of the common brushtail possum, Trichosurus vulpecula, has been recombinantly expressed in Escherichia coli, refolded from inclusion bodies, purified and crystallized at two different pH values. The three-dimensional structure of trichosurin was solved by X-ray crystallography in two different crystal forms to 1.9 A (1 A=0.1 nm) and 2.6 A resolution, from crystals grown at low and high pH values respectively. Trichosurin has the typical lipocalin fold, an eight-stranded anti-parallel beta-barrel but dimerizes in an orientation that has not been seen previously. The putative binding pocket in the centre of the beta-barrel is well-defined in both high and low pH structures and is occupied by water molecules along with isopropanol molecules from the crystallization medium. Trichosurin was also co-crystallized with a number of small molecule ligands and structures were determined with 2-naphthol and 4-ethylphenol bound in the centre of the beta-barrel. The binding of phenolic compounds by trichosurin provides clues to the function of this important marsupial milk protein, which is highly conserved across metatherians.