Structural basis for cannabinoid-induced potentiation of alpha1-glycine receptors in lipid nanodiscs

Nociception and motor coordination are critically governed by glycine receptor (GlyR) function at inhibitory synapses. Consequentially, GlyRs are attractive targets in the management of chronic pain and in the treatment of several neurological disorders. High-resolution mechanistic details of GlyR function and its modulation are just emerging. While it has been known that cannabinoids such as Δ9-tetrahydrocannabinol (THC), the principal psychoactive constituent in marijuana, potentiate GlyR in the therapeutically relevant concentration range, the molecular mechanism underlying this effect is still not understood. Here, we present Cryo-EM structures of full-length GlyR reconstituted into lipid nanodisc in complex with THC under varying concentrations of glycine. The GlyR-THC complexes are captured in multiple conformational states that reveal the basis for THC-mediated potentiation, manifested as different extents of opening at the level of the channel pore. Taken together, these structural findings, combined with molecular dynamics simulations and functional analysis, provide insights into the potential THC binding site and the allosteric coupling to the channel pore.

Effect of a 2-step probiotic program on digestive health and performance of Holstein heifer calves

Managing the composition of the bacterial communities in the digestive tract with the use of probiotics that enhance protective microflora could result in positive effects on health and performance of calves. The objective of this study was to evaluate a 2-step probiotic program (added to colostrum and milk) on the digestive health and growth of preweaning Holstein heifers. A randomized clinical trial was conducted from July to October 2020 in a calf rearing facility in Colorado. Calves were housed in pairs sharing the same treatment in 2 polyethylene hutches within a common area of 4.50 m². A total of 232 calves were enrolled at birth and randomly allocated into 2 treatment groups [control (CTR) = 116; treatment (PB) = 116] and followed until weaning (64 ± 3 d). Treatment consisted of 2 formulations of a multistrain bacterial-based probiotic added in colostrum (PBF1) and milk (PBF2). Treatment calves received 2 g of PBF1 added to each colostrum feeding, and 1 g of PBF2 added to the milk at the morning feeding 3 times per week up to weaning. Calf weight was collected at birth, at 30 d of age, and at weaning. Serum total protein was determined at age 3 ± 1 d and a health assessment was completed 3 times per week. Statistical analyses were performed using SAS, with calf considered the experimental unit clustered by housing pair. Cox proportional hazard analysis and time to event analysis were used to compare time to the first diarrhea event and time to recovery between treatment groups. The total number of diarrhea events and culling were assessed by Poisson regression and logistic regression analysis, respectively. Linear regression was performed to evaluate differences in average daily gain by treatment group. Overall, the mean (± standard error) temperature humidity index (THI) was 75 (± 0.44) units during the study period, which resulted in continuous exposure to heat stress in the day hours. No difference between treatment groups was observed in serum total protein. The overall incidence of diarrhea was 96.6% (CTR = 99%, PB = 95%); no differences were determined in the hazard of a first diarrhea episode or in the median time to the first diarrhea event (11 d in both groups). Similarly, no differences were found in the likelihood of recovery or in the median time to recovery from diarrhea (7 d in both groups). Likewise, treatment group was not associated with the number of diarrhea events, mean (± standard error, g/d) average daily gain from birth to weaning [CTR = 562.5 (13.9); PB = 570.8 (13.5)], or with the odds of culling. The most prevalent pathogen isolated from feces was Clostridium, which tended to be more frequent in CTR calves than PB calves. In conclusion, the probiotic program did not affect the incidence of enteric disease or the growth of preweaning heifer calves.

A phase II study of retifanlimab (INCMGA00012) in patients with squamous carcinoma of the anal canal who have progressed following platinum-based chemotherapy (POD1UM-202)

Background

Locally advanced or metastatic squamous carcinoma of the anal canal (SCAC) has poor prognosis following platinum-based chemotherapy. Retifanlimab (INCMGA00012), a humanized monoclonal antibody targeting programmed death protein-1 (PD-1), demonstrated clinical activity across a range of solid tumors in clinical trials. We present results from POD1UM-202 (NCT03597295), an open-label, single-arm, multicenter, phase II study evaluating retifanlimab in patients with previously treated advanced or metastatic SCAC.

Patients and methods

Patients ≥18 years of age had measurable disease and had progressed following, or were ineligible for, platinum-based therapy. Retifanlimab 500 mg was administered intravenously every 4 weeks. The primary endpoint was overall response rate (ORR) by independent central review. Secondary endpoints were duration of response (DOR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety.

Results

Overall, 94 patients were enrolled. At a median follow-up of 7.1 months (range, 0.9-19.4 months), ORR was 13.8% [95% confidence interval (CI) 7.6% to 22.5%], with one complete response (1.1%) and 12 partial responses (12.8%). Responses were observed regardless of human immunodeficiency virus or human papillomavirus status, programmed death ligand 1 (PD-L1) expression, or liver metastases. Stable disease was observed in 33 patients (35.1%) for a DCR of 48.9% (95% CI 38.5% to 59.5%). Median DOR was 9.5 months (range, 5.6 months-not estimable). Median (95% CI) PFS and OS were 2.3 (1.9-3.6) and 10.1 (7.9-not estimable) months, respectively. Retifanlimab safety in this population was consistent with previous experience for the PD-(L)1 inhibitor class.

Conclusions

Retifanlimab demonstrated clinically meaningful and durable antitumor activity, and an acceptable safety profile in patients with previously treated locally advanced or metastatic SCAC who have progressed on or are intolerant to platinum-based chemotherapy.

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Retifanlimab (PD-1 inhibitor) monotherapy demonstrated encouraging results in patients with platinum-refractory SCAC.

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Clinically meaningful antitumor activity was reported with ORR of 13.8% and stable disease in 35.1%, for a DCR of 48.9%.

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Observed responses in advanced SCAC were durable (median 9.5 months).

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Acceptable safety profile consistent with that reported for the PD-(L)1 inhibitor class.

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Promising results warrant further investigation of retifanlimab in advanced SCAC as well as earlier stages of disease.

CT volumetry helps predict prognosis of large hepatocellular carcinoma after resection

AIM

To determine whether the tumour volume measurement on preoperative contrast-enhanced computed tomography (CT) could be used to predict the overall survival patients with large hepatocellular carcinoma (>5 cm) after resection.

MATERIALS AND METHODS

This study included 171 patients with surgically confirmed hepatocellular carcinoma who underwent preoperative CT. The largest diameter, the product of the axial dimension, tumour volume, and tumour-to-liver volume ratio (TTLVR) on CT images were measured and calculated. The univariate and multivariate Cox proportional hazard ratio regression models were used to identify the impact of the tumour burden-related risk factors on overall survival.

RESULTS

In multivariate analysis, TTLVR (p=0.042) and major vascular invasion (p=0.006) were independently associated with overall survival of patients with hepatocellular carcinoma after the resection. The group in which the patients had a low TTLVR showed higher cumulative survival rates than patients with a TTLVR (p=0.004). Patients with a low TTLVR (≤26.23%) and absence of major vascular invasion had significantly higher cumulative survival rates compared to those patients with hepatocellular carcinoma with either or both the risk factors (p=0.001).

CONCLUSION

A higher TTLVR in combination with the presence of major vascular invasion was associated with poorer overall survival in patients with large hepatocellular carcinoma after resection.

OUTCOMES OF NEONATAL CHYLOUS EFFUSIONS: A 20-YEAR WEST-AUSTRALIAN TERTIARY CENTER EXPERIENCE

Neonatal chylous effusions are rare entity with limited evidence-based management. We conducted a retrospective review of neonates admitted to King Edward Memorial and Princess Margaret/Perth Children's Hospital over 20 years with laboratory-confirmed chylous effusions. A total of 51 infants with chylous effusion were identified. Median gestational age and birth weight were 35.5 weeks and 2620 grams respectively. Congenital [27/51] and acquired [24/51] cases were included. Antenatal interventions were performed in 17/22 with antenatal hydrops and 50/51 needed postnatal drains. Effusions were monitored with serial (≥2) chest ultrasounds in 29/51 infants and multiple (≥5) x-rays in 45/51 infants. Median duration of mechanical ventilation, oxygen requirement, and hospital stay was 294.5 hours, 400 hours, and 49 days respectively. 39/51 received medium chain triglyceride (MCT) diet while 8/51 received octreotide. Six infants died during hospital stay. 12/19 had normal developmental assessment at one-year. The acquired group had higher number of xrays done, need for MCT diet and inotropes, and hospital stay vs congenital group. Duration of drains, radiological investigations and immunoglobulin administration were higher in neonates who received octreotide. Syndromic association, duration of ventilation and oxygenation were risk factors for mortality. In our setting, neonatal chylous effusions are associated with significant morbidity and mortality.

Sub-structure-based category formation for the prioritisation of genotoxicity hazard assessment for pesticide residues: Sulphonyl ureas

In dietary risk assessment, residues of pesticidal ingredients or their metabolites need to be evaluated for their genotoxic potential. The European Food Safety Authority recommend a tiered approach focussing assessment and testing on classes of similar chemicals. To characterise similarity and to identify structural alerts associated with genotoxic concern, a set of chemical sub-structures was derived for an example dataset of 74 sulphonyl urea agrochemicals for which either Ames, chromosomal aberration or micronucleus test results are publicly available. This analysis resulted in a set of seven structural alerts that define the chemical space, in terms of the common parent and metabolic scaffolds, associated with the sulphonyl urea chemical class. An analysis of the available profiling schemes for DNA and protein reactivity shows the importance of investigating the predictivity of such schemes within a well-defined area of structural space. Structural space alerts, covalent chemistry profiling and physico-chemistry properties were combined to develop chemical categories suitable for chemical prioritisation. The method is a robust and reproducible approach to such read-across predictions, with the potential to reduce unnecessary testing. The key challenge in the approach was identified as being the need for pesticide-class specific metabolism data as the basis for structural space alert development.

Water Nanoconfined in a Hydrophobic Pore: Molecular Dynamics Simulations of Transmembrane Protein 175 and the Influence of Water Models

Water molecules within biological ion channels are in a nanoconfined environment and therefore exhibit behaviors which differ from that of bulk water. Here, we investigate the phenomenon of hydrophobic gating, the process by which a nanopore may spontaneously dewet to form a "vapor lock" if the pore is sufficiently hydrophobic and/or narrow. This occurs without steric occlusion of the pore. Using molecular dynamics simulations with both rigid fixed-charge and polarizable (AMOEBA) force fields, we investigate this wetting/dewetting behavior in the transmembrane protein 175 ion channel. We examine how a range of rigid fixed-charge and polarizable water models affect wetting/dewetting in both the wild-type structure and in mutants chosen to cover a range of nanopore radii and pore-lining hydrophobicities. Crucially, we find that the rigid fixed-charge water models lead to similar wetting/dewetting behaviors, but that the polarizable water model resulted in an increased wettability of the hydrophobic gating region of the pore. This has significant implications for molecular simulations of nanoconfined water, as it implies that polarizability may need to be included if we are to gain detailed mechanistic insights into wetting/dewetting processes. These findings are of importance for the design of functionalized biomimetic nanopores (e.g., sensing or desalination) as well as for furthering our understanding of the mechanistic processes underlying biological ion channel function.

The prevalence and safety of direct oral anticoagulants in patients with non-atrial fibrillation associated intra-cardiac thrombus

Background

The standard of care in management of intra-cardiac thrombus has been the use of vitamin K antagonists (VKAs). The emergence and use of direct oral anticoagulants (DOACs) in other conditions has led to the consideration of their use in patients with intra-cardiac thrombus. Thus far, case-reports have provided the majority of data regarding the efficacy of DOACs in this population.

Purpose

The aim of this observational study was to investigate the safety and efficacy of DOACs in intracardiac thrombus not associated with atrial fibrillation, compared to the current standard of care, VKAs.

Methods

An observational study was conducted between 10 hospitals in our region. The study was conducted between 2013 and 2019 in patients with a diagnosis of intracardiac thrombus. All left and right, atrial and ventricular thrombi were included. Patients with atrial fibrillation were excluded. Patient information was collected from the hospital electronic record. The primary endpoints were clinically significant bleeding requiring transfusion and thromboembolic events, excluding myocardial infarction.

Results

1153 patients had a diagnosis of intracardiac thrombus. 878 out of 1153 patients were discharged on warfarin and 275 were discharged on a DOAC. In the warfarin population 73 of 878 patients (8.3%) had clinically significant bleeding events compared to 21 of 275 patients (7.6%) in the DOAC population (p=0.801). The median ages were 60.5 and 58 respectively. The median time period to a bleeding event was 151 and 198 days respectively. In the warfarin population, 116 of 878 patients (13.2%) had thromboembolic disease versus 34 of 275 patients (12.4%) in the DOAC arm (p=0.759). The median ages were 62 and 62.5 respectively. The median time period to a thromboembolic event was 114 and 184 days respectively. In the warfarin arm, 3 patients had systemic thromboembolism and 113 patients had embolic strokes. In the DOAC arm, 2 patients had systemic thromboembolism, 32 patients had embolic strokes.

Conclusion

The data from this study suggests that DOACs may be a feasible alternative to warfarin in patients with intracardiac thrombus. There was no statistically significant difference in the rates of clinically significant bleeding or in incidence of thromboembolic disease. To our knowledge, this is the largest observational study to date on this topic. Randomized controlled trials are needed to fully establish the efficacy of DOACs in this patient population.

Funding Acknowledgement

Type of funding sources: None. Table 1